WO2004111557A1

WO2004111557A1 - Multiutility vapor compression system

Info

Publication number: WO2004111557A1
Application number: PCT/IN2003/000408
Authority: WO
Inventors: Milind V. Rane; Avijeet Dasgupta
Original assignee: Rane Milind V; Avijeet Dasgupta
Priority date: 2003-06-12
Filing date: 2003-12-30
Publication date: 2004-12-23
Also published as: AU2003304208A1

Abstract

Conventional vapor compression system (VCS) provides only air conditioning and is not capable of providing hot and/or cold utility with air conditioning. Thus, it is not capable of operating as multiutility system. It is required to add heat and mass transfer surfaces in VCS to get multiutility effect resulting in heating and cooling of the fluid streams along with air conditioning. The invention relates to Energy Efficient Multi Utility Vapor Compression System (MUVCS) wherein judicious combination of Heat and Mass Transfer Devices (HMTD) facilitates hot and/or cold utility while conditioning air. This system capable of conditioning different spaces and conditioning air with high relative humidity. The system is also capable of thermal storage when catering to part air conditioning loads.

Description

MULTIUTIL1TY VAPOR COMPRESSION SYSTEM

Field of the Invention

The present invention relates to an Energy Efficient Multi Utility Vapor Compression System (MUVCS) wherein judicious coupling of Heat and Mass Transfer Devices (HMTD) facilitates generation of hot and/or cold utility while conditioning air. It further relates to a system capable of conditioning different spaces and conditioning air with high relative humidity. The system is also capable of thermal storage when catering to part air conditioning loads.

Background of the Invention A Vapour Compression System (VCS) typically consists of four components, namely a compressor, a condenser heat exchanger, an expansion valve and an evaporator heat exchanger. This is the most common type used in both Heating Ventilation and Air conditioning (HVAC) and industrial processes.

It is required to add heat transfer surfaces in VCS to get multiutility effect resulting in heating and cooling of the fluid streams along with air conditioning.

US patent no 6,041 ,613 discloses an air conditioning system which reduces energy consumption by disposing of waste heat to low temperature heat sink such as municipal water or effluent. In this system municipal water is heated in condenser of the Vapor Compression System. Additional heat recovery unit is placed in series with the condenser. However, it is not possible to use this system to provide cold utility as an additional heat recovery unit is not provided with evaporator of the vapor compression system.

US patent 4,538,418 discloses a water source heat pump system with heat exchanger units. Flow control valves are responsive to the pressure at the outlet of the refrigerant compressor to automatically optimize the operating conditions of the heat pump. Water source is in the form of a well, stream or body of water such as an ocean or lake. However, only condenser heat is utilized to heat water from ocean, lake and there is no heat exchanger with evaporator. This system does not provide with the cold utility and it is not possible to get hot and cold utility simultaneously.

Following are the desirable features of the multi utility system: a. Simultaneous generation of three utilities such as air-conditioning, cold and/or hot streams using a single vapor compression system b. Instant-on-demand supply of hot and/or cold c. Increased cooling capacity of the vapor compression system d. Reduced primary energy consumption The systems discussed in the prior art do not have the capability of providing hot and/ or cold utility along with air conditioning simultaneously Summary of the Invention

The main object of the present invention is to provide Energy Efficient Multi Utility Vapor Compression System (MUVCS) by judicious combination of Heat and Mass Transfer Devices (HMTD) to provide simultaneous hot and/or cold utility and conditioning of air.

Yet another object of the invention is to provide with the Vapor Compression System (VCS) comprising heat and mass transfer devices in series /integrated with evaporator / condenser of the vapor compression system to get hot / cold utility

Another object of the invention is to utilize contacting device as a HMTD Yet another object of the invention is to utilize finned tubes, tube and tube heat exchanger, plastic panel as HMTD

Yet another object of the invention is to provide hot/cold utility with heat transfer devices in series with the condenser/evaporator of the VCS

Another object of the invention is to provide hot/cold utility with heat transfer devices integrated with the condenser/evaporator of the VCS

Yet another object of the invention is to provide air conditioning to different spaces at different locations

Another object of the invention is to provide air conditioning for high relative humidity areas. Yet another object of the invention is to provide MUVCS wherein contacting device enables thermal storage when air conditioning load is lower than the designed capacity of the system

Another object of the invention is to provide MUVCS wherein contacting device/s are used as evaporator and condenser and HMTD A mere combination of a VCS with a HMTD functioning independent of one another would only give additive effects of the two devices. The main feature of this invention is that a judicious coupling of these two devices synergistically function to produce new effects such as generating hot and/or cold utility while conditioning air.

Thus in accordance with the invention MUVCS comprises of various system options as: a. HMTD placed in series with condenser/evaporator of VCS b. HMTD are integrated with condenser/evaporator and are in parallel with the refrigerant circuit of the condenser/evaporator of VCS c. Air conditioning different spaces at distant locations with compressor of VCS placed at a location d.. HMTD used as evaporator/condenser for conditioning air with high relative humidity DETAILED DESCRIPTION OF THE INVENTION

Other features and advantages of this invention will become apparent in the following detailed description of the preferred embodiments of this invention with reference to the accompanying drawings, in which: Figure 1 Schematic of VCS

Figure 2 Schematic of MUVCS with HMTD in series with condenser / evaporator Figure 3 Schematic of MUVCS with HMTD in parallel with condenser / evaporator Figure 4 Schematic of MUVCS with HMTD at different distant locations Figure 5 Schematic of MUVCS with contacting devices as HMTD and condenser / evaporator

A schematic of Conventional Vapor Compression System (VCS) shown in Figure 1.

High pressure-high temperature refrigerant vapour is discharged by compressor 1, through the conduit 2, to condenser 7 through conduit 5 where it rejects heat 6 to ambient. Further condensed high pressure-low temperature liquid refrigerant passes through the conduit 8 to liquid-vapour heat exchanger 9, where refrigerant is sub cooled by delivering heat to the vapour refrigerant from the evaporator 16 while passing to compressor 1. Sub cooled refrigerant is throttled in throttling device 11 and passes through conduit 15, to evaporator 16. In 16 it extract heat 17 from the space to be conditioned, low pressure vapour refrigerant further passes through the conduit 18 to 9 where it is super-heated. This superheated refrigerant vapour passes through the conduit 19 back to 1 to complete the cycle.

Conventional VCS provides only air conditioning and is not capable of operating as multiutility system. The main feature of this invention is that a judicious coupling of VCS and HMTD synergistically function to produce new effects such as generating hot and/or cold utility while conditioning air. Various options for MUVCS are as follows: a) In one of the embodiments HMTD is in series with condenser/evaporator of VCS in which

• HMTD is in series with condenser/evaporator of VCS

• HMTD is before condenser of VCS in refrigerant circuit • Part of the total heat is rejected to fluid in HMTD by the refrigerant to obtain hot utility

• Residual heat is rejected to atmosphere by the refrigerant in the condenser

• HMTD is placed before evaporator of VCS in refrigerant circuit

• The heat from the fluid in HMTD is absorbed to evaporate part of the refrigerant to obtain cold utility • Heat from the space to be conditioned is absorbed to evaporate residual refrigerant The system and process to operate option (a) is shown in Figure 2 with schematic of MUVCS with HMTD in series with condenser / evaporator of VCS. Vapor Compression System works as already explained in Figure 1. Additional heat and mass transfer devices are added in series with the condenser and evaporator. In 3, high temperature refrigerant vapour transfers heat to the fluid in conduit 4 to get hot utility. Refrigerant is further passed through conduit 5 to 7, where it rejects heat 6 to ambient. Sub cooled refrigerant is throttled in the throttling device 11, which is then passed through the heat transfer device 13, placed in series with 16. Low pressure- low temperature liquid refrigerant in conduit 12 is evaporated by absorbing heat from the fluid passing through conduit 14, where the fluid is chilled.

In another embodiment of (a) fluid is not passed through conduit 4 and 14 to get hot and cold utility while conditioning air. Same system can condition air without delivering hot and cold utility. b) In another embodiment HMTD is integrated with condenser/evaporator of VCS in which • HMTD and condenser of the VCS are integrated in a single device such that they are in parallel connection in refrigerant circuit

• Part of the total heat is rejected to fluid in HMTD by the refrigerant to obtain hot utility

• Residual heat is rejected to atmosphere by the refrigerant in the condenser

• HMTD and evaporator of the VCS are integrated in a single device such that they are in parallel connection in refrigerant circuit

• The heat from the fluid in HMTD is absorbed to evaporate part of the refrigerant to obtain cold utility

• Heat from the space to be conditioned is absorbed to evaporate residual refrigerant The system and process to operate option (b) is shown in Figure 3 with Schematic of MUVCS with HMTD integrated with condenser/evaporator of VCS. Vapor Compression System works as explained in Figure 1. Additional heat and mass transfer devices are integrated with the condenser and evaporator. Device 120 consists of condenser and Heat and Mass Transfer Device (HMTD), integrated and in parallel connection in refrigerant circuit with the condenser. The vapour refrigerant in 120 rejects major part of heat to the fluid passing through 121 to get the hot utility through conduit 107. Excess heat 106 is rejected to air. High pressure low temperature liquid refrigerant from 120 passes through 110 to liquid vapor heat exchanger 111. Low pressure- low temperature liquid refrigerant in 124 is partially evaporated by absorbing heat 127 from the space to be conditioned. Refrigerant is further evaporated by absorbing heat from fluid passing through 125. In another embodiment of (b) thermal contact between tubes carrying fluid in the HMTD and refrigerant tubes is enabled by fins. A set of the tubes carrying refrigerant and fluid are in the form of rows. c) In yet another embodiment conditioning of air is provided at different locations in which

• HMTD and condenser of the VCS are integrated in a single device such that they are in parallel connection in refrigerant circuit

• Residual heat is rejected to atmosphere by the refrigerant in the condenser • HMTD and evaporator of the VCS are integrated in a single device such that they are in parallel connection in refrigerant circuit

• The heat from the fluid in HMTD is absorbed to evaporate part of the refrigerant to obtain cold fluid which is circulated through another HMTD/s placed at different locations to condition respective spaces • Heat from the spaces at different distant locations is absorbed by the cold fluid and cold fluid is recirculated in the HMTD which is integrated with the evaporator of the VCS

• Heat from the space to be conditioned is absorbed to evaporate residual refrigerant

The system and process to operate option (c) is shown in Figure 4 with schematic of MUVCS with HMTD at different location/s. Vapor Compression System works as explained in Figure 1. Additional HMTD 230 is used to facilitate conditioning of air at distant location. Low pressure- low temperature liquid refrigerant in 224 is partially evaporated by absorbing heat 227 from one of the spaces to be conditioned. Refrigerant is further evaporated by absorbing heat from fluid passing through 225. Cold fluid from 225 passes through 215 to pump 228. Pump feeds the cold fluid through conduit 229. to 231 of the heat and mass transfer device 230 which is placed in the space to be conditioned which is located at a distance from the 217. Thus, it is possible to condition different spaces at different distant locations by evaporating refrigerant at one location only. After absorbing heat from the space to be conditioned, fluid passes through conduit 233 back to 225. Low pressure vapour refrigerant further passes through the conduit 218 to 223 where it is super-heated. Superheated refrigerant vapour passes through the conduit 219 to compressor 201 and cycle is completed, d) In another embodiment conditioning of air of high relative humidity is provided in which

• HMTD is a contacting device consisting of a rotating assembly submerged in liquid desiccant/ water in a containment vessel • Liquid Desiccant (LD) is cooled by the evaporator of the VCS which is in thermal contact with the containment vessel

• Moisture from the air with high relative humidity is absorbed by cooled LD • Refrigerant rejects heat to LD in another containment vessel to release absorbed moisture in the LD

• Water/ liquid desiccant is used in containment vessel to use the system as thermal storage when air conditioning load is lower than the designed capacity of the system

The system and process to operate option (d) is shown in Figure 5 with schematic of

MUVCS with contacting devices as HMTD and condenser / evaporator. The system comprises of an absorber/ICD 318, which incorporates large surface density contacting discs 301 , in plurality mounted'on a shaft 302. The disc-assembly placed in a trough 303, containing the LD. The trough is made of any material that is compatible with the LD and air. A fan, 316 circulates the indoor air through the absorber/ICD, which gets dehumidified and cooled as it passes through the absorber. In an embodiment the fan may be a forced/induced draft fan. A hood, 314 guides the indoor air over the contacting disc assembly. Concentrated LD enters the absorber/ICD through conduit 306. Weak LD leaves the absorber/ICD through conduit 307. The contacting discs are partially submerged in the LD, in the absorber/ ICD. The disc assembly is rotated by a drive at low rpm in the LD, preferably at around 3 to 5 rpm or oscillated to an angle greater than 30° in either direction. The refrigerant of VCRS is expanded in the throttle valve, 321 and the low temperature refrigerant flows in through conduit 311 to the passages 309, that are in thermal contact with the outer lower surface or inner surface or integrated with the trough wall of the absorber/ ICD. The LD in the absorber/ICD is cooled as the refrigerant evaporates in the passages 309. The cooled desiccant in the absorber has high affinity to absorb the moisture from the indoor air. After absorbing the moisture from the indoor air, weak LD flows through conduit 307 and led to the pump 330, to the regenerator/OCD, 319 through a liquid- liquid heat exchanger 331. This heat exchanger is provided to heat the LD from the absorber/ICD and cool the desiccant stream as it flows from regenerator/OCD 319, which flows in to the absorber/ ICD. Refrigerant exits from the absorber/ICD through conduit 312 and moves to the compressor 320. Refrigerant after compression passes through conduit 310 to the passages 309 of regenerator/OCD, 319 which are in thermal contact with the outer lower surface or inner surface or integrated with the trough wall of the regenerator/OCD. The weak LD from absorber/ICD after liquid-liquid heat exchanger flows to the regenerator/OCD. The weak LD enters the regenerator /OCD through conduit 327. The heat required for the regeneration is supplied by the refrigerant condensing in the passages 309. After condensation of the refrigerant in regenerator/ OCD, it moves through conduit 12 which led to throttling device 321.

The regenerated, strong LD flows out from the regenerator/OCD through conduit 308 and pumped with LD pump 332 to the absorber/ ICD through the liquid-liquid heat exchanger, 331. A hood 314 is provided to guide the outdoor air through the regenerator/OCD. A fan 316 is provided to circulate the outdoor air through the regenerator/OCD. The contacting disc assembly is partially submerged in the LD in the regenerator/OCD. The ambient air pickups the moisture from the hot desiccant, in the trough of regenerator/OCD. In another embodiment of

(d) water is used in trough 303 instead of liquid desiccant to use the system as thermal storage when air conditioning load is lower than the designed capacity of the system

In yet another embodiment of (d) HMTD is a contacting device consisting of a rotating assembly and a liquid desiccant/ water in a containment vessel or any other suitable contacting device

In another embodiment of (a)-(c) HMTD consists of finned tubes, tube and tube or any suitable heat transfer surface

In another embodiment of (d), air conditioning for high humidity areas is provided using contacting devices as HMTD

In yet another embodiment of (d), contacting device enables thermal storage while air conditioning is not at peak load In another embodiment of (d), contacting device/s are used as evaporator and condenser and HTD to get hot and/or cold utilities and air conditioning

In another embodiment of (a)-(d), any suitable refrigerant such as ammonia, R 22, CO₂ etc. is used as refrigerant

Example

Example shows the result of the combination in a wherein HMTD is places in series with condenser/evaporator of the VCS as explained in embodiment (a). Vapor compression system used in the example is window air conditioner. Important parameters, needed to evaluate the performance this system are tabulated in Table 1. Performance of this Multi Utility Vapor Compression System (MUVCS) operating in different modes is compared with the air conditioning (AC) mode.

In AC + Water Heating (WH) + Water Cooling (WC) mode most of the condenser heat is delivered to the water being heated. Lower condensing pressure leads to a lower pressure ratio. This results in 5.47 % increase in total cooling capacity, to 5.34 kW_c, of which about 4.59 kW is in the form of AC and 0.75 kW in the form of cooled potable water cooled to 15⁰C. Lower pressure ratio leads to 9.72 % lowering of power consumption, to 1.86 kW_e, which results in 16.82 % increase in cooling COP, to 2.87. Water heating duty works out to be 4.01 kW and the corresponding heating COP is 2.15. Overall COP of the HP is 5.02.

Definition

Symbol Description Symbol Description

AC air condition t temperature, ⁰C

COP coefficient of performance volf volume flow rate, lpm

CV calorific value, kJ/kg WAC window air conditioner

DBT dry bulb temperature, ⁰C WBT wet bulb temperature, ⁰C

Q heat duty, kW and TR WC water cooling

RTD resistance temperature detector WH water heating

SAC split air conditioner WHP window heat pump

SHP split heat pump η efficiency

SS stainless steel

Suffix Description Suffix Description ac air condition f fuel

C cooling h heating

CW cooled water hw hot water cw.o cooled water outlet hw.o hot water outlet e.a.i evaporator air inlet tot.c total cooling e.a.o evaporator air outlet w.i water inlet

In AC + WH mode also most of the condenser heat is delivered to the water being heated. This helps lower the condensing temperature to 44⁰C as compared to 54.9⁰C in the AC mode. Lower condensing pressure leads to a lower pressure ratio of 3.37. This results in reduced flashing at the outlet of the expansion device and higher compressor volumetric efficiency. This leads to 8.05 % increase in cooling capacity, to 5.47 kW_c. Lower pressure ratio leads to 8.13 % lowering of power consumption, to 1.89 kW_e, which results in 17.62 % increase in cooling COP, to 2.89. Water heating duty works out to be 3.13 kW and the corresponding heating COP is 1.65. Overall COP of the HP is 4.54.

Power consumption of the HP is reduced by 7.44 %. Since, the cooling capacity increased and the power consumption reduced, the cooling COP of the system enhanced by 10.41 %, which takes up the overall COP of the HP to 2.71. Table 1 : Experimental Results of 1.5 TR MUVCS

Parameters AC AC+WH+W AC+WH AC+WC

DBT e.a.i C 25.2 29.4 26.7 29.9 WBT e.a.i C 18.6 18.5 18.4 18.5 DBT e.a.o C 15.6 21.3 17.6 19.4 WBT e.a.o C 13.9 15.8 14.3 15.2 t w.i C 25.8 25.0 27.1 t hw.o C 45 45 t cw.o C 15 15 volf hw lpm 3.0 2.25 volf cw lpm 1.0 0.70 Q.ac kW 5.07 4.59 5.47 4.59

(TR) (1.44) (1.31) (1.56) (1.31)

Q.h kW 4.01 3.13 Q.cw kW 0.75 0.59

(TR) (0.21) (0.16)

Q.tot.c kW 5.07 5.34 5.47 5.18

(TR) (1.44) (1.52) (1.56) (1.47)

Power Input (includes kW 2.06 1.86 1.89 1.91 all auxiliaries)

COP.c 2.46 2.87 2.89 2.71 COP.h 2.15 1.65

Total COP of the 2.46 5.02 4.54 2.71 System

Reduction in Power % 9.72 8.13 7.44 Input, P.sys

Increase in Cooling % 5.47 8.05 2.19 Effect, Q.tot.c

Increase in COP.c % 16.82 17.62 10.41 In AC + WC mode the condenser is air cooled, which leads to higher condensing temperature of 54.9⁰C. Evaporating pressure increased because of cold water extraction and higher indoor air temperature. The total cooling capacity increased by 2.19 % because of cold water extraction which leads to higher inlet air temperature to the indoor unit.

The test results for both window and split HP in different modes shows that the cooling capacity is increased by 2.19 to 8.05 % and the cooling COP is enhanced by 10.41 to 37.86 % compared to conventional air condition systems. Performance of the HP reverts to that of conventional Air Conditioners when hot and cold water is not tapped. Thus, the judicious coupling of VCS and HMTD synergistically function to produce new effects such as generating hot and/or cold utility while conditioning air. A mere combination of a VCS with a HMTD functioning independent of one another would only give additive effects of the two devices.

Claims

What is claimed is:

1. Energy efficient multi utility vapor compression system (MUVCS) to generate hot and/or cold utility while conditioning air using Vapor Compression System (VCS) coupled with Heat and Mass Transfer Device (HMTD)

2. MUVCS as claimed in Claim 1 wherein:

• HMTD is in series with condenser/evaporator of VCS

• Residual heat is rejected to atmosphere by the refrigerant in the condenser

• HMTD is placed before evaporator of VCS in refrigerant circuit

• The heat from the fluid in HMTD is absorbed while evaporating part of the refrigerant to obtain cold utility • Heat from the space to be conditioned is absorbed while evaporating residual refrigerant

3. MUVCS as claimed in Claim 1 wherein HMTD is integrated with condenser/evaporator of VCS in which:

• Residual heat is rejected to atmosphere by the refrigerant in the condenser

• HMTD and evaporator of the VCS are integrated in a single device such that they are in parallel connection in refrigerant circuit • The heat from the fluid in HMTD is absorbed while evaporating part of the refrigerant to obtain cold utility

• Heat from the space to be conditioned is absorbed while evaporating residual refrigerant

4. MUVCS as claimed in Claim 1 to provide conditioning of air at different locations in which • HMTD and condenser of the VCS are integrated in a single device such that they are in parallel connection in refrigerant circuit

• Residual heat is rejected to atmosphere by the refrigerant in the condenser

• HMTD and evaporator of the VCS are integrated in a single device such that they are in parallel connection in refrigerant circuit • The heat from the fluid in HMTD is absorbed while evaporating part of the refrigerant to obtain cold fluid which is circulated through another HMTD/s placed at different locations to condition respective spaces • Heat from the spaces at different distant locations is absorbed by the cold fluid and cold fluid is recirculated in the HMTD which is integrated with the evaporator of the VCS

• Heat from the space to be conditioned is absorbed while evaporating residual refrigerant S. • MUVCS as claimed in Claim 1 to provide conditioning of air of high relative in which

• HMTD is a contacting device consisting of a rotating assembly submerged in liquid desiccant/ water in a containment vessel

• Liquid Desiccant (LD) is cooled by the evaporator of the VCS which is in thermal contact with the containment vessel • Moisture from the air with high relative humidity is absorbed by cooled LD

• Refrigerant rejects heat to LD in another containment vessel to release absorbed moisture in the LD

• Water/ liquid desiccant is used in containment vessel to use the system as thermal storage when air conditioning load is lower than the designed capacity of the system 6. MUVCS as claimed in Claim 2,3,4 wherein the HMTD is finned tube, tube and tube heat transfer device

7. MUVCS as claimed in Claim 1 wherein multi wall sheet of material such as polymer, plastic, aluminum, Stainless steel, metal alloy is used as HMTD

8. MUVCS as claimed in Claim 1 wherein conduit and metal mesh assembly with corrosion resistant coating is used as HMTD

9. MUVCS as claimed in Claim 5 wherein contacting device/s are used as evaporator and condenser

10. MUVCS as claimed in Claim 1 wherein any primary refrigerant such as ammonia, R 22, R12, CO₂ is used.