Maintenance of the required indoor air exchange rate by using compact regenerative heat exchangers

Abstract

Introduction. Ventilation systems of civil buildings experience problems of air exchange interruption and high heat losses. A solution to this problem is the use of compact decentralized ventilation units with the function of heat recovery from exhaust air. They are called stationary switching regenerative heat exchangers (SSRHEs). SSRHEs ensure high energy saving at low air flow rates. However, the required air exchange rate can be substantial even for one person. Therefore, a study was conducted to determine values of the energy efficiency coefficient of SSRHEs for the range of characteristic air flow rates. Materials and methods. The analysis of regulations and research papers, focused on determining the indoor air exchange required for one person was conducted. The air exchange rate is mainly determined through the recommended level of carbon dioxide concentration in a room. The energy efficiency coefficient of SSRHEs is determined by means of mathematical modeling of the heat exchange process in a single channel of a regenerative nozzle. Results. Values of the energy efficiency coefficient of SSRHEs are provided for a wide range of air flow rates. Efficiency reduction, accompanied by an increase in the rate of the air flow through the SSRHE, as well as a decrease in the nozzle length and an increase in the diameter of a single channel are shown. Recommendations are provided on the design of a regenerative nozzle that ensures extensive thermal energy savings at high air flow rates through the SSRHEs. Conclusions. Taking into account a wide range of values of the amount of air required per person, SSRHE capacity control is recommended. Research results can be used to modernize existing devices and develop new configurations of nozzles for such SSRHEs. The authors have found that experimental studies of the proposed configurations are needed to evaluate the level of noise generated by SSRHEs and the optimal nozzle design mitigating the risk of clogging.