Enthalpy-based automatic temperature control for automobiles

Abstract

This paper studies the temperature control for an automobile air-conditioning (AC) system, especially the control of air flow rate in the circulation. Based on energy balance and mass conservation laws, the control strategy is proposed by analyzing the heat exchange between heat gains form outdoor environment and the AC equipment. To be more precise, sensible heat exchange characterized by room sensible heat factor (RSHF) responses to the change in temperature; whereas latent heat exchange characterized by apparatus sensible heat factor (ASHF) responses to the variation in humidity. The problem of temperature control is to assess not only the sensible heat transfer, resulting from the mismatching between RSHF and ASHF while the system attains its equilibrium state, but also the extra cooling load while the system is on the transient stage. Simulation results show a good agreement that the car compartment condition will converge into the comfort zone defined by ASHRAE Standard, regardless of initial conditions.