US20120175082A1

US20120175082A1 - Solar heat pipe heat exchanger

Info

Publication number: US20120175082A1
Application number: US13/496,158
Authority: US
Inventors: Ronald E. Kmetovicz; Steven N. Sanders
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-09-14
Filing date: 2010-09-14
Publication date: 2012-07-12
Also published as: WO2011032164A3; WO2011032164A2

Abstract

This invention relates to the process of collecting heat and removing heat from a heat pipe for solar energy applications. More specifically, this invention is a solar energy system that elegantly couples a heat pipe and a single header heat transfer assembly that has the capability of interchangeable operational designs using solar collector panel, solar vacuum tube, or integrated solar thermal and photovoltaic array configurations. The header assembly is structurally and thermally connected to the heat pipe by a heat pipe receiver which surrounds the condenser end of the heat pipe and plugs into the interior of the header assembly.

Description

DESCRIPTION

This application claim priority of Provisional Application Ser. No. 61/242,198, filed Sep. 14, 2009, the entire disclosure of which is incorporated herein by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a solar heat pipe heat exchanger and, more particularly, to a single header solar heat pipe heat exchanger with a header assembly having a plurality of inlet fluid channels formed by heat transfer fins and a single return fluid channel for the circulation of heat transfer fluid, and having at least one heat pipe attachment that contains a working fluid operating in a closed loop system within the heat pipe. Each heat pipe is attached to the header assembly at a connection junction by means of a single clamp, wherein collected heat is transferred from the heat pipe to the header assembly by the process of evaporation and condensation. The heat pipe heat exchanger has the capability of interchangeable operational designs using solar collector panel, solar vacuum tube, or integrated solar thermal and photovoltaic array configurations in a closed loop drainback solar heating system.
2. Related Art
Simple to construct solar heat pipe designs currently on the market fail to optimally mate a constant diameter heat pipe to the header assembly. The length of the heat pipe condenser grows proportionally to the total length of the heat pipe. For example, a 90 inch heat pipe may require a 6 to 9 inch condenser in order to maintain efficient heat pipe operation. In addition, the width of the header must be greater than the length of the heat pipe condenser which is typically in the range of 6 to 9 inches. As such, if piping were used, the header diameter would be large and heat transfer from the heat pipe condenser to the heat transfer fluid flowing through the large diameter header pipe becomes inefficient.
No header implementation currently exists that accepts a constant diameter heat pipe and efficiently transfers the heat from the heat pipe condenser to the heat transfer fluid circulating within the header. Existing art modifies the shape of the heat pipe condenser to best suit heat transfer within the header assembly, usually by placing and thermally attaching the condenser region between two header pipes. The current design techniques tend to produce a tall or thick structure not suitable for use in solar panels.
Efficient heat transfer from the heat pipe condenser to the heat transfer fluid in the header assembly presents significant design challenges. The area of the heat pipe condenser in contact with the heat transfer fluid within the header tends to be small when the heat pipe condenser is inserted into a small pipe, and thus, resulting in very poor heat transfer. A heat exchanger improves thermal efficiency by increasing the effective area of the heat pipe condenser in thermal contact with the heat transfer fluid. Existing implementations increase this area by a factor of two or less by altering the shape of the heat pipe condenser.
Headers used in solar panel structures differ significantly from those used in solar vacuum tube structures. Solar panel structures use a bottom header, risers and a top header; a configuration that does not work with heat pipe based designs. Solar vacuum tube designs use a single top header design which proves to be thermally inefficient when used with non-vacuum insulated heat pipe based absorbers. No existing header configuration works with both solar panel and vacuum tube design structures.
Existing solar panel and vacuum tube designs require plumbing skills to install and service. Existing header connections are most often made by soldering copper tubing. When done, the outlet from the array is spaced away from the inlet by the dimensions of the array, requiring running an insulated return line. Inlet and return lines are frequently soldered to their respective headers.
Current design methods are not conducive for building an integrated solar thermal and photovoltaic panel. The non-modular nature of existing solar panel designs mandates covering the entire solar surface with photovoltaic material. Thermal expansion and contraction results in the deformation of the absorber area which tends to fracture the photovoltaic cells, the material attaching them thermally to the panel, or both. A failure of one cell shuts down the whole array containing that cell. The integrated assembly contains a photovoltaic array and a solar thermal array, but the photovoltaic array does not support solar thermal operation, and the solar thermal array does not support photovoltaic operation.
Various solar collector panel designs currently on the market utilize a process of condensation and evaporation. Existing designs collect solar radiation with absorber tubes containing a working fluid, wherein the absorber tubes connect mechanically and thermally to the header pipe at a connection junction. The heat collected by the absorber tubes is transferred to the heat exchange fluid in the header pipe using a condensation and evaporation process near the connection junction. Some current designs have a complicated mechanical and thermal attachment between the absorber tubes and the header pipe. The complicated attachment junction makes replacement and repair difficult, and in some designs, impossible. The complexity of the current junction connection designs also increases the manufacturing expense.
Some exemplary current designs are:
U.S. Pat. No. 4,313,423 (Mandjuri) discloses a heat pipe wherein the condenser section is inserted into the heat exchanger header and secured therein by a gasket and a threaded connection.
U.S. Pat. No. 4,686,661 (Garrison) discloses a thermal energy collection system wherein heat is transferred directly from the energy collector to the heat storage tank, and not into a heat exchanger header.
U.S. Published Application US2010/0108055 (Davis, et al.) discloses a solar collector with a special end fitting that may be connected together with end fittings of two neighboring collectors to provide fluid flow paths without the need for a manifold or header.

SUMMARY OF THE INVENTION

The invention relates to a solar heat pipe heat exchanger, and more particularly, a solar heat pipe heat exchanger having a single header assembly with multiple inlet fluid channels and a single return fluid channel wherein heat transfer fluid flows in a horseshoe direction, and having at least one constant diameter heat pipe attached at the connection junction to the header assembly by means of a single clamp device, and that the design supports interchangeable solar collector panel, solar vacuum tube, or integrated solar thermal and photovoltaic array configurations for the collection of solar radiation to operate in a closed loop drainback solar heating system.
On one end of the header assembly the inlet opening is fixed beneath the return opening; and the inlet return cap molds the fluid flow loop at the opposite end of the header assembly. A plurality of heat transfer fins structure the inlet fluid channel compartments for the purpose of providing increased surface area for the heat transfer process. The header assembly design operates using a constant diameter heat pipe. The heat pipe condenser region plugs into the header assembly which is designed to matingly accept a relatively long condenser. The condenser length divided by the evaporator length is optimized for efficient heat pipe operation and for the transport of heat to the heat transfer fluid through the heat exchanger built into the header assembly. The simple design of the header assembly requires no plumbing skills for making connections.
Enhanced efficiency is achieved with a header assembly design that completely surrounds the condenser region of each heat pipe and that also serves as an absorber which renders up to 95% solar absorptive interior space. In addition, the heat exchanger design within the header assembly significantly increases the effective thermal area between the heat pipe condenser and the circulating heat transfer fluid. The multiple inlet fluid channels in the heat exchanger region of the header assembly narrow near the condenser region of each heat pipe and transfer more heat as heat transfer fluid turbulence increases.
One embodiment described in this invention, the solar collector panel, supports the attachment of multiple constant diameter heat pipe absorber assembly units to the single header assembly. Each heat pipe absorber assembly simply attaches mechanically and thermally to the header assembly using a single clamp. The heat pipe absorber assembly includes an absorber fin attached to a heat pipe for collecting incident solar radiation. The working fluid vapor within the heat pipe transfers heat to the header assembly through the process of evaporation and condensation.
The solar collector panel provides a strong structure; and a weather resistant seal, without the use of a perimeter gasket, is formed by mating the shell bottom into the shell top. The shell is assembled from bottom to top and disassembled from top to bottom. The shell design is easy to manufacture, install, service and repair. In addition, the shell may be made of plastic, providing an inexpensive and lightweight solution.
Another embodiment described in this invention, the vacuum tube array, uses the same constant diameter heat pipe described in the solar collector panel design; with the single header assembly supporting the attachment of multiple vacuum tube heat pipes which forum the vacuum tube array. The vacuum tube array provides an inexpensive vacuum insulation solution by using a single wall glass tube between each heat pipe absorber and the sky. Metal bellows form the seal between the glass tube and the heat pipe and allow for thermal expansion and contraction of the finned heat pipe without stressing the glass.
Yet another embodiment described in this invention, the integrated solar thermal and photovoltaic panel design, is compatible with the same header assembly described above for the solar collector panel and vacuum tube array, and uses the same constant diameter heat pipe. The photovoltaic cells mount onto the absorber fins which are attached to each heat pipe. The heat pipe design keeps the photovoltaic cells' temperature in close proximity to the heat transfer fluid temperature within the header assembly. The mating shell for the integrated solar thermal and photovoltaic panel is the same as described above in the solar collector panel design.
The integrated solar thermal and photovoltaic design provides electrical output equivalent to that of photovoltaic panels not having heating capability; plus, the thermal output is nearly equivalent to a solar panel without electrical capability. This combination provides low cost electricity and heat. A computer control may optimize the use of either the electric or thermal system. The header heat exchanger can be supplied with cooled heat transfer fluid not circulating through the heat storage tank, and thus, optimize electrical generation by cooling the photovoltaic cells. To optimize the collection of heat, the controller may allow the heat transfer fluid to increase in temperature and warm the heat storage tank. As such, the photovoltaic system remains operational, but at reduced efficiency. Heat collection functions effectively, but is limited by the absorptivity, emissivity and reflectivity of the photovoltaic cells.

BRIEF DESCRIPTION OF THE DRAWINGS

A complete understanding of the present invention may be assisted by reference to the accompanying drawings, when considered in conjunction with the subsequent, detailed description, in which:

FIGS. 1A-E are detail, side views of a header assembly 101 showing detail of the header return 110, header inlet 120, heat pipe receiver 130, and header flange 140 components;

FIG. 1F and FIGS. 1G-K are detail views of an alternate header inlet design including a three-dimensional view (FIG. 1F), front view details (FIG. 1G-I) of the header inlet 120 a, and side-sliced view (FIG. 1J and K) of the finned heat pipe receiver 131 a components;

FIGS. 2A and B are three-dimensional and three-dimensional sliced views, respectively, of the header assembly 101;

FIGS. 3A-G is a set of three-dimensional and rotated detail views of a header assembly 101

inlet return cap

150, end cap 160, heat pipe clamp 180 and gasket 170 components;

FIG. 4 is a three-dimensional view, with a sliced expanded detail of a heat pipe absorber assembly 201;

FIG. 4 a is a three-dimensional view, with a sliced expanded detail of a heat pipe photovoltaic assembly 221;

FIG. 5 is a top view of an absorber header assembly 250 with a heat pipe absorber assembly 201, or a heat pipe photovoltaic assembly 221;

FIG. 6 is a three-dimensional view of an exploded panel enclosure assembly 301 including an enlarged sliced detail view of the frame extrusion 305 and top panel 312;

FIG. 7 is a three-dimensional view of an exploded solar collector panel 400;

FIGS. 8 a and B are three-dimensional, and three-dimensional sliced, respectively, shortened detail views of a solar vacuum tube 501;

FIG. 9 is a three-dimensional view of a vacuum solar collector 500; and

FIG. 10 is a front schematic view of a heat pipe header heat exchanger system.

For purposes of clarity and brevity, like elements and components will bear the same designations and numbering throughout the Figures.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1A-E are a set of detail, side views of a header assembly 101 showing detail of the header return 110, header inlet 120, heat pipe receiver 130, and header flange 140 components.
The header return 110 transports returning heat transfer fluid 11 within the header assembly 101 (See FIGS. 2, 5 and 9). The header return 110 is W hr wide, H_h high, and L_h long, and may be Ruined by extruding a suitable material such as aluminum. The header return top wall 111, header return inside side wall 112, header return bottom wall 113 and header return side wall 114 have thickness t_hr and faun the return fluid channel 115. The header return inside side wall 112 is located in near proximity to the header inlet inside side wall 124. The space between the header return inside side wall 112 and the header. inlet inside side wall 124 having width W_i, thermally isolates the header return 110 from the header inlet 120. The header return top wall 111 may be coated with a high absorbtivity, low emissivity header return top wall coating 117 to optimize the collection of incident solar energy.
The header inlet 120 transports inlet heat transfer fluid 11 (See FIG. 10) through the header assembly 101 and is W_hi wide, H_h high, L_h long, and may be formed by extruding a suitable material such as aluminum. The header inlet top wall 121, header inlet side wall 122, header inlet bottom wall 123, and header inlet inside side wall 124 are nominally t_hi thick. The header inlet top wall 121 may be coated with a high absorbtivity, low emissivity header inlet top wall coating 127 to optimize the collection of incident solar energy. The interstice of the header inlet 120 contains N heat transfer fins 125 of length L_h positioned perpendicular to the header inlet top wall 121 and header inlet bottom wall 123 that conduct heat transferred from the heat pipe receiver 130 and form N+1 inlet fluid channel 126 components. The number, thickness, length and height H_h, of heat transfer fins 125 establishes the heat transfer efficiency from the heat pipe 202 (See FIGS. 4 and 4 a) through the heat pipe receiver 130 to the heat transfer fluid 11 flowing through the header inlet 120. Each inlet fluid channel 126 is approximately W_hi/(N+1) wide and H_h high. Heat flows from a heat pipe receiver pipe 131 attached to the heat pipe receiver 130 through the heat pipe receiver 130 and into the heat transfer fins 125 and surrounding header inlet top wall 121, header inlet side wall 122, header inlet bottom wall 123 and header inlet inside side wall 124. Heat transfer fluid 11 contacting the surfaces of these items warms as it flows through the header inlet 120.
The heat pipe receiver 130 matingly accepts the condensation end of the heat pipe 205 (See FIGS. 4 and 4 a). The heat pipe receiver pipe 131 has high thermal conductivity and is made of a material similar to the header inlet 120. The heat pipe receiver pipe 131 has length L_hpr, outside radius r_ohpr, inside radius is r_ihpr, diameter 2r_ohpr and wall thickness of r_ohpr−r_ihpr. Heat pipe receiver slots 132 cut in the end of the heat pipe receiver 130 allow the walls to be compressed by the heat pipe clamp 180 (See FIGS. 3, 5 and 9) to secure the heat pipe absorber assembly 201 (See FIG. 4) or heat pipe photovoltaic assembly 221 (See FIG. 4 a) into position.
The header return 110 and header inlet 120 attach to the header flange 140 by weld, solder, braze or other suitable attachment method. The header flange 140 enables the connection of multiple header assembly 101 units or the attachment of the inlet return cap 150 and end cap 160 (FIGS. 3, 5, 9). The header flange 140 provides a wide surface area to contact the gasket 170 material placed between mating connections. The header flange 140 is W_f wide, H_h tall and t_hf thick. The inlet opening 148 has height H_h high and width W_hi and matingly receives the header inlet 120. The return opening 149 has height H_h and width W_hr and matingly receives the header return 110. The header flange 140 is formed by the flange top 141 and flange bottom 143 having approximate dimensions of W_f wide and F tall and by the flange inlet side 142 and flange return side 144 having approximate dimensions of H_f tall and F wide. The divider 145 forms the space between the header inlet 120 and the header return 110 with a minimum area of H_f tall and W_i wide. W_i may be made greater than F to increase the thermal resistance between the header return 110 and the header inlet 120. The header flange attachment holes 147, with the use of suitable fasteners such as bolts and nuts, allow for the connection of one header assembly 101 to another in a serial fashion, or for the attachment of the inlet return cap 150 or the end cap 160 at their respective appropriate locations.
FIGS. 1F-K show an alternate header inlet 120 design showing three-dimensional and front view detail of the header inlet 120 a and side sliced view of the finned heat pipe receiver 131 a components.
The alternate header inlet 120 a design implements finned heat pipe receiver 131 a units that can be fabricated using a metal turning process or casting methods known in the art. The finned heat pipe receiver 131 a has total length L_hpr, height H_h and consists of N concentric fins of equal thickness t_fin and spacing s_fin. The heat pipe absorber assembly 201 (See FIG. 4) has outer radius r_ohp and fits snugly into the finned heat pipe receiver 131 a unit with inner radius r_ihpr. The header inlet 120 a encloses the finned portion of the finned heat pipe receiver 131 a, which has length equal to the width of the header inlet W_hi. For a given r_ihpr, the heat transfer performance may be optimized by adjusting the number of fins, N, the material between the fins, the outer radius of the heat pipe receiver, the fin thickness t_fin, the fin diameter d_fin, and the fin spacing s_fin.
The header inlet 120 a may be fabricated from readily available and inexpensive rectangular pipe and has a header inlet top wall 121 a, header inlet side wall 122 a, header inlet inside side wall 124 a and header inlet bottom wall 123 a. The finned heat pipe receiver 131 a units are housed within the header inlet 120 a and positioned perpendicular to the header inlet top wall 121 a and header inlet bottom wall 123 a. Openings with diameter slightly larger than d_fin drilled through the header inlet inside side wall 124 a and the header inlet side wall 122 a matingly accept the finned heat pipe receiver 131 a units. The finned heat pipe receiver 131 a units may be attached to the header inlet 120 a by weld, adhesive, seals or other methods known in the art. The rectangular header inlet 120 a and more complex finned heat pipe receiver 131 a units reduce the amount of material needed, simplify the manufacturing process and improve thermal performance.
FIGS. 2A and B are a three-dimensional and three-dimensional sliced view of the header assembly 101, respectively.
The header assembly 101 with length L_h, width W_f and height H-f, is formed from a header return 110, a header inlet 120, M heat pipe receiver 130 components and two header flange 140 components. All components are made of the same material, such as aluminum. The inlet fluid channel 126 components and return fluid channel 115 having widths W_hi/N+1 and W_hr, respectively, provide passage for the heat transfer fluid 11 circulating within the header assembly 101. The inlet return thermal gap 128 having width W_i, thermally isolates the header return 110 and the header inlet 120 and may be filled with air or a high thermally resistive substance such as fiber glass or a ceramic should more thermal resistance be desired. The header assembly 101 contains M heat pipe receiver holes 135 with a diameter of 2×r_ohpr, and that extend through the header inlet side wall 122, header inlet inside side wall 124 and N heat transfer fins 125 (FIGS. 1A-E). The heat pipe receiver holes 135 function to matingly receive the heat pipe receiver 130.
FIGS. 3A-G represent a set of three-dimensional and rotated detail views of a header assembly 101 inlet return cap 150, end cap 160, heat pipe clamp 180 and gasket 170 components.
The inlet return cap 150 attaches to the header assembly 101 (FIGS. 2, 5, 9) at one end; while the end cap 160 attaches at the opposite end. The inlet return cap 150 connects the header assembly 101 to the remainder of the system at a single point, and thus, greatly simplifies system installation. The attachment end of the inlet return cap 150 must be at the low point of the system to enable drainback. In normal installation practice the header rises ¼ inch per linear foot to facilitate drain back with the inlet return cap 150 at the low point and the end cap 160 at the high point of the installation. The Inlet return cap 150 accepts heat transfer fluid 11 and distributes it within the header inlet 120 (See FIGS. 1A-E, and 2) through the inlet plenum 153. The inlet 151 having radius r_i, directs heat transfer fluid into the inlet plenum 153. Heat transfer fluid entering through the inlet 151 distributes within the inlet plenum 153 and then enters and flows through the inlet fluid channel 126 components. The inlet plenum 153 is W_hi wide and H_h tall and may be F or greater in length. The inlet 151 diameter of 2r_i must be slightly less than H-hi and the inlet 151 must be placed near the header inlet side wall 122 to allow for drainback and minimization of heat transfer fluid retention within the header inlet 120 when drained. The return 152 having radius r_r, attaches to the return plenum 154 and returns warmed heat transfer fluid 11 from the header assembly 101 back to the system. Warmed heat transfer fluid enters the return plenum 154 and then enters the return 152. The return plenum 154 is H_h high and W_hr wide and may be F or greater in length. The inlet return cap divider 155 isolates the return 152 from the inlet 151 and the divider 145 is W_i in width. The end cap 160 directs heat transfer fluid exiting the header inlet 120 into the header return 110. The end cap 160 flange dimensions are the same as the header flange 140, except that the divider 145 is removed. The end plenum 161 is W_hi+W_hr+W_i wide, H_h high and may be H_h or more in length. Heat transfer fluid 11 exits the header inlet 120, enters the end plenum 161 and then exits the end plenum 161 before entering the header return 110 as it circulates. A gasket 170 is placed between joints when attaching a series of header assembly 101 units, or when attaching an end cap 160 or inlet return cap 150 to a header assembly 101 end. The gasket 170 seals all joints and has dimensions W_f wide, H_f high, t_g thick, and horizontal and vertical sections F wide. The heat pipe clamp 180 secures the heat pipe absorber assembly 201 (See FIGS. 4, 5 and 8) or the heat pipe photovoltaic assembly 221 to the header assembly 101 using concentrated compressive force. The clamp hole 181 allows a threaded fastener, screw or comparable device, to pass through to the clamp threaded hole 182. The clamp threaded hole 182 matingly receives the threaded fastener and when turned closes the compression gap 183. Reducing the compression gap 183 increases retention force between the heat pipe receiver 130 (See FIGS. 1A-E, and 2) and the heat pipe absorber assembly 201 or the heat pipe photovoltaic assembly 221. Heat pipe receiver slots 132 (See FIG. 1A-E) aid the compression process. The inlet return cap 150, end cap 160, and heat pipe clamp 180 components may be formed from the same material or from other suitable materials as the header assembly 101.
FIG. 4 is a set of three-dimensional and sliced expanded detail views of a heat pipe absorber assembly 201.
The heat pipe absorber assembly 201 collects solar radiation over the area W_fin×L_hpe. The heat pipe absorber assembly 201 is made of the same material as the header assembly 101 (See FIGS. 2, 5 and 9), which may be aluminum, an inexpensive aluminum alloy, or other suitable known material. The heat pipe 202 having total length of L hp, inside radius r_ihp, outside radius r_ohp, and wall thickness t_hp=r_ohp−r_ihp efficiently transports heat collected by the absorber fin 203 from the evaporator 204 to the condenser 205 by utilizing the process of evaporation and condensation of the working fluid contained within the heat pipe 202. L_hpe defines the length of the evaporator 204 section and L_hpc defines the length of the condenser 205 section.
The absorber fin 203 collects incident solar energy or heat supplied by the photovoltaic array 222, and heats the evaporator 204 of the heat pipe 202. The absorber fin 203 may be extruded as an integral member of the heat pipe 202 or may be formed from sheet metal and attached to the heat pipe 202 by welding, brazing, soldering, adhesives or other suitable attachment method. The absorber fin 203 has width W_fin and length L_hpe. The evaporator 204 portion of the heat pipe 202 is L_hpe in length and the working fluid within the heat pipe 202 turns to a gas within the evaporator 204 when the absorber fin 203 is heated by the incident solar radiation. Cleaning, evacuating and filling the heat pipe 202 takes place at the end portion of the evaporator 204. The evaporator seal 208 may be formed by pinching off the end of the heat pipe 202, and then permanently closing the pinch off region using a weld, braze, solder, adhesive or other suitable sealing method.
The working fluid within the heat pipe 202 returns to the liquid state within the condenser 205. The condenser 205 portion of the heat pipe 202 has length L_hpc such that L_hpc is slightly greater than L_hpr of the heat pipe receiver 130. Likewise, the outside heat pipe 202 radius r_ohp is slightly less than the heat pipe receiver pipe 131 inside radius r_ihpr. The gap between r_ohp and r_ihpr is filled with thermal paste to efficiently transfer heat from the condenser 205 to the heat pipe receiver 130 and into the header inlet 120, which then transfers heat to the heat transfer fluid 11 flowing through the header inlet 120. The condenser plug 207 seals the condenser 205 end of the heat pipe 202. The plug with radius of r_ihp inserts into the end of the heat pipe 202 and is held in position by weld, solder, braze, adhesive or other suitable attachment method.
A solar coating 206 applied to the sun facing surface of the absorber fin 203 and heat pipe 202 increases absorbtivity and decreases emissivity, which enhances absorption of incident sun light while reducing black body infrared radiation from the heat pipe 202 and absorber fin 203. The performance characteristics of the solar coating 206 may be used to control stagnation temperatures experienced by the heat pipe absorber assembly 201 and header assembly 101 (See FIGS. 2, 5 and 9). As such, with a suitable coating, a panel enclosure assembly 301 (See FIG. 6) may be fabricated from a plastic such as a suitable polycarbonate composition. Should greater operating efficiency be desired, the panel enclosure assembly 301 may be fabricated from glass and metal to withstand higher stagnation temperatures.
FIG. 4 a is a set of three-dimensional and three-dimensional sliced expanded views of a heat pipe photovoltaic assembly 221.
The heat pipe photovoltaic assembly 221 has total length of L_hp. The condenser 205 portion of the photovoltaic assembly including the condenser plug 207 has length L_hpc, while the photovoltaic array 222 portion including the evaporator seal 208 has length L_hpe. A photovoltaic array 222 made of materials known in the art and having approximate dimensions W_fin×L_hpe, attaches to the sun facing side of the absorber fin 203 by means of a suitable thermally conductive adhesive, such as an appropriate thermal epoxy. Solar radiation incident on the photovoltaic array 222 produces electricity while delivering heat to the heat pipe 202 through the absorber fin 203. The photovoltaic array 222 operates at a temperature just slightly above the temperature of the heat transfer fluid 11. The heat pipe 202 transfers the heat to the heat transfer fluid 11 circulating through the header assembly 101. Solar collector panel 400 (See FIG. 7) units fitted with the photovoltaic array 222 components atop the absorber fin 203 components produce electricity while simultaneously collecting thermal energy.
FIG. 5 is a top view of an absorber header assembly 250.
The absorber header assembly 250 consists of a header assembly 101, M heat pipe absorber assembly 201 or M heat pipe photovoltaic assembly 221 units, M heat pipe clamp 180 components and two gasket 170 components, an end cap 160 and an inlet return cap 150. The absorber header assembly is approximately L_h wide and W_hr+W_i+W_hi+L_hpe long. The area available to absorb incident solar energy is W_a×(L_hpe+W_hi+W_hr) and where W_a equals M×W_fin.
FIG. 6 is a set of three-dimensional detail views of an exploded panel enclosure assembly 301 including an enlarged sliced detail view of the frame extrusion 305 and top panel 312.
The panel enclosure assembly 301 includes the top panel assembly 310, bottom panel assembly 320 and the enclosure to header seal 330 components. The top frame 311 having width W_st, length L_st and height H_f, and bottom frame 321 having width W_sb, length L_sb and height H_f, are formed from four frame extrusion 305 sections cut to the desired length and attached to the four sides of the top panel 312 and bottom panel 322, respectively. The frame corners may be sealed and strengthen by welding, soldering, brazing, adhesive, corner bracketing or other method suitable to the application. The top panel 312 may be formed using extruded plastic, sheet plastic, glass or other optically transmissive material. Use of extruded polycarbonate increases strength, minimizes weight, reduces cost and yields improved optical performance over other types of plastic top panels. A plastic top frame 311 may be utilized with a plastic top panel 312. In addition, solar optimized glass may be used to enhance optical performance. The use of glass, however, generally requires a metal top frame 311 which increases the weight of the top panel assembly 310. The bottom panel 322 may be formed from an extruded plastic to minimize weight and cost while maximizing strength and providing a durable weather seal. On plastic material, the top panel top coating 313 provides ultraviolet protection. An anti-reflective coating may be applied to improve optical performance for off perpendicular sun angles on plastic or glass. A top panel bottom coating 314 and a bottom panel top coating 323 may be applied to the bottom surface of the top panel 312 and the top surface of the bottom panel 322, respectively, to reflect infrared radiation emitted by a heat pipe absorber assembly 201 (See FIGS. 4, 5 and 8), a header assembly 101 (See FIGS. 2, 5 and 9), or a heat pipe photovoltaic assembly 221 (See FIG. 5) back to the respective assembly, and thereby increase the collector operating efficiency. A reflective material, such as aluminum foil, may be used as the bottom panel bottom coating 324 to reflect infrared radiation emitted by nearby objects, such as a hot roof, from entering the collector.
The top spacer 315 (not visible in FIG. 6) and bottom spacer 325 vertically position and support the heat pipe absorber assembly 201 or the heat pipe photovoltaic assembly 221. The opening between the spacers must be greater than 2×r_ohp. The header notch 327 opening allows for the header assembly 101 to extend beyond the panel enclosure assembly 301. The enclosure to header seal 330 components seal the joint between the header assembly 101, bottom panel assembly 320 and top panel assembly 310. With the enclosure to header seal 330 components in place the enclosure becomes weather tight in this area, as well as around the full perimeter. The top panel assembly 310 overlaps the bottom panel assembly 320 by a distance H_f−H_p to produce a highly effective weather tight perimeter seal without the use of gaskets. The frame extrusion 305 having width W_f, height H_f and thickness t_f, may be extruded from a plastic, aluminum or other material suitable to the application. A portion of the H_f side wall forms the back side of a U-channel whose opening is slightly greater than H_p. This U-channel forms a weather sealed frame on the four edges of either the top panel 312 or the bottom panel 322.
FIG. 7 is a three-dimensional view of an exploded solar collector panel 400.
The solar collector panel 400 consists of the absorber header assembly 250, the top panel assembly 310, the bottom panel assembly 320 and the enclosure to header seal 330 components. The top panel assembly 310 and bottom panel assembly 320 hold the absorber header assembly 250 in position, but without any direct attachment points. This arrangement allows the absorber header assembly 250 to thermally expand and contract. To make the structure mechanically sound the top panel assembly 310 attaches to the bottom panel assembly 320 around its entire perimeter with the use of suitable and commonly available fasteners.
An alternate embodiment to this design, the photovoltaic array 222 (See FIG. 4 a), utilizes heat pipe photovoltaic assembly 221 (See FIGS. 4 a and 5) units in lieu of heat pipe absorber assembly 201 (See FIGS. 4, 5 and 8) units within the absorber header assembly 250.
FIG. 8 is a set of three-dimensional and three-dimensional sliced, shortened detail views of a solar vacuum tube 501.
The heat pipe absorber assembly 201, bellows 510, seal 520 and glass tube 530 form the solar vacuum tube 501. The solar vacuum tube 501 is L_vt long and D_vt in diameter. The heat pipe 202 condenser 205 (See FIG. 4) portion with length L_hpc of the heat pipe absorber assembly 201 extends past the bellows 510 and plugs into the header assembly 101 (See FIGS. 2, 5 and 9) where it is secured by the heat pipe clamp 180 (See FIGS. 3, 5 and 9). The glass tube 530 is slightly greater than L_hpe in length and encloses the heat pipe 202 evaporator 204 (See FIG. 4) portion of the heat pipe absorber assembly 201. The diameter of the glass tube 530 D_vt is slightly greater than W_fin. The bellows 510 allows for thermal expansion and contraction of the heat pipe absorber assembly 201 both radially and longitudinally without placing any undue force on the glass tube 530. Additionally, the bellows 510 provides the vacuum wall between the heat pipe absorber assembly 201 and the seal 520. Within the bellows attachment region 511 the bellows 510 becomes permanently attached to the heat pipe 202 (See FIG. 4) by means of weld, solder, braze or other known vacuum preserving attachment method to the heat pipe 202 (See FIG. 4). The bellows seal region 512 follows the contour of the seal 520 and the bead 531 and holds the glass tube 530 in place even with no vacuum present within the tube 532. The bead 531 on the bellows end of the glass tube 530 strengthens the tube 532 and serves to increase the area contacting the seal 520. The seal 520 conforms to the shape of the bead 531 and the bellows seal region 512 forming a glass to metal seal 520 between the bellows 510 and the glass tube 530. Once the vacuum is drawn, outside air pressure forces the glass bead 531 to compress the seal 520 against the base of the bellows seal region 512. The tube 532 extends between the bead 531 and the hemispherical glass tube end cap 533. A vacuum is drawn through the vacuum port 534 to vacuum insulate the interior space of the solar vacuum tube 501. With the proper vacuum established, the vacuum port 534 is sealed using known glass sealing methods. An inside coating 536 may be applied to reflect infrared radiation and an anti-reflective outside coating 535 may be applied to improve optical performance for off perpendicular sun angles.
FIG. 9 is a three-dimensional view of a vacuum solar collector 500.
A vacuum solar collector 500 is formed by attaching M solar vacuum tube 501 units to the header assembly 101 using M heat pipe clamp 180 components. Attachment of the inlet return cap 150 and the end cap 160 using gasket 170 components allows for the circulation of heat transfer fluid 11 through the vacuum solar collector 500. The vacuum solar collector 500, having width greater than M×D_vt and length greater than L_vt, collects incident solar energy over the area M×W_fin×L_hpe.
FIG. 10 is a front schematic view of a heat pipe header heat exchanger system.
The system diagram depicts an array of solar collector panel 400 units repeated Q times connected within a closed loop in which heat transfer fluid 11 flows. A pump 620, driven by a pump motor 621, circulates heat transfer fluid 11 through the system. The counterclockwise connection: the pump 620 to inlet 151 of the solar collector panel 400; the header to drainback tank pipe 612 connects the solar collector panel 400 return 152 to the drainback tank 610; the drainback tank to heat exchanger pipe 613 connects the drainback tank 610 to the collector array heat exchanger 619; and the heat exchanger to pump 620 pipe connects the collector array heat exchanger 619 to the pump 620 inlet 151. The pipes may be metal or plastic material. The flow arrow 618 shows the direction of heat transfer fluid flow in the loop. Incident solar radiation heats the heat transfer fluid circulating in the system. This heat transfers to storage tank fluid 652 as the pump 620 moves heat transfer fluid through the collector array heat exchanger 619. Incident solar radiation striking the photovoltaic panel 630 runs the pump motor 621 with the temperature snap switch closed. The temperature snap switch 640 responds to the temperature, T_st, of the storage tank fluid 652. Below T_stmax the switch remains closed. With T_st>T_stmax, the switch opens and shuts off the pump motor 621.
The drainback tank 610 contains sufficient heat transfer fluid to fill the solar collector panel 400, the portion of the pump 620 to header pipe above H_dt, and the portion of the header to drainback tank pipe 612 above H_dt. H_ret represents the maximum distance between the low point in the system and the solar collector panel 400. H_dt represents the height of the heat transfer fluid within the drainback tank 610 with the pump motor 621 off. In practice H_dt may be slightly less than H_ret. The drainback tank 610 may be small, with the minimum tank volume given by W_hi×H_h×(Q×L_h)+W_hr×H_h×(Q×L_h). The above approximation may be used when H_dt almost equals H_ret, meaning that little heat transfer fluid is required to fill the pump 620 to header pipe and the header to drainback tank pipe 612. Placement of the drainback tank 610 in this position protects the system in two very important ways. One, the heat transfer fluid cannot turn to steam and damage system components when the pump 620 is off, fails or the switches break power to the pump 620. When the heat transfer fluid 11 temperature reaches T_stmax, the pump motor 621 stops and the solar collector panel 400 drains into the drainback tank 610. Second, with no fluid in the solar collector panel 400, the heat transfer fluid cannot be damaged when the solar collector panel 400 units stagnate and rise to very high temperatures. Thus, stagnating systems with propylene glycol which can become acidic and corrode pipes are eliminated. The heat transfer fluid fill port 616 is connected to the drainback tank 610. The system is filled with heat transfer fluid through the heat transfer fluid fill port 616 up to the height H_dt. Once filled, the heat transfer fluid fill port 616 valve is closed. The heat transfer fluid drain port 617 is attached to the drainback tank to heat exchanger pipe 613 at the lowest point in the closed loop. Opening the heat transfer fluid drain port 617 drains the system of heat transfer fluid. The drainback tank air space 611 makes drainback possible. The drainback tank air space 611 volume is at a minimum with the pump 620 not running. When the pump motor 621 runs and heat transfer fluid circulates, the air space expands to its maximum volume as the air in the solar collector panel 400 exchanges with heat transfer fluid.
The pump 620, driven by a low wattage DC pump motor 621 supplied with solar energy from the photovoltaic panel 630, circulates heat transfer fluid as indicated by the flow arrow 618. Alternatively, the pump 620 can be driven via utility grid power. With H_dt just slightly less than H_ret, the head requirements placed on the pump 620 are very small. As such, the pump 620 and the pump motor 621 may be very small and inexpensive. A small pump motor 621 may be supplied by a small photovoltaic panel 630. The photovoltaic panel 630 supplies sufficient power to run the pump motor 621 when illuminated by the sun. A typical installation of 2 to 4 panels may utilize a 10 to 20 watt photovoltaic panel 630. The ground terminal of the photovoltaic panel 630 is connected to the ground terminal of the pump motor 621 with a ground wire 622. The photovoltaic panel to snap switch wire 631 connects the positive terminal of the photovoltaic panel 630 to the temperature snap switch 640. The temperature snap switch 640 opens when T_st reaches T_stmax and closes when T_st falls below T_stmax. A temperature snap switch 640 provides an ultra reliable and inexpensive means of temperature control. The temperature snap switch to pump motor wire 641 connects the positive terminal of the photovoltaic panel 630 to the pump motor 621 when the temperature snap switch 640 is closed. In an alternate design, the temperature snap switch 640 can be replaced by a traditional solar panel controller.
The devices housed inside the storage tank 650 include the collector array heat exchanger 619, the temperature snap switch 640, and one or more of: the hot water heat exchanger 660, the space heating heat exchanger 661, and the other heat exchanger 662. The temperature snap switch 640 is replaced by a conventional temperature sensor if a conventional temperature is used. The storage tank 650 additionally contains a large volume of storage tank fluid 652. The storage tank fluid 652 stores heat for routing to other devices through the hot water heat exchanger 660, the space heating heat exchanger 661 and the other heat exchanger 662. The hot water heat exchanger 660 supplies heat to the hot water system, the space heating heat exchanger 661 supplies heat to the space heating system, and the other heat exchanger 662 supplies heat to another system. Other heat exchanger 662 components may be added for any other purpose. The storage tank air space 651 vents to the atmosphere through the atmospheric vent 653 which maintains the pressure within the storage tank 650 to be equal to the atmospheric pressure. The vapor barrier 654 stops the flow of storage tank fluid 652 vapors from escaping to ambient. The combination of the storage tank air space 651, the atmospheric vent 653 and the vapor barrier 654 eliminates any pressure build-up within the storage tank 650. Storage tank fluid 652, typically water, stores heat energy. Solar energy collected by the collector array units heats the storage tank fluid 652 to T_stmax. The hot water heat exchanger 660, the space heating heat exchanger 661, and the other heat exchanger 662 then deliver the stored heat to other systems thermally connected to the storage tank 650. The specified amount of storage tank fluid 652 is added to the storage tank 650 through the storage tank fill port 655 and the valve is then closed when the system is in operation. The storage tank drain port 656 is opened when draining the storage tank 650.
Alternate embodiments for the heat pipe header heat exchanger system can use the vacuum solar collector 500 (See FIG. 9) or the photovoltaic array 222 (See FIG. 4 a) in lieu of the solar collector panel 400.
Some embodiments of the invention may be described as a single header assembly 101 solar heat exchanger comprising:
a header inlet 120 extending the length of the single header assembly 101 for the passage of heat transfer fluid 11 medium, and having a plurality of inlet fluid channel 126 passageways aligned parallel and adjacent to one another, and that extend the length of the header inlet 120, wherein the multiple inlet fluid channel 126 passageways are formed by the longitudinal placement of heat transfer fin 125 components in the interstice of the header inlet 120;
a header return 110 extending the length of the single header assembly 101 and having a single return fluid channel 115 for the passage of heat transfer fluid 11 medium;
an inlet return thermal gap 128 extending the length of the single header assembly 101 and separating the header inlet 120 and the header return 110, wherein thermally isolating the header inlet 120 from the header return 110;
a multiplicity of preformed heat pipe receiver hole 135 openings located on the inside and outside lengthwise perimeter edges of the header inlet 120 and on the heat transfer fin 125 components; and that the heat pipe receiver hole 135 openings are aligned vertically between the elements within the header inlet 120;
a heat pipe receiver 130 that mates to the header inlet 120 by vertically crossing the inlet fluid channel 126 passageways through aligned heat pipe receiver hole 135 openings;
a duality of preformed header flange 140 components attached to the header inlet 120 and header return 110 on each end of said single header assembly 101;
and that the header inlet 120 resides beneath the header return 110 offset at a slight inclination to aid fluid flow, wherein the heat transfer fluid 11 medium flows in one direction through the header inlet 120 and flows in the reverse direction through the header return 110.
In some embodiments, the header inlet 120 is interchangeable with an alternate header inlet 120 a design comprising:
a plurality of equally spaced and longitudinally oriented finned heat pipe receiver 131 a units located in the interstice of the header inlet 120 a, wherein placement across the inlet fluid channel 126 passageway allows for thermal contact and fluid flow of the heat transfer medium, and that the concentric preformed fins on the finned heat pipe receiver 131 a enable fluid passage through the opening space s_fin.
In some embodiments, the heat transfer fluid 11 medium circulates in an upward horseshoe direction at one end of said single header assembly 101 from the inlet fluid channel 126 to the return fluid channel 115, wherein the fluid flow loop is molded by:
an inlet return cap 150 attached at one end of the single header assembly 101 and having an inlet plenum 153 and a return plenum 154, wherein the inlet plenum 153 and the return plenum 154 cap the header inlet 120 and the header return 110, respectively, and also that the inlet 151 and return 152 openings of predetermined radius and position are attached and radially extruded from the exterior top surface of the inlet plenum 153 and return plenum 154, respectively;
an end cap 160 attached at one end of the single header assembly 101, wherein the end cap 160 attachment end opposes the inlet return cap 150 attachment end, and that the end cap 160 caps the outside perimeter of the combined header inlet 120 and header return 110, and also that the end cap 160 end plenum 161 facilitates the backend structure of the horseshoe fluid flow loop; and
a gasket 170 element on each end of the single header assembly 101; wherein each gasket 170 element seals the joints between the single header assembly 101 and any end cap 160, inlet return cap 150 or other single header assembly 101, and that the gasket 170 elements are preformed to fit their respective attachment openings.
Some embodiments of the single header assembly 101 may support a series connection structure by attachment means between adjacent header flange 140 elements.
Some embodiments of the invention may be described as a heat pipe absorber assembly 201 comprising:
a unique constant diameter heat pipe 202 design that operates using conventional condenser and evaporator regions;
an absorber fin of rectangular dimension, and having a lengthwise centered half-moon arch with radius slightly greater than that of the heat pipe 202, wherein said absorber fin attaches to the evaporator portion of the heat pipe 202.
Some embodiments of the invention may be described as an absorber header assembly 250 Ruined by at least one heat pipe absorber assembly 201 attaching to the single header assembly 101 described above. A connection junction may comprise a heat pipe clamp 180 device, with a hollow cylindrical opening that encircles the heat pipe receiver 130, wherein one or more heat pipe absorber assembly 201 units can be secured to the single header assembly 101 using concentrated compressive force.
Some embodiments of the invention may be described as a panel enclosure assembly 301 comprising:
a top panel assembly 310 having dimensions slightly greater than the dimensions of the bottom panel assembly 320, wherein the top panel assembly 310 matingly receives the bottom panel assembly 320;
a top frame 311 of rectangular dimension, wherein the top frame 311 surrounds the preformed top panel 312, and thereby, forms the top panel assembly 310;
a bottom frame 321 of rectangular dimension, wherein the bottom frame 321 surrounds the preformed bottom panel 322, and thereby, forms the bottom panel assembly 320;
an enclosure to header seal 330 at each top spacer 315 and bottom spacer 325 assembled opening locations, wherein sealing the joints between the header assembly 101, top panel assembly 310 and bottom panel assembly 320;
a preformed top spacer 315 opening and bottom spacer 325 opening located on the top end of each lengthwise perimeter top frame 311 and bottom frame 321 sides, respectively, and that the top spacer 315 openings and bottom spacer 325 openings are aligned when assembled, wherein providing structural positioning for an absorber header assembly 250 unit.
Some embodiments of the invention may be described as a heat pipe photovoltaic assembly 221 comprising a heat pipe absorber assembly 201, wherein a photovoltaic array of existing art attaches to the sun facing side of the absorber fin 203, and that said photovoltaic array 222 produces electricity while concurrently transferring thermal energy through the absorber fin 203 to the heat pipe 202.
Some embodiments of the invention may be described as a photovoltaic array 222 formed by at least one heat pipe photovoltaic assembly 221 as described above, attaching to the single header assembly 101 described above.
Some embodiments of the invention may be described as a solar vacuum tube 501 comprising:
a heat pipe absorber assembly 201 that forms the central axis of the solar vacuum tube 501;
a glass tube 530 concentrically surrounding the evaporator 204 portion of the heat pipe absorber assembly 201;
a bead 531 located on the glass tube 530 end positioned at the evaporator to condenser junction of the heat pipe absorber assembly 201, wherein forming a supporting circular lip;
a bellows 510, made of metal material, wherein providing radial and longitudinal expansion and contraction means for the heat pipe absorber assembly 201, and that said bellows 510 makes a bottle-cap style attachment to the bead 531 forming the bellows seal region 512, wherein a seal 520 conforming to the shape of the bead 531 is positioned between the bellows seal region 512 and the bead 531, wherein foaming a glass to metal seal, and also that said bellows 510 concentrically surrounds and suitably attaches to the axial heat pipe 202 at the bellows attachment region 511; and
a hemispherical glass tube end cap 533 attaches to the glass tube 530 end opposite the bellows 510 attachment end, and that said end cap 533 is equipped with an extruding vacuum port 534, wherein enabling vacuum insulation of the interior space between the heat pipe absorber assembly 201 and glass tube 530.
Some embodiments of the invention may be described as a vacuum solar collector 500 formed by at least one solar vacuum tube 501 attaching to the single header assembly 101.
Some embodiments of the invention may be described as a solar collector system, comprising:
heat transfer fluid 11 flowing through a closed loop solar heating system;
at least one panel enclosure assembly 301; or photovoltaic array 222; or vacuum solar collector 500 connected in the closed loop system;
a drainback tank 610 of predetermined location and height, wherein the height of the heat transfer fluid 11 within the drainback tank 610 with the pump off is H_t; and that the drainback tank 610 volume is small, wherein the volume is pi*(r_h)̂2*l_h with r_h representing the inside radius of the header pipe and l_h representing the length of the header pipe plus piping to the level of the drainback tank 610 on both sides of the header pipe; and that placement of the drainback tank 610 restricts vaporization of the heat transfer fluid 11 and prevents damage to the system components;
a drainback tank air space 611 of predetermined volume, wherein the volume is at a minimum with the pump 620 off and volume expands to a maximum with the pump 620 running and heat transfer fluid 11 circulating; and that the drainback tank air space 611 corresponds nearly exactly to the space in the header pipe, header to drainback tank pipe 612, and pump to header pipe 615 filled by heat transfer fluid 11 with the pump motor 621 energized and driving the pump 620;
a header pipe of predetermined location above the drainback tank 610, wherein H_h is a predetermined maximum distance between the low point in the system and the header pipe; and that in practice, the height of the heat transfer fluid 11 within the drainback tank 610 H_t may be slightly less than the height of the header pipe;
a pump 620 and a pump motor 621, wherein the pump motor 621 is driven by photovoltaic panel 630 solar energy and the pump 620 circulates heat transfer fluid 11 through the system; and that when the heat transfer fluid 11 reaches a maximum predetermined temperature T_stmax, the pump motor 621 stops and the heat transfer fluid 11 in the header pipe drains into the drainback tank 610, wherein preventing stagnation damage due to high temperatures to the heat transfer fluid 11; and
a temperature snap switch 640 located within a storage tank 650, wherein providing temperature control to the system; and that the temperature snap switch 640 opens when the heat transfer fluid 11 reaches the predetermined maximum temperature T_stmax and closes when the heat transfer fluid 11 temperature drops below T_stmax.
Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the above examples for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention.
Although this invention has been described above with reference to particular means, materials and embodiments, it is to be understood that the invention is not limited to these disclosed particulars, but extends instead to all equivalents within the scope of the following claims. Having thus described the invention, what is desired to be protected by Letters Patent is presented in the subsequently appended claims.

Claims

1. A solar heat pipe heat exchanger, comprising:

a single header with a length and two ends, said header comprising an inlet with an inlet interior space extending the length of the header for inlet passage of heat transfer fluid;

the single header also comprising a return extending the length of the header for outlet passage of heat transfer fluid, the return being separated from the inlet by a thermal gap for the length of the header, and the return being secured to the inlet by a flange at each end of the header; and,

the inlet having a heat pipe receiver extending into the inlet interior space, the heat pipe receiver being adapted to matingly accept the condensation end of a pipe.

2. The heat exchanger of claim 1 wherein the inlet interior space comprises a plurality of passageways formed by heat transfer fins.

3. The heat exchanger of claim 1 wherein the heat pipe receiver is a finned tube.

4. The heat exchanger of claim 2 wherein the heat pipe receiver contacts the heat transfer fins.