AN APPARATUS FOR THE TESTING OF SMALL CRYOGENIC HEAT-EXCHANGERS

Most cryogenic processes demand high effectiveness heat exchangers, Th e performance of these exchangers is determined not only by convective heat transfer resistance, but also by other irreversibilities such as axial conduction, flow maldistribution, heat transfer with surroundin gs, and finite number of lateral heat transfer paths. While determinat ion of heat transfer correlations for exchanger cores is sufficient in most conventional applications, high-N-tu cryogenic exchangers must h e tested under true operating conditions. As a part of our matrix heat exchanger development program, an apparatus has been constructed for testing small, compact heat exchangers at low temperature. The apparat us, enclosed in a vacuum vessel, provides a variable cold end temperat ure and means for direct measurement of ineffectiveness. Temperature a pproaches at both ends and pressure drop in both channels are also mea sured. The construction of the apparatus as well as the instrumentatio n and data acquisition methods are discussed. The results of a test on a small matrix heat exchanger using the test apparatus are also prese nted. (C) 1996 American Institute of Physics.