Numerical Study on Accumulative Effect Owing to Heat Storage by Building Envelopes in HVAC Systems

Abstract

In this paper, an accumulative factor was defined to quantify the accumulative effect caused by heat storage by building envelopes in heating, ventilating, and air-conditioning (HVAC) systems. This factor was calculated using a novel model that was developed using the harmonic reaction method, the heat balance method, and a heat storage coefficient. Furthermore, simulations by EnergyPlus and experiments for three case walls (Wall E1, Wall E2, and Wall E3) were conducted under different outdoor conditions to determine the accumulative effect and verify the new model. The results show that the model can effectively evaluate the accumulative effect: when the outdoor temperature is below and above 10°C in the winter, the inner surface temperature and the indoor air temperature of the case walls vary greatly. A small slip region in the inner surface temperature curve appeared for one cycle. The accumulative factor ranged from 0.67 to 0.99 for the case of Wall E1, and the variation in the indoor air temperature was ±1°C. The novel model that is developed in this paper simplifies the calculation of the accumulative effect and improves the accuracy of the calculated cooling and heating load in HVAC systems.