Study on the heat and mass transfer characteristics of spray separation tower at low temperature and normal pressure

摘要

A one-dimensional mathematical model for the drying process of calcium chloride solution in a co-current spray separation tower based on the four-stage drying model of single droplet is proposed. A corresponding pilot system is set up and the reliability of the model is validated by a series of experiments. The maximum relative errors of the mathematical model are within 10% and 15% while the average relative errors are 4.0% and 7.0% when predicting the outlet air temperature and humidity, respectively. The effects of inlet parameters on the heat and mass transfer characteristics of the spray separation tower at low temperature and normal pressure are evaluated as well. Simulation results show that air mass flow rate, inlet solution concentration and solution mass flow rate have greater effect on the thermal efficiency than other inlet parameters while the inlet solution concentration plays a pivotal role on the drying strength. The most significant factor on the volumetric heat transfer coefficient is the inlet solution concentration. Besides, the back propagation (BP) neural network model of the spray separation tower is also established on the basis of experimental data, and the comparison between the one-dimensional mathematical model and the BP neural network model is conducted in detail.