Thermal Capacitor

Abstract

An insulated vessel containing phase change material (PCM), with an elongated conduit through the PCM, the conduit having an inlet and outlet extending outside of the insulated vessel. The PCM absorbs and stores thermal energy originating from a heat source external to the insulated vessel. Operation fluid flowing through the conduit absorbs stored thermal energy from the PCM and can be utilized on demand. A second conduit may be provided to introduce thermal energy to charge the PCM.

Claims

1. A thermal storage device comprising: a vessel surrounding an interior cavity; phase change material within the interior cavity; and a first elongated conduit with an entry end and an outlet end, the first elongated conduit extending through the phase change material, the first elongated conduit capable of allowing the passage of operation fluid therethrough, where the entry end and outlet end extend outside of the vessel.

2. The thermal storage device of claim 1, further comprising: a second elongated conduit with an input end and an output end, the second elongated conduit extending around the phase change material, the second elongated conduit capable of allowing the passage of charging fluid there through, where the input end and output end extend outside of the vessel, where the second elongated conduit is located adjacent to the first elongated conduit within the vessel.

3. The thermal storage device of claim 1, where the first elongated conduit comprises an elongated tube with a first internal diameter.

4. The thermal storage device of claim 3, where the first elongated conduit further comprises: an elongated cylinder with a second internal diameter, where the second internal diameter is at least twice the first internal diameter of the elongated tube.

5. The thermal storage device of claim 4, further comprising: a second elongated conduit with an input end and an output end, the second elongated conduit extending around the phase change material, the second elongated conduit capable of allowing the passage of charging fluid there through, where the input end and output end extend outside of the vessel, where the second elongated conduit is arranged to be coiled around the elongated cylinder.

6. A thermal storage device comprising: a vessel surrounding an interior cavity; phase change material within the interior cavity; and a first elongated conduit with an entry end and an outlet end, the first elongated conduit comprised of an elongated tube with a first internal diameter and an elongated cylinder with a second internal diameter, where the elongated tube and elongated cylinder are located within the interior cavity and surrounded by the phase change material, the first elongated conduit capable of allowing the passage of operation fluid therethrough, where the entry end and outlet end extend outside of the vessel; and a second elongated conduit with an input end and an output end, the second elongated conduit extending around the phase change material, the second elongated conduit capable of allowing the passage of charging fluid there through, where the input end and output end extend outside of the vessel, where the second elongated conduit is located adjacent to the elongated cylinder within the vessel.

7. The thermal storage device of claim 6, the first elongated conduit further comprising: a plurality of elongated cylinders connected in series.

8. The thermal storage device of claim 6, where a portion of the second elongated conduit is coiled around the elongated cylinder.

9. The thermal storage device of claim 1, the first elongated conduit further comprising: a first distribution manifold near the entry end of the first elongated conduit; a second distribution manifold near the outlet end of the first elongated conduit; and a plurality of elongated tubes extending from the first distribution manifold through the interior cavity to the second distribution manifold.

10. The thermal storage device of claim 1, the second elongated conduit further comprising: a third distribution manifold near the input end of the second elongated conduit; a fourth distribution manifold near the output end of the second elongated conduit; and a plurality of elongated tubes extending from the third distribution manifold through the interior cavity to the fourth distribution manifold.

11. The thermal storage device of claim 1, where the phase change material converts from a liquid to a solid at a temperature between 100 and 150 degrees Fahrenheit.

12. The thermal storage device of claim 1, where the phase change material converts from a liquid to a solid at a temperature between 100 and 1200 degrees Fahrenheit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a perspective view of a preferred embodiment of the invention

[0010] FIG. 2 is a side view of preferred embodiment showing cross sectional views along lines A-A and B-B of FIG. 3 and FIG. 4

[0011] FIG. 3 is a cross sectional view along line A-A of FIG. 2.

[0012] FIG. 4 is a cross sectional view along line B-B of FIG. 2.

[0013] FIG. 5 is a perspective view of the heat exchanger assembly of the preferred embodiment of the invention.

[0014] FIG. 6 is a perspective view of the portion of the heat exchanger assembly in the preferred embodiment of the invention which contains charging fluid.

[0015] FIG. 7 is a perspective view of the portion of the heat exchanger assembly in the preferred embodiment of the invention which contains operation fluid.

[0016] FIGS. 8-10 are alternate configurations of the operation fluid containers for the heat exchanger assembly.

[0017] FIGS. 11-13 are top views of the alternate configurations of the operation fluid containers shown in FIGS. 8-10.

[0018] FIG. 14 is a side view of an alternate embodiment of the present invention.

[0019] FIG. 15 is a bottom view of an alternate embodiment of the present invention.

[0020] FIG. 16 is a perspective view of the heat exchanger assembly of an alternate embodiment of the present invention.

[0021] FIG. 17 is a side view an alternate embodiment of the present invention showing cross sectional view along line E-E.

[0022] FIG. 18 is a cross sectional view along line E-E of FIG. 17.

[0023] FIG. 19 is a front view of an alternate embodiment of the present invention showing cross sectional view along line F-F.

[0024] FIG. 20 is a cross sectional view along line F-F of FIG. 19.

[0025] FIG. 21 is a perspective view of an alternate embodiment of the present invention.

[0026] FIG. 22 is a perspective view of the heat exchanger assembly of an alternative embodiment of the present invention.

[0027] FIG. 23 is a detailed view of detail A-A of FIG. 22.

[0028] FIG. 24 is a flow diagram of the operation of the present invention.

[0029] FIG. 25 is a flow diagram of the operation of an alternate embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0030] FIG. 1 shows the preferred embodiment of the invention, with a dual fluid heat exchanger system contained within vessel 500. Entry ports 101 and 301 and outlet ports 102 and 302 are shown extending out of vessel 500. The location of the entry and outlet ports can be anywhere on vessel 500.

[0031] As shown in FIGS. 2, 3 and 4, vessel 500 comprises a thermal insulating layer 501 surrounding an interior cavity wall 502. Insulation layer 501 can be a variety of different standard types of thermal insulation such as spray foam, fiber glass, vacuum and other similar materials known in the art. Interior cavity wall 502 provides a sealed barrier for cavity 400 within vessel 500. The cross sectional view in FIG. 3 shows a dual fluid heat exchanger assembly symmetrically centered within cavity 400. The dual fluid heat exchanger assembly is comprised of charging circuit 300 which contains charging fluid and operation circuit 100 which contains operation fluid. Charging circuit 300 extends from entry port 301 to outlet port 302. Operation circuit 100 extends from entry port 101 to outlet port 102.

[0032] All free space within interior cavity wall 502 and surrounding the heat exchanger assembly is preferably filled with PCM 200. PCM 200 may be any of the known types of phase charged materials, where the type of PCM will be determined by the preferred operating temperature. For household hot water use, the latent temperature of PCM 200 would preferably be in the range of 100 to 150 degrees Fahrenheit, similar to the range of a conventional hot water heater. For other uses, the latent temperature of PCM 200 may be in anywhere between 80 and 950 degrees Fahrenheit.

[0033] FIGS. 5-7 give more detailed views of the dual fluid heat exchanging assembly. FIG. 5 is a perspective view of the operation fluid circuit 100 intertwined with charging fluid circuit 300. All dual fluid heat exchanger components are spaced such that the maximum amount of conduit surface area is in direct contact with PCM 200 inside of cavity 400, optimizing thermal energy exchange within vessel 500. All heat exchanging components are preferably comprised of materials with a high thermal conductivity to best facilitate the exchange of thermal energy from charging fluid contained within charging circuit 300 to PCM 200, and from charged PCM 200 to operation circuit 100, and operation fluid contained therein.

[0034] FIG. 6 gives a perspective view of the charging fluid circuit 300 alone. As shown in FIG. 6, charging fluid circuit 300 is comprised of two concentric coils of heat exchange conduit, with an outer heat exchange coil 305 and an inner heat exchange coil 306, connected together via conduit 303. It is preferred that charging fluid enters heat exchange conduit 300 at entry port 301 and first flows through the inner heat exchange coil 306. This allows for optimal heat retention in the system, as the PCM is preferably heated from the center of the system outward. Charging fluid flows from the inner coil 306 though connector conduit 303, into the outer coil 305. The charging fluid flows through outer heat exchange coil 305, finally exiting the outlet port 302. While the preferred embodiment of charging circuit 300 is the arrangement shown in the drawings, other layouts may be used, including vertical loops or zig zag configured conduits.

[0035] Entry port 301 is an inlet for heated charging fluid to enter vessel 500, where the heated charging fluid provides thermal energy to the PCM within vessel 500. Outlet port 302 is in fluid communication within vessel 500 to entry port 301, and allows for cooled charging fluid to exit the vessel. Outlet port 302 is in fluid communication to an external heating source, such as a solar panel, furnace or hot water heater. In a preferred embodiment, the charging fluid path is cyclic, where the charging fluid starts at the external heating source, enters the charging fluid circuit 300 via entry port 301, exchanges its thermal energy into the PCM, and then exits the vessel via outlet port 302 to return to the external heating source for reheating.

[0036] Charging fluid circuit 300 is preferably formed by an inner coil 306 and outer coil 305 which carry the charging fluid. These coils may be a standard copper tubing which is mechanically coiled into an optimally spaced helix, such that all of the coils' surface area is in contact with PCM. The inner coil 306 is positioned concentrically inside of the outer coil 305 and connected by connector conduit 303 which crosses over at the bottom or top of the dual fluid heat exchanger assembly. The coils are made such that the tubes are separated at an optimal distance for dissipating heat evenly all around into the PCM. The heated charging fluid first travels through the inner coil 306 then through the outer coil 305, heating the PCM from the center of the vessel 500 outward, allowing for the highest temperatures to be in the center region of the vessel 500.

[0037] FIG. 7 presents a side perspective view of the operation fluid circuit 100. The operation fluid circuit 100 preferably comprises a plurality of piping 103, connecting tubular operational fluid containers 104 with ports at either end, which ports can function as either an inlet or outlet for operation fluid to flow through. The operational fluid containers 104 are preferably constructed of material with high thermal conductivity to maximize the exchange of thermal energy between the PCM and the operation fluid. Aluminum is a preferred material for the operation fluid container 104 due to its thermal conductivity, low cost, and availability in many different diameters. As one anticipated use of the invention is the heating of water for household use as the operating fluid, the tubular containers 104 are preferably gas and liquid impermeable, to prevent contamination. Tubular containers 104 preferably have a wider internal diameter than other elements of operation fluid circuit 100, to slow the flow of operation fluid through operation fluid circuit 100, and allow for greater exposure to the PCM for temperature control. The internal diameter of tubular containers 104 is at least twice the internal diameter of the piping 103.

[0038] Entry port 101 is an inlet for the introduction of operation fluid to be heated by the invention. Outlet port 102 in fluid connection with entry port 101, said fluid connection within vessel 500. Outlet port 102 allows for the heated operation fluid to exit the vessel. The heated fluid exiting from outlet port 102 is capable of any number of uses, such as appliances, showers, or other uses. The two fluids (charging fluid and operation fluid) flow through two separate paths within the heat exchanger assembly, and do not mix with each other. The locations of entry ports 101 and 301, and outlet ports 102 and 302 may be in other locations relative to the vessel 500 than as shown in the figures, and one or both of the pairs of entry and outlet ports may be reversed.

[0039] As shown in FIGS. 3-7, operation fluid containers 100 are arranged in a configuration to maximize the space of a cylindrical interior cavity 502, but other configurations and sizes may also employed, including a single operation fluid container 104, surrounded by a charging conduit 300. FIGS. 8-13 show different configurations of the operation fluid containers 104. In a preferred embodiment, the operation fluid containers 104 are connected in series, where operation fluid enters at one end of an operation fluid container 104, filling the entire container, exiting the other end of the operation fluid container 104, and travels through connector 103 to enter the next operation fluid container 104. The operation fluid preferably repeats this process and travels through a number of operation fluid containers 104 before exiting the invention via outlet port 102 connected to a final operation fluid container 104 located in the center of the vessel, at a desired temperature. The outlet port 102 is connected to the last operation fluid container 104 preferably in the center of the vessel 500, where as stated earlier temperatures will be the highest.

[0040] The inventive concept here is that a relatively cold operation fluid enters through entry port 101, and travels through the operation fluid circuit 100, consecutively flowing through each operation fluid container 104 before exiting though the last operation fluid container 104 via outlet port 102. The operation fluid exiting outlet port 102 will preferably have been heated by the charged PCM 200 surrounding the operation fluid containers 104, to reach a desired temperature, greater than the temperature of the operation fluid at entry port 101. The PCM 200 surrounding the operation fluid containers 104 is charged by charging fluid traveling though the heat exchanging circuit 300. Arriving at entry port 301 from an external heat source, heated charging fluid first travels down through the inner coil, and continues up through the outer coil via connection tube 303 at the bottom of the vessel. The heat exchanging circuit 300 carries thermal energy from an external heat source, and quickly disperse that energy to the PCM 200 by conduction.

[0041] The cylindrical shape of vessel 500 is preferred because it facilitates maximal contact surface area between the heat exchanging assembly and PCM material. The cylindrical shape also provides good manufacturing capability. Structures with angular cross-sections, such as rectangular or triangular cross-sections have corners which may create cold spots for the PCM 200 because of lack of contact area, or require additional thermal contact points.

[0042] FIGS. 14-23 show alternate embodiments of the invention. Specifically, FIGS. 14-16 show one style of a single fluid heat exchanger assembly 600 similarly immersed in PCM, contained within an impermeable barrier wall 502. This embodiment operates as a thermal capacitor, which only allows one fluid to enter and exit. The single fluid heat exchanger 600 serves to charge the PCM 200 with thermal energy in a first cycle, and at a second cycle then extracts the thermal energy at a different time, usually upon demand. In the charging mode, the incoming fluid would be heated from an external heating source and flow into the vessel via entry port 601. In this mode the thermal energy from the incoming fluid would be stored by the PCM 200, as fluid travels through assembly 600, eventually exiting outlet port 602. Otherwise the vessel would be heating or maintaining temperature of the same fluid used within the larger system.

[0043] FIGS. 15 and 16 detail the single fluid heat exchanger concept with an arbitrary number of tubes. The ideal fluid flow direction for this type of exchanger is entering the vessel from the outer most tube via entry port 601, filling each subsequent tube until exiting though the center tube via outlet port 602. This way thermal energy is preserved the longest during a cycle which the system needs to draw energy from the vessel. The tubes may be held in place by an alignment plate 604 which has holes punched in it such that the tubes spiral inward to a centered exit tube. These are shown connected via fittings 603, which may be conventional fittings as are known in the art for connecting tubes. Analogous to the dual fluid type heat exchanger system discussed earlier, the heat exchange conduit is spaced such that all of its surface area is in contact with PCM 200.

[0044] FIGS. 17 and 18 detail an alternate embodiment of the single fluid heat exchanger concept. Instead of the fluid flowing though consecutive tubes in series, spiraling from the outer most tube to the inner most tube, in the alternate embodiment, fluid enters a collection manifold 605 and fills all of the tubes 650 simultaneously or in parallel. The tubes 650 are immersed in PCM 200 within cavity 640 and contained within a barrier wall 502. The fluid flow may be bidirectional so outlet ports and inlet ports are interchangeable. This type of heat exchanger system would be better suited for high flow applications where fluid needs to pass through the system very quickly. Not shown in FIGS. 17 and 18, is an insulation layer which would preferably surround barrier wall 502 and collection manifolds 605.

[0045] FIGS. 19-23 show an alternate embodiment of a square shaped cross flow type heat exchanger system, with the heat exchanger assembly within cavity 840, encased in an insulation layer 900, and where cavity 840 is filled with PCM 200. In this embodiment there are four collection manifolds 901, each serving as either an entry or outlet port. Analogous to the preferred embodiment in FIG. 1, cool operation fluid enters via entry port 701, travels through operation fluid conduit 700 collecting thermal energy from surrounding charged PCM 200, and heated operation fluid exits outlet port 702. Heated charging fluid enters entry port 801, travels through charging fluid conduit 800 heating the surrounding PCM, and cooled charging fluid exits outlet port 802. All entry and outlet ports are bidirectional, and can be reversed.

[0046] FIGS. 22 and 23 show a perspective view of the operation fluid conduit 700 and charging fluid conduit 800 within the square embodiment. Here it can be seen that the operation fluid heat exchanging conduit 700 and charging fluid conduit 800 are evenly spaced and overlapping, with operation fluid conduit 700 preferably sandwiched in the center. In this collector manifold type design, fluid will fill all tubes simultaneously for both 700 and 800 with operation fluid and charging fluid respectively. It is important to note that for this type of heat exchanger, there are several different types of conduits which could be implemented aside from a tube shape. Any other types of conduit common in the radiator industry could be used such as bar-and-plate or wafer/fin. Equally important to note is that FIGS. 19-23 only display a dual fluid type exchanger, a more simplified version is easily imaginable with one entry port and one outlet port for operation with a single fluid.

[0047] FIG. 24 presents an example of a complete circuit using the invention, which may be directly applied to hot water heating. The system could be thermostatically controlled by any widely available HVAC controller C1. Charge mode would be initiated by the controller C1 based on readings from the various temperature sensors T1, T2, and T3 within the system. When in charge mode, the charging fluid is heated by any heat source H1 and flows via pump P1 to charge the PCM within vessel 500 to a desired latent heat temperature. Operation fluid, in this case household hot water, would enter through entry port 101 and travel through the operation fluid containers 100 within vessel 500 to be heated, then exit via outlet port 102 to be utilized. Some common plumbing safety devices not shown in this diagram would be required such as, an expansion tank and safety shutdown switch. The expansion take would allow for safe expansion and contraction of the charging fluid, while the shutdown switch would protect the PCM from being over heated by the heat source.

[0048] FIG. 25 presents an example of general system diagram of the single fluid vessel embodiment shown in FIGS. 14-16. Taking an internal combustion engine as the cyclic heat source example H1, the melting temperature of the PCM chosen would match desired engine operating temperature. The secondary heat exchanging system H2 would be the vehicle's heater core (for cab heating/hot air). The three way valve V1 in this example would be optional, and the vessel could be plumbed directly to the heater core H2. When the engine is warm and operating normally, it would have the PCM in charge mode filling it with thermal energy. When the engine is turned off, there is no fluid flow and the energy is stored inside the insulated vessel 502. Upon restarting the engine, hot fluid would travel from the vessel 502 though the heater core H2 and into the engine. This means that the vessel would act as both an engine block heating device to combat cold starting emissions, and a luxury item providing cabin heat almost instantly at cold start-up.

[0049] In contrast to the three layer encapsulation method of having an outer most containment barrier concentric with an inner containment barrier with the empty space in-between the two filled with some insulation material, a single layer method of encapsulation is possible. Very similar to how beverage carriers are constructed, injection molded single layer encapsulation of the PCM and heat exchanger assembly is efficient. This type of encapsulation would make for a more efficient and cost effective volume production, greatly cutting down on material cost as well as labor time involved with assembly. Aside from injection molding techniques, this single layer design could also be formed stainless steel with a vacuum insulation layer. Although stainless steel is a more expensive material, it could provide a more efficient insulation layer, while also enabling the ability for the heat exchanging system and PCM to operate at much higher temperatures.

[0050] This disclosure takes into consideration common building materials which are commercially available. All internal heat exchanging components are preferably comprised of materials which have a high thermal conductivity. An example of such materials are aluminum and copper. The vessel which contains the PCM and heat exchanger assembly, should be made from nonporous materials with low thermal conductivity. Commonly available would be polymer plastics such as polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC). To maximize efficiency of the storage system, the containment vessel should also be insulated from its surroundings. To achieve this, the preferred embodiment utilizes an outer vessel to retain an insulation layer surrounding the PCM and heat exchanger assembly. This insulation layer can be made from a number of different media including vacuum, air, spray foam, hard foam, or fiberglass.

[0051] The capabilities of the storage system described in this disclosure are limited by the working temperature of the vessel which contains the PCM and heat exchanger assembly, and to a lesser extent the working temperature of the heat exchanger materials themselves. For instance, PVC and CPVC have a maximum operating temperature of 200 F. Common soldered joints of copper tubing will melt at 370 F., acting as another limit of the system. The designs presented in this disclosure could be made from any engineered materials. The highest latent heat temperatures of tested PCMs reach 900-1200 F. The heat exchanger and containment materials could be designed to withstand this temperature range.

[0052] While certain novel features of the present invention have been shown and described, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing from the spirit of the invention.