Absorption Refrigeration System

Abstract

An absorption refrigeration system employing a secondary refrigerant to transfer heat from a suitable heat exchanger to the system evaporator; pump means to circulate absorbent solution and the secondary refrigerant; and ejectors for increasing pump inlet pressures to prevent refrigerant flashing at the pump inlets.

Description

BACKGROUND OF THE INVENTION

In many applications, for example, air conditioning systems, an absorption refrigeration system is provided with a secondary circuit employing chilled water. The water chilled by the absorption refrigeration machine is circulated to a heat exchanger within the conditioned space, warm air from the space being circulated over the heat exchanger to cool the air for distribution throughout the conditioned space. The warm water from the heat exchanger is returned to the absorption refrigeration machine for transferring the heat therein to the evaporator or chiller of the refrigeration machine.

In certain installations, it may be desirable to utilize a halogenated hydrocarbon refrigerant such as dichlorodifluoromethane in the secondary circuit. Pump means are ordinarily provided to circulate the absorbent solution within the absorption machine circuit and to circulate the chilled water or the halogenated hydrocarbon refrigerant to the heat exchangers within the conditioned space. Under certain circumstances, the pressures at the pump inlets may be below the vapor pressure of the fluid being pumped, resulting in flashing of the fluid and inefficient pump operation.

SUMMARY OF THE INVENTION

This invention relates to an absorption refrigeration system including an absorber, a condenser, an evaporator and a generator connected to provide refrigeration. A heat exchanger is operatively associated with the evaporator for circulation of refrigerant between the evaporator and the heat exchanger. First pump means to transfer solution from the absorber to the generator and second pump means to circulate refrigerant between the evaporator and the heat exchanger are provided. At least one of said pump means is provided with an ejector including nozzle means for discharging a portion of the fluid from the discharge side of the pump associated therewith into the throat of the ejector to maintain pressure at the pump inlet above the vapor pressure of the fluid being pumped to prevent flashing of the fluid at the pump inlet.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram of an absorption refrigeration system including a secondary refrigerant circuit provided with a pump and an ejector for circulating the secondary refrigerant; and

FIG. 2 is a schematic diagram of another embodiment of my invention, wherein pump means including ejectors are provided to circulate secondary refrigerant and to circulate absorbent solution.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 of the drawings, there is shown a refrigeration system comprising an absorber 10, a condenser 12, a chiller 14 and a generator 16 connected to provide refrigeration. A pump 20 is employed to circulate weak absorbent solution from absorber 10 to generator 16.

As used herein the terms "weak solution" or "weak absorbent solution" refer to solution which is weak in absorbent power and the terms "strong solution" or "strong absorbent solution" refer to solution which is strong in absorbent power. A suitable absorbent for use in the system described is water and a suitable refrigerant is ammonia.

Liquid refrigerant condensed in condenser 12 passes through refrigerant liquid passage 22 and refrigerant restrictor 24 to heat exchange tube 26 of liquid suction heat exchanger 27. The liquid refrigerant which is cooled in tube 26 passes through refrigerant restriction 28 into heat exchange coil 30 of chiller 14.

A heat exchange medium such as a halogenated hydrocarbon refrigerant for example, dichlorodifluoromethane, is passed over the exterior of coil 30 where it is chilled by giving up heat to evaporate the refrigerant within heat exchange coil 30.

The chilled heat exchange medium is collected in the lower portion of chiller 14 for subsequent passage through line 32 to a pulser type pump 34. The pump 34 includes a housing 36 having an inlet opening 38 and discharge opening 40. A suction valve 42 is disposed within inlet opening 38 and a discharge valve 44 is disposed within discharge opening 40. A flexible diaphragm 46 is mounted within housing 36. A pulsating flow of hydraulic fluid from a suitable hydraulic pump 48 is provided to the interior of diaphragm 46.

When hydraulic fluid under pressure is supplied to diaphragm 46, the diaphragm is expanded outwardly toward the housing walls. The heat exchange medium in space 50 between the diaphragm and housing is forced through discharge valve 44 into discharge line 52. When the hydraulic pressure within the diaphragm is released, the diaphragm contracts. This allows heat exchange medium to pass through suction valve 42 into space 50. Thus, the pulsing hydraulic pressure in diaphragm 46 causes heat exchange medium to be pumped from line 32 to line 52.

For optimum pump efficiency it is desirable to supply liquid heat exchange medium to pump 34. However, the suction pressure at the pump inlet may be below the vapor pressure of the heat exchange medium which could result in flashing of a portion of the heat exchange medium. The resulting flash gas would reduce pump efficiency. To obviate this problem, an ejector 54 having a throat 56 is provided in line 32 to increase the pressure of the heat exchange medium at the pump inlet. A nozzle 58, disposed adjacent throat 56 is adapted to inject a portion of the heat exchange medium flowing through line 52 into throat 56 to provide a pressure downstream from the ejector sufficient to prevent flashing of the heat exchange medium.

The chilled heat exchange medium passes through line 52 to suitable remote heat exchangers (not shown) after which it is returned to the chiller through line 68.

The refrigerant evaporated in heat exchange coil 30 passes through refrigerant vapor passage 70 of liquid suction heat exchanger 27 in heat exchange relation with liquid refrigerant passing through tube 26. Refrigerant vapor having a small proportion of absorbent liquid therewith passes from passage 70 through line 72 into vapor distributor 74. Strong solution which is supplied from the generator to the vapor distributor 74 through line 76 is discharged into the vapor distributor 74 to induce refrigerant vapor from distributor 74 into tubes 78. The strong solution with the refrigerant vapor therein is supplied to absorber 10 where cooling medium, preferably ambient air is passed over the surface of the absorber in heat exchange relation with the solution therein for cooling the absorbent solution to promote the absorption of the refrigerant vapor by the solution. The same cooling medium may be supplied to condenser 12 in heat exchange relation with refrigerant vapor therein to condense the refrigerant.

Cold weak absorbent solution passes from absorber 10 through a line 80 into weak solution pump 20. Pump 20 may be of the same general design as pump 34, the hydraulic pump 48 being adapted to supply a pulsating flow of hydraulic fluid to pump 20 and pump 34. Liquid from pump 20 passes through pump discharge line 82 to rectifier heat exchange coil 84. The weak solution passes through coil 84 in heat exchange relation with hot strong solution passing through heat exchange coil 86 disposed within coil 84 and with the hot refrigerant vapor flowing through rectifier shell 87 in contact with the outer surface of coil 84. The weak solution from coil 84 is discharged into the upper portion of generator 16 along with any vapor which is formed in coil 84 due to heat exchange with the hot vapor passing thereover and the hot solution flowing therethrough.

Generator 16 comprises a shell 90 having fins 92 suitably affixed thereto as by welding. The generator is heated by a gas burner 94 or other suitable heating means. The weak solution is boiled in generator 16 to concentrate the solution, thereby forming a strong solution and refrigerant vapor.

The hot strong absorbent solution passes upwardly through the analyzer section of generator 16 through analyzer coil 96 in heat exchange with weak solution passing downwardly over the coil. The warm strong solution then passes through heat exchange coil 86 and line 76 into vapor distributor 74. A restrictor 98 is provided in line 76 so that the solution supplied to the vapor distributor is at the same pressure as the vapor in vapor distributor 74.

Refrigerant vapor formed in generator 16 passes upwardly through the analyzer section thereof where it is concentrated by mass heat transfer with weak solution passing downwardly over analyzer coil 96. Analyzer plates 102 in generator 16 provide a tortuous path for flow of solution and vapor, assuring intimate contact therebetween to improve the mass heat transfer. The vapor passes through rectifier 87 in heat exchange relation with the weak solution passing through coil 84. Absorbent condensed in rectifier 87 flows downwardly onto the generator 16. The vapor formed in the generator is a mixture of refrigerant vapor and absorbent vapor. The analyzer plates and rectifier purify the refrigerant vapor by condensing the water or absorbent vapor from the mixture. The purified refrigerant vapor is passed from rectifier 87 through line 104 to condenser 12 to complete the refrigeration cycle.

Referring to FIG. 2 which illustrates a second embodiment of my invention, there is disclosed a system similar to the system illustrated in FIG. 1 with the exception of an ejector 106 associated with pump 20. The ejector 106, having a throat 108 is disposed in line 80 to increase the pressure of the absorbent solution at the pump inlet. A nozzle 110 disposed adjacent throat 108 is adapted to inject a portion of the solution flowing through line 82 into throat 108 to provide a pressure downstream from the ejector sufficient to prevent flashing of the refrigerant in the absorbent solution when the pump inlet pressure is below the vapor pressure of the refrigerant, thereby increasing pump efficiency and preventing noise normally generated by flashing refrigerant.

While I have described a preferred embodiment of my invention, it is to be understood the invention is not limited thereto but may be otherwise embodied within the scope of the following claims.

Claims

I claim:

1. In an absorption refrigeration system including an absorber, a condenser, a chiller and a generator connected to provide refrigeration, apparatus comprising:

pulser type pump means for circulating refrigerant fluid in a refrigeration cycle through said chiller, said pump means having an inlet and a discharge side; and

an ejector for receiving refrigerant fluid and for passing the fluid to said pulser type pump means, said ejector including nozzle means and a throat, said throat leading to the inlet of said pump means and said nozzle means discharging a portion of the refrigerant fluid from the discharge side of said pulser type pump means into the throat of said ejector to maintain pressure at the inlet of said pulser type pump means above the vapor pressure of the refrigerant fluid being pumped to prevent flashing of the fluid at said inlet.

2. Apparatus according to claim 1, wherein said pulser type pump means includes:

a housing;

a diaphragm disposed within said housing; and

means for providing a pulsating supply of hydraulic fluid to one side of said diaphragm for pulsing said diaphragm to circulate the refrigerant fluid in the refrigeration cycle.

3. Apparatus according to claim 1, and further comprising:

pump means for transferring absorbent fluid from said absorber to said generator, said pump means having an inlet and a discharge side; and

a second ejector for receiving absorbent fluid from said absorber and for passing the absorbent fluid to said absorbent fluid pump means, said second ejector including nozzle means and a throat, said throat leading to the inlet of said pump means and said nozzle means discharging a portion of the absorbent fluid from the discharge side of said absorbent fluid pump means into the throat of said second ejector to maintain pressure at the pump inlet above the vapor pressure of the refrigerant in said absorbent fluid to prevent flashing of the refrigerant at the pump inlet.

4. Apparatus according to claim 3 wherein said refrigerant fluid pump means and said absorbent fluid pump means are operable by hydraulic pressure, and said apparatus further includes a hydraulic pump connected to both of said pump means for transmitting the hydraulic pressure for operating each of said pump means.