Refrigeration – Refrigeration producer – Compressor-condenser-evaporator circuit
Reexamination Certificate
2000-12-26
2002-10-22
Doerrler, William C. (Department: 3744)
Refrigeration
Refrigeration producer
Compressor-condenser-evaporator circuit
C062S513000
Reexamination Certificate
active
06467303
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to vapor compression refrigeration systems and, more specifically, to the use of passive desuperheating of the gaseous refrigerant used in the refrigeration system.
BACKGROUND OF THE INVENTION
The field of vapor compression refrigeration systems includes refrigeration systems and air conditioners. Prior art closed vapor compression refrigeration systems utilize a cycle wherein the liquid refrigerant vaporizes to produce useful cooling, and where the following steps are used: (1) expansion of the liquid refrigerant (pressure reduction); (2) vaporization of the expanded liquid refrigerant in an evaporator to produce useful cooling (the refrigerant absorbs heat in this step); (3) compression of the gaseous refrigerant to form a compressed gaseous refrigerant (the refrigerant absorbs further heat in this step); and (4) condensation of the gas to condense the gaseous refrigerant back into a cool liquid refrigerant. The above steps are driven by the energy used to drive the compressor. Some prior art devices also include a reservoir, for the purpose of storing the cooled liquid refrigerant. Some prior art devices also require the use of oil to lubricate the compressor and therefore also require the use of oil separators to remove oil from the refrigerant, thus reducing contamination of the refrigeration system.
The refrigerant can absorb heat at various points in the refrigeration cycle, where the result is superheating. Superheating is the heating of vapor to a temperature much higher than the boiling point at the existing pressure. Superheating is also defined as the condition where the temperature of a vapor is greater than the saturation temperature corresponding to its pressure (Dossat, R. J. (1997) Principles of Refrigeration, 4
th
ed., Prentice-Hall International, Inc., p. 108, 120-123). Heat is initially absorbed in the evaporator. The vaporized refrigerant can continue to absorb heat before it reaches the compressor. Further heat is absorbed by the refrigerant during compression, such that superheated gaseous refrigerant is produced. Superheating in a refrigeration system has a number of adverse consequences, as revealed below.
Adverse Effects of Superheated Gas and Advantages of Desuperheating.
One adverse consequence of superheated gas is that contact of the superheated gas with a water-cooled condenser can result in excessive heating of the water within the condenser, with consequent undesirable deposit of scale (scaling). Water used in the condenser normally contains calcium bicarbonate, which is water-soluble. However, excess heating provokes the conversion of the calcium bicarbonate to calcium carbonate, which forms a water-insoluble deposit in the condenser (Demko et al, U.S. Pat. No. 5,509,462, issued Apr. 23, 1996; Pauling, L. (1970) General Chemistry, Dover Publications, N.Y., p. 504).
Another adverse consequence of passage of superheated gas through the refrigeration system is that it results in excessive expansion of the gaseous refrigerant. The result of this excessive expansion is that the compressor must compress a correspondingly greater volume of gas during passage of the refrigerant through the system (Dossat, R. J. (1997) Principles of Refrigeration, 4
th
ed., Prentice-Hall International, Inc., p. 120). A result of this need for an increased amount of compression is the utilization of extra power (Stoecker, W. F. (1998) Industrial Refrigeration Handbook, McGraw-Hill, New York, p. 72).
Oil from the compressor can mix with the refrigerant, resulting in the drawing of oil throughout the system, and in undesirable oil deposits in the condenser and evaporator. Oil in the evaporator can cause considerable loss of evaporator efficiency (Dossat, R. J. (1997) Principles of Refrigeration, 4
th
ed., Prentice-Hall International, Inc., p. 322-323). Another undesirable effect is loss and depletion of oil in the compressor. The undesirable effects of contaminating oil can be prevented by means of an oil separator. Oil separators are described below. Separation of the oil from the gaseous refrigerant is difficult when the mixture is relatively hot, but is easier when the mixture is relatively cool. Hence, a desupetheater can be used to cool the hot discharge gas at or prior to the position where the hot discharge gas enters the oil separator.
A further disadvantage of introducing superheated gas into the condenser is that it can result in inefficient wetting of the surface of the condenser, with consequent inefficient heat transfer (U.S. Pat. No. 1,946,328 issued to J. Neff). Hence, an advantage of desuperheating is more efficient heat transfer in the condenser.
In summary, desuperheating of hot discharge gas, prior to contact with parts of the refrigeration system downstream of the compressor might be expected to solve a number of problems, including: (1) scaling as a result of hot discharge gas in a watercooled condenser; (2) expansion of gas with the consequent need for excess power consumption due to extra work performed by the compressor, (3) utilization of heat, derived from a desuperheater, to improve the performance of oil separation devices, and (4) more efficient heat transfer in the condenser.
Desuperheaters
Some prior art desuperheaters use steam, while others describe desuperheaters that use refrigerant.
U.S. Pat. No. 4,454,720 issued to H. M. Leibowitz describes a heat pump for recovering energy from waste fluid, wherein a desuperheater sprays atomized liquid water into a flow of superheated steam.
U.S. Pat. No. 5,041,246 issued to F. E. Garrison describes a venturi for use in desuperheating in a steam generator.
U.S. Pat. No. 3,343,375 issued to L. K. Quick describes a desuperheater wherein only a portion of the superheated hot discharge gas is desuperheated. The superheated gas that leaves the compressor at output 12 and sent through line 71 is desuperheated, but the portion leaving at output 12 and sent through line 13 is not desuperheated.
U.S. Pat. No. 4,311,498 issued to D. K. Miller describes a desuperheater wherein hot discharge gas is desuperheated by coils 32 containing mechanically circulated water.
U.S. Pat. No. 5,336,451 issued to J. M. Lovick relates to the desuperheating of steam by the injection of cool water.
U.S. Pat. No. 1,946,328 issued to J. Neff describes a desuperheater for a refrigeration system wherein the desuperheater comprises a pump for actively driving cool liquid refrigerant to be used for desuperheating purposes.
U.S. Pat. No. 4,554,799 issued to F. T. Pallanch relates to the problem of compressing gaseous refrigerant, where the gas is expanded to such a great degree that multiple compressors are needed. A desuperheater is placed in the line between two successive compressors in order to improve the efficiency of the second compressor. Cool liquid refrigerant is not mixed with the superheated gas. Instead, cooling is by means of a heat exchanger. The preferred mode of delivery of the cool liquid refrigerant is a mechanical pump.
U.S. Pat. No. 4,311,498 issued to D. K. Miller describes a refrigeration system having a desuperheater positioned between the compressor and condenser, where the desuperheater is comprised of a line 34 containing circulating cold water (column 3, lines 34-36). The water appears to be circulated by means of a mechanical pump.
U.S. Pat. No. 5,150,580 issued to R. E. Hyde describes a desuperheater wherein cool liquid refrigerant leaving the condenser is actively injected into the condenser with a mechanical pump (column 6, lines 61-63). Desuperheating occurs in the condenser, and not in any portion of a line upstream to the condenser (column 6, lines 66-69).
U.S. Pat. No. 4,419,865 issued to P. G. Szymaszek describes a desuperheater wherein cool liquid refrigerant leaving the condenser is actively injected at a point in between the compressor and an oil separator using a pump 22 and motor 23.
U.S. Pat. No. 5,097,677 issued to M. T. Holtzapple describes a desuperheater where cool liquid refrigerant is introduced into the compressor, rather than at a
Coudert Brothers LLP
Doerrler William C.
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