SE456449B - Heat exchanger working by natural convection - Google Patents

Abstract

The exchanger has a cellular structure (3,4) with open cells on opposite sides which form throughflow channels for a gas medium. The cell structures are tightly connected to cooling flanges (2) so that gas exchange and subsequent pressure compensation transverse to the gas throughflow direction are prevented.

Description

456 449 10 15 20 25 3D PREVIOUS: Drawn uïf-'öRlNcsl-'ORM Fig. 1 shows a heat exchanger according to the invention in perspective with parts removed for the sake of clarity. 1 denotes a number of pipes through which the liquid to be cooled flows at the same time as cooling air flows in the upward direction between the cooling flanges 2. It should be emphasized that the flow can also be directed in the opposite direction, namely when the air stream is cooled by the liquid Fig. 2. The heat exchanger is provided with flat wall portions 3 which extend parallel to the flanges 2 and further wall portions 11 which extend parallel to the pipes 1. In this way a cell structure is formed with enclosed spaces which form short channels and tightly connect to the spaces between the flanges. The walls 3 can be fixedly connected to the flanges or form a piece with these and wall wall abuts against the edges of the flanges. No air circulation in the transverse direction to the air flow is thus not possible. In previous solutions, where a chimney-type duct is arranged above a cooling element with a space between the cooling element and the duct acting as the chimney, a pressure equalization takes place in the transverse direction of the flow. This completely or partially loses the increased suction power that the negative pressure in the chimney creates. The negative pressure is proportional to both the difference between the average temperature of the cooling air at the flanges. It should be emphasized that even a low chimney gives a negative pressure that is very high and the ambient temperature as well as the chimney height. effective auxiliary force for the rather small driving force for heat transport with natural convection from the heat sinks. For example, a chimney height of the same order of magnitude as the height of the flanges gives a temperature reduction of the order of 50%.

A further advantage of the heat exchanger according to the invention is that when set up outdoors, the cell structure formed by the walls 3 and 4 can function as a screen to prevent the sun from heating the heat sinks while the sun increases the suction power by heating the outlet end of the duct.

Fig. 2 shows that the heat exchanger can also be used to cool a gaseous medium by means of a cold liquid. In this case, the chimney becomes downward and the negative pressure rises at the upper edge of the ducts.

Fig. 3 shows a comparison of the pressure distribution along the flow path of the air when the cell structure with the channels closely connects to the flanges (curves a and b) and when there is a gap (curve c).

Claims (3)

1. 456 449 - * 4 CLAIMS: Wu l Heat exchanger for heat exchange by natural convection between a liquid and a gaseous medium, with tubes (1) for the flow of the liquid and cooling fins (2) through which the gaseous medium flows, can be a cell structure (3,4) with cells (5) open on opposite sides, which form flow channels for the gaseous medium, the cell structure being tightly connected to the cooling fins (2), so that gas exchange and with the following pressure equalization in the transverse direction to the flow direction of the gas is prevented. Heat exchanger according to claim 1, characterized in that the cell structure is formed by intersecting flat walls (3,4), which extend parallel to the flanges (2) and to the pipes (1), respectively. Heat exchanger according to Claim 1 or 2, characterized in that the height of the flow-through ducts is chosen in such a way that at normal sunlight the cooling fins are in the shade.