PMV model is insufficient to capture subjective thermal response from Indians

Abstract

A controlled laboratory experiment was carried out on forty Indian male college students for evaluating the effect of indoor thermal environment on occupants' response and thermal comfort. During experiment, indoor temperature varied from 21 °C to 33 °C, and the variables like relative humidity, airflow, air temperature and radiant temperature were recorded along with subject's physiological parameters (skin (Tsk) and oral temperature (Tc)) and subjective thermal sensation responses (TSV). From Tsk and Tc, body temperature (Tb) was evaluated. Subjective Thermal Sensation Vote (TSV) was recorded using ASHRAE 7-point scale. In PMV model, Fanger's Tsk equation was used to accommodate adaptive response. Stepwise regression analysis result showed Tb was better predictor of TSV than Tsk and Tc. Regional skin temperature response, suppressed sweating without dipping, lower sweating threshold temperature and higher cutaneous threshold for sweating were observed as thermal adaptive responses. These adaptive responses cannot be considered in PMV model. To incorporate subjective adaptive response, mean skin temperature (Tsk) is considered in dry heat loss calculation. Along with these, PMV-model and other two methodologies are adopted to calculate PMV values and results are compared. However, recent literature is limited to measure the sweat rate in Indians and consideration of constant Ersw in PMV model needs to be corrected. Using measured Tsk in PMV model (Method1), thermal comfort zone corresponding to 0.5 ≤ PMV ≤ 0.5 was evaluated as (22.46–25.41) °C with neutral temperature of 23.91 °C, similarly while using TSV response, wider comfort zone was estimated as (23.25–26.32) °C with neutral temperature at 24.83 °C, which was further increased to with TSV-PPDnew relation. It was observed that PMV-model overestimated the actual thermal response. Interestingly, these subjects were found to be less sensitive to hot but more sensitive to cold. A new TSV-PPD relation (PPDnew) was obtained from the population distribution of TSV response with an asymmetric distribution of hot-cold thermal sensation response from Indians. The calculations of human thermal stress according to steady state energy balance models used on PMV model seem to be inadequate to evaluate human thermal sensation of Indians. Relevance to industryThe purpose of this paper is to estimate thermal comfort zone and optimum temperature for Indians. It also highlights that PMV model seems to be inadequate to evaluate subjective thermal perception in Indians. These results can be used in feedback control of HVAC systems in residential and industrial buildings.