Experimental investigation on performance of three fluid heat exchanger using artificial roughness

Abstract Increasing heat transfer under controlled pressure drop is the primary goal of the present experimental work. This can be obtained in three-fluid heat exchanger (TFHE) by using anartificial roughness (circular rings provided on the outer surface of the helical coil).This experimental work shows that the circular rings (1 mm diameter at 5 mm pitch) provide more heat transfer (HT) under controlled pressure drops for industrial applications in water and space heating simultaneously. The waste hot fluid (WHF) and normal water (NW) cycled through the helical coil’s inner and outer annuli. The trials were conducted out under turbulent circumstances, with the Reynolds number (Re) of WHF ranging from 7500 to 25000. The experimentally determined Nusselt number (Nu) for the helical coil side is checked and validated against the Nu stated in the literature. It is achieved from the experiments that the Nu and pressure drop rise as the Re rises. Due to the circular rings at 5 mm pitch, the percentage increment in Nu, pressure drop, friction factor, overall heat transfer coefficient, and effectiveness for the HC is found to be 7.07%–12.14%, 9.20%–18.18%, 19.05%–22.85%, 3.11%–3.34%, and 1.15%–8.89%, respectively, as compared to a roughness of 1 mm diameter at 10 mm pitch.