US1968908A - Refrigeration - Google Patents

Description

Aug. 7, 1934. F. D. PELTIER Er AL 1,968,908

REFRIGERATION Filed Nov. 20. 1930 V I 7 I a lgfj IN E 0R8. izh/c, xvi

A TTORNEY Patented Aug 7, 1934 UNITED STATES PATENT OFFICE I REFRIGERATION Application November 20, 1930, Serial No. 496,888

3 Claims.

This invention relates to refrigerating systems of the compression type and more particularly to a means for returning lubricant from the evaporator to the compressor.

5 In some refrigerating systems lubrication of the compressor is accomplished by circulating a socalled working fluid which consists of a mixture of refrigerant and lubricant. In other refrigerating systems a separate source of lubricant is provided for the compressor but some of the lubricant mixes with the compressed refrigerant and passes through the condenser into the evaporator. Due to the relatively less volatile nature of lubricents as compared to refrigerants the latter pass from the evaporator back to the compressor through the vapor suction line while the lubricant remains in the evaporator. In time the accumulation of lubricant in the evaporator will seriously impair the efliciency of the systems, wherefore in both of these systems it is necessary to provide some means for returning the lubricant from the evaporator to the compressor. A very convenient method of doing this is to introduce the lubricant from the evaporator into the vapor suction line where it is drawn with the refrigerant vapor back to the compressor.

An object of this invention is to provide a simple but positive means for effecting the transfer of lubricant from the fluid accumulation in an evaporator of the flooded type into the vapor suction line More .specifically this invention contemplates the use of a capillary device as, for instance, a wick for transferring lubricant from the evaporator into the vapor suction line.

Further objects and advantages will be appar ent from the following description taken in connection with the accompanying drawing wherein:

Fig. 1 is a vertical section of an evaporator hav- .ing a lubricant return means in accordance with this invention; and a Fig. 2 is a section on the line 2-2 in Figure 1. Referring to the drawing an evaporator of. .the flooded type has a refrigerant inlet line 11 and a vapor suction or return line 12. The liquid level in the evaporator is maintained substantially constant by any well known means such as a valve 13 in the refrigerant inlet line which valve is operated responsive to the liquid level by a float 14 through hell crank 15.

If the lubricant used for the compressor is not 'soluble in the liquid refrigerant, it will stratify and float either above or below the surface of the latter in the evaporator. depending upon the difference in specific gravity between the lubricant v 5 .and the refrigerant. The vapor suction line 12 to the compressor extends into the evaporator 10 above the liquid level therein to remove vapor of refrigerant which has evaporated due to the decrease in pressure created by the suction of the compressor, and the absorption of heat from the 0 surrounding medium. Within the evaporator a wick 16 is positioned with one end extending into the vapor suction line and the other end depending into the fluid accumulation. The portion of the vapor suction line into which the wick is ex- 65 tended is enlarged, preferably at the end 1'? of the line in order to compensate for the vapor flow area occupied by the portion of the wick extended into the line.

If the lubricant is of such a character that the fluid accumulation in the evaporator stratifies, the depending portion of the wick may be extended into the lubricant stratum and substantially pure lubricant will be raised by capillary attraction through the wick and into the vapor suction line where it will be scrubbed into the vaporized refrigerant flowing therein. If the lubricant is of such a character that it tends to combine with the refrigerant into a uniform mixture, the wick will raise both lubricant and refrigerant by capillary attraction, but due to the increased surface presented by the wick and the pressure reduction-created by the refrigerant vapor flowing past the portion of the wick in the vapor suction line, the liquid refrigerant rising through the wick will be vaporized leaving substantially pure lubricant to be scrubbed into the refrigerant vapor stream in the vapor suction line. If any unevaporated refrigerant is carried into the vapor suction line it will be vaporized before reaching the compressor.

The wick constitutes a capillary siphon of which the leg extending into the suction line is shorter than the leg depending into the liquid Y accumulation in the evaporator. Ordinarily such 5 an arrangement would be inoperative to transfer liquid by siphonic action. However, there is a pressure difference between the legs of the wick corresponding to the difference in velocity of the vapor in the evaporator and in the suction line when the compressor is in operation. It will be understood that this pressure difference must be at least slightly greater in eflect than the difference in the length of the two legs of the siphon in orderfor the transfer of liquid to mplace through the wick. In some instances it they be necessary 'or advisable to provide a flow restrie tion such as an orifice or venturi in the suction line in order to produce the requisite difference in pressure. This depends of course upon the relative displacement of the compressor and also the height of the suction tube above the liquid level which latter factor determines the difference in lengths of the two legs of the siphon.

When the compressor is not operating, any fluid raised by the wick will not be carried over to the compressor but that portion of the raised liquid which is not evaporated will drain back into the evaporator from the open end of the vapor suction line.

It will be obvious to those skilled in the art that various other changes may be made in the construction and arrangement without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawing and described in the specification but only as indicated in the appended claims.

We claim:

1. In a refrigerating system of the compression type, an evaporator of the flooded type, means for maintaining a substantially constant liquid level within said evaporator, a vapor suction line extending into said evaporator above the normal liquid level therein, the end of said vapor suction line within the evaporator being enlarged, and a wick extended directly into the enlarged portion of said vapor suction line and depending below the normal liquid level in said evaporator.

2. In combination, an evaporator of the flooded type, a liquid refrigerant supply line connected to said evaporator, means in said supply line for maintaining a substantially constant liquid level within said evaporator, a vapor suction line extending into said evaporator above the normal liquid level therein, the end of said suction line within the evaporator being slightly enlarged above the liquid level, and a wick having one end extending directly into the enlarged portion of said vapor suction line and the other end depending below the normal liquid level in said evaporator.

3. In combination, an evaporator of the flooded type, a liquid refrigerant supply line connected to said evaporator, means for maintaining a substantially constant liquid level in said evaporator, a vapor suction line extending into the evaporator above the normal liquid level therein. said suction line having an enlargement above the liquid level in the evaporator and a capillary device having one end extending directly into and obstructing said enlargement and its other end extending downwardly into the liquid accumulation in the evaporator.

CLYDE E. PLOEGER. FRANK D. PELTIER.

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