Experimental Study on Heat Transfer Enhancement and Pumping Loss In R407c Evaporator Using Twisted Tape

Abstract

An experimental study on heat transfer enhancement and pumping loss is done during evaporation of R407C in horizontal 2 m long copper tube Evaporator. Plain tube and plain tube with turbulent promoters are considered for investigation. Experimentation is carried on the plane tube and plane tube with twisted tapes. Operating conditions: refrigerant mass flux, G-100 – 350 kg m^-2s^-1, heat Flux, q-1.4 – 9.1 kW m^-2, temperature range: -14 to 10.9 ⁰C, pressure range (absolute): 3.5 -8 bar and vapor quality, x- 0.05 -0.95.Three twisted tapes are used as turbulent promoters of twist ratios 8, 10 and 12. Study reveal that heat transfer enhancement depends on geometry of twisted tape and operating conditions. Twisted tape with twist ratio, y = 12 shows maximum heat transfer at all operating conditions with 56.51% maximum average increase in heat transfer coefficient. With increasing operating conditions of heat flux, mass flux and pressure, pumping loss increases. Twisted tape with twist ratio, y = 12 is giving minimum percentage increase of pumping loss from 2.57% to 5.20% over plain tube.