Field of the Invention

This invention relates in general to solar heating system, and more particularly to solar heating system having a solar exchanger. Background of the Invention

Solar thermal collectors are widely used to collect energy in areas where sunlight is abundant. In the market various types of solar collectors are available, and the collected solar energy is transferred to heat exchanger for other purposes such as heating per se or heating of other devices. Available heat exchangers are made of vertically arranged heat pipes that are welded in such a way that the heat exchanger fluid flows through within the pipes. Cost in metal for making of these pipes is huge and these pipes are not durable due to various factors. In these conventional heat exchangers, heating plates are used as an alternative, but the mounting and arrangement of the heating plates are too complicated and laborious. In other words, the assembly of the heating plates is of high cost and the heating plates are prone to damage in the course of assembly.

U.S. Pat. No. 4,326,583 discloses a heat exchanger consists of a metal tube with a metal plate welded to it. To prevent damages, the regions of the metal plate on both sides of the weld seam are provided with corrugations that run substantially transverse to the longitudinal direction of the tube. These corrugations are adapted to prevent the occurrence of distortions but the arrangement is not really satisfy in term of function. US Patent Publication No. 20090101319 discloses heat exchanger with varying cross sectional area of conduits. The heat exchange process involves heat exchange that employs heat exchangers where the process material flows over a heat transfer surface in which a process material passes through the process conduit of a heat exchanger wherein the desired velocity profile of the process material passing through the process conduit is achieved by varying the cross sectional area of the process conduit in three or more locations along the path length of the process conduit which allows better regulation of heating or cooling within the system which, for some processes, will result in improved temperature control.

US Patent No. 4,562,828 discloses a solar water heating system which comprises: (a) solar collector means containing a fluid flow path therein; (b) water storage means for containing a reservoir of water and adapted to provide water to an external circuit; (c) a heat transfer circuit coupled to said water storage means; (d) heat exchanger means including a top surface and having a first input port located at said top surface and a first output port, both of said first ports being coupled to the fluid flow path of the collector means; and (e) vacuum break means located within the heat exchanger means proximate to the first input port for supplying air to the solar collector means upon the cessation of flow in the fluid flow path. The heat exchanger means provides a reservoir therein for at least a portion of the fluid contained in the flow path, and the heat exchanger means further includes a second input port and a second output port, each of the second ports being located at the top surface and being coupled to the heat transfer circuit with at least a portion of the heat transfer circuit residing within the reservoir in the heat exchanger means. The first input port and the second output port are being coaxially located on the heat exchanger means to enhance heat transfer between the fluid circuits. Summary of the Invention

One aspect of the present invention is to provide a solar heat exchanger comprises a housing; a plurality of heat absorbing tube parallely arranged across the housing, wherein each heat absorbing tube is hollow at the center defining a passage, each heat absorbing tube comprises an outer tube and an inner tube, wherein working medium is filled and sealed in a space between the outer tube and the inner tube; and a top and a bottom fluid compartments defining at two sides of the housing, wherein the two fluid compartments are in fluid communication through the plurality of heat absorbing pipes at the end thereof.

Operationally, water flows into one compartment through a water inlet, passes through the passages of the heat absorbing tubes and enters into the other compartment at a higher temperature.

In accordance with one aspect of the present invention, there is provided a solar heat exchanger having non-phase change axially arranged heat absorbing tubes, wherein the heat absorbing tubes are entirely mounted vertically or at any optional angle to ensure that beam of the sunlight is focused onto the heat absorbing tubes such that the heat exchanger provides maximum working efficiency.

Conveniently, the present invention provides a solar heat exchanger having non-phase change heat absorbing tubes, wherein the heat absorbing tubes are mounted vertically in at least one row and are at any optional angle to the bottom plate and the top plate.

Preferably, the present invention provides a solar heat exchanger having non-phase change heat transfer device. In accordance with the present invention, the heat exchanger has a high efficiency in absorbing solar energy, and provides high heating efficiency in heating chilled water, i.e., the heat exchanger provides high solar energy exchange efficiency, and has high heating density.

The heat exchanger in accordance with the present invention is to provide a safe and reliable device, which has a rigid configuration, and is a pressure resistance and eco-friendly device.

The advantages of the solar heat exchanger in accordance with the present invention are that it absorbs heat from the sun evenly, and it is quick to provide a fast and high efficiency in transferring heat to chilled water such that the temperature of chilled water increases or the chilled water is boiled.

The heat exchanger of the present invention also has the uniqueness of transferring heat in axial direction, and provides a continuous stream of steam. The exchange of heat transfer can be operated at a lower temperature, which ensures that very little heat loss to the atmosphere due to radiation.

In accordance with the present invention, the size of the exchanger is small, and light weight, which is reliable in use.

Brief Description of the Drawings

A detailed description of the preferred embodiment is provided herein below with reference to the following drawings, in which like numbers refer to like elements. The drawings are: FIG. 1 illustrates a solar heat exchanger in accordance with an embodiment of the present invention;

FIG. 2 A is a schematic sectional view of the solar heat exchanger of FIG. 1 of the present invention; FIG. 2B illustrates a cross sectional view a heat absorbing tube of the solar heat exchanger of FIG. 1 in accordance with one embodiment of the present invention;

FIG. 3 is a perspective schematic view of a solar collecting system in accordance with one embodiment of the present invention; and

FIG. 4 illustrates an application of the heat exchanger in accordance with an alternative embodiment of the present invention.

Detailed Description

In line with the above summary, the following description of a number of specific and alternative embodiments are provided to understand the inventive features of the present invention. It shall be apparent to one skilled in the art, however that this invention may be practiced without such specific details. Some of the details may not be described at length so as not to obscure the invention. For ease of reference, common reference numerals will be used throughout the figures when referring to the same or similar features common to the figures.

FIG. 1 illustrates a schematic view of a solar heat exchanger 10 in accordance with an embodiment of the present invention. The heat exchanger 10 is adapted for heating up fluid, such as water, utilizing solar energy. The heat exchanger 10 comprises a housing 15, a plurality of heat absorbing tubes 11 and two fluid compartments 20, 30. The housing 15 is a shallow casing with at least one major side opened. The two fluid compartments 20 and 30 are defined at two opposing sides of the housing 15 respectively. Between the two fluid compartments 20 and 30, the plurality of heat absorbing tubes 11 are arranged parallely across the housing 15. The heat absorbing tubes 11 are exposed through the opened side of the housing 15. Each of the heat absorbing tubes 11 is secured at the ends thereof such that the two compartments 20 and 30 are connected through the plurality of heat absorbing tubes 11. The bottom compartment 20 is provided with a water inlet 22 and the top compartment 30 is provided with a water outlet 32.

In the present embodiment, structure of the heat absorbing pipes 11 is identical to each other but configuration or orientation of the heat absorbing tubes 11 within the heat exchanger 10 can be varied as an alternative embodiment of the present invention. For instance, the heat absorbing tubes 11 can be arranged with a specific angle to the top and bottom compartments 20, 30.

FIG. 2 A illustrates a sectional view of the heat exchanger 10 of FIG. 1. The top and bottom compartments 20 and 30 have cavities for containing water. Water is supplied through the water inlet 22 into the bottom compartment 20 and leaves the top compartment 30 through the water outlet 32. Each of the heat absorbing tubes 11 comprises an outer tube 12 surrounding an inner tube 13 with space defining there between. The space is filled with heat transfer medium 14 (also known as working medium) that is sealed between the outer tube 12 and the inner tube 13. Preferably, the heat transfer medium 14 is fluid medium. Accordingly, the heat absorbing tube 11 with the heat transfer medium 14 sealed within the outer tube 12 and the inner tube 13 forms a heat transfer device, such as heat pipe.

Generally, the heat absorbing tube 11 may be configured according to any heat transfer phenomenon. More preferably, the heat transfer medium 14 is fully filled and sealed within the outer tube 12 and the inner tube 13 at a predetermined temperature and pressure according to the desired working temperature to form a heat transfer device. Further, it is required that the heat absorbing tubes 11 are configured to transfer the heat from the outer tube 12, to the working medium 14 to the inner tube 13, i.e. axial heat transfer. Yet, it may be desired that each heat absorbing tube 1 1 has a surface coating that prevents or reduces heat lost through radiations.

In addition, it may also be desired the housing 10 is made of a thermally insulated material to preserve the collected heat.

When the heat absorbing tubes 11 are in placed on the heat exchanger 10, the inner tube 13 of each heat absorbing tubes 11 forms a fluid passage between the top and the bottom compartments 20 and 30. Accordingly, water supplies through the water inlet 22 can flow into the bottom compartment 20, passes through the inner tube 13 of each heat absorbing tube 11, enters the top compartment 30 and exits the heat exchanger 10 through the water outlet 32.

In FIGs. 1 and 2A, six heat absorbing tubes 11 are provided. But it is understood to the skilled person that the heat absorbing tubes shall not be limited to only six. The illustrative heat absorbing tubes in the figures are for the purpose of easy understanding of the invention and should not be interpreted as a limitation. Operationally, the heat exchanger 10 is arranged with the heat absorbing tubes 11 exposing to solar energy source. Water at a cooler temperature from a water supply, such as a water tap, enters into the heat exchanger 10 via the water inlet 22 on the bottom

compartment 20. Since the heat absorbing tubes 11 are connected with the bottom

compartment 20, water flows into the heat absorbing tubes 11 via the passage of the inner tube 13. As the water flowing through the heat absorbing tubes 11, the solar thermal energy exposed on the outer tube 12 is transferred to the inner tube 13 through the heat transfer medium 14 to heat up the water flowing there through. Accordingly, water flows into the top compartment 30 at a higher temperature, or in some case, vaporized form. FIG. 2B is a cross sectional view of the heat absorbing tube 11 in accordance with one embodiment of the present invention. The heat absorbing tube 11 is configured in a manner that the inner tube 13 is concentrically mounted within the outer tube 12 with a sealed space 16 defined in between. The sealed space 16 is adapted for containing working medium 17 that functioned as a heat transfer medium for the heat absorbing tube 11.

Preferably, when the working medium 17 is being filled into the sealed space 16, it is filled at a predetermined temperature and a predetermined pressure. The predetermined temperature and the predetermined pressure are determined in accordance with a desired working temperature of the heat absorbing tube 11. Optionally, the outer surface of the outer tube 12 may be coated with a layer of coating 18. Operationally, as the sunlight illuminates on the heat absorbing tube 11, the heat absorbing tube 11 absorbs the thermal energy and transfers it axially to the inner part of the tube 11 to heat up water that passed through the passage. In an alternative embodiment, it is possible that the heat absorbing tubes 1 1 are arranged in two or more rows. For example, in addition to the row of heat absorbing tubes 11 in FIG. 1, the housing 15 can be made slightly deeper for mounting a second row or rear row bundle in a similar matter as the first or front row. The second or more rows of heat absorbing pipes offers a better efficiency of absorbing solar energy as well as heating up a larger volume of water as the water flow increases.

The advantages of the solar heat exchanger 10 are that it absorbs heat from the sun evenly, and efficiently transfers the absorbed heat to heat up the cold water. It may even boil the water immediately as the water passes through the passage of the heat absorbing tubes.

In accordance with the present invention, the size of the heat exchanger is small, and light weight and it is reliable in use. For example, when a 10m diameter parabolic concentrator is used to collect solar heat energy onto the heat exchanger 10, it can provide about 36 W of heat energy. In this configuration, a 60cm by 40cm heat exchanger with two rows of heat absorbing tubes mounted therein can be used for heating at least 10 tons of water to boil in about 15 minutes with continuous stream of water supply.

Other variations and modifications of the invention are possible. For example, there are more units of heat absorbing tubes being used and other configurations of heat absorbing tubes.

FIG. 3 illustrates a solar heating system 40 in accordance with one embodiment of the present invention. The solar heating system 40 comprises a ζ> arabolic heat concentrator 42 and a solar heat exchanger 45. The parabolic concentrator 42 is a parabolic dish with reflecting surface that concentrates incoming sun light at a focal point or focal area. The solar heat exchanger 45 has a same or substantially the same configuration as the solar heat exchanger 10 of the present invention. It is mounted at the focal point or focal area for receiving the solar energy reflected from the parabolic concentrator 42. Typically, the working temperature at the focal point or focal area may go beyond 1000 degree C, and the heat capacity transfer may be more than lOOW/cm ² . Further, the heat exchanger 42 may heat water up to 1 10 degree C at 1.5atm.

This type of solar heat exchanger achieves the objective of high efficiency heat transfer and the longevity of the exchanger is greatly improved.

FIG. 4 illustrates an application of the heat exchanger 10 in accordance with another embodiment of the present invention. The heat exchanger 10 can be used without any solar thermal collector. In this embodiment, the heat exchanger 10 is used directly to absorb solar heat. The heat exchanger 10 can be mounted at a sidewall of a building 50, or any part, such as rooftop of the building 50 for absorbing solar heat.

While one or more embodiments of this invention has (have) been illustrated in the accompanying drawings and described above, it will be evident to those skilled in the art that changes and modifications may be made therein without departing from the essence of this invention. All such modifications or variations are believed to be within the sphere and scope of the invention as defined by the claims appended hereto.