Solar heat pipe heat exchanger

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[0001]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[0002]1. Field of the Invention[0003]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 o...

AI Technical Summary

Benefits of technology

[0007]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.

[0011]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.

[0018]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.

[0020]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.

[0021]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.

[0023]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.

Problems solved by technology

Simple to construct solar heat pipe designs currently on the market fail to optimally mate a constant diameter heat pipe to the header assembly.

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.

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.

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.

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.

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.

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