要約

Pulsating heat pipes (PHPs) are an interesting class of passive two-phase heat transfer systems incorporating self-excited thermally driven oscillations for achieving a high rate of heat transfer. While many applications of PHPs have emerged, a systematic analysis of heat exchangers based on this technology has not been reported. In this work, two possible configurations of PHP-based heat exchangers, for process waste heat exchange as well as high heat flux handling needs, respectively, have been explored, scrutinized, and analyzed. These two configurations are (1) temperature-controlled liquid-liquid non-contact-type heat exchangers and (2) heat flux-controlled air-cooled systems. These two types of systems are performance tested under different operating conditions. Given the fact that the fundamental transport modeling scheme for PHPs is still not available, it is shown that global modeling of these devices can still be achieved. The temperature controlled PHP system is effectively modeled by conventional heat exchanger analysis techniques; i.e., the NTU-ε method. The heat flux-controlled PHP system is modeled by fin analogy employing the conventional theory of extended surface heat transfer, as applicable to diffusion fins. The mathematical modeling with these two systems is presented and limitations of global modeling are also discussed. The effectiveness values for the temperature-controlled heat exchanger system consisting of bare and un-finned PHP tubes, operating under gravity-assisted mode, were of the order of ∼ 0.25−0.45. The heat flux controlled mode has more favorable performance with overall thermal resistance lower than ∼ 0.2 K/W, corresponding to an effective thermal conductivity of PHPs in the range of 500−4500 W/mK for simple air cooling on bare tubes.