Experimental study of heat transfer coefficient in heat exchanger reactors with square millimetric zigzag channels

Abstract

Heat transfer performances of compact heat exchanger reactors were experimentally characterized and measurement uncertainties were evaluated using the derivation method. Prototypes presenting two kinds of process channel configurations (zigzag and straight channels) with square cross-section were investigated, from 2 mm to 4 mm depth. Water or glycerol-water mixture were used as the process fluid, cooled by water as the utility fluid. Reynolds number ranged between 15 and 7300 and Prandtl number between 3.1 and 115. From the measurements of the fluid temperatures and flow rates, local heat transfer coefficients were calculated. In zigzag channels, it ranged from 760 to 15,000 W.m−2.K−1, with an average uncertainty of 15.7%. With water as the process fluid, the heat transfer coefficients in zigzag channel were 2 to 5 times higher than in straight channel. The experimental data were then used to establish a correlation for the Nusselt number in the zigzag channels as a function of the channel geometry, the fluid properties and flow rates expressed in terms of dimensionless numbers. The average relative difference between experimental and calculated values was 9.1%. Finally, the consistency of the correlation was confirmed by comparison with data obtained in a previous work based on CFD.