FORM - 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION (Section 10, rule 13)
"AIR COOLED ABSORPTION REFRIGERATING MACHINE"
Thermax Limited
with Corporate office at Thermax House, 4 Pune-Mumbai Road, Shivajinagar, Pune 411005,
Maharashtra, India.
an Indian Company registered under the provisions of the Companies Act, 1956,
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED: -
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FIELD OF THE INVENTION
This invention relates to an absorption refrigerating machine.
Particularly, this invention relates to an indirectly air cooled or high temperature water cooled double effect absorption refrigerating machine.
Even more particularly, this invention relates to an indirectly air cooled or High temperature water cooled double effect absorption refrigerating machine consisting of two shell concept i.e. two evaporators, two absorbers, a low temperature generator, a high temperature generator, solution heat exchangers and two new regenerative heat exchangers designed to give low generator temperature and better Coefficient of Performance.
BACKGROUND OF THE INVENTION
The invention mentioned here relates to an air-cooled absorption refrigerating machine, particularly to an indirectly air-cooled machine operating at higher cooling water temperature. The cycle uses a two-shell concept as mentioned before.
A similar two-shell concept has been used in prior art for producing -5 °C brine. In the construction disclosed in this prior art publication, the dilute absorbent solution after leaving the second absorber flows in parallel to Low temperature generator & High temperature generator. A schematic diagram of this cycle is shown (Fig. 2).
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In the cycle disclosed in this prior art, refrigerant sprayed on the Low-Pressure Evaporator tubes (EVAl) removes heat from brine flowing in the tubes thus cooling it to -5°C. The refrigerant vapours so formed are absorbed into the absorbent solution spraying in Low Pressure Absorber (ABS1). Due to dilution of Absorbent solution heat of dilution is released which has to be removed using cooling water. In turn the cooling water gets heated.
This heated cooling water is fed to High-Pressure Evaporator Tubes (EVA2) where it is cooled to the desired cooling water inlet temperature of Low Pressure Absorber (ABS1). For achieving this cooling, Concentrate LiBr Solution is fed to High Pressure Absorber (ABS2). Here it absorbs refrigerant vapours released in EVAl and gets diluted. This intermediate solution is then fed to ABS1.
The dilute solution leaving ABS1 is then passed on in series through three heat exchangers where it exchanges heat with Strong solutions. Before it enters the Fourth (high temperature) heat exchanger the flow is bifurcated to Low Temperature Generator (LTG) and High Temperature Generator (HTG).
In HTG the solution is concentrated using external Heat source (steam). The water vapours released in the HTG act as heat source to LTG. Both the concentrated streams leaving LTG & HTG are mixed before entering the heat exchangers. After losing heat in these heat exchangers the absorbent solution is sprayed back in ABS2, thus completing the cycle.
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If the same cycle as used in the prior art publication were used for the air-cooled application i.e. parallel flow of Dilute Absorbent solution to LTG & HTG, the generator temperature would be high. Also high generator temperature increases corrosion.
To avoid this, the solution first flows to Low temperature generator and then to high temperature generator. This ensures low temperature in the generator. Also as seen in the diagram, there are two new regenerative heat exchangers used for the first time in absorption cycle, which improve the Coefficient of Performance by 10%.
PRIOR ART
An U.S. patent application No. 7,225,634 claiming A triple effect absorption refrigerating machine comprising: a high temperature regenerator; an intermediate temperature regenerator; a low temperature regenerator; a condenser; an absorber; an evaporator; an auxiliary regenerator; an auxiliary absorber; and a path for interconnecting these devices, said triple effect absorption refrigerating machine further comprising: a high concentration circulation path for circulating a solution among said absorber, said auxiliary regenerator, said intermediate temperature regenerator and said high temperature regenerator; and a low concentration circulation path for circulating a solution between said auxiliary absorber and said low temperature regenerator, wherein said triple effect absorption refrigerating machine further comprises: a path for guiding a refrigerant vapor generated in said auxiliary regenerator to said auxiliary absorber; a path for guiding a refrigerant vapor generated in said intermediate temperature regenerator to said low temperature regenerator and said auxiliary regenerator in the heating sections thereof; and a path for guiding a refrigerant vapor generated in said high temperature regenerator to said intermediate temperature regenerator in the heating section thereof.
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An U.S. patent application No. 6,993,933 claims, An absorption refrigerating machine comprising: a high temperature regenerator, a low temperature regenerator, a condenser, an evaporator, an absorber, a low temperature heat exchanger for performing heat exchange between absorbent solutions entering and leaving the absorber, a high temperature heat exchanger for performing heat exchange between absorbent solutions entering and leaving the high temperature regenerator, a first heat recovery device for collecting heat remaining in a heat exhaust fluid discharged from the high temperature regenerator after heating an absorbent solution in the high temperature regenerator through heat exchange between the heat exhaust fluid and the absorbent solution leaving the absorber and flowing into the low temperature heat exchanger, and a second heat recovery device upstream, with respect to the heat exhaust fluid, of the first heat recovery device for collecting heat remaining in the heat exhaust fluid through heat exchange between the beat exhaust fluid and absorbent solution discharged from the low temperature heat exchanger, and flowing into the high temperature heat exchanger.
An U.S. patent application No. 6,581,406, claims, an absorption diffusion type refrigerating structure, comprising: a concentrated ammonia aqueous solution tank for receiving concentrated ammonia aqueous solution; a concentrated ammonia aqueous solution pipe for guiding out concentrated ammonia aqueous solution from said concentrated ammonia aqueous solution tank, another end of said concentrated ammonia aqueous solution pips having an opening; a diluted ammonia aqueous solution pipe sleeved outside said concentrated ammonia aqueous solution pipe and passing across the other end of said concentrated ammonia aqueous solution pipe; a generator having a heater, said heater
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abutting on said diluted ammonia aqueous solution pipe so that said diluted ammonia aqueous solution pipe can conduct heat to said concentrated ammonia aqueous solution pipe to let said concentrated ammonia aqueous solution pipe generate vapor; a separator for separating vapor and liquid, said separator being formed between the open end of said concentrated ammonia aqueous solution pipe and said diluted ammonia aqueous solution pipe; a rectifier connected with said diluted ammonia aqueous solution pipe to let part of the vapor leaving said separator condense into liquid and then flow back; a condenser connected with said rectifier to let vapor condense into liquid; an ammonia liquid pipe, one end thereof being joined at a distal end of said condenser, and the other end thereof being an opening, a liquid-shutting loop forming between the two ends of said ammonia liquid pipe; a diluted ammonia aqueous solution reflow pipe led out from said diluted ammonia aqueous solution pipe near said concentrated ammonia aqueous solution tank; an absorber, having a lower end thereof being connected with said concentrated ammonia aqueous solution tank and said diluted ammonia aqueous solution reflow pipe, the joining position of said absorber with said diluted ammonia aqueous solution reflow pipe being lower than said opening of said concentrated ammonia aqueous solution pipe in said separator, said absorber being used to let diluted ammonia aqueous solution react to become into concentrated ammonia aqueous solution, said absorber being connected*with an airway, said airway being disposed downwards, ammonia vapor and hydrogen gas passing through said absorber entering said airway to let ammonia vapor condense into ammonia liquid, said airway being connected with an ammonia liquid guide pipe, the other end of said ammonia liquid guide pipe being connected to a region below the liquid face of said concentrated ammonia aqueous solution tank; a hydrogen pipe, one end thereof being connected to the other end of said airway and disposed upwards, the other end thereof being an opening; and an evaporator having a pipeline, the upper end of said pipeline being closed, the lower end of said pipeline being
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connected with said concentrated ammonia aqueous solution tank, a rear section of said hydrogen pipe and said ammonia liquid pipe being inserted into said pipeline of said evaporator from near the lower end and extending to the closed end along said pipeline, the open end of said ammonia liquid pipe being lower than the position where said ammonia liquid pipe joins the distal end of said condenser, ammonia liquid and hydrogen gas being simultaneously released out from the closed end of said evaporator to let ammonia liquid absorb heat and perform reaction of heat exchange, the generated ammonia vapor and hydrogen gas then flowing back to be discharged into said concentrated ammonia aqueous solution tank.
An U.S. patent application No. 6,845,631, claims, an Absorption refrigerator (1) comprising: a cabinet having outer walls (2,3,4,5,6) and at least one door (7,8), said cabinet enclosing a low temperature storage compartment (9) and a higher temperature storage compartment (10), said compartments being essentially sealed from each other and separated by a partition wall (11), said partition wall being arranged inside the cabinet and generally perpendicular to a first wall (2) of said outer walls, and an absorption refrigerating system including an evaporator tube (20) comprising a first evaporator tube section (21) for cooling the low temperature compartment and a second evaporator tube section (22) for cooling the higher temperature compartment, said second evaporator tube section being arranged downstream of said first evaporator tube section with respect to a direction of flow of a coolant, wherein a substantial portion of said first evaporator tube section (21) is arranged generally in parallel with said partition wall (11), and wherein said substantial portion of the first tube section (21) includes two non-coaxial tube portions (21a) the axes of said tube portions together defining a general extension plane of said substantial portion of the first
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evaporator section said general extension plane being arranged generally in parallel with said partition wall (11)
An U.S. patent application No. 6,442,964, claims, an absorption refrigerating machine using plate type heat exchangers at least in an absorber and a condenser, characterized in that cooling water is supplied in parallel with each other respectively to said plate type heat exchanger in said absorber and said plate type heat exchanger in said condenser, and amounts of cooling water distributed to said absorber and said condenser are determined mainly based on fluid resistance of each of said plate type heat exchangers.
An U.S. patent application No. 6,422,033, claims, an absorption type refrigerating apparatus having an evaporator in which a refrigerant is stored, an absorber for absorbing a refrigerant vapor generated^ in the evaporator with the use of an absorbent solution, a regenerator for heating up the absorbent solution to extract the refrigerant vapor and thus recover a concentration of the absorbent in the solution, and a condenser for condensing the refrigerant vapor extracted in the regenerator before transferring back the same to the evaporator, wherein the condenser has a reduction unit provided within the interior thereof, said reduction unit holding fundamentally a metal oxide which oxidizes hydrogen gas to water, and means for conducting which hydrogen gas being produced during the absorption refrigerating cycle operation into contact with said metal oxide
An U.S. patent application No. 6,282,918, claims, an Absorption refrigerating apparatus (18) of steel, where
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a dissolvable refrigerant by means of an absorption liquid, circulates through in turn a boiler (36) where refrigerant is liberated from the absorption liquid;
a condenser (50) where the refrigerant condenses;
an evaporator (16) where the refrigerant evaporates;
an absorber (60) where the refrigerant is absorbed by the absorption liquid, and
an absorber vessel (32) for collecting the absorption liquid, from which absorber vessel (32) the absorption liquid circulates back to the boiler (36), where the absorption liquid is heated in a pump pipe (42) so that the refrigerant is again liberated from the absorption liquid, characterized in that the pump pipe (42) is made of a more corrosion resistant material, than the steel material used in the condenser (50), the evaporator (16), the absorber (60) and in the absorber vessel (32), and that in the boiler (36) there are no joints between different materials, which can cause galvanic corrosion
In the cycle disclosed in the prior art, refrigerant sprayed on the low-pressure evaporator tubes (EVA1) removes heat from brine flowing in the tubes thus cooling it to -5°C. The refrigerant vapours so formed are absorbed into the absorbent solution spraying in low pressure Absorber (ABS1). Due to dilution of Absorbent solution heat of dilution is released which has to be removed using cooling water. In turn the cooling water gets heated.
This heated cooling water is fed to high-pressure evaporator tubes (EVA2) where it is cooled to the desired cooling water inlet temperature of ABS1. For achieving this cooling, Concentrate LiBr Solution is fed to ABS2. Here it absorbs refrigerant vapours released in EVA1 and gets diluted. This intermediate solution is then fed to ABS1.
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The dilute solution leaving ABS1 is then passed on in series through three heat exchangers where it exchanges heat with Strong solutions. Before it enters the Fourth (high temperature) heat exchanger the flow is bifurcated to Low temperature generator (LTG) and High temperature generator (HTG).
In HTG the solution is concentrated using external Heat source (steam). The water vapours released in the HTG act as heat source to LTG. Both the concentrated streams leaving LTG & HTG are mixed before entering the heat exchangers. After losing heat in these heat exchangers the absorbent solution is sprayed back in ABS2, thus completing the cycle.
If the cycles proposed in the prior art were used for the air-cooled application i.e. parallel flow of Dilute Absorbent solution to LTG & HTG, the generator temperature would be high and the high generator temperature increases corrosion.
Also, the above proposed cycles and systems are complex and are lacking in providing a integrated and high quality self-contained air-cooled machines (chillers). Also, the use of cycles mentioned the prior art i.e. parallel flow of Dilute Absorbent solution to LTG & HTG creates high temperature in the generator. This high generator temperature increases not only the chances of corrosion but also the actual corrosion.
OBJECTS OF THE INVENTION
The objective of this invention is to provide an improved chiller.
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Another objective of this invention is to avoid creating high temperature in the generator thereby avoid corrosion.
Another objective of this invention is to provide low temperature in the generator by allowing the solution to first flows to Low temperature generator and then to high temperature generator thereby avoiding corrosion.
Another objective of this invention is to provide two new regenerative heat exchangers used in absorption cycle which improve the Coefficient of Performance by 10%.
Another objective of this invention is to provide air cooled or High temperature water cooled machine which has an inbuilt control system that measures the ambient air temperature and changes the two-shell concept to normal cycle automatically, thus giving twice the Coefficient of Performance.
These and other objects and advantages of the present invention will become more apparent from the detailed description thereof taken with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1: Cycle diagram of Air-cooled Absorption Refrigeration Machine
Numeral 1: Low Pressure Evaporator (EVA1) Numeral 2: Low Pressure Absorber (ABS1) Numeral 3: Higher Pressure Evaporator (EVA2)
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Numeral 4: High Pressure Absorber (ABS2)
Numeral 5: Drain Heat Exchanger (DHE)
Numeral 6: Flash Heat Exchanger (FHE)
Numeral 7: Low Temperature Heat Exchanger 1 (LTHE) Numeral 8: Low Temperature Heat Exchanger 2 (LTHE) Numeral 9: High Temperature Heat Exchanger (LTHE) Numeral 10: Low Temperature Generator (LTG)
Numeral 11: High Temperature Generator (HTG)
Numeral 12: Condenser (COND)
Figure 2: Cycle diagram of-5 degree C brine producing cycle used by prior art publications
Figure 3: cycle diagram describing the inbuilt control logic for switching over from Air
cooled or High temperature water cooled to Normal Cycle of Operation.
Numeral 1: Valve 1
Numeral 2: Valve 2
Numeral 3: Valve 3
Numeral 4: Valve 4
Numeral 5: Valve 5
Numeral 6: Valve 6
BRIEF SUMMARY OF THE INVENTION
The proposed invention relates to an indirectly air cooled or High temperature water cooled double effect absorption refrigerating machine consisting of two shell concept i.e. two
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evaporators, two absorbers, a low temperature generator, a high temperature generator, solution heat exchangers and two new regenerative heat exchangers designed to give low generator temperature and better Coefficient of Performance.
The endeavor of this proposed invention is to provide low temperature in the generator by allowing the solution to first flows to Low temperature generator and then to high temperature generator thereby avoiding corrosion.
DETAILED DESCRIPTION OF THE INVENTION
It is an object of the present invention to use the two-shell concept for indirectly Air-cooled absorption machines operating at high ambient temperatures, and to achieve this refrigeration effect at lower generator temperatures and higher COP, as compared to standard double effect machines operating at such higher cooling water temperatures. Figure 1 gives the schematic cycle diagram of the Air-cooled cycle diagram. In this cycle the Refrigerant is sprayed in the Low Pressure Evaporator (EVA1) which extracts heat from chilled water flowing in the evaporator tubes (cooling chilled water from 12-7 °C) and gets converted into refrigerant vapours. The refrigerant vapours so released are then absorbed in the concentrate LiBr solution (64%) which are sprayed in Low Pressure Absorber (ABSl). As a result of this, the concentrate LiBr solution gets diluted to an intermediate concentration (58%).
Water at approximate 33 °C is then fed to the ABSL tubes to remove the heat of the dilution. This water leaves ABSl at around 37 °C and is then fed to the High-Pressure Evaporator (EVA2). In EVA2, this water is cooled to 33 °C and re-circulated back to ABSl.
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Meanwhile, the intermediate concentration LiBr (58%) solution from ABS1 is passed from a series of heat exchangers before it is sprayed in ABS2. The intermediate concentrate LiBr solution from ABSL is first passed to FHE where it exchanges heat with the Condensate from condenser. The Intermediate solution is then passed to LTHE2 where it exchanges heat with concentrate LiBr solution. This heated solution is then sprayed in ABS2. Here, the refrigerant vapours released in the EVA2 are absorbed and the dilute LiBr solution (54%) so formed leaves the absorber section. Water at 55 °C (i.e. output from Dry cooler) is fed to ABSH to remove the heat of dilution of LiBr solution.
The dilute solution leaving absorber section is then passed through heat exchangers where it exchanges heat with concentrate LiBr solution in Low Temperature Heat Exchanger (LTHE) and with condensed High Temperature Generator (HTG) vapours in DHE. These heated dilute solutions are then mixed and fed to Low Temperature Generator (LTG).
The dilute solution fed to LTG is concentrated to an intermediate concentration (57%) by making use of HTG vapours as heat source. The intermediate concentration solution is then fed to High Temperature Heat Exchanger (HTHE). Here it exchanges heat with concentrate LiBr Solution before entering HTG. The solution is concentrated to approx. 64% in this direct (oil) fired generator. The concentrate solution leaving the HTG is then fed in series to HTHE, LTHE and LTHE2 as heating medium and is then returned to Low Pressure Absorber.
The refrigerant vapours released in LTG pass through the eliminators and are condensed in the condenser. The HTG vapours after losing heat in LTG and DHE get condensed and are fed back to condenser. Water leaving ABSH at around 59°C is fed as
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cooling medium to Condenser. This water condenses the refrigerant vapours and leaves the condenser at around 63 °C. The condensed refrigerant is first fed to High Pressure Evaporator and then to Low Pressure Evaporator, thereby competing the cycle
One of the major advantages of this cycle is it has an inbuilt control system that measures the ambient air temperature and changes the two-shell concept to normal cycle automatically, thus giving twice the COP as indicated in Figure. 3.
When the measured ambient air temperature is high (-45 °C) valves 2 & 6 (Numeral 2 & 6) would be opened and 1, 3, 4, 5 (Numeral 1,3,4 & 5) would be closed by the internal control system of the chiller. Thus the machine would work under the Air-cooled cycle. If the measured air temperature is low (-30-35 °C i.e. the cooling water temperature is in the range of 32 - 40 °C) the machine would give better performance in standard cycle. To achieve this, valves 2 & 6 would be closed and 1, 3, 4 & 5 would be opened. By doing this, both chilled water and cooling water would flow in parallel to both the shells and thus work is a standard lower shell.
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We Claim,
1. An air cooled, double effect absorption refrigerating machine in which water is used as refrigerant and a water solution of salt is used as an absorption solution, said machine comprising of:
a) First Evaporator, operating at lower pressure
b) First Absorber, for absorption of refrigerant vapors produced in first evaporator
c) Second Evaporator, operating at higher pressure and cooling the water leaving first absorber
d) Second Absorber, for absorption of refrigerant vapors produced in second evaporator, operating at higher cooling water temperatures
e) Solution Heat Exchangers as LTHE2, FHE, HTHE, LTHE, DHE
f) Condenser, for condensing the regenerated refrigerant using higher temperature cooling water
g) Low temperature Generator
h) High temperature Generator
i) Inter connecting piping between all the heat exchangers mentioned above,
j) Inbuilt logic, controls and valves for operation of both air-cooled and normal
cycle on the basis of ambient air temperature.
2. An absorption refrigerating machine as claimed in claim 1, wherein

a. heated water leaving low-pressure absorber is fed to high-pressure
evaporator tubes where it is cooled to a temperature which can be re
circulated to low pressure absorber tubes.
b. The cooling water intercirculation pipes complete with pump and valves,
which connects the low-pressure absorber and high-pressure evaporator.
3. An absorption refrigerating machine according tc claim 1, wherein
a. Concentrate absorbent solution is first sprayed in low pressure absorber,
absorbs the refrigerant vapors and gets diluted to an intermediate
concentration
b. This intermediate concentration is then sprayed onto the high-pressure
absorber tubes, absorbs the refrigerant vapors and gets further diluted.
c. The pipes, valves, pump connecting the high-pressure and low-pressure
absorber.
4. An absorption refrigerating machine according to claim 1, wherein
a. Two new regenerative solution heat exchangers, FHE and LTHE2 in
series, are used in between the absorbent solution passage from low-
pressure absorber to high-pressure absorber.
b. The Flash heat exchanger (FHE) where intermediate absorbent solution
exchanges heat with the refrigerant coming from condenser.

c. The Low temperature heat exchanger (LTHE2) where intermediate
absorbent solution is heated using strong absorbent solution coming from
HTG.
d. The piping and valve assembly connecting these heat exchangers thereby
giving an improvement in Coefficient of performance by 10%.
5. An absorption refrigerating machine according to claim 1, wherein
a. The passage of dilute absorbent solution to the low temperature generator
(LTG) first, thereby reducing the generator temperature.
b. The passage of moderately concentrated solution from LTG to high
temperature generator (HTG) whereby, the absorbent solution reaches its
maximum concentration.
6. An absorption refrigerating machine according to claim 1, wherein
a. The passage of dilute absorbent solution through Low temperature heat
exchanger (LTHE) and Drain heat exchanger (DHE) in parallel, where it
exchanges heat with concentrate absorbent solution and Refrigerant
leaving LTG respectively.
b. The passage of moderately concentrated absorbent solution through High
temperature heat exchanger (HTHE), where it exchanges heat with
concentrate absorbent solution leaving HTG.
7. An absorption refrigerating machine according to claim 1, wherein

a. Auto - operated valves placed in the piping
b. Instruments measuring the ambient air temperature and transferring the
same to the controller.
c. Control logic and software operating the valves for switching over from
Air-cooled cycle to Normal cycle and vice versa depending on the
measured ambient air temperature, thereby giving twice the COP as air
cooled cycle during standard mode of operation.

ABSTRACT
A high temperature water cooled, double effect absorption refrigerating machine (Fig. 1) in which water is used as refrigerant and a water solution of salt is used as an absorption solution, said machine comprising of Low Pressure Evaporator (Fig 1, Numeral 1), operating at lower pressure, a High Pressure Absorber (Fig 1, Numeral 4), for absorption of refrigerant vapors produced in Low Pressure Evaporator, a High Pressure Evaporator (Fig 1, Numeral 3)v operating at higher pressure and cooling the water leaving Low Pressure Absorber (Fig 1, Numeral 2), a High Pressure Absorber (Fig 1, Numeral 4), for absorption of refrigerant vapors produced in High Pressure Evaporator, operating at higher cooling water temperatures, a Solution Heat Exchangers as Low Temperature Heat Exchanger 1 (Fig 1, Numeral 7), Flash Heat Exchanger (Fig 1, Numeral 6), High Temperature Heat Exchanger (Fig 1, Numeral 9), Drain Heat Exchanger (Fig 1, Numeral 5), a Condenser (Fig 1, Numeral 12), for condensing the regenerated refrigerant using higher temperature cooling water, a Low Temperature Generator (Fig 1, Numeral 10) and a High Temperature Generator (Fig 1, Numeral 11) along with an Inter connecting piping between all the heat exchangers which has inbuilt logic (Fig. 3), controls and valves (Fig 3, Numeral 1-6), for operation of both air-cooled and normal cycle on the basis of ambient air temperature.