FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
THE PATENTS RULES, 2006
COMPLETE
Specification
(See Section 10 and Rule 13)
TRIPLE-EFFECT ABSORPTION REFRIGERATION SYSTEM
THERMAX LIMITED
an Indian Company
of D-13, MIDC Industrial Area, R.D. Aga Road,
Chinchwad, Pune - 19,
Maharashtra, India
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF DISCLOSURE
The present disclosure relates to absorption refrigeration systems.
Particularly, the present disclosure relates to a triple-effect absorption
refrigeration system.
DEFINITIONS OF TERMS USED IN THE SPECIFICATION
The term "desorber" used in the specification means the equipment in which an absorbed substance is converted to a vapor state and released by extracting heat from a liquid.
The term "absorber" used in the specification means the equipment in which a vapor is absorbed by contact with a liquid.
The term "heat of absorption" used in the specification means the heat released during the exothermic absorption of a vapor in a liquid.
The term "low temperature heat exchanger" used in the specification means the heat exchanger operated over a temperature range of 25 - 100 °C being adapted to transfer heat between two liquids.
The term "low temperature generator" used in the specification means a generator operated over a temperature range of 70 - 100 °C being adapted to generate vapors.
The term "low temperature resorber" used in the specification means a resorber operated over a temperature range of 25 - 54 °C being adapted to absorb vapors.

The term "medium temperature heat exchanger" used in the specification means the heat exchanger operated over a temperature range of 64 - 120 °C being adapted to transfer heat between two liquids.
The term "medium temperature generator" used in the specification means a generator operated over a temperature range of 100 - 150 °C being adapted to generate vapors.
The term "medium temperature resorber" used in the specification means a resorber operated over a temperature range of 64 - 100 °C being adapted to absorb vapors.
The term "high Temperature Heat Exchanger" used in the specification means the heat exchanger operated over a temperature range of 100 - 170 °C being adapted to transfer heat between two liquids.
The term "high temperature generator" used in the specification means a generator operated over a temperature range of 145 - 175 °C being adapted to generate vapors.
The term "high temperature resorber" used in the specification means a resorber operated over a temperature range of 100 - 150 °C being adapted to absorb vapors.

BACKGROUND
Absorption refrigeration systems are heat driven refrigeration machines in which a secondary fluid, the absorbent, absorbs a primary fluid, a gaseous refrigerant, which has been vaporized in an evaporator, to provide cooling. Typically, water is used as the refrigerant and lithium bromide (LiBr) solution is used as the absorbent. Other refrigerant-absorbent pairs (solutions) have also been used in absorption refrigeration systems.
In a single-effect absorption refrigeration system, refrigerant vapors are produced in an evaporator at a temperature below that of the heat load. The refrigerant vapors are exothermically absorbed by a concentrated absorbent solution entering the absorber, wherein the absorber and the evaporator are provided in communication with each other. The heat of absorption produced during the exothermic process is transferred to a heat sink, such as cooling water, at the absorber. The dilute absorbent solution is pumped to a generator where it is concentrated again and returned to the absorber. External heat is provided to the generator to supply the energy required to separate the refrigerant from the absorbent. The separated refrigerant is condensed in a condenser and returned to the evaporator while the concentrated absorbent is returned to the absorber. A heat exchanger can be provided between the absorber and the generator, for exchanging heat between the dilute absorbent solution and the concentrated absorbent solution. This process is generally carried out at two pressures: a lower pressure in the evaporator-absorber section, and a higher pressure in the generator-condenser section.
The co-efficient of performance (COP) of a single-effect absorption refrigeration system is typically about 0.5 to 0.7. A COP of above 1.0 in a

single-effect absorption refrigeration system cannot be achieved because the heat required to generate one pound of refrigerant is not less than the heat taken up when the refrigerant evaporates in the evaporator. The COP of the absorption refrigeration system can be increased by using a double-effect absorption refrigeration system, wherein two generators are used; a first generator operated at high temperature and pressure and heated by an external heat source, and a second generator operated at low temperature and pressure and heated by condensation of the vapors from the first generator, wherein the condensate from both the generators is transmitted to the evaporator. Therefore, the energy from the external heat source is effectively used, thereby increasing the overall system efficiency. As compared to a single-effect absorption refrigeration system, the COP of a double-effect absorption refrigeration system is typically in the range of 1.0 to 1.2.
With growing interests in more energy-efficient absorption refrigeration systems, recently substantial effort has been devoted towards triple-effect absorption refrigeration systems, where using a triple-effect absorption refrigeration system a COP of 1.5 to 2 can be achieved. However, numerous problems have been encountered when operating a triple-effect absorption refrigeration system. The high temperature generator must be maintained at a temperature well in excess of 200 °C. This high temperature can be achieved by employing direct fuel firing; however, the conventional LiBr solution becomes highly corrosive at such high temperatures. Further, the triple-effect absorption refrigeration systems are complicated and the costs involved in operating them are high. One approach to achieve triple-effect absorption refrigeration is by providing a third pressure stage, but this might result in increase of the maximum pressure to well above the atmospheric pressure, thus involving code

restrictions such as IBR associated with pressure vessels. This will reduce the acceptability of the system in the market. The other approach is to add a concentration stage, but this requires a much wider solubility field than is possible with conventional LiBr.
Several attempts have been made to alleviate some of the problems related to triple-effect absorption refrigeration systems, some of these disclosures are listed in the prior art below:
US6324865 discloses a triple-effect absorption chiller comprising one or more vapor compressors connected to a medium-temperature generator (GM), a high-temperature generator (GH), or an evaporator, to compress the refrigerant vapors coming from the generators or the evaporator, lowering the temperature of the high-temperature generator to a range below 170 °C, thus preventing corrosion of the metal parts of the chiller due to high temperature in the high-temperature generator.
US5946937 discloses a triple-effect absorption chiller comprising a first absorption circuit for operation at a first temperature range and a second absorption circuit for operation at a second temperature range, wherein the second operation circuit has a maximum temperature lower than the relative temperature of the first operation circuit; the chiller further comprises a common evaporator connected operatively to the first absorption circuit and the second absorption circuit, being in heat exchange relation to an external heat load.

US5653I16 discloses a triple-effect absorption cycle comprising two hermetic loops: a first loop is a conventional LiBr double-effect loop, and a second loop is a single-effect loop which overlaps the high pressure portion of the first loop and exchanges heat at three locations, wherein each loop further comprises: an absorber, a condenser, an evaporator, and an absorbent solution received there through which exchanges heat with the condensate. The absorption cycle as disclosed in US5653116 primarily aims at overcoming limitations such as super-atmospheric pressures and/or low pressure absorbers of a conventional triple-effect absorption cycle.
US5335515 discloses a triple-effect absorption cycle comprising a first, second and third generators, and a first, second, and third condensers; both operatively communicating with each other and operating at successively high temperatures; further comprising heat exchange means for extracting energy there between. The peak operation temperature of the triple-effect absorption cycle disclosed in US5335515 is lower than that of a conventional triple-effect absorption cycle, thus, reducing the fluid crystallization requirements in the third stage generators.
US4732008 discloses a triple-effect absorption method and apparatus comprising two single-effect absorption circuits with heat exchange occurring between a condenser and an absorber of a high temperature circuit, and a generator of a low temperature circuit; the refrigeration circuits are operated at relatively higher and lower temperatures, in which the external heat input is utilized three times to improve the COP.

The present invention provides a triple-effect absorption refrigeration system which aims at overcoming the limitations of the known triple-effect absorption refrigeration systems. The present invention is directed at providing a higher COP using a low temperature heat source; further the system is energy-efficient, simple, and cost-effective, with minimal heat losses and controlled pressures.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a triple-effect absorption refrigeration system.
Another object of the present invention is to provide a triple-effect absorption refrigeration system having an increased co-efficient of performance (COP).
Yet another object of the present invention is to provide a triple-effect absorption refrigeration system using a low temperature heat source.
Still another object of the present invention is to provide a triple-effect absorption refrigeration system which is energy-efficient.
One more object of the present invention is to provide a triple-effect absorption refrigeration system which is simple and easy to operate.
Still one more object of the present invention is to provide a triple-effect absorption refrigeration system which aims at alleviating the corrosion problems associated with such systems.

Yet one more object of the present invention is to provide a triple-effect absorption refrigeration system which reduces the heat losses.
An additional object of the present invention is to provide a triple-effect absorption refrigeration system which does not operate at super-atmospheric pressures.
SUMMARY OF THE INVENTION
In accordance with the present invention is provided a triple-effect absorption refrigeration system comprising:
■ a first operation cycle to provide a heated LiBr solution having concentration between 25 - 45 %;
■ a second operation cycle to provide a cooled LiBr solution having concentration between 54 - 64 %;
■ a desorber in operative communication with said first operation cycle to receive the heated LiBr solution, said desorber being adapted to extract heat from a fluid to be cooled in the heated LiBr solution to provide refrigeration effect and generate a heated liquid-vapor mixture of concentrated LiBr solution; and
■ an absorber in operative communication with said second operation cycle to receive the cooled LiBr solution, said absorber being adapted to absorb vapors from the heated liquid-vapor mixture of concentrated LiBr solution in the cooled LiBr solution to give a dilute LiBr solution;
■ wherein, said first operation cycle is adapted to receive the heated concentrated LiBr solution from said desorber and dilute the LiBr solution to 25 - 45 % by passing through at least one resorber to

provide the heated LiBr solution; said second operation cycle is adapted to receive the dilute LiBr solution from said absorber and concentrate the LiBr solution to 54 - 64 % by passing through at least one generator to provide the cooled LiBr solution; and said at least one resorber is provided in communication with said at least one generator to receive water vapors.
Typically, in accordance with the present invention, said first operation cycle comprises a high temperature resorber, a medium temperature resorber and a low temperature resorber being adapted to dilute the heated concentrated LiBr solution from said desorber to obtain the heated LiBr solution having concentration between 25 - 45 %.
Preferably, in accordance with the present invention, said second operation cycle comprises a high temperature generator, a medium temperature generator and a low temperature generator being adapted to concentrate the dilute LiBr solution from said absorber to obtain LiBr solution having concentration between 54-64 %.
Typically, in accordance with the present invention, said first operation cycle comprises a first high temperature heat exchanger, a first medium temperature heat exchanger, and a first low temperature heat exchanger being adapted to further heat the heated LiBr solution having concentration between 25 - 45 %.
Preferably, in accordance with the present invention, said second operation cycle comprises a second high temperature heat exchanger, a second medium temperature heat exchanger, and a second low temperature heat exchanger

being adapted to cool the LiBr solution having concentration between 54 - 64 %.
Typically, in accordance with the present invention, said high temperature resorber, said medium temperature resorber, and said low temperature resorber receive water vapors from said high temperature generator, said medium temperature generator, and said low temperature generator, respectively.
In accordance with the present invention, is provided a method for obtaining refrigeration effect by using a triple-effect absorption refrigeration system, said method comprising the steps of:
■ vaporizing at least a portion of heated LiBr solution having concentration between 25 - 45 % in a desorber by taking heat from a fluid to be cooled to generate the refrigeration effect and give a heated liquid-vapor mixture of concentrated LiBr solution;
■ absorbing the LiBr vapors from the heated liquid-vapor mixture of concentrated LiBr solution in a cooled LiBr solution having concentration in the range of 54 - 64 % in an absorber, to generate a dilute LiBr solution;
■ receiving the heated concentrated LiBr solution from said desorber in a first operation cycle being adapted to dilute the LiBr solution to provide the heated LiBr solution which is recycled to the desorber; and
■ receiving the dilute LiBr solution from the absorber in a second operation cycle being adapted to concentrate the LiBr solution to provide the cooled LiBr solution which is recycled to the absorber.

Typically, in accordance with the present invention, the method includes the step of diluting the heated concentrated LiBr solution from said desorber in said first operation cycle by passing through a high temperature resorber, a medium temperature resorber and a low temperature resorber, to obtain the heated dilute LiBr solution.
Preferably, in accordance with the present invention, the method includes the step of concentrating the dilute LiBr solution from said absorber in said second operation cycle by passing through a high temperature generator, a medium temperature generator and a low temperature generator, to obtain LiBr solution having concentration between 54-64%.
Typically, in accordance with the present invention, the method includes the step of further heating the heated dilute LiBr solution in said first operation cycle by passing through a first high temperature heat exchanger, a first medium temperature heat exchanger, and a first low temperature heat exchanger.
Preferably, in accordance with the present invention, the method includes the step of cooling the LiBr solution having concentration between 54 - 64 % in said second operation cycle by passing through a second high temperature heat exchanger, a second medium temperature heat exchanger, and a second low temperature heat exchanger to obtain the cooled LiBr solution.
Typically, in accordance with the present invention, the method includes the step of receiving water vapors from said high temperature generator, said medium temperature generator and said low temperature generator in said high

temperature resorber, said medium temperature resorber and said low temperature resorber, respectively.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will now be described with the help of the accompanying drawings, in which,
FIGURE 1 illustrates a schematic diagram of a first embodiment of the triple-effect absorption refrigeration system, in accordance with the present invention; and
FIGURE 2 illustrates a schematic diagram of a second embodiment of the triple-effect absorption refrigeration system, in accordance with the present invention.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will now be described with reference to the accompanying drawings which do not limit the scope and ambit of the invention. The description provided is purely by way of example and illustration.
The present invention envisages a triple-effect absorption refrigeration system which provides a high COP, while using a low temperature heat source, alleviating the corrosion problems. The system of the present invention aims at minimizing heat losses, thus, energy efficient, is simple and easy to operate, and operates at pressures well below super-atmospheric pressures.

The triple-effect absorption refrigeration system in accordance with the present invention comprises: a desorber (106), an absorber (108), a first operation cycle (102, 150) further comprising: a first low temperature heat exchanger (110), a first medium temperature heat exchanger (112), a first high temperature heat exchanger (114), a high temperature resorber (116), a medium temperature resorber (118), and a low temperature resorber (120), and a second operation cycle (104, 152) still further comprising: a second low temperature heat exchanger (122), a second medium temperature heat exchanger (124), a second high temperature heat exchanger (126), a high temperature generator (128), a medium temperature generator (130), and a low temperature generator (132).
In the triple-effect absorption refrigeration system of the present invention: the desorber (106) is provided in communication with the absorber (108) and is operatively connected to the first operation cycle (102, 150) at the first low temperature heat exchanger (110), with chilled water being passed there through (134); and the absorber (108) is provided in communication with the desorber (106) and the low temperature resorber (120), is operatively connected to the second operation cycle (104, 152) at the second low temperature heat exchanger (122), with cooling water being passed there through (136).
For achieving refrigeration using a water-lithium bromide (LiBr) pair, as the refrigerant-absorbent pair, heat source having temperature between 155 - 190 °C, the desorber (106), illustrated in FIGURE 1 & 2, receives a LiBr solution having concentration in the range of 25 - 45 % from the first operation cycle (102, 150), and the absorber (108), illustrated in FIGURE 1 & 2, receives a LiBr solution having concentration in the range of 54 - 64 % from the second operation cycle (104, 152). In the desorber (106), heat from the chilled water

being passed there through, via passage (134), is extracted in the LiBr solution, to vaporize a part of the LiBr solution therein, giving LiBr vapors, a LiBr solution having concentration in the range of 25 - 45 %, and thereof provide cooling. The absorber (108) absorbs the LiBr vapors in the LiBr solution received therein and generates a LiBr solution having concentration in the range of 54 - 64 %, thereby releasing the heat of absorption which is extracted by the cooling water passed there through via passage (136).
The first operation cycle (102, 150) receives the LiBr solution having concentration in the range of 25 - 45 % from the desorber (106) and is adapted to dilute this LiBr solution and transfer heat thereto, and return a LiBr solution haying concentration in the range of 25 - 45 % to the desorber (106); and the second operation cycle (104, 152) receives the LiBr solution having concentration in the range of 54 - 64 % from the absorber (108) and is adapted to concentrate this LiBr solution and transfer heat thereto, and return a LiBr solution having concentration in the range of 54 - 64 % to the absorber (108).
The first operation cycle (102, 150) comprises: the first low temperature heat exchanger (110) which is operatively connected to the desorber (106), the low temperature resorber (120), and the first medium temperature heat exchanger (112); the first medium temperature heat exchanger (112) which is operatively connected to the first low temperature heat exchanger (110), the low temperature resorber (120), the medium temperature resorber (118), and the first high temperature heat exchanger (114); the first high temperature heat exchanger (114) which is operatively connected to the first medium temperature heat exchanger (112), the medium temperature resorber (118), and the high temperature resorber (116); the high temperature resorber (116) which

is operatively connected to the first high temperature heat exchanger (114), the medium temperature generator (130), the second medium temperature heat exchanger (124), and the high temperature generator (128); the medium temperature resorber (118) which is operatively connected to the first medium temperature heat exchanger (112), the low temperature generator (132), the second medium temperature heat exchanger (124) or the second low temperature heat exchanger (122), the first high temperature heat exchanger (114), and the medium temperature generator (130); and the low temperature resorber (120) which is operatively connected to the first low temperature heat exchanger (110), the first medium temperature heat exchanger (112), the absorber (108), and the low temperature generator (132).
The second operation cycle (104, 152) comprises: the second low temperature heat exchanger (122) which is operatively connected to the absorber (108), the low temperature generator (132) or the medium temperature resorber (118), and the second medium temperature heat exchanger (124); the second medium temperature heat exchanger (124) which is operatively connected to the second low temperature heat exchanger (122), the medium temperature resorber (118) or the high temperature resorber (116), the medium temperature generator (130) or the low temperature generator (132), and the second high temperature heat exchanger (126); the second high temperature heat exchanger (126) which is operatively connected to the second medium temperature heat exchanger (124), the high temperature resorber (116) or the medium temperature generator (130), and the high temperature generator (128); the high temperature generator (128) which is operatively connected to the second high temperature heat exchanger (126), the high temperature resorber (116), and a heat source; the medium temperature generator (130) which is operatively connected to the second

medium temperature heat exchanger (124) or the second high temperature heat exchanger (126), the medium temperature resorber (118), and the high temperature resorber (116); and the low temperature generator (132) which is operatively connected to the second low temperature heat exchanger (122) or the second medium temperature heat exchanger (124), the medium temperature resorber (118), and the low temperature resorber (120).
FIGURE 1 & FIGURE 2 illustrate the schematic of a first and a second embodiment of the triple-effect absorption refrigeration system. The LiBr solution having concentration in the range of 25 - 45 % is pumped to the first operation cycle by pumping means (144), the first operation cycle being referred by numeral 102 in FIGURE 1 and numeral 150 in FIGURE 2, at the first low temperature heat exchanger (110) which is adapted to extract heat from a LiBr solution having concentration in the range of 25 - 45 % received therein from the low temperature resorber (120), so as to heat the LiBr solution with concentration in the range of 25 - 45 %, the heat-extracted LiBr solution being fed to the desorber (106). The heated LiBr solution having concentration in the range of 25 - 45 % is then transmitted to the first medium temperature heat exchanger (112) where it extracts heat from a LiBr solution having concentration in the range of 25 - 45 % from the medium temperature resorber (118), thereby producing a further heated LiBr solution with concentration in the range of 25 - 45 % which is fed to the first high temperature heat exchanger (114), the heat-extracted LiBr solution being fed to the low temperature resorber (120). In the first high temperature heat exchanger (114), the further heated LiBr solution having concentration in the range of 25 - 45 % is still further heated by a LiBr solution having concentration in the range of 25 - 45 % received therein from the high temperature resorber (116), providing a still

further heated LiBr solution having concentration in the range of 25 - 45 %, which is received in the high temperature resorber (116) and a heat-extracted LiBr solution having concentration in the range of 25 - 45 % which is fed to the medium temperature resorber (118). Thus, the LiBr solution from the desorber (106), received in the first operation cycle (102), is heated by passing through the series of heat exchangers, viz., 110, 112, and 114, before receiving it in the high temperature resorber (116) where the LiBr solution is diluted.
In the high temperature resorber (116) the still further heated LiBr solution with concentration in the range of 25 - 45 %, absorbs water vapors received therein from the high temperature generator (128), through a passage represented by numeral 138, thus diluting the LiBr solution to a concentration in the range of 25 - 45 %. The heat of absorption generated in the high temperature resorber (116) during the absorption process is extracted by a LiBr solution having concentration in the range of 54 - 64 %, received therein from the second high temperature heat exchanger (126), as shown in the FIGURE 1, or the second medium temperature heat exchanger (124), as shown in the FIGURE 2.
The diluted still further heated LiBr solution with concentration in the range of 25 - 45 % from the high temperature resorber (116), after losing heat in the first high temperature heat exchanger (114) is received in the medium temperature resorber (118). In the medium temperature resorber (118), water vapors received from the medium temperature generator (130) through a passage represented by numeral 140, are absorbed in the heat-extracted LiBr solution, to cause further dilution of the heat-extracted LiBr solution up to a concentration in the range of 25 - 45 %. This diluted heat-extracted LiBr solution is received in the first medium temperature heat exchanger (112), where heat is further

extracted from the LiBr solution. The heat of absorption, generated in the medium temperature resorber (118) during the absorption process, is extracted by a LiBr solution; wherein the LiBr solution is either circulated there through from the second medium temperature heat exchanger (124) as shown in the FIGURE 1, or from the second low temperature heat exchanger (122) as shown in the FIGURE 2.
The further diluted heat-extracted LiBr solution having concentration in the range of 25 - 45 % from the medium temperature resorber (118), after cooling in the first medium temperature heat exchanger (112), is received in the low temperature resorber (120). In the low temperature resorber (120), water vapors from the low temperature generator (132) are received via the passage represented by numeral 142, which are absorbed in the LiBr solution so as to still further dilute the LiBr solution, to obtain the LiBr solution having concentration in the range of 25 - 45 %, to be fed in the desorber (106), after further cooling in the first low temperature heat exchanger (110). The heat of absorption generated during the absorption process in the low temperature resorber (120) is extracted by cooling water circulated there through, via passage represented by numeral 136, from the absorber (108).
Referring to FIGURE 1, the LiBr solution having concentration in the range of 54 - 64 % is pumped by pumping means 146, to the second operation cycle, referred by numeral 104 in FIGURE 1, from the absorber (108), at the second low temperature heat exchanger (122), where the LiBr solution extracts heat from a second LiBr solution having concentration in the range of 54 — 64 % and received therein from the low temperature generator (132). The heated LiBr solution having concentration in the range of 54 - 64 %, is received in the

second medium temperature heat exchanger (124), where it is further heated by a LiBr solution having concentration in the range of 54 - 64 % and received therein from the medium temperature generator (130). The further heated LiBr solution having concentration in the range of 54 - 64 % is still further heated in the second high temperature heat exchanger (126); wherein it extracts heat from a LiBr solution having concentration in the range of 54 - 64 % and received therein from the high temperature generator (128).
The still further heated LiBr solution having concentration in the range of 54 -64 % is received high temperature generator (128) from the second high temperature heat exchanger (126); wherein a heat source having temperature between 155 - 190 °C causes the LiBr solution to boil releasing water vapors which are fed to the high temperature resorber (116) through the passage 138, thereby generating a concentrated LiBr solution having concentration in the range of 54 - 64 %. The concentrated LiBr solution generated in the high temperature generator (128) is passed through the second high temperature heat exchanger (126) and the high temperature resorber (116), where the heat from the LiBr solution is extracted, before receiving the concentrated heat-extracted LiBr solution in the medium temperature generator (130).
In the medium temperature generator (130), the concentrated LiBr solution having concentration in the range of 54 - 64 % is further concentrated by flashing the solution therein, generating a further concentrated LiBr solution having concentration in the range of 54 - 64 % and producing water vapors which are fed to the medium temperature resorber (118) through the passage 140. The further concentrated LiBr solution generated in the medium temperature generator (130) is passed through the second medium temperature

heat exchanger (124) and the medium temperature resorber (118), where the heat from the LiBr solution is extracted, before receiving the further concentrated further heat-extracted LiBr solution in the low temperature generator (132).
In the low temperature generator (132), the further concentrated LiBr solution having concentration in the range of 54 - 64 %, is still further concentrated by flashing the solution therein, generating a still further concentrated LiBr solution having concentration in the range of 54 - 64 % and producing water vapors which are fed to the low temperature resorber (120) through the passage 142. The still further concentrated LiBr solution generated in the low temperature generator (132) is passed through the second low temperature heat exchanger (122), where the heat from the LiBr solution is extracted, before receiving this concentrated cooled LiBr solution having concentration in the range of 54 - 64 %, in the absorber (108).
Referring to FIGURE 2, the LiBr solution having concentration in the range of 54 - 64 % is pumped by pumping means 146, to the second operation cycle, referred by numeral 152 in FIGURE 2, from the absorber (108), at the second low temperature heat exchanger (122), where the LiBr solution extracts heat from a second LiBr solution having concentration in the range of 54 - 64 % and received therein from the second medium temperature heat exchanger (124). The heated LiBr solution having concentration in the range of 54 - 64 %, after passing through the medium temperature resorber (118) where the LiBr solution extracts the heat of absorption, is received in the low temperature generator (132).

In the low temperature generator (132), the heated LiBr solution having concentration in the range of 54 - 64 % is flashed, thereby generating a concentrated LiBr solution having concentration in the range of 54 - 64 % and producing water vapors which are fed to the low temperature resorber (120) via the passage 142. The concentrated LiBr solution is pumped from the low temperature generator (132), by pumping means 148b, to the second medium temperature heat exchanger (124) where it is further heated by extracting heat from a second LiBr solution having concentration in the range of 54 - 64 % received therein from the second high temperature heat exchanger (126).
The further heated concentrated LiBr solution having concentration in the range of 54 - 64 %, after passing through the high temperature resorber (116) where the LiBr solution extracts the heat of absorption, is received in the medium temperature generator (130). In the medium temperature generator (130), the further heated LiBr solution having concentration in the range of 54 - 64 % is flashed, thereby providing a further concentrated LiBr solution having concentration in the range of 54 - 64 %, and giving water vapors which are fed to the medium temperature resorber (118) through the passage 140. The further concentrated LiBr solution from the medium temperature generator (130) is pumped by pumping means 148a, to the second high temperature heat exchanger (126), where the LiBr solution extracts heat from a second LiBr solution having concentration in the range of 54 - 64 % received therein from the high temperature generator (128).
The still further heated LiBr solution having concentration in the range of 54 -64 % is received in the high temperature generator (128) from the second high temperature heat exchanger (126); wherein a heat source having temperature

between 155 - 190 °C causes the LiBr solution to boil releasing water vapors which are fed to the high temperature resorber (116) through the passage 138, thereby generating a still further concentrated LiBr solution having concentration in the range of 54 - 64 %. The still further concentrated LiBr solution is fed to the absorber (108) after losing heat in the second high temperature heat exchanger (126), the second medium temperature heat exchanger (124), and the second low temperature heat exchanger (122).
TECHNICAL ADVANTAGES
A triple-effect absorption refrigeration system as described in the present invention has several technical advantages including but not limited to the realization of:
• a triple-effect absorption refrigeration system having a high co-efficient of performance (COP);
• a triple-effect absorption refrigeration system using a low temperature heat source;
• a triple-effect absorption refrigeration system which is energy-efficient;
• a triple-effect absorption refrigeration system which is simple and easy to operate;
• a triple-effect absorption refrigeration system which aims at alleviating the corrosion problems;
• a triple-effect absorption refrigeration system which reduces the heat losses; and
• a triple-effect absorption refrigeration system which does not operate at super-atmospheric pressures.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the invention, unless there is a statement in the specification specific to the contrary.
In view of the wide variety of embodiments to which the principles of the present invention can be applied, it should be understood that the illustrated embodiments are exemplary only. While considerable emphasis has been placed herein on the particular features of this invention, it will be appreciated that various modifications can be made, and that many changes can he made in the preferred embodiments without departing from the principle of the invention. These and other modifications in the nature of the invention or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

Claim:
1. A triple-effect absorption refrigeration system comprising:
■ a first operation cycle (102, 150) to provide a heated LiBr solution having concentration between 25 - 45 %;
■ a second operation cycle (104, 152) to provide a cooled LiBr solution having concentration between 54 - 64 %;
■ a desorber (106) in operative communication with said first operation cycle (102, 150) to receive the heated LiBr solution, said desorber (106) being adapted to extract heat from a fluid to be cooled in the heated LiBr solution to provide refrigeration effect and generate a heated liquid-vapor mixture of concentrated LiBr solution; and
■ an absorber (108) in operative communication with said second operation cycle (104, 152) to receive the cooled LiBr solution, said absorber (108) being adapted to absorb vapors from the heated liquid-vapor mixture of concentrated LiBr solution in the cooled LiBr solution to give a dilute LiBr solution;
■ wherein, said first operation cycle (102, 150) is adapted to receive the heated concentrated LiBr solution from said desorber (106) and dilute the LiBr solution to 25 - 45 % by passing through at least one resorber to provide the heated LiBr solution; said second operation cycle (104, 152) is adapted to receive the dilute LiBr solution from said absorber (108) and concentrate the LiBr solution to 54 - 64 % by passing through at least one generator to provide the cooled LiBr solution; and said at least one resorber is

provided in communication with said at least one generator to receive water vapors.
2. The apparatus as claimed in claim 1, wherein said first operation cycle (102, 150) comprises a high temperature resorber (116), a medium temperature resorber (118) and a low temperature resorber (120) being adapted to dilute the heated concentrated LiBr solution from said desorber (106) to obtain the heated LiBr solution having concentration between 25 - 45 %.
3. The apparatus as claimed in claim 1, wherein said second operation cycle (104, 152) comprises a high temperature generator (128), a medium temperature generator (130) and a low temperature generator (132) being adapted to concentrate the dilute LiBr solution from said absorber (108) to obtain LiBr solution having concentration between 54 - 64 %.
4. The apparatus as claimed in claim 2, wherein said first operation cycle (102, 150) comprises a first high temperature heat exchanger (114), a first medium temperature heat exchanger (112), and a first low temperature heat exchanger (110) being adapted to further heat the heated LiBr solution having concentration between 25 - 45 %.
5. The apparatus as claimed in claim 3, wherein said second operation cycle (104, 152) comprises a second high temperature heat exchanger (126), a second medium temperature heat exchanger (124), and a second low temperature heat exchanger (122) being adapted to cool the LiBr solution having concentration between 54-64 %.

6. The apparatus as claimed in anyone of the preceding claims, wherein said high temperature resorber (116), said medium temperature resorber (118), and said low temperature resorber (120) receive water vapors from said high temperature generator (128), said medium temperature generator (130), and said low temperature generator (132), respectively.
7. A method for obtaining refrigeration effect by using a triple-effect absorption refrigeration system, said method comprising the steps of:

■ vaporizing at least a portion of heated LiBr solution having concentration between 25 - 45 % in a desorber by taking heat from a fluid to be cooled to generate the refrigeration effect and give a heated liquid-vapor mixture of concentrated LiBr solution;
■ absorbing the LiBr vapors from the heated liquid-vapor mixture of concentrated LiBr solution in a cooled LiBr solution having concentration in the range of 54 - 64 % in an absorber, to generate a dilute LiBr solution;
■ receiving the heated concentrated LiBr solution from said desorber in a first operation cycle being adapted to dilute the LiBr solution to provide the heated LiBr solution which is recycled to the desorber; and
■ receiving the dilute LiBr solution from the absorber in a second operation cycle being adapted to concentrate the LiBr solution to provide the cooled LiBr solution which is recycled to the absorber.
8. The method as claimed in claim 7, which includes the step of diluting the
heated concentrated LiBr solution from said desorber in said first

operation cycle by passing through a high temperature resorber, a medium temperature resorber and a low temperature resorber, to obtain the heated dilute LiBr solution.
9. The method as claimed in claim 7, which includes the step of concentrating the dilute LiBr solution from said absorber in said second operation cycle by passing through a high temperature generator, a medium temperature generator and a low temperature generator, to obtain LiBr solution having concentration between 54 - 64 %.
10.The method as claimed in claim 8, which includes the step of further heating the heated dilute LiBr solution in said first operation cycle by passing through a first high temperature heat exchanger, a first medium temperature heat exchanger, and a first low temperature heat exchanger.
11 .The method as claimed in claim 9, which includes the step of cooling the LiBr solution having concentration between 54 - 64 % in said second operation cycle by passing through a second high temperature heat exchanger, a second medium temperature heat exchanger, and a second low temperature heat exchanger to obtain the cooled LiBr solution.
12.The method as claimed in anyone of the preceding claims, which includes the step of receiving water vapors from said high temperature generator, said medium temperature generator and said low temperature generator in said high temperature resorber, said medium temperature resorber and said low temperature resorber, respectively.