FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2006
COMPLETE
Specification
(See Section 10 and Rule 13)
AN AIR-COOLED APPARATUS FOR PROVIDING CONDENSATION AND ABSORPTION
THERMAX LIMITED
an Indian Company
of D-13, MIDC Industrial Area,
R.D. Aga Road, Chinchwad,
Pune - 411 019, 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 an air-cooled apparatus, particularly, for condensing/absorbing a vapor medium, generally water vapor.
BACKGROUND
Condensers are very commonly used in manufacturing and chemical processing units for condensing and cooling a vapor medium. In power plants, it is required to extract heat from the process at ambient temperature by the condensation of the vaporous medium. The air-cooled condensers are a special type of condensers, which generally operate under vacuum and without a cooling liquid, and in which the vapor medium is directly condensed by means of a cooling air flow.
A typical direct air-cooled condenser, generally used in the power plants, comprises a horizontally mounted tube bank in the form of a coil and having fins. The cooling air flows over the tube bank approximately perpendicular to the tubes from the bottom to the top. The vapor medium is carried through the tube bank. The vapor in the tube bank is condensed by the cooling air flow. To compensate for the low heat transfer coefficient of the air, the heat transfer area must be large. When used in an Organic Rankine Cycle in which the water is replaced by an organic fluid, a larger quantity of the organic fluid is required. This increases the process cost.
Also, air-cooled absorbers have been known for a long time now, but their use is very limited due to the low coefficient of performance (COP) and high capital investment. A high efficiency, low capital cost air-cooled absorber is desirable in heat pumps and refrigeration applications, due to the environment benefits and energy conservation. A typical direct air-cooled absorber consists of a number of finned tubes connected in parallel between a top header and a bottom

header. The refrigerant vapors, preferably steam, and an absorbent solution is conveyed through the finned tubes from the top header to the bottom header. The cooling air flows outside the finned tubes approximately perpendicular to them. On the outer side of the finned tubes, to compensate for the low heat transfer coefficient of air, fins are provided for increasing the transfer area. The refrigerant vapors are absorbed in the absorbent solution in the finned tubes and the heat of absorption so produced is removed by the cooling air flow. The dilute absorbent solution is then collected by gravitation in the bottom header. A drawback of the direct air-cooled absorbers is that it is bulky in size. This is due to lower heat and mass transfer coefficient in a vertical falling film type absorption process in the vertical tubes of direct air cooled absorber. The lower heat & mass transfer coefficient inside the finned tubes governs the heat transfer area, resulting in increased size of the absorber. Further, the direct air-cooled absorber is inefficient and involves high capital investment. Also, as most of the absorption occurs in the vertical tubes, a high flow rate of the mixture of the refrigerant vapors and the absorbent solution through the tubes can cause turbulence, which results in an excessive pressure drop, and, on the other hand, a quiescent flow causes a very low transfer coefficient.
There is therefore felt a need for an air-cooled condensation/absorption apparatus which overcomes the afore-mentioned drawbacks of the known air-cooled apparatus and provides an air-cooled condensation/absorption apparatus having a high transfer coefficient, is simple, compact and cost-effective, and provides high efficiency with a reduced heat transfer area.
OBJECTS
Some of the objects of the present disclosure, which the preferred embodiment herein satisfies, are as follows:

It is an object of the present disclosure to overcome the above listed drawbacks of the known air-cooled apparatus. Accordingly, an object of the present disclosure is to provide an air-cooled apparatus which can be configured as an absorber and a condenser, and which provides Uniform distribution of the vapors for improved condensation, gives a high transfer coefficient, is simple, compact and cost-effective, and provides improved heat transfer efficiency with a reduced heat transfer area.
It is another object of the present disclosure to provide an air-cooled apparatus which improves the ratio of the heat transfer area to the volume.
It is still another object of the present disclosure to provide an air-cooled apparatus in which the non-condensable gases are completely removed from the tubes.
These objects and other advantages of the present disclosure will be more apparent from the following description.
SUMMARY
In accordance with the present disclosure, there is provided an air-cooled apparatus comprising:
■ a reaction chamber for receiving vapor, said reaction chamber adapted to
perform a function alternatively selected from,
i) absorption, wherein said vapor is absorbed in a strong absorbent solution
to provide a dilute absorbent solution at the operative bottom of said reaction
chamber;
ii) condensation, wherein the heat from the vapor is extracted to provide a
condensate at the operative bottom of said reaction chamber;
■ a first inlet provided in said reaction chamber for introducing said vapor;

■ a second inlet provided in said reaction chamber for introducing said strong absorbent solution;
■ a plurality of heat pipes for conveying a heat exchanging fluid to perform a function alternatively selected from:
i) extracting the heat of absorption; ii) absorbing heat from said vapor;
wherein, a portion of said plurality of heat pipes is disposed within said reaction chamber to be in direct contact with a medium alternatively selected from said absorbent solution and said vapor; and
■ a heat sink provided in operative communication with said plurality of
heat pipes for extracting heat from said heat exchanging fluid by means of
cooling air.
In accordance with a preferred embodiment of the present disclosure, said first inlet is provided at the operative bottom of said reaction chamber and said second inlet is provided at the operative top of said reaction chamber forintroducing said vapor and said strong absorbent solution counter currently. Typically, said cooling air (107) is countercurrent with the strong solution (105). Typically, in this embodiment, wherein spraying means is provided in operative communication with said second inlet at the operative top of said reaction chamber for evenly distributing said strong absorbent solution in said reaction chamber.
In accordance with another preferred embodiment of the present disclosure, said first inlet is provided at the operative top of said reaction chamber for introducing said vapor to effect falling film condensation.
Preferably, in accordance with the present disclosure, said heat sink is positioned above said plurality of heat pipes.

Typically, in accordance with the present disclosure, said plurality of heat pipes have a dimpled fin configuration.
In accordance with the present disclosure, there is disclosed a method for providing condensation or absorption in an air-cooled apparatus, said method comprising the following steps:
■ receiving vapor in a reaction chamber to perform a function alternatively
selected from,
i) absorption, wherein said vapor is absorbed in a strong absorbent solution
to provide a dilute absorbent solution;
ii) condensation, wherein the heat from the vapor is extracted to provide a
condensate;
■ conveying a heat exchanging fluid through a plurality of heat pipes to
perform a function alternatively selected from:
i) extracting the heat of absorption; ii) absorbing heat from said vapor;
wherein, a portion of said plurality of heat pipes is disposed within said reaction chamber to be in direct contact with a medium alternatively selected from said absorbent solution and said vapor; and
■ extracting heat from said heat exchanging fluid by means of cooling air
passed through a heat sink provided in operative communication with said
plurality of heat pipes.
In accordance with a preferred embodiment of the present disclosure, the method comprises the step of introducing said strong absorbent solution at the operative top of said reaction chamber and said vapor at the operative bottom of said reaction chamber to effect the absorption.

In accordance with another preferred embodiment of the present disclosure, the method comprises the step of introducing said vapor at the operative top of said reaction chamber to effect falling film condensation.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The disclosure will now be described with the help of the accompanying
drawings, in which,
FIGURE 1 illustrates a conventional air-cooled absorber with vertical finned tubes;
FIGURE 2 illustrates a conventional air-cooled condenser with horizontal tube bank;
FIGURE 3 illustrates a preferred embodiment of the air-cooled apparatus configured as an absorber in accordance with the present disclosure; and
FIGURE 4 illustrates another preferred embodiment of the air-cooled apparatus configured as a condenser in accordance with the present disclosure.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The disclosure will now be described with reference to the accompanying drawings which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
FIGURE 1 of the accompanying drawings illustrates a conventional air-cooled absorber 10 for absorbing refrigerant vapors in an absorbent solution. The air-cooled absorber 10 includes a vertically positioned finned tube bank 12 placed between a top header 14 and a bottom header 16. The mixture of the refrigerant

vapors and the absorbent solution is introduced in the finned tube bank 12 via the top header 14. Air is blown over the tube bank 12 by a horizontally mounted fan (not shown in figure) in the direction 11. The refrigerant vapors are absorbed in the absorbent solution in the finned tube bank 12 to give a condensate medium containing refrigerant-absorbent solution. The condensate medium leaves the tube bank 12 at the bottom header 16 by gravitation. The exothermic absorption reaction generates heat which is extracted by the air. A drawback of the air-cooled absorber 10 is that since the mass transfer coefficient in the finned tubes governs the heat transfer area, the size of the condenser is bulky. Also, non-condensable gases get accumulated in the tube bank 12 affecting the efficiency. Further, the air-cooled absorber is inefficient and involves high capital investment. Also, as most of the absorption occurs in the vertical tubes, a high flow rate of the mixture of the refrigerant vapors and the absorbent solution through the tubes can cause turbulence, which results in an excessive pressure drop, and, on the other hand, a quiescent flow causes a very low transfer coefficient.
FIGURE 2 of the accompanying drawings illustrates a conventional air-cooled condenser 20 for condensation of organic fluid vapors in an Organic Rankine cycle. The air-cooled condenser 20 comprises a coiled tube bank 22 having fins 24. The organic fluid vapors enter the tube bank 22 at inlet 26a. Air is blown over the coiled tube bank 22 in the direction 21 by means of an induced draft fan mounted on the top. Due to heat rejection to the air, the organic fluid vapors are condensed and the condensate is discharged from the tube bank 22 at outlet 26b. To compensate for the low heat transfer coefficient of the air, the heat transfer area must be large. When used in an Organic Rankine cycle, in which the water is replaced by an organic fluid, a larger quantity of the organic fluid is required. This increases the process cost.

The present disclosure therefore envisages an air-cooled apparatus which is simple, compact and cost-effective, gives high transfer coefficient, provides improved heat transfer efficiency with a reduced heat transfer area, and prevents accumulation of non-condensable gases in the finned tubes. The air-cooled apparatus of the present disclosure can be configured as an absorber or a condenser. The apparatus comprises: a reaction chamber for receiving a vapor, and a strong absorbent solution when configured as an absorber; a plurality of heat pipes for conveying a heat exchanging fluid; and a heat sink provided in operative communication with the plurality of heat pipes. The condensation or absorption of the vapor occurs in the reaction chamber and the medium so obtained is discharged at the operative bottom of the reaction chamber by gravity. The heat exchanging fluid conveyed through the heat pipes is adapted to extract the heat of absorption or heat from the vapor to provide the condensation. In accordance with the present disclosure, a portion of the heat pipes is disposed within the reaction chamber to be in direct contact with the vapor or the absorbent solution. Cooling air is passed through the heat sink to extract heat from the heat exchanging fluid. The heat pipes have a dimpled fin configuration. The heat sink is typically positioned above the heat pipes.
FIGURE 3 of the accompanying drawings illustrates a preferred embodiment of the air-cooled apparatus of the present disclosure, configured as an absorber; the absorber is referenced by numeral 100 in the FIGURE 3. The absorber 100 is suitable for absorbing refrigerant vapors in a strong absorbent solution. The absorber 100 comprises a reaction chamber 103 having an operative top 103a and an operative bottom 103b. The refrigerant vapors are introduced at a first inlet 106 provided at the operative bottom 103b of the reaction chamber 103. The strong absorbent solution is introduced at a second inlet 105 provided at the operative top 103a of the reaction chamber 103. A spraying means 104 is provided in operative communication with the second inlet 105 at the operative

top 103a of the reaction chamber 103 for evenly distributing the strong absorbent solution in the reaction chamber 103. The refrigerant vapors and the strong absorbent solution are contacted in a countercurrent fashion. A plurality of heat pipes 101 are provided for conveying a heat exchanging fluid. A portion of the plurality of heat pipes 101 is disposed within the reaction chamber 103 to be in direct contact with the refrigerant vapors and the absorbent solution. A heat sink 102 is provided in operative communication with the heat pipes 101, preferably the heat sink 102 is positioned above the heat pipes 101. The strong absorbent solution sprayed through the spraying means 104 flows in the reaction chamber 103 in the form of even droplets. The refrigerant vapors flowing in the countercurrent direction are absorbed in the strong absorbent solution to generate a dilute absorbent solution. The heat exchanging fluid conveyed through the heat pipes 101 extracts the heat of absorption to get vaporized. The vaporized heat exchanging fluid is cooled and condensed by cooling air passed through the heat sink 102 in the direction 107. The air-cooled absorber 100 gives uniform mixing of the absorbent solution and the refrigerant vapors, thereby providing high efficiency. Also, there is no accumulation of non-condensable gases in the heat pipes 101. The design in compact and uses dimpled finned heat pipes for enhanced heat transfer.
FIGURE 4 of the accompanying drawings illustrates a preferred embodiment of the air-cooled apparatus of the present disclosure, configured as a condenser; the condenser is referenced by numeral 200 in the FIGURE 4. The condenser
200 is particularly suitable for condensing organic fluid vapors in an Organic Rankine cycle. The condenser 200 comprises a reaction chamber 203 having an operative top 203a and an operative bottom 203b. The organic fluid vapors are introduced at a first inlet 205 provided at the operative top 203a of the reaction chamber 203, for facilitating falling film condensation. A plurality of heat pipes
201 are provided for conveying a heat exchanging fluid. A portion of the

plurality of heat pipes 201 is disposed within the reaction chamber 203 to be in direct contact with the organic fluid vapors. A heat sink 202 is provided in operative communication with the heat pipes 201, preferably the heat sink 202 is positioned above the heat pipes 201. The organic fluid vapors flow downwards by gravity. The heat exchanging fluid conveyed through the plurality of heat pipes 201 is adapted to extract heat from the organic fluid vapors and thereby condense the vapors to give an organic fluid condensate medium which is discharged at the operative bottom 203b. The heat exchanging fluid extracts the heat from the organic fluid vapors and gets vaporized. The vaporized heat exchange fluid is cooled and condensed by cooling air passed through the heat sink 202 in the direction 204. The condenser 200 provides improved heat transfer efficiency with a reduced heat transfer area.
TECHNICAL ADVANTAGES
An air-cooled apparatus, as described in the present disclosure has several technical advantages including but not limited to the realization of: the air-cooled apparatus can be configured as an absorber or a condenser, and provides uniform distribution of the vapors for better condensation, gives a high transfer coefficient, is simple, compact and cost-effective, and provides improved heat transfer efficiency with a reduced heat transfer area; improves the ratio of the heat transfer area to the volume; and provides complete removal of the non-condensable gases from the tubes.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the invention as it existed anywhere before the priority date of this application.
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 air-cooled apparatus comprising:
■ a reaction chamber (103, 203) for receiving vapor, said reaction
chamber (103, 203) adapted to perform a function alternatively selected from,
i) absorption, wherein said vapor is absorbed in a strong absorbent solution to provide a dilute absorbent solution at the operative bottom (103b) of said reaction chamber (103); and
ii) condensation, wherein the heat from the vapor is extracted to provide a condensate at the operative bottom (203b) of said reaction chamber (203);
■ a first inlet provided in said reaction chamber (103, 203) for introducing said vapor;
■ a second inlet provided in said reaction chamber (103) for introducing said strong absorbent solution; and
■ a plurality of heat pipes (101, 201) for conveying a heat exchanging fluid to perform a function alternatively selected from:
i) extracting the heat of absorption;
ii) absorbing heat from said vapor;
wherein, a portion of said plurality of heat pipes is disposed within said reaction chamber (103, 203) to be in direct contact with a medium alternatively selected from said absorbent solution and said vapor; and
■ a heat sink (102, 202) provided in operative communication with said
plurality of heat pipes (101, 201) for extracting heat from said heat exchanging
fluid by means of cooling air.
2. The air-cooled apparatus as claimed in claim 1, wherein said first inlet
(106) is provided at the operative bottom (103 b) of said reaction chamber (103)
and said second inlet (105) is provided at the operative top (103 a) of said

reaction chamber (103) for introducing said vapor and said strong absorbent solution counter currently.
3. The air-cooled apparatus as claimed in claim 1, wherein said cooling air (107) is countercurrent with the strong solution (105).
4. The air-cooled apparatus as claimed in claim 2, wherein spraying means (104) is provided in operative communication with said second inlet (105) at the operative top (103a) of said reaction chamber (103) for evenly distributing said strong absorbent solution in said reaction chamber (103).
5. The air-cooled apparatus as claimed in claim 1, wherein said first inlet (205) is provided at the operative top (203a) of said reaction chamber (203) for introducing said vapor to effect falling film condensation.
6. The air-cooled apparatus as claimed in claim 1, wherein said heat sink (102, 202) is positioned above said plurality of heat pipes (101, 201).
7. The air-cooled apparatus as claimed in claim 1, wherein at least some of said plurality of heat pipes (101, 201) has a dimpled fin configuration.
8. A method for providing condensation or absorption in an air-cooled apparatus, said method comprising the following steps:
■ receiving vapor in a reaction chamber to perform a function alternatively selected from,
i) absorption, wherein said vapor is absorbed in a strong absorbent solution to provide a dilute absorbent solution;
ii) condensation, wherein the heat from the vapor is extracted to provide a condensate;

■ conveying a heat exchanging fluid through a plurality of heat pipes to
perform a function alternatively selected from:
i) extracting the heat of absorption;
ii) absorbing heat from said vapor;
wherein, a portion of said plurality of heat pipes is disposed within said reaction chamber to be in direct contact with a medium alternatively selected from said absorbent solution and said vapor; and
■ extracting heat from said heat exchanging fluid by means of cooling
air passed through a heat sink provided in operative communication with said
plurality of heat pipes.
9. The method as claimed in claim 7, which comprises the step of introducing said strong absorbent solution at the operative top of said reaction chamber and said vapor at the operative bottom of said reaction chamber to effect the absorption.
10. The method as claimed in claim 7, which comprises the step of introducing said vapor at the operative top of said reaction chamber to effect falling film condensation.