Analysis of vehicular cabins’ thermal sensation and comfort state, under relative humidity and temperature control, using Berkeley and Fanger models

Abstract

This manuscript discusses the effect of manipulating the Relative Humidity (RH) along with the Dry Bulb Temperature (DBT) on vehicular cabins’ environment in terms of the overall thermal comfort and human occupants’ thermal sensation. The study uses the Berkeley and the Fanger models to investigate the human comfort through analyzing the (RH) effect from three specific perspectives; firstly its effect on other environmental conditions such as the Dew Point Temperature (DPT), the Enthalpy (H), the vapor pressure (vp) and the humidity ratio (ω) in the cabin. This will be done during the summer and winter periods. Secondly, the cabin local sensation (LS) and comfort (LC) will be analyzed for different body segments mainly; the head, chest, back, hands and feet with the addition of the overall sensation (OS) and the overall comfort (OC). This will be done using a thermal manikin based on the Berkeley model. Thirdly, the human sensation will be measured by the Predicted Mean Value (PMV) and the Predicted Percentage Dissatisfied (PPD) indices during the summer and the winter periods using the Fanger model calculations. From this study and according to the Berkeley model; the RH value should be controlled and synced with the cooling process such that at the early stage (rapid transient) low RH value should be enforced; while a high RH value is needed in the steady state phase. During the start of the heating process (winter conditions), the RH value does not play a major role due to low temperature in the passenger compartment. However, at later periods until the end of the heating process, a low RH value is needed to achieve the needed comfort level. According to Fanger model, in the summer period as the RH value increases, the A/C can achieve the human comfort zone ( PMV = ∓0.5) in lesser time than if the RH value is not controlled. While in the winter period, as the RH value decreases, the A/C reaches the human comfort zone faster. So, this study shows that controlling the relative humidity along with (DBT) enables the cabin to reach the comfort zone faster than the sole control of the cabin (DBT), in both the cooling and the heating processes i.e. summer and winter conditions respectively.