Studies on transverse fin tube heat exchangers

Abstract

This thesis presents an investigation of heat?transfer and pressure?drop characteristics of tubes with parallel fins (straight and inclined) placed concentrically inside an outer pipe through which air is flowing. Experimental investigations have been carried out on six finned tubes with pitch?to?length ratio, p/lp/lp/l, ranging from 1.27 to 2.52 (that is, with pitch?to?height ratio, p/ep/ep/e, ranging from 1.46 to 2.91) and inclination, ?\phi?, ranging from 0?0^\circ0? to 45?45^\circ45?. In all the finned tubes, the fin thickness is 1/16 in., and the fin tip presented a blunt edge to the flow. Only one outer pipe of inside diameter 3.281 in. has been used. The Reynolds number, ReReRe, of air flow varied from 10410^{4}104 to 11�411 \times 10^{4}11�4. A one?dimensional analysis has been carried out for temperature distribution in the inclined fin. The theoretical fin?surface temperature distribution thus obtained has been compared with the experimentally measured fin?surface temperature distribution along the fin length. Temperature and velocity distributions of the air flow have been obtained both at the entrance to and exit from the fin?tube test section. Bulk mean temperature (BMT) is evaluated using the velocity and temperature profiles and is compared with the graphical mean temperature (GMT) and the measured temperature at the mean position (MTAMP). Heat?transfer and pressure?drop correlations are presented for the finned tubes investigated. An attempt has been made to explain the best performance of finned tubes on the basis of optimum fin?gap ratio.