The passenger thermal comfort has been an important subject for the automotive industries. Energy Efficient HVAC (Heating Ventilation and Air Conditioning) Systems is getting significant attention from the automotive industry to improve fuel economy of their vehicles, and to conform to tighter CAFE (Corporate Average Fuel Economy) standards. 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.

TAITherm, a commercially available software is capable 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. The human physiology model uses multiple body segments and each segment is modeled as either four or five tissue layers or 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 VTCE tool can simulate the occupant skin and core temperatures under various thermal environments. It includes solar radiation, mean radiant temperature, local air velocity, air temperature, and humidity. The present study shows the analysis of human thermal system using Human Thermal Module in TAITherm software. A sitting human model is used for simulation with 21 parts which includes face, head, neck, chest, back, left hand, right hand, left upper arm, right upper arm, left lower arm, right lower arm, left shoulder, right shoulder, left thigh, right thigh, left lower leg, right lower leg, left foot, right foot, upper abdomen and lower abdomen. Metabolic heating is distributed throughout the muscle tissues by distributing heat equally due to work among all of the body's muscle tissues. Clothing is applied to the whole body with appropriate material and measurements. Convection coefficients were given as, flow speed= 0.05 m/s, environment temperature= 20 C fluid temperature= 30 C, and relative humidity= 40%.