Exhaust gas from automobile can be used to drive adsorption cooling based air conditioning system for the vehicle cabin. This study describes the thermodynamic framework of a two stage indirect exhaust heat recovery system of automotive engine and an effective lumped parameter model to simulate the dynamic behaviors of an adsorption chiller that ranges from the transient to the cyclic steady states. Silica gel and water are used as adsorbent - adsorbate pair. The adsorption chiller model is developed from the rigor of mass and energy balances of each components of the system employing the experimentally confirmed isotherms and kinetics data of silica gel-water system. The performances of the chiller are calculated in terms of COP (Coefficient of Performance) and SCP (Specific Cooling Power) for different operating parameters such as cycle time, switching time, exhaust gas temperatures and flow rates. From the simulation, it is found that the exhaust energy of a six cylinder 3000 cc private car is able to produce enough cooling power for the car cabin. It is also observed that the driving heat source temperature of the adsorption cooling system does not remain constant throughout the cycle time rather it varies in the range depending on the design of the heat recovery system. The optimized COP and SCP of cooling system are found to be 0.47 and 0.25 kW/kg, respectively.
Keywords: Adsorption Chiller, COP, Silica gel – water, SCP