WO2004081462A1

WO2004081462A1 - Air conditioning method using liquid desiccant

Info

Publication number: WO2004081462A1
Application number: PCT/IN2003/000409
Authority: WO
Inventors: Milind V. Rane; S. V. Kota Reddy; Roshini R. Easow
Original assignee: Rane Milind V; Reddy S V Kota; Easow Roshini R
Priority date: 2003-03-12
Filing date: 2003-12-30
Publication date: 2004-09-23
Also published as: AU2003303998A1

Abstract

The present invention relates to a Process for Energy Efficient Conditioning of Air Using Liquid Desiccant (CAULD) with the contacting device functioning as adiabatic/diabatic humidifiers/dehumidifiers and/or direct/indirect Evaporative Coolers (EC) wherein the LD is regenerated by multi stage or single stage regeneration while ensuring the outgoing air stream free of LD. The main advantages of the CAULD is that the outgoing air stream is free of desiccant as compared to the conventional LD based air conditioning, use of low grade heat sources and possibility of recovering water. This is possible by the appropriate design of the dehumidifier, regenerator, liquid-liquid heat exchanger air-air heat exchangers and other components of CAULD. Significant reduction in weight and cost can be achieved with the use of alternate materials such as plastics and this eliminates problems due to corrosion. The system is compact, low weight and techno-economically viable for air-conditioning.

Description

AIR CONDITIONING METHOD USING LIQUID DESICCANT

Field of the Invention

The present invention relates to a Process for Energy Efficient Conditioning of Air Using Liquid Desiccant (CAULD) with the contacting device functioning as adiabatic/diabatic humidifiers/dehumidifiers and/or direct/indirect Evaporative Coolers (EC) wherein the LD is regenerated by multi stage or single stage regeneration while ensuring the outgoing air stream free of LD.

Background Art

In a conventional air conditioning process air is cooled below its dew point, using vapour compression refrigeration system (VCRS), to reduce the moisture content, followed by reheating of the air to a desired temperature prior to introducing it into the space to be conditioned. As the evaporator operates at low temperature, the power consumption of the conventional VCRS is high.

In liquid desiccant (LD) air conditioning process, air is dehumidified by exposing it to a substance that has affinity for water. Aqueous solutions of such substances are called liquid desiccants. Tri-ethylene glycol, Lithium chloride, Lithium bromide, Calcium chloride and their combinations are used as liquid desiccants. LD also has the ability to simultaneously control the microbiological contaminants from air streams and improve the indoor air quality. The air is not allowed to reach the saturation condition at any point in the desiccant cycle and hence it prohibits the growth of moulds, fungi, or other microbial organisms. (ASHRAE, "Fundamentals Handbook", American Society for Heating Refrigeration and Air-conditioning Engineers, pp 21.1-21.5, Atlanta, USA, 1997)

In LD air conditioning process, the LD contacts the air either in adiabatic dehumidifiers where the heat of absorption is transferred to the air and the air experiences a rise in temperature or in diabatic dehumidifiers where a part of the heat of absorption is transferred to a cooling media and the temperature of the air does not rise as much as in the case of adiabatic dehumidifiers. The temperature of the dehumidified air has to be reduced by sensible cooling. Sensible cooling or heating of air is that process where the temperature of the air is reduced or increased without change in moisture content.(Arora,C.P., "Refrigeration and Airconditioning", Second Edition.Tata cGraw Hill, 2000)

US Patent no. 6,216,483 titled "Liquid desiccant air conditioner" describes air conditioning process using a liquid desiccant dehumidifier, a boiler for reconstituting the dilute desiccant and an absorption refrigeration system to cool the dehumidified air. The dehumidification of air is achieved by spraying the LD in the dehumidifier. The LD is regenerated by heating in a boiler and the steam generated during the regeneration process is used to pre-heat the dilute desiccant before entering the boiler. A portion of the steam is used for the regeneration process in the regenerator of the vapour absorption refrigeration cycle. Spraying of LD in the dehumidifier results in carryover of LD into the indoor air stream thereby causing loss of LD and corrosion of ducts and equipment, in the conditioned space. Cooling of the air after dehumidification is done in a separate system operating on vapour absorption cycle. Such an arrangement increases the size of the operating system. The efficiency of regeneration in the said process is lower than that in multi stage regeneration because only part of the latent heat of steam generated is used to preheat the LD.

US Patent no. 5,351 ,497 titled "A low flow internally cooled liquid desiccant dehumidifier" is described as a part of a liquid desiccant air conditioning process, in which the LD is sprayed into the process air stream in the dehumidifier, which has water/air mixtures flowing in alternate passages with LD, so as to remove the heat of absorption. This arrangement prevents temperature rise of LD so that the dehumidification effectiveness is increased. The low flow rate of desiccant leads to maldistribution and channelling of LD with improper wetting of contacting media and reduced efficacy of contacting device. Scale formation in the channels carrying air/water mixture leads to fouling of heat transfer surfaces of the dehumidifier. The disadvantage of the system is that there is a possibility of leakage between the LD and water streams.

US Patent no. 5,460,004 titled "Desiccant Cooling System with Evaporative Cooling" describes air conditioning process using water as the refrigerant. The air conditioning process is achieved by passing process air through a pre cooling air-to-water heat exchanger, desiccant dehumidification module and a second air-to-water heat exchanger. Both heat exchangers receive cooling water from a cold-water source. The air is then sent to an indirect EC and then in to a direct EC. This system consumes large amount of water. Further there are problems of carryover of desiccant into process air stream. The system has numerous valves and dampers and is complex to operate.

US Patent no. 4,171 ,620 titled "Cooling method and system" discloses an air conditioning process wherein a stream of relatively wet warm air is dehumidified in a dehumidifier by bringing it in contact with hygroscopic liquid in water cooled absorbent zone. It is then passed through an evaporative cooling zone and the resulting cooled air or water is used as a cooling or refrigerating medium. A portion of the cooled water is used to cool the absorbent zone. The hygroscopic liquid is regenerated using solar energy or low temperature heat. The pumping power required for spraying of LD is high. Spraying causes carryover of LD, leading to loss of LD and corrosion of equipment in the conditioned space. US Patent no. 4,864,830 titled "Air conditioning process and apparatus" describes a system with absorption of water vapour by an aqueous salt solution. The absorbing liquid is cooled by indirect contact with a circulating water stream in a heat exchanger. The circulating water absorbs heat and the warmed water is expanded at reduced pressure to release water vapour and lower its temperature. This cooled water at reduced pressure is re circulated in the heat exchanger. Water vapour released is absorbed by the salt solution. The dilute solution is regenerated using heating fluid. Flow of a thin film of salt solution along the heat exchange surfaces will lead to channelling of LD and improper wetting of contacting surface which reduces the efficacy of the process. Maintaining vacuum increases power consumption of the system. US Patent no. 5,297,398 titled "Polymer desiccant and system for dehumidified air conditioning describes the use of a relatively inexpensive, less corrosive polymer desiccant in an air conditioning system comprising of a heat pipe having its heat absorption section in air inlet after the dehumidifier and heat rejector section before regenerator. The dehumidifier and regenerator of packed tower design have disadvantage of high pressure drop and large blower power requirement. The parasitic power increases due to the use of large number of pumps.

US Patent no. 5,050,391 titled "Method and apparatus for gas cooling" relates to a method for cooling of air and other gases utilising evaporative cooling and sorbent dehumidification. Moisture removal is done by exposing air to solid adsorbents on rollers. The contact between the air and adsorbent is not as efficient as when large surface area is exposed to LD. Regeneration of desiccant is done using hot air and is an inefficient method of regeneration. Co pending Indian Patent Application no. 153/MUM/2002 titled "Contacting Device" relates to a novel contacting device to provide intimate contact between fluids to enhance the interfacial area between them for increased heat and/or mass transfer. Carryover of liquid in to the air stream is eliminated. There is provision to heat/ cool the liquid based on the application.

Co pending Indian Patent Application no. 767/MUM/2002 titled "Energy Efficient Regeneration Process" relates to a novel energy efficient multi-stage regeneration process, for regenerating liquid desiccant (LD). There is provision to utilize the latent heat of vapour generated in High Temperature Regenerator (HTR) to relatively low temperature regenerator. Rotating contacting disks provide intimate contact between LD and air without problems of carryover of LD in to the air stream.

Problems in Prior Art

The challenges in making LD based conditioning of air techno-economically viable are: 1. to reduce the size and weight of these systems to those comparable with conventional equipment, like VCS based air conditioners

2. to develop processes for energy efficient LD based conditioning of air wherein the number of components are reduced, controls are simplified and outgoing air streams are free of LD

3. to make it possible to use low temperature/high temperature waste heat for regeneration of LD and enable dispersed regeneration and usage

4. to develop processes and components wherein the process is executed at near atmospheric pressure thereby eliminating pressure and vacuum parts 5. to reduce the cost of the equipment required to execute the process by using alternate low cost corrosion resistant materials

6. to eliminate difficulty in LD distribution

7. to reduce parasitic power requirements

The LD regeneration process/system ideally should exhibit the following attributes:

Summary of the Invention

The main object of the present invention relates to a Process for Energy Efficient Conditioning of Air Using Liquid Desiccant (CAULD) with the contacting device functioning as adiabatic/diabatic humidifiers/dehumidifiers and/or direct/indirect Evaporative Coolers (EC) wherein the LD is regenerated by multi stage or single stage regeneration while ensuring the outgoing air stream free of LD

Another object of the invention is to provide an energy efficient process for conditioning air, which helps reduce CO₂ emissions as compared to air conditioners using VCRS. Yet another object of the invention is to achieve sensible cooling of dehumidified air using air leaving the conditioned space to increase the energy efficiency of the process

Yet another object of the invention is to recover water from the process of multi stage regeneration of LD. The recovered water can either be used for selective rehumidification of air after being deep dehumidified using LD or for applications like drinking, food processing or for any other use. Yet another object of the invention is to recycle the available heat between hot LD and cold LD.

Another object of the invention is to use the regenerated LD for applications such as drying or comfort/ industrial air conditioning.

Thus in accordance with the invention CAULD comprises of various options as A) o A diabatic/adiabatic dehumidifying process wherein air is brought in contact with the LD o Single/multi stage regeneration, to regenerate the LD o Passing air through dehumidifier and EC o Optional diabatic/adiabatic humidification o Optional process to recycle heat and/or cold between air streams and/or LD streams o Optional Evaporative cooling of air stream(s) « Optional removal of recovered excess water o Recirculation of LD B)

An adiabatic dehumidifying process wherein air is brought in contact with the LD

Single/multi stage regeneration, to regenerate the LD

Passing air through dehumidifier

Recycling heat between LD streams • Optional removal of recovered excess water

Recirculation of LD C)

A diabatic dehumidifying process wherein air is brought in contact with the LD

Cooling of LD with air/ water/air water mixtures while it is dehumidifying air stream (s) • Passing air through dehumidifier

Recycling of heat between LD streams

Single/multi stage regeneration, to regenerate the LD

Optional removal of recovered excess water

Recirculation of LD D)

Single/multi stage regeneration, to regenerate the LD

• Evaporative cooling of air stream(s) ° Passing air through dehumidifier and EC's ° Recycling heat /cold between LD streams/air streams o Optional removal of recovered excess water

• Recirculation of LD E) o A diabatic dehumidifying process wherein air is brought in contact with the LD o Cooling of LD with air/ water/air water mixtures while it is dehumidifying air stream(s) o Evaporative cooling of air stream(s) o Passing air through dehumidifier and EC o Single/multi stage regeneration, to regenerate the LD o Recycling of heat between LD streams • Optional removal of recovered excess water ° Recirculation of LD F)

A diabatic dehumidifying process wherein air is brought in contact with the LD

Cooling of LD with chilled water while it is dehumidifying air stream(s)

Single/multi stage regeneration, to regenerate the LD

Passing air through dehumidifier • Recycling of heat between LD streams

Optional removal of recovered excess water

Recirculation of LD

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 Processes of Conditioning Air using Liquid Desiccant Represented on Psychrometric Chart Figure 2 System for Conditioning Air using Liquid Desiccants

Figure 3 Liquid Desiccant Dehumidifier with Evaporative Coolers

Figure 4 Dehumidifier with passages

Figure 5 System for Drying using Liquid Desiccants

Figure 1 shows processes of conditioning of air using liquid desiccant represented on psychrometric chart.

P) The process of adiabatic dehumidification is represented by a line through 960 and parallel to constant enthalpy line. Process 960 to 961 represents diabatic dehumidification of air while heat is rejected to ambient air. Process 960 to 962 represents diabatic dehumidification of air while heat is rejected to water /air water mixture. Air after going through any of the above- mentioned processes is termed as conditioned air and may be used when the application calls for dehumidified air. Choice of the particular process is governed by the temperature requirements of the application. Q) Process 960 to 961 represents diabatic dehumidification of air while heat is rejected to ambient air. This process is followed by sensible cooling of air 961 to 962. Process 962 to 963 represents the humidification and cooling of air to provide the conditioned air. Process 963 to 964 shows the air conditioning process when the sensible and latent heat is gained by the air supplied into the space to be conditioned. R) Process 960 to 962 represents diabatic dehumidification of air while heat is rejected to water /air water mixture. This process is followed by humidification and cooling of air process 962 to 963. Process 963 to 964 shows the air conditioning process when the sensible and latent heat is gained by the air supplied into the space to be conditioned. S) Process 960 to 963 represents diabatic dehumidification of air while heat is rejected to chilled water. Process 963 to 964 shows the air conditioning process when the sensible and latent heat is gained by the air supplied into the space to be conditioned. Fig 2 shows a system for conditioning air using liquid desiccants. In a preferred embodiment of the process as described in "R", ambient air 932 is induced into the dehumidifier 934 by fan 915 and leaves the dehumidifier as dehumidified air through conduit 942 and flows through air- air heat exchanger 943 and gets cooled by the air flowing from the conditioned space 949 and further passes to the EC 950, through conduit 944. Cooling water enters the passages, which are in thermal contact with the trough of dehumidifier, through conduit 939 and leaves through conduit 941. The removal of heat from the dehumidifier makes the dehumidification process diabatic. The EC 950 consists of rotating contacting discs 1, as the contacting media between the air and water. The trough 3 is holding the water in which the contacting discs are rotated or oscillated. A fan 921 is provided to induce/force the air through the EC 950. The air exiting the EC 950 is the conditioned air and is free of desiccant. This conditioned airflows to the conditioned space 949 through conduit 945. The air exiting from the conditioned space passes through heat exchanger 943 to recycle the cooling effect for cooling the air flowing from dehumidifier to EC.

The weak LD from the dehumidifier 934 passes to the pump 930 through conduit 937 and is pumped to Low Temperature Regenerator Heat Exchanger (LTRHE) 933 where it gets heated by the heated LD exiting the LTR 18 and further flows to High Temperature Regenerator Heat Exchanger (HTRHE) 41, through conduit 938, where it is heated further by hot LD exiting from HTR 32 and passes through conduit 33 and is introduced in to HTR 32. Water vapor is generated from the LD at high temperature and pressure due to the addition of heat 39, from suitable heat sources. This vapor passes through conduit 36 and gets sensibly cooled in HTRHE 41. Further it passes through conduit 10 and flows through the passages of LTR 8 and gets condensed completely in passages of LTR transferring its heat of condensation to the LD. This increases the energy efficiency of the process. This water then passes through conduit 12 and flows into trough 3 through valve 931 controlled by float 948, excess water is drained out through valve 948.

Partially regenerated LD from HTR 32 exits through conduit 34 and then passes through HTRHE 41 where it gets cooled and further passes to LTR 18 through conduit 6. After complete regeneration of LD in LTR it exits through conduit 935 and then passes through LTRHE 933 where it gets sub-cooled by the LD leaving the dehumidifier 934 and the regenerated LD enters the dehumidifier 934 through conduit 936 and leaves as weak LD through conduit 937 to the suction of the LD pump 930. The dehumidifier 934 may be located at distant locations in which case the conduits 936 and 937 are sufficiently long to service the dehumidifiers.

Figure 3 shows another embodiment for the process "R" of diabatic dehumidification of air followed by evaporative cooling. Ambient air 932 enters the dehumidifier housing 981 and contacts LD on the rotating contacting disc 1 which is mounted on shaft 2. The rotating / oscillating discs mounted on a shaft together with the trough for housing the assembly is hereinafter referred to as the contacting device. LD enters the trough 3 through conduit 987 and exits through conduit 988. The diabatic dehumidifier 981 is indirect evaporatively cooled by means of water entering through conduit 978. The water that has picked up heat from LD in trough flows through conduit 985 and further to pump 986 where it is pumped through conduit 977 to trough 3 of EC using ambient air. Ambient air 932 or air exiting conditioned space enters housing 970 of EC. The air contacts the water carried on contacting disc 1, mounted on shaft 2, is cooled and exits through fan 975 as cooled and humidified air 974. Water contained in the trough 3 gets cooled and exits through conduit 978 to use its cooling effect on the diabatic dehumidifier. The air exiting the dehumidifier further contacts the water carried on disc 1 mounted on shaft 2, gets cooled and humidified and exits with the help of a fan 980 as the conditioned air 979. Water enters trough 3 through conduit 990 and exits through conduit 991. Makeup water enters trough 3 of EC 970 through throttling device 992.

Figure 4 shows yet another embodiment for the process " " of a diabatic dehumidifier with passages for cooling the dehumidifier. The disc, 1 provides the contacting surface between the LD and air. The contacting surface is the mesh, or roughened surface, which holds the liquid on the surface for mass transfer. The discs in plurality are mounted on a square hollow or solid shaft 2. A trough, 3 contains the LD. Material of construction of the trough can be metal, non-metal or any other suitable, which is compatible with the LD and vapour/gas. The concentrated LD flows in to the trough 3 through inlet conduit 906. The weak LD flows out from the trough 3 through outlet conduit 907. Passages, 916 are in thermal contact with the trough. They can be inside/outside or integrated with the wall of the trough and be used for heat transfer from the LD in the trough. The passages can be metallic, non-metallic, or any other suitable material, which is compatible with fluid flowing through it. A housing 918 is provided to ensure the air passes in closed contact with contacting discs 1. A fan 915 is provided to force/induce the air over the discs of the dehumidifier. The heat transfer fluid is supplied through conduit 910 to the passages 916 wherein it exchanges heat with the LD in the trough and leaves through conduit 912. A device 924 is provided to rotate the contacting disc assembly and is supported on support 923.

Process described in "Q" is executed when conduit 939 in thermal contact with trough 3 carries air as cooling fluid. Process described in "S" is executed when conduit 939 in thermal contact with trough 3 carries chilled water as cooling fluid.

Processes described in "P" deliver dehumidified air which can be used for drying applications. Figure 5 shows the system for drying using LD. Regenerated LD leaves the regenerator 952 through conduit 936, flows to dehumidifier 934 and leaves as weak LD through conduit 937 back to the regenerator for regeneration. Dehumidified air flows from dehumidifier 934 through conduit 942 and is blown into the dryer 955 by blower 956. This air leaves the dryer as humidified air through conduit 954 after picking up moisture from the product to be dried and flows back into dehumidifier 934. The dehumidifier 934 may be located at distant locations in which case the conduits 936 and 937 are sufficiently long to service the dehumidifiers. The LDs are selected from solutions exhibiting boiling point elevation of at least 5°C. The CAULD functions at temperatures at least 3°C lower than the saturation temperature of the LD at a given concentration.

The invention is now illustrated with a non-limiting example. Example

RESULTS DEMONSTRATING DIABATIC DEHUMIDIFICATION PROCESS

A diabatic dehumidifier was fabricated and tested for dehumidification of ambient air using aqueous solution of calcium chloride as LD. It consists of discs made of aluminium mesh. The discs are of 150 mm diameter, with circumferential lip and dimples. The discs are mounted on an aluminium shaft of diameter 9.5 mm. The discs are placed in a semi hexagonal aluminium trough 850 mm (length) x 200 mm (width) x 210 mm (height). It incorporates 600 m²/m³ surface density, when maintaining 2 mm gap between the discs. Dehumidifier was covered with a plastic housing. A fan with an impeller length 850 mm and diameter of 101.6 mm is used to move air through the dehumidifier. The discs are made to rotate at 5 rpm using an electric motor. The cooling of LD in the trough was done by circulating water in the passages which are in thermal contact with the trough. Table 1 shows experimental results of the dehumidifier for dehumidification of ambient air. Experimentl was carried out with water circulating in tubes which were in thermal contact with trough and Experiment 2 was carried out with chilled water circulating in tubes which were in thermal contact with trough The specific humidity of the air reduced by 5 g/kg of dry air while RH changing from 68% to 46%. The specific moisture removal from the ambient air is 2.48 kg/kWh heat input. The primary energy requirement is reduced to 60% of that required by VCRS for equivalent moisture removal. The outgoing air was bubbled through a dilute solution of sulphuric acid to detect calcium and it was found that there was no visible formation of salt calcium sulphate after a period of 20 minutes thus showing that the outgoing air is free of LD.

Compared to conventional VCRS, electrical power consumption is significantly reduced in the present invention. The system using CAULD is modular and can be scaled up/down to meet any air conditioning load. It operates with lower pressure drops and low desiccant flow rates compared to conventional desiccant cooling systems. The main advantages of the CAULD is that the outgoing air stream is free of desiccant as compared to the conventional LD based air conditioning, use of low grade heat sources and possibility of recovering water. This is possible by the appropriate design of the dehumidifier, regenerator, liquid-liquid heat exchanger air-air heat exchangers and other components of CAULD. Significant reduction in weight and cost can be achieved with the use of alternate materials such as plastics and eliminates any problems due to corrosion of the dehumidifier/regenerator as in conventional systems. The system is compact, low weight and techno-economically viable for air-conditioning. Table 1: Experimental Results of Diabatic Dehumidification System

Parameters Experiment I Experiment II

Air in, DB/WB (°C ) 32/31 34/29

Specific humidity, g/kg. da) 28.5 23.5 ₅

Air out, DB WB (°C ) 34/30 37/27

Specific humidity, g/kg da) 25.5 18.5

Moisture removed (g/kg da) 3.0 5.0

Air flow (kg/s) 0.4 0.4

Moisture removed (kg/h) 4.32 7-2 ₁₀

Power input (kW) 3.4 2.9

Moisture removal (kg/kWh) 1.27 2.48

Solution in/out (°C) 64/34 36/38

LT Regenerator in/out (°C) 97/77 95/85

Solution flow (kg/min) 0.8 0.8 ₁₅

Air flow/ LD flow 15 15

Remarks With ambient water With cooled water circulated in tubes in circulated in tubes in thermal contact with thermal contact with trough trough 20

Claims

CLAIMSWe claim:

1. A Process for Energy Efficient Conditioning of Air Using Liquid Desiccant (CAULD) comprising of: o A diabatic/adiabatic dehumidifying process wherein air is brought in contact with the LD

© Single/multi stage regeneration, to regenerate the LD o Passing air through dehumidifier and EC © Optional diabatic/adiabatic humidification o Optional process to recycle heating and/or cooling effects between air streams and/or LD streams

Optional Evaporative cooling of air stream(s)

Cooling of LD with air/water/air water mixture while it is dehumidifying air stream(s)

Optional removal of excess water generated and recovered • Recirculation of LD

2. Adiabatic dehumidification process as claimed in Claim 1 wherein: Air is brought in contact with the LD by means of a contacting device LD regenerated in single/multi stage regeneration process Heat is recycled between LD streams • Excess water generated is recovered

LD is recirculated by suitable means

3. Diabatic dehumidification process as claimed in Claim 1 wherein: Air is brought in contact with the LD by means of a contacting device LD in dehumidifier is cooled by ambient air/ water/air water mixture/chilled fluid • LD regenerated in single/multi stage regeneration process

Heat is recycled between LD streams Excess water generated is recovered

• LD is recirculated by suitable means

4. A process of evaporative cooling as claimed in Claim 1 wherein: o Air is brought in contact with the water by means of contacting device o Suitable water level is maintained in contacting device

5. The CAULD as claimed in claim 1 comprising of:

• Adiabatic dehumidification of air as claimed in Claim 2

• Sensible cooling of air • Evaporative cooling of air as claimed in Claim 4

6. The CAULD as claimed in claim 1 comprising of: o Diabatic dehumidification where LD is cooled by air as claimed in claim 3 o Sensible cooling of air

7. The CAULD as claimed in claim 1 comprising of:

8. The CAULD as claimed in claim 1 comprising of:

• Diabatic dehumidification where LD is cooled by chilled fluid as claimed in claim 3

9. The processes as claimed in Claims 1-8 wherein outgoing air is free of LD.

10. The processes as claimed in Claims 1 ,5-7 wherein sensible cooling of dehumidified air is enabled by air leaving conditioned space/ambient air

11. The processes as claimed in Claims 1 ,3,7 wherein air stream leaving the conditioned space or ambient air is humidified and the cooling effect achieved thereby is used to cool the LD

12. The processes as claimed in Claims 1 ,5-7 wherein direct evaporative cooling process follows dehumidification process ensuring out going air is free of LD

13. The CAULD as claimed in Claims 1 ,5-7 wherein air is induced / forced over dehumidifier followed by evaporative cooler using a suitable means

14. The processes as claimed in Claims 2-3 wherein air is induced / forced over dehumidifier.

15. The CAULD as claimed in Claims 1-8 wherein regeneration of LD is enabled in a single stage or in multiple stages

16. The CAULD as claimed in Claim 15 wherein water is recovered during multistage regeneration of LD

17. The CAULD as claimed in Claims 1-3,5-8 wherein recovered water is used for selective rehumidification of air after it is deep dehumidified using LD

18. The CAULD as claimed in Claims 1-3,5-8 wherein recovered water is used for applications such as drinking, food processing or for any other suitable use

19. The CAULD as claimed in Claims 1-3,5-8 wherein heat in regenerated LD is recovered to preheat the LD before regeneration

20. The CAULD as claimed in Claims 1-3,5-8 wherein multiple dehumidifiers placed at distant locations are fed with LD regenerated at central location/(s)

21. The CAULD as claimed in Claims 1-3,5-8 wherein the heat source to the LTR is low temperature waste heat from power stations, engine cooling fluids or any waste heat source

22. The CAULD as claimed in Claims 1-3,5-8 wherein LD is regenerated at centralised location/(s), distributed to distant locations and retrieved for regeneration from distant locations

23. A process of drying wherein conditioned air is circulated over/through the product to be dried.

24. The CAULD as claimed in Claims 1 ,3,7 wherein water is circulated by gravity and pump and combination thereof, between diabatic dehumidifier and indirect EC 25. The CAULD as claimed in Claims 1 ,5,6 wherein recycling of cooling effect is enabled by removal of air from conditioned space 26. The CAULD as claimed in Claims 1-8 wherein the dehumidifiers/EC's is placed in series when larger quantity of conditioned air is needed or in parallel when more dehumidification is required 27. The LD as claimed in Claims 1-26 are selected from solutions exhibiting boiling point elevation of at least 5°C 28. The CAULD as claimed in Claims 1-26 functions at temperatures at least 3°C lower than the saturation temperature of the LD at a given concentration