Transient behavior of subcooled forced‐convective boiling with twisted tape inserts

Abstract

An internal twisted tape, when used to initiate subcooled swirling flow boiling, is a very effective method of cooling components which are subject to a high heat flux in a fusion reactor. In this study, the swirled channel was constructed using a copper cylinder (8 mm inside diam., 190 mm outside diam., and 100 mm heating length), which was equipped with a twisted aluminum tape (approx. 0.5 mm thick and 7.5 mm wide). The values of the tape-twist ratio y (the length required to complete a single 180-degree twist of the tape divided by the inside tube diameter) were approximately 1.8, 2.5, 3.2, 4.2, and infinity. Critical heat flux dependence on flow velocity and tape-twist was determined. Heating and cooling processes of large thermal capacity and inertia were used to obtain the wall heat flux via quasi-steady conditions, and several results for these limited cases are presented in the transition region near atmospheric pressure. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res 25(3): 178–191, 1996