A STUDY 0? LOW COST
REFRIGERATKON EQUIPMENT FOR
(ZOOLING CREAM

Thesis ‘50: the Degree 31 M. &
MiCHIGAN STATE COLLEGE

Fred Eugene Satchel!
[947

M-796

This is to certifg that the

thesis entitled .

"A STUDY 0? Low COST MLFRIGEMEIQJ EQUIPMLJT
FOR COOLING CREAM"

presented by

has been accepted towards fulfillment

of the requirements for

M. S_.___ degree infligaljgral Engineering

)

/7—'/
[/1 ” K
/ " ‘\ l ‘
/ - V 0

Major professor

 

A STUDY OF LOW COST REFRIGERATION
EQUIPMENT FOR COOLING CREAM

By

Fred Eugene Satchell

A THESIS

Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and Applied Science

in partial fulfillment of the requirements
for the degree of

)

MASTER OF SCIENCE

Department of Agricultural Engineering

1947

. ‘L—

 

 

 

TABLE OF CONTENTS

Page
Acknowledgements o o e o o o o o o o o o o o e o o o o 2

Purpose Of PrOblem o e o e e o o o o o o o o o o o e 0
History and Deve10pment of the Butter Industry . . . .

Background for the Project . . . . . . . . . . . . . o

CD (D $5 tF

The Quality Problem . . . . . . . . . o . . . . . . .
Relative Importance of Cleanliness and Cooling 0 o . . ll
Economical Feasibility of a Cream Cooler . . . . . . . 19
Design of Cooler . . . . . . . . . . . . . . . . . . . 22
Putting Unit in Operation . . . . . . . . . . . . . . 39
Testing Programt ... . . . . . . o o . . p . . o o o o 40
Effect of Holding Cream at Low Temperature . . . . o . 52
Performance Under Farm Conditions . . . . . . . . . . 62
Discussion 0 . . o . . . . . . . . . . . e .'. . . . 68
Conclusion . . . . . . . . . . . . . . . . . . . . . 70

Literature Cited 0 o o o o e o o o e o o e o o o o o 71

ACKNOWLDEGEMENT

The author gratefully acknowledges the helpful
suggestions and valuable assistance of Professor A. W.
Farrell and Professor D. E. Wiant or the Department of
Agricultural Engineering and Assistant Professor J. M.
Jensen of the Dairy Department of Michigan State College.

Funds for the project were made available by

Swift and Company.

A STUDY OF LOW COST REFRIGERATION
EQUIPMENT FOR COOLING CREAM

PURPOSE OF PROBLEM

It is generally recognized that in the postwar
period, considerable pressure will be brought on the
butter industry to improve the quality of their product.
Federal and State laws may require such improvement or

it may be forced by consumer pressure.

One of the most effective ways of maintaining
the high quality of farm held cream is by the use of low
temperatures. This problem has been set up to design,
build and test one or more basic designs for a low cost
mechanical refrigerator which.will prevent cream deteriora-

tion and thus make better butter possible.

HISTORY AND DEVELOPMENT OF THE BUTTER INDUSTRY 9

Butter has been used for various purposes includ!
ing food, medicinal and cosmetic purposes since before
the beginning of the Christian Era. Martiny, a German
dairy scientist, records the making and use of butter in
2000 A.D. For centuries the oream.for this butter was
separated by gravity. To be effective, gravity separation
must take place on cream that has not lost the physical

prOperties characteristic of sweet cream. Thus, since

effective separation requires from 24 to 48 hours, this
method is successful only when the temperature of the

cream could be held low enough to prevent curdling in this
length of time.

In.the infancy of butter as a food, there seems
to have been develOped a taste for rancidity, probably
from necessity. Butter was even.buried and left for long
periods of time. One practice was to bury the butter and
then plant a tree over it to insure against its being
disturbed. The Irish.buried butter in the peat bogs of
that country. Specimans have been recently discovered
that are believed to be over eight hundred years old.

Until the middle of the 19th century the factory
system of butter manufacture was practically unknown. The
butter was nearly all made during the summer months on
the farm. Refrigeration, pasturization and other present
day quality control methods were unknown at that time and
the market butter was of inferior quality. By the end of
the flush season the butter was of such poor quality that
it was not marketable as such. It was generally disposed

of as packing stock.

Efforts to renovate packing stock butter were
first successful in 1885. In this process the butter is
melted, clarified and refined. This oil is mixed with

skim.milk, milk or cream and regranulated. About 50,000,000

[I

x.

pounds per year of this butter were sold during the first
decade of the 19th century.

Records indicate that Manchester, Iowa started
the first butter factory in 1871. This first factory
gathered whole milk and skimmed the cream in the factory,
however, the practice of gathering cream and processing

in a central plant became pOpular at nearly the same time.

In 1879, Dr. Gustav Patrick DeLavel, introduced
his continuous cream.aeparator in Sweden. Factories in
this country changed to his separator in the years from ,
1885 to 1890 and farm separation practically disappeared.
During this period creameries bought whole milk and sepa-
rated it at the creamery. This practice yielded a much
better quality of cream.than was obtained under the old
system. Consumption increased rapidly and the butter

industry flourished.

The farm separator was introduced in the last
decade of the 19th century. Its acceptance was slow at
first but was firmly established by 1920 and by 1930 was
adapted on practically every farm in the dairy regions of

this country.

The creameries again adopted the gathered cream
system and the responsibility for cream quality was shifted

again to the farm. While the farm separator undoubtedly

has helped to spread the dairy industry and thus increased
the volume of dairy products, it has resulted in much of
the cream being received in an advanced stage of deteriora-
tion. This has in turn.had an adverse effect on the
quality of American butter. Keen competition for cream
volume has also aggravated the quality program. Efforts
toward cream quality improvement have been nullified in
many sections by the refusal of creameries to pay a premium

for high quality cream.

There has resulted from this situation of poor
butter quality two definite trends, one is directed toward
the return to the gathered milk system with.better utiliza-
tion of the non-fat milk solids to pay the added trans-
portation cost. There has been a great ambunt of research
on better processing methods and market deve10pment for

these products.

The second approach is to provide the farmer with
'inexpensive facilities to maintain the quality of the
cream until delivered to the factory. This approach should
appeal particularily to the farmer who desires the skim
milk for stock feed or other home use. Perhaps it could
not be Justified unless there was a good use present for
the skim milk, or unless the farmer was far removed from

a market.

BACKGROUND FOR THE PROJECT

The butter industry has two main purposes in
the American economy. The first purpose is the obvious
one of providing income to thousands of farmers. These
farmers are usually small producers or are isolated from

a fluid milk market.

The second purpose is less apparent but not less
important. The butter industry acts as a balance wheel in
the fluid milk industry. There have always been periods
of slack and heavy production of dairy products. Usually
the farmer takes advantage of the lush spring feed supply
to produce the heaviest flow of milk. Conversely, in mid-
winter milk production falls off markedly. Therefore, if
the fluid milk supply is to be adequate in this slack winter
period, some profitable means of using the surplus spring
and early summer flow must be provided. The dairy industry
has traditionally used this summer surplus to produce

butter.
THE QUALITY PROBLEM

The quality of the cream and butter produced
from this surplus milk is good because the milk is gathered
every day and separated in the collecting station or
processing plant. However, the consumer also uses butter

made from cream.produced by the small or isolated dairyman

I.

and here the cream.quality program needs prompt and serious
action. Much of this cream.is a week or more old and has
already suffered severe deterioration by virtue of high
temperature storage or neglect of preper cleanliness

procedures.

The quality of the butter made from this cream
is necessarily very poor in spite of the excellent work in
pasteurization and neutralization of sour cream preparatory
to butter making. In view of the widespread introduction
of vegetable fat substitutes during World War II, it seems
very necessary to establish high standards of butter quality
to meet this competition and maintain the consumer market
necessary to both functions of the butter industry. The
loss of the consumer market for butter would be a tremendous
blow to the entire dairy industry. Butter men are becoming
increasingly conscious of the adverse effect on consumer
goodwill that this poor butter is producing. They are
ready to back any sound program that will improve the
quality of cream received. The industry technology makes
good butter a simple attainment if the cream.aupply is
of reasonable good quality.

Current Approaches to Quality Control

There are two basic approaches to the problem of
maintaining the quality of farm.held cream. One method
would be the use of preservatives to inhibit bacterial

,.

 

10

and enzyme activity. The use of common salt for this pur—

pose was patented by Williams (U.S. Patent No. 2,192,864)

and made available as a public service patent.19 This

method was shown to be effective by several investigators3s5:11:17
but has never been approved by the Pure Food and Drug
Administration.

It was found that butter could be held for one
week at room temperature with no appreciable deterioration
in quality if about 10% of salt was added. Butter from
this cream in no instance contained over 2.5% of salt and
scored from 2 to 5 points higher than unsalted cream.held
under the same temperature conditions.6 It would be dif-
ficult to standardize the salt content of butter made from
salted cream.aince the salt present could only be estimated
without a chemical determination. Also salt is corrosive
to all common dairy metals except stainless steel which

would be a definite deterrent to its widespread use.

Hydrogen peroxide has also been shown to be an
effective bacteriacide and has been used to preserve dairy
products particularily in Italy. The advisability of
recommending the use of chemical perservatives by inexp
perienced farmers is Open to many criticisms and has not

received official encouragement.

The second and perhaps the best procedure, based

on present knowledge, would be to maintain the cream at a

11

low temperature to inhibit bacteria growth. Golding and
miller 8 found that mold in cream grew most rapidly at
77.5 degrees to 86 degrees F% While growth will occur at
lower and higher temperatures, the rate of growth at
temperatures approdaching the freezing point of water is
very slow.2 The work of many investigators shows a rapid
increase in bacteria growth rate when the temperature is
raised from 45 degrees to 50 degrees £5 (Fig.1?A The rate
does not change markedly at temperatures lower than about
48 degrees. Therefore there would seem to be no advantage
in maintaining lower temperatures. In fact raw sweet cream
characteristically develOps a bitter metallic flavor when

held at temperatures below 40 degrees F.15
RELATIVE IMPORTANCE OF CLEANLINESS AND COOLING

It has been shown conclusively that the tempera-
ture of cream storage is the most important single factor
in cream quality and therefore, in.butter quality. All
cream.possesses some initial contamination. Milk, freshly
drawn into sterile containers will usually show bacteria
counts in the thousands. These bacteria multiply very

rapidly at temperatures above 50 degrees Ft

In an experiment conducted at Pennsylvania State
College, 1 milk was plated and the bacteria counted directly
after drawing from.the cow and after "sooling" 12 hours.

These tests were made on a farm and the milk temperature

ioz .mE

a. umafiemmasm...

 

'l‘l

I. .«c emu W or» t

 

#—

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3555;:
pzummta 2.3: cm 2.
4.5.53 so 1.525
E: 02.26% .145

U

 

 

 

NT

9
s .b
0..

.7

 

use Vltj-BiOVB

'c’o‘.

‘.
‘

coo:

13

after cooling was still relatively warm - 60 to 68 degrees.
under these conditions percentage increases of up to

762,400 percent were noted.

In a study by J. M. Jensen and A. L. Bortee at
Michigan State College, 10 the effect of separator clean-
liness and storage temperature was studied. Three storage
temperatures were used, 55, 65, and 75 degrees F5 Three
samples were stored at each temperature making a total of
nine samples. At each temperature, samples were stored
which had been separated from (a) a carefully washed and
sterilized separator bowl, (b) a dirty separator bowl
stored at 55 degrees F3 and, (c) a dirty bowl stored at
75 degrees F5 The results of this test are shown in
Figure 2. The overwhelming effect of temperature of
storage is very apparent. Figure 5 shows work done by
different investigators but also illustrates the effect
of storage temperature and its relative importance compared

to‘cleanliness.

It may be concluded that the three essential
factors in the maintaining of cream.quality are time of
holding, temperature of storage, and good cleanliness
habits. In this study, the element of temperature is
given heavy stress. It appears that temperature control
can minimize but not eliminate the evils of long holding

and heavy contamination.

m .oz .wflm

pm. we «m1: 3 - om. cm 2. cc em

monk

.uenh Pd OUCOPQ

4’0. >h¢.a .II I
.k can h‘ OUKOPG

430. fish—a lllt

are. 23.3
”ozuous

 

.mmDOI a MZTP 02.040:

 

i

    

.uonw

 

 

 

Aummhcom oz< zumzm...

IkBOmm <_mm.—.0<m zo
mJBOm makdmdmmm ourm<32=
024 z<mJo ..._O bouumw

ON. mm Nb ow VN

Kenn

 

0'.

0’.

no.

on.

GO.

 

AilOIOV 9'.

00.

BACTERIA PER CO.

”(10’

uxuo‘

nxno’

IXIO

l00.000

I0,000

I,OOO

0.8. DJ. I UL. 042

 

 

//
//
V /
/ /
CLEAN
DIRTY / / / MILK
“if.“ / 70'F 4/
/’
// /
/ SO’F
/
/ / l /

 

 

m /

 

 

 

 

 

 

 

 

 

 

/
/
/ /
/ ' .
/ /
/J/
/
40°F /
It 24 80 ‘8 7!:

STORAGE TIH E " HOURS

F18. NO. 5

16
Method of Cooling

Caulfield and Martin 5~ studied five methods of
cooling cream.which have practical significance. (Fig. 4)
These five methods included submerging the can in cold
water, flooding or allowing a heavy flow of water over the
cans, evaporation of water from wetted cloth wraps, water
spray and storing in a refrigerator. Not included but
certainly worthy of note is mechanical refrigeration of
thveater bath. This would, in fact, be faster and more
effective than the previous five. However, the five
methods studied cooled in order of decreasing rapidity,
submerged, flooded, refrigerator, water spray and
evaporation. All except refrigeration are dependent on
local conditions such as water temperature, humidity and

air temperature.

The two most common methods used in the collect-
ing stations were evaporation and water spray. The use of
evaporative cooling is intrinsically slow and under
conditions of greater than 60% relative humidity this
method is ineffective. During the test, temperatures
obtained varied with.the room temperature and the
humidity. Room temperatures ranged from.105.5 degrees to
72 degrees. Corresponding temperatures obtained in the
cream.were 82 degrees to 84 degrees for 105.5 degrees roam

and 57 degrees to 64 degrees for 72 degrees room with.the

‘V

TEMPERATURE - ’F.

METHOD OF COOLING USED

' SUBMERGED

---- 3 FLOODEO
,,,,____ , EVAPORAT'O" SWEET CREAM ' TEMP. 98.- .
HUN. 37 '/e
SOUR CREAM" TEMP. 92 - 5| ‘L
—""'"""' 8 WATER SPRAY GT’OB’F

H

I REFRIGERATOR 35‘40’F

SWEET CREAM

 

SOUR CREAM

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

WT ‘
as ‘
so
.ee \ \
\
'0 Xx \\
\ _ l“‘wr—-.
15 6 a
70 , T‘ a “A ,
66
I
so P
tar-'- \pr—J Af-
rw’w’n r‘
on « ‘
o I 2 3 o

 

 

 

 

 

 

 

. 2 3 4 5 6
IN HOURS

csuLnsLo s ssms
4.0M" sctssss

F18. N00 4

‘18

variation at a definite room temperature due to variation

in humidity conditions. Bacteria would grow rapidly even

at the lowest of these temperatures. Spraying is also

only effective if the water and room temperatures are low.
One must conclude that the only dependable method of obtain;'
ing and maintaining consistently low temperatures is by the
use of mechanical refrigeration either in a dry box or to

lower the temperature of the cooling water used.
Choice of Dry Cooler for Temperature Control

The use of a water bath adds two outstanding
difficulties to the problem. First the box must be con-
structed more substantially to support the added weight
and to eliminate danger of leaks from dents, sprung seams
and corrosion. Second, the cream producers add cream in
small quantities. It would be a nuisance to keep the
cream container upright under the bouyant effect of the
water. Another factor which would depend on the individual
is the danger of the water becoming foul and imparting

flavors to the cream.

A small one can milk cooler was deve10ped by the
Wilson Cabinet Company, Smyrna, Delaware at the request of
T.V.A. Tests made by J. E. Nicholas, 12 Pennsylvania State
College, indicated that this cooler could handle satis-
factorily as much as two ten gallon cans of milk in twenty-

four hours. The cans would be cooled one at a time with

19

about a twelve hour interval. In the state of Pennsylvania
a survey showed that nearly fifty percent of the milk
producers could have gotten along with this inexpensive
cooler. Demand among milk producers was poor, however,

and this line has been discontinued.

In view of these facts, it was decided that this
investigation should try to develop and prove the effect-
iveness of one or more simple basic designs of mechanically
cooled dry boxes that could maintain cold temperaturesyet

be reasonable in cost.
ECONOMICAL FEASIBILITY OF'A CREAM COOLER

The introduction of a cream cooler as a neces-
sary item of equipment for the cream producer may be very
easily Justified in the eyes of the researcher on quality
improvement and aesthetic grounds alone. However, it will
certainly never gain widespread acceptance by the cream

producer unless it is possible to show a dollar benefit.

Obviously then, a farmer must receive a premium
for producing sweet cream.if he is to be converted. As
long as the farmer receives the same pay check for sour
deteriorated cream.as for fine quality cream, he will
never go to the added expense of installing cooling
equipment. We believe in the premium system and had to
assume its ultimate acceptance to justify this project.

It

 

20

How much premdum.should the farmer get? Our.
aLm was to design a cooler to sell for one hundred dollars.
Under present conditions of inflated prices, a quality
cooler cannot be produced for this sum.if handled through
the customary retail channels. However, we were able to
get an estimate of manufacturing cost of approximately
ninety-five dollars for one unit and one hundred and ten
dollars for another of slightly different design. There-
fore if the butter industry shows enough interest to
handle the cooler on a non-profit basis as milk cans have

been handled, our aim can be realized.

Assuming a capital cost of one hundred dollars
with an estimated life of 15 years, we arrive at these

cost figures:
1. Depreciation and Maintenance

at 10% $10.00 per year
2. Average Interest Cost
at 6% 5.50 per year
5. Cost of Operation 1/2 kw
per day at 2¢ 5.65 per year
TOtal $16.95

Operational cost data were taken from the average
of several cooling runs with a cream load of from 16 to
25 pounds per day. This would correspond to about 45

pounds of fat per week.

Reference to Figure 5 would immediately tell how

much premium.a farmer should receive to finance the cooler.

mmmmmmm
xmu? cun— .mm.._ oooooooooooooooooooo
mmmmmmm

 

 

\
N...
\\\\\g

 

 

\\\\ M

 

 

\ \
\,\\\\

 

\ \\ \ \

 

 

 

 

 

 

 

 

 

 

 

 

 

22

For example, a farmer producing over 52 pounds of fat a
week could justify a cooler with.a l¢ premium.While the
producer of only 8 pounds per week would have to receive
a premium.of 4% per pound. The 52 pound producer on the
other hand would show a net profit of nearly $50.00 every
year with the 4¢ premium. These figures show that even
a small premdum.would finance the cooler except for the

very small producer.
DESIGN OF COOLER

It was decided that two fundamentally different
cabinet types would be designed and built. The "R“, or
round unit would be designed primarily to handle cream.
Most farmers would find that there was sufficient space
for some storage of other foodstuffs in this unit.

Another unit "8", would be designed to handle

cream plus substantial storage space for eggs foodstuff.
Tentative Requirements for Experimental Unit

1. Should maintain a cabinet temperature of
not higher than 45 degrees Ft at an
ambient of 100 degrees F5

2. A11 controls automatic.

C):
0

Capacity:
"B" one ten gallon can or four

five gallon "shot" cans. (A "shot" can is

23

a straight sided five gallon can 9% inches
in diameter and 21 inches high).
4. Compressor should have a load capacity suf-
ficient to cool two gallons of cream in
about six hours from 90 degrees to 50
degrees. It should be able to do this as
well as to maintain the cabinet temperature
by compensating for the leakage and usage
loads.
Heat LOad
Total Odhide area:
"S" unit 57.6 sq. ft.
"R" unit 28.75 sq. ft.
Kelvinator heat loss tables 15 give a value of
5000 BTU/day for heat leakage from.the "R" unit with a
temperature difference of 50 degrees F5 This is for an
insulation thickness of three inches of cork or its
equivalent with.meta1 walls. 5000 BTU/ day is equivalent
to 125 BTU/hour. If a usage factor of 5% is assumed, the
total usage and leakage equals 151 BTU/hour. The usage
factor attempts to compensate for heat lost when Opening
and closing the cabinet. Since this cabinet should only
be disturbed twice daily, the usage could be expected to
be small.. Also the design calls for a tOp Opening cover
which reduces the heat lost in Opening the cabinet.

24

The amount of product load is determined by the
following equation:
Q = w c (T1 - T2)
Product load - BTU/hour

weight of material cooled - pounds

Specific heat - BTU/pound °F:

0
I

T1

1

Initial Temperature - ° Ft

T2 - Final Temperature - ° F5

If we design to cool 16 pounds from.90 degrees
to 50 degrees in six hours this becomes:

Q (16) (.68) 590 - 50)
6

72.5 BTU/hour

The total load on the compressor should not exceed the
leakage and usage load of 151 BTU/hour plus 72.5 BTU/hour
from cooling the cream, or a total of 205.5 BTU/hour. 0n
the basis of this light heat load, a 1/8 h.p. hermetic_

compressor with static condenser was considerdadequate.

Specifications for this type and size compressor
unit give a capacity of 1085 BTU/hour at 90 degrees ambient
and 20 degrees low side temperature. Since this value
represents one hundred percent Operating time and we will
design for a maximum of fifty percent Operation, the tOp
capacity for design purposes should be 545 BTU/hour. This
is over twice the anticipated load but smaller units are not
standard and so would cost more than the 1/8 h.p. standard

model.

25

Determination of Length of Evaporator Coil

In designing the coil length (area), the engineer
is given considerable latitude for the exercise of good
judgment. Fbr example, the heat transfer may be computed
from coil to air and the coils placed in the space being
cooled or the design may place the coils on the outside of
the wall. The transfer then is computed from the wall itself
and depends on the type and efficiency of the coil to wall
contact and the spacing of the coils on the wall. A figure
recommended by the engineers of Kold Hold Company, manu-
facturers of refrigeration plates, for 5/8 inch coils
fastened with.good thermal contacts every 2 inches on the
plate is 2.25 BTU/sq. ft. ° F.

With the coil mounting determined, the engineer
is allowed to set a figure for temperature difference be-
tween the refrigerant and the storage space. There are
power economies to be derived from.0peration at as high a
refrigerant temperature as possible since the coefficient
of performance of a compressor rises sharply as the low
side pressure is raised. This economy of Operation to be
gained by using a large transfer surface must be balanced

against the added construction cost of using extra tubing.

There are several factors which.make accurate
determination of coil length difficult. In most instal-

lations, design is based on the compressor Operating

26

only a fraction of the time. The coil temperature, therefore,
is not constant, varying from some low value to a tempera-
ture approximating that of the box itself. It is customary
for design purposes to assume a maximum Operating time of.
2/5 of the elapsed time. With.the static condenser which
is rather limited in capacity, this value is probably too
high and we have used 50 percent as a maximum Operating
timee
Computation of Coil requirements:
A. Fbr the "R" unit:
Total load (leakage, usage, product) is equal to
205.5 BTU/hour. If we assume 50% Operating time, the
load has an effective value for design purposes of

(2) (205.5) or 407 BTU/hour.

Using a figure of 2.25 BTU/sq.ft. 0 F5 and assuming

a temperature difference of 20 degrees (24.6 psi gauge)

Heat transfer (20) (2.25) 45 BTU/sq.ft.

Transfer area 407/45 9 sq.ft. of plate

Each foot of coil represents (2)(12)/144 or 1/6
sq. ft.

(9) (6) j 54 feet of coil

g

If a temperature difference of 15 degrees is used:
Heat transfer (15) (2.25) 55.7 BTU/ sq.ft.
407/55.7 12.5 sq.ft.

75.8 feet of coil

27

The specification for the round unit called for
a coil length.between these. - 65 feet total length or an

effective length of 60 feet.

Corresponding figures for rectangular box:
Total load (leakage, usage, product load) 245.5 BTU/hr.

Basis of 50% operating time 487‘ BTU/hr.
Heat Transfer rate 20° temperature dif. 45.0 BTU/sq.ft.

" " " 15° " " 55.8 BTU/sq.ft.
Transfer Area 20° " " 10.8 sq.ft.

" " 15° " " 14.4 sq.ft.
Coil Length 20° " " 64.8 feet

" " 15° " " 84.4 feet

Specification calls for 75 feet of coil which
should give a temperature difference Of approximately 18
degrees and a low side pressure of about 28 psi gauge.

Description of Coil Mounting

Details Of the coil mounting on the inner shell
of the "R" unit are shown in Figure 6. Expansion of the
refrigerant is accomplished by the pressure drOp through
the capillary tube (1). (Numbered references refer to
Figure 6). Current practice favors the use of capillary
tubes in small installations - 1/4 h.p. or less. They
have the advantages of small expense, adaptability to
heat exchange with the suction line and constancy of

 

 

-‘W

Rm

_-—'—~—'-

*— _.---—.——_-_—v——_
(a- .____.___-___- __ -_____..-

INNER SHELL
WITH COIL DETAILS

F180 NO. 6

29

pressure drOp. With the conventional type of expansion
valve, a small erosion of the valve seat causes a very ap-
preciable change in the pressure drOp and flow characteris-
tics of the valve. Also the small clearance of the
conventional valve together with.the very sharp drOp in
temperature across the valve orifice creates an ideal
condition for frost formation. The capillary type of
expansion system uses from.6 to 20 feet of tubing with
comparitively large clearances. The system.shown is .040
inches in diameter and twelve feet long. The amount of
tubing used depends on the temperatures desired in the box.
The longer lengths are used where low temperatures are
needed. The greater resulting pressure drOp across the
capillary enables a lower pressure to be obtained in the
expansion coil. This of course results in a lower
vaporizing temperature for the refrigerant. The capil-
lary is wound on the suction line as shown which.effect-
ively cools the liquid refrigerant in the tubing at the
expense of the expanded gas leaving the coils.through

the suction line.

Although great care is used to eliminate all
the moisture in the system, it is considered good practice
to install a drier in the low side. Such.a drier is shown
at (2). The drying agent commonly used is silica gel
which.combines physical strength, chemical inertness, and

great moisture hold capacity.

 

 

 

50

The expansion coil (5) was tOp fed although in
small coolers using freon the choice of tOp or bottom
feeding is largely a matter of personal preference. How-
ever, tOp feeding is felt to give better heat transfer
coefficients by virtue of more complete wetting Of the coil.
With refrigerants which are immisible with oil, tOp feed-
ing helps in returning the oil to the compressor. This is
not a factor with freon, which is miscible with oil and
carries the 011 back in its vapors. PrOponents of bottom
feed coils point out that the chances of getting liquid
refrigerant back in the suction line are lessened by
introducing the liquid at the bottom and letting the dry
vapor boil off. To avoid drawing liquid refrigerant back
into the compressor when using tOp feeding, the suctipn
line is supplied with an accumulator (4) and the coil is

bent up and down as shown.

In mounting the coils on the outside of the
refrigerated space and using the cold wall system, it is
essential that good thermal contact between the coils and
the metal shell be Obtained. A common practice in the
past has been to solder the coils to the shell. This
method is very effective but adds considerably to the
labor cost. The thermal bond was obtained in this unit
by bridging between the shell and coil with.thermomastic
#446 manufiactured by Prestite Company of St. Louis,

Missouri. There are several members of this group which

I..
C
‘ ‘ 9
e- .
\
U
‘ e
- ‘ ,
C
v '-
V
A. v
I
O
._ .7 ‘ H 5
t . C
e

,9

51

differ only in the conducting filler. The base is a non-
hardening asphaltic material similar to the material used
to vapor seal the box. Into this base a metallic powder
is incorporated (aluminum, carbon, etc.) to increase the

thermal conductivity.

Relative heat transfer value for metallic
Permagum and thermal Mastic as compared to air and asphalt
are as follows:

Air 1.00

Asphalt - 1.57

#440 Metallic Permagum 5.24

#446 Thermal‘Mastic 5.80

#447 Thermal Mastic 5.50

These units are only comparative and do not give

an absolute figure for conductivity.

The method of heat exchange is shown at point 7.
The capillary expansion system is wrapped around the suction
line. Both.the suction line and the capillary extend about
four feet beyond point 8 to give sufficient tubing to

make the compressor connections.

Also shown in Figure 6 at point 6 is the thermal
well into which.the control bulb is inserted. The well is
bent so that the control bulb exerts a pressure on the

sides and so will stay in place. Control in this unit is

52

from.the coil temperature rather than the box temperature.
This is less expensive than trying to place the control
in the box but has the disadvantage of allowing the box
temperature to rise when heavily loaded. As an example,
the box temperature rose to 56 degrees Ft when loaded
with ten gallons of water at 100 degrees. This tempera-
ture is 18 degrees above the no-load cabinet temperature.
Naturally this decreases the speed of cooling. If sub-
sequent experience indicates that more rapid cooling is
desirable, changing the control to the box itself would
be a logical move.

Insulation

.
The amount of insulation to use is determined by
consideration of the factors of installation cost and
Operation cost. It is usually desirable to use enough to
preclude the possibility of moisture condensation forming
on the surface. Tables have been compiled which consider
these factors and make recommendation based on experience

and theo ry e

Three inches Of insulation was used on these
boxes. This is adequate for preventing large heat losses
and to prevent condensation. 75’29 Fibre glass was used
except as indicated on Drawing No. l of the type "R" unit.
Here temlock rigid insulation was used as part of the

bottom to supply support for the inner container.

‘-

 

 

- ‘ It.
i
‘ o
o
. ‘4
‘ ‘
l
\
" ’5‘- . V‘ ‘ .. e .

 

 

'-'v§.’."r. ’

4 .

 

 

‘5”.

      

1.3" _
.33"
:2.

in
v

1"

.w

I .

x

,u

cw.

(w
ea). '4.

 
 

 

.D:

as.
.‘. .Lc‘i" "_'

7'? A?

.. i“ .‘-..’~"’Ni' es,

-'.'

Ma's 11w!"

   

,— 4v
..'

‘n

I

’-
D 90

.,\I'

Eat PLKI HLMTAL. COOLER. -75" _ .

I11 I 1. Jill) v n). 21-. - - 11.1.1111!) .1.

1 1 . .1 1 -
. 1

.1 .. 1...; u

_ - fi... I1. e .

.... 11.. .. 1 --.. 11— ..Wd.._.‘r"_r_

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1
1.
1 ., 1.11
1 w 1 . - . - y -. ,. .1
.1 ..“11. 1 J ....
1 1 1 1 ... 1a..
. 1 m _ W11 1
a n r _. . - “.4Wu1fl-Ww-1HHWA
. 1 1 -muga1
1. 1. - , T. -.
1 1.. 1 . .11. :1
1 1 ...-1.1 1.
. . 1 . 1 11a. 1
. . _ - -. .111 -111 1'1. m” 1 MI-.. .
. 1. , W. . .v . 1..
114/ 1 .. Vv. I
, 1 11 a. .1.
. . 11. a 1: L
. . . 11 . 1 1.
.1 1 1 11 . .. ., .1
-_ . 1 _. /. 11 ...- *Qf-fa
.. 1 . . / 1 1. . T11 1 h. .
1 _ -1.1-.
1 . 1 :1 .
-.- , . 11 x I 1 EH; ..
1. . . . 1 , f . . - -
«r 2.. .. 1 11-...4111. - .
/ . ix.» /\ - 1. - . W L 1M
.. 1 . T- . .
1 . . z .. M 1 1111. vi ..
. w 1. _ . . ... . .
1 1 11-1.-
1 Hm..- w 1 14 .1
- 1 . ,_ - 1 1
) \.. 31’- fl
\
. / 1 1 .. . .
lhr . ..t .. . ifi A .
a. I .. 1 ...1 Ir a .
”74/ .. I r; - W 4.... WWI-1M 1
_ ... 1 11...- 1
- .. 1 1...-
M. .1 1 1 .
_ . 1 . .1.
. . . . M 1.1 .
/
. . . 1
. 11/ 1 1 m
. .. .. 1 1 1
. .. .. 1
. ......) u . . 1 »
1 a .- -. A1111 . 1... 1
,1! ., . -. , 1
...-A . / . . w“
. . C. r/ -. 1 rd».
, 111-... 1.. .1.r ole! . 1.1 I . o . 1 s . - .. «e
1.... .1. 11- . 131-1....
. .. w W *5.“ 1.. 1H1....1 ....-..m-...-..m1.1-111- 1. 1mm“... .1-111.H.1-w.MHH..-H...- -1- 1.11111?- -- 1.-.- r8 {----1-11-1.1..- 11: 9- I 11.11
4/. . A1,... 1 111-1111,}. 1.1.
.. _
V .... .
fl\ 1. z . w

 

 

A ....N 1....

 

-—-—-'~<
.
.
.
1
.
-
.
I
1
1
-
-
.
-
1
.
| 1
A
-
. -
, .
I
1
1
1
1
-
-
.
-
-
. 1
1
.
l
-
1
1
-
.
-
.
1 -
I 1
.-
1
31:;
45- 1
,
1
1

\_

4
e

1

 

1 1, r -. 1
1 1 .1
> .
11. 11111..(-115..1.1.1-111...1 1..1.-..l-1.-11.!.1. 1. 11-1....1 . ..1.-|-... 1 .11.-. ... .1 1- . 1. .11 v 1.1 I _ 1.1 -..-1:. - 1. .1.-. 11-1 111- 1. - I1-.11..1-| 11- . . 1 - .11 . - -.1. 1 11- 1111- 111-111. .1
711111.. 1111-1111..-1111.11-. .11 .1111. 11111. 1.... -1- 11...-.-111111-1111111111. 1 k -. . .
..111w1...11 - 1 . .. - . - . 4 1. 11 1 - . .1 M d 1.
1 I ll . ~ "
. . . _ 1
... . 1 . 1 . .
, r. 1 1 1 .
t 1 v. A n . M
. 4 r 1.. . .
. ~ 4.. 1 v M u 1 m
1 r , _ .. n .
1 . .. u _ 1 .

.v-g ...-Au— ——d~..

 

 

 

- . . -. ..- .-.- - ...-.-. 111- -m...-m1:1:-m;..z .11:-a.1M;---1-:11.-z-wnwwM111111m.

 

..a . . .. 1.1... . 1 .1 1 -
. .1 .1. _ . . 1 . .
...1’ 1.. . . . .1111-11-
. .. 1‘ 1 -

 

1p. _ w.
..k a.

ll

 

 

 

 

 

 

 

1. _ 1 .
... 1. w
w . _
.1 .1 1
u a .
1 1 .1 W
.. 1 M 1
.... m .11 ..
... m w 1
. am.1
(4‘ .1 1.. a . . . 1
.w . . 1- . Y . . .. . 1. #
.. _ 1 .
1 .. . m (C- \ 1 4 fl
1‘ .4 .. m .. U w . .. s .n 1
. fl 1 1. U . ~ . . .../H
. . .. 1 1 .
. 1 . _ . 1 . 1 .. _ . .1
. . . . ~ . .. 1 .
1 . a . 3.141: ll...O. .. .
.. . 11 . M a . 1... 1.! , V1 .1111L. 17.
m n _ .1 I 1. I ‘ e . <.\ u /
.1 1 ._ a . .. m - 1 1.. . W
. .. . 1 . . at 1 K 1
.11 -.1 .11 11 11 H . 1.. . A 1 . 1.
ad. . _ a. pm .. w -1Ix h. 111.11.11.11... (1111!): (1*. .
.11 .. 1 1 . . M _ . I ..\ _ . -. . .. 1. .1 . 1 V\\
— . _ . . . . v 1 ( 1 ‘ . .1
L 1.... m w . 1 _ 1. 1 1 . h . .. f I»; _" I:
... . 1 1 .. _ . . . . .1 . + L\
1‘ ~ 1 .. n M f . r .- ./ 1 x 1
.. . .. a v ' . .. 1 . a. I 1 .. ...
W .. - 1. w .. . .1/ / . 7,. . . - , , . .1
.1 .U 1 - . . . 211.11 . .r W
_ . 1. 1 1 . . _ . . . 1*
. 1 x 11 1 1 _ . 1. . . - . m . .. .. . .. .. w L »
. . .1 i... 1 . .. . . ... . .1 ...-11.11
.1 ... .. 1 . . w ; .. . 1‘ .. 1
. . . . . . . . .. 1 .. . {J . .
.. . 1 . 1 _ . ,
. , 1 _. . .. ,. . . 1 ... . .... . .
. 1. _ r- . . ... 1 1 1 . 1. A. .1 _ . H.
5.. 1." .. z. .. . . . . i . . .. . . .l ... - 1 . . .. . u .H
. .. . . r. .11 .. .. . J . W1. m/ .e ._ . . . 1 _ 1 . m 1
, 1 . . . 1. . . ..

1
a

I,
a
1
a
-
I
M
3
_)
r.
I
1
I
.L

 

/

./
I

 

 

.. .
J ...... _ . . X. e
. . .1 . . ..
1 . ... 1 r1 . 1 . 1.1 .1111: (11:11 1.5.1.1 |1.1.. ..1.1(1-ll'111|.1011(1lI-1-|0-|-1I1-111111(§14 11..)11'111111-1 11-1111
1 . 1 . .911 - ...... ...-.1 1-1- - .1 1.. ..1 ) ... .1 1.1. .11 ......1 (I. a .. 1.!) .1 . 1 1. 4 1 1 1.1.2.1.. . ...-1 (..11111..A11..1.10.16l\c1|\lI|-¥tl11| 2 fl
/ . . . - - 1 . - . (.. .. 1 .1 . . ...: . . 1:.) l1. . I . . 1
_ - - . . .1

 

 

 

 

. .1. 1 1.
/» .
. _
- .. . 1 1 e a - 1
. 1‘ 1111. .111 .1 . (1)111: 11.1111 111 1 1 .111. 1.1111-1‘11111l1i.0. Q.. Illilllvvl-I I. r - .
- . .. .1 -. a 1. .- - . - . . .- . . .- -1. - -. -1.. 1 -.-1-.w - ..1....-. -1.. HA1... 1..:---11111-.|1..11 11.51111..- 1111.21-11.11 11.111.11.111...- 1 T .
i1. 1.. .1 A - - . . . -1 .
..-. .
. .. s

y a

_

..

I 1 . .

a m
\r. _
i| \—
... -
\
.
I

 
 

 

37

On the "8" unit, this support is obtained by
using crossed wooden 2 by 4's. These tere used because it
is necessary in this unit to space the inner container
away from the wall. This spacing is accomplished by
dressing the 4" dimension down to 3" except for 3" on the
end which is left 4". The inner box then is held by the

and projection as shown in Drawing No. 2.

It will be necessary to pack insulation into the
vertical section beside the compressor before mounting the
back panel. Insulation should also be packed into the
spaces around the wooden supports before the inner shell

is put in placé.

Plywood breaker strips are used on the tOp of the
inner shell of both boxes to prevent the flow of heat from
the outer to the inner shell. It is not uncommon to see
coolers built without this precaution but merely feeling
how cold the outer shell is at this point will indicate the
rapid flow of heat into the box.

This breaker ring is mounted differently in the
two boxes. Close inspection will show that the mounting
on the "8" unit has two outstanding advantages over the

tOp mounted ring in the "R" unit.

First, in the "3" unit the rubber cover gasket

seals on the outer jacket. This eliminates all danger of

 

38

moisture infiltration at this point. Also, bringing the
outer shell up over the breaker strip gives a metal ring
on top to take the abuse of setting cans on it.

Plywood was used on the underside of the covers
to give them rigidity. They also act in the same manner
as the breaker strip discussed above in preventing heat
flowing along a metal path into the box. All outside
Joints were sealed with permagum to prevent infiltration

of moisture vapor.

AIR CIRCULATION SYSTEM
Both compressors were specified with static con-
densers. This means that air circulation over the con-
denser is by natural draft. The use of this type conden-
ser eliminates fans and other external moving parts. They
are justified on small capacity units such as this if
some means of encouraging natural draft is used.

Both cabinets contain built-in stacks that in-
crease the flow of air through the condenser. Air is
drawn from.the floor through the condenser where it picks
up heat and becomes lighter. This creates an updraft
which draws in more cool air to continue the process.

We were unable to find design procedures for
stack area or height. The dimensions used are adapted
from current industrial practive.

Finish
Both units were finished with aluminum paint on

the inside. Th "R9 unit was built according to our plans
by the Revco Company, Inc., Deerfield, Michigan. It re-
ceived a baked white enamel outer finish. Since we have
no baking ovens in our department, the "S" unit was spec-
ified with aluminum finish. It may be enameled white if
desired.

PUTTING UNIT IN OPERATION

After the cabinet is finished the coils are
throughly dehydrated before being connected to the com-
pressor. Revco, Inc. heats the coils four hours at 280
degrees and then draws a vacuum of from 15-18 microns.
Slightly lower vacuum.may be used with 50 microns the re-
commended limit.

Freon is introduced into the evacuated coil
until a positive pressure is assured. Connection is made
to the compressor, connecting first the high side and
then the low side. Back seat the low side and then the
high side valves. Dehydrate by heating the freon charg-
ing line and connect to the low side valve. Start the
compressor and allow freon to enter the low side valve
by loosening the valve periodically. (Valve is closed
when front seated - Open when back seated and vented to
the atmosphere when in an intermediate position) Charge
should be introduced slowly. The right amount has been
charged when the frost line appears just out of the box
with the compressor running full time. Freon should be

purged if the frost line moves near the compressor.

40

The "R" unit was put into Operation in the above
manner. The box temperature reached - 14 degrees with a
coil temperature of - 19 degrees with the compressor run-
ning full time. The control was then hooked in and the
unit run at about 45 degrees for one week before under-
going further testing.
TESTING PROGRAM
In evaluating the cooler performance, tests were
set up to provide the following information:
1. No-load current consumption.
2. Cooling rates on water in different.amounts and
in different containers.
3. Cooling rates and quality studies on cream.
4. Performance under conditions as they exist on

an average farm.

No-Load Current Consumption

The no-load current consumption test is run on
new units to obtain cost of Operation figures and to check
the design heat loss figures.

The unit was set up in a room of the Department
of Agricultural Engineering. The test set up was as shown
in Fig. 8. The circuit is controlled by a thermal control.
The sensitive bulb of‘this control is therefore by the
coil prOper. Control is of coil temperature. A wattmeter

was placed in the circuit to record the current consump-

tion. Hooked in parallel with the compressor was a self
starting electric clock which will show the total Operat-
ing time of the compressor. This same general setup was
used in all subsequent tests.

After the unit had come to equilibrium, the test
was started. Fbllowing are the results of three no-load
tests.

NO-LOAD TEST

Table No. 1
Test Time KWH Ave. Room.Ave. Cab. KWH Used/24 Hrs. °Fu
No. Hr. used Temp Temp.
1 44 .60 68 ' 44 .01565
11 156 5.0 76 37.5 .01375
12 96 1.9 75 41 .0139

Average .0137

The above results show good agreement despite
the widely different ambient and cabinet temperatures used.
The unit of current consumption used does not conform to
any recognized standards but it does put the data in a
form that is easily used in further computations.

Cooling Rates on Water

Cooling rates were run on water to indicate
something of the speed of cooling that could be expected
with cream. COpper-constantin thermocouples were used
for temperature measurement. The readings were made with

a Leeds and Northrup potentiometer. Examination of Figs. 9

0mm: mahmm ...mu... “.0 10kmxm 0.h<3<¢o<_o

mom $523 a: a:

 

 

 

 

 

 

 

a4_oo zo .socezoo
.ozcuzp >o aue<¢uao

 

 

 

 

 

 

 

 

 

 

 

 

 

A 105.3m
< V ......
\ Q

mmhuv‘hhh;

 

 

 

2:22.... a. commucazoo
3.55:: 23. oh 353

100.5

 

 

 

 

F180 NO. 9

 

-J‘..- g 77““; -

Fig. No. 10

--.—-

-....a.~h

-L - »‘—‘—_._.

F18. NO. 11

 

 

 

 

 

46

and 11 will give the reader the general test setup. The
thermocouples were shielded in five millimeter glass tub-
ing which had been drawn to a capillary at the end and
then sealed. The capillary was drawn small enough so that
the thermocouple junction just fit. The thin glass walls
and good physical contact made the thermocouples rapidly
responsive to temperature changes.

The combination thermocouple'holder and con-
tainer cover was drilled for seven tubes. It was made
from two different thicknesses of plywood. The thicker
piece was of a smaller diameter then the mouth of the can.
A thin piece was cut with a larger diameter and fastened
as shown to form the cover. The couples are adjustable
in depth so that a good cross sectional picture of tem-
perature conditions can be obtained.

A summary of the results obtained with water are

given in the following table.

Table NO. 2

Test Size Lbs. initial Final Time Initial Rate of
No. can water Temp. Temp. Hr. Cooling oF/Hr.
2 10 Gal. 72 98 74 8.5 2.56

5 5 Gal. 55.5 91 66 8.5 2.94

4 5 Gal. 16.5 86 57.5 8.5 3.40

5_ 5 Gal. 16.5 87 54 8.5 5.80'

6 10 Gal. 72 89.5 87 1.0 2.50

7 5(gal. 72 81 61 7.5 2.67

Typical cooling curves are shown in Fig. 12.
These test show that the rate of cooling was relatively
slow in all cases. The rate is affected by both the amount
of water to be cooled and the container used. The dif-
ference caused by the containers is due to the larger area
for heat transfer when using smaller containers.

Determination of Compressor Performance

The coefficient of performance of a refrigeratiOn
machine is defined as the ratio of refrigeration obtained
to the heat equivalent of the power supplbd. 18

Coefficient of Perf. : Heat removed - BTU's
(KWH’ (54I27

A refrigeration unit is not considered to have
an efficiency in the same sense as a power plant since it
does no useful physical work. Its function is rather to
pump heat from a low temperature T2 to a higher tempera-
ture T1. Thermodynamic consideration of the carnot or
ideal refrigeration plant leads to the following
treatment.

The coefficient of performance in a carnot

refrigeration plant is equal to:

 

 

Q2 : WT2 (82-81) : T2

Heat absorbed in evaporator

D
N)
I

Q1 - Heat rejected by the condenser

2
ll

weight of refrigerant circulated

T2 : Absolute temperature in evaporator

 

 

 

 

 

 

 

 

 

 

 

380LV836N31

 

 

 

 

ӣ90: a u!.#
0.. w w w m m w M .« fl

_ _ so
I! on

// / . N.” MQOJm
. O

/// amt; .mm._ 0.2
n.~ macaw // /// . as

zqo .eoxm. zonaqe n. mWWWNu 1//
«n+4; do; can \\ //////////

w I 6.

 

m.~ . macaw
zqo zoance 9 z. \e.
mus<3 .mmn «a

 

 

 

 

 

 

 

 

 

 

 

+-

muk<3
mm>mao 02.40001

 

dc

49

T1 : Absolute temperature in condenser
s2 = entrOpy of vapor
s1 : entropy of liquid

Inspection of this equation shows that the efficiency of
performance is a function of the absolute temperature and
that the efficiency rises as the difference between T2

and T1 becomes less.

Inserting values obtained in testing the "R"
unit with the control setting at the lowest temperature,
we have the following:

Evaporator temperature 220 F. 4820 R

Condenser temperature 1120 F. 5720 R

Carnot coefficient of performance 482 - 5.55
572 - 482

 

In cooling a load of 5,212 BTU's over a period.
of 162 hours, ambient temperature 75 degrees and cabinet
temperature 43 degrees, the unit used 5.4 KWH. Using the
previously determined figure of .0157 BTU/24 hours 0 F.
for heat leakage with a temperature difference of 52°:

( 247'1rs.y

 

This leaves 5.4 - 2.97 or .43 KWH to handle
the load of 5,212 BTU or a coefficient of performance

0. of P. = _5 212 = 5.58
fresh 54157

This value for the coefficient of performance is higher

than might be expected for a small unit. EXpressed as

'5

.2”

N?

. oz

_¢ 0? mm

)

..Hrm

mm

Kn mm mm

mUPDEI - NI;

 

H

d

H

IJ

#

4

i

 

 

cm - w o
|.\/\I \\
_ .oz
ozCemw nomkzoo

mmammwmd mo_m . 102i

 

 

ON.

Oc

cm

00

OO~

ON.

01¢.

BHHSSEBd

lSd

52

percent, this becomes 66.7% of the theoretical. The dif-
ference between this value and 100 represents the

inefficiencies in the compressor and motor.
EFFECT OF HOLDING CREAM AT LOW TEMPERATURE

Since these coolers were designed to maintain
high quality in farm held cream, much stress was given to
the following series of tests which were set up to closely

simulate farm conditions.

Many investigators have found that adding warm
milk to cold milk has a tendency to stimulate the activity
of the enzyme lipase. However, there is no doubt that the
farmer would be very happy to be able to add his cream to
the previously accumulated cream with no further treatment.
We decided that this point should be explored so in each
test twenty gallons of milk were divided into two equal ten
gallon portions before separating. When ten gallons had
been separated, the cream.was placed in a cold water bath
and the temperature was lowered rapidly twenty or more
degrees before placing in the cooler. The results of this
treatment are given in the series of samples lettered "A".
The remaining milk was separated and the cream was placed
in the cooler at the separating temperature. This series

was lettered "B".

This procedure was repeated for four consecutive

1“

55

days with the cream added to the previously accumulated
cream. Four series of runs were made with "A" and "B"
treatment in each series. Thus a total of eight batches
were cooled and tested. Only in run No. 2 was the cream
stirred into the older cream. In runs 1, 5, and 4, the

cream was merely poured into the older cream.

In runs 1, 2, and 5, the milk to be separated
was taken from.the delivery truck at the college receiving
station. Run No. 4 was made from college herd milk. A
relatively high bacteria count was obtained on this milk
due to the fact that it stood for some time before separat-
ing. (See Table No. 5) There was no way of telling whether
the milk taken from the delivery route was morning or night
milk. The milk was sampled immediately for bacteria count
and then warmed to approximately 95 degrees before

separation.

An effort was made to choose milk with an average
to poor quality since it is recognized that the quality
of milk produced by the farmer that markets cream is
generally of lower quality than the whole milk producer.
That we did get highly contaminated or poorly handled milk
is apparent from both the bacteria counts and the flavor
criticisms. In no case was there acid deve10pment in the
cream to a degree sufficient to impair the flavor of

butter made from it.

‘C

, ~——————-_1:.\=3 s YET"

Table NO. 5‘
DATA ON MILK SEPARAT‘ED

 

 

 

 

 

 

 

 

 

 

 

 

 

RUN DATE FIRST SECOND THIRD FOURTH
ND. STARTED DAY DAY DAY DAY
I 4/I5/47 250.000 2Io,ooo 96,000 660,000
”CTR” 2 4/26/47 2I6.Doo ”50,000 900,000 50,000
00”" T‘ 3 6/23/47 20,000,0“3 8,000,000 2,000,000 §,700,000
.4 7/0/47 90,000 30,000 660,000 770,000
I S 55 6
TEMR| 7' o ' 0
MILK 2 62 63 as so
"new“ 3 _ 72 7D 69 70
'F
4 7s 7s ‘ so 76
I V I00 90 as 7 es
TEW' 2 as 92 95 I00
SEPARATE!) 3 96 , as 97 I00
..F
4 96 as as S7

 

 

 

 

 

 

 

 

 

MILK WAS RECEIVED COLD AT THE COLLEGE Rs-
CEIVING STATION. IT WAS WARMED To 90-I00°
BEFORE SEPARATING. THE MILK WAS SAMPLED
FOR BACTERIA BEFORE WARMING.

55

The butter was all hand made and in many cases
the score could have been raised a point if more buttermilk

had been removed.
Effectiveness in Cooling Cream

The cooling rate was faster than had been ex-
pected considering the rather slow rate with water.
Figure No. 15 shows a representative curve made from data
obtained in run No. 1. This shows a cooling rate on the
"B" sample of 25 degrees in the first four hours or 6.25
degrees per hour. This may be eXplained by the smaller
volume of cream per can and by the lower specific heat of

cream.

Each subsequent day after the first shows a
lower peak temperature due to the mixing of the cold cream

with the warm.

Table NO. 4 tabulates the weight and temperature
of the cream used in the tests. The weight varied from 6
to 10.5 pounds depending on the richness of the milk used
in the test. The separator was set to deliver cream test-

1118 40% fat.

It can be seen that the cream in the "A" series
averages about 20 degrees lower in temperature than the

”B" series.

2 .. o:

J

.....ME

mm: 0:,

uzz.

N.

 

'_L’

‘I J
I.
.

:12 \. IIILAIII

d
q

h¢\o_\¢

 

/,

7.
. /’j

/r

 

/

/

 

£2 uh 20:. (cc

 

-..um 5 88¢ .PBIIIII
838qu .226 .2. I I l

52“me

 

76/,

'

 

 

 

 

.2122. .. 5132’
mo<x 22m some qeqo

mfido 130m mom >40
Io<m.omoo< 24mmo

,mu>m= 0 22.68

 

 

 

 

 

 

 

 

on

0.?

O
I‘D

O
0

O
p.

00

on

 

3801'8341'31

:Io

amcwm 20.

9

final... >20 ...mZtmmbdcmm 0.... own): COO—IMO

 

 

 

 

 

 

 

 

 

 

(max... 0... 03m»! gone 40 coorma 4min. on can)... izwz roono on...
. "I

1.3 m u A _ m u A
:ocwm

> m > > m > m > m > m p. m > m
o .o e a , 9»... o m a me as so no we on 3 .3

EEEEE

m. ...... so 4 3a Nu who a me so a»... .3 so we so
so a u .2... 4 Pa 4 93.. no as as m. a» me co
«m 5.6 Pa cheese 6 a Na 4 a. .3 am on an so so no
a.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

.2 m3: «mean no 25.23 an ...rx 5.... 2:23 .232 6263 .23. .0
can 6 3:02.336: (so «moraine ..zo 4:." nan»:

a) r r02 1 02.302”.
«.1 a) 1_or<

82.3 .623. no.
Western 1: r>unrno ......

.3... 5.» 532.3 .m...

unroi ...:m umv>8’4_oz «filmmaDHCSM.

....r.

.....n 3:: spa 325:3 2:. .34 32.3..

004: ublwrmm (man 13 .2 din GOO—una.

58
DevelOpment of Acidity

It is interesting to note that the difference in
deveIOped acidity is significantly larger in the "E" series
than in the "A" series only if milk of high initial bacteria

is used.

Figure No. 16 shows this development for the
poorest batch and for the best. The "B" series was notice-
ably more acid when the initial bacteria load is very high
but when milk of relatively good quality was used, neither
series showed much acid develOpment. This indicates that
cream.from freshly produced milk can safely be added to the
cooler at separation temperature with.no criticism on an
acid development basis. Further study of enzyme activity

or of other considerations may alter this vieWpoint.
Flavor of Stored Cream

The tabulated data of Table No. 5 gives both the
acidity deveIOpment and a flavor score of the quality of
butter that could be reasonably expected from the cream.
The observer is presented with the fact that acidity
develOpment is not the only criteria of deterioration in
quality. Three samples scored 95 after 96 hours holding
and these samples had acidities of .180, .185 and .155.
However we have a sample with the lowest acidity, .155.
which graded 92 and made butter grading 91. This sample

p.

.50

.30

ACIDITYf PERCENT

.IO

 

 

 

I4:

/ POOR

/ I
/ ‘3’
CREA FRO“

,0
/

NILN A'aI

 

.20

A.

 

 

/ :A ERIou 000D

 

 

 

 

 

 

 

 

24 4D 72

ELAPSED TIME " HOURS

GRAPH SHOWING DEVELOPED AOIDITY WITH GOOD
HILKIAVE. BACTERIA, 300,000 PER 00.)

‘ POOR NILK I'AVE. couNT 9.050.000)

AND WITH

F18. NO. 16

 

emuwm 20. m
>0.D.H< >20 mr><ow ommmOHm om<mr0umo .2 ...Im omMDZ.

 

 

 

 

. can»: >223 g. . mr><0a mooam
4.3m
zocrm . m . a A _ m u A
> m > m > m > m > m > m >‘ m > m
0 .8 .....0...~0 .00 ..00 .80 .3 .3 00 00 00 00 ea 00 0a 00

 

.NA .00 .00 ..0u..a0 ...... .-.u.._A0.A0 00 00 0.... 00 00 on 00 0a

 

km .00 ..NO .30 ..NN .NOO.UHO.30 .50 mm 0U 06 nu mu m. cu 0m

 

NM .00 ..m0 ..VO ..ou.»oo..uuo..ao..oo mu mu 0.» ON on 0. 00 om

 

, . . M u a 0
mm .50. .50 ..mo .NNu .Nmo .umo..uu..uu mm mm m. mm. mm 0. on ma

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

mr><0a 02.10.01. .
70523.: a>20_0-...mm0 . A- 1.0: ...mmo.

s. 050.3,: >20 .. u .. 050.15.. 820.23 .. 222.50
a. 50:... ...mmo. .. .

61

(series "A", run No. 4) developed a slight utensil flavor
during holding. The "A" series of run No. 2 was also
criticised for a similar defect. It may be dangerous to
draw conclusions from such meager data, but the impression
is received that maintaining too low an acidity may inhance

the chances of metal catalyzed oxidation.

Acidity development can be controlled by control-
ling temperature. Perhaps a small amount of acidity should
be developed to exhaust the dissolved oxygen in the cream
and thus 510w the development of oxidized and metallic
flavors. An indication that a small amount Of acidity may
be beneficial if cream is to be held for three or more days
is shown in the "B" series run No. 2. This is the only
sample of cream that made 95 score butter yet it had an
acidity of .225%. There were five other samples with
lower acidity which graded no better than 92.

Treatment of Cream After Holding

After holding the cream the prescribed 96 hours,
it was neutralized with Wyandotte C. A. S. if the acidity
of either "A" or "B" was in excess of .20%. The cream
was then pasteurized by setting the can in hot water. A
pasteurizing temperature of 156 degrees F. was chosen.
When the cream temperature reached this value it was held
ten minutes and then cooled rapidly in cold water. The

cream was held overnight at 54 degrees, heated to churning

62

temperature and churned in a small laboratory churn. See

Table NO. 6 .

The butter was worked by hand and about 2.5% of
salt was added. The butter was stored at 40 degrees over-
night and then graded. The grading was done by Mr. G. M.
lrout and Mr. J. M. Jensen of the Dairy Department of
Michigan State College.

Butter from runs one and two were given storage
stability tests of ten days at 70 degrees. All samples
received the same score after this test as they had re-

ceived previously. Flavor scores are shown in Table NO. 7.
PERFORMANCE UNDER FARM CONDITIONS

The cooler was placed on the farm of Austin
Cunningham to test its performance under actual conditions.
Mr. Cunningham was recommended by the Dairy Department as
being cOOperative in spirit and a producer of considerable
cream. At the time of the test he was delivering about

150 pounds of 40% cream every week.

The cooler was placed in the basement of Mr.
Cunningham's home and set up with a meter and a clock as
in the laboratory. (Figure No. 17) Four new "shot" cans
were used for storage of the cream. The cream was added
with no cooling or agitation filling each five gallon can

in turn before starting on the next one. This represents

D

02.2030 000.000 ...: 5. 2.0.2030 023.0 0»

0030...... 02¢ 00:; 0.00 2. 30.03. 00.000 04; 30000 0..» .0052...
20» 00... 02:0 0.. 0030...... 0...... 02.0200 0; 200 0.: .0020}... 0:.
0005.00.20» 02.0.0000... use 20.; 0.0.03 00: .0 5; < z. .3000 0.:

 

 

 

We

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

02.2.5200 :00 10:0. 20.300. 02.. 4. 05:00 .0 000.0005... 04.... 2.3.00
00 00 00 .0 00 .00.. 00.. oz 00_._00_. 00. ... .00.. 0
.0 00 00 0.0 00 00.. 00.. 00> 002—000. 00. 3.000 0
00 .00 0.. 00 00 00.00.. 00» 000. 00.. 00. 3.00... 0
.0 00 ..,.0_m.20."z 00 00.. 00.. oz 00.. 00.L 00. 5.0... _

he 4 m 4 ...—o

m 4 m 4 .010» , m .0 00m. 020.. 0.... omkmdhm .02
00000 02:. 02.5.0.3 02.2”“:0 .2500... .2000 8-5000040 whdo 23m
cutbowzzcaxo T5004. >....0.0¢ . g

 

 

 

mmnooo Z. wrdo .0 62.040

. oz 0 Home

.... mwkud 24mmo .....o kzuih<mmh

 

 

0....._<._.m2n.o.xo ....m u r.

5.2000000 -0 0000 00.: - 0
0000000 _ 0000 .00 -0
000400.00-»

o.o< ....m ..N
0344th ...m

omw0n9024m ....m u.

u......Ew_o_._._mo mo><40

 

. 0. n .0300 000.
-0000000-0000 m N. 0.0.0.500

 

mmum .mNmNmOm .mNmnmNm .mNmmmNQ _mNmNm _mmmnm wmoom

 

 

 

 

 

 

 

 

 

 

 

00.0000000000000004000000.
¢~m N _ ¢ m N _ ¢ m N _ 02230.
.00 2 0.200.
000000 00:00 . 00:00 00000 20000

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

00330 000.039 oza. 24000
0 .oz 0.000

 

 

 

 

 

Fig. No. 17

66

the minimum.effort on his part and the worst conditions
that could be expected.

His practice in the past has been to cool the
freshly separated cream immediately to about 65 - 70
degrees. This was then added to the old cream in a ten
gallon can. No further cooling was provided so that the
storage temperature became the temperature of his basement
where the cream.was held. The cream was delivered once

every week.

TABLE NO. 8

QATA ON THREE WEEKLgRQDUCTION

 

 

Cream Cooler Can Temp. Ave. Current
EIOQEpedfl, Used NOQ#, Reed. Acidity Acidg=§gpre Usedggflfl
7-12-47 1 73 .855 89

to No .778
7-19-47 2 73 .720 89
7-26-47 1 45 .42 90
to Yes 2 43 .54 .295 92 4.7
8-2-47 5 43 .25 92
4 62 .17 92
8-2-47 Yes 1 42 .53 91
t0 2 42 054 .265 92 405
8-9-47 3 42 .24 92
_______A 4 64_i [l4 93

 

None of the cream showed any trace of metal or
bitter flavor. The oldest cream had been held seven days
and had an old flavor in both batches. As the cooler is
set, acid develOps to an appreciable degree in seven days.

It was felt that the combined cream could be used to produce

..--

67

92 score butter both weeks. We do not know the Optimum
temperature for storage at this time. Evidence points to
danger in too cold temperatures as well as tOO warm. It
seems that this Optimum temperature would vary with the
producer depending on the condition of the cream that is

placed in the cooler.

The tests on Mr. Cunningham's farm are going
forward. During the week ending August 16, 1947, he is
filling all four cans simultaneously. This should pro-

vide more rapid cooling and may lower the average acidity.

On the assumption that 98 score butter could be
made from the cream delivered on August 2, 1947, average
acidity .295%, and that his regular delivery without the
cooler would produce 89 score butter, Mr. Cunningham would
market a product worth $3.05 more for this weeks period
'by the use of the cooler. Added to this would be a saving
in time and water since he previously cooled the cream

down before placing in the storage can.

Mr. Cunningham's personal reaction to the cooler
has been extremely favorable. He would be very interested
in Operating under the premium.aysbem and would be willing
to purchase a cooler to maintain high.quality in his
product; Present plans call for leaving mhe cooler on his
farm for a period Of several months. We believe much

valuable information can.be Obtained by a careful inspection

68

Of the cooler after a prolonged periOd of unsupervised
usage. Typical information would be points Of physical
weakness and something Of how dirty the cooler will become

after long usage.

DISCUSSION

Most of the work in refrigerating dairy products
has been centered about milk. While the use of a dry box
has not been successful in cooling milk, we believe that it

has shown great promise as a means of holding cream.

Several Observations were made in the course Of
the project. First, very little is known about the physical
behavior of cream. There is room for research On such
basic prOperties as specific heats, coefficients Of heat
transfer and viscosity studies. We Observed that cream will
become extremely viscous, almost plastic, when cooled if it
is separated from milk which has been held cold and rewarmed
to about 85 degrees before separating. This plasticity
does not Occur in cream separated from fresh, warm milk or
from cold milk which is warmed to 95 - 100 degrees and held
for a few minutes. This must be caused by incomplete melt-
ing Of the fat and agglomeration into larger particles to
cause the high viscosity. Such thickening might improve
the customer appeal of whipping cream and thus be 0:

commercial value.

19

69

Cooling rates on cream were more rapid than was
predicted from the values given with water. This seems to
indicate that the characteristic formation of a thick layer
of cream on the inside container wall observed when cooling
with cold water does not occur with cold air. This elim-

inates some of the Speed advantage expected with water.

The quality of the cream.beld in the cooler was
all that could be expected. Many of the experiments were
run in the spring and feed flavors were observed more
often than any other defect. The "shot" cans and the
separator bowl both had some exposed iron and metallic
flavors were observed in two samples. The acid develop-
ment could be kept below .20% very easily. The butter
was hand churned and contained considerable buttermilk.
This caused some lowering in score but all samples had

good aging qualities.

Points particularily worth further investigation
include: (1) Finding the Optimum temperature of storage.
(2) The method of adding cream, whether it should be added
warm or cold. (5) Should the cream.be thoroughly stirred
into the older cold cream or added carefully with as little
mixing as possible. (4) What acidity should be allowed

to develOp in stored cream.

The use of vacuum in conjunction with evaporative

cooling might show interesting results. It is possible

70

that low pressure could be maintained more easily than
refrigeration. Use of a vacuum.chamber might also improve

quality by removing dissolved oxygen from the cream.
CONCLUSIONS

(1) A dry box type of refrigeration unit ef-
fectively maintains the quality of farm held cream for
about five days. This cream should score 92 or better.

Longer storage is not recommended for best quality.

(2) The use of this refrigerator will show a good
profit to the farmer providing a reasonable premium is

given for producing quality cremm.

(5) These units may be designed to provide

cold storage for eggs or other perishables.

(4) To keep the investment cost low, they

should be retailed at cost by the creamery.

 

(1)

(2)

(3)

(4)

(5)

(8)

(9)

(10)

(ll)

(12)

71
LITERATURE CITED

1941. Bacterial ASpects of Farm Iilk Cooling
Pa. Agr. EXpt. Sta. Bul. 404 13 pp.

AnderSon, T. G., and Nicholas, J. E.
1943. Influence of Cooling nethods on Bacteria
in Milk. Pa. Agr. EXpt. Sta. Bul. 454. 17pp.

Anonymous
1939. Preserving Cream with Salt. Butter and
and Cheese Jour. 39: 26 - 28

Costell, C. H., and Garrard, E. H.
1939. Preserving Cream with Salt. Canad.
Dairy and Ice Cream Jour. La: 19 pp.

Caulfield, W. J., and Martin, 3. H.
1938. An Evaluation of Several Hethods of
Cooling Cream. Jour. Dairy Sci. g1: 13 - 20.

Caulfield, V. J., Nelson, F. E., and Eartin, J. H.
1940. Effect of Salt on the Keeping Quality
of Cream. Jour. Dairy Sci. g3: 1215-1228

Dill, R. S., and Cottony, H. V.
1946. Laboratory Observation of Condensation in
Wall Specimens. Natl. Bur. of Stds. Report
BMSlOS. Washington: Supt. of Documents

Golding, N., and Miller, D. D.
1943. Optimum Temperature of Growth of 22
Cultures of OOSPORA Lactis. Jour. Dairy
Sci. §§: 251-260.

Hunziker, O. F.
1940. The Butter Industry 3rd Ed. 521 pp.
LaGrange, Ill. Author 1 - 23

Jensen, J. M., and Bortree, A. L.
1947. Influence of Separator Cleanliness and
Temperature of Cream Storage on Cream Quality.
MiCho ASP. EXpt. Sta. EU]..- 32: 243-255.

Nelson, F. E., Caulfield, W. J., and Kartin, W. H.
1942. Further Studies on the Use of Salt for
Improving the Quality of Cream for Butter-
making. Jour. Dairy Sci. fig: 59 - 70.

Nicholas, J. E.
1941. One Can Electric Milk Coolers.
Agr. Engin.,§§: 259 - 260.

(15)

(14)

(15)

(16)

(17)

(18)

(19)

(so)

72

Parker, M. E.
1946. Butter Manufacture. Amer. Soc. Refrig.
Engin. Appl.: 249

Paulsen, E. H.
1946. Milk Plants. Amer. Soc. Refrig. Engin.
Apple: 242

Powell, M. E.

1938. Flavor and Bacterial Changes Cccuring
During Storage of Sweet Cream which had been
Pasteurized at Various Temperatures. Jour.
Dairy Sci. El; 219 - 226

Kelvinator Corporation
1939. Refrigerator Daily B.T.U. Hall Leakage
Tables. Kelvinator Service Kannal.
Form 4540. Detroit

Thompson, D. 1., and Facy, H.
1940. Effect of Salt on the Hicroflora and
Acidity of Cream. Butter_and Cheese
Jour- g1; 12

Venemann, H. G.
1946. Refrigeration Theory and Practice.
2nd Ed. 336 pp. Chicago - Eicmerson
‘ and Collins.

 

Williams

1939. U. 8. Patent No. 2,192,864. A Kethod
of Preserving Cream pith Salt. Original
not seen. Cited by Caulfield, etc. 1940

Wooley, H. H.
1940. Moisture Condensation in Building walls
Natl. Bur. of Stu. Report 8K363.

’35,;

“1 USE “NE! Jun 22 194%

JTUIZO 7 I94 8

‘48
’71 O O
jxug ”h ’1»

Sep 27 ’48

fl.

 

 

 

; T63l.2 190934
5253

.0

 

 

 

 

mummymmmmtltmlmllfllmlmH