Effect of twisted tapes and surface extensions in enhancing the condensation heat transfer of high-temperature saturated steam in a circumferential rectangular channel

Abstract

This article numerically investigates the impact of twisted tapes and extended surfaces (fins) on enhancing high-temperature steam flow in a circumferential rectangular channel, akin to the external jacket cavity of a tyre cure press. The passive enhancement techniques for improving the mold warm-up time of the tyre curing process have received limited attention in previous studies, which have primarily focused on enhancing heat transfer in configurations and working conditions typical of heat exchanger applications. The objective of this article is to enhance the condensation heat and mass transfer rate by geometrically modifying the internal flow path of the circumferential rectangular channel, resembling an external jacket cavity of a tyre cure press, using twisted tapes and extended surfaces. Four configurations are simulated: i) conventional circumferential rectangular channel, ii) channel with twisted tapes, iii) channel with surface extension, and iv) channel with both twisted tapes and surface extension. The heat transfer performance of all the modified channel configurations derived from the simulation results is assessed in comparison to the conventional channel. The channel, featuring a design that includes five twisted tapes with a twist ratio of 8 and 54 extended surfaces, records a substantial 36.85% rise in heat flux along with a notable 24% increment in the condensation mass flux. The simulation results are validated using an in-house experimental study. The tyre cure press in the experimental setup is modified to align with the design proposed by the simulation results, and a warm-up study is conducted. The warm-up time for the modified mold to attain the desired temperature is reduced by 33%, with no accompanying increase in steam consumption, compared to the warm-up time for the conventional mold. This significant reduction in mold warm-up time holds immense potential in enhancing the productivity rate, an ongoing requirement of the automobile industry.