青藏铁路空调列车车体围护结构非稳定传热分析

Analysis on the Unsteady Heat Transfer of the Compartment Enclosure

考虑青藏铁路沿线的特殊气候条件及运行列车车体围护结构的热惰性,利用非稳定传热理论编程计算列车运行中车内外相关参数及车体围护结构的传热量,并与不同计算基准温度下稳定传热计算结果进行比对。对青藏铁路,太阳辐射对车体围护结构外表综合温度影响显著,而且不同车次各朝向的车体围护结构外表综合温度波的变化趋势差异较大,这主要是由于车体不同部位在不同时刻接受到的太阳辐射强度不同;对青藏铁路绝大部分区段,用非稳定传热计算方法所得到的车体围护结构传热量均大于同样计算条件下用稳定传热计算方法得出的结果,说明原设计中采用稳定传热计算方法按照设计日最高温度确定的车体围护结构传热量冷负荷偏小,这虽然有利于空调制冷节能,但却增大了供暖能耗。采用非稳定计算方法分析车体围护结构传热,可为列车空调制冷系统的运行调节、改进供氧系统与空调系统的协作方式以及能耗分析、提高青藏铁路列车车内环境参数的控制精度提供更准确的依据。

Based on the special climate conditions of Qinghai-Tibet Railway and the thermal stability of the enclosure of running train compartment, unsteady theory in program compiled for the study was adopted to calculate the inner and outer parameters and the heat transfer through the enclosure of train compartment. Moreover, the quantity of unsteady heat transfer was compared with that using steady method based on different outer calculating temperatures. In Qinghai-Tibet Railway, the outer surface synthesis air temperature of the compartment enclosure is affected remarkably by solar radiation. But also, there are very distinct characteristics for outer surface synthesis air temperature curves of the compartment enclosure of different trains which run towards opposite direction, which is mainly resulted from different intensity of so-lar radiation accepted by different parts of the train at different times. In most sections of Qinghai-Tibet Railway, in terms of heat transfer quantity of compartment enclosure, values obtained by unsteady heat transfer calculation method are higher than those by steady heat transfer calculation method under the same calculation condition. It shows that the cooling load of the compartment enclosure using steady method based on the highest temperature of the designing day in the original design is relatively lower. Although it is beneficial to energy conservation of air-conditioning, the heating energy consumption is therefore increased. Analysis on the heat transfer of compartment enclosure using unsteady calculation method can provide more concrete and accurate data for adjusting the running condition of air-conditioning and refrigeration systems, modifying the cooperation modes between the oxygen system and the air-conditioning system, improving the control precision of the inner environmental parameters and reasonably evaluating the energy consumption of the train in Qinghai-Tibet Railway.