Analysis of Heat Transfer Coefficients for a Micro-Jet Heat Exchanger

This study investigated a microjet heat exchanger. The microjet heat transfer technique offers numerous advantages, such as high heat transfer coefficients, efficient heat transfer even at low temperature differences, the ability to easily regulate the heat flux, and the possibility of direct contact with the cooled surface. The experimental setup and the microjet heat exchanger are discussed. The experiments were conducted using a microjet-generating head equipped with four membranes, each having 364 circular slits with a diameter of 160 μm, a nozzle-to-heat-transfer-surface area ratio Ar of 0.0019, and a ratio of the distance between adjacent nozzles to their diameter s/d of 19. The working fluid was water. The volumetric flow rate was adjusted manually and ranged from 12.8 to 133 mL/s, corresponding to Reynolds numbers in the range of 279–4166. The experiments were conducted for four different distances between the nozzles and the heat transfer surface, adjusted using appropriate spacers with thicknesses of 1, 3, 5, and 7 mm. The heat transfer coefficients k_exp were calculated from the obtained results.