CHAPTER VIII HOUSEHOLD REFRIGERATING MACHINES (Part 3)

that no desirable control could be de'eloped for controlling water simultaneously with the gas and that any water control developed would have to be designed using as a ccmtroUing factor a predetermined cooling water outlet temperature. Such a device was developed and with the outlet water temperature maintained at 90° F. the water consumption was practicalh' halved as compared to that which was used prior to the de- velopment of this water control. The machine is now operat- ing satisfactorily with about three gallons of water per hour with water inlet temperature of 70° F. The machine will oper- ate and produce ample refrigerating effect with cooling water up to 90° F. With temperatures above this, the water would flow through unrestricted parts in the \ah-e and the \alve be- come unnecessary, but where cooling water is encountered below 90° F. the saving in water is very material. Those familiar with early tests must realize the material saving made in the water consumption and that the objections raised to water cooling, both as to waste of water and costs has been overcome. The machine unit comprising the generator, evaporator, absorber, rectifier and gas heat exchanger is made of heavy steel tubing inter-connected by steel pipes, all joints being 318 HOUSEHOLD REFRIGERATION uxy-acelyline welded. This produces a completely sealed unit from which there is no danger of leakage. The units are de- signed to withstand a pressure of 3100 pounds per square inch although only about 200 pounds charging pressure is used, and a certain proportion of the run of units are tested to this pressure at the factory. Each unit, however, is subjected to a high pressure test in order to detect any possible imperfec- tions in welding. From time to time one hears many stories reflecting on the safety of gas-fired absorption machines. This all emanated from experiences of ten to fifteen years ago when a few gas- fired intermittent absorption machines were being marketed, most of them of large capacity for commercial use. A few serious accidents practically eliminated further progress in this type of machine, and produced adverse legislation. The cause of this trouble was largely due to a lack of understanding as to the necessary safety devices that are required on a large in- termittent machine. In other words, a machine of this kind requires automatic mechanism to shut off the fuel at the end of the boiling period, to apply cooling water at the right time both for condensing and absorbing purposes, and a pressure limiting device in the event that the gas fuel or condensing water did not function properly. The fact is these variously needed devices had not been properly perfected before the machines were marketed. Since that time there has been con- siderable progress made in small intermittent machines, so that in some cases for certain types of work the objections of the past have as a rule been overcome. The Electrolux-Servel unit incorporates features which make safety devices not only unnecessary but undesirable. The fuel burns continuously, and continued operation of the maximum burner adjustment would merely produce an ex- tremely cold box. In practice this is prevented by making the gas consumption depend upon box temperature. If, for any reason, the cooling water were to fail nothing would happen other than that the refrigeration would cease. The reason that no safety device is required to meet this condi- tion is due to the design of the machine, which provides so much radiating surface, in proportion to the heating surface, ABSORPTION REFRIGERATING MACHINES 319 that all parts, with the exception of the generator will throw off the heat as fast as it is applied, through all the surfaces as represented by the evaporator, heat exchanger, absorber, condenser and rectifier, and a state of equilibrium will be reached when these surfaces will throw ofif the heat at the same rate as heat is applied to the generator. These two features absolutely eliminate the need of any safety devices whatsoever for the purpose of safe operation. For an entirely different reason, however, a fusible plug is installed on the absorber end of the gas heat exchanger. This w^as made at the suggestion of the New York Fire De- partment, as well as the National Board of Fire Underwriters, and is to provide for that emergency which would be brought about by intense exterior heat being applied to all parts of the machine as would be the case if a fire occurred in the room in which the refrigerator were installed. To meet this emergency the fusible plug set to melt at 200° F. would simply relieve the refrigerator charge. This is a precaution which would be just as important if the machine were simply tilled with either water or air, as the unlimited heat supply would simply produce an internal pressure which would event- ually rupture the machine. These facts are borne out by the approval of the machine by the National Board of Fire Under- writers' Laboratory in Chicago, and by recent changes in the proposed code for the city of New York. This machine has long since passed its experimental stage. When first brought out into production 250 sample boxes were sold to the various gas and public utility companies for the purpose of having them conduct tests and determine if the machine and box w-ere what they desired and what was claimed it would do. Apparently the machine and boxes de- signed met with instant approval as is evidenced by the large order placed for this machine. The machine lends itself to and is particularly suitable for apartment house service espe- cially in large and congested cities where the fact that it is absolutely noiseless, safe and serviceless has been deciding factors in its reception. The unit may also be used in specially built boxes of vary- ing sizes, built to fit into particular niches as seems to be the growing demand in new apartment house construction. There 320 HOUSEHOLD REFRIGERATION is also a combination of a gas stove and refrigerator where a gas stove is mounted on a refrigerator box the same gas service line serving both. There are operating right now in the Eastern districts embracing environment of Metropolitan district of New York approximately one thousand machines. The servicing of these machines, in case it were necessary, would, of course, be done b- the gas company, and from the information received the' advise that so far they ha'e not experienced any servicing whatsoever. One question has undoubtedly occurred to a good many of you. "What effect has the gas flame with its products of combustion on the interior of the gas flue which passes through the generator?" In view of the fact that the gas flame is not extinguished but ranges in degrees from IJ/^ cubic feet per hour to 3 cubic feet per hour results in the gas flue always being kept at a temperature higher than the dew point. Numerous people have asked the question, "What corro- sion will take place within the unit?" Before the unit is charged with ammonia, distilled water and hydrogen, a high vacuum is pumped. Practically all oxygen is therefore re- moved. The machine, of course, has not been in service more than a few years so we can go back no further — but machines that have operated for this length of time in Sweden have l)een cut open and no trace of corrosion has been found. The dissociation of ammonia into nitrogen and hydrogen is an old story in absorption systems where numerous joints and connections are used. In the Platen-Munters Refrigerat- ing unit — there are no joints, no possibilities of air leakages. Then, too, if there should be a tendency to break down the ammonia into nitrogen and hydrogen — -it must be remem- bered that the unit has already a heavy charge of hydrogen and this would tend to repel the dissociation. Another question that has apparently been causing some comment by refrigerating engineers has been the possibility of leakage of hydrogen through the steel. As long ago as about 1860 it became known that hydrogen is absorbed by certain metals and can be diffused through them. This matter has since this time been subject to a large number of investi- gations which have mostly centered on the diffusion of hydro- ABSORPTION REFRIGERATING MACHINES 321 gen through iron and steel, as this for several reasons is of considerable technical interest. It was known from these investigations that gaseous hydrogen easily penetrates and diffuses into steel at red heat. This diffusion, however, is sharply reduced with the lowering of the temperature and has seldom been observed at a tem- perature below 300° C or 572° F., wherefore some investi- gators have assumed a discontinuity of the diffusion at this temperature, or a "hydrogen point" of the steel. On the other hand it was shown that hydrogen which had been introduced into the steel electrolytically would diffuse through the metal at even room temperature. As the Platen-Munters refrigerating unit contains hydro- gen at ordinary room temperature under relatively high pres- sure, it was desired to determine if any appreciable loss of hvdrogen would occur under these conditions. Earlier inves- tigations had indicated that the losses would be quite small, but as no figures were available regarding their actual mag- nitude, tests were arranged and conducted by Professors Borelius and Lindblom at the Royal Technical School at Stockholm. Applying the data obtained to the Platen-Munters refrig- erating unit, we find that no danger exists of loss of hydrogen through the wall of the apparatus. For instance, if we take a 60 cal. refrigerator which contains 1.5 gr. hydrogen and which will still operate if 0.3 gr. of this hydrogen were lost, we would find that it would take one hundred eighty years before sufficient hydrogen escaped making the apparatus in- operative. This certainly gives a wide margin of life. Thousands of people have examined this machine, among them a large number of engineers ; in fact, generally speaking, the more technical a person is, the greater appeal has been made by the machine. The fact that the machine is noiseless, free from moving parts, compact, economical in operation and has apparently unlimited life, cannot but make us reflect on its effect on domestic refrigeration. When we consider that this machine is the first of its kind, and if we compare it with other developments in the past, we can readily visualize that the continuous absorption machine will also follow in the path of progress. 322 HOUSEHOLD REFRIGERATION Does this not make us wonder if the absorption principle will not soon be a vital factor in domestic refrigeration? (From an address delivered by F. E. Sellmann at the Ameri- can Society of Refrigerating Engineers meeting in May, 1927.) l-IG. 166.— ELECTROLUX SERVEL KEFRIGKRATOR CABINET. Fig. 166 shows the refrigerator cabinet. The exterior is made of lead coated steel finished with white duco. Fig. 167 shows the cooling unit and food compartment space. The food capacity is 6^^ cubic feet. The box is insulated with three inches of corkboard. The lining is of porcelain and the cooling section is of cast aluminum having five trays with a capacity of fifty cubes of ice. ABSORPTION REFRIGERATING MACHINES 323 Fig. 168 shows the machine mounted on the side of the cabinet. The water control valve is mounted on an outlet water line. The purpose of the water control is to throttle FIG. 167.— SHOWING COOLI.N'G UNIT AND FOOD COMl'ARTMENT SPACE. the water used in the condenser so as to maintain a constant outlet temperature under all conditions of inlet temperature and pressure. The gas thermostat automatically regulates the supply of gas responsive to the temperature of the food compartment. 324 HOUSEHOLD REFRIGERATION A safety gas burner is used so that the gas supply is auto- matically shut off if for any reason the gas flame is ex- tinguished. FIG. 168.- -SHOWING ELECTROLUX SERVEL MACHINE MOUNTED ON SIDE OF CABINET. ABSORPTION REFRIGERATING MACHINES 325 Sorco Gas Absorption Refrigerator. — The new Sorco Gas Absorption Refrigerator (Figs. 169 and 170) which is manu- factured by the Gas Refrigeration Corporation, with sales office at 18 East 41st Street, New York City, has a great num- IIG. 169.— SORCO GAS ABSORPTION REFRIGERATOR. ber of new features not shown in their old construction de- scribed heretofore. The boiler absorber contains a solution of auiuionia and water. As cold water attracts and absorbs or dissolves am- monia, the rate at which it does so and the amount it absorbs depend on the temperature of the absorbent. On the other 326 HOUSEHOLD REFRIGERATION hand, hot water repels ammonia in the form of a gas. Hence during the heating period, ammonia is liberated from the boiler, liquefied in the condenser and fills the evaporator. Dur- ing the refrigerating or absorbing period of the cycle which FIG. 170.— SUKCO GAS ABSUKPTIOX UNIT INSTALLED IX REFRIGERATOR. may last from eight (8) to se'enteen (17) hours, according to the required amount of cold, the liquid anhydrous ammonia gasifies from the evaporator and returns to the boiler absorber where it is reabsorbed by the weak liquor. The heat absorbed by the evaporating ammonia as well as the heat of association generated by the absorption of the ammonia gas in the weak ABSORPTION REFRIGERATING MACHINES 327 liquor in the boiler absorber are carried off by the cooling water. The patented construction and design of the Sorco Boiler Absorber are extremely simple as it contains no moving parts such as valves of any kind, floats, by-passes, packing or stuff- ing boxes or anything that can possibly get out of order. In all intermittent absorption machines ammonia gas must be ex- pelled from the top of the liquid level and re-absorbed under- neath the surface of the liquid. We accomplish this by an application of gas heat to the boiler as well as the absorber, at which time an over pressure is created in the absorber dur- ing the boiling period which keeps the aqua ammonia floating in the boiler compartment until a predetermined maximum is reached in the boiler when the required amount of ammonia gas is expelled to the condenser. Shortly after the beginning of the absorption period the remaining weak liquor in the boiler flows back to the absorber to a lower pressure created by the cooling water flow which is diverted through the absorber at the same time the heat is turned off. A number of novel patented features are embodied in the Evaporator construction. As shown in the diagram attached, there is no moveable part in the ammonia system which is hermetically sealed in steel vessels and seamless steel tubing welded to the tanks. As the same pressure exists during the boiling period in all parts of the evaporator a great part of the ammonia would condense in the cold evaporator which would warm it up so that the food compartments and the ice in the evaporator would melt. Condensation in the evaporator is reduced to a minimum in the construction shown. The first entering fluid ammonia fills above the coils. Condensation cannot take place in the coils as they never become empty. Condensation must then first take place in the evaporator in the reduced surface area inside the main upper vessel which quickly increases the temperature of this vessel at the begin- ning of the heating period. But as soon as the temperature of this main vessel reaches a certain temperature slightly above the cooling water temperature, condensation stops there auto- matically. This is due to the fact that only a small part of 328 HOUSEHOLD REFRIGERATION the latent heat can escape through the air insulation between the main vessel and the housing of the evaporator. Conden- sation thereafter takes place only in the condenser. The evap- orator housing remains unaffected by this heat which cannot circulate. The ice evaporator is able to make six (6) pounds of ice in form of 72 ice cubes, within the short time of two to three hours. There is alwavs a small amount of moisture in the dis- tilled ammonia when it enters the evaporator during the heat- ing period. This moisture not only has the tendency to in- crease the boiling point of the ammonia in the evnporator, thereby preventing the e\ aporator from reaching its minimum possible temperature, but it also would gradually accumulate in the evaporator because it does not evaporate back in the boiler absorber with the evaporating ammonia. The amount of moisture generally increases with increasing cooling water temperature and has to be removed automatically. The Sorco evaporator is equipped with a marvelously operating patented return suction tube cup which has no moveable part and is based on two functions. First, a continuously separating op- eration, and, second, a removing operation. The first one is performed by the ice tray supporting coils in combination with the vertical tube during the whole absorption period. The lower ends of these coils are over orifices in communica- tion with the vertical tube, so that liquid circulation between the vertical tube and the two coils is avoided. At the start of the boiling period the remaining aqueous solution in the vertical tube and in the lower part of the coils is forced through an orifice into the sump at the bottom of the evap- orator. Due to the drop in pressure shortly after the end of the boiling period a small predetermined amount of liquid in the tube cup is drawn back into the absorber. This takes place shortly after the end of each boiling period with an astonishing regularity and without returning an appreciable amount of ammonia. The Sorco is now as formerly 100 per cent automatical}} operated. The attractive feature, however, is that electricity is no longer required to operate the control of the gas heated unit. The movement of the few parts in the patented control ABSORPTION REFRIGERATING MACHINES .^29 is