Use of Two-Phase Heat Transfer for Improved Transformer Cooling. Final Report

摘要

The potential for significantly improving transformer thermal performance by implementing new heat transfer technology was investigated. The investigation centered around two-phase heat transfer techniques and devices. Equipment was considered that was active (that is, consumed energy), as well as equipment that was passive. For power class transformers, for example, this included such devices as a forced-flow heat pipe as well as a heat pump system in which a vapor compressor reduces the transformer oil temperature below that of ambient air. Cost comparisons were made for both systems, with the former appearing cost competitive in forced air operation and the latter appearing cost competitive in the thermal dissipation range of 20 to 200 kW. Additional effort was also directed toward studies of improved single-phase cooling systems for power transformers, including the development of a more precise technique for modeling thermosyphon flow and its application to the design of finned aluminum transformer radiators. The use of two-phase heat transfer techniques was considered in particular detail for applications where effective heat rejection is difficult using existing technology. For underground transformers, reflux condenser systems were considered as a means of increasing load capability. In particular, heat pipes linking the transformer to surrounding soil were found to be an optimal method of cooling. An additional benefit of this transformer cooling investigation was development of two possible methods of measuring core and coil temperatures. These methods and the design of the measuring equipment are discussed. (ERA citation 03:021530)