Performance Evaluation of a Guarded Hot Box U-value Measurement Facility under Different Software based Temperature Control Strategies☆

Abstract Energy conservation and energy management can be achieved in buildings by reducing the load on the HVAC systems used in the buildings. This is possible by reducing the magnitude of heat flow through the building materials and components such as the windows, ceilings, floors, walls, etc. The thermal performance of a material can be evaluated by measuring its overall heat transfer coefficient or the U-value. The U-value of a material can be measured using the Guarded Hot Box method. The setup comprises of three parts – the metering box, the guard box and the cold box. In this method a constant heat flow needs to be maintained through the test specimen from the metering box to the cold box. Thus it is important to control temperatures in all the three parts accurately. In the present work the temperatures of the metering box and the guard box have been controlled using three different software based temperature control strategies. In the first two strategies on-off control was implemented while in the third strategy proportional control was implemented. From the experimental data it was found that similar performances were obtained in the first two test cases where the temperatures could be controlled satisfactorily. Whereas, in the third case steady state offset was obtained while controlling the metering box temperature and the guard box temperature showed fluctuations.