Experimental transient response of a minichannel heat exchanger with step flow variation

Heat exchangers are essential components of many systems and their use is extended to include various industrial, chemical, and automotive applications. Heat exchanger behavior affects the total performance of a thermal system. Enhancing this critical component leads to improving the system overall performance and thus its energy efficiency. Since a heat exchanger operates in conjunction with other process equipment, its evaluation under a transient condition is crucial. A transient response of heat exchangers is necessary to evaluate the exchanger performance when subjected to a change in its conditions. The scarcity of experimental data on a transient response of heat exchangers in general and minichannel exchangers in particular is the main motivation for this research. This work is an investigation of an experimental characterization of the transient response of a cross flow liquid-air heat exchanger subjected to step changes in liquid mass flow rate. Hot fluid mass flow rate step changes of 0.5, 0.8, 1.5, and 2.0 are considered and the liquid outlet temperature response time is presented. The results are compared with the limited experimental work from the literature. While the outlet temperatures of both fluids do not respond instantaneously to the step change in the primary fluid mass flow rate, the cold fluid exhibits a faster response time than that of the hot fluid. The step variation increases the Reynolds number which results in a longer hot fluid response time to reach the steady state. The outcome of this work is valuable in the design, selection, and analysis of heat exchangers. The experimental data provided in this work can be used to establish a database for future advances in research. It also provides an overview of the characteristic behavior of certain parameters such as fluid temperatures, response time, and residence time when the heat exchanger is subjected to a change in the hot fluid mass flow rate.