GB2064754A

GB2064754A - Solar heater

Info

Publication number: GB2064754A
Application number: GB8031794A
Authority: GB
Original assignee: Modine Manufacturing Co
Current assignee: Modine Manufacturing Co
Priority date: 1979-11-29
Filing date: 1980-10-02
Publication date: 1981-06-17
Also published as: IT1127915B; IT8050067A0; JPS5685660A; DE3041750A1; FR2470940A1

Abstract

A solar heater comprises an aluminum plate (11) adapted to receive heat from solar rays, a plurality of spaced tubes (12) secured to the plate and metallurgical bonds such as brazing joining the tubes to the aluminum plate in heat transfer relationship. As shown, the tubes extend between two headers (13, 14) and are engaged by tabs (18) which are integral with the plate. <IMAGE>

Description

SPECIFICATION Solar heat collecting system One of the features of the invention is to provide a solar heat collecting system in which an aluminum plate is exposed to the solar rays to absorb heat therefrom and spaced tubes of ferritic stainless steel are secured to the tubes by metallurgical bonds so as to have greater heat transfer between the plate and the tubes and so as to reinforce the plate. Then, a liquid such as water is directed through the tubes from a source such as a manifold to absorb heat after which the heated liquid is conveyed to a location for extracting the heat from the liquid.

Another feature of the invention is to provide spaced tabs that are integral with the plate and embracing the tubes for retaining the tubes in position relative to the plate and for providing heat transfer paths between the plate and the tubes in addition to the metallurgical bond which provides the main heat transfer path.

Figure 1 is a perspective view of a system embodying the invention.

Figure 2 is a section taken substantially along the line 2-2 of Fig. 1.

The solar heat collecting system 10 comprises an aluminum plate 11 that has bonded thereto spaced tubes 1 2 that extend in parallel relationship between an inlet manifold 1 3 and an outlet manifold 14 so that a heat transfer liquid such as water may flow into the manifold 1 3 as indicated by the arrow 15, through the spaced tubes 1 2 and from the outlet manifold 14 as indicated by the arrow 16.

The tubes 1 2 are attached to the plate 11 by metallurgical bonds such as the brazing 1 7. In order to properly locate the tubes 12 on the plate 11 preparatory to brazing and to provide additional heat transfer paths there are provided spaced tabs 1 8 or fingers struck from the plate 11 to leave openings 1 9 and tightly embracing the tubes on the side thereof opposite the plate 11. The brazing 1 7 therefore secures the tubes 1 2 to the plate 11 and the tabs 18 to the tubes 1 2.

With this arrangement the tubes 1 2 not only provide paths for the heat transfer and heat conveying liquid 1 5 and 1 6 but also strengthen the system 10.

The aluminum of the plate 11 provides a low density, low cost and efficient collector plate for collecting heat from the sun's rays.

The tubes 1 2 and manifolds 1 3 and 14 comprise a ferritic stainless steel, for example 409, 439 or 18Cr-2 MO. This stainless steel construction means that the heat transfer liquid 1 5-1 6 may be corrosive water which contains chlorine or other strong chemicals without destruction and without damage to the stainless steel parts.

The curved tabs or fingers 18 not only strengthen the assembly and provide additional heat transfer paths but also form continuous channels between the tabs and the plate into which the tubes can be inserted in assembling the unit.

The stainless steel of the manifolds 1 3 and 14 and tubes 1 2 may be welded at the joints between the tubes and the manifolds. This welding may be of any of the usual methods but preferably is by an inert gas-shielded electric arc that travels at high speed over the joints where the welding is to be produced thereby converting the metal to a molten state which when cooled comprises the joint. The welds are thereby made without the use of any added metal such as a welding rod and are protected from contamination by the inert gas shield, which inert gas may be argon.

In this type of welding the only metal supplied is from the metal parts themselves at their contacting areas and the molten metal is protected by the inert gas. A high frequency high potential source is applied between the electrode and work piece and ionizes the gaseous medium, for example argon, surrounding the electrode and the joint. Simultaneously a direct current of low potential is applied between the same electrode and the work piece comprising the heat exchanger parts. When the high potential high frequency source ionizes the gas an arc or stream of electrons caused by the presence of the direct current low potential source flows between the electrode (not shown) and the work thereby causing the welding work to be heated to the molten welding temperature at the joint.

The preferred stainless steel is that which contains chromium in the amount of at least 12% such as from 12-32% although other types of stainless alloys may be used. Chromium containing stainless is preferred because the chromium is a strong promoter of hardenability as it decreases the critical cooling rate of steel and the chromium containing steel alloy has good creep particularly at high temperatures and pressures. Because of the stainless steel weldment construction the unit is very strong and thus can be self-supporting.

Having described my invention as related to the embodiment shown in the accompanying drawings, it is my intention that the invention be not limited by any of the details of description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the appended claims.

1. A solar heat collecting system, comprising: a plate comprising aluminum adapted to receive heat from solar rays; a plurality of spaced tubes comprising ferritic stainless steel; metallurgical bonds joining said ferritic tubes to said aluminum plate in heat transfer

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Solar heat collecting system One of the features of the invention is to provide a solar heat collecting system in which an aluminum plate is exposed to the solar rays to absorb heat therefrom and spaced tubes of ferritic stainless steel are secured to the tubes by metallurgical bonds so as to have greater heat transfer between the plate and the tubes and so as to reinforce the plate. Then, a liquid such as water is directed through the tubes from a source such as a manifold to absorb heat after which the heated liquid is conveyed to a location for extracting the heat from the liquid. Another feature of the invention is to provide spaced tabs that are integral with the plate and embracing the tubes for retaining the tubes in position relative to the plate and for providing heat transfer paths between the plate and the tubes in addition to the metallurgical bond which provides the main heat transfer path. Figure 1 is a perspective view of a system embodying the invention. Figure 2 is a section taken substantially along the line 2-2 of Fig. 1. The solar heat collecting system 10 comprises an aluminum plate 11 that has bonded thereto spaced tubes 1 2 that extend in parallel relationship between an inlet manifold 1 3 and an outlet manifold 14 so that a heat transfer liquid such as water may flow into the manifold 1 3 as indicated by the arrow 15, through the spaced tubes 1 2 and from the outlet manifold 14 as indicated by the arrow 16. The tubes 1 2 are attached to the plate 11 by metallurgical bonds such as the brazing 1 7. In order to properly locate the tubes 12 on the plate 11 preparatory to brazing and to provide additional heat transfer paths there are provided spaced tabs 1 8 or fingers struck from the plate 11 to leave openings 1 9 and tightly embracing the tubes on the side thereof opposite the plate 11. The brazing 1 7 therefore secures the tubes 1 2 to the plate 11 and the tabs 18 to the tubes 1 2. With this arrangement the tubes 1 2 not only provide paths for the heat transfer and heat conveying liquid 1 5 and 1 6 but also strengthen the system 10. The aluminum of the plate 11 provides a low density, low cost and efficient collector plate for collecting heat from the sun's rays. The tubes 1 2 and manifolds 1 3 and 14 comprise a ferritic stainless steel, for example 409, 439 or 18Cr-2 MO. This stainless steel construction means that the heat transfer liquid 1 5-1 6 may be corrosive water which contains chlorine or other strong chemicals without destruction and without damage to the stainless steel parts. The curved tabs or fingers 18 not only strengthen the assembly and provide additional heat transfer paths but also form continuous channels between the tabs and the plate into which the tubes can be inserted in assembling the unit. The stainless steel of the manifolds 1 3 and 14 and tubes 1 2 may be welded at the joints between the tubes and the manifolds. This welding may be of any of the usual methods but preferably is by an inert gas-shielded electric arc that travels at high speed over the joints where the welding is to be produced thereby converting the metal to a molten state which when cooled comprises the joint. The welds are thereby made without the use of any added metal such as a welding rod and are protected from contamination by the inert gas shield, which inert gas may be argon. In this type of welding the only metal supplied is from the metal parts themselves at their contacting areas and the molten metal is protected by the inert gas. A high frequency high potential source is applied between the electrode and work piece and ionizes the gaseous medium, for example argon, surrounding the electrode and the joint. Simultaneously a direct current of low potential is applied between the same electrode and the work piece comprising the heat exchanger parts. When the high potential high frequency source ionizes the gas an arc or stream of electrons caused by the presence of the direct current low potential source flows between the electrode (not shown) and the work thereby causing the welding work to be heated to the molten welding temperature at the joint. The preferred stainless steel is that which contains chromium in the amount of at least 12% such as from 12-32% although other types of stainless alloys may be used. Chromium containing stainless is preferred because the chromium is a strong promoter of hardenability as it decreases the critical cooling rate of steel and the chromium containing steel alloy has good creep particularly at high temperatures and pressures. Because of the stainless steel weldment construction the unit is very strong and thus can be self-supporting. Having described my invention as related to the embodiment shown in the accompanying drawings, it is my intention that the invention be not limited by any of the details of description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the appended claims. CLAIMS

1. A solar heat collecting system, comprising: a plate comprising aluminum adapted to receive heat from solar rays; a plurality of spaced tubes comprising ferritic stainless steel; metallurgical bonds joining said ferritic tubes to said aluminum plate in heat transfer relationship; and means for directing a heat absorbing liquid through said tubes to absorb heat and to a location for extracting said heat from said liquid.

2. The solar heat collecting system of claim 1 wherein spaced tabs are provided integral with said plate and embracing said tubes for retaining said tubes in position relative to said plate and for providing heat transfer paths between said plate and said tubes.

3. The solar heat collecting system of claim 1 wherein said tubes are united with said plate by brazing.

4. The solar heat collecting system of claim 1 wherein spaced tabs are provided integral with said plate and embracing said tubes for retaining said tubes in position relative to said plate and for providing heat transfer paths between said plate and said tubes and brazing uniting said tubes, tabs and plate.

5. The solar heat collecting system of claim 1 wherein said tubes are arranged parallel-to each other and spaced manifolds are provided connected to opposite ends of said tubes for directing said liquid in parallel flow from one manifold through said tubes and to an opposite manifold.

6. The solar heat collecting system of claim 5 wherein said tubes and said manifolds are ferritic stainless steel and said tubes and manifolds are provided with welds joining said tubes and manifolds, the weld metal of said welds being essentially a solid, previously molten, metal from adjacent portions of said stainless steel tubes and manifolds.

7. The solar heat collecting system of claim 6 wherein spaced tabs are provided integral with said plate and embracing said tubes for retaining said tubes in position relative to said plate and for providing heat transfer paths between said plate and said tubes.

8. The solar heat collecting system of claim 6 wherein said tubes are united with said plate by brazing.

9. The solar heat collecting system of claim 6 wherein spaced tabs are provided integral with said plate and embracing said tubes for retaining said tubes in position relative to said plate and for providing heat transfer paths between said plate and said tubes and brazing uniting said tubes, tabs and plate.