Evaluation of the convective heat transfer coefficient of human body and its effect on the human thermoregulation predictions

Jingxian Xu,Agnes Psikuta,Jun Li,Simon Annaheim,René M Rossi

doi:10.1016/j.buildenv.2021.107778

Abstract

Human thermoregulation models, particularly the Fiala model, are well accepted for the prediction of thermoregulatory responses and the assessment of clothing and building systems with regard to human thermal comfort. However, the convective heat transfer coefficients (hc), used for the heat transfer calculations, were obtained from measurements with a thermal manikin with poor body resolution from decades ago, and they were not distinguished between body postures. In this study, the overall and local hc of the human body in both standing and seated postures were evaluated by CFD simulations and implemented in the Fiala model to investigate the resultant influence on the predicted thermoregulatory responses by comparing the predictions with measurements of 14 human exposures. It was found that the original hc used in the Fiala model was similar to the simulated hc of the standing body, but higher than that of the seated body at most body parts. In 64% of the investigated human exposures, the root-mean-square-deviation of the skin temperature predicted by the Fiala model with the simulated hc was lower than that achieved with the original hc, indicating an improvement of the accuracy of the Fiala model. Additionally, the higher hc of the standing body resulted in a lower mean skin temperature by up to 1.5 °C when compared to the seated body in the environment of 10 °C and 2.5 m/s. This emphasises the necessity of ensuring the accuracy of the hc in the thermoregulation model in order to improve its validity for specific investigated conditions.

Highlights

The human thermoregulation model, in combination with the ther mal sensation model, is an efficient tool for predicting human thermal responses, especially in hazardous environments where human tests are not feasible [1,2]
A database of the overall and local hc of standing and seated human bodies was developed in the current study using validated CFD model ling
It was incorporated into the Fiala model for predicting human thermal physiological responses

Summary

Introduction

The human thermoregulation model, in combination with the ther mal sensation model, is an efficient tool for predicting human thermal responses, especially in hazardous environments where human tests are not feasible [1,2]. According to the study by Koelblen et al [6], a deviation of 1 ◦C in the mean skin temperature and/or 0.2 ◦C in the core temperature would cause a variation of 3 units and 1.1 units in the predicted vote for thermal sensation by the Thermal Sensation (TS) model by Zhang [7,8] and the Dynamic Thermal Sensa tion (DTS) model by Fiala [9], respectively, which is higher than the generally accepted error of 1 unit or below [6] This indicates the great necessity of improving the accuracy of the physiological parameters predicted by human thermoregulation models. In the case of convective heat exchange between the human body and its surroundings, the convective heat transfer coefficient (hc) of the human body is a critical factor for the accuracy of the human thermoregulation model

Methods

Results

Discussion

Conclusion