The characteristics of heat transfer and flow resistance in a rectangular channel with vortex generators

The vortex generators (VGs) are among the most popular actuators for the heat transfer enhancement of heat exchangers. Using pure water as the working fluid, the characteristics of heat transfer and flow resistance in a rectangular channel with novel types of VGs were studied numerically at the Reynolds number range of Re = 8900-29,900. Five types of VGs with the same frontal area were used in the present study and the corresponding mechanism of heat transfer was analyzed. The heat transfer enhancement and flow resistance were examined by using the dimensionless parameters j/j(0), f/f(0), R = (j/j(0))(f/f(0)). and R* = Nu(c)/Nu(0). The results revealed that, when the thermohydraulic performance factor R and Performance Evaluation Criterion R* were considered as the comprehensive evaluation criteria, the half-cylinder VG was the best. Then the effects of arrangement, length, radius, and spacing of the half-cylinder VGs on the heat transfer and flow resistance were investigated. When the half-cylinder VGs were arranged along the side-lined row, the thermohydraulic performance factor R was the largest. With the increase in the generator length, the thermohydraulic performance factor R increased at first and then decreased, and exhibited the maximum value at A/B = 0.50. With the increase in the radius and decrease of the spacing, the thermohydraulic performance factor R decreased. (C) 2017 Elsevier Ltd. All rights reserved.