The effect of internal leakage of air streams on effectiveness of the fixed-bed regenerator for fast switching cycle of its operation: experimental and numerical results

Abstract

The paper presents the course of heat and mass transfer in the fixed-bed heat exchanger. For this purpose, a previously developed original mathematical model of a fixed bed regenerator was used. On the basis of the developed model, a computer program was written and verified using experimental data. The validation results confirmed that the developed model can predict the performance of the heat exchanger. The effect of the presence of internal air leaks was analyzed for conditions of sub-zero outdoor air temperatures. Multi-variant numerical simulations carried out under low outdoor air temperature operating conditions made it possible to demonstrate many irregularities. Effectiveness variation was carried out for different thermodynamic air parameters. A maximum increase in device effectiveness (up to 0.92) was demonstrated, confirmed by the additional condensation of water vapor effect and the dominant effect of “wet” area accumulation. In the analyzed cases, a decrease in “frost” area accumulation was observed (by 10%) as the relative humidity of the return air increased. Moreover, the presence of a limiting return air relative humidity (for which the dew point temperature is equal to 0°C) was demonstrated, beyond which the non-accumulated “frost” area was partially transformed to a non-accumulated “wet” zone. A significant change in the effectiveness of the device was noticeable when the relative humidity of the return exceeds 30%, which was also confirmed by the maximum size of the “frost” area for this value (about 49%).