Heat transfer enhancement by using holed-pin fins in a concentric heat exchanger

Abstract

The purpose of this investigation is to analyze the effects of the holed-pin fins which are located in the entrance of a concentric heat exchanger on heat transfer and pressure loss. The outer surface of the inner tube is maintained at constant temperature (100 C) by continuous contact with saturated water vapor introduced and filled into the annular space between the inner and outer tubes and discharged by a channel, like a teapot. The surface temperatures of the inner pipe, inlet and outlet temperatures of the air and pressure loss through the pipe are measured. The measurements are carried out for the Reynolds number ranged from 6000 to 12000. The design parameters are considered as the distance between the turbulators (s = 20, 30, 40 mm), hole diameter that is drilled on the pin fins (d = 6, 9, 12 mm) and the positions of the holes (top of the plate; namely Type T and center of the plate; namely Type C). Nusselt number and friction factor are found out based on the measurements. The comparison between the results of tabulated pipe and empty pipe, by means of Nusselt number and friction factor are done in order to show the effect of the turbulators in the concentric tube.