CHAPTER VIII HOUSEHOLD REFRIGERATING MACHINES (Part 1)

CHAPTER VIII HOUSEHOLD REFRIGERATING MACHINES ABSORPTION TYPE Household Absorption Refrigerating Machines. — In this chapter, attention will be given to the general types and char- actertistic construction of a number of household absorption refrigerating machines. Ice-O-Lator. — Fig. 162 shows an absorption type refriger- ating machine manufactured by the Winchester Repeating Arms Company for the National Refrigerating Company at New Haven, Conn. The "absorbent" which was the result of so many years of research by Prof. Keyes is the basis of the machine. Other absorbents have been known. Charcoal is an efficient absorb- ent and is frequently employed to absorb gases of various kinds. A good example is in gas masks. But charcoal can- not be employed in refrigeration because it is such a poor con- ductor of heat that no practical degree of efficiency can be obtained in the operation of a machine using it. You can get the gas into it well enough, but you can't get it out again without the expenditure of a prohibitive amount of energy. This absorbent combines the highest known absorbing quali- ties together with the quality of high heat conductivity. Following are the qualities which the inventors set out to embody in their absorbent. They are the properties of an ideal material : 1. Cheapness and unlimited supply. 2. Should absorb at least 100 per cent of its own weight of re- frigerant. 299 300 HOUSEHOLD REFRIGERATION 3. Should ha\ c :i lii,L;li heat coiuluctivity in urder to facilitate the removal of heat of absorption and also the application of heat for driving off the refrigerant. 4. Cellular, or porous structure, in order to present necessary working surface. 5. Stability. There should be no diminution of operating effi- ciency, or no disintegration or decomposition after continued use. ^ I FIG. 162.— XATIONAL UEFRIGEUATINC MACHINE. In three >ears of contintiotis oiieration. no si^n of decreased efficiency has developed. A brief comparison with water, the best known absorbent, forms a favorable basis for com])arison. Water rom])els the ABSORPTION REFRIGERATING MACHINES 301 use of aqueous ammonia. This material is absolutely dr, making" possilile the use of pure anhydrous ammonia. Water absorbs 40 per cent of its own weight of ammonia. This material absorbs a])i)r(jximately 110 per cent of its own weight of ammonia gas and in addition loses its working charge on the application of about half the amount of heat necessary to dri-e the much smaller charge from water. Result — much less bulk and much more economical operation. As the efficiency of the material has been steadily increased by constant scientific research since its discovery, there is con- siderable possibility th.it it may be still further increased. The small hcjusehold machine operates as follows: A steel tube is filled with a material which will absorb a large quantity of ammonia gas. When heat is applied the pressure is in- creased and the NH, gas is liberated and passes through a filter and check vahe to the condenser. When the pressure reaches a point that corresponds to the temperature of the cooling water, condensation takes place and liquid NH3 is de- livered to the liquid valve float chamber. The purpose of this chamber is to insure complete condensation by the cooling water. The liquid NH, is then delivered through a small orifice and tube to the refrigerating chamber and coils. The heating continues until enough liquid NH3 has collected in the re- frigerating chamber and coils to make a contact by means of the float contacting mechanism at the top of the refrigerating chamber. \Mien this contact is made the relay switching sys- tem is tipped to the opi)osite position, the heating circuit is broken, and the water is shifted by means of the valve from the condenser to the generator. As soon as the pressure over the material in the generator has dropped to the point which is less than the vapor pressure of the liquid ammonia in the refrigerating chamber and coils, boiling in this chamber com- mences and continues until all the liquid has evaporated. This evaporation may require from one hour to five hours depend- ing upon the temperature in the refrigerator. A'hen the tem- perature is high, the evaporation is very rapid and when it is low the boiling requires a much longer period of time. The temperature in the refrigerator, then is regulated by the rate of evaporation of the liquid. The brine tank maintains the 302 HOUSEHOLD REFRIGERATION low temperature during- the heat i)eriod when no refrigeration is taking place so that the temperature ;n the refrigerator is practically constant. When the entire quantity of liquid has evaporated a contact is made at the bottom of the refrigerating chamber which tips the relay to the heating position, the heat- ing circuit is made, the water is shifted back to the condenser, and the cycle repeats. Fig. 163 shows a diagramatic drawing of the gas-fired Ice- O-Lator. This model has electrical controls and is water- tifTTfOiinrr rp^euiAM^fif '"'" "■"* """ BtlT- B,,.,. -r;: <• v.lrt i/^rrfi/ r« (ifMfTar (fupr««c SlAm v<. Ovrtir -flt««'<7r rPv FIG. 163.— DIAGRAMMATIC DRAWING OF THE GAS-FIRED ICE-O-LATOK. cooled. The unit is placed in the cellar or any convenient place outside of the refrigerator cabinet. The following information concerning the cost of operating this unit is of interest. Illuminating or coal gas delivers 520 B.t.u. per cubic foot and natural gas an average of 1100 B.t.u. per cubic foot. One kw-hr. of electricity at 110 volts delivers 3415 B.t.u. Taking coal gas for comparison, 6.56 cu. ft. of gas is equivalent to one kw-hr. of electricity for heating purposes. The cost of gas per 1000 cu ft. ranges from $0.40 to $1.50 in various localities. Many cities have a rate under $1.00. ABSORPTION REFRIGERATING MACHINES 303 Natural gas, with about double the B.t.u. of coal gas, can be purchased for as low as $0.40 per 1000 cu. ft. in some localities As against this, the cost of electricity averages about $0.55 per kw-hr. Heat for heat, the difference will readily be seen. At $1.00 per thousand cu. ft. for coal gas the same number of B.t.u. can be obtained for three-fifths of a cent as from five and one half cents' worth of electricity at the above rate. The following table shows the approximate cost of opera- tion, for the equivalent of 100 lbs. of ice refrigeration, of a machine using gas at the various rates. Cost of Gas Per Cost Per 100 Lbs. 1000 Cu. Ft. of Refrigeration $0.40 $0.05 .80 10 1.00 125 1.50 187 2.00 25 2.80 35 It will probably have been observed that the small house- hold machine is cyclic and subject to peaks. Whereas this has not proven an objection in any of the machines at present in operation, still in the event that continuous refrigeration should be desired to meet some special conditions, such can easily be obtained by the use of two generators, one absorb- ing while the other distills. Keith. — Fig. 164 shows an ammonia absorption type house- hold refrigerating machine made by the Keith Electric Re- frigerator Division of the Canada Wire and Cable Company, Ltd., at Leaside, Ontario, Canada. Referring to Fig. 164, which shows the unit in the cooling position, on the left hand side in the generator, is about two quarts of ordinary "ammonia" as used in the home. Within the tank there is also a small electric heater. When the heater is started the gas is driven out of the water, just as you can see gas or bubbles of air driven out of the water in your tea kettle as it begins to boil. This gas is not very warm, as ammonia is easily driven ofif, and when it flows over into the pipes shown on the right hand of the illustration, it is chilled by a trickle of cold water which is flowing over the pipes of 304 HOUSEHOLD REFRIGERATION the cc)n{len>er. W hen it is chillt'd, the gas is deposited on the inside of the condenser, about the same as dew is deposited by the chill of the morninci: air. This dejiosit is pure liquid am- monia. When the condenser is nearly full of pure liquid ammonia, in approximately one hour's time, it ])egins to weigh more than the generator, and swings down, ])ulling the generator ui) and shutting off the electric heater. Almost immediately the pure licpiid ammonia ])egins to c\a])orate and chills the FTC. 164. —KEITH ..\l M ( ).\ 1 .\ .M'.SORl'l'lO.X lYI'E KK KKICK k.ATI .( i MACHINE. pipes to apj^roximately zero temperature. This chills the sur- rounding air, which flows do\n into the food comi)artment of the refrigerator. As the pure liquid ammonia evaporates, it flows l)ack as a gas into the tank of water, where it is once more cjuickly absorbed. As soon as all the ammonia is returned to the generator, the pipes of the condenser naturallx" become lighter and the tank (or generator) heavier, and the unit gently tilts back to the original position, the electric heater starts and the operation commences all over again. ABSORPTION REFRIGERATING MACHINES 305 The u])crati()n, as has been cxphiined is inircl) automatic, requiring no attention and maintains an even cold tt'm])eraturc at all times, ideal for the jM-eservation of food. The amount of electrical energy consumed axerages about 3^/2 kilowatt hours per da}' for continuous ojjeration, depending on the weather and other conditions. FIG. K. 5.— KEITH REFRIGERATING UNIT INST.\LLED IN COMP.XR'l MEN 1 OX CABINET. Heater — 900 watt resistance coil, porcelain core, inserted in steel tube through generator. Ice lock — Holds the condenser down until all ammonia is in the generator. Is released by temperature rising above freezing point. Tip switch — A safety device tf> disconnect the electricity should the water be shut off. 306 HOUSEHOLD REFRIGERATION Mercury seal — Contains mercury, which runs to lowest point with the tilting of the unit opening and closing the ammonia pipe to condenser. Dehydrator — Eliminates water vapor from ammonia gas as it rises to the condenser. The cabinet, Fig. 165, shows a complete self-contained unit with the machine in the compartment at the top. Master. — An absorption machine of simple design is made by the Master Domestic Refrigerating Company, Inc., at Flushing, N. Y. It comprises a cylindrical generator, water cooled condenser and evaporator, connected by a single pipe to form the complete machine. It is made entirely from steel pipe and sheet steel. Only water and ammonia are used as the means of produc- ing refrigeration. These substances are charged in the gen- erator in the correct proportions. Ammonia in the form of gas is released by applying heat to the generator. The gas is then cooled and liquefied in the condenser from which it flows by gravit} to the evaporator in the cooling compartment of the refrigerator. By the subsequent cooling of the gener- ator a reduction in tlie pressure is produced and the ammonia slowly evaporates thus producing the required refrigeration. The gas is re-absorbed by the cooled water in the generator. When the evaporation of the ammonia is practically completed a new cycle automatically begins. The necessary reduction of the pressure is attained solely by the cooling of the generator, no check, float, or expansion valve, restricted orifice or other device is used in the machine and the pressure is always the same at any given time in all parts of the machine. The generator, condenser and evapora- tor freely communicate with each other at all times with pipe of full orifice. The machine requires no attention as it is completely auto- matic. The automatic control consists of a power element actuated by the temperature of the generator, and a further power element which is placed in contact with the evaporator. The cooperation of these two power elements, by means of a simple mechanical principle, which is novel in its application to this machine, regulates and establishes the heating and cool- ABSORPTION REFRIGERATING MACHINES 307 ing" periods and assures the proper and continual functioning of the machine in a simple and positive maner. Should for any reason the supply of water to the condenser be interrupted, the heating means is automatically 'cut ofif. Simple and effective means are provided for automatically returning to the generator any water which may be carried over by the ammonia gas to the evaporator. The machine and refrigerator are built as a complete self- contained unit, but, if desired, the machine may be installed outside of the refrigerator. Defrosting of the evaporator is automatic. Provision is made for an ample supply of ice cubes for table use. The present machine is used to cool refrigerators of any size up to eight cubic feet inside capacity. The Electrolux Servel. — The first practical continuous operating absorption refrigerating machine was made about the year 1860 by a Frenchman named Carre. His apparatus consisted first of a source of heat, generator, condenser cool- ing water, expansion valves, evaporator, absorber and pump. The heat liberated the ammonia gas from the aqua ammonia, so called "rich solution or strong liquid" leaving a weak liquid or water in the generator. The gas passing to the condenser is cooled off by the cooling water and condensed into a liquid. The liquid ammonia flows through the throttle or expansion valve into the evaporator, where the liquid ammonia is vapor- ized into a gas. During the evaporation heat is withdrawn from the surroundings, and thus cold is produced. The cold vapor passes into the absorber where it is sprayed by weak liquid from the generator. By the expulsion of the ammonia from the aqua-ammonia solution in the generator, the remain- ing liquid is to a large extent water. This poor solution be- ing exposed to the high pressure passes through an expansion valve into the absorber. In this way the poor solution,- meet- ing the ammonia vapors, absorbs them, so that in the bottom of the absorber a mixture collects as a "rich or strong solu- tion." This solution is continually forced into the generator by the pump, which is operated by outside mechanical forces. A line drawn from the expansion valves t! rough the pump 308 HOUSEHOLD REFRIGERATION separates the machine into a liigh pressure side and a low pressure side. In the apparatus of Carre's there are two cycles. The ammonia circulates from the generator through the condenser, the vaporizer and the absorber l)ack to the generator. It therefore passes through all four recei)tacles. The water cir- culates from the generator to the abs<,)rber and vice versa. The water therefore only passes through these two receptacles. The Carre machine was built in great numbers, being used in breweries, distilleries and similar ])lants where large amounts of heat vapor was available for vvliich at that time no particular use was made. However as the steam technique further developed and afforded numerous uses for exhaust steam for other purpv)ses, the employment of the ab>ori)tion machine became less and less. This was further augmented b}' the high efficiency of the newdy develo])ed compressor system. Meclianical difficul- ties also played a role as with small units as were used, the expansion valves were necessaril}- small and the orifice wa> <:ontinualh' clogging uj) with dirt ; then tcjo the ])um])s were d source of constant maintenance and had to be operated by auxiliar}- power, independent of this source of heat used in evaporating the aqua-ammonia. There therefore arose a demand for small continually oper- ating absorption machines, from which the above said defects of the machine of Carre were eliminated, said machines to have neither expansion \alves nor pump, but which could be oi)er- ated merel}" by the heat supply. This was the aim of Geppert. In order to reach this aim he dispensed with the difference of the total pressure for the ]>ur])ose of \apori/cation. W'itli the same total pressure in the entire apparatus he tried to effect the vaporization neces- sary for refrigeration, as well as the reuniting of the ammonia gases with the w^ater, and returning the mixture to the boiler without a pump or other mechanical energy. To this end, Geppert, in adition to the cooling medium (ammonia) and the absorbing liquid (water) used in the vaporizer a third medium, to wit. a gas. in the presence of wdiich according to physical laws (due to tlie difference of so called partial pressures of ABSORPTION REFRIGERATING MACHINES oU9 the gases) liquid ainnionia exajjorates without a (h'op of the total pressure being required. In the year 1899, Geppert built such an ap]>aratus. In the boiler the ammonia gas is expelled as in tlie Carre machine. After being liquihed in the condenser the licpiid ammonia flows through a conduit into the upper pan of the evaporator. In this liquid is immersed a porous material which is so placed as to extend over the rim of the inner o])ening and extend- ing completely under the pan. The porous material with its large exposed surface facilitates the evaporation of ammonia in the presence of the second gas contained in the receptacle. The second gas used by Geppert was air. At a slight distance below the porous pad on the bottom of the upper pan is a bath of poor solution, whicli flows fr(jm the boiler, being cooled by passing through a cooler on its way to the absorber. It will thus be seen that Geppert combined the eva])orator and absorber into one vessel. The ammonia gases resulting from the evaporation at the surface of the porous material difl:use> downward through the second gas filling the receptacle and is then absorbed by the absorption liquid. The rich liquid then flows back to the generator where l)y the a])])lication of heat ammonia gas is again expelled. The machine of Geppert is based on the theoreticall}' cor- rect idea that a pressure drop requiring throttle valves and pump becomes unnecessary in a refrigerating machine, if in the evaporator the lic^uid ammonia meets with a gas