Optimized offset strip fin for use in compact heat exchangers

摘要

An offset strip fin for use in compact automotive heat exchangers is disclosed. The offset strip fin has multiple transverse rows of corrugations extending in the axial direction wherein the corrugations in adjacent rows overlap in order that the oil boundary layer is continually re-started. The fin dimensions have been optimized in order to achieve superior ratio of heat transfer to pressure drop along the axial direction. In one aspect, .[.an.]. .Iadd.a .Iaddend. compact concentric tube heat exchanger has an offset set strip tin located in an annular fluid flow passageway located between a pair of concentric tubes. The preferred range of lanced lengths is determined to be between 0. 035" to 0.075" for periodically developed flow. Maintaining the lanced length in the regime of periodically developed flow is advantageous in that it gives a higher heat transfer coefficient than is achievable with fully developed flow. This also provides the added advantage that variations in the shape of the flow passages from the rectangular do not impact negatively on the heat transfer. .Iadd.The corrugations have top portions and bottom portions of the same width. The height of the corrugations is greater than this width. .Iaddend.