CFD simulation of a cabin thermal environment with and without human body – thermal comfort evaluation

Paul Danca,Amina Meslem,Ilinca Nastase,Florin Bode,C Balan,M.C Balan

doi:10.1051/e3sconf/20183201018

Abstract

Nowadays, thermal comfort became one of the criteria in choosing a vehicle. In last decades time spent by people in vehicles had risen substantially. During each trip, thermal comfort must to be ensured for a good psychological and physical state of the passengers. Also, a comfortable environment leads to a higher power concentration of the driver thereby to a safe trip for vehicle occupants and for all traffic participants. The present study numerically investigated the effect of human body sited in the driver's place, over the air velocity distribution and over the thermal comfort in a passenger compartment. CFD simulations were made with different angles of the left inlet grill, in both cases, with and without driver presence. In majority of the actual vehicles environment studies, are made without consideration of human body geometry, in this case, the results precision can be affected. The results show that the presence of human body, lead to global changing of the whole flow pattern inside the vehicular cabin. Also, the locations of the maximum velocities are changing with the angle of the guiding vanes. The thermal comfort PMV/PPD indexes were calculated for each case. The presence of human body leads to a more comfortable environment.

Highlights

Thermal comfort is defined by ASHRAE [1] as the condition of mind that expresses physical and psychological satisfaction with the thermal environment
In 1970 Fanger [3] developed in controlled laboratory conditions and with measurement tools available at that time, Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) indexes which further was embraced by thermal comfort standards
We note that the maximum values of the velocity magnitude are rather high compared to the limits of the PMV-PPD models from the standards

Summary

Introduction

Thermal comfort is defined by ASHRAE [1] as the condition of mind that expresses physical and psychological satisfaction with the thermal environment. The thermal non-uniformity of the surfaces directly affects the air flow distributions through convective effects Flow patterns and their effect on thermal sensation are not completely considered by manufacturers or by users, given that flow trajectory might substantially differ from the direction imposed by the guiding vanes of the air vents. Higher velocities was found in the rear part of the compartment at the head and foots level and low temperatures, while in the front part at all the levels air velocity was higher for the first case as well as the temperature values All these previously cited papers show that the global distribution of the air flows inside the vehicular space plays an important role on thermal sensation, directly via the possibility of heat dissipation of the human body and its ambient, and indirectly through the homogeneity of air temperature and velocity distributions. We present in this article, results obtained for the air vent located on the dashboard at the driver’s position (left side air vent)

Assessment protocol

Boundary conditions

Results and discussions

Conclusions