The refrigerating apparatus which we illustrate herewith is the invention of two young Swedish engineers, Messrs. B. de Platen and C. Munters. It works on the ammonia evaporation principle, and is continuous in its action. Its distinguishing feature is the fact that it embodies no moving elements whatsoever, no motor, fan, valve or other mechanical operat ing device forming part of its construction. For the present the system embodied in the invention is being applied to refrigerating apparatus of a small size suitable for domestic and similar use, such as the preservation of food, but, we understand, its application on a larger basis is only a matter of time. The energy required to operate the apparatus is supplied either by a small gas burner, an electrical heating unit, exhaust steam or other convenient source of heat. As supplied by the makers the apparatus is charged under pressure with distilled water, ammonia and hydrogen, and as all the pipes and vessels are connected by welding these substances remain in use an indefinitely long time. Beyond the supply of heat nothing father is required except a circulation of cooling water.

In all continuously operating refrigerating systems there are of necessity a portion of the apparatus under relatively low pressure and another under relatively high pressure. In the ammonia evaporation system the refrigerating effect is produced by the evaporation of the ammonia in the low-pressure part. In the high-pressure portion the ammonia is condensed and the cycle is then repeated. The circulation of the working fluid between the two portions necessarilyinvolves the expenditure of energy, which hitherto has generally been supplied by a motor or other mechanical source of power. Moreover, between the high and the low-pressure portions some form of valve has hitherto been required to effect and regulate the reduction of pressure. In the " Electrolux " refrigerator the circulation is 1 effected on the thermo-syphon principle, while the reducing valve is eliminated by an ingenious application of Dalton's law of gaseous pressures. Dalton's law, it will be recalled, states that the total pressure of a mixture of gases inside a vessel is equal to the sum of the partial pressures of the separate gases : that is to say, the sum of the pressures which the gases in the mixture would exert if they were separately caused to occupy the vessel.

Fig. 176.

In the " Electrolux "refrigerator the pressure on the ammonia in the high-pressure portion of the apparatus may be of the order of 180 lb. per square inch, while in the low-pressure portion the pressure required to effect evaporation may be 30 lb. or thereabouts. The reduction of pressure is effected by introducing into the low-pressure portion hydrogen in such volume and at such pressure as to give a partial pressure of 150 lb. in the hydrogen and a partial pressure of 30 lb. in the ammonia. The hydrogen is removed from the ammonia before the ammonia circulates back into the high-pressure portion. The effective reduction of pressure on the ammonia of 180 lb. to 30 lb., is thus secured without the use of anything in the nature of a valve, and the total pressure throughout the apparatus is constant at 180 lb. Other inert gases besides hydrogen might be used, but hydrogen has been chosen because its lightness greatly assists the required circulation. Not only does the introduction of the hydrogen effect the required reduction of effective pressure on the ammonia ; the fact that it results in the total pressure being virtually uniform throughout the apparatus reduces the energy required to effect the circulation and indeed makes practicable the use of a simple thermo-syphon system for achieving such circulation.

Fig. 177.

The apparatus as shown in the diagram-Fig. 177-and in the more complete drawing given in Fig. 176, comprises three chambers, known as the generator, the absorber, and the evaporator. The evaporator is placed inside the chamber to be cooled. The generator is heated by a gas, electric, or other unit, and. with the absorber, is placed outside the chamber.

Inside the generator there is a mixture of ammonia and water. When this mixture is heated the ammonia is driven off and, ascending upwards, passes through a water-cooled condenser in which the gas is liquified. Any water vapour passing off with the ammonia is condensed in an air-cooled rectifier, which, as indicated in Fig. 176. is so arranged that the condensed water flows back into the generator, and does not mingle with the liquefied ammonia. Reaching the evaporator the liquefied ammonia falls on to a series of baffles on which it evaporates under the partial pressure t o which it is subjected as a result of an inflow of hydrogen into the evaporator from the absorber. In so evaporating the ammonia draws its latent heat I from the space surrounding the evaporator, which space may comprise a chamber filled with brine. The hydrogen enters the evaporator at the top. The mixture of ammonia gas and hydrogen, being heavier than the pure hydrogen, falls to the bottom and leaves the evaporator by way of a pipe which conducts it to the absorber. In the absorber it meets a spray of water-actually weakly ammoni-acal-which is received from the generator, and which falls over a series of baffles. In this water the ammonia is dissolved. The hydrogen in the mixture being insoluble escapes upwards to the top of the absorber and re-enters the evaporator.

The strong ammoniacal liquid formed in the absorber leaves that vessel by a pipe at the foot and flows through a heat exchanger working on the counter-current principle In this exchanger the strong liquid flowing from the absorber is heated, and the weak liquid or water flowing to the absorber is cooled. After emerging from the-heat exchanger the strong liquid flows through a coil surrounding the heating unit of the generator. The heating of the strong liquid causes the liberation of gas bubbles from it, which lift the liquid upward until it is delivered into the generator at a point near the top of that vessel. The inflow of strong liquid into the generator maintains a hydrostatic head sufficient to cause the liquid freed from some or all of its dissolved gas to flow out of the generator through the heat exchanger and into the absorber, where it once again takes up ammonia and becomes strong liquid. The arrangement constitutes a pump operated, without moving parts, by the direct application of heat to the liquid pumped. In order to promote the solution of the ammonia in the weak liquid or water the absorber is provided with a jacket through which the cooling water is passed on its way to the condenser.

The parts occupy but a small space in the interior, and do not project far on the outside. The brine tank surrounding the evaporator inside the refrigerator extends into both the compartments into which the refrigerator is divided. In the lower compartment the tank is furnished with trays, which, when filled with water, enable a supply of pure ice to be obtained. In the remainder of the refrigerator space the temperature maintained is sufficient for the preservation of food stuffs, but is not necessarily below the freezing point. It is understood, however, that if required the temperature preserved in the refrigerator can be arranged to be as low as 1 deg. Fah.

In the electrically heated form of the apparatus, the type which we have inspected, an arrangement is provided whereby, should the supply of cooling water fail, a mercury contact switch comes automatically into action and cuts off the heating current. The consumption of the apparatus as made for domestic use is, we understand, about 3 cubic feet of gas, or 1/4 Board of Trade unit per hour, and 5 to 6 gallons of water in the same time. (The Engineer.)