Critical analysis of thermodynamic cycle modeling of adsorption cooling systems for light-duty vehicle air conditioning applications

Thermodynamic cycle of adsorption cooling systems (ACS) is thoroughly studied under different operating conditions for light-duty vehicles air conditioning applications. Available ACS prototypes installed in vehicles are discussed in detail followed by different ACS thermodynamic cycle modeling. Also, equilibrium uptake and uptake rate of commonly used working pairs in ACS are summarized. The proper ACS thermodynamic cycle with capability of integration with vehicles׳ Engine Control Unit (ECU) is developed and it is validated against two sets of experimental data reported in the literature. The realistic input data in agreement with light-duty vehicles are introduced to the model as the base-case condition to produce 2 kW cooling power. Sensitivity of ACS specific cooling power (SCP) and coefficient of performance (COP) are studied with respect to the input parameters. According to the results, the SCP and COP of the base-case ACS are maximized at 10-15 min cycle times and adsorption to desorption time ratio (ADTR) of one. In addition, the results indicate that the adsorber bed overall heat transfer conductance and mass have the highest and the lowest effects on the SCP, respectively. Also, the results show that during the operation of ACS, the heating and cooling fluids, coolant fluid and chilled water mass flow rates do not change the SCP and COP after specific values. As a result, variable speed pumps are required to adjust these mass flow rates to reduce feeding pump powers. Finally, the results indicate that the engine coolant cannot provide enough heat for the adsorber bed desorption process under different operating conditions. Therefore, a portion of the exhaust gas of the engine is recommended to be utilized during the desorption process.