IE50686B1

IE50686B1 - Space heater

Info

Publication number: IE50686B1
Application number: IE228/81A
Authority: IE
Original assignee: Runtal Holding Co Sa
Priority date: 1980-02-07
Filing date: 1981-02-06
Publication date: 1986-06-11
Also published as: DK53481A; GB2072316B; CH644444A5; IE810228L; IT8119541A0; DE3026731C2; ES265380U; BE887413A; FR2475708B1; DK151159B; CA1132531A; DK151159C; GB2072316A; DE3026731A1; ES265380Y; FR2475708A1; IT1135326B

Abstract

In a heat exchanger co-planar, parallel flat tubes (1) are connected at a distance inboard from their ends to manifolds (2) for the supply and return flow of a fluid medium. The flat tubes (1) have very small internal clear widths and the ratio of the internal cross-sectional area to the outer peripheral length of each tube (1) is less than or equal to 2.5. The fluid medium flows with correspondingly greater velocity through the flat tube. A smaller thermal inertia and a better heat transfer results. The tubes (1) are closed at their inwardly bent edges by a welding seam. Outwardly pressed wall regions of the manifold (2) surround bores therein and are connected by welding to the tubes (1), the welding taking place from the inside of the manifold. The manifold (2) consists of at least two parts which are secured together by welding.

Description

The invention concerns a space heater having flat tubes arranged mutually in parallel and connected at a distance from their ends to forward and return flow manifolds.

Space heaters of this type are known in numerous different embodiments, the differences being manifested particularly in the construction of the connections of the parallel flat tubes to the manifolds in order to enable the heater to be produced in a rational manner by welding either manually or by machine, for example by means of a projection-welding machine that produces a plurality of simultaneous weld connections.

In the utilisation of space heaters, bodies in a central heating plant, hot water flows through the heater at a velocity which depends amongst other things, on the selected dimensions of the tubes. The thermal inertia of the heater and its heat dissipation depend on the flow rate of the hot water.

For reasons of manufacturing technique, in known heaters flat tubes have been used which have hitherto been made with a relatively large ratio of water content to heating surface of the flat tube or in other words, the ratio of - 2 50686 the inner cross-sectional area to the circumference of the tube is relatively large.

A task of the present invention is to provide a heater which, in the interests of better energy utilisation and energy saving has a lower thermal inertia and better heat dissipation or transfer due to a greater velocity of flow of the heating medium and which, by virtue of constructional simplifications, may be manufactured in an economic manner.

According to the present invention there is provided a space heater comprising an array of parallel, coplanar flat tubes connected at a distance inwardly from their ends to manifolds for the forward and return flow of a fluid medium, each flat tube having such a cross-section that the ratio of the internal cross-sectional area of each tube to its outer circumferential length - measured in mm - is in the range of from 1.1 to 2.5 mm, and each tube being closed at each of its ends by a welded joint between the end portions of the mutually opposed longitudinal sides of the tube, at least one of the end portions being bent inwardly towards the other.

The flat tubes may be made in long tubular lengths and cut to the desired size before being closed. The welded joint between the end portions may be formed with both of the end portions bent inwardly or with only one portion bent inwardly. In the latter case, the end portion that is not bent should be shortened by the extent of the inwardly bent portion.

Further details will become clear from the following description and drawings, in which various embodiments of the invention are shown purely by way of example and in which: Figure 1 is a front elevational view of the heater, Figure 2 is a vertical section along line I-I of Figure 1, on an enlarged scale, - 3 3 0 6 8 6 Figure 3 is a vertical section like Figure 2, but in a different embodiment of the connection and wall-opening, Figure 4 is a horizontal section through a flat tube and a manifold along the line II-II in Figure 1, on another enlarged scale, Figure 5 is a horizontal section like Figure 4 but showing a different embodiment of the flat tube and manifold; and Figure 6 is a vertical section through a further embodiment of the heater with flat tubes on both sides of the manifold, on a larger scale.

The space heater according to Figure 1 has five co-planar somewhat spaced10 apart flat tubes 1 arranged horizontally and mutually in parallel which are connected on their rear side at a distance (inboard) from their ends to vertical manifolds for the forward (supply) and return flow of a fluid medium therethrough. Each of these flat pipes 1 is connected to the same manifold pipe 2 via two couplings 3 of which one coupling is disposed near the upper edge of the flat tube while the other coupling is disposed near the lower edge of the flat tube so that the flat pipes may be vented and emptied without difficulty. Each of the manifolds 2 has a coupling 4 to which are connected the supply and discharge ducts for a heating medium.

From the vertical sections through the flat tube 1 shown in Figures 2 and 3, it may be seen that the width of the internal cross-sectional area 5 is relatively small in relation to its length. The clear width of the tube amounts to 3-5 mm for a height of the flat tube of about 70 mm, measured on the outside. The tube has a plate (wall) thickness of 1.25 mm to at most 2.00 mm. In such an extremely flat tube the ratio of the internal cross-sectional area to the external peripheral length of the tube is less than or equal to 2.5 (times the unit of length). Calculated over the length of the tube, the same value - 4 50686 is true for the ratio of the volume of water in the tube to the external heating surface area of the tube. In comparison with the greater tube cross-sections of known heaters a small value here signifies that the heating surface area related to the same volume of water is greater and consequently the heat transfer or dissipation of the heating body is better.

Since furthermore the flat tube contains less water which flows through at a greater velocity, the thermal inertia of the heater is markedly lower.

The dimensioning of the flat tubes accordingly allows various advantages regarding the improved exploitation of energy to be achieved.

The flat tubes manufactured in longer lengths are cut according to need and are closed at their front ends which can be carried out in a very advantageous manner in the case of very flat pipes. Figure 4 shows an embodiment wherein the flat pipes are closed at their front ends by providing the mutually opposite longitudinal sides of the pipe with respective terminal zones 6 which are bent inwardly towards the centre, with a welding seam 7 securing the terminal zones 6 together.

In the embodiment according to Figure 5, each of the flat tubes is closed at its front end by a welding seam 9 that connects a respective terminal zone 8 of one, inwardly bent longitudinal side of the tube with the oppositely lying longitudinal side of the flat tube, the latter being shortened by the extent of the said terminal zone 8.

The flat tubes are illustrated in Figures 4 and 5, on an enlarged scale, while in Figures 2 and 3 they are shown in their approximate natural size. The edges of each flat tube, where the or each inwardly bent end portion lies adjacent to the side of the tube, thereby forming a slotted edge, may be closed by a weld that generally will be somewhat thicker than the weld seam 7 or 9. - 5 50886 It is thus evident that the very fiat tubes may be closed by a single welding seam.

Consequently, with relatively low manufacturing expenditure, it thus becomes possible to achieve a heater construction which is preferable on aesthetic grounds, and which has manifolds on the rear side thereof at a position somewhat inwardly from the ends of the flat tubes.

A construction with manifolds arranged at and welded to the ends of the flat tubes requires more labour input and is less satisfactory from an aesthetic consideration due to the thickening at both ends required by the larger manifold.

Wall openings or bores 10 are formed in the manifolds 2 in order to connect them to the flat tubes 1 as shown in Figures 2 and 3; the region 11 of the wall surrounding the wall opening is pressed outwardly either in a step-like manner according to Figure 2 or, as shown in Figure 3, in some other manner a wall region 12 is pressed outwardly in a funnel-shaped configuration. The flat tubes 1 have wall openings or bores 13 of smaller diameter disposed coaxially with each of the wall openings or bores 10. A wall region 14 of the flat tube 1 surrounding the smaller diameter wall openings 13 is welded to the outwardly pressed wall region 11 according to Figure 2, or 12 according to Figure 3. A welding seam 15 shown only in Figures 4 and 5 is not shown in Figures 2 and 3 for the sake of clarity. A small clearance remains between the flat tubes 1 and the manifold 2 after the welding of the outwardly pressed wall section 11 or 12, which clearance enables any weld connection that may be found to be leaky subsequently to be made completely leakproof by laying a ring around the connection and brazing it.

The connection of the flat tubes 1 with the manifolds 2 by means of the welding seam 15 takes place from the inside of the manifolds as may be seen - 6 50686 from Figures 4 and 5. To enable this to be done, each manifold 2 consists of at least two parts extending over the length of the pipe and in particular, according to Figure 4, from a part 20 which is U-shaped in cross-section and a cover like part 21. These parts are connected together after making all the weld connections with all the flat tubes by means of welding seams 22 running along the whole length of the manifold. In the embodiment according to Figure 5, two similar U-section parts 23 and 24 of the manifold 2 are connected together by two welding seams 25. Naturally, many other possibilities of configuration exist in relation to these manifold parts, in particular in order to facilitate the assembly of the parts, one part may be formed with an edge which has been pressed slightly inwardly in a step-like manner and which engages over the other parts in the manner of a cover.

With a manifold consisting of at least two parts and using the above described methods, a heat-exchanger according to Figure 6 may also be made without difficulty, this heater having flat tubes on the opposite sides of the manifold. In this heater, for each of the two parts of the manifold 2, firstly the connections to the respective mutually superposedly arranged flat tubes are made by welding and subsequently the two parts of the manifold are welded together. A multiple, bent convector plate 30 is arranged in the space between the flat tube arranged on the two oppositely lying sides of the manifold as shown in Figure 6. Such a convector plate may also be rigidly arranged on the rear side of flat tubes arranged on only one side of the manifold.

Claims

1. A space heater comprising an array of parallel, coplanar flat tubes connected at a distance inwardly from their ends to manifolds for the forward and return flow of a fluid medium, each flat tube having such a cross-section 5 that the ratio of the internal cross-section area of each tube to its outer circumferential length - measured in mm - is in the range of from 1.1 to

2.5 mm, and each tube being closed at each of its ends by a welded joint between the end portions of the mutually opposed longitudinal sides of the tube at least one of the end portions being bent inwardly towards the other. 10 2. A space heater according to Claim 1, v/herein at at least one end of some of the tubes, the end portions of both the mutually opposed longitudinal sides are bent inwardly.

3. A space heater according to Claim 1, wherein at at least one end of some of the tubes, the end portion of only one of the longitudinal sides is bent 15 inwardly, the other end portion being shortened by the extent of the inwardly bent end portion.

4. A space heater substantially as herein described with reference to and as shown in Figures 1 and 2 or Figure 3 or Figures 1 and 4 or Figure 5 or Figure 6 of the accompanying drawings.