A Novel Spherical Packed Bed Application on Decentralized Heat Recovery Ventilation Units

Abstract

Decentralized heat recovery ventilation (HRV) systems are assumed as simple solutions to obtain a healthy and comfortable indoor environment. A wall or window mounted compact version of decentralized HRV systems (mono unit) are used for small scale, mostly residential applications. A fan and a heat exchanger are the critical components of this compact system. The flow capacity of these units are down to 10 m3/h, where efficiencies over 90% are commonly declared by the manufacturers. On the other hand, spherical packed beds (SPD) are widely used in the heat transfer applications such as; chemical reactors, grain driers, nuclear reactors, thermal storage in buildings and in solar thermal power plants, due to operational convenience. These systems are operated under steady flow conditions, unlike decentralized HRV systems which are designed for cyclic operation. In this study, heat recovery performance of a spherical packed bed heat exchanger for a decentralized HRV system is investigated. A one dimensional mathematical model for a SPD is obtained and an in-house computer code is developed to solve the transient heat transfer inside the packed bed under cyclic operation conditions. Well known convenient correlations were used for pressure drop calculations. A number of bed and sphere diameters were studied in a wide range. Various flow time and number of cycles were studied for the hot and cold flow to understand the SPD performance for HRV applications. This novel application also has the potential for regenerative heat recovery systems.