Numerical investigation of thermal-hydraulic behaviour in HVAC pipe networks

To investigate the hydraulic and thermal behaviour of the HVAC network under part load condition, the models of the components in the network, such as pipes, valves, pumps, and heat exchangers, are established based on a real HVAC system and incorporated so as to represent the overall behaviours of the system. Corresponding FORTRAN programs are developed. The simulation results of the model reach an agreement with experimental data, with relative error not exceeding 10%. As the thermal load decreases, the dynamic behaviours of some vital variables in the network are quantitatively studied, such as supply and return water temperature, air supply temperature of terminal devices, and total heat exchange rate. The results show that dynamic behaviours of the network exhibit obvious differences, as the thermal load uniformly changes or not.