Effect of flow pulsation on energy consumption of a radiator in a centrally heated building

Currently used central heating systems utilise radiators operating on constant flow with on/off control strategy that consumes significant amount of energy. Therefore, enhancing the thermal performance of central heating systems can play a major role in reducing buildings' energy consumption. This work aims to improve the performance of hot water heating system by changing the radiator inlet flow strategy from constant to pulsed flow without changing the installed radiator or compromising the user comfort. Using the Simulink/Matlab software, a mathematical model of a room with single radiator was developed. This model couples the thermal performance of the radiator, air within the heated space, walls and windows. Pulsed flow with amplitudes ranging from 0.024 to 0.048 kg/s, frequencies ranging from 0.0017 to 0.017 Hz and duty cycles ranging from 50 to 80% were investigated and compared with the constant flow. Results showed that up to 22% of the energy consumed for heating can be saved by changing the constant flow to pulsed flow. In addition to the energy saving achieved using this pulsed flow, the indoor temperature response is also shortened from 600 s for the constant flow case to 450 s. Further improvement was achieved by introducing the proportional integral differential (PID) control system with the pulsed flow where the results showed that the fluctuation in the indoor temperature decreased to ±1 K of the desired temperature of 20ºC and energy saving can be increased to 27%.