FINE-TUBE HEAT-EXCHANGER WOVEN WITH THREADS

A new type of compact heat exchanger is suggested, and the fundamental heat transfer performance is studied chiefly from experimental aspects. The design concept is based on the new principles for heat transfer enhancement, namely 'reducing the size of heat transfer surfaces' and 'arranging a couple of turbulence promoters so as to cause drastic change in the turbulence structure'. To satisfy such requirements, the heat exchanger consists of fine tubes (of.d. approximately 1 mm) and woven threads (diameter approximately 0.3 mm); the latter play a combined role of both turbulence promoter and fin. The maximum heat transfer coefficient obtained in the experiment is 14-fold larger than that around a cylinder without threads. Owing to the combination of the woven threads and the very small characteristic length, the heat transfer coefficient per unit projected area is about 5 x 10(3) W m-2 K-1, and that per unit volume reaches 3 x 10(6) W m-3 K-1.