Experimental investigation of the heat transfer process between a tube bundle and an upward aqueous foam flow

Abstract

High heat transfer intensity and low energy consumption for coolant transportation to heat transfer location are really significant nowadays. An extended range of heat transfer intensity control (control of volumetric void fraction and flow rate of coolant) and low mass flow rate of coolant are one of the most important factors for heat exchangers. In some cases the usage of aqueous foam as a coolant can solve all of the mentioned problems. Our previous investigation showed that heat transfer between a heated tube and aqueous foam flow is over five to ten times lower for the water coolant, but the density of foam is more than one hundred times lower than that of water. When applying aqueous foam as a coolant in practice, some cases are problematic. The reasons for this are the variation of the structure and the characteristics of foam. Therefore, usage of aqueous foam as a coolant needs to be narrowly explored. This work follows our previous investigations. The tube bundle with a new arrangement of tubes was used in this research work. Spacing between the centres of the tubes in the horizontal lines of the bundle and the spacing between tube lines were equal to 0.03 m. Each following line of tubes was located 0.01 m to the right of previous line. During the experimental investigation the dependence of heat transfer intensity (from tubes to foam flow) was determined on the volumetric void fraction of foam and the foam flow velocity. The experiments were performed for upward vertical foam flow for three different values of foam volumetric void fractions equal to 0.996, 0.997 and 0.998. The velocity of the foam flow was changed from 0.14 to 0.32 m/s. The influence of tube position in the bundle for www.witpress.com, ISSN 1743-3533 (on-line) WIT Transactions on Engineering Sciences, Vol 68, © 2010 WIT Press Advanced Computational Methods and Experiments in Heat Transfer XI 13 doi:10.2495/HT100021 the intensity of heat transfer was investigated. In research of the optimal geometry of a bundle, an average heat transfer intensity from bundle to foam flow was calculated and compared with the in-line and staggered tube bundles. The results showed that the heat transfer intensity of the investigated tube bundle to the upward foam flow is higher than that of the commonly-used heat exchangers. The analysis of the results is also presented in this paper.