CA2925630C

CA2925630C - Real-time passive cooling apparatus with optional integrated storage

Info

Publication number: CA2925630C
Application number: CA2925630A
Authority: CA
Inventors: Eric L. Bibeau
Original assignee: University of Manitoba
Current assignee: University of Manitoba
Priority date: 2015-05-07
Filing date: 2016-03-31
Publication date: 2023-09-05
Anticipated expiration: 2036-03-31
Also published as: CA2925630A1

Abstract

A real-time passive cooling apparatus reduces energy utilization in buildings using a vertical closed-loop two-phase thermosyphon with its condenser located externally of the building. The wind shear layer and the temperature of the air surrounding the condenser provide renewal cooling in real-time when the thermosyphon evaporator temperature is lower than the ambient outside temperature. A pump circulates a fluid coolant through a closed-loop piping network that includes a primary annulus formed by a pipe that encloses the thermosyphon evaporator. The pump is activated when a building cooling device temperature is above a temperature set point. There is an option to store sensible and latent energy in a secondary annulus formed by a larger pipe that surrounds the first annulus to reduce the intermittency of the real-time passive cooling apparatus. The thermosyphon can be integrated into the building to support building loads, and devices like lights, wind turbines, and solar panels

Description

REAL-TIME PASSIVE COOLING APPARATUS WITH OPTIONAL
INTEGRATED STORAGE
FIELD OF THE INVENTION
The disclosed apparatus is in the field of passive cooling using a vertical two-phase closed thermosyphon (TPCT) to displace energy that is used for cooling devices located inside buildings.
BACKGROUND
Independent cooling devices located in buildings consume energy to lower the temperature of an enclosed volume and often reject heat to the air inside the building. In some instances, the ambient temperature outside the building is colder than the enclosed volume temperature of the independent device. A
passive cooling apparatus allows reducing building energy loads to enhance the cooling of devices inside buildings. By using the colder ambient air and the wind, intermittent renewable cooling is possible in real-time at temperatures approximately between -20oC to 30oC. A passive cooling apparatus can reduce greenhouse gases when the building's cooling energy originates from fossil fuels.
Reducing building energy loads is particularly important for near-net zero buildings. The disclosed apparatus reduces the need for on-site electricity generation for near net-zero buildings, while eliminating compressor noise for extended periods. It is known that cooling loads for air-conditioning and refrigeration systems for residential and commercial buildings account for almost 10% of the electricity usage in Canada (Office of Energy Efficiency, ISBN 989-1-100-17240-8, 2011). Solar contribution of photovoltaic electricity is 6.5% to 21% of building loads depending on orientation (R. Companion, Energy & Buildings, 36(4), p. 321-328, 2004). This implies that the development of near net-zero buildings requires

2 displacing energy loads. Moreover, solar assisted cooling absorption systems contribute to net-zero building applications, but they compete for limited facade space.
Their cost is considerable making the use of absorption chillers and solar collectors economically challenging (M. Tiago and A.C. Oliveira, Applied Energy, 86, p.

957, 2009). As 70% of building facades in urban areas access less than 50% of available solar irradiation, it becomes mathematically difficult to achieve near net-zero buildings. The percentage of buildings that can achieve net-zero through energy efficiency and onsite generation becomes even more difficult for multi-floor buildings:
offsite generation and sprawl remain the main options. In Canada a 10,000 m2 supermarket will consume 1.9 GWhr of electricity for refrigeration a year which could be considerably reduced with the invention disclosed.
TPCT are well-known passive heat transfer devices with no moving parts. They consist of a closed vertical or inclined pipe with a controlled charge two-phase fluid and non-condensable gases removed. An important commercial application for TPCT is to re-freeze permafrost to stabilize foundations made unstable due to climate change effects in northern climates (Xu J. and Goering D.J., Cold Regions Science and Technology, 53(3), p 283-297, 2008). For such application, TPCT design and predictive models are relatively simple: a freezing cycle occurs over approximately a 6-month period, predictive accuracy is not important, and the overall heat transfer over a year is relatively minimal as the ground acts as an insulator once refrozen. Other applications of TPCT is to extract heat from a water reservoir during nighttime and use the water during the day to cool buildings with applications for seasonal and nocturnal cooling of buildings (Chotivisarut N. and Kiatsiriroat T., International Journal of Energy Research, 33(12), p 1089-1098, 2009). In such cases, the focus is on air conditioning and is not concerned with reducing the energy

3 consumed by cooling devices located inside buildings in real-time. In contrast, the real-time passive cooling apparatus disclosed herein for near net-zero buildings requires accurate predictive knowledge of the cross-correlation of temperature and wind conditions, the wind shear layer, and the cooling profile of building cooling devices.
TPCT have also been used in other applications which are not focused on reducing cooling loads of buildings. By way of example, cooling engines in vehicles (Suzuki M. et al., JSME International Journal, 41(4), p 927-935, 1998) and the charging and discharging of a thermal energy storage using a thermosyphon loop (Benne, K.S. and Homan K.0, Numerical Heat Transfer, 54(3), p 235-254, 2008).
United States Patent 5579830 discloses the use of an inclined heat pipe for passively cooling an enclosure with the heat pipe located inside a thermal storage device with the heat exchange occurring on the outside of the storage device.
The system does not interact with a separate cooling device to lower the overall net energy consumption, nor does it have active control of the amount of heat exchanged.
In a similar application, United States Patent 7096928 teaches how to use a flexible thermosyphon loop to extract heat from electronic devices and United States Patent Application 2007/0242438 teaches the use of an inclined TPCT for the same application. Canadian patent CA 2614540 Al teaches how to exchange heat passively using a TPCT between two air ducts with forced air flow for building HVAC
applications. There is considerable additional art for cooling electronic devices, including CPU's, using inclined TPCT and horizontal heat pipes. In all these passive cooling applications heat is extracted from an enclosure in real-time and rejected inside the room where the electronic device is located. In all these devices the net building heat load is unchanged as the rejected heat adds to the internal room

4 temperature which adds to building energy transfer system requirements. The art does not teach how to passively reject the heat of cooling devices to the outside ambient air that surrounds the building envelop. All these passive electronic cooling devices are not subject to the condition that when vu(TR-T.) is negative there is no .. heat flow and they do not work. For the passive cooling apparatus disclosed, this condition occurs for extended periods of time in the order of hours or even months.
In prior art, the use of a TPCT to reduce the energy consumed by building cooling devices in real-time at temperature approximately between -20oC to +30oC cannot be found. The disclosed cooling apparatus of buildings adds to the known art. Freezers, refrigerators, server rooms, ice making machine for hockey arenas, HVAC, are just a few examples of cooling devices located in buildings for which the disclosed cooling apparatus can reduce energy use in real time.
There is a need for an apparatus with the TPCT evaporator coupled to building cooling devices using a liquid coolant such that heat is rejected to the air outside the building envelop.
Each TPCT can reduce the need to install separate vertical columns to secure third party devices like solar panels, wind mills, and telecommunication equipment by way of example, and can even be integrated into building structures to provide load bearing support.
The renewable cooling resource which characterizes energy available for building cooling devices can be postulated to be v"(TR-T.), where v is the wind velocity measured 10 m above the ground available from weather stations, TR is the refrigeration temperature (e.g., -18oC for freezers, -5oC for supermarket coolers, >20oC for computer data centers, >25oC for barns), and T. is the outside temperature. The term v"(TR-T.) is an intermittent renewable resource available to every type of building when the term is positive and can be integrated inside building cooling devices. The thermosyphon condenser is located either above the roof, the side of the building, or remotely above the ground level¨with the velocity at the condenser modified at each of these locations applying wind shear layer scaling laws and accounting for building or other structures impacting the boundary layer.
The

5 disclosed real-time passive cooling apparatus displaces energy used to operate building cooling devices in an amount that depends on the temperature set point of each cooling devices, the latitude and longitude coordinates of the building, the shape of the building, and the general landscape surrounding the building.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a heat transfer system for use with a building having an envelope which separates an interior space of the building from a surrounding exterior of the building and a cooling device within the interior space of the building which requires cooling, the system comprising:
a thermosyphon assembly comprising:
a closed thermosyphon chamber extending between an evaporator section and a condenser section arranged to be located in direct heat exchanging relationship with ambient air in the surrounding exterior of the building;
and a two-phase fluid within the closed thermosyphon chamber;
a heat exchanger chamber receiving a heat transfer fluid therein which at least partially surrounds the evaporator section of the thermosyphon chamber such that the heat transfer fluid is in direct heat exchanging relationship with the evaporator section of the thermosyphon chamber;
an insulation layer which insulates the evaporator section of the thermosyphon chamber and the heat exchanger chamber relative to respective

6 surroundings thereof;
piping for communicating between the heat exchanger chamber and the cooling device in a closed loop such that the heat exchanger fluid is in heat exchanging relationship with the cooling device; and a pump for circulating the heat transfer fluid through the piping between the cooling device and the heat exchanger chamber.
The present invention relates to using a plurality of TPCT to reduce energy consumed by cooling devices located inside buildings. Each TPCT is located close to the building or is part of the building, and can have its own fluid and internal pressure optimized for the cooling device temperature requirement and design constraints. Furthermore, each TPCT requires flowing a liquid coolant in a closed-loop piping network around each thermosyphon evaporator using a pump. The liquid coolant is then circulated inside a plurality of building cooling devices.
Each TPCT
evaporator then passively extracts the heat from the liquid coolant, rejecting that heat via the TPCT condenser that is exposed to an air flow surrounding the building envelop. The TPCT condenser can be located above the building rooftop, on the side of the building, or remotely above the ground level. Each TPCT condenser is continuously subjected in real-time to a variable ambient air temperature and wind shear layer. At the same time, the TPCT evaporator is subjected to a variable cooling load depending on the requirements of building cooling devices. The disclosed apparatus provides a method to remove heat from building cooling devices when the renewable cooling resource vcL6(TR-T..) is positive. To better match cooling loads of building devices with the renewable cooling resource outside the building envelop, an energy storage cavity that surrounds the evaporator and the liquid coolant can be added. The storage reduces the impact of the intermittency of the renewable cooling

7 resource to further decrease the energy used by cooling devices inside buildings by mitigating relatively large fluctuations in the wind velocity and changes in ambient air temperature. In addition, many buildings use vertical steel hollow members to support structural loads, and to support external devices like lights in a parking lot and solar panels. Each TPCT can be integrated into buildings as a load bearing member and can be used to secure third-party devices above ground.
Preferably the heat transfer fluid has a prescribed boiling point which is outside of an operating temperature range of the heat exchanger chamber such that the heat transfer fluid does not undergo a phase change.
Preferably the two-phase fluid in the thermosyphon chamber is a mixture of fluids having different boiling temperatures which does not undergo a phase change.
The heat exchanger chamber may comprise an annular portion which fully surrounds the evaporator section of the thermosyphon chamber.
Preferably the system further includes an energy storage chamber including an energy storage fluid therein which at least partially surrounds one or both of the evaporator section of the thermosyphon chamber and the heat exchanger chamber. Preferably the insulation layer insulates the energy storage chamber, the evaporator section of the thermosyphon chamber, and the heat exchanger chamber .. relative to the respective surroundings thereof.
When the heat exchanger chamber comprises an annular portion fully surrounding the evaporator section of the thermosyphon chamber, the energy storage chamber preferably comprises an annular portion fully surrounding the heat exchanger chamber, and the insulation layer preferably fully surrounds the energy storage chamber.

8 An auxiliary energy storage tank may be further provided which includes an energy storage fluid therein which is in heat exchanging relationship with the piping at a location downstream from the cooling device and upstream from the thermosyphon assembly.
A plurality of thermosyphon assemblies may be provided in parallel relationship with one another, in which each assembly comprises i) a closed thermosyphon chamber extending between an evaporator section and a condenser section arranged to be located in contact with ambient air in the surrounding exterior of the building, ii) a two-phase fluid within the closed thermosyphon chamber, and iii) a heat exchanger chamber which receives the heat transfer fluid therein and which at least partially surrounds the evaporator section of the thermosyphon chamber such that the heat transfer fluid is in direct heat exchanging relationship with the evaporator section thereof.
When provided in combination with a plurality of cooling devices, the piping is preferably connected between the heat exchanger chamber and each of the cooling devices in parallel relationship with one another.
Preferably a controller is operatively connected to the pump so as to be arranged to turn the pump on and off to control circulation of the heat transfer fluid through the piping. Preferably the controller is arranged to actuate the pump in response to a sensed temperature which exceeds an upper temperature limit of the system. The sensed temperature may be sensed by a temperature sensor in communication with the cooling device or in communication with the heat transfer fluid.
The system may be used in combination with a cooling device comprising a refrigeration cycle which is operational supplementary to the

9 thermosyphon assembly.
When the system is used in combination with a cooling device comprising a refrigeration cycle having a condenser section, the piping may be in heat exchanging relationship with the condenser section of the refrigeration cycle.
The thermosyphon assembly may extend through the envelope of the building such that the evaporator section is located within the interior space of the building. In this instance, the thermosyphon assembly preferably further comprises an adiabatic section extending between the evaporator section and the condenser section such that the evaporator section and the condenser section are spaced apart from one another in which the adiabatic section is insulated relative to respective surroundings thereof.
The thermosyphon assembly may extend through a 'roof portion of the building. The roof portion may include a main roof line and a well portion recessed relative to the main roof line, in which the condenser section is at least partially received within the well portion below the main roof line.
Preferably the thermosyphon assembly is located fully externally of the building, for example on building grounds, laterally to one side of the building.
The evaporator section of the thermosyphon evaporator may be located below ground.
In some instances, a portion of a boundary wall of the thermosyphon chamber may support a portion of a load of the building. The boundary wall of the thermosyphon chamber may also structurally support a load of an auxiliary device supported thereon.
A surface coating may be provided on an outside of the condenser section of the thermosyphon chamber which reflects solar radiation to increase the heat transfer rate to ambient air.
A plurality of heat transfer fins may be mounted in conductive relationship with at least one boundary wall of the condenser section of the thermosyphon chamber to increase the heat transfer rate to the ambient air.
5 The system may further include an auxiliary refrigerant cycle operatively connected in heat exchanging relationship with the thermosyphon chamber in proximity to the condenser section which actively cools the condenser section when ambient air is insufficient to meet cooling demands by the cooling device.
Various embodiments of the invention will now be described in

10 conjunction with the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevation cut away of an embodiment of the passive cooling apparatus of the present invention located inside a building showing one thermosyphon and one building cooling device.
FIG. 2 is an elevation cut away of a preferred embodiment of the passive cooling apparatus of the present invention located inside a building showing one thermosyphon and one building cooling device with integrated energy storage to reduce the impact of the intermittency of the renewable cooling resource.
FIG. 3 is a plan view of an embodiment of multiple passive cooling apparatus and building cooling devices with separate energy storage tank.
FIG. 4 is an elevation cut away of an embodiment of the passive cooling apparatus of the present invention with the thermosyphon condenser extending below the main roof line.
FIG. 5 is an elevation cut away of an embodiment of the passive cooling apparatus of the present invention located on the side of a building.

11 FIG. 6 is an elevation cut away of an embodiment of the passive cooling apparatus of the present invention located on the building grounds.
FIG. 7 is an elevation cut away of an embodiment of the passive cooling apparatus of the present invention located inside a building showing one thermosyphon and one building cooling device whose load is fully serviced by disclosed cooling apparatus.
In the drawings like characters of reference indicate corresponding parts in the different figures.
DETAILED DESCRIPTION
FIG 1 illustrates an embodiment of the invention showing a cross-sectional view of part of building 2 using a real-time passive cooling system to reduce the energy consumed by cooling device 1 located in building 2. Cooling device could be a plurality of such devices that performs a cooling function in real time in building 2 which by way of example, may be coolers, freezers, open refrigerate vegetable counters, ice rink refrigeration systems, air conditioning devices, heat pumps, chillers, electronic equipment cabinets, computer server cooling systems, etc.
Building 2 consists of roof 4, at least one floor 3, and walls which collectively form a building envelope which separates an interior space of the building from ambient air in a surrounding exterior of the building.
Cooling device 1 is consuming energy to keep the temperature inside cooling device 1 at a set temperature. The cooling device includes a target object or space which requires cooling and thus generates on ongoing cooling demand. The cooling device may rely entirely on the system of the present invention to meet the cooling demand. Alternatively, the cooling device may employ a conventional refrigeration cycle to assist in meeting the cooling demand by cooling the target object

12 or space only when the system of the present invention is not capable of meeting the cooling demand. Use of a refrigeration cycle in a supplementary manner to the cooling of the system of the present invention is shown at the left side of Figure 3.
Alternatively, the evaporator of the refrigeration cycle may be used to directly meet the cooling demands of the target object or space to be cooled, and the system of the present serves to remove heat from the condenser of the refrigeration cycle of the cooling device, as shown on the right side of Figure 3.
Thermosyphon assembly 5 is composed of closed loop pipe 6 defining a thermosyphon chamber therein which is functionally subdivided in three sections: a thermosyphon evaporator 7, a thermosyphon condenser 9 longitudinally opposed from the evaporator 7 at opposing ends relative to one another, and an optional thermosyphon adiabatic section 8 spanning between the evaporator and condenser.
The chamber is partially filled with two-phase fluid 16.
Thermosyphon condenser 9 is exposed to and in direct heat exchanging relationship with ambient air 11 having a variable temperature and moisture, variable solar radiation 15, and variable wind shear layer 10. Wind shear layer 10 on roof 4 may have a lower disturbed region, is a function of the shape of building 2, the roughness terrain surrounding building 2, the wind velocity, and the wind direction.
Fins 12 are optionally added to the outside of thermosyphon condenser 9 to increase heat transfer rate 13 to ambient air 11. Thermosyphon condenser 9 has exterior finish 14 that reflects solar radiation 15 to increase heat transfer 13 to ambient air 11.
Two-phase fluid 16 boils in thermosyphon evaporator 7 and the vapor phase rises upwards in pipe 6 when the temperature of ambient air Ills below the vapor temperature inside thermosyphon evaporator 7. When the thermosyphon vapor flows, it passes through adiabatic section 8 and changes to a liquid phase in

13 thermosyphon condenser 9, creating liquid film 19, which flows downwards back to thermosyphon evaporator 7.
Pipe 20 forms cavity 21 between the inner wall of pipe 20 and the outer wall of thermosyphon evaporator 7. The cavity 21 is a heat exchanger chamber which fully surrounds the circumference of the pipe forming the thermosyphon chamber at the evaporator section thereof. The heat exchanger chamber receives a heat transfer fluid therein which at least partially surrounds the evaporator section of the thermosyphon chamber such that the heat transfer fluid is in direct heat exchanging relationship with the evaporator section of the thermosyphon chamber.
Preferably, insulation 17 is added as a continuous layer to restrict heat loss to the building ambient air from pipe 20 and thermosyphon adiabatic section 8.
The insulation layer forms a complete envelope which Insulates the evaporator section of the thermosyphon chamber and the heat exchanger chamber relative to respective surroundings thereof.
To reduce energy consumed by cooling device 1, pump 24 circulates liquid coolant 18 through cavity 21 and cooling device 1 in closed-loop pipe network 41. Controller 22 measures temperature of liquid coolant 18 and temperature inside cooling device 1 and controls operation of pump 24 accordingly. Optionally, liquid coolant 18 flowing through closed-loop pipe network 41 can be a slurry composed of liquid and solid phases, and can contain nanoparticies to improve heat transfer. The controller is thus operatively connected to the pump so as to be arranged to turn the pump on and off to control circulation of the heat transfer fluid through piping which communicates between the heat exchanger chamber and the cooling device in a closed loop such that the heat exchanger fluid is in heat exchanging relationship with the cooling device. The controller is typically arranged to actuate the pump in Date Recue/Date Received 2022-06-06

14 response to a sensed temperature which exceeds an upper temperature limit of the system and to cease actuation of the pump when below a lower temperature limit of the system. The temperature may be sensed by a temperature sensor in communication with the cooling device and/or a temperature sensor in communication with the heat transfer fluid.
Thermosyphon 5 optionally supports part of the weight of roof 4. More particularly, in this instance at least a portion of a boundary wall of the thermosyphon chamber structurally supports at least a portion of a load of the building.
FIG 2 shows an alternative embodiment where an additional pipe 26 is added to form energy storage cavity 27 formed between the inner wall of pipe 26 and the outer wall of pipe 20. The energy storage chamber includes an energy storage fluid therein which at least partially surrounds one or both of the evaporator section of the thermosyphon chamber and the heat exchanger chamber. In this instance, the insulation layer collectively envelopes and insulates the energy storage chamber, the evaporator section, and the heat exchanger chamber relative to the respective surroundings thereof. Storage fluid 28 fills energy storage cavity 27 and energy is transferred through pipe 20. Optionally, storage fluid 28 can undergo phase change forming solid phase 29. Should storage fluid 28 expand when turning to solid phase 29, potential for heaving is reduced by creating fluid layer melt 30 when pump 24 is on. Controller 22 senses pressure in energy storage cavity 27 resulting from formation of solid phase 29 and can shut off valve 31 to prevent damage.
Storage fluid 28 can be a slurry composed of liquid and solid phases and contain nanoparticles to enhance heat transfer. Thermosyphon condenser 9 can support a plurality of third-party device 32 that require elevated support like solar panels in this embodiment.

FIG 3 shows an alternative embodiment where liquid coolant 18 circulates through closed-loop piping network 41, cavities 21, cooling devices 1, pump 24, and energy storage tank 40. Energy storage tank 40 contains storage fluid 28 that can undergo phase change, can be a slurry composed of liquid and solid phases, and 5 can contain nanoparticles to improve heat transfer. The auxiliary energy storage tank 40 which includes an energy storage fluid therein is thus in heat exchanging relationship with the piping at a location downstream from the cooling device and upstream from the thermosyphon assembly.
FIG 3 also shows a plurality of thermosyphon assemblies in parallel relationship with one another, in which each thermosyphon assembly comprises i) a closed thermosyphon chamber extending between an evaporator section and a condenser section arranged to be located in contact with ambient air in the surrounding exterior of the building, ii) a two-phase fluid within the closed thermosyphon chamber, and iii) a heat exchanger chamber which receives the heat

15 transfer fluid therein and which at least partially surrounds the evaporator section of the thermosyphon chamber such that the heat transfer fluid is in direct heat exchanging relationship with the evaporator section thereof.
FIG 3 also shows a plurality of the cooling devices in which the piping is connected between the heat exchanger chamber and each of the cooling devices in parallel relationship with one another. Liquid coolant 18 can be integrated into cooling device 1 by adding by way of example heat exchanger 51 and fan 52 that is separate of refrigeration cycle 25, and by way of on other example integrating heat exchanger 53 into refrigeration cycle 25. Bypass valve 60 can redirect liquid coolant 17 to energy storage tank 40.
FIG 4 shows an alternative embodiment to Fig 1 where roof 4 has a

16 built-in recess 42 that allows to' extended length of thermosyphon condenser 9 without extending the height of thermosyphon 5, making more contact with ambient air 11. As heat transfer rate 13 is mainly controlled by the exposure area of thermosyphon condenser 9 to the outside air, recess 42 helps increase heat transfer rate 13. Fins 12 can act as a rain and snow guard to prevent liquid accumulating at the bottom of the recess 42.
FIG 5 shows the real-time passive cooling apparatus located adjacent to building side 52, with condenser 9 exposed to wind shear layer 10. Wind shear layer 10 may also be directed 900 to what is shown into or out of the figure.
Therrnosyphon evaporator 7 is shown located below ground level within ground 46.
Liquid coolant 8 circulates in closed-loop piping network 41 (partially shown) to a plurality of cooling devices 1 (not shown) inside building 2 (not shown).
FIG 8 shows a real-time passive cooling apparatus located remotely on building grounds 45. Thermosyphon condenser 9 Is exposed to wind shear layer and thermosyphon condenser 7 is located below ground level within ground 46.
Liquid coolant 18 circulates in closed-loop piping network 41 (partially shown) to a plurality of cooling device 1 (not shown) inside building 2. Parking lots lights 47 are secured to thermosyphon 5 in this embodiment.
FIG 7 shows an alternative embodiment where heat exchanger 50 is added around thermosyphon adiabatic section 8 to actively remove the heat from thermosyphon 5 when required. This allows to remove refrigeration cycles 25 In cooling devices 1 and replace these with a larger refrigeration plant (not shown) that services each thermosyphon condenser 9 when required using refrigerant 52 and building distribution piping 51.
The thermosyphon evaporator can be also located below ground in FIG
Date Recue/Date Received 2022-06-06

17 1, FIG 2 and FIG 4 and above ground in FIG 5 and FIG 6. Two-phase fluid 16 inside thermosyphon 5 can be replaced by a fluid that does not undergo a phase change resulting in higher internal heat transfer resistance. Said fluid can be a mixture composed of fluids that vaporize at different temperatures to maintain two-phase heat transfer rates over a wider range of operating temperatures. The disclosed invention can include a plurality of components interconnected using closed-loop piping network 41: thermosyphon 5, building cooling device 5, energy storage cavity 27, pump 24, and energy storage tank 40. In addition, the effect of wind shear layer 10 varies depending if thermosyphon condenser 9 is located above roof 4, adjacent to building side 52, and above building ground 45 and can be predicted using fluid dynamics boundary layer scaling laws, experimental data, and computational methods to predict heat transfer rate 13 based on the available intermittent renewable cooling resource v .6(TR-T..).
Since various modifications can be made in my invention as herein above described, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

Claims

CLAIMS:

1. A heat transfer system for use with a building having an envelope which separates an interior space of the building from a surrounding exterior of the building and a cooling device within the interior space of the building which requires cooling, the system comprising:
a thermosyphon assembly comprising:
a closed thermosyphon chamber extending between an evaporator section and a condenser section arranged to be located in direct heat exchanging relationship with ambient air in the surrounding exterior of the building;
and a two-phase fluid within the closed thermosyphon chamber;
a heat exchanger chamber receiving a heat transfer fluid therein which at least partially surrounds the evaporator section of the thermosyphon chamber such that the heat transfer fluid is in direct heat exchanging relationship with the evaporator section of the thermosyphon chamber;
an insulation layer which insulates the evaporator section of the thermosyphon chamber and the heat exchanger chamber relative to respective surroundings thereof;
piping for communicating between the heat exchanger chamber and the cooling device in a closed loop such that the heat exchanger fluid is in heat exchanging relationship with the cooling device; and a pump for circulating the heat transfer fluid through the piping between the cooling device and the heat exchanger chamber.

2. The system according to Claim 1 wherein the heat transfer fluid has a prescribed boiling point which is outside of an operating temperature range of the heat exchanger chamber such that the heat transfer fluid does not undergo a phase change.

3. The system according to either one of Claims 1 or 2 wherein the two-phase fluid in the thermosyphon chamber does not undergo a phase change.

4. The system according to either one of Claims 1 or 2 wherein the two-phase fluid in the thermosyphon chamber is a mixture of fluids having different boiling temperatures.

5. The system according to any one of Claims 1 through 4 wherein the heat exchanger chamber comprises an annular portion which fully surrounds the evaporator section of the thermosyphon chamber.

6. The system according to any one of Claims 1 through 4 further comprising an energy storage chamber including an energy storage fluid therein which at least partially surrounds one or both of the evaporator section of the thermosyphon chamber and the heat exchanger chamber, wherein the insulation layer Insulates the energy storage chamber, the evaporator section of the thermosyphon chamber, and the heat exchanger chamber relative to the respective surroundings thereof.

7. The system according to Claim 6 wherein the heat exchanger chamber comprises an annular portion fully surrounding the evaporator section of the thermosyphon chamber, wherein the energy storage chamber comprises an annular portion fully surrounding the heat exchanger chamber, and wherein the insulation layer fully surrounds the energy storage chamber.

8. The system according to any one of Claims 1 through 7 further comprising an auxiliary energy storage tank including an energy storage fluid therein which is in heat exchanging relationship with the piping at a location downstream from the cooling device and upstream from the thermosyphon assembly.

9. The system according to any one of Claims 1 through 8 further comprising a plurality of thermosyphon assemblies in parallel relationship with one another, each assembly comprising i) a closed thermosyphon chamber extending between an evaporator section and a condenser section arranged to be located in contact with ambient air in the surrounding exterior of the building, ii) a two-phase fluid within the closed thermosyphon chamber, and iii) a heat exchanger chamber which receives the heat transfer fluid therein and which at least partially surrounds the evaporator section of the thermosyphon chamber such that the heat transfer fluid is in direct heat exchanging relationship with the evaporator section thereof.

10. The system according to any one of Claims 1 through 9 in combination with a plurality of cooling devices, wherein the piping is connected between the heat exchanger chamber and each of the cooling devices in parallel relationship with one another.

11 The system according to any one of Claims 1 through 10 further comprising a controller operatively connected to the pump so as to be arranged to turn the pump on and off to control circulation of the heat transfer fluid through the piping.

12. The system according to Claim 11 wherein the controller is arranged to actuate the pump in response to a sensed temperature which exceeds an upper temperature limit of the system.

13. The system according to Claim 12 wherein the sensed temperature is sensed by a temperature sensor in communication with the cooling device.

14. The system according to Claim 12 wherein the sensed temperature is sensed by a temperature sensor in communication with the heat transfer fluid.

15. The system according to any one of Claims 1 through 14 in combination with a cooling device comprising a refrigeration cycle which is operational supplementary to the thermosyphon assembly.

16. The system according to any one of Claims 1 through 14 in combination with a cooling device comprising a refrigeration cycle having a condenser section, the piping being in heat exchanging relationship with the condenser section of the refrigeration cycle.

17. The system according to any one of Claims 1 through 16 wherein the thermosyphon assembly extends through the envelope of the building such that the evaporator section is located within the interior space of the building.

18. The system according to Claim 17 wherein the thermosyphon assembly further comprises an adiabatic section extending between the evaporator section and the condenser section such that the evaporator section and the condenser section are spaced apart from one another, the adiabatic section being insulated relative to respective surroundings thereof.

19. The system according to either one of Claims 17 or 18 wherein the thermosyphon assembly extends through a roof portion of the building.

20. The system according to Claim 19 for a building in which the roof portion includes a main roof line and a well portion recessed relative to the main roof line, wherein the condenser section is at least partially received within the well portion below the main roof line.

21. The system according to any one of Claims 1 through 16 wherein the thermosyphon assembly is located fully externally of the building.

22. The system according to Claim 21 wherein the thermosyphon assembly is located on building grounds.

23. The system according to any one of Claims 1 through 22 wherein the thermosyphon assembly is located laterally to one side of the building.

24. The system according to any one of Claims 1 through 23 wherein the evaporator section of the thermosyphon evaporator is located below ground.

25. The system according to any one of Claims 1 through 24 wherein at least a portion of a boundary wall of the thermosyphon chamber supports at least a portion of a load of the building.

26. The system according to any one of Claims 1 through 25 wherein at least a portion of a boundary wall of the thermosyphon chamber structurally supports a load of an auxiliary device supported thereon.

27. The system according to any one of Claims 1 through 26 further comprising a surface coating on an outside of the condenser section of the thermosyphon chamber which reflects solar radiation to increase the heat transfer rate to ambient air.

28. The system according to any one of Claims 1 through 27 further comprising a plurality of heat transfer fins in conductive relationship with at least one boundary wall of the condenser section of the thermosyphon chamber to increase the heat transfer rate to the ambient air.

29. The system according to any one of Claims 1 through 28 further comprising an auxiliary refrigerant cycle operatively connected in heat exchanging relationship with the thermosyphon chamber in proximity to the condenser section which actively cools the condenser section when ambient air is insufficient to meet cooling demands by the cooling device.