Reducing CO2 emissions in temperature-controlled road transportation using the LDVRP model

Temperature-controlled transport is needed to maintain the quality of products such as fresh and frozen foods and pharmaceuticals. Road transportation is responsible for a considerable part of global emissions. Temperature-controlled transportation exhausts even more emissions than ambient temperature transport because of the extra fuel requirements for cooling and because of leakage of refrigerant. The transportation sector is under pressure to improve both its environmental and economic performance. To explore opportunities to reach this goal, the Load-Dependent Vehicle Routing Problem (LDVRP) model has been developed to optimize routing decisions taking into account fuel consumption and emissions related to the load of the vehicle. However, this model does not take refrigeration related emissions into account. We therefore propose an extension of the LDVRP model to optimize routing decisions and to account for refrigeration emissions in temperature-controlled transportation systems. This extended LDVRP model is applied in a case study in the Dutch frozen food industry. We show that taking the emissions caused by refrigeration in road transportation can result in different optimal routes and speeds compared with the LDVRP model and the standard Vehicle Routing Problem model. Moreover, taking the emissions caused by refrigeration into account improves the estimation of emissions related to temperature-controlled transportation. This model can help to reduce emissions of temperature-controlled road transportation.     

二甲醚用作汽车空调制冷剂的实验研究

根据二甲醚的热物理性质对二甲醚的制冷循环性能进行了分析,并在R134 a汽车空调系统上对二甲醚的制冷性能进行了测试。结果表明:由于二甲醚的气相和液相黏度都比较小,使用二甲醚作为制冷剂可以减小系统的阻力,有利于系统制冷性能的提高。二甲醚可以直接灌注式替代R134 a,但会造成蒸发器出口过热度降低,需对膨胀阀弹簧预紧力进行调整,才能充分发挥二甲醚的制冷性能。     

Experimental study on performance of automotive air conditioning system using R-152a refrigerant

Recently, as climate changes have manifested worldwide, every country is making efforts to prevent ozone depletion and global warming. In the automotive industry, R-134a refrigerant is widely used in air conditioning systems because it has zero ozone depletion potential (ODP). Unfortunately, its global warming potential (GWP) is high. Therefore, alternative refrigerants are needed as a replacement for R-134a. R-152a is considered to be one of the better alternative refrigerants due to zero ODP and low GWP. In this paper, the performance of an automotive air conditioning system using R-134a and one using R-152a are compared experimentally at the bench level. The experimental apparatus simulated a real automotive air conditioning system consisting of a cabin and engine room structure. The cooling capacity, condensing capacity, coefficient of performance (COP) and power consumption characteristics of the automotive air conditioning system are evaluated by changing the air velocity entering the condenser and the compressor rotation speed with the optimized refrigerant charge amount. Also, the performance of the R-152a system was investigated by changing the thermostatic expansion valve which is set of values. The results of this study show that the R-152a system is slightly better than the R-134a system, not only under driving conditions but also under idling condition. R-152a refrigerant thus shows promise as an alternative refrigerant to replace the current standard, R-134a, in automotive air conditioning systems.     

制冷剂/压缩机油与PA6的相容性研究

采用红外光谱分析和热重分析研究了不同规格PA6(聚酰胺6或尼龙6)的区别,不同规格PA6的红外谱图有细微区别,PA6在350℃之前的热失重量不同,可见其增塑剂等小分子的含量不同,这不但影响PA6的耐热老化性能,还会明显影响PA6的挤出工艺和使用性能。通过PA6在制冷剂、压缩机油、制冷剂/压缩机油等介质中的热老化测试和测试后试样的热重分析,对比了不同PA6的体积变化和热失重曲线,结果表明不同规格的PA6与制冷剂/压缩机油等介质的相容性不同。同一规格的PA6在不同的制冷剂/压缩机油中体积变化不同,R1234yf/POE(2,3,3,3-四氟丙烯/多元醇脂)体系中体积变化率最小,并且在不同的制冷剂/压缩机油共混体系对PA6性能的影响中制冷剂起决定性作用。