A PMV-based HVAC control strategy for office rooms subjected to solar radiation

Abstract

The user comfort and energy consumption become two conflicting subjectives leading to pareto-optimal control fronts when designing HVAC systems. Although, indoor air temperature has been extensively used as a primary parameter of HVAC control for many years, it is unable to precisely or fully reflect the perceived thermal comfort. And the set-points of thermal comfort sensors for the conditioned space are generally installed far away from occupants, making them unable to detect real occupant sensations. Computational Fluid Dynamics (CFD) simulations can be used to assist with developing the thermal comfort control strategies.A comparative simulation study between the thermal comfort (Predicted Mean Vote, PMV-based) control and conventional temperature (Temperature-based) control is conducted in a typical glazed office room subjected to solar radiation for the entire occupied time of a day. To achieve the control target of ISO 7730 comfort zone, an iterative procedure was developed to estimate the flow rate of the supply air. The air temperature field and ventilation performance in the work plate and the plate crossing through the middle of the office room were shown in two control strategies by CFD. The thermal environment indices (vertical air temperature difference and draught) and energy saving are analyzed and compared under two control strategies. The results demonstrate that the PMV-based control could provide better thermal comfort in highly glazed office room and it still shows a savings of 1.6% per day of energy usage.