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Wind turbine with flat heat pipe heat exchanger

IP.com Disclosure Number: IPCOM000205586D
Original Publication Date: 2011-Mar-31
Included in the Prior Art Database: 2011-Mar-31
Document File: 3 page(s) / 166K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

In recent wind generators, there are power losses which are caused e. g. by thermal effects like the field weakening of magnets or the reduction of lifetime of the stator winding insulation. These effects need to be reduced by utilization of appropriate cooling systems to meet the thermal requirements of the generator. Currently, most wind generators utilize a cooling system based on air to water heat exchangers. These use external air to cool an internal liquid cooling system. The problem of these passive cooling systems is that they are usually very large and heavy. The conventional heat exchangers utilize single-phase flow in coolant tubes and cooling fins outside the tubes to increase the heat transfer area between the heat exchanger and cooling air. The finned aluminum structure has a large exchange surface and thermal conductivity. The heat exchanger has a tank at each end. Hot coolant enters an inlet at top of one tank, flows across the flat core tubes, and returns through an outlet at the bottom of the other tank. The number and size of the flat tubes and fins is a measure for the surface and heat transfer ability. Additionally, the liquid cools down some internal air in order to cool the generator without using ambient air. This is especially relevant for corrosion risk of offshore applications. Figure 1 shows the scheme of a conventional air to liquid heat exchanger.

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Wind turbine with flat heat pipe heat exchanger

Idea: Jean Le Besnerais, FR-Brande

In recent wind generators, there are power losses which are caused e. g. by thermal effects like the field weakening of magnets or the reduction of lifetime of the stator winding insulation. These effects need to be reduced by utilization of appropriate cooling systems to meet the thermal requirements of the generator.

Currently, most wind generators utilize a cooling system based on air to water heat exchangers. These use external air to cool an internal liquid cooling system. The problem of these passive cooling systems is that they are usually very large and heavy. The conventional heat exchangers utilize single- phase flow in coolant tubes and cooling fins outside the tubes to increase the heat transfer area between the heat exchanger and cooling air. The finned aluminum structure has a large exchange surface and thermal conductivity. The heat exchanger has a tank at each end. Hot coolant enters an inlet at top of one tank, flows across the flat core tubes, and returns through an outlet at the bottom of the other tank. The number and size of the flat tubes and fins is a measure for the surface and heat transfer ability. Additionally, the liquid cools down some internal air in order to cool the generator without using ambient air. This is especially relevant for corrosion risk of offshore applications. Figure
1 shows the scheme of a conventional air to liquid heat exchanger.

In the following, a novel solution is proposed which equips the wind turbines with heat exchangers incorporating heat pipes, which are also referred to as so-called two-phase closed thermosyphons. One is schematically depicted in figure 2. A small amount of working liquid is filled in a tube or other container type. Then air is evacuated from the container and it is sealed. Heat is applied to the evaporator section, which causes the liquid to vaporize. Due to the higher vapor pressure in the hotter section, the vapor flows to the colder section of the heat pipe, where it is condensed. The condensated liquid then flows back from the condenser section to the evaporator section under the assistance of gravity. High heat transfer rates can be achieved with a small temperature difference between the condenser section and the evaporator section of the heat pipe, because the latent heat of vaporization is very large. Consequently, the temperature is rather uniform along the heat pipe. The heat exchanger using heat pipes will have a much higher cooling efficiency compared to the conventional single-phased solutions, due to the fact that heat pipes are very efficient two-phase heat transfer devices. The proposed heat exchanger utilizing heat pipes is depicted in figure 3

The proposed solution can advantageously be used to increase the UA-value of the heat exchanger of a w...