Experimental investigation on thermal-hydraulic characteristics in a traverse rib tube fitted with regularly spaced helical tapes

摘要

A synergy enhancement approach by simultaneously combing a traverse rib tube (TRT) with regularly spaced helical tapes (RSHTs) was devised to increase thermal performance of heat exchangers aiming for saving more energy. Air flow heat transfer and pressure drop tests were respectively performed under constant heat flow and isothermal conditions by analyzing different parameters comprising Reynolds numbers, pitch length ratios and space ratios. In contrast to the plain tube, the gained results in the alone use of TRT show that the heat transfer rate and flow resistance are respectively augmented by 35.3%-49.4% and 1.48-1.70 times. By further fitting RSHTs into the TRT, the heat transmission performance and friction loss are increased by about 108.1%-177.0% and 5.97-15.31 times, respectively. The flow patterns are dominated by transverse streams and swirl flows, which render enhanced turbulent intensity and improved fluid mixing in the air flow passage, leading to thermal enhancement. The maximum value in performance evaluation criterion of about 1.26 is achieved by both the TRT and the TRT fitted with RSHTs. Moreover, the empirical formulas are developed from experimental values with deviations within ±5% and ±8% for Nusselt number and friction factor, respectively. Compared with published studies of swirl flow devices, the proposed enhanced apparatus of the TRT fitted with RSHTs in present study can be regarded as a proper candidate for potential heat transfer enhancement applications.