GB2326707A - Heat exchanger with divided header tank - Google Patents

Description

Title: Cooling Heat Exchanger and method of making a cooling heat exchanger.

The invention relates to a cooling heat exchanger such as the radiator in the cooling circuit for a motor vehicle engine, and in particular to the kind known as a bottle tank radiator.

Very early vehicle radiators were of the "vertical flow" kind and did not suffer from significant problems associated with gas in the coolant. However, when "cross-flow" radiators were adopted significant problems arose which various degassing techniques were developed to overcome, at first employing separate expansion tanks. Subsequently bottle tank radiators, in which the necessary expansion and degassing tank are provided in a single unit with the heat exchanger, were developed and have now been known for some time.

There are two general types of degassing known as "flow degassing" and "siphon degassing", and either can be employed in bottle tank radiators.

However, flow degassing bottle tank radiators suffer from a number of problems, one of which leads to premature failure. The siphon degassing is now the preferred form, as it does not suffer from the same problems and also provides some specific advantages.

One example of a prior art siphon degassing radiator is disclosed in European Patent No. 0 029 373. The radiator comprises a central heat exchange portion with a header tank at either side. One of the header tanks provides a collector compartment adjacent the heat exchange portion and a make-up tank, with a filler cap at it's upper end, distant from the heat exchange portion An opening is provided between the collector compartment and the make-up tank which is of appropriate dimension to produce a pressure drop between them. A siphon tube is also provided connecting the upper portion of the collector compartment to the lower portion of the make-up tank. Thus any gas rising to the top of the collector compartment is forced down the siphon tube into the make-up tank where it rises to the top adjacent the filler cap. Coolant to make-up the volume in the heat exchanger, header tank and collector compartment is drawn back through the opening.

It is a first object of the invention to provide an alternative form of cooling heat exchanger.

It is a second object of the invention to provide a method of manufacture of a cooling heat exchanger.

According to a first aspect of the invention there is provided a cooling heat exchanger comprising a heat exchange portion; an inlet header tank on a first side of the heat exchange portion, having an inlet from a coolant circuit; an outlet header tank on a second side of the heat exchange portion having an outlet to the coolant circuit, and having a substantially vertical partition dividing it into a first compartment communicating with the heat exchange portion and the outlet and a second compartment communicating with the first compartment, a filler spout and the outlet, wherein the cooling heat exchanger further comprises one way valve means which permits fluid flow between the top of the first compartment and the second compartment.

The heat exchanger portion is of the cross-flow type. The heat exchanger portion comprises a plurality of substantially horizontal coolant tubes arranged between and opening into first and second tube plates which communicate with the inlet and outlet header tanks respectively.

The one way valve means may comprise a bore at or adjacent the top of the substantially vertical partition, with a relatively narrow portion opening into the first compartment, a relatively wide portion opening into the second compartment and a step therebetween forming a valve seat, and a ball retained in the relatively wide portion moveable away from and into contact with the step to open and close the valve respectively.

Preferably the outlet header tank is formed in first and second parts, the first part comprising the first compartment, including the substantially vertical partition, and the filler spout, and the second part comprising the remaining parts of the second compartment. The first and second parts provide first and second edges which are adapted to be secured to each other to form a seam, and the first and second edges may bear interengaging formations.

According to a second aspect of the invention there is provided a method of making a cooling heat exchanger comprising: a heat exchange portion; an inlet header tank on a first side of the heat exchange portion, having an inlet from a coolant circuit; an outlet header tank on a second side of the heat exchange portion having an outlet to the coolant circuit, and having a substantially vertical partition dividing it into a first compartment communicating with the heat exchange portion and the outlet and a second compartment communicating with the first compartment, a filler spout and the outlet, wherein the method comprises the steps of: moulding a first part of the outlet header tank comprising the first compartment, including the substantially vertical partition, and the filler spout, and a second part of the outlet header tank comprising the rest of the outlet header tank; connecting the first and second parts of the outlet header tank together, and assembling the heat exchanger.

Preferably, the first and second parts of the outlet header tank are connected together by welding.

An embodiment of a cooling heat exchanger according to the invention will now be described, by way of example only, with reference to accompanying drawings in which: FIGURE 1 is a schematic partial cross-section lengthways through the cooling heat exchanger of the invention, and FIGURE 2 is a cross-section through the outlet header tank of the embodiment of Figure 1, with exploded views of the one-way valve and seam.

A cooling heat exchanger 10 comprises a heat exchange portion 11 of known cross-flow type. The heat exchange portion 11 comprises a plurality of coolant tubes 12 arranged substantially horizontally between and opening into first and second tube plates 13, 14, such that coolant approaching the first tube plate 13 can enter the tubes 12, flow along them and exit from the other end through the second tube plate 14. The heat exchange portion further comprises secondary heat exchange elements 15 in the form of corrugated fins 15, or other heat exchanger surface, connected between adjacent coolant tubes 12 in order to increase the surface area for heat exchange.

The cooling heat exchanger 10 further comprises an inlet header tank 16 and outlet header tank 18. An inlet 17, from a coolant circuit (not shown) opens into the inlet header tank 16 towards the top. The tank 16 is bounded on one side by the first tube plate 13 and thus communicates with the heat exchange portion 11. Thus coolant flowing into the inlet header tank 16 flows out through the heat exchange portion 11.

The outlet header tank 18 comprises a substantially vertical partition 19 which divides the tank vertically into a collector compartment 20 and a degassing compartment 21. One side of the collector compartment 20 is bounded by the second tube plate 14, and therefore communicates with the heat exchange portion 11. An outlet 22, to the coolant circuit (not shown), opens from the collector compartment 20 near the bottom thereof. Thus coolant flowing into the collector compartment 20 flows out through the outlet 22 and around the coolant circuit before returning to the inlet 17. Coolant is represented in Figure 1 by horizontal chain lines C, which illustrate that in use the collector compartment 20 is completely full of coolant whilst the degassing compartment 21 is only partly full of coolant.

The outlet header tank 18 further comprises, at the bottom of the degassing compartment 21, an opening 23 to the outlet 22. Thus the degassing compartment 21 communicates with both the collector compartment 20 and the outlet 23. In addition a one way valve 24 is provided at the top of the partition 19 which permits the flow of gas between the top of the collector compartment 20 and the degassing compartment 21. The valve 24 is best illustrated in the first exploded portion of Figure 2. The valve 24 comprises a bore 25, having a relatively narrow portion 25a opening into the collector compartment 20 and a relatively wide portion 25b opening into the degassing compartment 21 with a step 25e therebetween forming a valve seat, a valve member in the form of a ball 26 within the wider portion 25b of the bore, and a retaining means, in this embodiment, in the form of a circlip 27 to retain the ball therein. The relatively wide portion 25b is of sufficient length that the ball 26 can be forced away from the step 25e to open the valve 24, and can move back onto the step 25e to close the valve 24. Clearly, the one-way valve may take any other appropriate form.

The outlet header tank 21 further comprises, at the top of the degassing compartment 21, a filler spout 28, which is normally closed by a cap (not shown) of the kind incorporating a pressure relief valve. A second outlet 29 may also be provided from the degassing compartment 21 for receipt of a coolant level sensor (not shown), although this may be omitted if not required.

The cooling heat exchanger 10 operates to degas the coolant as follows.

Gas present in the coolant rises to the top of the exchanger 10, and much of it collects at the top of the collector compartment 20. The pressure at which the coolant circuit operates forces the gas through the one way valve 24 into the top of the degassing compartment 21. It therefore collects below the filler spout 28, and no longer mixes with the coolant actively flowing through the coolant circuit.

Any additional coolant required in the circuit, to top-up as a result of the gas movement, is drawn down through the opening 23 into the outlet 22 or collector compartment 20, as a result of pressure changes.

The outlet header tank 18 is manufactured in two pieces, 18a and 18b and are joined at a seam 30, as best illustrated in Figure 2. The first part 18a comprises the collector compartment 20, and part of the degassing compartment 21 including the filler spout 28. The second part 18b comprises the remaining part of the degassing compartment 21 and the outlet 22.

The seam 30 is formed from the edge of part 18a which comprises a recess 31, and the edge of part 18b which comprises a protrusion 32 adapted to be received in the groove 31. The seam 30 is joined by any appropriate method depending on the material from which the parts 18a and 1Sb are made. For example the parts 18M, 18b may be made from 30% glass filled nylon '66', in which case the seam may conveniently be joined by vibration welding. The inlet and outlet header tanks may however be made from any appropriate material.

The features disclosed in the foregoing description, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (10)

1. A cooling heat exchanger comprising: a heat exchange portion; an inlet header tank on a first side of the heat exchange portion, having inlet from a coolant circuit; an outlet header tank on a second side of the heat exchange portion having an outlet to the coolant circuit, and having a substantially vertical partition dividing it into a first compartment communicating with the heat exchange portion and the outlet and a second compartment communicating with the first compartment, a filler spout and the outlet, wherein the cooling heat exchanger further comprises one way valve means which permits fluid flow between the top of the first compartment and the second compartment.

2. A cooling heat exchanger according to claim 1 wherein the heat exchanger portion is of the cross-flow type.

3. A cooling heat exchanger according to claim 2 wherein the heat exchanger portion comprises a plurality of substantially horizontal coolant tubes arranged between and opening into first and second tube plates which communicate with the inlet and outlet header tanks respectively.

4. A cooling heat exchanger according to any one of the preceding claims wherein the one way valve means comprises a bore at or adjacent the top of the substantially vertical partition, with a relatively narrow portion opening into the first compartment, a relatively wide portion opening into the second compartment and a step therebetween forming a valve seat, and a ball retained in the relatively wide portion moveable away from and into contact with the step to open and close the valve respectively.

5. A cooling heat exchanger according to any one of the preceding claims wherein the outlet header tank is formed in first and second parts, the first part comprising the first compartment, including the substantially vertical partition, and the filler spout, and the second part comprising the remaining parts of the second compartment.

6. A cooling heat exchanger according to claim 5 wherein the first and second parts provide first and second edges which are adapted to be secured to each other to form a seam, the first and second edges bearing interengaging formations.

7. A cooling heat exchanger substantially as hereinbefore described with reference to the accompanying drawings.

8. A method of making a cooling heat exchanger comprising: a heat exchange portion; an inlet header tank on a first side of the heat exchange portion, having an inlet from a coolant circuit; an outlet header tank on a second side of the heat exchange portion having an outlet to the coolant circuit, and having a substantially vertical partition dividing it into a first compartment communicating with the heat exchange portion and the outlet and a second compartment communicating with the first compartment, a filler spout and the outlet, wherein the method comprises the steps of: moulding a first part of the outlet header tank comprising the first compartment, including the substantially vertical partition, and the filler spout, and a second part of the outlet header tank comprising the rest of the outlet header tank; connecting the first and second parts of the outlet header tank together, and assembling the heat exchanger.

9. A method according to claim 8 wherein the first and second parts of the outlet header tank are connected together by welding.

10. Any novel feature or novel combination of features as herein defined and/or shown in the accompanying drawings.