Electric vehicles (EVs) suffer significant driving range degradation under extreme temperatures due to high cabin conditioning energy consumption. A novel CO2-based thermal management system (TMS) for electric vehicles that incorporates a battery, an electric motor, and a transcritical CO2 heat pump with vapor injection has been proposed. The proposed architecture uniquely combines downstream vapor injection with motor waste heat recovery in a unified TMS, enabling coordinated cabin, battery, and motor thermal regulation year-round. A dynamic simulation model was developed in Amesim. Results show that under summer conditions (35-43 degrees C), the cabin cooling COP decreases from 1.385 to 0.881 with increasing ambient temperature, achieving optimal performance at 5 m/s air velocity and 60% expansion valve opening. At -15 degrees C in winter, vapor injection alone improves heating COP from 1.96 to 2.45 (a 19.7% increase), while additional waste heat recovery further elevates COP to 2.74 (a 17.6% improvement) and reduces compressor discharge temperature by 11.3%. The system maintains battery temperature below 45 degrees C and motor temperature below 70 degrees C across all operating conditions. These findings demonstrate that the proposed integrated CO2-based TMS significantly enhances energy efficiency and component durability for next-generation EVs.

In order to optimise supermarket refrigeration systems, a novel transcritical CO2 system was developed. Simulation results indicate that under high-temperature conditions, the optimal discharge pressure ranges from 9-11 MPa, corresponding to the best COP value of 2-2.4, while receiver pressures above 5 MPa reduce COP by 3.7-4.7%. Advanced exergy analysis reveals the high-pressure compressor has the highest avoidable exergy destruction (12.05 kW at 30 degrees C), followed by the gas cooler and medium-temperature evaporator, indicating significant optimisation potential.

Integrating efficient CO2 heat pumps with solar energy and thermal storage (PSCHP system) supports low-carbon building heating. Using MATLAB-TRNSYS and Hooke-Jeeves optimization, this study analyzes the system’s dynamic performance. The results show that the temperature interactions among system components are well coordinated throughout the heating season: the solar collector output follows solar radiation trends, while the air-source heat pump fluctuates significantly in early and late stages but stabilizes in mid-season. The PCM tank maintains thermal stability of around 58 °C during the mid season, with increased initial and final changes. The buffer tank always reflects the temperature dynamics of the heat pump. The maximum COP of the system in March was 3.21, and the minimum COP in December was 2.07. At the optimal gas injection ratio of 0.3, the heating capacity increased by 80.18 % compared with the case without gas injection. The outlet temperature of the solar collector increased by 18.36 % when the ambient temperature rose from −10 °C to 30 °C, and showed an irradiance-dependent growth of 27.85 %–30.44 % when the solar irradiance increased from 200 W/m2 to 1000 W/m2 under ambient temperatures of 0 °C, 10 °C, and 20 °C. After optimization, the annualized cost was reduced by 15.22 % compared with the baseline design before optimization, and the volumetric storage and discharge capacities of the PCM tank were increased by 14.3 % and 13.5 %, respectively, relative to the pre-optimization configuration.

Heat pump systems for domestic hot water preparation hold great promise under low-temperature conditions. To enhance heat pump system performance, this study proposes a transcritical CO2 quasi-two-stage compression heat pump with an ejector (TCIEJ) and compares it with three other CO2 heat pump cycles. Using Tianjin as a case study, models for energy saving, economic viability, and environmental protection were established to analyze the system's practical application, with comparisons made against R410A heat pumps and electric water heaters. A hybrid evaluation model combining the analytic hierarchy process and entropy weight method was employed to optimize the weight distribution of evaluation indicators and assess the overall performance of the three types of water heaters. Results show that at ambient temperatures of -15-10 degrees C, the TCIEJ system's optimal COP was enhanced by 21.7 % and 37.2 % compared to CO2 heat pumps with expanders and ejectors, respectively. CO2 heat pumps could save 80.4 % and 8.7 % of electricity annually compared to electric water heaters and R410A heat pumps. Additionally, CO2 heat pump water heaters had the lowest pollutant emissions, approximately 80.4 % less than electric water heaters. While CO2 heat pump systems have a slightly higher initial investment cost than R410A heat pumps and electric water heaters, they offer lower operating costs. In the comprehensive evaluation index, a 10 % reduction in the initial investment cost of the CO2 heat pump would lead to optimal overall performance. These findings provide essential theoretical references for enhancing the performance of the TCIEJ system.

Global energy demand continues rising with technological advancement. Renewables like solar and wind are increasingly adopted, yet heating/cooling systems responsible for 40 % of building energy use require urgent efficiency improvements. Heat pumps emerge as key solutions, particularly cascade systems. Refrigerant charge in cascade Heat pumps is critical: overcharging raises costs and leakage risks, while undercharging reduces heating capacity. To investigate the effect of refrigerant charge on the performance of the High-Temperature Cascade Heat Pump (HTCHP) system, a 20 kW HTCHP test rig was constructed. Several experiments were conducted to examine the variations in pressure, power input, heating capacity, and coefficient of performance (COP) with different refrigerant charge amounts in the Low-Temperature End Refrigeration Cycle (LS). An uncertainty analysis was performed to ensure the accuracy and reliability of the experimental results. The findings reveal that the evaporating and condensing pressures in both the LS and High-Temperature End Refrigeration Cycle (HS), as well as the power input of LS, heating capacity, and COP, increased with the refrigerant charge in LS. In contrast, the power input of HS showed little change. The HTCHP COP decreased by approximately 3.25 %-5.77 % as the refrigerant charge in LS increased by 300 g.

As environmental problems become more and more serious, CO2 2 is widely used as a natural work material in heat pump water heaters. In order to better improve the performance of CO2 2 air-source heat pump water heater, a trans-critical CO2 2 quasi-two-stage compression heat pump system with ejector (TCIEJ) is proposed. And a transcritical CO2 2 air-source heat pump water heater experimental bench was built. The effects of parameters such as cooling water flow rate, high pressure and compressor frequency on the performance of the heat pump were tested. A simulation model of TCIEJ was also developed to simulate the system performance. The results show that when the cooling water flow rate is increased from 70 kg/h to 122.5 kg/h the COP is improved by 30 %, while the cooling water discharge temperature is reduced by 15.4 %. System performance can be enhanced by increasing the cooling water flow rate within the temperature range required to meet hot water demand. When the high-pressure pressure of the TCIEJ system was increased from 8.0 MPa to 10.4 MPa, the cooling water discharge temperature increased by 17.66 degrees C on average. Even in the ambient temperature of 0 degrees C high-pressure pressure of 10.4 MPa, the compressor discharge temperature is only 85.77 degrees C. It shows that the combination of make-up air technology and ejectors effectively reduces the compressor discharge temperature, which is conducive to improving the compressor's service life.

Solar-coupled CO2 heat pumps provide an efficient and clean energy solution for building energy supply. A novel solar-coupled CO2 transcritical quasi-two-stage compression heat pump with an ejector system (STQHPE) is proposed and compared to two alternatives: the solar-coupled CO2 transcritical heat pump with an ejector system (STHPE) and the solar-coupled CO2 transcritical quasi-two-stage compression heat pump (STQHP). Simulation models for these systems are developed using TRNSYS software, focusing on building heating and hot water supply. Three evaluation indicators were analyzed: energy efficiency, economy and environment. Increasing the collector area and tank volume enhances STQHPE performance, with its heating seasonal performance factor (HSPF) 1.5 % and 16.5 % higher than STQHP and STHPE, respectively, as the collector area grows. Adjusting the tank volume reduces CO2 emissions. Based on sensitivity analyses found that increasing cooling water flow boosts heat production, with the system's comprehensive performance coefficient (zeta) improving by up to 39.8 %, averaging 65.5 % and 72.1 % higher than STQHP and STHPE across a 6 degrees C-10 degrees C temperature difference. With a collector area of 40-120 m2, the STQHPE's zeta is 25.0 % and 27.5 % higher than STQHP and STHPE. Optimization via the NSGA-II algorithm achieves a Pareto optimal solution, with HSPF of 5.215, annual cost value of 24,902.4 yuan, and CO2 emissions of 19,796.43 kg for collector area of 40 m2, cooling water flow rate of 6 m3/h, and start-stop temperature difference of 5 degrees C. These findings highlight STQHPE as a superior option for building energy supply.

为了研究CO2/HCs混合工质应用于热泵系统的性能,建立单级带节流阀亚临界循环和跨临界循环数学模型,分析了CO2/R170,CO2/R1270,CO2/R290,CO2/RC270 4种混合工质的特性、不同混合工质配比对循环制冷系数COP和高压压力的影响,以及蒸发温度和冷凝温度对循环性能的影响.结果表明:在亚临界循环中,性能最好的是CO2/RC270,COPc峰值为2.92,COPh峰值为3.92,质量比在0.1/0.9左右,COPc和COPh分别比其他2种工质高出了 9％、26％和7.1％、18％.在跨临界循环中,CO2/R1270当质量比为0.96/0.04时,COPc最大值为3.2,COPh最大值为4.2;CO2/R290能有效降低高压压力,当循环的高压压力在7.5 MPa下时,CO2/R290的质量比为0.9/0.1时COP最大,达到2.9,与纯CO2在相同高压压力下相比,COP提高了 93％.

为了提高商超跨临界CO2 制冷循环的性能,对 4 种跨临界CO2 双级压缩制冷循环(TCTC、TCEC、TCRG、TCRG)建立热力学模型.主要分析了高压压力、中间压力、蒸发温度和气体冷却器出口温度等参数对性能系数(COP)的影响.结果显示:在一定条件下,TCEC循环COP相对最高,比基础循环最优高压COP提高49.82%,最优中间压力COP提高 61.41%;TCRC和TCTC循环COP相差无几;TCRG循环COP相对最低.TCRG循环不适用于中低温制冷;TCTC、TCRC循环由于在气冷器出口温度高于37℃后急速下降,不适用于气冷器出口温度较高工况,系统制冷性能受气体冷却器出口温度的影响较大,添加回热器反而降低了系统COP.

目前以自然工质CO2为制冷剂的空气源热泵具有十分优良的应用前景,为挖掘其节能潜力,本文改进了常规的?分析评价方法,采用高级?分析方法对跨临界CO2双级压缩空气源热泵循环进行了深入研究.结果表明:系统的可避免内因?损占比为46.88％,这一部分?损可通过改进系统部件性能避免;从高级?分析角度,低压压缩机、高压压缩机和膨胀机具有最高的优化优先级;高压压缩机的?损占总?损的25.37％,对高压压缩机进行优化可明显提升系统性能;蒸发器的?损全部为自身因素导致的内因?损;节流阀的外因?损和可避免?损为负值,可通过更换其他节流设备提高系统性能;系统存在对应最高?效率的最优高压压力,高压压力从8.00 MPa增大到10.00 MPa时,高压压缩机的可避免内因?损增大了1.96％.

CO2跨临界热泵系统在制冷制热应用方面具有极大的潜能,为了更好地提高该系统的效率,通过实验及仿真对该系统性能进行研究.首先对系统进行了实验测试,然后运用集中参数法建立系统各部件模型,对系统性能进行模拟计算,并与实验值进行对比.分析CO2质量流量、冷却水温度流量对系统制冷性能系数COP和制热性能系数COPh的影响.结果表明:COP/COPh随CO2质量流量、冷却水流量的增大而增加;随冷却水温度的升高而减小.并且加过冷器之后系统的COP和COPh与不加过冷器相比,分别增加了 4.19％和4.62％.同时模拟值与实验值的一致性较好,误差基本在10％以内,从而验证了模型的准确性.研究结果可为系统进一步优化提供理论支持.

为了提高CO2跨临界热泵系统的性能,通过建立热力学模型,将3种带膨胀机的CO2跨临界循环,即单级膨胀机循环(SCE)、双级一次节流中间完全冷却循环(TPCE)、双级二次节流中间完全冷却循环(TSCE)与单级节流阀循环(BASE)进行了制热性能对比分析.结果表明:蒸发温度变化时,TSCE循环的制热系数COPh最大,分别比SCE和TPCE循环平均高出6.32％和10.01％;当气体冷却器出口温度高于37?℃时,SCE循环的COPh最大,低于37?℃时,TSCE性能最好;TPCE和TSCE循环在蒸发温度变化过程中,存在蒸发温度的最优值,对应对基础循环的提升程度ΔCOP最大,TPCE和TSCE循环的ΔCOP最大值分别为27.27％和15.21％;根据假设条件,进而得到了最优高压和蒸发温度和气体冷却器出口温度之间的关联式.

In order to improve the efficiency of the system and promote its application in other industries, the performance of a thermoelectric subcooled CO2 transcritical heat pump system was studied. A simulation model of the system was established using steady-state lumped parameter technology, and the experimental data were compared with the simulation results. The effects of cooling and chilled water flow rate and temperature, subcooling degree, compressor discharge pressure on the coefficient of performance (COP), and heating coefficient of performance (COPh) were analyzed. The results showed that COP/COPh increased with the increase in cooling and chilled water flow rate and chilled water temperature and decreased with the increase in cooling water temperature. The experimental COPh and COP of the system with a thermoelectric subcooler increased by 4.19% and 4.62%, respectively, compared to the system without it. The simulated data was in good agreement with the experimental data, and the error was within 10%, thus verifying the correctness of the model. When the subcooling degree increased to 11 °C, the system simulation results showed that COP/COPh increased by about 40% and 13.3%, respectively. The optimal high pressure was about 8.0 MPa, which corresponded to the maximum COP and COPh of the system of 3.25 and 4.25, respectively. The research results can provide a theoretical basis for future system optimization.

为了比较供暖装置在不同气候条件下的性能,建立了能耗、经济和环保性模型,分析了CO2跨临界空气源热泵(ASHPCO2)、R410A空气源热泵(ASHPR410A)、燃气壁挂炉(WGH)以及电加热取暖器(DEH)4种供暖装置.结果表明:ASHP CO2的能耗较低,相比DEH的能耗最大减少了81.2％;ASHP R410A和WGH的经济性较好,相比DEH的运行总成本分别最大减少了60％和52.1％;WGH的环保性最佳,其次是ASHPCO2,ASHPCO2在上海的PM2.5排放量比DEH低75.2％;除长沙以外,4种供暖装置的能耗、运行成本及污染物排放量均随地区纬度的降低而降低;ASHP CO2在上海地区的能耗比哈尔滨降低64％;ASHP R410A在上海地区15 a内运行总成本比哈尔滨减少41％;WGH在上海的SO2、NOx和PM2.5排放量比北京分别下降17.4％、34.3％和34.3％;按照综合性能排序,依次为WGH、ASHP R410A、ASHP CO2、DEH;哈尔滨等严寒地区采用WGH具有优势,其他地区可采用ASHP R410A,ASHP CO2在西安地区的综合指数高于其他地区.

为了分析CO2/HCs混合工质用于单级带膨胀机系统的性能,研究了 CO2/R170,CO2/R290,CO2/RE170,CO2/R1270 4种混合工质的特性,建立单级带膨胀机系统热力学模型,分析了不同混合工质配比对系统性能和高压压力的影响.结果表明:为实现系统跨临界运行,混合工质中HCs的摩尔分数存在上限;对于系统性能,与纯CO2相比,CO2/R1270的最大制冷性能系数COP最高可提升2％,而CO2/R170、CO2/R290以及CO2/RE170则分别降低25％、12％和10％.当高压压力较低时,CO2/R290对系统性能的提升效果最为明显,最高可提升93％.在最优高压压力方面,与纯CO2相比,CO2/R290、CO2/RE170以及CO2/R1270均可降低系统最优高压压力,最大可分别降低13％、10％和7％,而CO2/R170则提升了 15％;综合考虑系统性能和降压效果,CO2/R1270和CO2/RE170的综合性能较好,CO2/R290更适用于运行压力较低的设备环境,而CO2/R170综合性能较差.

为了研究CO2工质在微细通道内流动沸腾换热特性,采用Fluent软件建立模型,通过给定边界条件模拟分析了CO2沸腾换热,与已有的换热关联式进行对比分析.结果表明:低干度下的相对误差在15％以内,验证了模型的准确性.根据液相容积分配图,在低干度条件下,随着饱和温度和热流密度的增大,通道内气泡的数量增多,尺寸明显增大,说明CO2沸腾换热系数增大;质量流速对沸腾换热系数的影响较小,从而也说明了在低干度区,CO2核态沸腾机理占主导地位.

"建筑能源应用"类专业课程教学改革,以突出专业特色和优势、加强对学生实践及创新能力的培养为目的.文章通过分析"冷热源"系列课程现状,提出优化系列课程结构、加快教学内容更新,开展综合性课程设计活动及创新实验,加强教育教学方法改革等多种策略,以期促进课程改革目标的达成,满足新时代背景下社会及行业对人才的要求.

为了比较回热器对不同型式CO2热泵系统性能的影响,建立了5种带回热器CO2跨临界循环的热力学模型,分析了吸气过热度、蒸发温度、高压压力和气体冷却器出口温度对制冷、制热系数的影响,以及蒸发温度、气体冷却器出口温度对最优高压压力的影响,给出了不同循环的适用条件.结果表明:带膨胀机单级、双级压缩系统综合性能较好,制冷COP可分别达到2.83和3.2,制热COP可分别达到3.82和3.6,但都不适合加回热器;回热器对CO2跨临界双级带节流阀回热器循环(TSCV+IHE)性能提高最大,过热度平均每提升5?℃,COP提升约0.1;CO2跨临界单级带喷射器回热器循环(SCEJ+IHE)适用于蒸发温度、气体冷却器出口温度均较低的情况;单级压缩比双级压缩的最优高压压力低0.5～1?MPa;提高蒸发温度和减小气体冷却器出口温度都有利于降低最优高压压力.研究成果可为CO2跨临界循环的性能提高和优化提供参考.

为了提高CO2跨临界循环的性能,提出了一种双级压缩机械过冷带回热器(简称"TSC+MS+RE")循环,将其与双级压缩机械过冷(简称"tSC+MS")循环、双级压缩带回热器(简称"tSC+RE")循环进行理论计算和性能比较,分析了蒸发温度、环境温度、过冷度、制冷剂流量和排气压力等参数的影响.结果 表明:TSC+MS+RE循环的性能最好;在最佳过冷度下,TSC+MS+RE循环的COP比TSC+RE循环增加了33.3％,比TSC+MS循环增加了10.9％;TSC+MS+RE循环的最佳过冷度随着蒸发温度的升高而减小,压缩机耗功比随着蒸发温度的升高而逐渐增大;对于TSC+MS+RE循环,增设回热器导致了压缩机排气温度的升高.