MATHEMATICAL-MODEL OF HEAT-RECOVERY IN A SPACE-HEATING AND VENTILATION SYSTEM

Proper selection of a control scenario is essential for efficient management of energy systems which provide space heating and local ventilation to buildings. Using the steady-state, bottom-up approach, we have developed a mathematical model and the software AZMA to analyze the efficiency of energy recovery by using 13 different energy-control scenarios. In this analysis, we have introduced a coefficient of transfer of recovered heat, the coefficient of thermal comfort and also cost ratings for different controls and scenarios. In general, the recovered energy is not equal to the energy saved. Depending on the control scenario and size of the recovery heat exchanger (RHE), the transfer of recovered energy to the energy system may generate energy losses rather than energy savings, which may impair the thermal comfort of the building space. Results show that good energy savings can be obtained not only for scenarios with size control (SC) of space heaters but also for valve control (VC), which is much less costly than SC.