Heat exchangers and solar heating

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Drawings

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like, but such securement can take place if preferred or

HEAT EXCHANGERS AND SOLAR HEATING if considered desirable for certain uses of the invention, such as where it may be necessary or desirable for the

This invention relates to heat exchangers and solar fluid ducts 4 formed between the two members 1 and 2 heating and more particularly relates to the construc- 5 and the points of contact 3 to be sealed from each other. tion of fluid containers and the manner in which fluid The preferred non-welded friction fit arrangement of ducts may be formed within such containers in the pro the outer and inner tubular members 1 and 2 has an vision of heat exchange units which have particular added advantage of permitting expansion and contrac application for the heating of water by solar heat. tion of the members 1 and 2 under temperature variation An object of this invention is to provide a simple but 10 and without either of the members 1 and 2 being placed effective means for providing a heat exchanger and under undue stress likely to cause joint failure. fluid duct system therein whereby such exchanger can In the present preferred application of the invention be manufactured and sold at relatively low cost whilst to solar water heating, the provided unit is intended to at the same time the heat exchanger provides broad work on a thermo-siphon convection system for water areas of contact for fluid within the ducts formed to 15 contained within the outer and inner tubular members 1 thus provide a means for efficient heat exchange be and 2, with the main body of water being accommo tween the heat exchanger and the fluid passed there dated within the area 5 defined by the inner member 2. through. The inner member 2 can either terminate short of the Other and more particular objects and advantages of ends 6 of the outer member 1 to provide communication the invention will become apparent from the ensuing 20 between the ducts 4 and the main inner area 5, or the description. inner member 2 can extend to the ends of the outer According to the first aspect of this invention there member 1 and communication can be provided between fore, there is provided a heat exchanger comprising an ducts 4 and main inner area 5 by means of apertures or outer tubular member closed at its ends and provided ports 2a provided at or near the ends of the wall parts of with a fluid inlet at one end and a fluid outlet at the 25 the inner tubular member 2.

other end, and an inner tubular member of different The end walls 6 of the container (in particular the end cross-sectional shape to the cross-sectional shape of the walls 6 of the outer tubular member 1) thus formed may outer tubular member but positioned and dimensioned be concave or dished inwardly for added strength, and so as to provide a plurality of longitudinal points of an inlet pipe 7 may be secured medially and co-axially contact between the outer member inner surface and 30 of one end and an outlet pipe 8 secured medially and the inner member outer surface and a plurality of fluid co-axially at the other end for water or other fluid to be ducts defined by the longitudinal wall portions of the passed through the unit.

outer and inner members between said points of In the solar heating application, the heat exchanger COntact. unit thus formed is preferably arranged to be housed Preferred aspects of this invention will now be de- 35 within a housing 9 comprising a transparent or translu scribed by way of example with reference to a solar cent cover such as an arcuate or inverted U-shaped water heating system and with reference to the accom cover 10 secured at its lower ends to a base member 11, panying drawings, in which: which may be a metal base of shallow trough form, and FIG. 1 is a side elevational view of one form of solar is preferably provided at least on its upper inner side 11a water heating unit in accordance with the invention, 40 with a reflective surface whereby the sun's rays enter FIG. 2 is a cross-sectional view on line II-II of FIG. ing the housing 9 may be reflected back from such 1. reflective inner side 11a on to the underside of the heat FIG.2a is a cross-sectional view of a modification of exchanger unit. The housing 9 may include transparent the heat exchanger, or translucent end wall members 12, but for added FIG. 3 is a part broken perspective view of an assem- 45 strength and to provide support for the heat exchanger bled solar water heating unit, unit located there within, the end plates 12 of the hous FIG. 4 is a fragmentary view more particularly show ing 9 can be again of metal with preferably reflective ing one construction of the inner tubular member of the surfaces on at least the inner sides. The inlet and outlet heat exchanger, and pipes 7 and 8 may pass through such end plates 12 in FIG. 5 is a diagrammatic view illustrating the loca 50 providing support and an expansion pipe 13 may extend tion of a solar heating unit in accordance with the in from the outlet pipe 8 of the unit or from a pipe connec vention and incorporated in a domestic water heating tion thereto.

system. In a preferred construction of the invention, in addi In this first preferred form of invention, and one of tion to the main housing 9 the heat exchanger unit is the simplest forms, the outer member 1 of the heat ex-55 mounted within an outer transparent tubular cover changer is of cylindrical tube formation and may be member 14 which is of a heat retaining but sun's ray or formed from such as a black plastics material but is heat admitting material e.g. a polycarbonate plastics or preferably of a more permanent and heat conducting clear fibre-glass cover 14, there being a small airspace material such as copper or an aluminium alloy. The between the outer cover 14 and the outer tubular mem inner tubular member 2 may be of any polygonal cross 60 ber 1 of the heat exchanger. Where the heat exchanger section i.e. any multi-sided tubular figure and preferably outer member 1 is cylindrical, then of course the sur a regular sided figure, the illustrated example shows a rounding cover 14 will be similarly cylindrical but of a pentagonal cross-sectional inner member 2, and is slightly larger diameter.

formed so as to be a tight fit within the outer member 1 It will be appreciated that the invention is not con at the longitudinal corners 3 of the inner member 2. 65 fined to a heat exchanger having a cylindrical outer By providing a tight fitting construction it will nor member 1 and a pentagonal cross-section inner member mally be unnecessary to in fact secure the outer and 2, but that the outer member 1 can be, for example, be inner tube members 1 and 2 together by welding or the elliptical in cross-section (with the surrounding cover 5 where provided also similarly of elliptical cross-section) lar member and having a tubular peripheral wall defin or that the inner member 2 may be of square, hexagonal, ing an interior fluid compartment, said tubular periph octagonal or any other multi-sided cross-sectional sha eral wall having an outer surface defining a plurality of pe-the number of sides may be determined by the longitudinal lines of contact with the inner surface of actual diameter required for the heat exchanger, the the outer member to form a plurality of longitudinal capacity of the exchanger and/or the desired effective fluid ducts between the outer and inner members be peripheral surface areas of the formed ducts 4. In an tween said lines of contact, said ducts having opposite other variation of the invention, it is envisaged that the end parts in communication with the interior compart inner member 2 can be cylindrical and the outer mem ment of the inner tubular member for circulation of the ber 1 can be multisided or of regular polygonal cross fluid within the unit, and said interior compartment section with the dimensions of both inner and outer being dimensioned relative to said outer member to members 2 and 1 appropriately designed so that longitu accommodate the main volume of fluid passed into and dinal parts of the outer peripheral surface of the inner out of the unit.

cylindrical member 2 can be in longitudinal contact 2. A heat exchanger as claimed in claim 1 wherein the with medial longitudinal parts of the flat walls of the 15 outer tubular member is cylindrical in form and the outer member (as exampled in FIG. 2a). inner tubular member is of regular polygonal cross-sec The preferred solar heating unit and incorporated tion.

heat exchanger of this invention is arranged, as before 3. A heat exchanger as claimed in claim 1 wherein the mentioned, for thermo-syphonic circulation of water inner tubular member is a friction fit within the outer and as a storage unit for heater water and water to be 20 tubular member.

heated by solar rays, and is therefor arranged for dispo 4. A heat exchanger as claimed in claim 1 wherein the sition in an inclined or vertical plane for efficiency of inner tubular member is of cylindrical form and the operation. The arrangement provides a self-contained outer tubular member is of regular polygonal cross-sec unit which may be readily incorporated in a new or tion.

existing domestic hot water system, and FIG. 5 of the 25 5. A heat exchanger as claimed in claim 1 wherein the accompanying drawings illustrates diagrammatically inner tubular member terminates short of the ends of the the location of a solar heating unit, generally indicated outer tubular member in providing communication be at 15, in an existing conventional system comprising an tween the longitudinal fluid ducts and the inner area electric hot water storage cylinder 16 and cold water defined by the inner tubular member.

heater tank 17, the main cold water feed pipe 18 from 30 6. A heat exchanger as claimed in claim 1 wherein the tank 17 to cylinder 16 being severed at an intermediate inner tubular member extends for the full length of the point and new pipes 19 and 20 being provided to couple outer tubular member between the ends thereof, and to the solar heating unit inlet pipe 7 to the cold water fluid ports or apertures are provided at or near the ends pipe 18 leading from the tank 17 and couple the solar of the wall portion of the inner tubular member to pro heating unit outlet pipe 8 to the section of pipe 18 lead 35 vide communication between the longitudinal fluid ing to the hot water cylinder 16. ducts and the inner area defined by the inner tubular The illustrated and described solar water heating unit member.

is a single unit and it will be appreciated that multiples 7. A solar water heater comprising the heat ex of such units can be coupled in series or in parallel as changer of claim 1 with its outer tubular member may be required. 40 formed as or provided with a solar heat absorbtion Particular embodiments of the invention have been outer surface and being located within a further outer described and illustrated by way of example but it will tubular member of transparent material capable of ad be appreciated that other variations of and modifica mitting solar heat rays and defining a sealed air space tions to such embodiments can take place without de about said outer tubular member of the heat exchanger. parting from the scope of the appended claims. 45 8. A solar water heater as claimed in claim 7 wherein I claim: an outer housing having at least a major part of trans 1. A heat exchanger and fluid storage unit comprising parent or translucent material is provided to enclose an outer tubular heat absorbent member closed at its said heater.

ends and provided with a fluid inlet at one end and a 9. A solar water heater as claimed in claim 8 wherein fluid outlet at the other end, and an inner tubular mem 50 the housing has a base part with a reflective inner sur ber of different cross-sectional shape to the cross-sec face arranged to reflect solar rays onto the heat ex tional shape of the outer tubular member, said inner changer.

tubular member being positioned within said outer tubu : ck k & k