DK147583B - HEAT EXCHANGES WITH A HEADROOM SURROUNDED BY WATER - Google Patents

Description

147583

The invention relates to a heat exchanger with a main pipe surrounded by water, from which heat is to be transferred to a cold heat exchanger medium which flows through the main pipe.

When extracting energy from lake water by means of heat pump-5 systems, one often encounters the problem of icing the part of the system that absorbs the energy from the water. As the water in lakes and streams in many countries in winter time maintains a relatively low temperature (+ 1.8 ° C at 40 m depth about 1 m from the bottom in Storsjdn, Jämtland), the available temperature difference becomes 10 down to 0 ° C very small. Therefore, if you want to avoid icing of the heat exchanger's main pipe, make sure that the heat exchanger medium as it enters the main pipe has a relatively high temperature, namely so high that the energy absorption that occurs from the water becomes sufficiently small that this does not fry-15 looks. However, a high inlet temperature of the heat exchanger medium means that in order for sufficient energy to be absorbed into the heat exchanger medium, much of this must be used. This could be remedied by applying a lower inlet temperature of the heat exchanger medium to the main pipe, thereby causing a greater temperature drop between the water surrounding it and the heat exchanger medium, but in that case risking icing of the main pipe, the heat exchanger medium being then will absorb so much energy from the water that its temperature drops below freezing point.

Such icing significantly reduces the efficiency of the heat exchanger 25.

The heat exchanger according to the present invention is characterized in that the main pipe, at least along a stretch beginning at the inlet of the main pipe, contains a number of the main pipe substantially concentric pipe, the heat exchanger medium 30 being intended to be pressurized to the inner pipe, and wherein the tubes are provided with end walls so arranged as to cause the medium to flow back and forth in the spaces between the concentric tubes and finally to flow in the space between the outer tube and the main tube.

35 There is thus a considerable reduction in the danger of lamination of the main pipe even when using a heat exchanger medium with a low inlet temperature. This is because, with the application of the heat exchanger, a temperature gradient will adjust between the contact surface on the one hand between the outside of the main pipe and the surrounding water and on the other hand the inner pipe. This gradient is due to the fact that the heat exchanger medium flowing in the space between the outer tube and the main tube will be heated by the latter and will give part of its heat to the outer tube which in turn will heat the heat exchanger medium flowing inside the outer tube and this heat exchanger. medium will again dispense some of its heat to the next tube until finally a heat transfer to the cold heat exchanger medium flowing through the innermost inner tube. This in turn implies that the heat exchanger medium has already been heated to some extent as it flows into the gap between the outermost tube and the main tube, thereby reducing the energy absorption at this location from the surrounding water and correspondingly reducing the icing hazard. Although the heat exchanger medium flows to the space between the outer tube and the main pipe at a relatively high temperature, good energy is still obtained from the surrounding water, the heat exchanger medium during its flow in the space between the outer tube and the main tube giving off some of its heat. to the outer tube and, consequently, even undergoing a slower heating than would otherwise be the case.

In other words, the heat exchanger medium which flows in the space between the outer tube and the main tube can maintain a sufficiently low temperature to obtain a good heat transfer from the water and to the heat exchanger medium flowing in that space and which will be considerably higher than in the case where the heat exchanger medium in question could not dispense a portion of its heat supplied during its flow through said gap. The invention results in such that a cheap assembly of e.g. plastic pipes can be used to extract energy from e.g. lake water. The unit, which forms a closed system containing a low freezing point heat exchanger medium, can be installed directly in the lake.

The invention will now be explained in more detail with reference to the drawing, which shows an embodiment of the heat exchanger according to the invention, with fig. 1 is a schematic representation of a plant in which one or more heat exchangers according to the invention may be incorporated; and FIG. 2 is a horizontal section of an embodiment of the heat exchanger according to the invention.

5 In FIG. 1, 1 denotes a mechanism not shown in detail for circulating a heat exchanger medium, e.g. a liquid with a reduced freezing point through a pipe system 2 laid on the bottom of a lake. The temperature of the sea water can be approx. 2 ° C, while the liquid with reduced freezing point may have a temperature of 10 - 4 ° C.

The system 2 comprises two parallel pipes 3 and 4, between which one or more heat exchanger pipes 5, hereinafter referred to as the main pipe, are connected. The liquid with reduced freezing point is supplied under pressure through the pipe 3, after which the liquid 15 flows through the pipes 5, as shown by arrows, where heat is taken up by the liquid, so that its temperature rises to approx. + 1 ° C at the flow into the pipe 4. The heat thus obtained is used in the mechanism 1 in a conventional manner, whereby the temperature of the liquid leaving the mechanism 1 drops again to approx. -4 ° C.

One of the main pipes in FIG. 1 is shown in detail in FIG.

2. The main tube 5 is sealed at one end to an annular flange 6 on the casing surface of the tube 3 and at the other end is sealed to an annular flange 7 formed by a projected edge along a the casing of the tube 4 recessed circular aperture 8.

The main pipe 5 contains four interiors with the main pipe 5 generally concentric pipe 9-12. The sheath of the tube 3 is provided with a circular aperture 13, the edge of which is projected to form an annular flange 14, around which the tube 9 is sealed in a sealing manner.

The tube 10 is fixed by concentric means 15 around the tube 9 at a distance from the casing surface of the tube 3. The free end of the tube 9 extends at a distance from the present end of the tube 10 which is closed by an end wall 16.

The tube 11 is sealed in a sealing manner against an annular flange 17 of the tube 3. The tube 12 is secured by means of spacers 18 concentrically around the tube 11 at a distance from the casing surface of the tube 3. The end of the tube 12 which is closest to the tube 4 is closed by means of an end wall 19 which is spaced from the free end of the tube 11.

Liquid flowing into the tube 9 through the opening 13 in the tube-3 first flows through the tube 9 and then back and forth through the spaces between the tubes 9-12 and 5, 10 as shown by arrows in FIG. 2. Thereby, a controlled temperature gradient is obtained from the contact surface between the water and the energy-absorbing surface to the coldest part of the energy-absorbing medium, thereby avoiding a freezing of the contact surface of the main pipe 5 relative to the water.

The pipes 9-12 can advantageously consist of thin-walled, cheap plastic pipes. Only for the main pipe 5 does one have to make greater demands regarding diffusion density.

The proportions between zones A and B, cf. FIG. 2, as well as the number of pipes and their dimensions and lengths, are selected in such a way that optimum outlet temperature of the heat-carrying medium is obtained.