KR20100080552A - Non-vacuum absorption refrigeration - Google Patents

Abstract

A non-vacuum absorption refrigeration system is disclosed that operates at ambient pressure using membrane distillation to perform evaporator, absorber and boiler and condenser functions, The absence of a vacuum enables the use of low-pressure, non-corrosive piping and vessels that obviate the maintenance requirements associated with vessels and piping that are susceptible to corrosion and also reduces total system weight.

Description

NON-VACUUM ABSORPTION REFRIGERATION

The present invention relates generally to the field of absorption refrigeration. More specifically, the present invention relates to an absorption refrigeration system using membrane distillation to perform evaporator, absorber and concentrator functions without requiring vacuum.

The basic absorption cycle employs a refrigerant and an absorbent. Typically, water is used as the refrigerant and lithium bromide / water solution (LiBr / H ₂ O) is used as the absorbent. These fluids separate and recombine during the absorption cycle.

In the absorption cycle, refrigerant vapor is absorbed into the absorbent, thereby releasing a large amount of heat. The concentration of the diluted (dilute) absorbent solution may be at least 55% by weight. The dilute absorbent solution is pumped into the hot boiler. The heat applied causes refrigerant in the dilute absorbent to be released from the absorbent and evaporated. The steam flows to a condenser where heat is released and condenses into a liquid. The liquid is metered into the low pressure section in the evaporator, where the liquid is evaporated by absorbing heat to provide useful cooling. The residual liquid absorbent in the boiler may be recombined with the refrigerant vapor returned from the evaporator and the cycle may be repeated.

The absorption process is operated under high vacuum. For example, a vacuum of 0.85 kPa (6.35 mmHg), corresponding to the saturated vapor pressure of water at 5 ° C. (41 ° F.), is used in the evaporator / absorber section. A vacuum of 10.2 kPa (76.2 mmHg), corresponding to the saturated condensation pressure of water at 46 ° C (115 ° F), is used in the boiler and condenser sections. These two sub-ambient pressures should be used to maintain an absorption cycle with a design in the form of a boiler / condenser and an evaporator / absorber.

Since the evaporator / absorber and boiler / condenser sections are operated in a vacuum, they require a high pressure and hermetic design. Thick metal walls are needed to withstand the external pressure on the vessel section. However, the absorbent solution is quite corrosive to metals. Inhibitor chemicals are used to control corrosion. Periodic chemical analysis of alkaline and inhibitor drug concentrations in the absorbent solution is required to maintain normal operation of the absorption chiller.

The inventors have found that it would be desirable to have an absorption refrigeration system operated without vacuum using membrane distillation to perform evaporator and absorber and boiler and condenser functions. The absence of a vacuum enables the use of low pressure, low cost corrosion resistant tubing and vessels, which reduces the maintenance requirements associated with corrosion sensitive vessels and tubing. The use of corrosion resistant materials such as plastics also reduces the total system weight.

A non-vacuum absorption refrigeration system according to one aspect of the present invention cools a refrigerant fluid to generate refrigerant vapor, carries an absorption solution to absorb refrigerant vapor, thereby producing a refrigerant-absorbing (dilute) solution. A membrane contactor (evaporator / absorber); A membrane contactor (concentrator) which removes the refrigerant from the dilute solution and thereby provides a concentrated absorbent solution for the membrane contactor (evaporator / absorber).

In another aspect of the non-vacuum absorption refrigeration system, non-corrosive materials are used for system piping and vessel construction.

In another embodiment of the non-vacuum absorption refrigeration system, the membrane contactor (evaporator / absorber) and the membrane contactor (concentrator) are used for direct contact membrane distillation, air gap membrane distillation, sweep gas membrane distillation and vacuum membrane distillation. It is designed and operated for including membrane distillation.

In another aspect of the non-vacuum absorption refrigeration system, the membrane contactor comprises a microporous membrane having a hydrophobic inner and outer surface.

In another embodiment of the non-vacuum absorption refrigeration system, the pore size and hydrophobicity are such that the absorbent solution and refrigerant do not penetrate the membrane pores.

In another embodiment of the non-vacuum absorption refrigeration system, the thermal efficiency (η _A ) of the membrane contactor (evaporator / absorber) is greater than 50%.

Another aspect of the invention provides a method for non-vacuum absorption refrigeration. A method according to this aspect of the invention comprises the steps of adding a refrigerant to a refrigerant fluid flow; Circulating a concentrated absorbent solution and refrigerant fluid flow through a membrane contactor (evaporator / absorber); Generating refrigerant vapor in the membrane contactor (evaporator / absorber) to cool the refrigerant fluid flow; Absorbing the refrigerant vapor thereby producing a refrigerant-absorbing (dilute) solution; Circulating the dilute solution and refrigerant through a membrane contactor (concentrator); Generating refrigerant vapor from the dilute solution in a membrane contactor (concentrator); Absorbing refrigerant vapor into the refrigerant; Providing a concentrated absorbent solution for the membrane contactor (evaporator / absorber) and cooling the solution.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

1 is an exemplary absorption refrigeration machine.
2 is an exemplary non-vacuum absorption refrigeration system using membrane distillation.
3 is an exemplary microporous membrane contactor.
4 is a cross-sectional view of vapor exchange taking place within the porous hydrophobic polymer membrane wall.
5 is a micrograph of a single microporous membrane cross section in a partial tube-envelope evaporator / absorber device with different fibers.
FIG. 6 is a micrograph of a cross section of the wall of the similar microporous membrane shown in FIG. 5.

Embodiments of the present invention will be described with reference to the accompanying drawings, wherein like reference numerals designate like elements throughout the drawings. Before embodiments of the present invention are described in detail, it should be understood that the present invention is not limited in its application to the details of examples described in the following detailed description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various applications and in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including", "comprising" or "having" and derivatives thereof herein is intended to encompass the items listed thereafter and their equivalents and additional items. The terms "mounted", "connected" and "coupled" are used in a broad sense and encompass both direct and indirect mounting, connection and coupling. In addition, “connected” and “coupled” are not limited to physical or mechanical connections or couplings.

As background, absorption refrigeration is a different process than compression refrigeration. Absorption processes use heat as driving force instead of power or shaft power.

1 shows a simplified absorption chiller machine 101. This machine 101 includes an evaporation section 103 and an absorption section 105.

The refrigerant 107 in this example is water metered into the evaporator section 103. Water is circulated through the spray head 111 such that the refrigerant circulation pump 109 is sprayed onto the tube bundle 113 of cooled water. This infiltrates the tube bundle 113 through which water circulated from the cooling water system passes. Heat from the coolant system 113 evaporates the refrigerant 107 to produce water vapor, shown schematically at 115. Water continues to evaporate and must be replenished.

In the absorption section 105, the absorbent (LiBr) solution 117 has a lower vapor pressure than water evaporated from the evaporator section 103 and readily absorbs water vapor 115 into the solution 117. The LiBr solution 117 is recycled via the LiBr solution circulation pump 119 through the spray head 121 to provide a larger surface area to the solution to attract water vapor 115. As solution 117 absorbs water, solution 117 is diluted. If water is not removed, the solution 117 will no longer have any attraction potential and will be diluted to the extent that the absorption process is stopped. Another pump 123 continues to remove some of the solution 117 and pumps some of the solution 117 into the concentrator 125. The solution pumped to the concentrator 125 is called a dilute solution because it contains water absorbed from the evaporator 105.

Thickener (generator) 125 includes a boiler 127 and a condenser 129. Boiler 127 requires a heat source that can be either steam or hot water 131. Condenser 129 typically requires a stream of cooling water from cooling tower system 133. The dilute solution is pumped into the concentrator 125 where the dilute solution is boiled. The boiling action turns water into steam leaving the absorbent solution, and water vapor is attracted to the condenser coil 129. Water is collected and metered back through the orifice 135 to the evaporator section 103 to condense into the incoming liquid. The absorbent solution becomes a concentrated absorbent solution 137 and is drained back through line 139 to absorbent section 105 for circulation by absorbent pump 119.

The absorption process 101 is simple considering that the only moving parts are the pump motor and the pump impeller. Absorption chillers may include more than one stage resulting in more efficient absorption machines than single-stage designs.

FIG. 2 illustrates a non-vacuum absorption refrigeration system 201 that may use non-corrosive materials for piping and vessels because it does not operate under vacuum. This system 201 uses membrane distillation to replace the boiler 127 and condenser 129 and evaporator 103 and absorber 105 used in concentrator 125. Membrane distillation employs low temperature heat to evaporate water from one side of the membrane contactor and to condense water vapor on the other side of the membrane contactor. Due to evaporation, membrane distillation can cool the water. This system 201 uses a membrane contactor (concentrator) 203 and a membrane contactor (evaporator / absorber) 205.

Membrane contactors are devices that enable the transport of refrigerant vapor between two sides of the membrane where the liquid is in contact with two different liquids without passing through the membrane.

The refrigerant 207 circulation loop is formed by the refrigerant circulation pump 209, the refrigerant heat exchanger (refrigerant cooler) 211, the metering orifice 213 and the membrane contactor (concentrator) 203 tube side. The absorbent solution 215 circulation loop consists of an absorbent solution circulation pump 217, a primary absorbent solution heat exchanger (recuperator) 219, a thin absorbent solution heater 221, a membrane contactor (concentrator) 203 outer side, Secondary absorbent solution heat exchanger (recuperator) 219, another primary absorbent solution heat exchanger (solution cooler) 223 and membrane contactor (evaporator / absorber) 205 outer skin side. The sheath or tube side can be exchanged without any loss of function. The recuperator is used to recover heat from the hot absorbent solution 241 as the diluted cold absorbent solution 231 to increase system efficiency. The absorbent solution used in the exemplary embodiment is LiBr / H ₂ O, although other absorbents may be used. The refrigerant used in the exemplary embodiment is water, but other refrigerants may be used.

Another refrigerant flow 225 (to be used for cooling purposes) is combined with the metered refrigerant flow 227 to produce a refrigerant flow 229 to be cooled by the membrane contactor (evaporator / absorber) 205. Refrigerant flow 229 is coupled to the tube contactor (evaporator / absorber) 205. The present invention uses membrane distillation to cool the refrigerant flow 229 in the membrane contactor (evaporator / absorber) 205 and to concentrate the dilute absorbent solution 237 heated by the membrane contactor (concentrator) 203. .

Heat is removed from the refrigerant fluid 229 flowing through the membrane contactor (evaporator / absorber) 205 via evaporation of the refrigerant 207 from the fluid 229 flowing through the tube side of the membrane contactor 205. At the outer side of the membrane contactor (evaporator / absorber) 205, the absorbent solution 215 has a lower vapor pressure than the refrigerant fluid 229 on the tube side of the membrane. The absorbent solution 215 absorbs the vapor of the refrigerant fluid 229 carried through the membrane pores. This absorption leads to greater evaporation of the refrigerant fluid 229 inside the membrane contactor.

Similarly, when the absorbent solution diluted to a temperature such that the refrigerant vapor pressure from the skin side in the concentrator is higher than the refrigerant on the tube side in the concentrator, the refrigerant vapor will be transported from the absorbent solution side to the refrigerant side. The absorbent solution loosens the refrigerant and concentrates.

3 is a cutaway view of a typical membrane contactor 301 configuration that may be used for membrane contactor (concentrator) 203 and membrane contactor (evaporator / absorber) 205. Membrane contactor 301 has a configuration similar to a tube-shell exchanger in which tubes composed of hydrophobic microporous membranes are arranged, whereby input and output tube side ends 303, 305 through which one fluid flows are coupled, and Another fluid flows through the tube through the sheath input and output 307, 309. Since the surface of the microporous membrane is hydrophobic, the membrane will not allow liquid water or LiBr / H ₂ O solution to pass through the pores on both sides of the membrane. The microporous membrane in both the contactor (concentrator and evaporator / absorber) has a surface energy lower than the surface tension of polypropylene, polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE) or pure water. It may be made of another material having a. Alternatively, the membrane made of the material or materials has a surface energy lower than the surface tension of pure water or refrigerant.

4 is a cross-sectional view of the membrane wall 401 in the membrane contactor ((concentrator) 203 and (evaporator / absorber) 205). Membrane wall 401 includes membrane 403 and microporous sheath 405. Membrane surface 407 is hydrophobic. The cavity 409 is filled with gas and forms two interfaces, a liquid refrigerant and a refrigerant vapor interface 411, and a liquid absorbent solution and a refrigerant vapor interface 413. In the membrane contactor (evaporator / absorber) 205, the absorbent solution 245 flows over the tube (the sheath side) and the refrigerant fluid 229 flows in the tube (the tube side). In the membrane contactor (concentrator) 203, the hot absorbent solution 237 flows over the tube (envelope side) and the low temperature refrigerant 207 flows in the tube (tube side).

5 is a cross-sectional view of an example of one hollow fiber tube in membrane contactor (evaporator / absorber) 205. In the membrane contactor (evaporator / absorber) 205, the cold absorbent solution 245 is shown flowing across the hollow fiber tube at the skin side. Refrigerant fluid 229 is shown to flow within each hollow fiber. FIG. 6 is an enlarged view of the hollow fiber wall shown in FIG. 5, which shows the transition from evaporation to condensation for a solution having a water vapor pressure greater than the outside.

The microporous membrane has a pore size in the range of about 0.1 to 0.6 μm and a porosity greater than 50%. The membrane acts as a barrier between the two states of the absorbent solution and the refrigerant fluid. The surface energy of the membrane is sufficiently lower than either the surface tension of the absorbent solution or the surface tension of the refrigerant fluid. The membrane evaporates the refrigerant from the refrigerant fluid 229 in the membrane contactor (evaporator / absorber) 205 and the dilute absorbent solution 237 in the membrane contactor (concentrator) 203 in conjunction with the process parameters. The membrane allows refrigerant vapor to pass through the membrane. The driving force is the difference in vapor pressure across the membrane.

On the tube contactor (evaporator / absorber) 205 tube side, the refrigerant from the refrigerant fluid 229 will evaporate from the meniscus formed near the inlet of the membrane cavity (FIG. 4). The vapor will be carried through the membrane pores to the skin side. Water vapor is absorbed by the absorbent solution meniscus near the membrane pore inlet on the skin side.

Since the refrigerant vapor pressure difference is the driving force in the membrane distillation, evaporation and absorption can be continued without vacuum. This surface evaporation combined with a large contact area is achieved using hollow fiber membrane contactors. Refrigerant absorption is effected by concentrated absorbent in the membrane contactor (evaporator / absorber) 205 shell side to produce cooled refrigerant fluid 229 through evaporation and membrane contactor (concentrator) for concentrating the dilute absorbent solution 237. Sustained by colder water flowing on the tube side in 203.

The low temperature concentrated absorbent solution 245 has a concentration of 56.8% by weight and a refrigerant vapor pressure of 0.57 Pa (4.3 mmHg) at 0.31 ° C. (31.44 ° F.) at the inlet of the membrane contactor 205 on the absorbent solution side, for example. vp _{evaporator / absorber} . This vapor pressure is lower than 0.95 kPa (7.1 mmHg), which is the vapor pressure of the refrigerant fluid 229 at 7.22 ° C. (45 ° F.) at the refrigerant outlet of the membrane contactor 205. After passing through the membrane contactor 205, the concentrated absorbent solution is diluted to 56% and the temperature is raised to 8.27 ° C. (46.9 ° F.). At the outlet of the absorbent solution of the membrane contactor 205, the refrigerant vapor pressure is from the refrigerant fluid 229 at 1.51 kPa (11.3 mmHg) at 12.77 ° C. (55 ° F.) at the inlet on the refrigerant side of the membrane contactor 205. Lower 1.48 kV (11.1 mmHg). This vapor pressure difference ensures absorption of the refrigerant vapor from the refrigerant fluid 229 by the absorbent solution 245 inside the membrane contactor 205.

The refrigerant fluid 229 temperature t ° _{evaporator / refrigerant-fluid} in the membrane contactor 205 determines the refrigerant vapor pressure vp _{evaporator / refrigerant-fluid} . In order to cool the refrigerant fluid 229, the vapor pressure of the refrigerant fluid 229 must be higher than the vapor pressure of the absorbent solution 245 in the membrane contactor (evaporator / absorber) 205.

vp _{Evaporator / Refrigerant-Fluid} > vp _{Evaporator / Absorbent} (1)

The weight percent concentration of the absorbent solution is known, and using the weight percent concentration in the membrane contactor (evaporator / absorber) 205 and the solution temperature t ° _{evaporator / absorbent} , the absorbent solution vapor pressure vp _{evaporator / absorbent} can be obtained. . The conversion from temperature and concentration to vapor pressure can be performed using either an equation or a memory lookup table.

The absorbent solution cooler 223 is configured to output the absorbent solution 245 to a predetermined temperature t ° _{evaporator / absorbent} corresponding to a predetermined vapor pressure vp _{evaporator / absorbent} for a given capacity absorption refrigeration system, whereby the membrane contactor (evaporator / To ensure that the absorber 205 functions up to its capacity. If a system change occurs and the vapor pressure relationship (1) is not met, the absorbent solution cooler 223 is thermostatically configured to lower the absorbent solution temperature t ° _{evaporator / absorbent} and thereby lower the absorbent solution vapor pressure vp _{evaporator / absorbent} . Can be controlled. In this way, relationship (1) will be maintained in any system change.

After the absorbent solution 231 passes through the membrane contactor (evaporator / absorber) 205 envelope side, the concentration of the absorbent solution 231 is due to the absorbent solution 245 absorbing the refrigerant from the refrigerant fluid 229. Lower than solution 245, thereby reducing its absorption capacity. The absorbent solution 245 becomes a diluted absorbent solution 231, and this absorbent solution 231 is referred to as a dilute absorbent solution.

The dilute absorbent solution 231 is circulated to the absorbent recuperator 219 which preheats the dilute solution 231 by the hotter concentrated absorbent solution 241. Preheated dilute solution 233 output by recuperator 219 is heated in dilute solution heater 221. The dilute solution heater 221 is heated to about 95 ° C. (203 ° F.) using hot water or steam source 235. The heated dilute absorbent solution 237 is input to the outer skin of the membrane contactor (concentrator) 203.

The hot dilute absorbent solution 237 may have a vapor pressure vp _{concentrator / dilute solution} of 16.67 kPa (125 mmHg) at a 56 wt% concentration and corresponding, eg, 95 ° C. (203 ° F.). The vapor pressure of the dilute absorbent solution 237 should be higher than the refrigerant 239 vapor pressure vp _{concentrator / refrigerant} , which may be 13.20 kPa (99 mmHg) at 36 ° C. (96.8 ° F.), for example, after passing through the refrigerant cooler 211.

The vapor pressure difference drives the vapor transport through the membrane pores. The dilute absorbent solution side of the membrane is at a temperature high enough to generate a higher vapor pressure than the refrigerant on the refrigerant side of the membrane.

The refrigerant temperature t ° _{concentrator / refrigerant} in the membrane contactor 203 determines the refrigerant vapor pressure vp _{concentrator / refrigerant} . In order to concentrate the dilute absorbent solution, the vapor pressure of the dilute absorbent solution must be higher than the vapor pressure of the refrigerant in the membrane contactor 203.

vp _{thickener / dilute solution} > vp _{thickener / refrigerant} (2)

The weight percent concentration of the dilute absorbent solution 237 is known, and the dilute solution vapor pressure vp _{concentrator / dilute solution} can be obtained using the wt% concentration in the membrane contactor 203 and the dilute solution temperature t ° _{concentrator / dilute solution} . Can be. The conversion from temperature and concentration to vapor pressure can be performed using either an equation or a memory lookup table.

The dilute solution heater 221 and the refrigerant cooler 211 provide a predetermined temperature t˚ _{concentrator / dilute solution} and t˚ _{concentrator / refrigerant} corresponding to the predetermined vapor pressure vp _{concentrator / dilute solution} and vp _{concentrator / refrigerant} for absorption refrigeration systems of a given capacity. Furnace dilute solution 237 and low temperature refrigerant 239, thereby ensuring that the membrane contactor (concentrator) 203 functions up to its capacity. If a system change occurs and the vapor pressure relationship (1) is not met, the dilute solution heater 221 is automatically adapted to raise the dilute solution temperature t ° _{concentrator / dilute solution} and thus raise the dilute absorbent solution vapor pressure vp _{concentrator / dilute solution} . It can be controlled in a temperature controlled manner. Conversely, if relationship (1) is not met, the refrigerant cooler 211 can be controlled in a thermostatic manner such that, for example, the refrigerant t _{concentrator / refrigerant} is lowered and thus the refrigerant vapor pressure vp _{concentrator / refrigerant} is lowered. In this way, relationship (1) will be maintained in any system change. A control device may be provided that controls both the dilute solution heater 221 and the refrigerant cooler 211.

The dilute absorbent solution after passing through the membrane contactor (concentrator) 203 becomes a concentrated absorbent solution 241, thereby restoring its absorbent capacity. The absorbent solution 241 is circulated by the absorbent solution circulation pump 217 through the absorbent solution recuperator 219 in which the absorbent solution is precooled (243) and then the absorbent solution cooler (243). By passing through 223, the absorbent solution cycle is completed.

The refrigerant pump 209 circulates the refrigerant 239 through the cooler 211 cooled by the water 243 of the cooling tower. A portion of the cooled refrigerant 238 passes through the membrane contactor 203 and the remainder of the refrigerant is sent to the evaporator / absorber 205.

As can be appreciated, the refrigerant in the refrigerant fluid 229 that is absorbed by the absorbent solution 245 into the absorbent solution 231 circulation loop (by the membrane contactor 205) is [by the membrane contactor 203]. The refrigerant 207 is returned to the circulation loop again. Refrigerant 207 losses that may occur may be replenished using heads or storage tanks (not shown).

The membrane contactor 203 may employ low temperature heat to evaporate water from the dilute absorbent solution 237 in the skin side and condense the vapor in the tube side through which the refrigerant 207 is circulated. The heated refrigerant 239 is cooled by the refrigerant cooling heat exchanger 211 using water 243 in the cooling tower.

Non-vacuum absorption refrigeration system 201 using the membrane contactor of the present invention can achieve a high coefficient of performance (COP). The coefficient of performance of the system is the ratio of the amount of cooling to the amount of heat supplied to drive the absorption cycle.

Non-vacuum absorption refrigeration system 201 uses membrane contactors in evaporator / absorber 205 and concentrator 203. The thermal efficiency η for each membrane contactor 203, 205 is calculated.

The thermal efficiency for the membrane contactor (concentrator) 203 is defined by the following equation:

(3)

(3)

Where η _G is the thermal efficiency of the membrane contactor (concentrator) 203, Q _HV is the heat of evaporation for water from the absorbent solution 237, and Q _CG is from the absorbent solution side of the membrane in the concentrator 203. Heat loss through conduction of the membrane in concentrator 203 to the refrigerant side.

The thermal efficiency for the membrane contactor (evaporator / absorber) 205 is defined by the following equation:

(4)

(4)

Where η _A is the thermal efficiency of the membrane contactor (evaporator / absorber) 205, Q _HV is the heat of evaporation of water from the refrigerant fluid 229, and Q _CA is the absorbent solution side of the membrane in the membrane contactor 205 Heat loss to the refrigerant side of the membrane in membrane contactor 205.

The conduction heat Q _CA should be as small as possible to have high thermal efficiency. Q _CG is similar.

In the evaporator / absorber 205, evaporation of the refrigerant 207 from the refrigerant fluid 229 provides a cooling action. However, condensation of the refrigerant 207 on the cold absorbent solution 245 side of the membrane heats the absorbent solution as the absorbent solution dilutes. Evaporator / absorber 205 membrane material should be selected for its thermal insulation capability.

The coefficient of performance (COP) for the non-vacuum absorption refrigeration system 201 can be derived as the following equation:

(5)

(5)

Where η _A is the thermal efficiency of the membrane contactor (evaporator / absorber) 205, η _G is the thermal efficiency of the membrane contactor (concentrator) 203, and F is the absorbent solution 233 from the absorbent solution 241. Is the percentage of heat energy recovery through the absorbent solution recuperator 219.

As can be appreciated from equation (5), the thermal efficiency (η _A ) of the membrane contactor (evaporator / absorber) 205 for the non-vacuum absorption refrigeration system 201 to cool the refrigerant fluid 229. ) Must be greater than 50%:

η _A > 50% (6)

If the thermal efficiency η _{A of the} membrane contactor (evaporator / absorber) 205 is less than 50%, the membrane contactor (evaporator / absorber) 205 will heat the refrigerant fluid without cooling the refrigerant fluid 229. The membrane material in the membrane contactor (evaporator / absorber) 205 must satisfy equation (6).

Advantages of non-vacuum absorption refrigeration machines include eliminating corrosion due to the corrosive properties of the absorbent solution by eliminating all metal parts and thus using non-corrosive materials such as plastics, which are non-corrosive materials Also considerably reduces. The use of membrane distillation obviates existing problems by isolating the absorbent solution from the refrigerant.

One or more embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, such other embodiments are also within the scope of the following claims.

Claims (26)

A membrane contactor (evaporator / absorber) that cools the refrigerant fluid and generates refrigerant vapor, and carries the absorption solution to absorb the refrigerant vapor, thereby producing a refrigerant-absorbing (dilute) solution;
Membrane contactor (concentrator) which removes the refrigerant from the dilute solution and thereby provides a concentrated absorbent solution for the membrane contactor (evaporator / absorber).
Non-vacuum absorption refrigeration system comprising a. The non-vacuum absorption refrigeration system of claim 1 wherein non-corrosive materials are used for system piping and vessel construction. The non-vacuum absorption refrigeration system according to claim 2 wherein the non-corrosive material is plastic. The membrane contactor (evaporator / absorber) and membrane contactor (concentrator) of claim 1 wherein the membrane contactor (evaporator / absorber) is designed and operated for membrane distillation, including direct contact membrane distillation, air gap membrane distillation, carrier gas membrane distillation, and vacuum membrane distillation. -Vacuum absorption refrigeration system. The non-vacuum absorption refrigeration system of claim 4 wherein the membrane contactor comprises a microporous membrane having hydrophobic inner and outer surfaces. 6. The method of claim 5, wherein the microporous membrane material on or in the interior and exterior surfaces has a surface energy lower than the surface tension of polypropylene, polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE) or refrigerant. A non-vacuum absorption refrigeration system selected from the group consisting of any other materials having. 6. The non-vacuum absorption refrigeration system according to claim 5 wherein the microporous membrane has a wall porosity of greater than 50%. The non-vacuum absorption refrigeration system according to claim 7 wherein the microporous membrane has a pore size in the range of about 0.1 to 0.6 μm. 9. The non-vacuum absorption refrigeration system according to claim 8 wherein the pore size and hydrophobicity are such that the absorbent solution and refrigerant do not penetrate the membrane pores. 10. The non-vacuum absorption refrigeration system according to claim 9 wherein the surface energy of the membrane in the membrane contactor (evaporator / absorber) and the membrane contactor (concentrator) is lower than either the surface tension of the dilute absorbent solution or the surface tension of the refrigerant. . 6. The method of claim 5, further comprising an absorption solution circulation loop, a refrigerant circulation loop, and a metered refrigerant flow,
Absorbent solution circulation loop and refrigerant fluid flow through the membrane contactor (evaporator / absorber),
The refrigerant circulation loop and the absorbent solution circulation loop flow through the membrane contactor (concentrator),
The metered refrigerant flow is coupled to the refrigerant fluid flow
Non-vacuum absorption refrigeration system. 12. The apparatus of claim 11, further comprising: a heater configured to heat the dilute absorbent solution to a predetermined temperature before entering the membrane contactor (concentrator);
A cooler configured to cool the refrigerant to a predetermined temperature prior to entering the membrane contactor (concentrator);
A cooler configured to cool the concentrated absorbent solution to a predetermined temperature prior to entering the membrane contactor (evaporator / absorber)
Non-vacuum absorption refrigeration system further comprising. 13. The non-vacuum absorption refrigeration system according to claim 12 wherein the dilute absorbent solution preset temperature determines the dilute absorbent solution vapor pressure and the refrigerant preset temperature determines the refrigerant vapor pressure. 14. The thinner absorbent solution vapor pressure is higher than the refrigerant vapor pressure, and the refrigerant is evaporated from the dilute absorbent solution on one side of the membrane contactor through which the dilute absorbent solution is circulated, and the evaporated refrigerant is condensed on the other side of the membrane contactor through which the refrigerant is circulated. Non-vacuum absorption refrigeration system. 13. The non-vacuum absorption refrigeration system according to claim 12 wherein the dilute absorbent solution heater pressure is raised when the dilute absorbent solution vapor pressure is below the refrigerant vapor pressure. 13. The non-vacuum absorption refrigeration system according to claim 12 wherein the refrigerant cooler cooling temperature is lowered if the dilute absorbent solution vapor pressure is below the refrigerant vapor pressure. 13. The non-vacuum absorption refrigeration system according to claim 12 wherein the concentrated absorbent solution preset temperature determines the concentrated absorbent solution vapor pressure and the refrigerant fluid preset temperature determines the refrigerant fluid vapor pressure. 18. The membrane contactor of claim 17 wherein the concentrated absorbent solution vapor pressure is lower than the refrigerant fluid vapor pressure, and the refrigerant is evaporated from the refrigerant fluid solution on one side of the membrane contactor through which the refrigerant fluid is circulated, and the evaporated refrigerant is a membrane contactor through which the concentrated absorbent solution is circulated. A non-vacuum absorption refrigeration system that condenses on the other side of the. 13. The non-vacuum absorption refrigeration system according to claim 12 wherein the concentrated absorbent solution cooler cooling output temperature is lowered if the concentrated absorbent solution vapor pressure is above the refrigerant fluid vapor pressure. The non-vacuum absorption refrigeration system according to claim 1 wherein the refrigerant is water. The non-vacuum absorption refrigeration system according to claim 1 wherein the absorbent solution is a LiBr solution. 12. The non-vacuum absorption refrigeration system according to claim 11 wherein the refrigerant removed from the dilute solution is derived from metered refrigerant flow. 23. The non-vacuum absorption refrigeration system according to claim 22 wherein the refrigerant removed from the dilute solution is returned to the refrigerant circulation loop by a membrane contactor (concentrator). The non-vacuum absorption refrigeration system according to claim 1 wherein the thermal efficiency (η _A ) of the membrane contactor (evaporator / absorber) is greater than 50%. A method for non-vacuum absorption refrigeration,
Adding a refrigerant to the refrigerant fluid flow;
Circulating a concentrated absorbent solution and refrigerant fluid flow through a membrane contactor (evaporator / absorber);
Generating refrigerant vapor and cooling the refrigerant fluid flow in a membrane contactor (evaporator / absorber);
Absorbing the refrigerant vapor thereby producing a refrigerant-absorbing (dilute) solution;
Circulating the dilute solution and refrigerant through a membrane contactor (concentrator);
Generating refrigerant vapor from the dilute solution in a membrane contactor (concentrator);
Absorbing refrigerant vapor into the refrigerant;
Providing a concentrated absorbent solution for the membrane contactor (evaporator / absorber) and cooling the solution
How to include. The method of claim 25, wherein the thermal efficiency η _A of the membrane contactor (evaporator / absorber) is greater than 50%.

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