FORM - 2

THE PATENTS ACT, 1970
(39 OF 1970)
COMPLETE SPECIFICATION
(See Section 10)
TITLE OF INVENTION
ADSORPTION MODULE"

(a) INDIAN INSTITUTE OF TECHNOLOGY Bombay (b) having administrative office at Powai, Mumbai 400076, State of Maharashtra, India and (c) an autonomous educational Institute, and established in India under the Institutes of Technology Act 1961.
The following specification particularly describes the nature of the invention and the manner in which it is to be performed.

FIELD OF INVENTION
' '
This invention is related to easy to fabricate design of, adsorption modules that overcome the problems of low thermal conductivity dsorbents, without increasing the thermal mass of the system. Further the adsorption modute, when , integrated into system configurations involving condensersv evaporators and-' other components, to implement different cycles, deliver characteristics of lower cycle times, high coefficient of performance (COP), high specific cooling power (SCP) with easy operability
BACKGROUND OF INVENTION
Certain substances have the property of adsorbing some fluids at low temperatures and desorbing them at high temperatures. Adsorption Module is an apparatus, which facilitates the containment of the adsorbent and adsorbate and the process of its heating and cooling. These substances are selective in nature, i.e. they adsorb only specific fluids. This phenomenon can be used for separation of fluids. Alternatively, in sorption cooling applications these are used to adsorb refrigerants at low temperatures and pressure, and desorb them at high temperature and pressure.
The key problem in adsorption systems is low conductivity of the adsorbents and that of the adsorption bed, which in turn effects the cycle time of the system. An important aspect in the design of adsorption modules is to achieve higher heat transfer rates to and from the adsorption beds that results in low cycle time. To make the system compact number of cycles per unit time need to be increased resulting in reduced requirement of adsorbant and adsorbate.
It is desirable to have adsorption modules that exhibit the following characteristics:
a. High thermal conductivity of the adsorbent bed
b. High rates of heat transfer to and from the bed
c. Low thermal mass of the adsorption module
d. Low thermal mass of adsorbent module while having high rates of heat
transfer
e. High affinity for adsorbate per unit quantity of adsorbent.
Past, attempts to achieve the above objectives have been any of the following
four approaches:
a. Use of binders and additives (e.g. graphite) with good thermal conductivity or metallic foam, which are well bound with adsorbent powder: US Patent 4,138,850 uses a solid zeolite adsorbent mixed with a binder, pressed, and sintered into divider panels and hermetically sealed in containers. Such systems are prone to loosing the contact between the adsorbent and the heat transfer surface as the system is cycled repeatedly leading to reduced thermal conductivity over a period of time and thereby reducing its specific cooling power. This increases the cost of the system.

b. Use of consolidated samples (like bricks): US Patent 4,637,218 uses zeolites
that are sliced into bricks or pressed into a desired configuration. However,
the fabrication of this type of module is complex.
c. Use of compartmentalized reactors: US Patent 5;477,705: discloses an
apparatus for refrigeration employing a compartmentalized reactor,'As the
entire heat transfer surface area is not active at any given time, the total
surface area required in the system is much larger, there by adding to the
thermal mass, which in turn necessitates more heat to be" transferred to
achieve the required COP. This increases the size, weight and cost of the
system.
d. Use of metallic fins or coating metal tubes with the adsorbent: US Patent
4,548,046 relates to an apparatus for cooling or heating by adsorption of a
refrigerating fluid on a solid adsorbent. The operation employs a plurality of
tubes provided with radial fins, the spaces between which are filled or covered
with solid adsorbent such as zeolite 13X located on outside of the tubes.
US Patent 6,102,107 relates to a sorption cooling module employing a uniform adsorbent coating on a fin plate surface which does not build up on heat transfer medium tubes passing through the fin plates even in a dense plate configuration. The large number of small diameter tubes complicates the fabrication of such a system. The increased number of tubes and the joints enhances the possibility of leakage.
USP 5,518,977 relates to sorption cooling device, which employ adsorbent-coated surfaces to obtain a high cooling coefficient of performance. Thermal mass of the surface which is coated adds to the thermal mass, which leads to reduced COP. Also, with time the adsorbent coating might get dislodge due to cycling and/or thermal shocks.
In a review paper titled "Solar adsorption technologies for ice-making and air-conditioning purposes and recent developments in solar technology" by Wang and Dieng ("Literature review on solar adsorption technologies for ice-making and air-conditioning purposes and recent developments in solar technology", Renewable & Sustainable Energy Reviews, Vol. 5, pp. 313-342, 2001) conclude that some crucial points in the development of sorption systems still exists especially those related to problems of low specific cooling power of the machine and high investment costs. It also mentions that thermosyphons and heat pipes are one of the most convenient heat transfer devices for the solid and liquid sorption machines due to their flexibility, high thermal efficiency, cost-effectiveness and reliability.
However the thermosyphones and heat pipes disclosed in the prior art suffer from low heat transfer rates when used without fins and increase in thermal mass when used with fins.

SUMMARY OF INVENTION
Main object of the present invention is to provide design for_adsorption modules that make it possible to develop compact adsorption systems by .overcoming the problems of low thermal conductivity of adsorbents without ihcreasing the thermal mass of the adsorption modules, thereby increasing heat ..transfer rates and reducing cycle time while maintaining high efficacy of the cycles and processes in which they are used.
The other object of the invention is to achieve the low thermal mass using a set of passages to and from the containment vessels thereafter termed " passages".
It is another object of the invention to provide designs of "passages" that function as heat pipes that are in thermal contact with the wall of the containment vessels in diverse configurations.
It is yet another object of the invention to provide design of a system of "passages" preferably constructed of the high conductivity material.
It is yet another object of the invention to provide design of a system of "passages" that preferably enable the use of the containment vessel wall itself as the fin thereby eliminating the need for separate fins.
It is yet another object of the invention to provide design of a system of "passages" that preferably enable the use of the containment vessel wall and partitions as the fins thereby eliminating the need for separate fins.
Another object of the invention is to provide design of a system of "passages" with the option of increasing or decreasing number of the "passages" per containment vessel based on the desired cycle time.
Another object of the invention is to provide design of a systemjof "passages" in a manner to reduce the effective thermal mass at the same time achieving high COP and high SCP.
Another object of the invention is to provide design of a system of shared "passages" between multiple containment vessels in a manner to reduce the effective thermal mass at the same time achieving high COP and high SCP.
Yet another object of the invention is to provide design of a system of "passages" in a manner that is simple to fabricate, easy to operate and provide options for a wide range of application involving heat transfer.
Thus in accordance of the present invention the adsorption module comprises
FIG. 1)_
a. A main containment vessel in which adsorbent is filled
i. Two or more "passages", in thermal contact with the containment vessel for
heat transfer the containment vessel and the "passages" preferably constructed of high conductivity material such as Aluminum

"Passages" used for heat transfer in the present adsorption modules are means for transporting heat from the heat source to the module and/or from the module to the heat sink.
DETAILED DESCRIPTION OF THE INVENTION
FIG.1 shows the construction of the adsorption module in one of the "preferred
embodiments. Two tubes of smaller diameter 504, 531 are thermally attached to
the containment vessel 550 either by way of continuous line welding or by using
thermal paste. The two tubes of smaller diameter 504, 531 act as heat pipes,
which are used for supplying and removing the heat from the module. An opening
at one end of the containment vessel 550 with an outlet 552 lets the adsorbate
flow in_and out of the module.
One of the heat pipes 504, 531 acts as the means of transferring the heat to the module 500 and other acts as the means to remove the heat from the module. At any given time, only one of the two heat pipes 504, 531 is active. These heat pipes 504, 531 are in thermal contact with the containment vessel 550 that is achieved by either being in thermal contact with the wall of the containment vessel 550 or any internal partition of the containment vessel 551. As per this the containment vessel wall 550/partition 551 acts as fin leading to increase of the containment vessel surface area that is in contact with the adsorbent. This eliminates the need for separate metal fins, thereby reducing the overall thermal mass of the system. Lower thermal mass is a desirable property in case of applications pertaining to adsorption refrigeration or heat pumps. The design described herein achieves the objective of obtaining high rate of heat transfer along with low thermal mass.
Cross sectional area (CSA) of the containment vessel 550 is determined on the basis of amount of adsorbent to be packed in each module 500. As the "CSA" of the module 500 is increased, the fin effectiveness of the containment vessel wall 550 decreases, which in turn decreases the efficiency of heat transfer from the heat pipes 504, 531 to the adsorption module 500 and vice versa. An optimized "CSA" of the module 500 has to be selected based on the desired cycle time and compactness of the system. An optimum "CSA" needs to be arrived at based on the desired adsorption system compactness and COP. Increasing the number of passages 504, 531 for heat transfer can further increase fin effectivness of the containment vessel wall 550. All "passages" 504 used for supplying heat to the module 500 should preferably be equidistant from each other. Same should be done in case of cooling "passages" 531. Fabrication and type of the heat pipes 504, 531 to be used, is based on the desired capacity of heat transfer.
During operation, working fluid at the hot end takes heat from the surroundings to produce vapour, which is then transported to the cold end. At cold end this vapour is condensed on the walls and the liquid drains back to the lower hot end. Liquid drains back by the help of gravity, in case of gravity assisted heat pipes 504, 531, or through a wick due to capillary action. To facilitate the draining back of the liquid, groves or wick may be provided on the inner side of the heat pipe wall. The two side tubes of smaller diameters function as heat pipes 504, 531 that


are used to transfer heat to the adsorption module 500 and rernove the heaYfrbm the module 500. At any given point of time only one of the two heat pipes 504, 531 is operational. The module wall 550 that is preferably made of high conducting material performs the function of fin attached to t'fie heat pipes 504
531.
The module design disclosed in this invention may be used in a Wide range of applications including purification of gases, separation of gases, removal of contaminants from a gas stream, pressure wing adsorption, catalytic reactions, and removal or supply of heat during the reactions, etc.
In other embodiments, the CSA of the containment vessel 550 may be circular, square, rectangular, elliptical or any shape based on space constraints or the need to increase the surface area of the wall in contact with the adsorbate.
In another embodiment, the "CSA" of the "passages" 504, 531 may be circular, square rectangular, elliptical or any shape governed by the space constraints or the method of fabrication being adopted. The containment vessel 550 along with the "passages" 504, 531 may be extruded with "passages" 504, 531 integrated with the containment vessel wall 550 or partition 551. It would improve the fin effectiveness of the containment vessel walls 550.
In other embodiments, the number of "passages" 504, 531 for supplying and removing heat from the module 500 may be varied depending on the desired heat transfer rate. Increasing the number of "passages" 504, 531 increases the fin effectiveness of the module wall 550, resulting in reduction of time required to transfer the requisite amount of heat to and from the module 500.
In another embodiment, the "passages" 504 for supplying the heat to the module 500 is not necessary as in the case of applications where the module 500 is placed directly at the eye of a solar collector. Under such circumstances heat is supplied to the module 500 directly through radiation and the "passages" 531 are required to ensure removal of the heat from the module 500.
In another embodiment, the "passages" 531 for removal of heat from the module 500 is not necessary as in the case of applications where the module 500 is placed directly in cooling fluid stream. Under such circumstances heat is removed from the module 500 directly through the containment vessel wall 550 and the "passages" 504 are required to supply heat to the module 500.
In one of the embodiments, the "passages" 504, 531 run along the partial complete length of the module 500.
In yet other embodiments, the "passages" 504, 531 may be thermally in contact with the inner side of the containment vessel wall 550.
In one of the embodiments, the "passages" 504, 531 are constructed as "heat pipes".

In another embodiment, electric heater may be thermally in contact with the containment vessel wall 550 or partition 551.
In another embodiments, the "passages" 504, 531 may be press fitted' inside/outside the containment vessel wall 550 or partition 551.
Example
In order to establish the performance of the adsorption module, its performance has been evaluated for example in a model adsorption refrigeration system.
Some of the important parameters that are considered fixed for the model system are as follows:

a. b. c. d. Evaporator temperature Generator outlet temperature Adsorber outlet temperature Maximum pressure in module -5°C 199°C 40°C 23 bar
e. f.
9- Pressure factor of safety
Intensity of solar radiations
Duration for which radiation is available 1.5
750 W/m 6 hrs
h. i.
j-k. Efficiency of solar collector Dry bulb temperature Wet bulb temperature Minimum wall thickness 45% 30°C 22°C 1 mm
1. Diameter of Heat pipes 6.35 mm
The findings are:
a. As the module diameter increases the COP of the system increases and the
SCP decreases. Significantly high values of SCP, up to 400 W / kg of
adsorbent are achieved.
b. SS304 has conductivity of the order of 17.7 W/m °K, and Al has conductivity
of the order of 210 W/m °K. Aluminium gives a much higher COP in
comparison to Stainless Steel. Due to high conductivity of Al, the fin
effectiveness of the module wall is significantly increased. This leads to a
lower time required to transfer the desired amount of heat from heat pipe to
the adsorption module and vice versa, which in turn leads to a lower cycle
time. Also due to lower cost of Al , the contribution of the refrigeration sub¬
system cost decreases significantly, which in turn leads to a lower overall
system cost.
c. Increasing the number of heat pipes each for supplying and removing the heat
from the module decreases the cycle time leading to higher COP.
The system disclosed in the invention clearly brings out the advantages over the prior art in terms of the following:
a. High Coefficient of Performance (COP), due to low thermal mass, which is the
result of elimination of need for separate metallic fins.
b. Simple design, which is easy to manufacture, leading to low cost
c. High Specific cooling power in the range of 50 to 750 W/kg of adsorbent,
which is just 20 to 40 W/kg of adsorbent in case of prior art.

We claim:
1. An easy to fabricate adsorption module with reduced thermal mass
comprising:
a. a containment vessel filled with adsorbent
b. plurality of passages that are in thermal contact_or integrated into the wall
f and/or partition of the containment vessel so that wallpartition functions
as a fin.
2. The adsorption module as in claim 1, wherein the cross-section of the containment vessel is circular, square, rectangular, elliptical, or any other shape.
3. The adsorption module as claimed any one of the claims 1 -2, wherein the material of construction of the containment vessel is selected from materials such as metals, composite materials preferably with high thermal conductivity of atleast 1 W/m.K and being compatible with heat transfer fluids.
4. An adsorption module as claimed in any one of the claims 1-3 wherein the cross section of the passages is circular, square, rectangular, elliptical or any other shape.
5. An adsorption module as claimed in any one of the claims 1-4 wherein the passages are open at both ends allowing through flow of heat transfer fluids.
6. An adsorption module as claimed in any one of the claims 1-5 wherein the number of passages is varied as per the desired rate of heat transfer and fin effectiveness of the module wall.
7. An adsorption module as claimed in any one of the claims 1-6 wherein the containment vessel shell is co-extruded with the passages.
8. An adsorption module as in any one of the claims 1-6 wherein the passages are in thermal contact with the inner surface of the containment vessel wall of the module.
9. An adsorption module as claimed in any one of the claims 1-8 wherein the passages are in thermal contact with the partition(s) in the containment vessel of the module
10. The adsorption module as in any one of the claims 1- 9 wherein the passages run partially along the length of the module.
11. An adsorption module as claimed in any one of the claims 1-10 wherein the passages are optionally non linear.

12. An adsorption module as claimed in any one of the claims 1-11 wherein the
^sorbents include activated carbon (AC), calcium chloride, magnesium
chloride, stronsium chloride, zeolite, silica gel and there like.
13. An adsorption module as claimed in any one of the claims 1-12 wherein the adsorbate include ammonia, methanol, water and alcohols.
14. An adsorption module as claimed in any one of the claims 1-13 wherein the heating is optionally effected by a "non-flow" heat sources such as solar/electric heater and there like.
15. An adsorption module as claimed in any one of the claims 1-14 wherein the "passages" for supplying heat to the module is not necessary when the module directly receives heat through the containment vessel wall and the "passages" are only required to ensure removal of heat from the module.
16. An adsorption module as claimed in any one of the claims 1-14 wherein the "passages" for removal of heat from the module is not necessary when the module directly loses heat through the containment vessel wall and the "passages" are only required to ensure supply of heat to the module.
17. An adsorption module as claimed in any one of the claims 1-16 wherein the passages are closed at one end to function as a heat pipe.
Ageni

fr Prabuddha Ganguli "VISION - IPR"