The influence of geometrical parameters on heat and mass transfer processes in rotary heat exchangers

Abstract

This paper focuses on the influence of geometrical parameters of the rotary heat exchanger on its operation under high-speed rotor conditions. Proposed mathematical model of heat recovery wheel is based on a structure of the counter-flow heat exchanger model. After implementation of a numerical method on the modified α-model, the computer simulations were conducted. They allowed considering the distribution of the active heat and mass transfer zones (“dry,” “wet” and “frost”) on the matrix channel surface depending on the outdoor air conditions for different variants of rotor size. The obtained results indicate that the increase in the wheel’s depth leads to the increase in temperature effectiveness of heat recovery (from 0.667 to 0.814). Moreover, it was also established that the threshold temperature under which the frost is accumulated on the core surface also rises with the rotor depth (from − 10.7 to −9.6 °C). It was concluded that under certain outdoor air temperature conditions (t1i> –10.7 °C, for rotor depth equal to 0.40 m), the mass transfer rate of the condensed water vapor in the channels of the return air side is equal to the evaporation mass transfer rate in the channels of the supply air side, and hence, the temperature efficiency reaches the same value level as under “dry” operating conditions. It was established that only under frost accumulation conditions, the increased temperature effectiveness is observed.