A virtual thermostat for local temperature control

• A virtual thermostat is developed to control the temperature of a specific zone in a HVAC controlled space.
• The average temperature in a specific zone is calculated using computational fluid dynamics (CFD).
• It is shown that a locally controlled temperature system improves energy saving, thermal comfort, and system stabilities.

Conventional HVAC thermostats use a single temperature sensor at one fixed location in a controlled space to control the temperature of the whole space. However, in most applications only a small zone in the controlled space need to be controlled (for example where the people are located). Heating and cooling of the unnecessary zones lead to extra energy consumption that can be saved if only the required zones are controlled. Such a control system requires knowledge of the temperature distribution in the whole zone at all times. In this work, we have used computational fluid dynamics (CFD) to determine the distributive temperature inside the controlled space at all times and turn the HVAC system ON and OFF based on the temperature of the desired zone in the space. In this case, since the distributive temperature is not directly measured, and it is only calculated, the control system is referred to as a virtual thermostat for local temperature control. In this study, we have determined the energy savings by comparing the energy consumption of a thermostat controlled system with a locally controlled one. Several cases with different heat losses, and different inlet air velocities and directions are studied. Energy savings of more than 22% is realized for the cases studied here.