Simulation Study on Active Air Flow Distribution Characteristics of Closed Heat Pump Drying System with Waste Heat Recovery

Abstract

A tridimensional turbulent flow model is established for a closed heat pump drying system with waste heat recovery to improve the drying air flow characteristics and reduce the energy consumption of air circulation. The active flow distribution mode is introduced to guide air flowing in the system’s drying cabinet, top air duct, mixing zone, and heat pump. It is found that the wind velocity in the cabinet’s supply channel is greater than that in the return channel, the velocity distribution in the top duct is uneven, and the outlet velocity of the bypass fan is high and a vortex forms. A partition panel added in the top duct and modulating fans in the drying cabinet are proposed to solve these problems. The simulation results show that removing the circulating fan, changing the volume flow of the bypass fan, adopting the alternative operation mode of the bypass fans, reducing the air volume flow of the supply fan, and reducing the total pressure of the fans can improve the dry air velocity uniformity in the drying cabinet and reduce the energy consumption of the fans. This paper analyzes the closed-loop drying air flow characteristics of the active flow distribution system in the heat pump drying system, which lays a foundation for the wind velocity, temperature, and humidity regulating of heat pump drying system with waste heat recovery.

Temperature Field Simulation and Energy Analysis of a Heat Pump Tobacco Bulk Curing Barn

“…Accordingly, the energy consumption of the curing barn can be calculated under the assumption that both curing barns have the same heat dissipation. Then the thermal efficiency of TCCB and HPCB systems can be calculated using the following expressions [23]: (10) where η is the thermal efficiency of the curing barn, %, E exergy is the useful energy for the energy consumption of the oven, kJ; E energy,TC is the total energy consumption of TCCB, including coal and electricity consumptions, kJ; h fg is the latent heat, J/kg; m wi is the actual amount of water removed per unit time from tobacco leaves, kg; q 1 is the low calorific value of standard coal, which is 29,295 kJ/kg; Q TC is the power consumption of TCCB, kWh; q 2 is the conversion coefficient of electric energy and heat energy, which is 3600 kJ/kWh; E energy,HP is the total energy consumption of HP curing barn, kJ; Q HP is the power consumption of HPCB, kWh; COP is the cycle performance coefficient of the heat pump. In this study, COP = 2.5.…”

“…To solve the problem, numerous investigations have been carried out to achieve an even temperature distribution in the barn. In this regard, different algorithms and analytical methods have been proposed [7][8][9][10]. Recently, replacing coal with methanol and biomass has become a research hot spot [11][12][13].…”