similar in construction to that shown in section in Fig. 167. R is the steam engine cylinder. B is the pipe through which the gas is drawn from the evaporating coils into the compressor A. The gas is then discharged by the action of the compressor through the pipe C, into the pressure tank D, where the sealing oil or liquid falls to the bottom. Suitable cast-iron baffle plates are fitted in the upper portion of the pressure tank, which serve to retain the oil, and insure its deposition. From the pressure tank D the gas which still retains the heat due to compression, passes through pipe E into the bottom or lower pipe of the condenser F, wherein, by the cooling action of cold water running over the pipes, the heated gas is first cooled and then liquefied. The ammonia, in this liquid condition, is then led by the small liquid pipes. G, through the liquid header II, into the storage tank 1, from whence it flows through the pipe J into the lower part of the separating tank K, which latter must be constantly maintained at the very least three-quarters full. L is a pipe of small bore, through which the liquid ammonia is forced, by reason of the pressure to which it is now subjected, to the expansion cock or valve, through which it is injected into the evaporating or expansion coil N which is situated in the room or chamber to be refrigerated or cooled.

The ammonia gas resulting from the expansion and evaporation of the liquid ammonia in the evaporating or expansion coil N, having absorbed or taken up the heat from the surrounding atmosphere, passes away through the pipes o and в, back again into the compressor cylinder, and the cycle of operations of compressing, etc., are again performed as above.

Secondly. Following the course of the oil employed

for sealing, lubricating, and cooling purposes, which, as previously mentioned, is heated with the gas during compression, and is passed into the tank D, to the bottom of which it falls. From the bottom of the tank D, the heated oil is conducted through a pipe a to the lowermost pipe of the oil-cooler b, which is practically similar in construction, but on a smaller scale, to the ammonia condenser, and is likewise cooled by sprayed or atomized cold water. After being sufficiently reduced in temperature in the oil-cooler b, the oil flows through the pipe c, strainer d, and pipe e, into the oil pump f, which latter Is so constructed that it delivers the cooled oil into the compressor, distributing it to either side of the piston or plunger during its compression stroke, that is to say, in such a manner that no oil is furnished during the suction stroke of the piston, but only during the time of compressing, thereby cooling the gas during its period of heating. The heated oil, after leaving the compressor, then again returns, together with the hot compressed gas, to the pressure tank D, and follows the same round through the oil-cooler b, strainer d, and oil pump f, back to the compression cylinder. It will be obvious that the oil, as well as the ammonia, is used over and over again, no loss or waste of either taking place except that which may occur through leakage.

Any small quantities of oil, however, that may be carried over with the current of the gas from the pressure tank into the condenser F, pass along with the liquid. ammonia into the separating tank K, where, by reason of its greater weight, this oil falls to, and collects at the bottom of the tank. As soon as a sufficient quantity of oil has become thus deposited, it is drawn off, and passed through the oil cooler back to the oil pump. The oil

reservoir or tank is also connected to the oil pump F. When the apparatus is employed for the manufacture of ice, the evaporating coils N are placed in a tank containing brine, sufficient space being left between them to allow of the insertion of cans or moulds containing the water to be frozen. As before stated the exhaust steam of the engine driving the compressor is condensed and purified, and supplies the water to be made into ice.

∞

FIGURE 169.

Diagram from De Lavergne Compressor.

The various parts are clearly indicated in Fig. 168and the routes taken by the ammonia, the sealing oil, the lubricating and cooling oil, and the steam are shown by the arrows.

Fig. 170 is a sectional view of the Triumph Ice Machine Company, Cincinnati, O., horizontal pattern double-acting ammonia compressor. It will be seen from the illustration that the compressor is provided with five valves, viz., three suction valves and two discharge

valves, the third, or auxiliary suction valve, being much lighter than the main valves, and perfectly balanced, and it being claimed by the makers tending greatly to increase the economy of the machine.

Obviously the main suction valves must necessarily be of sufficient dimensions to admit the charge quickly at the commencement of each stroke, and the springs con

trolling them must consequently have an appreciable tension. It will be readily seen that owing to this fact the pressure of the gas in the cylinder, during admission, must be less than it is in the suction pipe by an amount equal to the tension of these springs. By the use of the above mentioned third, or auxiliary suction valve, which is comparatively light, and is consequently operated with a very light spring, the pressures in the compressor pump

are equalised, and a fuller charge is obtained at each stroke, thereby increasing the efficiency of the machine.

The valves comprise each a guard screwed on to the stem, fitted inside a cage, and so ribbed as to reduce the port area, the bottom of the stem being enlarged for that reason. Stems extending from both the suction and discharge valves to the exterior, and passing through stuffing boxes, admit of their being adjusted from the outside, and any desired degree of tension being put upon the springs. The object of this arrangement is to adjust the machine for working at different pressures, and the relative temperatures thereof.

There are three packing compartments in the pistonrod stuffing box, and it is fitted with a suitable relief valve communicating with the suction. The heads are formed concave, and of a radius which enables a larger valve area to be secured. The principal shut-off valves are of such a form of construction as to admit of their being packed whilst the machine is working, and a feature in the design of this machine which is of by no means inconsiderable advantage, is that every portion of the compressor is easily accessible.

Besides ammonia, there are various other refrigerating agents employed in the compression system, among which may be mentioned Ether, Methyl-chloride, sulphurous acid, and carbonic acid, but space will not permit a further discussion of the compression system, and the absorption process will now be taken up.

The principie involved in the operation of apparatus for the abstraction of heat by the evaporation of a separate refrigerating agent of a volatile nature under the direct action of heat, and without the use of power, which agent again enters into solution with a liquid, is,