The Engineering Meetings Board has approved this paper for publication. It has successfully completed SAE’s peer review process under the supervision of the session organizer. This process requires a minimum of three (3) reviews by industry experts. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. ISSN 0148-7191 Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. SAE Customer Service: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: CustomerService@sae.org SAE Web Address: http://www.sae.org Printed in USA 2010-01-1205 Assessment of Various Environmental Thermal Loads on Passenger Thermal Comfort TAEYOUNG HAN, KUO-HUEY CHEN, BAHRAM KHALIGHI Vehicle Development Research Lab., GM R&D Center, Warren Michigan ALLEN R. CURRAN, JOSHUA J. PRYOR, MARK A. HEPOKOSKI ThermoAnalytics, Inc. Calumet, Michigan Copyright © 2010 SAE International ABSTRACT Virtual simulation of passenger compartment climatic conditions is becoming increasingly important as a complement to the wind tunnel and field testing to achieve improved thermal comfort while reducing the vehicle development time and cost. The vehicle cabin is subjected to various thermal environments. At the same time many of the design parameters are dependent on each other and the relationship among them is quite complex. Therefore, an experimental parametric study is very time consuming. The present 3-D RadTherm analysis coupled with the 3-D CFD flow field analysis takes into account the geometrical configuration of the passenger compartment which includes glazing surfaces and pertinent physical and thermal properties of the enclosure with particular emphasis on the glass properties. Virtual Thermal Comfort Engineering (VTCE) is a process that takes into account the cabin thermal environment coupled with a human physiology model. This model uses multiple body segments and each segment is modeled as several body layers (core, muscle, fat, and skin tissues) and a clothing layer. The UC Berkeley comfort model has the ability to predict local and overall thermal comfort levels of an occupant based on local skin and core temperatures and their time rate of changes. The combination of the present thermal analysis and the thermal comfort evaluations based on the human physiology model will shed light on the climate control strategies as they relate to the occupant thermal comfort for an “Energy Efficient HVAC System”. INTRODUCTION The passenger thermal comfort has been an important subject for the automotive industries. However, the tendency to use more glass in vehicles (styling), tightening fuel-economy constraints, and the changes to the environmentally friendly refrigerants have hampered achieving the occupant thermal comfort. As the automotive industries try to reduce the HVAC power consumption due to the tightening fuel economy, it has become necessary to develop new tools that can predict the impact of various design selections on the passenger thermal comfort early in the design process [1-5]. Thermal comfort is the ultimate goal of the HVAC systems for vehicles. However, assessment of the thermal comfort in a vehicle is very complex due to highly asymmetric thermal environments associated with highly non-uniform air velocity and temperature distributions, localized solar flux, and radiation heat load from the windshield and instrument panel. A passenger compartment thermal analysis tool coupled with the thermal comfort predictions can guide design directions during the early stage of vehicle development process. During the past two years, the University of California at Berkeley has collaborated with GM R&D Center and TAI (ThermoAnalytics Incorporated) to develop the capability of predicting passenger thermal comfort to support vehicle climate control systems. At the core of this Virtual Thermal Comfort Engineering (VTCE) tool is the human physiology model coupled with the thermal sensation and comfort correlations developed by UC Berkeley based on the large number of human subject tests [6-8]. The human physiology model uses multiple body segments and each segment is modeled as either four or five tissue layers (typically, core and/or bone, muscle, fat, and skin tissues) and a clothing layer. The UC Berkeley comfort model has the ability to predict local and overall thermal comfort levels of an occupant based on the local skin and core temperatures and their time rate of changes. The details of the UC Berkeley