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

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, thereby 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.

Heat pipes are defined as systems employing closed evaporating-condensing cycles for transporting heat from a location of heat generation to a location of heat reception capable of transporting large amount of heat with small temperature gradient. They are configured in

various shapes and geometry and may optionally use a capillary structure or wick to facilitate return of the condensate. A heat pipe may be represented by a tube with both ends sealed and partially filled with liquid, one end of which is capable of acting as an evaporator and the other end acting as the condenser. Such heat pipes can continuously transfer heat from the hot end to cold end. A heat pipe capable of controlling the heat transfer is known as switchable heat pipe.

Switchable heat pipes as effective heat transport devices have been developed for a variety of applications in space technology, refrigeration, air-conditioning, electronic cooling, etc.

Prior art is based on two approaches: a. To isolate the condenser and evaporator using various types of valves which are externally operated. Ways of implementing them are disclosed in US Patent 6,167, 955 and US Patent 6,047, 766. b. A common manner to achieve switchable heat pipes is to prevent the condensate from flowing back to the evaporator. In this case the evaporator gradually dries out and the heat transfer seizes to take place. Various way of implementing such a process is disclosed in US Patents 5159972,5771967, 4974667,4026348 and 4437510.

In these patents, the switching mechanisms are implemented as follows: In US Patents 5,159, 972 & 4,026, 348 controls the rate of heat transfer by controlling the amount of condensate that flows back to the evaporator. However the introduction of an additional bulb to hold the condensate significantly increases the void volume, which in turn increases the activation energy of the heat pipe.

In US Patent 6,167, 955 the flow of heat transfer fluid is regulated in response to changes detected by a sensor. In this patent the objective is achieved by disposing the valve between the first section and second section of the heat pipe. This valve regulates the flow of heat transfer fluid between the first section and the second section of the heat pipe in response to change detected by the heat pipe. In this case the construction of the valve is complex and expensive.

In US Patent 5,771, 967 a means is provided whereby temperature is actively controlled to within a narrow range while heat transport varies over a wide range. In this patent a sliding wick has been used, the position of which is controlled by means of a temperature sensitive metal strip. Whenever a discontinuity occurs in wick, the heat pipe seizes to operate. This system has an additional component that makes the system complex in construction. and operation. The limitation is that once it is set for a particular temperature range, this heat pipe would not operate over another temperature range.

In US Patent 4,974, 667 heat is transferred intermittently by stopping the condensate from flowing back to the evaporator.

In US Patent 4437510 an unidirectional flow of heat is achieved using a check valve, which is operated by very low pressure that is placed in the vapour channel of heat pipe and allows the vapour to flow only in the forward direction from heat source to heat sink.

An ideal switchable heat pipe should be compact, simple to operate with minimum number of components, should have low thermal mass and internal voids. The prior art on switchable heat pipes listed above do not satisfy all these criteria and hence the long felt need to design heat pipes that would meet such requirements.

Heat driven sorption refrigeration cycles have existed in literature since 1909, and refrigerators are commercially available since 1920's. Environment friendly solid sorption systems with non-polluting refrigerants can efficiently use natural gas or solar energy as primary energy. Further this provides a system with no moving parts making it silent and maintenance free. Adsorption heating and cooling is therefore a good alternative to classical vapor compression systems. Adsorption cooling units are attractive as they can be operated at temperatures in which liquid absorption systems cannot work. The desirable features are high coefficient of performance (COP), high specific cooling power (SCP) and the thermodynamic efficiency, which is the ratio between the COP and the Carnot COP.

The thermodynamic efficiency of the adsorption heat pumps is much lower than that of the conventionally employed compression heat pumps. Adsorption heat pumps are generally suitable for waste heat and solar energy based operation.

US Patent. 4,183, 227 disclose an adsorption based heat pump providing semi- continuous or substantially continuous refrigeration and/or heating. The limitations of such systems are intermittency in supply of useful cooling or heating effects and varying heat delivery temperatures.

Continuous delivery of output with small temperature variation is achieved through 'regenerative cycles'in which at least two reactors operate out of phase with internal heat recovery. US Patent 5,347, 815, US Patent 5,046, 319 of Jones, and US Patent 4,694, 659, US Patent 4,610, 148 of Shelton disclose various ways of implementing separate heat transfer fluid loop passing through the bed for regeneration. Heat transfer fluid loop in the regenerative cycle helps increase COP. However, in such systems pumps are required to circulate the heat transfer fluids through the beds, valves and their control systems are needed to regulate and divert the flow in various loops. This results in operational complexity and increased capital cost due to requirements of pumps valves and their controls. Such systems are not suitable for very small capacities (e. g. 50 to 500 W).

US Patent 5,847, 507 discloses an efficient adsorption based thermal compressor which used heat recycling. The system uses a thermal storage device for storing the heat released during adsorption which is used in next cycle during generation. Technology for heat transfer fluid loops is disclosed in US Patent 5,847, 507. Its cost is high and requires thermal storage,

pumps and associated controls. These systems are also not suitable for very small capacities (e. g. 50 to 500 W).

US Patent 4,765, 395 and US Patent 5,079, 928 disclose a scheme of cascading reactors, each using a solid adsorbent and refrigerant. Heat released during adsorption in one module is used for generation in the subsequent module. COP is increased by exchanging heat between the reactors. But, this arrangement is not appropriate for small refrigeration systems.

US Patent 5,477, 705 discloses an adsorption system in which the reactor has separate compartments. It has means for circulation of heat transfer fluid through hot and cold reactors in such a fashion that a solid sorbent temperature front successively passes through the first compartment to the last and vice versa. This allows the efficient recycling of heat. However this requirement of several valves and controls complicates the system and increases the capital cost. Literature review 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) on solar adsorption systems indicates that to produce simple and cost effective devices more attention is needed to reduce the number of valves.

US Patent 4,594, 856 describes a single stage pressure equalization technique, which increases the COP, but the complexity of the system makes this system inappropriate for small capacities.

Cycle time plays an important role in determining the compactness of the system. Cycle time can be decreased in adsorption refrigerators and heat pumps by improving heat and mass transfer rates. But, increasing heat transfer area to increase heat transfer rates leads to increase in thermal mass which increases thermal cycling losses and leads to reduction in COP.

The present invention addresses drawbacks of the prior art.

The desirable features of the adsorption refrigeration system are: a. improved COP b. high specific cooling power leading to compact unit c. regeneration without separate fluid loops d. reduced cycle time e. simple operational controls f. flexibility of using waste heat SUMMARY OF INVENTION The main object of the invention is to provide system based on adsorption cycle having high coefficient of performance (COP), high specific cooling power (SCP) with easy operability and lower cycle times using novel adsorption modules which are easy to fabricate and overcome the problems of low thermal conductivity of adsorbents, without increasing the thermal mass of the system. It also relates to refrigeration cum heating system that can be

heated by various heat sources like solar energy, direct fuel fired systems and waste heat fired systems using said adsorption module. Further, it relates to switchable heat pipes with a system to actuate or isolate hot end from the cold end to transfer heat intermittently as per the requirement.

One of the objects 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 increasing 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 system of"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.

Another object of the invention is to provide low cost and compact refrigeration cum heating system, based on adsorption refrigeration cycle that can be heated by various sources like solar energy, direct fuel firing and waste heat.

Another object of the invention is to provide a system comprising of a plurality of adsorption modules operating out of phase, to give continuous refrigeration and/or heating.

Yet another object of the invention is to increase the COP of the system without a separate loop circulating the heat transfer fluid.

Another object of the invention is to provide regeneration using multi stage pressure equalization process.

Yet another object of the invention is to reduce cycle time without affecting COP.

Yet another object of the invention is to reduce life cycle cost of the adsorption system.

Another object of the invention is to use waste heat as heat source Yet another object of the invention is to provide a means for simple control of the system Another aspect of this invention relates to switchable heat pipes using a system for actuating or isolating the evaporator or condenser capable of transferring heat intermittently when desired, based on parameters of the system for applications where a common evaporator is connected to multiple condensers and enabling operating selective set of condenser where plurality of evaporators are connected to a single condenser Another object of the invention is to provide a method for isolation of heat pipes as per need and application in a system of multiple heat pipes in the case of adsorption refrigeration module, which is to be periodically heated and cooled. For example, in the case of a tailored switchable heat pipe as in this invention, during the adsorption phase when the module needs to be cooled, the cooling heat pipe with its evaporator integrated with the module would be operative, while the heating heat pipe whose evaporator is integrated with the module would be switched off.

Another object of the invention is to provide means for the isolation of heat pipes as per need and application in a system of multiple heat pipes in the case where, heat transfer rate is to be varied while exchanging heat between to fix temperature source and sink. Heat transfer rate can be varied, in such a situation, by varying the number of active heat pipes.

Another object of the invention is to provide a cost effective means of isolating heat pipes as per need and application in a system of multiple heat pipes in a system of multiple heat pipes in case of application where several heat pipes are to be switched on and off as per a desired sequence. It is also possible to pinch multiple squeezable tubes fixed on a large number of heat pipes using a single low cost drive mechanism.

Yet another object of the invention is to provide for a simple, easily implementable and maintainable means for the isolation of heat pipes as per the need and application.

This invention provides a compact refrigeration cum heating system as described in figure 1 comprising a judicious combination of a heat source

0 set of adsorption modules that operate out of phase, to give continuous refrigeration and/or heating, switchable heat pipes in thermal contact with the wall and/or partition of the adsorption modules, condenser, evaporator, heat pipes and heat recovery unit functioning to provide regeneration resulting in high COP, reduced cycle time, high specific cooling power and thermodynamic efficiency.

The adsorption module comprises (FIG. 2) a. A main containment vessel in which adsorbent is filled b. Two or more"passages", in thermal contact with the containment vessel for heat transfer c. The containment vessel and the"passages"preferably constructed of high conductivity material such as Aluminum The switchable heat pipes as described in figure 4 comprises of The evaporator and the condenser part of the heat pipe are connected to each other through a squeezable tube/hose.

A single evaporator may be connected to multiple evaporators or vice versa by using multiple squeezable pinchable tubes.

A particular condenser or evaporator is isolated from the remaining condensers and evaporators by simply pinching the corresponding squeezable tube.

Pinching of the tubes may be done using any mechanical means, as desired by the application.

Operation of the controllable heat pump is effected by tilting the condenser "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 remove the heat from the module 500. At any given point of time only one of the two heat pipes 504,531 is operational. The nodule wall 550 that is preferably made of high conducting material performs the function of fin attached to the 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.

FIG. 2 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 remove the heat from 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 the 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.

FIG. 3 shows details of the module piping for a set of two modules 500, 600.

Each module 500/600 is made up of a containment vessel 550 containing suitable adsorbant and the containment vessel 550 which is in thermal contact with hot end and cold ends of

switchable heat pipes. Size and number of such sets may be varied depending on the desired capacity. Module 500 is in thermal contact with hot end 504 and cold end 531 of switchable heat pipe. Similarly module 600 is in thermal contact with hot end 604 and cold end 631 of switchable heat pipe. Either hot or cold end is operational at any instant. The modules 500,600 are filled with the adsorbent and have outlets 552/652, which has a mesh of suitable density to prevent adsorbent particles from escaping along with the refrigerant. This exit has a three-way connector 553, 653. One side is used for connecting the two modules through a valve 711 and the other side 702 leads to the condenser and evaporator. Incorporation of plurality of modules enables continuous cooling and heating effect.

Two adsorption modules 500, 600 are connected through valve 711 to allow pressure equalization between the two adsorption modules 500,600, at end of generation and/or adsorption phases. The refrigeration sub-system operates on an adsorption refrigeration cycle with pressure equalization for heat recovery. The two-module operate out of phase, i. e. one module is being heated while the other is being cooled. During pressure equalization between two modules or two sets of modules, refrigerant from a module or a set of module at high pressure is allowed to flow to a module or a set of modules at relatively lower pressure. This method of regeneration between two modules or sets of modules reduces the requirement of heat input from the external heat source in the generation phase and thus increases COP.

Pressure equalization between two sets of modules is single stage pressure equalization. Multi-stage pressure equalization is achieved if pressure equalization is effected sequentially between three or more modules or sets of modules. Vapour and heat regeneration efficacy increases with increase in number of stages of regeneration. Multi-stage regeneration eliminates the need for heat transfer fluid loops and the associated complex valve arrangements and controls otherwise needed for regeneration. Vapour equalisation technique enhances COP of the system and also reduces cycle time. Cycle time is reduced because the time required to equalize pressure is a fraction of the time required to regenerate the heat using heat transfer fluid loops. Also the auxiliary power required to pump the heat transfer fluids is eliminated.

Adsorption modules 500, 600 used in refrigeration cum heating system, are shown in FIG. 1. The thermal bonding between adsorption module and hot/cold ends can be achieved by co-extruding the three tubes or by welding the two smaller diameter pipes to the main module tube or by any other suitable means.

The module design may be further modified based on the application requirements.

Shape of module and the heat pipes may be varied on the basis of the ease of fabrication or other application constraints. Diameters of the module and heat pipe are governed by the desired capacities. Number of heat pipes of each type can be varied to increase or decrease the heat transfer rate. In some cases, the heat pipes either for heating or cooling are not required.

Due to some constraints, it might not be possible to make the heat pipe run along the complete

length of the module. Heat pipes may be thermally affixed on the inner side of the module wall, or they may be co-extruded along with the main pipe or affixed by any other means. But the basic idea of using the heat pipes for supplying and removing the heat from the adsorption modules, and integrating the same with the walls of the module to avoid the need of separate fins to facilitate heat transfer within the adsorbent bed still holds. In this design the wall of the module acts as a fin to facilitate heat transfer thereby reducing the overall thermal mass of the system, leading to lower cycle times and higher COP.

Hot/cold ends 501, 534,504, 531,604, 631 of switchable heat pipes, used in refrigeration cum heating system, use a system to isolate hot end from cold end or vice versa.

FIG. 4 shows switchable heat pipes, which consists of hot end, evaporator 501 and cold end, condenser 504, flexible tube 502 and pincher 505. The heat receiving section is integrated into the heat source and the heat giving section is integrated into the heat sink. When the heat pipe is in operation, the flexible tube is in the un-pinched position. Fluid in the hot end 501 evaporates absorbing heat from the heat source and passes to the cold end 504 and/or 604 passing through the flexible tube 502 and/or 602. In the cold end these vapours condense, delivering the heat. The condensate is transferred back to the hot end 501 due to capillary action of the wick or it drains back due to the gravitational action. To switch off the heat pipe, the flexible tube 502,602 is pinched using the pinchers 505,605, 507, 607. This isolates the hot end 501 and the cold end 504 and the heat pipe ceases to operate.

This novel construction and arrangement gives this heat the flexibility to use it in diverse ways. Heat pipe cross-section used may be of any shape (such as circular, elliptical, rectangular, etc.). Cross-sectional area of the heat pipe is decided on the basis of the desired capacity of heat transfer. The flexible tube used to connect the heat receiving section and the heat giving section can be made of any material as long as it can be pinched/squeezed to isolate the two sections as long as the material of the flexible tubing is compatible with the fluid used in the heat pipe. A wick may be provided on the inner wall of the heat receiving section, heat giving section and flexible tubing to facilitate the draining back of the fluid. There is no restriction on the type of wick that should be used, except that in the flexible tube section the wick should be also flexible. A sealant has to be applied to seal the flexible tube and metal tube joints. Sealant should be able to withstand pressures at which heat pipe is supposed to operate.

Any material may be used for making the heat receiving or condenser sections 501,504 of the heat pipe as long as it is compatible with the working fluid. Any pinching mechanism may be used to pinch the flexible tube 502 depending on the application.

In refrigeration cum heating system, as shown in FIG. 1, the design of the evaporator 707, condenser 703 and the heat recovery tank 709 may vary as per the application, location, etc. Purpose of the heat recovery tank is to recover the heat released from the adsorption modules 500,600 during the adsorption phase and use it for heating purposes. Heat is being

transferred from the adsorption modules to the heat recovery tank 709 using the heat pipes 504, 531,604, 631. Each heat recovery tank 709 will have heat pipes coming from at least two adsorption modules 500,600 and each heat pipe 504, 531,604, 631 would be operational during the adsorption phase of the respective module. Condenser 703 shown in FIG. 1 is an evaporative condenser. Design of the same will depend on space and location constraints. Each condenser should condense refrigerant coming through at least two adsorption modules during the generation phase but only one of them is operational at any given time. These will then lead to the evaporator 707, which has to be customized for a particular application like for chilling water, for producing ice or for cold storages, etc.

The system described in this invention may also function without pressure equalisation.

In such cases the COPs obtained will be low, as compared to the system operating with heat regeneration as described above.

FIG. 4 shows the design of the disclosed heat pipe for simplest application, i. e. transferring heat from one source to one receiver. It consists of an evaporator 501, condenser 504, squeezable tube 502 and pincher 505. The evaporator 501 is integrated into the heat source and the condenser 504 is integrated into the heat sink. When the heat pipe is in operation, the squeezable tube 502 is in the un-pinched position. Fluid 506 in the evaporator 501 evaporates taking heat from the heat source and moves to the condenser 504 passing through the squeezable tubing. In the condenser 504 these vapors condense, giving away their heat and drain back due to gravity in the evaporator 501. To switch off the heat pipe, the squeezable tube 502 is pinched using the pinchers 505. This isolates the evaporator 501 and the condenser 501 and the heat pipe seizes to operate. The amount of fluid 506 in the heat pipe is determined based on the desired operating temperature level of the heat pipe. Beyond this temperature limit, fluid 506 exists in vapour state and there is no condensation in 504 hence no evaporation in 501. Thus the heat pipe seizes to operate at and above this temperature. The simple pinchable heat pipe design is easy to operate and several heat pipes can be controlled using a single rotating shaft with appropriate cams to push the pinchers. This effective heat pipe design will be low in cost and is suitable for applications where a very large number of independent loads are to be switched on and off.

FIG. 4 shows example of a heat pipe that can be used for transferring the heat from a single source to multiple receivers, either simultaneously or one at a time. It has two condensers 504 and 604, one evaporator 501 and two pinchers 505 and 605, one for each condenser. To deactivate a particular condenser, the corresponding pincher is used to pinch the squeezable tube. In order to completely switch off the heat pipe, both pinchers are pinched simultaneously.

This heat pipe is an effective solution to alternate or sequence heating of two loads.

FIG. 4 gives an example of a heat pipe that can be used for transferring heat from multiple source to single receiver, either simultaneously or from one evaporator at a time. It has

two evaporators 531 and 631, one condenser 534, and two pinchers 507 and 607, one for each evaporator. To deactivate a particular evaporator, the corresponding pincher is used to pinch the squeezable tube. In order to completely switch off the heat pipe, both the pinchers are pinched simultaneously. A sealant has to be applied to seal the squeezable tube and metal tube joints. Sealant should be able to withstand pressures at which heat pipe is supposed to operate.

This heat pipe is an effective solution to alternate or sequence cooling of two loads.

FIG. 4 gives an example of a switchable heat pipe without pinching means consisting of evaporator 501 and condenser 504. The evaporator 501 and condenser 504 may be a continuous rigid tube capable of bending. Optionally squeezable tube 502 connects evaporator 501 and condenser 504. Heat pipe is controlled by retaining fluid in liquid state in the condenser thereby depriving the evaporator from access to this fluid. Heat transfer rate using the heat pipe and the cut out temperature at which the heat pipe stops transferring heat is controlled by tilting the condenser and retaining fluid in liquid state. Condenser 504 can be tilted using suitable means. This means and method of control of heat transfer rate is ideal for low cost applications.

This novel construction and arrangement provides flexibility to use it with diverse systems as listed below : a. Heat pipe cross-section used may be of any shape (like circular, elliptical, rectangular, etc.) b. The squeezable tube used to connect the evaporator and condenser can be made of any material as long as it can be pinched/squeezed to isolate the two section as long as the material of the squeezable tubing is compatible with the fluid used in the heat pipe. c. Number of evaporators and condensers used in each heat pipes may be varied as desired by the application. d. A wick may be provided on the inner wall of the evaporator, condenser and squeezable tubing to facilitate the draining back of the fluid. There is no restriction on the type of wick that should be used, except that in the squeezable tube section the wick should be also squeezable. e. Any material may be used for making the evaporator or condenser sections of the heat pipe as long as it is compatible with the working fluid. f. Any pinching mechanism may be used to pinch the squeezable tube depending on the application. g. The evaporator and condenser may be a continuous rigid tube capable of bending enabling control of heat transfer rate and maximum operating temperature.

The invention is now illustrated with non-limiting examples.

Example 1 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 : 1. Evaporator temperature-5°C 2. Generator outlet temperature 199°C 3. Adsorber outlet temperature 40°C 4. Maximum pressure in module 23 bar 5. Pressure factor of safety 1.5 6. Intensity of solar radiations 750 W/m2 7. Duration for which radiation is available 6 hrs ) 8. Efficiency of solar collector 45% 9. Dry bulb temperature 30°C 10. Wet bulb temperature 22°C 11. Minimum wall thickness 1 mm 12. Diameter of Heat pipes 6.35 mm i 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 i 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) up to 0.9, 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.

Example 2.

The results of an adsorption refrigeration cum heating system, using adsorption cycle with pressure equalisation for heat regeneration, with activated carbon/ammonia as working adsorbent-adsorbate pair are given to serve as a non-limiting example of the present invention.

Table 1 presents the simulation results for a system using solar collector as the heat source. Some of the important parameters that are considered fixed for the system in this example for simulation are as follows : 13. Evaporator temperature-5°C 14. Generator outlet temperature 199°C 15. Adsorber outlet temperature 40°C 16. Maximum pressure in module 23 bar 17. Pressure factor of safety 1.5 18. Intensity of solar radiations 750 W/m2 19. Duration for which radiation is available 6 h 20. Efficiency of solar collector 45% 21. Dry bulb temperature 30°C 22. Wet bulb temperature 22°C 23. Minimum wall thickness 1 mm 24. Diameter of Heat pipes 6.35 mm 25. Shape of Module Circular 26. Shape of Heat pipes Circular Table 1: Simulation results for an optimised system using solar collector as heat source.

Material Module No. of Diameter heat pipes Cycle Time SCP Weight of ice (mm) COP (min) (W/kg) (kg/m2. day) Aluminium 38. 1 1 0. 40 57. 7 162 6. 574 SS304 38. 1 1 0.38 34.9 143 6.143 Aluminium 38.1 2 0.39 16.0 312 6.303 Though this system can operate with various heat sources, one of the very common applications of the adsorption systems is solar refrigeration. Solar refrigeration is an important use of solar energy because the supply of solar energy and the demand for cooling are greatest during the same season. It has the potential to improve the quality of life of people who live in areas where the supply of electricity is far from sufficient. The success of solar cooling is dependent on the availability of low cost and high performance of solar collectors. In the disclosed refrigeration cum heating system if solar energy is used as the input, solar collector contribute to more then 80% of the system cost. Still the costs have been brought down

significantly by reducing the solar collector area required per kg of ice produced per day and the cost of adsorption modules. This has been made possible in the present invention due to high COP of the system with low cycle time. After optimizing the system to minimize the system cost the overall system is expected to cost one-third of the currently commercially available solar refrigeration system. In addition to that system is very compact and gives hot water as an additional utility.