INTRODUCTION Several industrial applications of model-based engineering in the development are well known. In fact, the complex algorithms for features such as drive-by-wire and advanced engine management have mandated the use of modeling environment such as MATLAB/Simulink [ 1]. The graphical modeling tools such as Simulink and Stateflow allow the simulation analysis well before the physical prototype is made available [ 2]. Modeling tools let engineers develop algorithms in a flexible and collaborative way, allowing them to explore different aspects of design and test various approaches irrespective of the availability of the physical prototype. Nevertheless, testing on prototyping platform and even the production hardware is indispensable - the modeling tools support the need to produce code for prototype hardware as well as the production hardware. Model-based development environments therefore clearly provide a way to expedite the design of complex embedded control system and certainly have the impetus for shorter design cycles, greater levels of flexibility, lower costs and letting engineers focus on the domain of their expertise.Another widely appreciated aspect of model-based engineering tools is that of letting engineers develop models specific to the several key system functions and test each designed component-based model individually, before integrating models to complete the embedded control system. Component-based software allows for defining component performance specifications, in addition to the system performance specifications. Also, the tuning guides can be developed component-wise. Component-based development lets system level performance issues to be categorized into component centric fixes, resulting in more cost-effective, less invasive, and faster performance resolutions. Furthermore, the software components are reusable and allows for the simultaneous system development by engineers [ 3]. Simulation of the complex designs such as the climate control system, using the graphical modeling tools, let engineers investigate many aspects of design including complexity, interactions between several subsystems, numerical aspects such as overflow and saturation, robustness and sensitivity to parameters and inputs - controlled as well as uncontrolled, etc. Simulation tools such as Simulink/Stateflow allow simultaneous simulation of continuous-time (differential) equations, used for Composite Thermal Model for Design of Climate Control System Rupesh Sonu Kakade General Motors Corp. ABSTRACT We propose a composite thermal model of the vehicle passenger compartment that can be used to predict and analyze thermal comfort of the occupants of a vehicle. Physical model is developed using heat flow in and out of the passenger compartment space, comprised of glasses, roof, seats, dashboard, etc. Use of a model under a wide variety of test conditions have shown high sensitivity of compartment air temperature to changes in the outside air temperature, solar heat load, temperature and mass flow of duct outlet air from the climate control system of a vehicle. Use of this model has subsequently reduced empiricism and extensive experimental tests for design and tuning of the automatic climate control system. Simulation of the model allowed several changes to the designs well before the prototype hardware is available. In addition to the reduced vehicle field tests and wind tunnel tests man hours and the cost associated with them, simulation of the model allowed for the greater potential benefits of increased accuracy and optimized heating and cooling of the passenger compartment to be achieved. An outlook is provided for integrating the composite thermal model of the passenger compartment with the human thermal comfort model to achieve greater benefit of optimized energy use by the climate control system and yet provide the thermal comfort to the occupants. CITATION: Kakade,