FORM-2
THE PATENTS ACT, 1970 (39 of 1970)
THE PATENTS RULES, 2006
COMPLETE
Specification
(See Section 10 and Rule 13)
VAPOR ABSORPTION SYSTEM
THERMAX LIMITED
an Indian Company
of D-13, MIDC Industrial Area, R.D. Aga Road,
Chinchwad, Pune - 411 019,
Maharashtra, India.
Inventors: a) Navale Devadatta; & b) Kulkarni Sameer.
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 a vapor absorption system and more particularly it relates to an ammonia-based vapor absorption system.
BACKGROUND
A vapor absorption system for refrigeration using ammonia-water as the refrigerant-absorbent pair comprises: a reboiler which provides a weak solution (with low ammonia concentration), an absorber which provides a strong solution (with high ammonia concentration), and a solution heat exchanger for cooling the weak solution by using the strong solution.
FIG. 1 illustrates an embodiment of a known vapor absorption system using ammonia-water as the refrigerant-absorbent. A weak solution from a reboiler 12 is cooled in a solution heat exchange 16 by using a strong solution coming from an absorber 14 via a solution pump 18. The solution heat exchanger (SHE) 16 is provided in communication with a stripping column 24 to receive the strong solution and separate the components thereof. The ammonia solution leaving the stripping column 24 at the bottom is received in the reboiler 12 where by means of steam 20 the weak solution is obtained. The weak solution from the solution heat exchanger 16 is received in the absorber 14 via expansion valve 36a, wherein cooling water is conveyed through the absorber 14 via inlet 38a and outlet 38b. The vapors from the stripping column is passed through a partial condenser 26, where cooling water is provided through supply line 40a and discharged through supply line 40b. From the partial condenser 26 the partially condensed water is conveyed to a condenser 28. The condenser 28 is provided with an inlet 37a and an outlet 37b for conveying cooling water. The condensed water is conveyed to an

evaporator 30 after passing through a series of heat exchanger 32, 34 via an expansion valve 36b.
A high concentration difference between the weak solution and the strong solution is desirable to obtain high system coefficient of performance (COP), low solution flow rates and therefore lower pumping costs and reduced equipment size. A high concentration difference between the weak solution and the strong solution can be obtained by providing: a high temperature heat source or reboiler temperature which gives low ammonia concentration in the weak solution, low cooling water temperature which gives low ammonia concentration in the weak solution and high ammonia concentration in the strong solution, and high refrigeration/evaporation temperature which also gives high ammonia concentration in the strong solution.
However, when the concentration difference between the weak and the strong solution is high, the strong solution leaving the solution heat exchanger 16 becomes a two phase mixture of vapor and liquid. When the outlet of the solution heat exchanger 16 is a vapor liquid mixture, due to inherent properties of ammonia-water vapor liquid equilibrium, the inlet concentration to the stripping column 24 reduces. This increases the net heat input to the reboiler 12. Thus the advantage obtained by having a higher concentration is lost due to the extra heat required in additional rectification of lower solution concentration caused by the vapor-liquid mixture. Therefore, although high concentration difference is desirable due to the higher COP, lower solution flow rates which result in lower pumping power, and smaller sizes of equipment, it is limited because of the occurrence of vapor-liquid mixture at the solution heat exchanger 16 exit.

When the concentration difference is high the heat of absorption which is usually lost to the cooling water in a conventional cycle can be recovered by using solution cooled absorber (SCA) and generator-absorber-heat exchangers (GAX). This additional recovered heat reduces the reboiler duty and hence increases the COP. Such an embodiment is illustrated in FIG.2, wherein FIG. 2 shows a GAX cycle disclosed in US5857355. The GAX cycle as disclosed in FIG. 2 comprises additional heat exchangers of solution cooled absorber (SCA) 108, solution cooled rectifier (SCR) 105, solution heat generator (SHG) 101, generator absorber heat exchanger (GAX) 109.
The GAX cycle disclosed in US5857355 eliminates the solution heat exchanger (SHE) and/or partial condenser from the cycle. The limitations of this cycle are as follows:
1. The cycle operation at a lower concentration becomes unstable as the weak solution entering the GAX 109 in the absorber section becomes two phase vapor-liquid mixture. This creates large pressure drop in the weak solution line after expansion valve to the GAX distributor. Thus flow through the weak solution line get disturbed and creates instability in the operation. Thus, this cycle can only operate at higher concentration difference and not at lower concentration difference.
2. The SCR 105 provided for purification of the ammonia vapor is highly sensitive to the flow, temperature, pressure and concentration of inlet strong solution flow as coolant to the SCR. Any small change in external parameters such as cooling load, cooling water temperature, evaporation temperature and external heat source temperature results in impure ammonia leaving SCR. This impure ammonia can cross the design limit which in turn results in increase in bleed flow from evaporator to maintain pool


concentration. Due to the variation in bleed flow there is a loss in cooling energy resulting in lower COP and instability in the operation of the system. 3. The SHG 101 in the cycle is part of the stripping column for simultaneous heat and mass transfer. This increases stripping column height. Thus, the stripping column becomes bulky.
Thus the current challenge is to maintain a higher concentration difference to improve the COP and at the same time to ensure that:
i. inlet to the stripping column is in the liquid state;
ii. inlet weak solution entering absorber/GAX is in liquid state;
iii. purity of ammonia is maintained to acceptable limits; and
iv. stable and reliable operation of cycle with improved COP at all operating solution concentration differences is achieved.
There is therefore felt a requirement for an ammonia-based vapor absorption system which will overcome the afore-mentioned drawbacks of known systems and provide a higher COP while reducing the energy consumption.
OBJECTS
It is an object of the present invention to provide an ammonia-based vapor absorption system which gives a higher COP by maintaining a high concentration difference between the weak solution and the strong solution, wherein the inlet to the stripping column is completely liquid.
Another object of the present invention is to provide an ammonia-based vapor absorption system which conserves energy and reduces the equipment size.

SUMMARY OF THE INVENTION
These and other objects are dealt in the present invention by providing an improved ammonia-based vapor absorption system for providing heating and cooling.
In accordance with the present invention, there is provided an ammonia-based vapor absorption system for heating/cooling applications, said vapor absorption system comprising:
■ an evaporator for providing ammonia vapors;
■ a reboiler for providing a weak solution and ammonia vapors;
■ a generator-absorber-heat exchanger, a solution cooled absorber and an absorber operatively connected in series and in communication with said evaporator for absorbing the ammonia vapors there from in the weak ammonia solution received from said reboiler via an expansion valve, wherein said solution cooled absorber is adapted to provide the heat of absorption to a strong ammonia solution produced during the absorption process in said absorber, and optionally a portion of the heated strong ammonia solution is received in said generator-absorber-heat exchanger for extracting the heat of absorption therein to generate an ammonia liquid-vapor mixture;
■ a solution heat exchanger provided in operative communication with said solution cooled absorber to receive at least a portion of heated strong ammonia solution, said solution heat exchanger being adapted to heat the strong ammonia solution to saturation temperature in liquid state;
■ a solution heat generator provided in operative communication with at least one device selected from said solution heat exchanger and said generator-absorber-heat exchanger to receive at least one solution from a

portion of the strong ammonia solution at saturation temperature and the ammonia liquid-vapor mixture, respectively, to generate a vapor fraction;
■ a stripping column provided in operative communication with said solution heat exchanger to receive at least a portion of the strong ammonia solution at saturation temperature, said solution heat generator to receive the vapor fraction and said reboiler to receive the ammonia vapors, said stripping column being adapted to partially purify the ammonia vapors to give partially purified ammonia vapors, and a liquid-vapor mixture of strong ammonia solution and water vapors which are received in said reboiler;
■ a rectification column and a partial condenser operative connected in series for further purifying the partially purified ammonia vapors from said stripping column and provide partially condensed ammonia solution; and
■ a condenser in operative communication with said partial condenser for receiving the partially condensed ammonia solution and to provide condensed ammonia solution which is subsequently fed to the evaporator, thereby completing the absorption cycle.
Typically, in accordance with the present invention, there is provided a solution splitter in operative communication with at least one device selected from said solution cooled absorber and solution heat exchanger, said solution splitter being adapted to bifurcate the strong ammonia solution.
Preferably, in accordance with the present invention, the strong ammonia solution from said absorber is pumped to said solution cooled absorber via a solution pump.
Typically, in accordance with the present invention, the condensed ammonia solution is cooled in at least one device selected from a refrigerant heat exchanger

and a bleed heat exchanger, wherein said refrigerant heat exchanger and said bleed heat exchanger are connected in series.
Preferably, in accordance with the present invention, the liquid-vapor mixture of strong ammonia solution and the water vapors are boiled in the reboiler to generate the ammonia vapors which are fed to said stripping column and the weak ammonia solution.
Typically, in accordance with the present invention, the weak ammonia solution is sprayed on said generator-absorber-heat exchanger or said solution cooled absorber after cooling in said solution heat generator and said solution heat exchanger.
In accordance with the present invention, there is disclosed a method for operating an ammonia-based vapor absorption system for heating/cooling applications, said method comprising the steps of:
■ absorbing ammonia vapors from an evaporator into a weak ammonia solution sprayed in a generator-absorber-heat exchanger, a solution cooled absorber and an absorber to generate a strong ammonia solution;
■ circulating the strong ammonia solution to said solution cooled absorber to extract the heat of absorption therein, to generate a heated strong solution;
■ conveying at least a portion of the heated strong ammonia solution to a solution heat exchanger, optionally a second portion of the heated strong ammonia solution is conveyed to said generator-absorber-heat exchanger to extract the heat of absorption and generate an ammonia liquid-vapor mixture;

■ heating the heated strong ammonia solution in said solution heat exchanger to generate a strong ammonia solution at saturated temperature in liquid state, optionally a portion of the strong ammonia solution at saturated temperature is conveyed to said generator-absorber-heat exchanger to extract the heat of absorption and generate an ammonia liquid-vapor mixture;
■ conveying the ammonia liquid-vapor mixture to a solution heat generator to obtain a vapor fraction;
■ feeding at least a portion of the strong ammonia solution at saturated temperature, the vapor fraction, and ammonia vapors from a reboiler, to a stripping column, to generate partially purified ammonia vapors and a liquid-vapor mixture of strong ammonia solution and water vapors;
■ boiling the liquid-vapor mixture of strong ammonia solution and the water vapors in the reboiler to generate the weak ammonia solution and the ammonia vapors which are fed to said stripping column;
■ purifying the partially purified ammonia vapors in a rectification column;
■ condensing partially the purified ammonia vapors in a partial condenser;
■ condensing the partially condensed ammonia solution in a condenser to obtain condensed ammonia solution;
■ cooling the condensed ammonia solution in a refrigerant heat exchanger and a bleed heat exchanger; and
■ feeding the cooled condensed ammonia solution to said evaporator to obtain the ammonia vapors, thereby completing the absorption cycle.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will now be described with the help of the accompanying drawings, in which,
FIGURE 1 illustrates an embodiment of a known vapor absorption system;
FIGURE 2 illustrates another embodiment of a known vapor absorption system;
FIGURE 3 illustrates an embodiment of the vapor absorption system, in accordance with the present invention;
FIGURE 4 illustrates another embodiment of the vapor absorption system, in accordance with the present invention; and
FIGURE 5 illustrates yet another embodiment of the vapor absorption system, in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
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 vapor absorption system of the present invention is illustrated in FIGS. 3, 4 & 5, where the system is generally represented by numerals 200a, 200b, & 200c in FIGS. 3, 4 & 5 respectively. In the vapor absorption system 200a, a strong ammonia solution is pumped from an ammonia solution pump 202a to a solution cooled absorber (SCA) 204a. In the SCA 204a, the strong ammonia solution flows

on one side and absorption of ammonia vapors in weak ammonia solution takes place on the other side. The ammonia vapors absorbed in the SCA 204a are received from an evaporator 206a via a refrigerant heat exchanger (RHE) 208a. These ammonia vapors from the evaporator 206a are absorbed by a weak solution coming from a generator-absorber-heat exchanger (GAX) 210a; heat of absorption is released during this process. Heat transferred in the SCA 204a increases the temperature of the strong ammonia solution produced thereof. The heated strong ammonia solution then flows through a solution heat exchanger (SHE) 212a. In the SHE 212a, the heated strong ammonia solution is on one side and a weak ammonia solution coming from a solution heat generator (SHG) 214a is on the other side. The heated strong ammonia solution entering the SHE 212a is further heated to its saturation temperature at reboiler 216a pressure which thereby remains in liquid state at the SHE 212a outlet.
The strong ammonia solution at saturation temperature at the outlet of the SHE 212a flows through a solution splitter 218a where the solution is divided in two streams. One stream is the major stream comprising 60 % - 95 % of the main incoming stream and the other stream is the minor stream comprising 5 % - 40 % of the main incoming stream. The major stream, which is in a liquid state, enters a stripping column 220a as feed from the outlet of the splitter 218a. The stripping column 220a comprises a liquid distributor, a liquid collector and a packed bed of structured packing. The stripping column 220a is an adiabatic column having no external heat addition/rejection. The major stream from the splitter 220a is distributed by a distributor on the packed bed of the structured packing. The ammonia vapors generated in a reboiler 216a having high water content, are partially purified in the stripping column 220a by mass transfer.

The minor stream of the strong ammonia solution at saturation temperature from the splitter 218a consecutively flows through the GAX 210a & the SHG 214a. In the GAX 210a the strong ammonia solution at saturation temperature flows on one side and absorption of ammonia vapors in the weak ammonia solution takes place on other side. The ammonia vapors absorbed in the GAX 210a are received from the evaporator 206a via a RHE 208a. These ammonia vapors from the evaporator 206a are absorbed by the weak ammonia solution coming out of the SHE 212a via the expansion valve 209a and heat of absorption is released during this process. The minor solution stream entering the GAX 210a is in liquid/saturated liquid condition, which turns into vapor-liquid by taking the heat of absorption in the GAX 210a. The vapor fraction at the outlet can be from 0% to 30%. The minor solution stream which is in liquid-vapor mixture state at the outlet of the GAX 210a flows through the SHG 214a. In the SHG 214a it is farther heated using hot weak ammonia solution leaving the reboiler 216a. Due to heat addition in the SHG 214a, the vapor fraction of the minor stream further increases to 5% - 50 %. The minor solution stream is fed to the bottom of the stripping column 220a or to the reboiler 216a. The minor stream does not take part in mass transfer in the stripping column 220a as it is fed at the bottom of the column 220a or to the reboiler 216a.
The solution at the outlet of the stripping column 220a and the liquid-vapor mixture are received in the reboiler 216a. Heat from an external heat source 222a at high temperature is added to the incoming solution in the reboiler 216a. Due to heat addition the incoming solution is boiled to form ammonia vapors and the weak ammonia solution in the reboiler 216a. The ammonia vapors so obtained are not pure and contain water vapors. These ammonia vapors are passed through the stripping column 220a to separate water vapors. The ammonia vapors are partially purified using the major stream of the strong ammonia solution. The partially

purified ammonia vapors then enter a rectification column 224a. The vapors are further purified in the rectification column 224a using partial condenser reflux liquid. The vapors from the outlet of the rectification column 224a are further purified to required concentration in a partial condenser 226a. In the partial condenser 226a the incoming vapors are partially condensed and the heat of condensation is rejected to external cooling water. Most of the water vapors in the incoming vapor steam get condensed as partially condensed ammonia solution. This partially condensed ammonia solution from the partial condenser 226a acts as a reflux for the rectification column 224a. The ammonia vapors with required purity are totally condensed in a condenser 228a and the heat of condensation thereof is released to the external cooling water. In the condensation process partially condensed ammonia solution turn into condensed ammonia solution.
The condensed ammonia solution from the condenser 228a flows to the evaporator 206a through the refrigerant heat exchanger 208a and a bleed heat exchanger (BHE) 230a. In the RHE 208a, the condensed ammonia solution from the condenser 228a outlet is sub-cooled using cold ammonia vapors leaving the evaporator 206a. During this process temperature of the ammonia vapors is increased and the temperature of the condensed ammonia solution is decreased. The condensed ammonia solution from the outlet of the RHE 208a is further sub-cooled in the BHE 230a using ammonia bleed from the evaporator 206a. During this process temperature of the condensed ammonia solution is further reduced. The heat added to the ammonia bleed stream in the BHE 230a increases temperature of the bleed stream resulting in vapor-liquid mixture. The ammonia bleed is 2 - 10 % of the incoming ammonia stream to the evaporator 206a. The sub-cooled condensed ammonia solution from the BHE 230a flows to the evaporator 206a via an expansion valve 232a. In the expansion valve 232a pressure

of the condensed ammonia solution is reduced from the condenser pressure to the evaporator pressure. The external cooling load adds heat in the evaporator 206a which converts the condensed ammonia solution into cold ammonia vapors.
The ammonia vapors from RHE 208a outlet and liquid-vapor mixture at the outlet of the BHE 230a flows to an absorber 234a, the SCA 204a and the GAX 210a. These ammonia vapors are absorbed in the weak solution in the GAX 210a, the SCA 204a and the absorber 234a. The GAX 210a, the SCA 204a and the absorber 234a are in series and the weak ammonia solution first enters the GAX 210a then the SCA 204a and finally the absorber 234a. The heat released during vapor absorption in the absorber 234a is rejected to external cooling water. During this process of absorption the solution leaving the absorber 234a becomes rich in ammonia. This solution is pumped using the ammonia solution pump 202a to the SHE 212a, thus completing the absorption cycle.
The various alternative embodiments of the present invention, illustrated in the Figures 4 & 5, are described herein below; wherein the above-listed components are particularly denoted by alphabets b & c in FIGS. 4 & 5, respectively. FIG. 4 illustrates an arrangement in which the solution splitter 218b is provided at the outlet of the SCA 204b. The major stream passes through the SHE 212b to the rectification column 224b and the minor stream passes through the GAX 210b and the SHG 214b to the bottom of the stripping column 220b or to the reboiler 216b.
FIG. 5 illustrates an arrangement which is applicable to the operating condition in which concentration difference is such that the GAX heat exchange is theoretically not possible. In this cycle the GAX is not provided. The heated strong ammonia solution from the SCA 204c directly enters the SHE 212c and the solution splitter

218c is provided at the SHE 212c outlet. The major stream of the strong ammonia solution at saturation temperature from the solution splitter 218c flows to the stripping column 220c. The minor stream of the strong ammonia solution at saturation temperature flows through the SHG 214c directly and then to the stripping column 220c or to the reboiler 216c.
The present invention therefore envisages an ammonia-based vapor absorption system which overcomes the drawbacks of the known systems, as described herein below:
• Strong ammonia solution pumped by a solution pump is split into two streams after it passes though the SCA 204 and the SHE 212. The minor split of the solution flow, typically 5 - 25%, passes through the GAX 210 and then the SHG 214. This minor solution stream is fed to the bottom of a stripping column 220 / reboiler 216. The major split of the solution flow is fed to the stripping column 220 as a feed. The additional heat recovered in the GAX 210 and the SHG 214 in transferred to the minor stream of the strong ammonia solution flow and results in vapor-liquid mixture at the SHG 214 outlet. This minor stream is not used as feed to the column 220. Only the major split of the solution after the SHE 212 is used as a feed which remains in the liquid state/acceptable limit of vapor-liquid mixture condition at all operating conditions. Thus, negative impact on the COP, because of vapor-liquid as feed to the stripping column 220 is avoided. This results in improved COP of the system 200.
• The SHE 212 provided in the cycle ensures cooling of the weak ammonia solution. The weak ammonia solution coming out from the SHG 214 is at higher temperature than boiling point of the weak ammonia solution at absorber pressure. This is further cooled below boiling point of the weak

ammonia solution in the SHE 212 using strong ammonia solution from the SCA 204 outlet. The expansion valve 209 provided on the weak ammonia solution line after the SHE 212 drops pressure of the weak ammonia solution stream to the absorber pressure. Due to cooling of the weak ammonia solution stream in the SHE 212, flashing of weak solution after expansion valve 209 is avoided. Thus, the weak ammonia solution stream remains in liquid form at all operating conditions resulting in reliable and stable operation of the system 200.
• The partial condenser 226 is provided instead of a SCR which ensures ammonia vapor purity leaving the partial condenser 226. This results in steady bleed requirement resulting stable and reliable operation with out any negative impact on the COP of the system 200.
• The cycle is designed such that above improvements are valid at all concentration difference conditions. Also, small variations in the operating parameters do not create instability in the operation of the cycle and system.
• The additional heat exchangers the SCA 204, the GAX 210, the SHE 212 and the SHG 214 are arranged in the cycle so that it recovers more heat from the weak ammonia solution and the heat of absorption and used to heat the strong ammonia solution entering the stripping column 220 / reboiler 216. This reduces external heat input 222 to the reboiler 216 giving significant increase in the COP.
• The arrangement of heat exchangers gives higher log mean temperature difference (LMTD) for the all heat exchangers. This reduces heat transfer area of the system 200 resulting in the lower size, weight and cost of the system 200.

• The SHG 214 location in the cycle is external to the stripping column 220 which gives advantage of having reduced height of the stripping column 220.
TECHNICAL ADVANTAGES
An ammonia-based vapor absorption system for heating and cooling applications; as disclosed in the present invention has several technical advantages including but not limited to the realization of: the system provides a higher COP by maintaining a high concentration difference between the weak ammonia solution and the strong ammonia solution, wherein the inlet to the stripping column is completely liquid; and the system conserves energy and reduces the equipment size.
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 be 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.

We Claim
1. An ammonia-based vapor absorption system for heating/cooling applications, said vapor absorption system comprising:
■ an evaporator (206) for providing ammonia vapors;
■ a reboiier (216) for providing a weak solution and ammonia vapors;
■ a generator-absorber-heat exchanger (210), a solution cooled absorber (204) and an absorber (234) operatively connected in series and in communication with said evaporator (206) for absorbing the ammonia vapors there from in the weak ammonia solution received from said reboiier (216) via an expansion valve (209), wherein said solution cooled absorber (204) is adapted to provide the heat of absorption to a strong ammonia solution produced during the absorption process in said absorber (234), and optionally a portion of the heated strong ammonia solution is received in said generator-absorber-heat exchanger (210) for extracting the heat of absorption therein to generate an ammonia liquid-vapor mixture;
■ a solution heat exchanger (212) provided in operative communication with said solution cooled absorber (204) to receive at least a portion of heated strong ammonia solution, said solution heat exchanger (212) being adapted to heat the strong ammonia solution to saturation temperature in liquid state;
■ a solution heat generator (214) provided in operative communication with at least one device selected from said solution heat exchanger (212) and said generator-absorber-heat exchanger (210) to receive at least one solution from a portion of the strong ammonia solution at saturation temperature and the ammonia liquid-vapor mixture, respectively, to generate a vapor fraction;

■ a stripping column (220) provided in operative communication with said solution heat exchanger (212) to receive at least a portion of the strong ammonia solution at saturation temperature, said solution heat generator (214) to receive the vapor fraction and said reboiler (216) to receive the ammonia vapors, said stripping column (220) being adapted to partially purify the ammonia vapors to give partially purified ammonia vapors, and a liquid-vapor mixture of strong ammonia solution and water vapors which are received in said reboiler (216);
■ a rectification column (224) and a partial condenser (226) operative connected in series for further purifying the partially purified ammonia vapors from said stripping column (220) and provide partially condensed ammonia solution; and
■ a condenser (228) in operative communication with said partial condenser (226) for receiving the partially condensed ammonia solution and to provide condensed ammonia solution which is subsequently fed to the evaporator, thereby completing the absorption cycle.

2. The vapor absorption system as claimed in claim 1, wherein a solution splitter (218) is provided in operative communication with at least one device selected from said solution cooled absorber (204) and solution heat exchanger (212), said solution splitter (218) being adapted to bifurcate the strong ammonia solution.
3. The vapor absorption system as claimed in claim 1, wherein the strong ammonia solution from said absorber (234) is pumped to said solution cooled absorber (204) via a solution pump (202).

4. The vapor absorption system as claimed in claim 1, wherein the condensed ammonia solution is cooled in at least one device selected from a refrigerant heat exchanger (208) and a bleed heat exchanger (230), wherein said refrigerant heat exchanger (208) and said bleed heat exchanger (230) are connected in series.
5. The vapor absorption system as claimed in claim 1, wherein the liquid-vapor mixture of strong ammonia solution and the water vapors are boiled in the reboiler (216) to generate the ammonia vapors which are fed to said stripping column (220) and the weak ammonia solution.
6. The vapor absorption system as claimed in claim 5, wherein the weak ammonia solution is sprayed on said generator-absorber-heat exchanger (210) or said solution cooled absorber (204) after cooling in said solution heat generator (214) and said solution heat exchanger (212).
7. A method for operating an ammonia-based vapor absorption system for heating/cooling applications, said method comprising the steps of:

■ absorbing ammonia vapors from an evaporator into a weak ammonia solution sprayed in a generator-absorber-heat exchanger, a solution cooled absorber and an absorber to generate a strong ammonia solution;
■ circulating the strong ammonia solution to said solution cooled absorber to extract the heat of absorption therein, to generate a heated strong solution;
■ conveying at least a portion of the heated strong ammonia solution to a solution heat exchanger, optionally a second portion of the heated strong

ammonia solution is conveyed to said generator-absorber-heat exchanger to extract the heat of absorption and generate an ammonia liquid-vapor mixture;
■ heating the heated strong ammonia solution in said solution heat exchanger to generate a strong ammonia solution at saturated temperature in liquid state, optionally a portion of the strong ammonia solution at saturated temperature is conveyed to said generator-absorber-heat exchanger to extract the heat of absorption and generate an ammonia liquid-vapor mixture;
■ conveying the ammonia liquid-vapor mixture to a solution heat generator to obtain a vapor fraction;
■ feeding at least a portion of the strong ammonia solution at saturated temperature, the vapor fraction, and ammonia vapors from a reboiler, to a stripping column, to generate partially purified ammonia vapors and a liquid-vapor mixture of strong ammonia solution and water vapors;
■ boiling the liquid-vapor mixture of strong ammonia solution and the water vapors in the reboiler to generate the weak ammonia solution and the ammonia vapors which are fed to said stripping column;
■ purifying the partially purified ammonia vapors in a rectification column;
■ condensing partially the purified ammonia vapors in a partial condenser;
■ condensing the partially condensed ammonia solution in a condenser to obtain condensed ammonia solution;
■ cooling the condensed ammonia solution in a refrigerant heat exchanger and a bleed heat exchanger; and
■ feeding the cooled condensed ammonia solution to said evaporator to obtain the ammonia vapors, thereby completing the absorption cycle.