Chemical refrigeration system

A chemical refrigeration system utilizes the endothermic reaction of chemicals such as potassium chloride dissolved in water to refrigerate the water. To achieve a large drop in water temperature, plural stages of endothermic reactions are utilized in a plurality of chillers to chill the water in increments. Heat exchangers are also provided in recirculation paths of the chillers to increase efficiency. The system will operate successfully in the zero gravity conditions of outer space.

BACKGROUND OF THE INVENTION 
The present invention relates to a refrigeration system suitable for use in 
the zero gravity conditions of outer space. More specifically, the present 
invention relates to a chemical refrigeration system in which a liquid is 
chilled from the endothermic reaction associated with dissolving selected 
chemicals in the liquid. 
Conventional mechanical refrigeration systems, which operate on the 
principles of vapor compression and utilize conventional components such 
as mechanical compressors and condensers, will not work properly in the 
zero gravity conditions of outer space because vapor cannot be separated 
from liquid without a great deal of difficulty under these conditions. 
Accordingly, when it is desired to chill or refrigerate liquids in outer 
space, conventional vapor compression systems may not be utilized. 
The present invention takes advantage of the fact that certain chemicals, 
when dissolved in a liquid such as water, produce an endothermic reaction. 
This endothermic reaction cools the liquid down below the ambient 
temperature. The degree of cooling depends on the nature of the chemical 
used. However, the amount of cooling is proportional to the amount of the 
chemical which may be dissolved in the associated liquid, which is fixed 
by the solubility limitations of the chemical. Therefore, for any given 
volume of liquid and associated chemical to be dissolved therein, there is 
a limit on the amount of cooling that can be achieved, namely, the drop in 
temperature of the resulting solution, as compared to the original 
temperature of the liquid. Therefore, if one wants to chill a liquid from, 
for example 82.degree. F. to 36.degree. F., such a drop in temperature is 
difficult to obtain merely by dissolving a quantity of a selected chemical 
in an associated liquid. 
Accordingly, a need in the art exists for a refrigeration system which 
utilizes the principles of chemical refrigeration achieved by dissolving a 
selected chemical in water, but utilizes the chemical/liquid solution in a 
system in such a manner that larger temperature drops can be achieved than 
normally permitted by the solubility limitations of the chemicals 
utilized. 
SUMMARY OF THE INVENTION 
Accordingly, it is a primary object of the present invention to provide a 
refrigeration system suitable for use in outer space under zero gravity 
conditions. 
It is another object of the present invention to provide a chemical 
refrigeration system which can achieve large drops in liquid temperatures 
not limited by the solubility limitations of a selected chemical dissolved 
in a liquid. 
It is a further object of the present invention to provide a chemical 
refrigeration system which will operate successfully with only a minimal 
amount of external energy being applied thereto. 
It is still a further object of the present invention to provide a chemical 
refrigeration sytem suitable for use in outer space in combination with a 
post-mix, carbonated beverage dispensing system. 
The objects of the present invention are fulfilled by providing a chemical 
refrigeration system for chilling a liquid from a first temperature to at 
least a second temperature by means of an endothermic reaction of selected 
chemicals dissolved in the liquid comprising: 
a source of liquid at said first temperature; 
a source of said selected chemical; 
chiller means having reservoir means in which a predetermined quantity of 
said selected chemical is dissolved in a predetermined quantity of said 
liquid to create said endothermic reaction and a resulting cooling 
solution, said cooling solution having a temperature intermediate said 
first and second temperatures, and a conduit passing through said 
reservoir means in heat transfer contact with said cooling solution, said 
conduit having an input end and an output end for passing said liquid to 
be chilled, said reservoir means having an inlet for introducing said 
liquid into said reservoir and an outlet for accommodating the flow of 
said cooling solution out of said reservoir means; 
heat exchanger means having a first inlet connected to said source of 
liquid at said first temperature, a second inlet connected to said outlet 
of said reservoir means for receiving said cooling solution, a heat 
exchange chamber for transferring heat between said liquid at said first 
temperature and said cooling solution to lower the liquid to a temperature 
intermediate said temperature and the temperature of said cooling 
solution, and an outlet for said liquid of intermediate temperature 
coupled to said input end of said conduit and the inlet of said reservoir 
means; 
pump means for circulating said liquid through said system from said source 
of liquid to the output end of said conduit, said liquid exiting from the 
output end of said conduit at said second temperature. 
The heat exchanger makes use of the cooling solution formed in a chiller 
means to recirculate the same into thermal contact with the source of 
liquid at the first temperature. Accordingly, this recirculation of the 
cooling solution cools the liquid down which enters the chiller means to 
lower the temperature drop requirements of the chiller means. Therefore, 
the temperature drop or delta achieved are not limited by the solubility 
of the selected chemical in the liquid within the reservoir means of the 
chiller. 
In order to add even further efficiency to the refrigeration system, a 
second chiller means may be provided in tandem with the first chiller 
means. The second chiller means has a second reservoir for containing a 
second cooling solution, said first cooling solution being formed by 
dissolving a first supply of said selected chemical into liquid entering 
the reservoir means of the first chiller means from the ouput of the heat 
exchanger means. The second cooling solution is formed by dissolving a 
second supply of selected chemical into liquid contained in the second 
reservoir of the second chiller. The liquid in the second reservoir of the 
second chiller is supplied from the output end of the conduit, which 
passes through the first cooling solution in the first reservoir. A second 
heat exchanger may also be provided, having a first inlet connected to the 
source of liquid to be chilled at said first temperature, a second inlet 
connected to an outlet from said second reservoir, a heat exchange chamber 
for transferring heat between said second cooling solution and said liquid 
at said first temperature, to lower the liquid to a temperature 
intermediate said first temperature and the temperature of said second 
cooling solution, and an outlet for the liquid coupled to the input end of 
a second conduit. The second conduit passes through the second cooling 
solution in the reservoir of the second chiller means in heat transfer 
contact therewith, to cool the liquid to a third temperature below the 
second temperature. The refrigerated liquid output from the output end of 
the second conduit is then utilized in an appropriate manner.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to FIG. 1, there is generally illustrated a post-mix beverage 
dispensing system including a water supply 11, a chemical refrigeration 
system 13 for chilling water provided by supply 11, a carbonator 15 for 
carbonating the chilled water, and a syrup supply 17 for providing syrup 
or flavor concentrate to a dispensing/mixing valve 19 for mixing with 
carbonated water in desired proportions to form a post-mix beverage. FIG. 
1 generally includes conventional components with the exception of the 
chemical refrigeration system 13. In conventional systems, refrigeration 
system 13 would normally be a mechanical refrigeration system including a 
compressor and condensor. However, when it is desired to make and dispense 
carbonated beverages in outer space, the conventional vapor compression 
refrigeration systems will not operate satisfactorily under zero gravity 
conditions. Accordingly, the present invention relates to the development 
of a chemical refrigeration system 13, as embodied in FIGS. 2 and 3, to 
satisfactorily refrigerate a liquid such as water in the zero gravity 
conditions of outer space. 
Before referring directly to the preferred embodiments of the chemical 
refrigeration system 13, as illustrated in FIGS. 2 and 3, the principles 
on which the chemical refrigeration system of the present invention 
operates will be briefly described. The present invention takes advantage 
of the known fact that certain chemicals, when dissolved in water, produce 
an endothermic reaction which will cool the water down to a temperature 
below ambient temperature. The degree of cooling depends on the type of 
chemical used. Applicant has investigated the behavior of several 
chemicals, including ammonium chloride, potassium chloride, potassium 
permangenate, and potassium bromate. More specifically, the behavior of 
these chemicals dissolved in water with respect to the refrigeration 
properties has been examined. The refrigeration properties of these 
chemicals, using ethyl alcohol as a solvent, have also been investigated. 
The results of these tests are illustrated in the following Table I. 
TABLE I 
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CHEMICAL REFRIGERATION 
Examples 
Initial Final 
Temperature 
Temperature 
Chemicals .degree.F. .degree.F. 
______________________________________ 
Ammonium Chloride 
70 48 
40 gms/water 20 ml 
Ammonium Chloride 
68 40 
50 gms/water 100 ml 
Ammonium Chloride 
100 58 
40 gms/water 50 ml 
Ammonium Chloride 
84 48 
40 gms/water 50 ml 
Ammonium Chloride 
92 56 
100 gms/water 300 ml 
Ammonium Chloride 
60 28 
50 gms/water 156 ml 
Ammonium Chloride 
82 46 
80 gms/water 200 ml 
Ammonium Chloride 
52 25 
60 gms/water 150 ml 
Potassium Chloride 
76 50 
15 gms/water 50 ml 
Potassium Chloride 
56 30 
25 gms/water 50 ml 
Potassium Chloride 
76 60 
25 gms/water 50 ml 
Potassium Permangenate 
68 60 
25 gms/water 50 ml 
Potassium Bromate 
68 58 
25 gms/water 50 ml 
Ammonium Chloride 
56 30 
15 gms/water 50 ml 
Ammonium Chloride 
60 40 
15 gms/water 50 ml 
Ammonium Chloride 
71 61 
15 gms/ethanol 50 ml 
Ammonium Chloride 
44 22 
15 gms/water 50 ml 
Ammonium Chloride 
34 11 
10 gms/water 40 ml 
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The results of this Table indicate that on a pound basis, ammonium chloride 
dissolved in water produces the most cooling, followed closely by a 
potassium chloride water system. However, ammonium chloride has been found 
to be somewhat unstable, so potassium chloride is the preferred embodiment 
of the present invention. 
The above Table also illustrates that the amount of cooling obtained is 
proportional to the amount of the chemical dissolved in water, which is 
fixed by the solubility limitations of the chemical. The lower the 
temperature of the liquid into which the chemical is introduced, the lower 
the solubility of the chemical is. This limits the amount of cooling one 
can get at a given temperature, namely the temperature drop or delta. 
For example, to 200 ml. of water at 82.degree. F., 80 grams of ammonium 
chloride was added with very gentle agitation. Within fifteen seconds, the 
temperature of the solution dropped to 46.degree. F. Since an excess 
amount of ammonium chloride was used, undissolved salt settled at the 
bottom of the container. The addition of more ammonium chloride did not 
lower the temperature any further because of the solubility limitations of 
the ammonium chloride. 
In another example, fifty ml. of fresh water at 44.degree. F. was provided, 
and 15 grams of ammonium chloride was added. The solution cooled down to 
22.degree. F. The addition of more ammonium chloride did not lower the 
temperature of the water. 
In another example, to 40 ml. of fresh water at 34.degree. F., ten grams of 
ammonium chloride was added, and the solution cooled down to 11.degree. F. 
The addition of more ammonium chloride did not lower the temperature 
further. 
The results of these experiments show that if one wants to chill water over 
a large delta, for example, from 82.degree. F. to 11.degree. F., this 
cannot be achieved in one stage, but it can be achieved in three stages. 
It is important to note that each stage must chill fresh water for the 
next stage in order to make it possible to achieve this large temperature 
drop or delta. 
An example of a two-stage system is illustrated in the preferred embodiment 
of FIG. 2 of the present invention, which will not be described. The 
chemical refrigeration system of FIG. 2 includes first and second chillers 
14 and 18 connected in tandem to chill water from 80 F. from a source 10 
to 36.degree. F., as output from the system at 24. A first supply of 
potassium chloride is input to the first chiller 14 at 14B, and a second 
supply of potassium chloride is input to the second chiller 18 at 18B. 
Chiller 14 has a reservoir 14R therein, and chiller 18 has a reservoir 18R 
therein. Water is supplied from a source 10 at 80.degree. F. to a heat 
exchanger 12 through inlet 12A. Heat exchanger 12 has another input 12D 
for receiving waste brine or a potassium chloride solution at 
approximately 47.degree. F. via pump P1 holding tank 26, inlet 26A 
thereto, and outlet 14C of chiller 14. Accordingly, it can be seen that 
the waste brine or first cooling solution from within reservoir 14R is 
recirculated and applied to heat exchanger 12 at inlet 12D in order to 
cool the incoming water at 80.degree. F. down to a temperature of 
65.degree. F. at outlet 12C of the heat exchanger. A portion of the waste 
brine is also output at heat exchanger 12 at 12B, and proceeds to a 
recovery station for recycling the potassium chloride. 
Consequently, the water entering the first chiller 14 is at 65.degree. F., 
rather than 80.degree. F., which enables the potassium chloride added at 
14B of chiller 14 to chill the water down 20 to 45.degree. F. A portion of 
the 65 F. water passes directly into chiller 14 at inlet 14A, and another 
portion passes into the input end of a coil 16 which passes through 
reservoir 14R in heat transfer contact with the 45.degree. F. cooling 
solution therein. Therefore, the liquid or water is further chilled from 
65.degree. to 50.degree. in the coil 16, and passes on through inlet 18A 
into the reservoir 18R of chiller 18. A second supply of potassium 
chloride is added to chiller 18 through inlet 18B, chills this 50.degree. 
F. water down to 32.degree. F., creating an even colder cooling solution 
than present in the first chiller 14. The cooling solution in chiller 18 
is recirculated through an output 18C, a pump P2, and an inlet 22C into a 
second heat exchanger 22. Waste brine from heat exchanger 22 is output at 
22B into the holding tank 26 through inlet 26B thereof. Simultaneously, 
water to be chilled at 80.degree. F. is input to heat exchanger 22 through 
inlet 22A, wherein it is cooled down to approximately 50.degree. F. by the 
cooling solution entering heat exchanger 22 from chiller 18. This 
50.degree. F. water exits heat exchanger 22 through outlet 22D, and passes 
through a second cooling coil 20 which is immersed in heat transfer 
contact within reservoir 18R. Accordingly, water exiting or output from 
cooling coil 20 at 24 is refrigerated to a temperature of approximately 
36.degree. F. 
Therefore, it can be seen that the plural stage refrigeration system 
illustrated in FIG. 2 can successfully cool water from an 80 F. first 
temperature to a 36.degree. F. second temperature by means of only two 
chillers, in which first and second supplies of potassium chloride or 
other selected chemicals are introduced. This 36.degree. F. water output 
at 24 could, for example, be introduced into the carbonator 15 of the 
post-mix beverage system of FIG. 1, described hereinbefore. 
Referring to FIG. 3, only one chiller stage is utilized to chill water from 
80.degree. F. down to 36.degree. F. However, in order to achieve this, 
larger heat exchangers and chillers must be utilized than in the 
embodiment of FIG. 1, and, in addition, the cooling solution of the 
chiller must still be recirculated to initially cool the incoming water 
down by means of heat exchanger 32 from an initial temperature of 
80.degree. F. to 50.degree. F. 
As illustrated in FIG. 3, water at a temperature of 80.degree. F. is 
provided by a source 30 into an inlet 32A of a heat exchanger 32, where it 
is coupled in a heat transfer fashion to 32.degree. F. brine input at 
inlet 32D from the output of a pump P3 and outlet 34C of chiller 34. The 
32.degree. F. brine chills the 80.degree. F. water down to a temperature 
of 50.degree. F. at output 32C of heat exchanger 32. Waste brine from the 
heat exchanger 32 may be output at 32B at a temperature of approximately 
72.degree. F. to a recovery station. The recovery station may constitute 
any suitable means for separating the potassium chloride salt from the 
water, such as by gas or solar drying devices. 
The 50.degree. F. water output from heat exchanger 32 has a portion input 
through inlet 34A to reservoir 34R of chiller 34, and another portion 
input to a coil 36 which passes through the cooling solution contained in 
reservoir 34R. Chiller 34 has a supply of potassium chloride supplied 
through inlet 34B, which lowers the temperature of liquid in reservoir 34R 
to a temperature of approximately 32.degree. F. Consequently, when the 
50.degree. F. water passes through coil 36, which is immersed in the 
32.degree. F. cooling solution of reservoir 34R, water is output at 38 at 
a temperature of about 36 F. 
Many variations may be made in the systems of the present invention 
embodied in FIGS. 1 and 2, without departing from the spirit and scope of 
the present invention. For example, the capacities and sizes of the 
respective heat exchangers, chillers, connecting conduits, and so forth, 
may be greatly varied to achieve the degrees of cooling required. Also, 
the flow rates of the liquid between successive stages of the system will 
be controlled in accordance with the size and heat exchange 
characteristics of the various devices. 
In addition, the pumps, such as P1, P2, and P3, of the systems of the 
present invention may be powered by various means, such as electrical 
power or gas power, which may be a biproduct of the carbonation system of 
the post-mix beverage dispenser of FIG. 1. However, if utilized in outer 
space, the pumps P1, P2, P3 are preferably powered with electricity. 
In addition to its use in outer space for providing refrigeration systems, 
the present invention may be utilized in underdeveloped countries for 
providing a low-cost refrigeration system. For example, the chemicals, 
such as potassium chloride utilized in the chillers of the systems of the 
present invention, may be recovered and recycled for repeated use. This 
can provide great cost savings over electrically-powered, mechanical 
refrigeration systems which are conventional in post-mix beverage 
dispenser systems now in use. 
The chemical refrigeration system described hereinbefore may be further 
modified, as would occur to one of ordinary skill in the art, without 
departing from the spirit and scope of the present invention.