The high thermal management energy consumption is a crucial reason for the severe driving range degradation of electric vehicles (EVs) at low temperatures. Currently, heat pumps and waste heat recovery technology have been widely used to improve the energy efficiency of thermal management systems and alleviate the driving range degradation of EVs in low-temperature environments. However, the conventional waste heat recovery heat pump, with the ambient air and waste heat as heat sources, operates at a single evaporation temperature, resulting in poor performance of the heat pump at low temperatures because the low-energy-grade ambient air source limits the recovery efficiency of the high-energy-grade waste heat. To address the issues, in this study, a thermal management system with dual-evaporation temperature for EVs, which can switch between the single-evaporation temperature and the dual-evaporation temperature modes to match the energy grade of the ambient air and waste heat sources, is proposed. A simulation model of the proposed system is established and validated. The appropriate compressor volume ratio, the heating performance under different operation modes, the energy-saving operation strategy adapted to different operating conditions, and the energy-saving and range extension effect of the proposed system are investigated. The results indicate that the heating energy consumption in dual-evaporation temperature mode can be reduced by 25.2 % and 9.5 % compared to that in single-air source mode and single-evaporation temperature mode, respectively, at −10 °C with waste heat of 1500 W. In Beijing, the proposed system and operation strategy can achieve an average heating energy saving of 14.2 % and an average driving range extension of 12.4 % under HWFET, compared with the conventional thermal management system without waste heat recovery.

Faced with an increasingly severe energy problem and increased demand for indoor comfort, heat recovery VRF systems have demonstrated remarkable potential for energy conservation. However, traditional heat recovery VRF systems need more suboptimal energy efficiency in terms of cooling and dehumidification and fail to guarantee precise temperature and humidity control in specific environments. In this study, a novel heat recovery VRF system that can achieve highly efficient cooling while ensuring precise humidity control is proposed. It can realize four primary operation modes by changing the function of indoor heat exchangers. The results showed that the optimal volume ratio of the two compressor cylinders was 1.4, which was used as the design parameter for the system. Compared to the single-evaporation temperature system, the proposed doubleevaporation temperature system has better energy efficiency and dehumidification capacity in the cooling mode. The cooling coefficient of performance (COP) can be increased by 3.18 %-6.05 %, the compressor energy consumption can be reduced by 3.07 %-7.03 %, and the moisture extraction rate and latent heat ratio of the system can be increased by 5.6 %-33.3 %.

Driving range degradation is a critical issue limiting the wide promotion and application of battery electric vehicles (BEVs). Quantifying the impact of various factors on the driving range by analyzing vehicle energy flow is of vital significance for developing improvement technologies to alleviate driving range degradation of BEVs, which is not addressed in previous studies. In this study, a whole-vehicle energy model is established to simulate the energy flow and driving range of BEVs under different ambient temperatures and driving cycles for quantitative analysis of the various factors (including battery output, thermal management energy consumption, and net driving energy consumption rate) contributing to driving range degradation. The results indicate that the driving range under WLTC (Worldwide Harmonized Light Vehicles Test Cycle) is reduced by 53.1 km compared to CLTC-P (China Light-duty Vehicle Test Cycle for Passenger Cars) at 25 degrees C, which is mainly caused by the increased net energy consumption rate for vehicle driving. Besides, under CLTC-P, the increased thermal management energy consumption leads to a driving range degradation of 79.7 km, 102.2 km, 116.1 km, and 139.0 km at 32 degrees C, 35 degrees C, 38 degrees C, and 42 degrees C, respectively. Moreover, the driving range degradation percentage under CLTC-P at -7 degrees C is 45.9 %, of which 16.0 % is caused by the reduced battery net output energy and 28.5 % is caused by the increased thermal management energy consumption. The investigation provides theoretical support and data basis for the research and development of driving range extension technologies and strategies of BEVs.

The development of electric vehicles (EVs) is of great significance to carbon emissions reduction; however, range anxiety is a major obstacle in the promotion of EVs. Utilizing fresh air under appropriate operating conditions for cooling or dehumidification can reduce the energy consumption of air conditioning (AC) systems for EVs, which has the potential to extend the driving range. In this study, two fresh air utilization strategies for AC systems of EVs are proposed. The AC energy consumption and the resulting driving range degradation of an EV throughout the year with traditional and proposed fresh air control strategies are calculated, moreover, the effects of the proposed strategies on AC energy-saving and driving range extension are discussed through comparative analysis. The results indicate that the fresh air mode optimization strategy can save the energy consumption of AC systems by 11.3% and 18.8% and improve the driving range degradation by 10.2% and 18.0% in summer and transition seasons, respectively, compared with the minimum fresh air volume strategy. Additionally, the energy consumption of the AC system and the driving range degradation using the fresh air volume optimization strategy are reduced by 35.3% and 32.6% in winter compared with the minimum fresh air volume strategy.

电动汽车能实现节能减排与蓄能调峰,其推广应用对于我国"双碳"战略目标的实现具有重要意义.针对现有电动汽车热管理系统尚存在换热流程复杂、系统能效低、难以轻量化集成等问题,本文中提出基于三介质换热器的电动汽车热管理系统,通过样机实验测试建立了三介质换热器计算模型,并结合电动汽车负荷模型与热泵模型建立了三介质换热器电动汽车热管理系统性能模型,分析该系统在不同工况下的运行特性,并与现有典型热管理系统方案进行性能对比.结果表明,在夏季36℃、60 km/h工况下,三介质换热器热管理系统相较于现有的采用风冷冷凝器、液冷冷凝器的热管理系统分别节能2.3%、15.1%;在冬季0℃、60 km/h工况下,采用舱外、舱内三介质换热器进行余热回收时,分别比不采用余热回收的系统节能5.9%、19.7%.

With the rapid development of radiant floor heating in residential buildings, high-temperature water for radiators and low-temperature water for radiant floor heating are needed simultaneously. As a renewable energy solution, the geothermal district heating system(GDHS) is used. In this paper, a GDHS supplying dual-temperature hot water for radiators and radiant floor heating is proposed based on absorption heat pumps(AHP-GDHS). The mathematical model of AHP is verified and the AHP-GDHS system is constructed for design application. The influence of geothermal water supply temperature and heating load ratio of radiators on the performance of AHP-GDHS are explored. Finally, GDHS using heat exchangers for dual temperature supply(HX-GDHS) is compared with AHP-GDHS. Results show that AHP-GDHS has advantages in terms of energy utilization and the payback period is 3.77 years. The proposed GDHS which can supply two kinds of hot water temperatures will benefit the district heating system which exists different heating terminals.

The replacement of internal combustion engine vehicles with electric vehicles is gradually becoming an important development direction of the automotive industry because of the increasingly serious environmental problems and climate change. The high energy consumption for heating and dehumidification of heat pump air conditioning system leads to the reduction of the driving range of electric vehicles in winter. In this study, a simulation model of the heat pump air conditioning system for electric vehicles is established to analyze the operating performance in various air circulation modes under different ambient conditions. The results show that the energy consumption of the outside air circulation mode is 34.4% higher than that of the recirculated air circulation mode under the typical winter condition in cold zone, and the energy consumption of the outside air circulation mode is reduced by 17.1% compared with the recirculated air circulation mode under the typical winter condition in hot summer and warm winter zone. The energy consumption of the heat pump air conditioning system for electric vehicles can be reduced by reasonably controlling the air circulation mode based on the ambient condition on the premise of meeting the requirement of temperature and humidity in the cabin. The control strategy for the energy-saving operation of the heat pump air conditioning system for electric vehicles in winter is proposed and shown in the ambient air psychrometric chart through regional division. And the energy-saving operation mode of the heat pump air conditioning system for electric vehicles in winter for different climatic zones and the number of passengers in the cabin are discussed.

With increasingly serious environmental and energy issues, efficient and environmentally friendly electric ve-hicles have received more attention. However, the high heating and dehumidification energy consumption of their air conditioning system reduces their driving range in winter, giving passengers and drivers range anxiety. In this study, a dual-evaporation temperature heat pump system is proposed to reduce the energy consumption of electric vehicle air conditioning systems in winter, and a simulation model of the proposed system is developed. First, the volume ratio of the dual-cylinder compressor is optimized. Subsequently, the performance of the proposed system in various operation modes under different ambient conditions is compared. The results indicate an optimized volume ratio of 2.85, which is taken as the system's design condition. The dual-evaporation temperature heating dehumidification mode shows superior performance compared with the conventional mode under typical winter conditions in three different climatic zones. Moreover, energy consumption can be reduced by reasonably controlling the operation mode based on ambient conditions. An operation strategy for the dual-evaporation temperature heat pump system in winter is proposed through the regional division of the psychrometric chart, and the energy-saving operation mode of the system is analyzed for different climate zones in China.

Range attenuation in winter is a major obstacle to the promotion and application of electric vehicles in cold regions. To improve the heating capacity and reduce the energy consumption of the air conditioning system for electric vehicles, power components waste heat recovery is currently widely used. However, how to utilize waste heat more efficiently based on the waste heat grade has not been investigated previously. In this study, the simulation model of the heat pump system for electric vehicles is established, and the performances of different waste heat utilization methods are compared. The result shows that the high-grade waste heat of the motor should be directly used for secondary heating, and the low-grade waste heat of the battery should be used as the heat source for the heat pump. Besides, improvement measures should be taken to avoid a low battery temperature under low ambient temperature and low waste heat conditions.

探明房间空调器的实际运行性能对于优化其控制策略、降低运行能耗和运行费用具有重要意义.首先系统地总结了空调器现场运行性能测量技术发展现状,指出压缩机能量平衡法(CEC法)能够满足现场性能测量非介入式、无干扰性且精度适宜的要求,是一种切实可行的长期在线性能测试方法.针对压缩机CEC法必须解决传感器位置固定与制冷剂状态参数动态变化、压缩机性能衰减与长期较高精度测量的矛盾,分析了基于CEC法动态修正的"全工况制冷剂流量法"的实现方法;总结了国内外空调器在线性能测量标准,并重点介绍了国内在线性能测量仪表精度的标定方法;在此基础上,通过典型案例给出空调器的在线性能测量结果,并分析其运行特征、能效现状和在线性能测量技术的发展趋势.