US2172239A - Noncondensable gas purger - Google Patents

Description

Sept. 5,1939. J. H. CATHER NONCONDENSABLE GAS PURGER Filed Aug. 18, 1937 INVENTOR.

Howard C 0 Mel Jay Wm. WM MW 5 ATTO .5"

Patented Sept. 5, 1939 v UNITED STATES PATENT OFFICE NONCONDENSABLE GAS BURGER Jay Howard Gather, Rochester, N. Y., assignor to Eastman Kodak Company,

Rochester,

The present invention relates to a non-condensable gas purger for mechanical refrigerating systems and more particularly to a purger wherein the non-condensable gases are exhausted from the lower portion of the purge tank.

Although many various and sundry types of The primary object of the present invention' is the provision of a non-condensable gas purger wherein the gases to be purged are withdrawn from the lower portion of the-purger.

Another object of the invention is the condensation of ammonia gases within the purger and/or the location of a cooling means within the purger tank so that the gases rich in noncondensable gas move to the lower portion of 20 the purge tank.

Other and further objects of the invention will be suggested to those skilled in the art by the description which follows. I

The above and other objects of the invention 25 are attained within a non-condensable gas purger which comprises a closed pressure structure, an inlet means for introducing a mixture of gaseous refrigerant and non-condensable gases into the purger, a cooling means for condensing the '30 gaseous refrigerant whereby a'mixture rich in non-condensable gases forms in the bottom of the purger, a gas outlet means extending from the lower portion of the purger, and a liquid refrigerant drainage means for withdrawing the -5 condensed refrigerant from the tank.

Although the disclosure herein willbe related with respect to the use of anhydrous ammonia as a refrigerant, it is to be understood that any of the well known refrigerants, such as carbon 40 dioxide, sulfur dioxide or commercialized compounds of these refrigerants with other ingredients, etc., may be used. The present disclosure will also describe specifically the function of the purger in a compression type refrigerating sys- 45 tem although it is contemplated that the purger could be used directly or easily adapted for use in an absorption type of refrigerating system.

Reference is hereby made to the accompanying drawing, the single figure of which illustrates 50' the application of my improved non-condensable gas purger to a refrigerating system.

It is well known that the non-condensable gases, particularly in a compression type of refrigerating system,'have a tendency to collect is in the upper regions of the condensers and in the upper portions of the receivers. A group of condensers l0 receive gaseous refrigerant from a compressor, not shown, through the gas main H. The condensers III are coolecbin the conventional way, that is, by passing cooling water over them and the condensed refrigerant is conducted from the condensers l0 into a receiver l2 by a pipe connection B. The liquid refrig erant is withdrawn from the receiver 12 through a discharge line ll and is expanded through an expansion valve l5 to produce refrigeration in the brine coolers or other heat-exchange apparatus.

The non-condensable gas purger comprises a closed pressure container or tank l6 having a head l1 and a bottom wall l8 secured to opposite ends thereof. A gas inlet means is connected to the purger and may comprise a series of connections llextending from condensers l0 and connected to a pipe line 20, and may also comprise a gas line 2| extending from the upper portion of receiver I! through a second gas line 22 and a valve 23, through head I1 and into the upper portion of the closed pressure container it. Obviously, any of the connections I9, 20 25 or 2| could be provided with valves to control the flow of. gas therethrough. Furthermore, it

' will be understood that the pressure of the mixture of gases, including gaseous refrigerant and non-condensable gases, within the tank IE will be equal to the head pressure or pressures within condensers I0 and receiver l2 subject to a slight or negligible pressure drop due to friction in the connections between these apparatus. A safety valve 23' is connected to the upper portion of tank 16 in the customary manner.

It will be understood by those skilled in purging refrigerating systems that the mixture of gases passing through the gas inlet means will. be composed principally of gaseous refrigerant 40 and only a relatively small proportion of noncondensable gases. For this reason it is not feasible or economical to purge directly from the condensers "I or receiver l2 and the purpose of a purger is toreduce the proportions of gaseous refrigerant in the purged gases in the interest of safety and economy.

A cooling means is associated with the tank I6 for cooling the gases therein to condense the ant discharge line All and which is connected at its exhaust side by a pipe lineZl to some point in the system, such as beyond the expansion valve 05. The temperature maintained in the purger by such a cooling means will depend on the amount of expansion of the refrigerant permitted or to the pressure or vacuum at the exhaust side of the cooling coil to which pipe line 2? is connected. For ordinary ice making the cooling means may maintain the gases within the purger at about 20 F. but in systems operating with a vacuum on the suction side of the compressor, this temperature may be as low 'as -40 F.

Assuming a head pressure of 150 pounds gauge in the condensers i and receiver l2 and that the liquid therein is at a temperature of 80.6 F., it

' will be found that there is about pounds excess pressure or partial pressure for the noncondensable gases in the mixture being conducted from the condensers and receiver to the purge tank It. Assuming further that the cooling means or cooling coil 2d maintains a temperature of 20 F. within tank 16, thevgaseous ammonia .will be condensed until there is a partial pressure for the ammonia gas of 48.2 pounds per square inch absolute. Since the absolute pressure in the purge tank is 164.7 pounds per square inch, it is found by subtraction of the ammonia partial pressure of 48.2 pounds per square inch absolute that the partial pressure of the non-condensable gases is 116.5 pounds per square inch absolute. The weight of a cubic foot of air under the conditions assumed upon entry of the gaseous mixture into the purger was about .05 pound, whereas, at the same time and under the same conditions a cubic foot of ammonia gas weighs .51 pound. After condensation of the ammonia and alteration in the-partial pressure relationship thereby, the weight of a cubic foot of air at 20 F. and under a pressure of 116.5 pounds per square inch absolute is .65 pound, while the gaseous ammonia at 20 1". and under a pressure of 48.2 pounds per square 'inch absolute is .17 pound per cubic foot. Thus, it will be seen, as already recognized in the art, that by condensation-of the gaseous ammonia the remaining mixture of non-condensable gases which are prin-' cipally composed of air, is heavier and will gravitate to the lower portion of the purge tank l6.

This movement of "the gaseous mixture rich in air, toward the lower portion of the purger caused by the increase in density due to the above mentioned cooling and condensing, may be supplemented by this same cooling and condensing action of the cooling coil which reduces the volume of the gases and creates a region of lower pressure which draws the gases downwardly in the purger toward the cooling coil. As a result of either or both of the aforementioned effects, the lower portion of the purger contains the mixture which is richest in non-condensable gases and leanest in the remaining gaseous ammonia, the richness of non-condensable gases depending upon the cooling effect of the cooling coil 2d.

The condensed refrigerant or anhydrous liquid ammonia is withdrawn from the purger through a liquid discharge means. Such liquid discharge .means may comprise a pipe line 28 connected through the bottom wall- [8 of container It and connected to a trap 29. A valve 30 is operated by a float 3| and is connected by a pipe line 32 to pipe line 21 for returning the salvaged ammonia from trap 29 to the system. ,In other words, when the condensed refrigerant increases the amazes level in trap-29 beyonda predetermined setting drains through pipe 32 into pipe line 21.

A. gas outlet means is arranged for the discharge of the gaseous mixture rich in non-condensable' gases from the lower portion of the container 56. An outlet 33 with a downwardly curved end 3% extends through the bottom wall 88 of container HE. A discharge control means for said gas outlet means may comprise a valve 35 connected to outlet 33. v The non-condensable gases are conducted from thevalve 35 in the usual manner such as by pipe 36 into a volume of water within a container 31. Since the gases being exhausted are under pressure, it is merely necessary to slightly open valve 35 and the gaseous mixture.

known to collect, such as the tops of the con-. densers and receivers. These gases are extremely rich in gaseous refrigerant and are introduced into the tank l8, preferably at thetop thereof. The cooling means or cooling coil 24 condenses the majority of the gaseous refrigerant and reduces the partial pressure thereof in the lower portion of the tank with complementary increase in partial pressure of the non-condensable gases and enrichment of the mixture in the bottom of the tank in said non-condensable .gases. The cooling coil expansion valve 26 is regulated to effect the aforementioned cooling and change of partial pressures to an extent which is both economical and efficient. Those skilled in the art will readily understand that the economy of a purger may be entirely offset by excessive use of work or energy in the expansion of a large volume the purger shall be maintained.

The condensed refrigerant is drained from the tank through the pipe line 28, trap 29, floatoperated valve 30 and pipe 32 for return to the system. The exhaust valve 35 in the gas outlet means maybe set to maintain equilibrium in the exhaust oi the gases rich in non-condensable gases to correspond/to the amount of non-condensable gases being introduced into thesystem. Such a setting will permit continuous operation of the purger although it is understood that the purger may also be intermittently operated at low excess head pressures, or as conditions warrant. The characteristic crackling of ammonia gas bubbling through water will. assist the oper-- it. Otherwise, condensed refrigerant might be discharged through the gas outlet means and crating system, comprising a closed pressure container, a gas inlet means connected to said container for withdrawing from said system and introducing into said container under pressure a mixture of gaseous refrigerant and non-condensable gases, a cooling means associated with said container for cooling the gases therein to condense gaseous refrigerant and decrease the proportion thereof in said mixture whereby the gaseous mixture in the lower portion of said container is richer in non-condensable gases, a noncondensing gas outlet means with an intake opening in the lower portion of'said container for discharging the gaseous mixture rich in noncondensable gases from said lower portion of the container, and a liquid discharge means for withdrawing the liquefied refrigerant from the container.

2. A non-condensable gas purger for a refrigerating system; comprising a closed pressure container, a gas inlet means connected to said container for withdrawing from said system and introducing into said container under pressure a mixture of gaseous refrigerant and non-condensable gases, a cooling means within said container for cooling the gases therein to condense gas.-

eous refrigerant and decrease the proportion.

crating system, comprising a closed pressure container, a gas inlet means connected to said container for withdrawing from said system and introducing into said container under pressure a mixture of gaseous refrigerant and non-condensable gases, a cooling means located only in the lower portion of said container for cooling the gases therein to condense gaseous refrigerant and decrease the proportion thereof in said mixture whereby the gaseous mixture richer in non-condensable gases is drawn into the lower portion of said container, a non-condensing gas outlet means with an intake opening in the lower portion of said container for discharging the gaseous mixture rich in non-condensable gases from said lower portion of the container,. and a liquid discharge means for withdrawing the liquefied refrigerant from the container.

4. A non-condensable gas purger for a refrigerating system, comprising a closed pressure container, a gas inlet means connected to said container for withdrawing from said system and introducing into said container under pressure a mixture of gaseous refrigerant and non-condensable gases, a cooling means associated with said container for cooling the gases therein to condense gaseous refrigerant and decrease the proportion thereof in said mixture whereby the gaseous mixture in the lower portion of, said container is richer in non-condensable gases, a noncondensing gas outlet means with an intake opening in the lower portion of said container for discharging the gaseous mixture rich in non-condensable gases from said lower portion of the container, a discharge control means connected to said gas outlet means for varying the rate of gas discharge to the atmosphere and adjustable to maintain such rate .of gas discharge equal to the rate of formation of the mixture richer in non-condensable gases for continuous operation-

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