车外综合温度条件下典型冷藏车厢内热稳定性研究

Thermal Stability of Typical Refrigerated Trucks Compartment under Outdoor Sol-air Temperature Conditions

综合考虑太阳直射辐射、天空散射辐射、地面反射辐射、室外空气温度及车辆运行速度多个因素,采用2阶谐波傅氏级数表达的车外壁面温度函数作为车厢外侧的边界条件,利用热工理论分析与试验验证相结合的方法,分析4种典型冷藏车隔热车厢对温度的衰减与延迟作用,以及厢内热稳定性的影响。结果表明:车厢的隔热材料不同,对车外综合温度的延迟时间与衰减倍数不同,厢体热惰性指标、热阻越大,延迟时间与衰减倍数相应越大;车辆行驶方向、隔热材料不同,车厢体内壁面温度也不同,但都按照正弦规律波动变化,且厢体内壁面温度逐时变化值接近厢内设定空气温度。车厢内的热稳定性主要由厢体隔热材料的热阻与热惰性指标决定,由好到差依次为真空绝热材料厢体、挤塑聚苯乙烯厢体、聚氨酯隔热厢体、聚苯乙烯隔热厢体。

Considering the factors of direct solar radiation, sky diffuse radiation, ground reflected radiation, outdoor air temperature, and the vehicle speed, compartment outdoor wall surface temperature function with two-order harmonic Fourier series expression was used as a boundary conditions. The effect factors of time lag, decrement, and thermal stability upon four kinds typical refrigerated trucks insulation compartment were analyzed by using combined method of thermal theory analysis and experimental validation. The analysis results show that different compartments insulation materials will cause different of time lag and decrement coefficient which increases with the increasing of the thermal inertia index and heat resistance of compartment. Different driving directions and insulation materials will cause different compartment indoor wall surface temperatures accordance with the sinusoidal variation. The compartment indoor wall surface temperature change with time closes to the compartment inner air temperature. The thermal stability inside compartment is determined by thermal resistance and thermal inertia index of insulation material. The order from the best to the worst is VIP compartment, extruded polystyrene composite compartment, polyurethane thermal insulation compartment and polystyrene insulation composite compartment.