GB1580466A

GB1580466A - Tubular heat exchanger

Info

Publication number: GB1580466A
Application number: GB3949877A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-09-22
Filing date: 1977-09-22
Publication date: 1980-12-03

Description

(54) TUBULAR HEAT EXCHANGER (71) I, ERWIN KLUCK, a German citizen, of 3052 Bad Nenndorf Prof.--Schriiter- Strasse 10, West Germany, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following state ment:- This invention relates to tubular heat exchangers for use in engine cooling radiators or interior heating or cooling radiators in motor vehicles. Such heat exchangers commonly have pipes fitted with closely spaced laminar baffles or heat transfer fins which serve to direct air over the pipes, through which a liquid, for example engine coolant, flows.

The use of a light metal in the manufacture of heat exchangers for engine cooling radiators and heat exchangers for interior heating systems in motor vehicles is generally known. Such heat exchangers have a plurality of pipes which convey liquid coolant between two headers, the pipes extending transversely to the direction of the air flow over the pipes.

In order to increase the heat transfer between the liquid and the air the pipes usually have fins in the shape of thin laminar baffles which are closely spaced, forming ducts through which the air flows.

Normally the pipes of such exchangers are arranged in two or more rows arranged one behind the other with attached baffles defining rows of air passages of rectangular cross section traversed by the pipes. Collars on the pipes serve to maintain the spacing between the baffles to define the air passages.

Heat exchangers of the aforesaid type are quite satisfactory for operation under the flow conditions and temperatures which prevail when cold air flows over the upstream row of pipes, but the effectiveness of the successive rows of pipes further downstream is reduced. The reason for this is that the downstream rows of pipes lie-at least partiallyin the lee of the upstream row of pipes, reducing the effective air flow. In addition the gradually increasing temperature of the air flowing over the successive rows of pipes in the direction of the air flow reduces the difference in temperature between the air and liquid flowing through the pipes, reducing the effectiveness of the downstream row or rows of pipes.Moreover, the laminar baffles are, because of the necessary distance between the rows of heat exchanger pipes, relatively deep, so that a considerable amount of material is used in the manufacture of the laminar baffles, increasing the weight and cost of the heat exchanger.

An object of the present invention is to provide a heat exchanger of the type referred to above affording an improved air flow for a given number of pipes, particularly over the downstream row of pipes, achieving a more even transfer of heat between the air and each individual pipe, and thereby allowing a reduction in the depth of the exchanger and affording a saving in the material used in the laminar baffles or heat transfer fins and a reduction of the overall cost of the heat exchanger.

According to the present invention there is provided a tubular heat exchanger for use in liquid-cooled radiators and for interior heating or cooling heat exchangers in motor vehicles, comprising a plurality of pipes extending between headers and laminar heat transfer fins which are closely spaced and extend perpendicularly to the pipes, defining air flow passages around the pipes, in which the pipes are arranged in a zig-zag array transverse the direction of the air flow over the pipes, in which the heat transfer fins have convoluted longitudinal edges which are formed with rounded corners so as to follow closely the boundaries of effective heat transmission surfaces around the pipes passing through the fins, and in which the said fins are provided with annular flanges adjacent the pipes, each flange serving to make thermal contact with a respective pipe and to maintain the spacing between the fins.

By the arrangement of the invention the airflow acts directly upon all the pipes of the heat exchanger without reduction in the total number of pipes, since the pipes all lie in a single convoluted or zig-zag shaped row.

Also the material requirements for the laminar heat transfer fins are reduced, be cause only minor surfaces are wasted on the heat transfer. Furthermore the convoluted laminar fins in the heat exchanger according to this invention can be punched out of a sheet of metal with minimal waste. This again saves on material in the manufacture of the heat exchanger. In addition side walls, which in some embodiments define air flow passages, can be manufactured with a narrower width so that even here a saving of material is achieved.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross section of a part of a heat exchanger according to one embodiment of the invention showing part of one of the laminar heat transfer fins in plan, and Figure 2 is a cross section of part of the heat exchanger, taken along the line Il-Il in Figure 1.

In the drawings reference numeral 1 represents part of a radiator heat exchanger made up of a number of parallel pipes 2, preferably fabricated in a light metal, for example aluminium, and laminar heat transfer fins 3 extending in parallel planes perpendicular to the said pipes 2 and disposed one above the other when the pipes 2 are arranged vertically.

The heat transfer fins 3, which are also fabricated in thin aluminium, could, for increased rigidity, be corrugated.

The laminar fins 3 are formed with annular flanges 4 around the holes 5 through which the pipes 2 pass and to which the pipes 2 are secured by means of expanding their diameters. The flanges 4 make good thermal contact for the heat transfer between the pipes 2 and the laminar fins 3 and in addition they also serve to maintain a precise spacing between neighbouring fins 3.

Intermediate raised flanges 7 may be provided between neighbouring flanges 4 on the fins 3 to maintain the requisite spacing between the fins 3 and at the same time cause turbulence in air flowing between the fins.

The holes in the fins 3 which result from the upsetting of the flanges 7 from the fins are of no importance and are herein referred to as punch holes 6.

As shown in Figure 1, the individual pipes 2 of the heat exchanger 1 are, in accordance with this invention, arranged in a zig-zag pattern, the axes of the pipes 2 lying on a zig-zag line 10 such that, in the illustrated embodiment, the pipes 2 are disposed at each vertex and on the median line of the said zig-zag line 10. The longitudinal edges 11 of the heat transfer fins 3 are convoluted and are tangential to the circular boundaries of the effective heat transmission surfaces 12 surrounding the pipes 2. The effective heat transmission surfaces 12 have circular boundaries since the pipes 2 are circular. In the regions of their vertices the longitudinal edges 11 are rounded with a fixed radius.

Both longitudinal edges 11 of the laminar fins 3 are identical in shape so that the fins 3 can be stamped or cut out from a strip or sheet of metal with minimal waste of material.

The punch holes 6 are to be formed in the regions of the internal corners of the zig-zag line 10 near the valleys of the convoluted longitudinal edges 11 of the fins 3, approximately equidistantly from the neighbouring three pipes 2.

In Figure 1 the direction of the cold air flow is indicated by arrows 9, whilst in Figure 2 the direction of the water flow through the pipes 2 is indicated by arrows 8.

The most important practical advantage of a heat exchanger according to this invention as illustrated is that by arranging the pipes 2, through which the liquid coolant flows, in a zig-zag or convoluted array each individual pipe 2 in the pipe assembly is directly exposed to the air flow, since none of the pipes lie in the lee of any pipe upstream of it with respect to the direction of air flow 9. The heat transfer efficiency therefore corresponds to that of a heat exchanger having a single row of pipes. Because of the convoluted shape of the laminar fins 3 as opposed to the usual rectangular shape a considerable saving on material is achieved. Moreover, because the air flow depth of the heat exchanger, relative to that of a conventional two row heat exchanger, is decreased, the pressure loss across the heat exchanger is reduced.The air resistance afforded by the heat exchanger remains constant, however, for a given number of pipes 2 in the heat exchanger.

Because of the reduced overall depth of the laminar heat transfer fins 3, side walls, which are sometimes provided with some heat exchangers, can also be narrower, achieving a further saving of material.

WHAT I CLAIM IS: 1. A tubular heat exchanger for use in liquid-cooled radiators and for interior heating or cooling heat exchangers in motor vehicles, comprising a plurality of pipes extending between headers and laminar heat transfer fins which are closely spaced and extend perpendicularly to the pipes, defining air flow passages around the pipes, in which the pipes are arranged in a zig-zag array transverse the direction of the air flow over the pipes, in which the heat transfer fins have convoluted longitudinal edges which are formed with rounded corners, so as to follow closely the boundaries of effective heat transmission surfaces around the pipes passing through the fins, and in which the said fins are provided with annular flanges adjacent the pipes, each flange serving to make thermal contact with a respective pipe and to maintain the spacing between the fins.

2. A heat exchanger as claimed in Claim

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. cause only minor surfaces are wasted on the heat transfer. Furthermore the convoluted laminar fins in the heat exchanger according to this invention can be punched out of a sheet of metal with minimal waste. This again saves on material in the manufacture of the heat exchanger. In addition side walls, which in some embodiments define air flow passages, can be manufactured with a narrower width so that even here a saving of material is achieved. The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross section of a part of a heat exchanger according to one embodiment of the invention showing part of one of the laminar heat transfer fins in plan, and Figure 2 is a cross section of part of the heat exchanger, taken along the line Il-Il in Figure 1. In the drawings reference numeral 1 represents part of a radiator heat exchanger made up of a number of parallel pipes 2, preferably fabricated in a light metal, for example aluminium, and laminar heat transfer fins 3 extending in parallel planes perpendicular to the said pipes 2 and disposed one above the other when the pipes 2 are arranged vertically. The heat transfer fins 3, which are also fabricated in thin aluminium, could, for increased rigidity, be corrugated. The laminar fins 3 are formed with annular flanges 4 around the holes 5 through which the pipes 2 pass and to which the pipes 2 are secured by means of expanding their diameters. The flanges 4 make good thermal contact for the heat transfer between the pipes 2 and the laminar fins 3 and in addition they also serve to maintain a precise spacing between neighbouring fins 3. Intermediate raised flanges 7 may be provided between neighbouring flanges 4 on the fins 3 to maintain the requisite spacing between the fins 3 and at the same time cause turbulence in air flowing between the fins. The holes in the fins 3 which result from the upsetting of the flanges 7 from the fins are of no importance and are herein referred to as punch holes 6. As shown in Figure 1, the individual pipes 2 of the heat exchanger 1 are, in accordance with this invention, arranged in a zig-zag pattern, the axes of the pipes 2 lying on a zig-zag line 10 such that, in the illustrated embodiment, the pipes 2 are disposed at each vertex and on the median line of the said zig-zag line 10. The longitudinal edges 11 of the heat transfer fins 3 are convoluted and are tangential to the circular boundaries of the effective heat transmission surfaces 12 surrounding the pipes 2. The effective heat transmission surfaces 12 have circular boundaries since the pipes 2 are circular. In the regions of their vertices the longitudinal edges 11 are rounded with a fixed radius. Both longitudinal edges 11 of the laminar fins 3 are identical in shape so that the fins 3 can be stamped or cut out from a strip or sheet of metal with minimal waste of material. The punch holes 6 are to be formed in the regions of the internal corners of the zig-zag line 10 near the valleys of the convoluted longitudinal edges 11 of the fins 3, approximately equidistantly from the neighbouring three pipes 2. In Figure 1 the direction of the cold air flow is indicated by arrows 9, whilst in Figure 2 the direction of the water flow through the pipes 2 is indicated by arrows 8. The most important practical advantage of a heat exchanger according to this invention as illustrated is that by arranging the pipes 2, through which the liquid coolant flows, in a zig-zag or convoluted array each individual pipe 2 in the pipe assembly is directly exposed to the air flow, since none of the pipes lie in the lee of any pipe upstream of it with respect to the direction of air flow 9. The heat transfer efficiency therefore corresponds to that of a heat exchanger having a single row of pipes. Because of the convoluted shape of the laminar fins 3 as opposed to the usual rectangular shape a considerable saving on material is achieved. Moreover, because the air flow depth of the heat exchanger, relative to that of a conventional two row heat exchanger, is decreased, the pressure loss across the heat exchanger is reduced.The air resistance afforded by the heat exchanger remains constant, however, for a given number of pipes 2 in the heat exchanger. Because of the reduced overall depth of the laminar heat transfer fins 3, side walls, which are sometimes provided with some heat exchangers, can also be narrower, achieving a further saving of material. WHAT I CLAIM IS:

1. A tubular heat exchanger for use in liquid-cooled radiators and for interior heating or cooling heat exchangers in motor vehicles, comprising a plurality of pipes extending between headers and laminar heat transfer fins which are closely spaced and extend perpendicularly to the pipes, defining air flow passages around the pipes, in which the pipes are arranged in a zig-zag array transverse the direction of the air flow over the pipes, in which the heat transfer fins have convoluted longitudinal edges which are formed with rounded corners, so as to follow closely the boundaries of effective heat transmission surfaces around the pipes passing through the fins, and in which the said fins are provided with annular flanges adjacent the pipes, each flange serving to make thermal contact with a respective pipe and to maintain the spacing between the fins.

2. A heat exchanger as claimed in Claim

1, in which the centres of the cross sections of the pipes lie on the vertices and median line of the zig-zag line interconnecting said centres.

3. A heat exchanger as claimed in Claim 1 or Claim 2, in which the heat transfer fins are provided with upset flanges adjacent the internal corners or valleys of the convoluted edges of the fins, said flanges serving to further maintain the spacing between the fins and to guide the flow of air around the pipes in use of the heat exchanger.

4. A heat exchanger substantially as herein described with reference to and as shown in the accompanying drawings.