Heat transfer system

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of the storage tank is substantially equal or higher than

EEAT TRANSFER SYSTE", the temperature of the solar collector. The heat transfer BACKGROUND OF THE INVENTION link acts as a heat check valve to allow the heat from the heat source to flow into the heat sink but prevents the

As the resources of combustible fuels to supply en 5 reverse flow of heat from the heat sink back into the ergy for heating, cooling and electricity are becoming heat source. Various combinations of these heat transfer more depleted, considerable interest has been generated links can be used to provide a multiple storage tank in the use of solar energy to satisfy these requirements. system with the capability of storing heat at different The ability of a solar powered system to effectively temperatures without the use of temperature sensors, utilize solar energy in a reliable and economical manner 10 mechanical valves or control systems. depends in large part on (l) its ability to efficiently store A similar heat transfer link can be used to provide a large quantities of heat during the limited number of heat recovery system from the heat storage tanks. By hours of available sunlight in order to operate the sys using various combinations of these heat transfer links, tem during the time in which sunlight is not available; a heat recovery system for recovering heat from multi and (2) its ability to efficiently store heat at the highest 15 ple heat storage tanks at different temperatures can be possible temperature over a relatively wide range of provided without the use of temperature sensors, me collection temperatures during the available hours of chanical valves or control systems.

sunlight. The heat transfer link of the invention is adapted to Because water has proved to be one of the most eco transfer heat from a source of heat to a heat sink while nomical storage mediums available from the present 20 substantially preventing the transfer of heat from the state of the art, most prior art solar energy storage sys heat sink back to the source of heat. The heat transfer tems use water as the storage medium. Since the amount link includes a first heat exchange means carrying a of heat that can be stored in a fixed quantity of water is working fluid with a prescribed vaporization tempera directly proportional to its temperature, it is desirable to ture and pressure range where the first heat exchange have the water at the highest temperature possible in 25 means is located at a first elevation and places the work order to keep the quantity of water required for storage ing fluid therein in a heat exchange relationship with the at a minimum. On the other hand, because a single hot heat output of the source of heat to vaporize the work water storage tank can absorb heat only when the tem ing fluid. The heat transfer link also includes a second perature from the solar collector is higher than the heat exchange means located at a second elevation temperature of the water in the storage tank and be 30 higher than the first elevation and connected to the first cause the available temperature at the solar collector heat exchange means for receiving the vaporized work varies significantly over the normal hours of available ing fluid from the first heat exchange means and return sunlight, it is desirable to use multiple storage tanks ing condensed working fluid to the first heat exchange which permit shifting the heat storage to another tank means under the force of gravity. The second heat ex when one of the tanks will not absorb any more heat 35 change means places the vaporized working fluid in a from the solar collector. heat exchange relationship with the heat sink so that the Multiple water storage tank systems have been pro heat sink will absorb the heat from the vaporized work posed where the solar collector is connected to the ing fluid to condense it as long as the temperature of the appropriate storage tank through temperature con heat sink is below the temperature of the source of heat. trolled mechanical valves. These systems require that As the vaporized working fluid condenses, the con both the temperature of the heat output from the solar densed working fluid flows back to the first heat ex collector and the temperatures of the water in the tanks changer means under the force of gravity to be re-vapo be sensed, and that an appropriate control system be rized.

provided so that the mechanical valves can be se For a heat storage system, the source of heat may be quenced to transfer the solar collector heat output from 45 the heat output of the solar collector and the heat sink one storage tank as its temperature approaches that of may be a plurality of storage tanks, usually filled with the output from the solar collector to another storage water. For a heat recovery system, the source of heat is tank which will accept the heat output. This has neces usually the plurality of storage tanks, usually filled with sarily required these systems to be complex and thus water, while the heat sink is usually a heating system, a expensive to build and operate. Similar systems have SO heat driven cooling system or some other heat driven been proposed which provide for the recovery of usable system.

heat from these storage tanks, however, such heat re For a heat storage system, if the heated output from covery systems have suffered from the same drawbacks the heat source is serially through multiple heat transfer as the prior art storage systems. links individually connected to multiple heat storage 55 tanks, then the first most upstream tank will be heated

SUMMARY OF THE INVENTION

first followed successively by the downstream tanks. If

These and other problems and disadvantages associ a single heat transfer link is used with series connected ated with the prior art are overcome by the invention output heat exchanges individually associated with mul disclosed herein by providing a heat transfer link that tiple heat storage tanks, substantially the same result can connects the heat output from a heat source such as a be achieved.

solar collector to a heat sink capable of receiving heat For a heat recovery system using multiple heat stor such as a heat storage tank which allows rapid transfer age tanks, if the operating fluid of the heat sink is passed of large quantities of heat from the heat output of the serially through multiple heat transfer links individually Solar collector to the heat storage tank as long as the connected to the storage tanks so that the lowest tem heat output from the solar collector is slightly higher 65 perature tank is the most upstream, then the highest than the temperature of the heat storage tank but sub temperature can be maintained in the operating fluid for stantially prevents the flow of heat from the storage the longest period of time. If a single heat transfer link tank back into the solar collector when the temperature is used with series connected input heat exchangers

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individually associated with multiple heat storage tanks, changer 20 is located at a second elevation E2 higher the heat may be sequentially recovered from the storage than the first elevation and the lower end 22 of the heat tanks starting with either the highest or lowest tempera transfer chamber 24 in output heat exchanger 20 is con ture tank first. nected through transfer pipe 25 to the upper end 17 of These and other features and advantages of the inven 5 the fluid reservoir 16 in input heat exchanger 15. The tion will become more apparent upon consideration of upper end 21 of the heat transfer chamber 24 in output the following specification and accompanying drawings heat exchanger 20 is closed. The fluid chamber 16, the wherein like characters of reference designate corre pipe 25, and the heat transfer chamber 24 define a closed sponding parts throughout the several views and in system and this system is charged with working fluid 18 which: 10 so that pipe 25 and chamber 24 are filled with vaporized BRIEF DESCRIPTION OF THE DRAWINGS working fluid when no heat is being transferred from input heat exchanger 15 to output heat exchanger 20.

FIG. 1 is a schematic drawing illustrating one of the In operation, the fluid chamber 16, the pipe 25 and heat transfer links of the invention; the heat transfer chamber 24 are charged with the FIG. 2 is a saturated pressure-enthalpy curve for a 15 working fluid 18 at a prescribed pressure when the typical refrigerant; temperature of the working fluid is at a known tempera FIG. 3 is a schematic drawing illustrating one en ture. The initial charging pressure is selected to cause bodiment of a heat storage and recovery system of the the working fluid 18 in the input heat exchanger 15 to invention; start boiling to vaporize the liquid working fluid when FIG. 4 is a schematic drawing illustrating another 20 the available temperature from the heat source 11 rises embodiment of a heat storage and recovery system of above a prescribed value to start the operation of the the invention; and, heat transfer link 10.

FIG. 5 is a schematic drawing illustrating still an Assuming initially that the temperature T, of the heat other heat recovery system of the invention. source 11 is the same as the temperature T of the heat These figures and the following detailed description 25 sink 12, the working fluid 18 in a liquid state will partly disclose specific embodiments of the invention, how fill the reservoir 16 in the input heat exchanger 15. The ever, it is to be understood that the inventive concept is rest of reservoir 16, the pipe 25 and the heat transfer not limited thereto since it may be embodied in other chamber 24 will be filled with the working fluid 18 in a forms. vapor state. The temperature T and pressure P of the 30 liquid and vapor of the working fluid 18 will be substan

DETAILED DESCRIPTION OF LLUSTRATIVE tially constant throughout both heat exchangers 15 and EMBODIMENTS 20 and the pipe 25. The temperature T will be equal to Referring to FIG. 1, the heat transfer link 10 is con temperatures T, and T and the vapor phase of working nected between a heat source 11 and a heat sink 12 and fluid 18 will be in equilibrium with the liquid phase is in a heat exchange relationship with both. The heat 35 thereof, Because there are no temperature differences transfer link 10 operates to transfer heat from the heat between the heat source 11 and heat sink 12, no heat source 11 to the heat sink 12 but prevents the transfer of will be transferred and the system will be at a steady heat from the heat sink 12 back to the heat source 11. state. When the output temperature Tof the heat source Thus, the heat transfer link 10 is a one direction heat 11 rises to temperature T. above the temperature T of transfer device as will become more apparent. the heat sink 12, the working fluid 18 in its liquid phase The heat transfer link 10 comprises an input heat will start to boil. This causes the working fluid 18 to exchanger 15 including a fluid reservoir 16 with an absorb heat and increase its enthalpy. Thus, the heat upper end 17. The fluid reservoir 16 is charged with a source 11 is now trying to drive the temperature T of working fluid 18 which has a prescribed vaporization the working fluid 18 toward the higher temperature T. temperature and pressure relationship so that the liquid 45 of the heat source 11 by vaporizing liquid working fluid level of the working fluid has elevation E. While a while the heat sink 12 is trying to drive the temperature number of different working fluids may be used as long T toward the lower temperature T of the heat sink 12 as the working fluid can be vaporized at the minimum by condensing vapor working fluid. This generates a operating temperature of the heat source 11, refriger slight pressure difference in the vapor working fluid 18 ants normally used in air conditioning systems such as 50 between exchanger 15 and exchanger 20 so that a net Refrigerant 12 have been found satisfactory when heat vapor flow is generated between the exchangers 15 and is being received from a solar collector, especially 20 driving the vapor and thus the heat energy toward where the heat source working fluid is water and the exchanger 20. The temperature of the working fluid 18 heat sink working fluid is water. The input heat ex will rise to a higher temperature T" with a correspond changer 15 places the working fluid 18 in a heat ex 55 ing rise in pressure to pressure P," where the liquid and changer relationship with the heat output of the heat vapor phases again reach equilibrium but the pressure source 11 so that the working fluid in reservoir 16 will and temperature will still be virtually constant through be vaporized when the temperature of the heat output out the system.

from the heat source 11 exceeds the vaporization tem The temperature T of the heat sink 12 is now below perature of the working fluid as will become more ap the temperature T of the working fluid vapor in the parent. output heat exchanger 20 so that the latent heat in work The heat transfer link 10 also includes an output heat ing fluid 18 is transferred to the heat sink 12 to decrease exchanger 20 which has an upper end 21 and a lower the enthalpy of the working fluid vapor causing it to end 22. The output heat exchanger 20 defines a heat start to condense to its liquid phase. Because the liquid transfer chamber 24 therein which receives the vapor 65 working fluid 18 in the output heat exchanger 20 is at ized working fluid 18 therein and places this vaporized substantially the same temperature T," as the vaporized working fluid in a heat exchange relationship with the working fluid 18, virtually no heat transfer takes place heat sink 12. The lower end 22 of the output heat ex between the liquid and vapor as the condensed liquid

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working fluid 18 flows back by gravity to the input heat fluid 18 in the output heat exchanger 20, the higher exchanger 15 through pipe 25. As the vapor in the out temperature T in the heat sink 12 can produce no vapor put heat exchanger 20 is condensed, more of the liquid in the working fluid 18 and there will consequently be in the input heat exchanger 15 is vaporized to replace no heat transferred through the working fluid 18 in the the condensed vapor. Thus, it will be seen that heat will reverse direction from the heat sink 12 to the heat be continuously transferred from the output of the heat source 11 except for a small amount of heat flow caused source 11 to the working fluid 18 through the input heat by conduction through pipe 25 and by convection exchanger 15 while heat will be continuously trans through the vapor working fluid 18 in pipe 25. Thus, the ferred from the working fluid 18 to the heat sink 12 heat transfer link 10 effectively transfers heat only from through the output heat exchanger 20 as long as the O the heat source 11 to the heat sink 12 and not in the actual temperature Tof the heat sink 12 remains below reverse direction.

the temperature T, of the output of the heat source 11, FIRST EMBODIMENT OF HEAT STORAGE The heat transfer rate from the heat source 11 to the heat sink 12 through the heat transfer link 10 is, of AND RECOVERY SYSTEM course, proportional to the temperature difference be 5 FIG. 3 illustrates a heat storage and recovery system tween the heat source 11 and heat sink 12 with greater 100 which uses a plurality of heat transfer links to store temperature differences producing greater heat transfer and recover heat at different temperature levels. This rates. Because the latent heat of the working fluid 18 is system is especially adaptable to store heat from a solar used as the heat transfer mechanism, the heat transfer collector SC that acts as the heat source for the storage rate capability of link 10 is several times greater than a 20 loop 101 of the system. The solar collector SC has a heat transfer mechanism that does not use vaporization heated fluid output, usually water, whose heat is trans and condensation. ferred to a plurality of insulated storage tanks ST with Reference to FIG. 2, which is a saturation pressure a storage fluid therein, usually water. These storage enthalpy curve for a typical refrigerant such as Refrig tanks ST act as the heat source in the heat recovery erant 12 (Freon-12, a trademark of DuPont de Nemours 25 loop 102 of the system. The heat in the storage tanks ST Co.), will better explain the pressure and temperature is transferred to a heat driven system HDS such as a relationships of the heat transfer. Because the working heater or heat driven air conditioner to drive the sys fluid 18 changes from its liquid to its vapor phase and tem. While different numbers of storage tanks ST may back to its liquid phase at a substantially constant pres be used, there are illustrated and individually desig sure and temperature under saturation conditions, it will 30 nated ST ST, and ST.

be seen that heat is transferred while the working fluid The system heat input loop 101 includes a separate 18 remains at a substantially constant temperature. For storage heat transfer link 110 transferring heat from the instance, assume that heat is being transferred into the output fluid of the solar collector SC to one of the heat transfer link from the heat source and the equilib storage tanks ST. The heat transfer links are individu rium temperature of the working fluid in the link is 100 35 ally numbered 110, 110, and 110 to correspond to the F. The heat being transferred into and out of the link storage tank into which each transfers heat from the working fluid is represented by the solid line A in FIG. solar collector. Since each of the storage heat transfer 2 extending between point P on the saturated liquid links 110 have the same construction, only link 110 will side of the curve and P, on the saturated vapor side of be described in detail with corresponding reference the curve. Now, suppose the temperature of the heat 40 numbers being applied to links 110, and 110. Source imposed on the heat transfer link is increased. The input heat exchanger 115 of link 110, is a shell This raises the equilibrium temperature of the working and tube type heat exchanger where the working fluid fluid in the link to 140 F. as an example. The heat being 118 of the link is carried in the shell chamber 116, while transferred into and out of the link working fluid is now the heated fluid output from the solar collector SC represented by dashed line B extending between point 45 passes through the tubes 113 of exchanger 115 to heat Pl' on the saturated liquid side of the curve and point the working fluid 1181. The output heat exchanger 120.1 P, on the saturated vapor side of the curve. As the is a coil vertically oriented and immersed in the storage temperature of the heat source rises, it will be seen that fluid in tank ST. The passage 124 in coil 120 is closed both the pressure and temperature of the working fluid at its upper end 121 while its lower end 122 is con 18 rise, however, the higher pressure and temperature SO nected to the vapor space in the shell of heat exchanger are substantially constant throughout the working fluid 115 through the transfer pipe 125. It will thus be seen 8. that the link 110 will transfer heat from the heated fluid When the temperature T of the heat sink 12 equals output from the solar collector SC passing through tube the temperature T, of the heat source 11 or the tempera 113, to the storage fluid in tank STI in the manner de ture T, of the heat source 11 falls below the temperature 55 scribed for link 10 but will not transfer significant heat Ta of the heat sink 12 as would occur with a solar collec in the reverse direction from the storage fluid in the tor heat source over a period of daily operation, the storage tank to the fluid output from the solar collector. liquid working fluid 18 in the input heat exchanger 15 The level of the liquid working fluid in the shell cham would no longer be vaporized since the pressure of the ber 116 is at the lower elevation E while the lower end vapor working fluid 18 would be equal to or greater 122 of coil 120 is located at the higher elevation Eo so than the equilibrium vapor pressure of the liquid work that the working fluid 118 condensed in coil 120 will ing fluid 18 in the input heat exchanger 15. All the flow back to the shell chamber 116 in exchanger 115 condensed liquid working fluid 18 will now drain back through pipe 125 under the influence of gravity. Nor into the input heat exchanger 15 and not vaporize. mally, the pipe 125 will be insulated. When the temperature T, reduces to a value less than 65 It will be noted that the heated fluid output from the temperature T, some of the vapor working fluid 18 will solar collector SC passes serially through the tubes condense until a new lower equilibrium pressure is 113, 113, and 113 of the heat exchangers 115, 115 and reached. However, since there is now no liquid working 115 of the heat transfer links 110, 110, and 110. Thus,

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the heateu fluid output f, on sular collector SC passes he heat transfer link 110 associated with the upstream through the tube 113 in link 110 first, then through most storage lank ST at a lower temperature than the tube 113 in link 110, and finally through the tube 113 temperature T heat will be transferred through the in link 110 before it is recycled through the solar collec heat transfer link 110 into that storage tank ST until the tor SC for reheating. temperature of the storage fluid in that particular stor The system heat input loop 101 of the system 100 age tank rises to or exceeds the temperature T. Nor operates with the transfe link. a 3-10, each transfer mally the temperature T will be greater than the tem ring heat to its associated storage lank under the theory perature T and the temperature T will be greater than of operation described hereinabove for link 10. Assum the temperature T. If the temperature T, falls below all ing that the storage tank STI is at an initial temperature 10 of the temperatures at the storage tanks, the fluid output T, that the storage tank ST, is at an initial temperature from the solar collector will flow through all of the T, and that the storage tank ST is at an initial tempera input heat exchangers 115 without heat being trans ture T, the system operation will be described where ferred to any of the associated storage tanks ST. When the input temperature T, from the solar collector heat the input temperature T, again rises above any of the source SC is at a higher temperature of any of the tanks 15 temperatures of the storage fluids in the storage tanks, ST. The heated fluid output from the solar collector SC heat will be transferred through the associated link 110 passes first through the tube 113 in the input heat ex into the storage fluid in the most upstream storage tank changer 115 of the first heat transfer link 110 where the whose temperature is below the temperature T. working fluid 118 in the heat transfer link 110 is vapor The heat recovery loop 102 includes a separate re ized thereby absorbing heat and transfering heat from 20 covery heat transfer link 210 connecting each storage the heated fluid output of collector SC to the storage tank with the driving fluid of a heat driven system tank ST. This causes the heated fluid output from the HDS. The recovery heat transfer links 210 are individu solar collector SC to be cooled to a new lower tempera ally numbered 210, 210, and 210 to correspond to the ture T. by the time it passes to the next heat transfer link storage tank each connects to the driving fluid of the 110. If this new temperature T, is higher than the tem 25 heat driven system HDS. Since each of the recovery perature T of the storage tank ST, then heat will also heat transfer links 210 have the same construction, only be transferred through the heat transfer link 110 to cool link 210 will be described in detail with corresponding the heated fluid output from the collar collector SC to a reference numbers being applied to links 210, and 210. still lower temperature T' by the time it passes to the The input heat exchanger 215 of link 210 is a coil third heat transfer link 110. If the temperature T." is 30 vertically oriented and immersed in the storage fluid in higher than the temperature T in the storage tank ST3, tank ST. The working fluid 218 of the link is carried in then additional heat will be transferred into the storage the coil passage 216 which is closed at its lower end tank ST, before the fluid output from the collar collector while its upper end is connected to the output heat SC finally is recycled back through the solar collector exchanger 220 through the transfer pipe 225. The SC to be reheated. The rate of heat transferred into each 35 output heat exchanger 220 is a shell and tube type heat tank ST-ST is, of course, proportional to the tempera exchanger where the vaporized working fluid 218 is ture difference between the temperature of the fluid in received in the shell chamber 224 while the heat driven the tank and the temperature of the fluid output from system driving fluid to be heated passes through the the solar collector while it is passing through the partic tube 221 of the exchanger 220. It will further be noted ular heat transfer link associated with the tank. Thus, it 40 that the upper end of the input heat exchanger 215 is will be seen that the temperature T in the tank ST will located at a first elevation E while the lowermost por be driven toward the output temperature T from the tion of the shell chamber 224 is located at a higher solar collector with the temperatures of each of the elevation E. It will further be noted that the liquid subsequent tanks ST, and ST being at lower tempera level of the working fluid 218 substantially fills the coil tures. As the temperature T of tank ST is driven 45 passage 216 under equilibrium conditions. It will thus toward the temperature T more and more of the heat be seen that the link 210 will transfer heat from the transferred out of the heat source output fluid will shift storage liquid in tank ST to the heat driven system to the next downstream storage tank since the heat driving fluid passing through the tube 221 in the output transferred is proportional to the temperature differ heat exchanger 220 in the manner described for the link ences. If the temperature Treaches the temperature T 50 10 but will not transfer significant heat in the reverse then the fluid output from the solar collector SC will direction from the heat driven system driving fluid pass through link 110 without heat transfer because of passing through heat exchanger 220 to the storage fluid the one way action of link 110 and the heat will be in the storage tank ST. In essence, it will be seen that transferred into the next downstream tank which is at a the links 210 are simply the links 110 turned upside temperature lower than the temperature of the fluid 55 down. Thus, the input heat exchangers 215 will vapor output from the solar collector. ize the working fluids 210 and the shell and tube type Because the available solar heat at any given location heat exchangers 220 will condense the working fluids varies during the hours of daily sunlight, the output 218.

temperature T from the solar collector SC may drop It will further be noted that the driving fluid to be below the temperature T in the storage tank ST while heated passes serially through the heat transfer links the temperature will still remain higher than the temper 210, 210, and 210. Depending on the size of the heat ature T or T in tanks ST or ST. Because of the one exchangers 215, the driving fluid to be heated will tend way action of each of the heat transfer links 110, the to be heated to the highest temperature available from heated fluid output from the solar collector SC will pass the storage tanks ST. If the driving fluid to be heated is through those heat transfer links associated with the 65 passed serially through the recovery heat transfer links storage tanks ST at a temperature higher than the tem 210 as seen in FIG.3 so that the driving fluid passes first perature T, without transferring heat to the particular through the output heat exchanger 220 of the heat storage tank. As soon as this heated fluid output reaches transfer link 210, and assuming that the temperature T

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Siss than the temperature T and the temperature I is ent numbers of storage tanks ST may be used, three are as , '', in the temperature T, then heat will be trans illustrated and individually designated ST, ST2 and ferred from each of the storage tanks ST but the temper ST, ature of all of the tanks ST will be lowered at the same The heat from the heated fluid output of solar collec time. Assuming that the inlet temperature of the driving tor SC is transferred to the storage fluid in the storage fluid is at T. seen in FIG. 3, then the storage heat trans tanks ST by a combination storage heat transfer link 310 fer link 210 will transfer heat from the storage tank whose theory of operation is based on that of link 10. ST into the driving fluid to raise the temperature of the The storage heat transfer link 310 has a single input heat driving fluid to the temperature T by the time it passes exchanger 315 and a plurality of output heat exchangers through the link 210. If the temperature T, in tank ST O 320 serially connected to the input heat exchanger 315. is higher than the temperature T, then additional heat The heat exchanger 315 is a shell and tube type heat will be transferred from the storage tank ST, into the exchanger where the working fluid 318 of the link is driving fluid as it passes through the output heat ex carried in the shell chamber 316 while the heated fluid changer 220 of the link 210. This serves to raise the output from the solar collector SC passes through the temperature of the driving fluid to a still higher temper 5 tube 313 of exchanger 315 to heat the working fluid 318. ature T by the time it passes through the link 210, and, The working fluid liquid level in the shell chamber 316 if the temperature T is higher than the temperature T is at elevation E. Each of the output heat exchangers then the heat transfer link 210 will transfer additional 320 is a coil vertically oriented and immersed in the heat into the driving fluid as it passes through the link storage fluid of one of the storage tanks ST. For sake of 210 to raise its temperature to a higher temperature T. 20 simplicity, the coils have been numbered 320, 320, and This output temperature T of the driving fluid will 320 corresponding to the storage tank number in which approach that of the highest temperature stored or tem they are submerged. Thus, it will be seen that coil 320 perature T. On the other hand, if the flow of the heat defines a passage 324 therein with an upper inlet end driven system driving fluid through the heat transfer 321 and a lower outlet end 322. Likewise, coil 320, has links 210 is reversed so that the driving fluid flows first 25 passage 324, inlet end 321 and outlet end 322; and coil through the heat transfer link 210 associated with the 320 has passage 324, inlet end 321s and outlet and 3223. highest temperature T in the storage tanks ST, and the The upper inlet end 321 of coil 320 is located in tank effective heat transfer surface area of the heat ex ST at an elevation E higher than elevation E, and is changer 215 of the link 210 is sufficiently large, then connected to the vapor space in the shell chamber 316 the driving fluid will be heated to a temperature ap 30 in heat exchanger 315 through the transfer pipe 325. proaching the temperature T before it exits the heat The lower outlet end 322 of coil 320is located at eleva exchanger 215. If the temperature This greater than the tion E which is lower than elevation E but higher temperature T and the temperature T, then the tem than elevation E. The upper inlet end 321 of coil 320, perature of the driving fluid as it exits the link 210 will in tank ST is located at elevation E at least as low as be higher than the temperatures T, and T, so that sub 35 elevation E but higher than elevation E and is con stantially no heat will be transferred from the storage nected to the outlet end 322 of coil 320, through trans tanks ST, and ST until the temperature Tdrops to the fer pipe 326. The lower outlet end 322 of coil 320, is vicinity of the temperature T, or T, whereupon the heat located at elevation E2 lower than elevation E, but transfer links 210, and/or 210 will start to transfer heat higher than elevation E. In like manner, the upper inlet into the driving fluid. If any one of the temperatures T, 40 end 321 of coil 320, in tank ST, is located at elevation T; or T drops below the initial temperature of the heat Eat least as low as elevation E, but higher than eleva driven system driving fluid passing through its associ tion E and is connected to the outlet end 322 of coil ated heat transfer link 210, then no heat will be removed 320, by transfer pipe 328. The lower outlet end 322 of from the associated lower temperature storage tank ST. coil 320 is located at elevation E. lower than elevation The recovery loop 102 is well suited to heat recovery 45 Ebut higher than elevation E and is connected back to where it is desirable to recover heat at the highest possi the shell chamber 316 in input heat exchanger 315 ble temperature for the longest period of time. A num therein through returnpipe 329 and metering valve 330. ber of applications would use this approach such as, for Thus, it will be seen that the vapor working fluid 318 example, where the heat driven system uses an absorp can successively circulate through the coils 320-320, tion refrigeration cycle which requires temperatures 50 while the working fluid 318 condensed in the coils greater than about 180' F. 320-320 drains back to the exchanger 315 through the SECOND EMBODIMENT OF HEAT STORAGE succeeding coils and valve 330. AND RECOVERY SYSTEM Assuming an initial temperature T in tank ST, a temperature T in tank ST and a temperature T in tank

FIG. 4 illustrates another heat storage and recovery 55 ST, a temperature T, in the heated fluid output of solar Systern 300 which uses a modified heat transfer link collector SC higher than temperatures T-T will cause construction to store and recover heat at different tem the liquid working fluid 318 in heat exchanger 315 to perature levels. This system, like system 100, is espe start vaporizing and absorbing heat as the solar collec cially adaptable to store heat from a solar collector SC tor fluid output passes through exchanger 315. This that acts as the heat source for the heat input loop 301 starts vapor working fluid 318 circulating out through of the system. The solar collector SC has a heated fluid pipe 325 and serially through coils 320-320. As soon as output, usually water, whose heat is transferred to a the temperature of the vapor working fluid 318 in coil plurality of insulated storage tanks ST with a storage 320 rises above temperature T, it starts to condense fluid therein, usually water. These storage tanks ST act and drain back to exchanger 315 through coils 320 and as the heat source in the heat recovery loop 302 of the 65 320 and valve 330. While the vapor working fluid 318 System. The heat in the storage tanks ST is transferred may initially condense in all three coils, the valve 330 to a heat driven device HDD such as a heater or heat which is an adjustable flow control valve is adjusted to driven air conditioner to drive the device. While differ control the flow of condensed liquid working fluid 318

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back to exchanger 315 so that the liquid level of the than any of the elevations E E or E and is con working fluid 318 in coils 320-320, will be maintained nected to the inlet 421 of coil 415 through metering at the outlet end of the particular coil 320-320, transfer valve 432 and inlet pipe 434. The inlet 430 has an eleva ring heat into the storage tank associated therewith tion ER higher than elevation E. The output heat across some prescribed temperature difference between exchanger 420 is a coil which defines a passage 435 the working fluid 318 and the storage fluid receiving therethrough with inlet 436 and outlet 438. Outlet 438 heat. Therefore, in this instance, an appropriate adjust has an elevation E higher than the elevation ER of ment of valve 330 will cause the condensed liquid level receiver 429 and is connected to the inlet 430 so that as of fluid 318 to rise to the level of the outlet end 322 of vapor working fluid 418 in loop 302 condenses in coil coil 320 as indicated at point P in FIG. 4 when the O 420, the condensed working fluid flows into the cham system reaches steady state conditions. Because coils ber 429 in receiver 428. The inlet 436 to coil 420 is 320, and 320 are now filled with liquid working fluid located at elevation E, which is higher than elevation 318, the heat transferred to tanks ST and ST will be E and is connected to the outlet 422 of coil 415 small compared to the heat transferred to tank ST. through

When temperature T substantially equals the tempera 15 a duct Dvapor pipe 439. The coil 420 may be located in ture T, or temperature T, drops below temperature T, across coil 420 by fan Fsystem in a heating so that air can be forced to heat the air while coiling coil the vapor working fluid 318 will cease to be condensed 420.

in coil 320 and the level of condensed working fluid 318 The operation of the heat recovery loop 302 can best in coils 320, and 320 will start to lower since this con be described by starting with the working fluid 418 in its densed working fluid continues to drain back to heat 20 liquid phase in the fluid chamber 429 of receiver 428. exchanger 315 through valve 330. The level of the con The metering valve 432 is adjusted so that the liquid densed liquid working fluid 318 lowers to a new posi working fluid 418 is allowed to flow by gravity into the tion P at coil 320, so that coil 320, now condenses the coil 415. If the initial temperature T of the working working fluid 318 to maintain the level of the condensed fluid 418 in receiver 428 is below the temperature T in working fluid until the temperature T, substantially 25 the storage tank ST, then the liquid working fluid 418 equals temperature T or temperature T, drops below will temperature T. The level of condensed working fluid from bethevaporized in coil 415, thereby absorbing heat then lowers to a new position P where the vapor work fluid 418 to flow outThis tank ST.

causes the vaporized working coil 415, through coil 415 and ing fluid 318 is condensed in coil 320. Normally, then, coil 415 and subsequently through the vapor pipe 439 the temperature T will be higher than temperature T 30 to the output heat exchanger coil 420. If the tempera and temperature T will be higher than temperature T. ture T of the air flowing through the duct D is lower It will also be noted that the transition of the condens than the temperature T, then the vaporized working ing of the working fluid 318 from one coil 320 to the fluid 418 will be condensed in the coil 420 and the con next lower temperature coil 320 is a gradual process so densed working fluid will flow back into the receiver that some condensation will probably be occurring in 35 428 under the influence of gravity. It will be noted that two of the coils 320 at the same time during the transi the vaporized working fluid 418 generated in the coil tion period. It is also to be understood that the heat 415 will absorb a small amount of heat to super heat the input loop 301 will work as long as all of the coils vapor as it flows through coil 415, and will do likewise 320-320 are higher than the elevation E. coil 320is no as the vapor working fluid 418 passes through coil 415 higher than coil 320 and coil 320 is no higher than coil since the temperature T, is higher than temperature T 320. and the temperature T is higher than the temperature In the heat recovery loop 302, heat is transferred to T. The quantity of heat absorbed from the storage the driving fluid of the heat driven device HDD from tanks ST, and ST as superheat, however, is small com the storage tanks ST by a combination recovery heat pared to the heat absorbed from the tank ST because transfer link 410 whose theory of operation is also based 45 the on that of link 10. The loop 302 uses the lowest tempera is theheat absorbed by the working fluid 418 in coil 415 latent heat of vaporization.

ture tank first.

The recovery heat transfer link 410 has a plurality of fluid As heat is absorbed from the tank ST by the working input heat exchangers 415, one being associated with to drop 418, the temperature T of the tank ST continues each storage tank ST. These input heat exchangers 415 50 storage fluid until such time as the available heat from the in the tank ST is not capable of vaporizing have been numbered 415, 415 and 415 to correspond all of the liquid entering the coil 415. At this time, the to the numbering of tanks ST, ST, and ST and are coil 415 starts to fill with liquid working fluid 418 until serially connected to each other. The heat exchangers some of this liquid working fluid overflows into the coil 415 are coils with the coil 415, in tank ST having fluid 415, where it vaporizes at the higher temperature T of passage 424 with inlet 421 and outlet 422. The outlet 55 tank ST. The vaporized working fluid continues to 422 is located at elevation E1 which is the highest flow through the coil 415 where it absorbs the small elevation of coil 415. The coil 415 in tank ST has fluid amount passage 424 with inlet 421 and outlet 422, the outlet through of the additional heat as super heat as it passes coil 415. The vapor working fluid 418 422 being located at elevation E, the highest elevation continues to flow to the coil 420 where it is condensed of coil 415, and connected to the inlet 421 of coil 415 and flows by gravity back into the receiver 428. As by transfer pipe 425. The coil 415 in tank ST, has fluid passage 424 with inlet 421 and outlet 422, which is indicated now start above, the temperature in the tank ST will to drop and will reach a point where it can no located at elevation E, the highest elevation of coil longer vaporize all of the available liquid working fluid 415. Outlet 422 of coil 415 is connected to inlet 421 of in the coil 415 Consequently, the liquid working fluid coil 415 by transfer pipe 426. The recovery loop 302 65 also includes a fluid receiver 428 defining a fluid cham 418 into will start filling the coil 415 and start to flow over the coil 415 where the higher temperature T will ber 429 therein with an upper inlet 430 and lower outlet 431. The outlet 431 is located at elevation E higher vaporize the liquid working fluid 418. This process continues until the temperature T in the tank STI falls

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below the vaporizing temperature of the working fluid ther be noted that the lowermost portion of the shell 418. Thus, it will be seen that the working fluid 418 will chamber 528 is located at elevation E, higher than the be vaporized in the first coil 415 it sees which is at a output elevation E of coil 515. The inlet 530 to shell temperature higher than the vaporizing temperature of chamber 528 is located in the lowermost portion of the working fluid 418. The heat recovery loop 302, chamber 528 and connected to the upper end 522 of then, uses the lowest useful temperature first. This type coil 515 by pipe 531.

heat recovery is, in many cases, the most desirable since As mentioned above, the loop 500 recovers heat from it is easier to replace the lowest temperature heat in the tanks ST by the solar collector SC, especially where the the highest temperature available from tanks ST. This type recovery may be desirable in some cases such as in highest available temperature is not required in the coil O the opraation of a device using an absorption refrigera 420 to drive the heat driven system associated there tion with. On the other hand, reversal of the order of the coil F. arecycle where temperatures greater than about 180" required.

415 will cause the heat driving capability of the highest In operation, the coils 515 are charged with working temperature storage tank ST to be depleted first. fluid 518 so that all of the coils 515 are filled to a level THIRD EMBODIMENT OF HEAT RECOVERY such that the liquid working fluid 518 fills at least a SYSTEM large portion of the upper coil 515 when all of the heat FIG. 5 illustrates an alternate embodiment of the heat storage tanks ST are at their maximum operating tem recovery loop and is designated by the numeral 500. peratures. Assuming that the temperature T in tank ST, is higher than the temperature T in the tank ST:

This loop uses a modified heat transfer link construction 20 and to recover heat from storage tanks ST at different ten temperature T is higher than the temperature T in perature levels. The storage tanks ST act as the heat the tank ST, the equilibrium pressure and temperature Source for the system and the heat stored in the storage in the working fluid 518 will be set by the temperature tanks ST is transferred to a heat driven device HDD T in the tank ST. This will cause the liquid working such as a heater or heat driven air conditioner to drive 25 fluid 518 in coil 515 to start being vaporized with heat the device. While different numbers of storage tanks ST being transferred into the vaporized working fluid 518 may be used, three are illustrated and individually des from the tank ST. Because the temperature T in tank ignated ST, ST, and ST. For the sake of clarity, the ST sets the equilibrium pressure and temperature in the temperature T of the tank ST is higher than the tem working fluid 518, the equilibrium temperature and perature of T of the tank ST and the temperature T of 30 pressure will be above that at which the working fluid the tank ST is higher than the temperature T of the 518 in coils 515 and 515, will be vaporized. Assuming tank ST. The heat from the tanks ST is transferred to that the temperature T of the driving fluid passing the driving fluid of the heat driven device HDD from through the tube 529 in the exchanger 520 is lower than the storage tanks ST by a combination recovery heat the temperature T, heat will be transferred to the driv transfer link 510 whose theory of operation is based on ing fluid to heat it while causing the vapor working that of link 10. The loop 500 removes heat from the fluid 518 in the coil 520 to be condensed whereupon it highest temperature tank first. flows back down toward the coil 515 under the influ The recovery heat transfer link 510 has a plurality of ence of gravity for revaporization. The temperature T input heat exchangers 515, one being associated with in the tank ST continues to drop as heat is taken from each storage tank ST. These input heat exchangers have 40 the tank and transferred to the driving fluid until the been numbered 515, 515, and 515, to correspond to the temperature T substantially equals the temperature T number of tanks ST ST, and ST. The heat exchangers in the storage tank ST. At this point, the liquid working 515-515 are serially connected to each other as will fluid 518 in the coil 515 will start being vaporized and become more apparent. The heat exchangers 515 are heat will now be transferred from both tanks ST and coils with the coil 515 in tank ST having fluid passage 45 ST, essentially equally since the evaporation of the 524, with lower end 521 and upper end 522. The upper working fluid 518 will take place all along the coil 515 end 522 is located at elevation E and lower end 521 is and 515. A small temperature and pressure gradient located at elevation E, lower than elevation E. The will be established between the outlet 522 af the coil coil 515, in tank ST, has fluid passage 524 with lower 515 and the inlet 521 of the coil 515 due to the effect end 521, and upper end 522, the upper end 522, being SO of the weight of the column of liquid working fluid 518 located at elevation E2 at least as low as elevation E on the equilibrium pressure of the working fluid. Heat and the lower end 521, being located at elevation E will continue to be transferred from the tank ST and lower than elevation E. The upper end 522, is con ST, until their temperatures substantially equal the tem nected to the lower end 521 of coil 515 by transfer pipe perature T whereupon evaportion will begin in the coil 525. The coil 515, in tank ST, has fluid passage 524, with 55 515, and continue in the coils 515 and 515. Heat will lower end 521 and upper end 522. Upper end 522, is continue to be taken from all of the tanks ST so long as located at elevation E. at least as low as elevation E. the temperatures in the tanks remain above the tempera and lower end 521 is located at elevation E. lower than ture of the driving fluid passing through the tubes 529 in elevation E. Upper end 522 of coil 515 is connected to lower end 521 of coil 515, by transfer pipe 526 and the exchanger 520. The loop 500 will finally stop func tioning when the temperature of the tanks ST reaches lower end 521 is closed. The recovery loop 500 also includes an output heat exchanger 520 through which the temperature of the driving fluid passing into the the driving fluid of the heat driven device HDD passes because529theofequilibrium tubes the exchanger 520. It will be noted that to be heated. Output heat exchanger 520 is a shell and 518 are set by the highestpressures in the working fluid temperature storage tank ST, tube type heat exchanger where the vaporized working 65 the loop 500 will operate to always transfer heat from fluid 518 is received in the shell chamber 528 while the the highest temperature storage tank first, the next high heat driven System driving fluid to be heated passes est temperature storage tank next and finally the lowest through the tube 529 of the exchanger 520. It will fur temperature storage tank. The same result may be

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achieved if the coils 515-55 are connected to output said second storage heat transfer link means compris heat exchanger 520 in parallel. ing a second storage working fluid having a pre The various embodiments of the heat storage loop scribed vaporizing temperature and pressure range, and heat recovery loop have been described in specific a second input heat exchanger serially connected to configurations, however, it is to be understood that any 5 said first input heat exchanger so that the heated one of the heat storage loops may be used with any one output of said heat source passes therethrough only of the heat recovery loops. This is because there is no after said heated output has passed through said positive connection between the heat storage loops and first input heat exchanger, said second input heat the heat recovery loops. exchanger carrying the second storage working While specific embodiments of the invention have 10 fluid therein in a heat exchange relationship with been disclosed herein, it is to be understood that full use said heated output passing therethrough to cause may be used of modifications, substitutions and equiva heat remaining in said heated output after passage lents without departing from the scope of the invented through said first input heat exchanger to vaporize concept. said second storage working fluid in said second What is claimed as invention is: 15 input heat exchanger, said second input heat ex 1. A heat transfer system comprising: changer located at a second input elevation; and a a heat source generating a heated output; second output heat exchanger operatively con first heat storage means capable of storing heat; nected to said second input heat exchanger for second heat storage means capable of storing heat; receiving vaporized second storage working fluid first storage heat transfer link means in a heat ex- 20 from said second input heat exchanger and for change relationship with said heated output of said returning condensed second storage working fluid heat source to said first heat storage means to trans to said second input heat exchanger, said second fer heat from said heated output of said heat source output heat exchanger placing the vaporized sec to said first heat storage means; ond storage working fluid in a heat exchange rela second storage heat transfer link means in a heat 25 tionship with said second heat storage means and exchange relationship with said heated output of said second output heat exchanger located at a said heat source after said heated output of said second output elevation higher than said second heat source has passed through said first storage input elevation so that the heat transferred to the heat transfer link means in a heat exchange rela second storage working fluid in said second input tionship therewith to transfer heat remaining in 30 heat exchanger vaporizes the second storage work said heated output from said heat source after pas ing fluid, the vaporized second storage working sage through said first storage heat transfer link to fluid rises to said second output heat exchanger, said second heat storage means; and the heat in the vaporized second storage work said first storage heat transfer link means comprising ing fluid is transferred to said second heat storage a first storage working fluid having a prescribed 35 means through said second output heat exchanger vaporizing temperature and pressure range, a first as long as the temperature of said second heat stor input heat exchanger carrying the first storage age means is lower than the temperature of the working fluid therein in a heat exchange relation heated output of said heat source after its passage ship with said heated fluid output from said heat through said first input heat exchanger to cause the source to cause said heated output to selectively 40 vaporized second storage working fluid in said vaporize said first storage working fluid in said first second output heat exchanger to condense where heat exchanger, said first heat exchanger located at upon the condensed second storage working fluid a first input elevation; and a first output heat ex flows back to said second input heat exchanger changer operatively connected to said first input under the force of gravity for revaporization in said heat exchanger for receiving vaporized first stor- 45 second input heat exchanger. age working fluid from said first input heat ex 2. A heat transfer system comprising: changer and for returning condensed first storage first heat storage means capable of storing heat; working fluid to said first input heat exchanger, second heat storage means capable of storing heat said first output heat exchanger placing the vapor where the temperature in said second heat storage ized first storage working fluid in a heat exchange 50 means is normally initially higher than the tempera relationship with said first heat storage means, and ture in said first heat storage means; said first output exchanger located at a first output heat sink means having an operating fluid to be elevation higher than said first input elevation so heated;

that the heat transferred to the first storage work first recovery heat transfer link means in a heat ex ing fluid in said first input heat exchanger vaporizes 55 change relationship with said first heat storage the first storage working fluid, the vaporized first means to transfer heat from said first heat storage storage working fluid rises to said first output heat means to said operating fluid of said heat sink exchanger, and the heat in the vaporized first stor means;

age working fluid is transferred to said first heat second recovery heat transfer link means in a heat storage means through said second heat exchanger 60 exchange relationship with said second heat stor as long as the temperature of said first heat storage age means to transfer heat from said second heat means is lower than the temperature of the heated storage means to said operating fluid of said heat output of said heat source to cause the vaporized sink means after said operating fluid has passed first storage working fluid in said first output heat through said first recovery heat transfer link in a exchanger to condense whereupon the condensed 65 heat transfer relationship therewith; first storage working fluid flows back to said first said first recovery heat transfer link means compris input heat exchanger under the force of gravity for ing a first recovery working fluid having a pre revaporization in said first input heat exchanger; scribed vaporizing temperature and pressure range,

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a first input heat exchanger carrying the first re as the temperature of the operating fluid of said covery working fluid therein in a heat exchange heat sink means passing through said second output relationship with said first heat storage means to heat exchanger after passage through said first cause said first heat storage means to vaporize said output heat exchanger is lower than the tempera first recovery working fluid in said first input heat 5 ture of said second heat storage means to cause the exchanger, said first heat exchanger located at a vaporized second recovery working fluid in said first input elevation; and a first output heat ex second output heat exchanger to condense where changer operatively connected to said first input upon the condensed second recovery working fluid heat exchanger for receiving the vaporized first flows back to said second input heat exchanger recovery working fluid from said first input heat 10 under the force of gravity for revaporization in said exchanger, said first output heat exchanger placing second input heat exchanger. the vaporized first recovery working fluid in a heat 3. A heat transfer system comprising: exchange relationship with the operating fluid of a heat source generating a heated output; said heat sink means, and said first output heat a heat sink means for receiving heat including first exchanger located at a first output elevation higher 15 and second heat storage means; than said first input elevation so that the heat trans a working fluid having a prescribed vaporization ferred to the first recovery working fluid from said temperature and pressure range; first heat storage means vaporizes the first recov input heat exchange means carrying the working ery working fluid, the vaporized first recovery fluid therein in a heat exchange relationship with working fluid rises to said first output heat ex- 20 said heat source to cause said heat source to vapor changer, and the heat in the vaporized first recov ize said working fluid in said input heat exchange ery working fluid is transferred to the operating means, said input heat exchange means located at fluid of said heat sink means through said first out an input elevation, said input exchange means in put heat exchanger as long as the temperature of cluding a first input heat exchanger and a second the operating fluid of said heat sink means passing 25 input heat exchanger, said second input heat ex through said first output heat exchanger is lower changer serially connected with said first input than the temperature of said first heat storage heat exchanger to said heat source so that the means to cause the vaporized first recovery work heated output from said heat source passes serially ing fluid in said first output heat exchanger to con through said first and second input heat exchang dense whereupon the condensed first recovery 30 ers; and, working fluid flows back to said first input heat output heat exchange means operatively connected to exchanger under the force of gravity for revapori said input heat exchange means for receiving va zation in said first input heat exchanger; and, porized working fluid from said input heat ex said second heat recovery link means comprising a change means, and for returning condensed work Second recovery working fluid having a prescribed 35 ing fluid to said input heat exchange means, said vaporizing temperature and pressure range, a sec output heat exchange means placing the vaporized ond input heat exchanger carrying the second re working fluid in a heat exchange relationship with covery working fluid therein in a heat exchange said heat sink means, and said output heat exchange relationship with said second heat storage means to means located at an output elevation higher than cause said second heat storage means to vaporize 40 said input elevation so that the heat transferred to said second recovery working fluid in said second the working fluid in said input heat exchange input heat exchanger, said second input heat ex means vaporizes the working fluid, the vaporized changer located at a second input elevation; and a working fluid rises to said output heat exchange second output heat exchanger operatively con means, the heat in the vaporized working fluid is nected to said second input heat exchanger for 45 transferred to said heat sink means through said receiving the vaporized second recovery working output heat exchange means as long as the tempera fluid from said second input heat exchanger and for ture of said heat sink means is lower than the tem returning the condensed second recovery working perature of said heat source to cause the vaporized fluid to said second input heat exchanger, said sec working fluid in said output heat exchange means ond output heat exchanger connected to said first 50 to condense whereupon the condensed working output heat exchanger so that the operating fluid of fluid flows back to said input heat exchange means said heat sink means passes through said second under the force of gravity for revaporization in said output heat exchanger only after passage through input heat exchange means, said output heat ex Said first output heat exchanger and placing the change means including a first output heat ex vaporized second recovery working fluid in a heat 55 changer and a second output heat exchanger, said exchange relationship with the operating fluid of first ouput heat exchanger operatively connected Said heat sink means after its passage through said to said first input heat exchanger for receiving first output heat exchanger, said second output heat vaporized working fluid from said first input heat exchanger located at a second output elevation exchanger and placing the vaporized working fluid higher than said second input elevation so that the 60 from said first input heat exchanger in a heat ex heat transferred to the second recovery working change relationship with said first heat storage fluid from said second heat storage means vapor. means so that heat in the vaporized working fluid is izes the second recovery working fluid, the vapor transferred to said first heat storage means through ized Second recovery working fluid rises to said said first output heat exchanger as long as the tem Second output heat exchanger, and the heat in the 65 perature of said first heat storage means is lower vaporized second recovery working fluid is trans than the temperature of the heated output from said ferred to the operating fluid of said heat sink means heat source during passage through said first input through said second output heat exchanger as long heat exchanger to cause the vaporized working

Page 14

fluid in said first output heat exchanger to condense ing fluid in a heat exchange relationship with said first and the condensed working fluid to flow back into heat storage means so that heat from the first heat stor said first input heat exchanger under the force of age means is transferred to said heat driven device gravity for revaporization in said first input heat through said first recovery output heat exchanger as exchanger, and said second output heat exchanger long as the temperature of said first heat storage means operatively connected to said second input heat is higher than the temperature of the operating fluid of exchanger for receiving vaporized working fluid said heat driven device passing through said first recov from said second input heat exchanger and placing ery output heat exchanger to cause the vaporized work the vaporized working fluid from said second input ing fluid in said first recovery output heat exchanger to heat exchanger in a heat exchange relationship 10 condense and the condensed working fluid to flow back with said second heat storage means so that heat in into said first recovery input heat exchanger under the the vaporized working fluid is transferred to said force of gravity for revaporization in said first recovery second heat storage means through said second input heat exchanger, and said second recovery input output heat exchanger as long as the temperature heat exchanger operatively connected to said second of said second heat storage means is lower than the 15 recovery output heat exchanger for placing the vapor temperature of the heated output of said heat source during passage through said second input ized working fluid in a heat exchange relationship with heat exchanger to cause the vaporized working second heat heat said second storage means so that heat from said fluid in said second output heat exchanger to con driven device throughmeans storage said is transferred to said heat second recovery output heat dense and to flow back to said second input heat 20 exchanger as long as the temperature of said second exchanger under the force of gravity for revapori heat storage means is higher than the temperature of the zation in said second input heat exchanger.

4. The heat transfer system of claim 3 further includ sage through said second output heat exchangerpas operating fluid of said heat driven device during

ing a heat driven device having an operating fluid to be cause the vaporized working fluid in said second recov heated; and further including recovery output exchange 25 ery output heat exchanger to condense and to flow back means comprising a first recovery output heat ex changer and a second recovery output heat exchanger, to said second recovery input heat exchanger under the said second recovery output heat exchanger serially force of gravity for revaporization in said second recov connected with said first recovery output heat ex ery input heat exchanger.

changer to said heat driven device so that the operating 30 5. The heat transfer system of claim 4 wherein the fluid of said heat driven device passes serially through temperature of said first heat storage means is higher said first and second output recovery heat exchangers; than the temperature of said second heat storage means and, wherein said input heat exchange means includes a and wherein the operating fluid of said heat driven first recovery input heat exchanger and a second recov device passes first through said second recovery output ery input heat exchanger, said first recovery input heat 35 heat exchanger and then through said first recovery exchanger operatively connected to said first recovery output heat exchanger.

output heat exchanger for placing the vaporized work