cham"ber)

A chamber in which the air is artificially cooled, used especially for the storage of perishable provisions during warm weather. refrigerating-machine (re-frij'e-ra-ting-mashen"), shēn"), n. A machine for the artificial production of cold. In such machines mechanical power is employed for the conversion of heat into work by operating upon a gas at a temperature far removed from that at which such gas becomes a liquid. They perform the following cycle of operations: first, the gas is compre ed into a smaller volume, in which compre ion its contained heat is increased by the heat-equivalent of the work performed in the compre ion; secondly, the compre ed gas is cooled under constant pre ure, and thus brought near to the temperature of the cooling medium (usually water), and the increase of heat due to compre ion is re moved; thirdly, the compre ed and cooled gas is permitted to expand, expending a portion of its expansive force in the performance of work. This work having been performed at the expense of the store of heat originally contained in the gas, the latter has now lost the heat-equivalent of the work, and its temperature is greatly lowered. The now cold gas can be used for the refrigeration of any other substance which has a higher temperature by methods described under ice - machine and refrigeration. In other machines a gas or vapor the ordinary temperature of which is near to that at which it liquefies is compre ed and cooled, and subsequently permitted to a ume the gaseous form. By the compre ion the temperature of liquefaction is raised till it becomes the same as or a little higher than that of a conveniently available cooling medium, such as ordinary atmospheric air, or, most commonly, water at ordinary temperature, the application of which to cooling the gas still under constant pre ure reduces it to the liquid state, or to a state of intermixed liquid and gas. The subsequent expansion of the liquid into gas is performed at the expense of its inner heat. It therefore suffers a reduction of temperature, to restore which it absorbs its latent heat of vaporization from a surrounding or contiguous substance (usually a saline solution), which, thus made cold, is used for cooling air-spaces, or refrigerators or substances therein contained, or for making ice. Machines of either of the above cla es are very commonly called ice machines, and are so styled in the cla ifications of inventions in both the United States and British patent-offices, whether designed for the manufacture of ice, for merely cooling substances in insulated spaces or refrigerators, or for both these purposes.