FIELD OF THE DISCLOSURE

The present disclosure relates to a metal hydride heat pump.

More particularly, the present disclosure relates to a device for cyclic switching of heat transfer media in a metal hydride heat pump.

BACKGROUND

Metals or alloys react with hydrogen exothermic ally to produce metal hydrides, and the metal hydrides reversibly release hydrogen gas endothermically. LaNi ₅ H _x , MmNi ₅ H _x , MmCo ₅ H _x , FeTiH _x , VNbH _x and Mg ₂ CuH are common examples of metal hydrides which have an ability to occlude a significant amount of hydrogen and release a large amount of the heat of reaction. Various metal hydride devices are known, such as heat pumps/air conditioning devices, which utilize these properties of metal hydrides to provide heating and/or refrigeration. Hydrogen is used as a refrigerant and metal hydrides are used as absorbents.

A conventional metal hydride heat pump comprises a first receptacle filled with a first metal hydride, a second receptacle filled with a second metal hydride, the first and the second metal hydrides having different equilibrium dissociation characteristics, a hydrogen flow pipe connecting these receptacles, and heat exchangers provided in the respective receptacles. Typically, a heating output and a cooling output based on the heat generation and absorption of the metal hydrides within the receptacle is obtained by means of a medium flowing within the heat exchangers.

The metal hydride heat pump operates cyclically. A pair of different types of metal hydrides are used, viz., regenerating alloy A and refrigerating alloy B, as sorbents, and hydrogen as a refrigerant. In the first cycle of operation of the paired reactors of alloys A & B, alloy A discharges hydrogen using a first medium of high temperature as a heat source. The discharged hydrogen is absorbed by the alloy B and in the process heat is transmitted to a second medium, typically ambient air. In the second cycle alloy B desorbs hydrogen using a third stream of low temperature heat source. The discharged hydrogen is absorbed by alloy A and in the process heat is transmitted to the fourth stream, typically ambient air. Thus, the operation of the metal hydride heat pump requires each alloy to go through a temperature swing for charging and discharging.

Conventional systems have a set of two-way air valves for cycle changeover. This arrangement requires a minimum of eight air valves for the operation of the heat pump. Thus, several drive mechanisms of pneumatic, electric or electromagnetic type are required for operating the air valves, which increases the number of moving parts in the system, hence reducing its reliability. Furthermore, the air valves are connected to the reactor casing by means of multiple interconnecting ducting. This leads to an intricate and long ducting length. The interconnecting ducting and the air valves form a part of the thermal cycling, which results in an increased thermal inertia. Higher thermal inertia is highly undesirable for the system and results in reduced performance. There is therefore a need for a device for cyclic switching of heat transfer media in metal hydride heat pumps that overcomes the above-noted drawbacks of the conventional arrangements in metal hydride heat pumps.

OBJECTS

Some of the objects of the system of the present disclosure, which at least one embodiment herein satisfies, are as follows:

It is an object of the present disclosure to provide a device for cyclic switching of heat transfer media in a metal hydride heat pump. It is another object of the present disclosure to provide a device for cyclic switching of heat transfer media in a metal hydride heat pump which reduces thermal inertia and enhances performance. It is yet another object of the present disclosure to provide a device for cyclic switching of heat transfer media in a metal hydride heat pump which reduces pressure drop in the heat transfer media while flowing through the heat pump, thereby reducing the power consumption in running fans and blowers. One more object of the present disclosure is to provide a device for cyclic switching of heat transfer media in a metal hydride heat pump which gives uniform air distribution in the reactor.

It is still another object of the present disclosure to provide a device for cyclic switching of heat transfer media in a metal hydride heat pump which is compact, light in weight, and of reduced height, which decreases the drag forces on the vehicle on which the pump is mounted.

Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.

SUMMARY

In accordance with an embodiment of the present disclosure, there is provided a device for cyclic switching of heat transfer media in a metal hydride heat pump, said device comprising:

a first heat exchanger and a second heat exchanger;

a first valve and a second valve positioned between said heat exchangers, said first valve and said second valve are separated by a partition such that each valve defines a plenum for connecting internal ducts; a shell for containing said heat exchangers and said valves, said shell is adapted for defining flow paths for a plurality of heat transfer media, in which each of the flow paths transits through one of said heat exchangers via a means selected from one of said valves and one of said internal ducts.

In accordance with the present disclosure, each of said first valve and said second valve comprises a flap for changing the valve position during changeover of the reactor cycle. The flap of said valves can comprise an automated drive mechanism for changing the valve position. The valves can be four-port two position valves.

Typically, in accordance with the present disclosure, said first valve and said second valve are aligned one above the other defining said plenum therebetween.

In accordance with an alternative embodiment of the present disclosure, there is provided a device for cyclic switching of heat transfer media in a metal hydride heat pump, said device comprising:

a first heat exchanger unit positioned between a first valve and a second valve; a second heat exchanger unit positioned between said first valve and a third valve; a first shell including said first heat exchanger unit and a second shell including said second heat exchanger unit, each of said shells is adapted for defining flow paths for a plurality of heat transfer media, in which each of the flow paths transits through one of said heat exchanger units via a means including said first valve and one of said second valve and said third valve.

In accordance with the present disclosure, each of said first valve, said second valve and said third valve comprises a flap for changing the valve position during changeover of the operation cycle. The flap of said valves can comprise an automated drive mechanism for changing the valve position. The first valve can be a four-port 2 position valve and said second valve and said third valve can be three-port two position valves.

In accordance with the present disclosure, each of said heat exchanger units has an arrangement that can be vertical, horizontal, inclined, L-shaped or Horse-shoe shaped. Both of said first heat exchanger unit and said second heat exchanger unit either comprise a refrigerating alloy or a regenerating alloy.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

The device for cyclic switching of heat transfer media in a metal hydride heat pump of the present disclosure will now be described with the help of the accompanying drawing, in which:

FIGURE 1 illustrates a schematic of the front view of a preferred embodiment of the device for cyclic switching of heat transfer media of the present disclosure;

FIGURE 2 illustrates a side view of the preferred embodiment shown in the FIG. 1 ;

FIGURE 3 illustrates a top view of the device for cyclic switching of heat transfer media of FIGS. 1 & 2;

FIGURE 4 illustrates a schematic of the front view of another preferred embodiment of the device for cyclic switching of heat transfer media of the present disclosure; and FIGURE 5 illustrates the different shapes in which the heat exchanger units of the present disclosure can be formed. DETAILED DESCRIPTION

A device for cyclic switching of heat transfer media of the present disclosure will now be described with reference to the embodiments which do not limit the scope and ambit of the disclosure.

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The present disclosure envisages a device for cyclic switching of heat transfer media in metal hydride heat pumps. The device comprises integral air valves having multiple ports arranged between the heat exchanger units. The multi-port air valves reduce the number of moving parts in a heat pump. The said arrangement, thus, results in reduced thermal inertia. Also, the mass of the heat pump is reduced by using the multi-port air valves, resulting in reduced inertia and higher performance. Further, the device has minimal ducting which reduces the ducting thermal inertia, thereby improving the assembly performance.

Further, the arrangement of the present disclosure has fewer bends and a reduced flow length for the heat transfer media, which decreases the pressure drop in the heat transfer media across its flow path in the device. The decreased pressure drop reduces the energy consumption involved in running air fans and blowers. The arrangement provides uniform air distribution over the heat exchanger units, as dampers and ducting are absent. The absence of dampers and ducting also reduces the size, weight and height of the metal hydride heat pump, and assists in reducing the drag forces on the vehicle in dynamic applications. A metal hydrie heat pump may use one or more sets of paired refrigerating and regenerating alloy containg heat exchanger units to give continuous cooling as each pair provides an output only during half cycle. The paired heat exchanger units are arranged so as to make the heat pump compact. FIGURES 1 & 2 of the accompanying drawing illustrate a schematic of the preferred embodiment of the device for cyclic switching of heat transfer media in a metal hydride heat pump of the present disclosure; the preferred embodiment is generally referenced by the numeral 100 in the FIGS. 1 & 2. FIG. 1 shows the front-view and FIG. 2 shows the side-view of the device 100. The device 100 comprises a first heat exchanger unit 102 and a second heat exchanger unit 104. The heat exchanger units 102 & 104 are placed in a vertical position. A first valve 106 and a second valve 108 are positioned between the heat exchanger units 102 & 104. In the device 100, the first valve 106 and the second valve 108 are placed one above the other with a plenum defined therebetween. The valves 106 & 108 are separated by means of a partition 118 such that each valve defines an independent plenum for connecting an internal duct. An internal duct 114 is connected to the plenum defined by the first valve 106 and an internal duct 116 is connected to the plenum defined by the second valve 108. The internal ducts 114 & 116 are an integral part of the device 100, placed within the shell 110. The internal ducts 114 & 116 are typically circular or elliptical in shape. Each of the valves 106 & 108 comprises a flap 112. The flap 112 is adapted to change the position of the valves 106 & 108 during cycle changeover. The flap 112 comprises an automated drive mechanism for effecting the change in the position of the valve. In the device 100, the valves 106 & 108 are four-port two-position valves. The heat exchanger units 102 & 104 and the valves 106 & 108 are contained inside a shell 110. The shell 110 is adapted for defining flow paths of the heat transfer media in the device 100, where each of the flow paths transits through one of the heat exchanger units 102 & 104, via one of the valves 106 & 108 and one of the internal ducts 114 & 116. Both the heat exchanger units 102 & 104 in the device 100 comprise the same type of hydrogen storing alloy. The device 100 particularly shows air flow pattern for heat exchanger units containing a refrigerating alloy. The heat exchanger units containing a regenerating alloy may also be implemented similarly.

A first half cycle of the device 100 is illustrated in the FIG. 1. The cycle involves two flow paths. A first flow path includes a return air stream which is received at point A at the bottom of the second valve 108. The return air stream traverses through the second heat exchanger unit 104 and is directed towards the outlet (at point B) via the internal duct 114 as a cold air stream. A second flow path includes an incoming ambient air stream which is received at point C of the internal duct 116. The ambient air stream traverses through the first heat exchanger unit 102 and is discharged at point D at the top of the first valve 106 as outgoing ambient air stream. The position of the valves is changed in the second half cycle. The inlet and outlet of the streams can be interchanged depending upon the application requirements. FIG. 3 illustrates a top view of a metal hydride heat pump using the device for cyclic switching of heat transfer media of the present disclosure; the metal hydride heat pump is generally referenced in FIG. 3 by the numeral 200. A device 202 for cyclic switching of heat transfer media including heat exchanger units 204 containing a refrigerating alloy is connected to a device 206 for cyclic switching of heat transfer media including heat exchanger units 208 containing a regenerating alloy by means of flexible hydrogen tubing 210 to form the metal hydride heat pump 200. The arrangement of the multi-port air valves in the devices 202 & 206 is indicated by the numeral 212. An alternative embodiment of the device for cyclic switching of heat transfer media (in a metal hydride heat pump) of the present disclosure is illustrated in FIG. 4 and is generally referenced by the numeral 300 in FIG. 4. The device 300 comprises a first heat exchanger unit 302 and a second heat exchanger unit 304. The first heat exchanger unit 302 is placed between a first valve 306 and a second valve 308. The second heat exchanger unit 304 is placed between the first valve 306 and a third valve 310. The first valve 306 is a four-port two position valve and the second and third valves 308 & 310 are three-port two position valves. Each of the valves (306, 308 & 310) comprises a flap 320. The flap 320 is adapted to change the position of the valves during cycle changeover. The flap 320 comprises an automated drive mechanism for effecting the change in the position of the valve.

The first heat exchanger unit 302 is positioned inside a first shell 312 and the second heat exchanger unit 304 is positioned inside a second shell 314. The shells (312 & 314) are adapted to define flow paths for the heat transfer media. Each of the flow paths transits through one of the heat exchanger units (302 & 304) via the first valve 306 and one of the second valve 308 and the third valve 310. Both the heat exchanger units 302 & 304 in the device 300 comprise the same type of metal hydride alloy. The device 300 particularly shows air flow pattern for heat exchanger units containing a refrigerating alloy. The heat exchanger units containing a regenerating alloy may also be implemented similarly.

A first half cycle of the device 300 is illustrated in the FIG. 4. The cycle involves two flow paths. A first flow path is indicated by the arrow 316 and a second flow path is indicated by the arrow 318. A first heat transfer medium, typically return air or ambient air, is received in the shell 312 of the first heat exchanger unit 302 via the second valve 308. The first heat transfer medium is discharged from the shell 312 via the first valve 306. A second heat transfer medium, typically return air or ambient air, is received in the shell 314 of the second heat exchanger unit 304 via the first valve 306. The second heat transfer medium is discharged from the shell 314 via the third valve 310. The position of the valves is changed in the second half cycle (as indicated by the dotted line). In the second half cycle, the first heat transfer medium will pass through the second heat exchanger unit 304 and the second heat transfer medium will pass through the first heat exchanger unit 302. The inlet and outlet of the streams can be interchanged depending upon the application requirements. The arrangement of each of the heat exchanger units in the device (100 & 300) may be vertical, horizontal, inclined, L-shaped or horse-shoe shaped. The various possible structures of the arrangement of each of the heat exchanger units of the present disclosure are illustrated in the FIG. 5 of the accompanying drawings, where, FIG. 5(A) shows the vertical arrangement, FIG. 5(B) shows the horizontal arrangement, FIG. 5(C) shows the inclined arrangement, FIG. 5(D) shows the L-shaped arrangement, and FIG. 5 (E) shows the horse-shoe shaped arrangement.

TECHNICAL ADVANCEMENT

The device for cyclic switching of heat transfer media in metal hydride heat pumps, as described in the present disclosure, has several technical advantages including, but not limited to, the realization of:

- the device for cyclic switching of heat transfer media reduces the thermal inertia and enhances the performance;

- the device for cyclic switching of heat transfer media reduces pressure drop in the heat transfer media while flowing through the heat pump, thereby reducing the power consumption in running fans and blowers;

- the device for cyclic switching of heat transfer media gives uniform air distribution in the reactor; and

- the device for cyclic switching of heat transfer media is compact, has a reduced weight, and a reduced height which decreases the drag forces on the vehicle.

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.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.