Single- and two-phase flow heat transfer in miniature straight and helical channels

This paper describes an experimental investigation of heat transfer in miniature helical flow passages under single- and two-phase Row conditions. The primary objective of the experimental part of the research was to study the effects of curvature on the hydraulic and thermal performance: of the miniature helical cold plate technology for electronic cooling. A series of test sections were designed and fabricated to cover a range of feature dimensions and hydraulic parameters of a cold-plate optimized by a preliminary analytical models. As a baseline for the curved channel experiments, additional linear channel test sections were also built and experimented. Experiments were performed over a wide range of single- and two-phase flow conditions by using R1 34a. It was found that the single-phase linear test section heat transfer data could be correlated against the Dittus-Boelter correlation with a reasonable success under turbulent flow conditions. On the other hand, it was demonstrated that the dependence of the heat transfer coefficient on the curvature was strong in the helical flow passage. In Fact, in terms of the Dean number. the heat transfer is proportional to the square root of the relative curvature of the flow passage. Each is discussed in terms of experimental data, and some experimentally based simple correlation offered for the prediction of heat transfer coefficient in miniature helical channels under flow boiling conditions.