Computational model of the heating system
Keywords:heating pump, fluid flow rate, convective heat transfer.
The primary objective of smart heating systems is to maintain a comfortable temperature in the rooms.
The aim of our paper is to propose a method for increasing electric efficiency of older houses heating systems by making simple changes in heating pumps. It has been demonstrated that appropriate start-stop control of the pump may result in significant reduction of the overall pump operation time.
The boiler is assumed to be an ideal one, the temperatures of which are always constant and equal (60ºC) at the zones of connection of the supply and return pipes. In this model the temperature of the heated space (HS) is assumed to be uniform throughout its volume. The temperature of the HS is influenced by the heat exchange processes through its outer surface, as well as, through the surface of the heater in contact with HS. The heat conductivity and surface convection coefficients of the heater are assessed by assuming it as an equivalent pipe. The transient heat transfer problem is solved under assumption that the heating fluid flow rate is a known time function. The aim of the analysis is to find the time law of the fluid flow rate, which ensures minimum power consumption by the pump. Steady temperature of HS within given tolerances must be maintained.
The relationships of the steady temperatures in the heated space against the <pump off> time part during the period at different temperatures of the boiler are presented in diagram. The curves demonstrate that the decrease of temperatures of the HS due to the decrease of the average flow rate is almost independent on the temperature of the boiler, until the <pump on> time part during the pulse time period is not less than 1/4.