A Transient Response Comparison of a Conventional and a Meso Heat Exchanger under Mass Flow and Temperature Step Changes

- The increasing worldwide energy consumption problem motivates the effective management of thermal systems. A heat exchanger is an important component in many thermal systems, such as a radiator of an engine cooling system in vehicles. Heat exchangers are generally designed and characterized to work under steady-state conditions. However, a change in operating conditions exposes heat exchangers to a transient state, therefore, it is important to study their transient responses for better control of the system and efficiency improvement. In this study, the experimental responses of two types of heat exchangers: conventional, and meso heat exchangers subjected to a sudden change in inlet temperature and mass flow rate of the hot fluid are compared and presented. The transient outlet temperature responses of both hot and cold fluids as well as the transient heat exchanger effectiveness and heat transfer rate variations are found in this work. A general empirical correlation is obtained for the hot fluid transient dimensionless outlet temperature subjected to mass flow rate step change. Furthermore, results show that the meso heat exchanger exhibited higher heat transfer rate and effectiveness as well as reached steady state faster than the conventional heat exchanger. Even though the meso heat exchanger has a longer initial delay time, it possesses a higher response time than a conventional heat exchanger, regardless of the step change.