Sorbent based enthalpy recovery ventilator (SERV) in northern building applications

Sorbent-based enthalpy recovery ventilator (SERV) is a potential replacement for conventional heat or enthalpy recovery ventilator (HRV/ERV) that require defrosting mechanisms in cold climates, such as in Canada. Sorbent materials (e.g. silica gel, CaCl2, alumina oxide) are non-toxic, inexpensive materials. However, the bulkiness, high pressure drop and large mass of adsorbent are major disadvantages of SERV in packed bed form. In this study, a novel design of sorbent discs with air channels is investigated which feature high heat and mass transfer performance with low pressure drop. A theoretical model is developed for heat and mass transfer in air channels in sorbent discs. A sensitivity analysis performed on design parameters e.g. channel diameter and spacing to achieve an optimum design. A prototype SERV is built in our laboratory. A custom-made experimental set-up equipped with thermocouples, humidity sensors, and an orifice plate air flow meter is designed based on ASHRAE 84 standards to evaluate the performance of the SERV prototype. The performance of the SERV is evaluated for several air flow rate, cycle time and outdoor air temperatures down to -15°C. It is shown that the proof of concept SERV consisting of 2.5 kg of heat storage materials and 2.1 kg of active sorbent material can recover up to 70% of heat and 80% of moisture from exhaust air (up to 20 CFM). It corresponds to 103 W of heat and 43 g of moisture recovery per hour which is comparable to the packed bed sorbent system reported in the literature, however, the proposed SERV offer a 60% less pressure drop.