Investigation of improvement of desorption efficiency using engine cooling water in natural gas vehicle tank

In natural gas driven vehicles, the endothermic effect during the desorption process in the gas tank not only poses a great impact on the quantity and efficiency of desorption but also affects the vehicle speed and the maximal mileage seriously. To investigate the influence of the thermal effect, this paper firstly establishes a mathematical model for the desorption process based on the conservation equations of mass, momentum and energy, as well as the gas state equation and the adsorption isotherm equation. The solution results of the model show that the average adsorbents temperature in the tank reduces from 293.15 K to 250.46 K due to the endothermic effect. The desorption efficiency decreases by 24.29% compared with that of the isothermal desorption. To mitigate this effect, a heating jacket, which uses the engine cooling water to heat the gas storage tank, is proposed in this paper. The modeling result shows that when the tank is heated by engine cooling water, the average temperature of adsorbents is 273.44 K, which is 26.88 K higher than that in a natural process. When the vehicle speed is 100 km/h, the natural gas mass released by the vehicle storage tank is 3.182 kg, which is 1.163 times of that in the natural desorption.