Vehicle Air Conditioning System Research Articles

On the Usefulness of Employing ANSYS Motor-CAD Software in Designing Permanent Magnet Synchronous Machines

This paper deals with the simulation of a permanent magnet synchronous machine (PMSM) to be developed for driving a scroll compressor of a vehicle air conditioning system. The simulations were needed for the verification of the pre-sizing and for the electromagnetic behavior analysis of the PMSM. These were performed by using the ANSYS Motor-CAD software. All the obtained results emphasized that the pre-sizing of the PMSM was performed correctly, and the designed electrical machine can fulfill all the prescribed requirements. To highlight the superiority of the chosen surface-mounted PMSM topology, a comparative study was performed for four PMSMs having the same stator but different rotor topologies having the same quantity of permanent magnets. The study revealed that the PMSM with permanent magnets on its rotor surface is the best-fitting variant for the foreseen application. By intensively using the ANSYS Motor-CAD software, the authors appreciated that this product is a very useful tool in the hands of the designers not only in evaluating the machine’s computed geometry (by checking its correctness and feasibility), but also in its in-depth electromagnetic analysis and in calculating its parameters of interest.

Real-time energy performance benchmarking of electric vehicle air conditioning systems using adaptive neural network and Gaussian process regression

One major concern of the electric vehicle is the limited driving range per charge. Among its auxiliary systems, the heating, ventilation, and air conditioning (HVAC) system consumes the largest amount of electricity and can have a significant impact on the driving range when operational faults occur. This paper proposes a real-time benchmarking method to continuously evaluate the energy performance of a large number of electric vehicle air conditioning systems. Each system is benchmarked based on the energy consumption of its peer systems. Considering the energy consumption is influenced by several impact factors including the ambient environment and the cooling capacity, this study encodes the impact factors with an Autoencoder to measure the similarities between operating conditions. Also, considering the difference in operating conditions between a system and its peers, the uncertainties in energy performance benchmarks of the peer systems are quantified by the Gaussian process given its probabilistic nature. For each peer system, a Gaussian process regression model is developed as a benchmark, and the performance of the target system is assessed by comparing its measured energy consumption with the averaged benchmarks of all its comparable peers, accounting for the uncertainties. With the continual learning algorithm adopted, the Autoencoder can be updated periodically to adapt to real-time operational data with minimal computational cost. The real-time benchmarking method is applied to electric bus air conditioners in Haikou and Sanya, China, and can effectively identify malfunctioning systems. This method can be conveniently deployed on cloud for smart health management of public electric vehicles in smart cities.

Heating performance of heat pump air conditioning system for battery electric vehicle with different refrigerants

To improve the heating performance of Heat Pump Air Conditioning System (HPACS) of Battery Electric Vehicle (BEV) and reduce the greenhouse effect of refrigerants, the performances of multiple refrigerants in different modes and conditions are analyzed in this paper. Based on Worldwide Harmonized Light Vehicles Test Cycle (WLTC) dynamic conditions, the impact of heating on battery State of Charge (SOC) is analyzed in HPACS and Positive Temperature Coefficient (PTC) combined heating mode. To better evaluate the contribution of refrigerants to the greenhouse effect, Total Equivalent Warming Impact (TEWI) is used to evaluate multiple refrigerants. The results show that heating capacity increases with the increment of compressor power and air velocity. As compressor power decreases and air velocity increases, COP increases. R32 and R744 are the optimal refrigerants. When the ambient temperature is between −10°C and −15°C under WLTC conditions, the SOC reduction of R32 system is 20.8%–21.1% less than that of R134a system. When the ambient temperature is between −20 and −25°C, the SOC reduction of R744 system is 21.4%–21.6% less than that of R134a system. And the carbon dioxide emissions of R32 and R744 systems are 35.1%, 66.9%, 39.2%, and 55.5% less than that of R134a system, respectively.

An experimental method for evaluating vehicle cabin airtightness and ventilation performance

An experimental method is proposed for evaluating the airtightness of a vehicle cabin and the ventilation effects of three components of the vehicle ventilation system. The measurement results are used to derive a theoretical equation to predict the total air infiltration rate of the cabin as a function of the pressure difference between the cabin interior and exterior, respectively. The validity of the predictive equation is demonstrated by means of fan pressurization experiments performed with the vehicle air-conditioning system set in the fresh air mode. It is shown that the prediction results for the total ventilation rate deviate from the experimental results by less than 10%. The infiltration ventilation effect of natural diffusion in the vehicle cabin is measured using the CO2 tracer gas method. The air exchange rate (ACH) of the cabin is found to be 0.816 in the recirculation air mode and 3.554 in the fresh air mode.

Performance analysis and operation strategy of a dual-evaporation temperature heat pump system for electric vehicles in winter

With increasingly serious environmental and energy issues, efficient and environmentally friendly electric vehicles 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.

Electric Vehicle Air Conditioning System and Its Optimization for Extended Range—A Review

Environmental protection initiatives are speeding up the replacement of the present IC engine-based transportation system with an electric motor-driven system. In electric vehicles (EV), energy stored in batteries is used for the traction of the vehicle and the operation of the auxiliaries. The range of the electric vehicle was identified to be one of the major challenges faced by the EV segment. The optimization of the consumption of stored energy is the best solution for range improvement in an EV. Auxiliaries in the vehicle include basic accessories such as a lighting system and equipment for improved comfort such as air conditioners. Air conditioning equipment is the major power-consuming auxiliary in an EV apart from the traction motor. This review article discusses the significance and influence of different components of the air conditioning system, and methods followed by researchers to optimize the performance and reduce the energy consumption of the air conditioning system to extend the range of vehicles. The effects of thermal load and volume of space to be conditioned were also considered in this study. This review concludes by stating the different possibilities for the reduction in power consumption and emphasizes zonal air conditioning of occupant space as a solution for reducing energy consumption or increasing the range of EVs. Compared to full-space air conditioning, zonal AC can reduce power consumption by up to 51%.

Simulation of CO2 heat pump air conditioning system for new energy vehicle

The CO2 heat pump air conditioning system of new energy vehicle is designed, and the vehicle model of CO2 heat pump module and heat management system is established based on KULI simulation. The effects of refrigerant charge, running time and compressor speed on the heat pump air conditioning system is studied, and the energy consumption is compared with the PTC heating system and the CO2 heat pump air conditioning system without waste heat recovery. The results show that the optimal charge for full-service operation is 750 g; increasing the compressor speed can increase the cooling capacity, so that the refrigerant temperature in the passenger compartment and battery inlet can quickly reach the appropriate temperature, but the COPh, COPc are reduced by 2.5% and 1.8% respectively. By comparing it with PTC heating and CO2 heat pump air conditioning systems without waste heat recovery, it is found that the energy consumption of this system is only for the PTC heating systems 42.5%, without waste heat recovery carbon dioxide heat pump air conditioning system of 86.6%. It greatly saves energy, but also increased the waste heat recovery function, so that the system supply air temperature increased by 26%, improve passenger cabin comfort. This provides a reference for the future experimental research of CO2 heat pump air conditioning and heat management system.

Numerical analysis of heat pipe-assisted finned adsorber with FAM-Z02/water pair for vehicle air conditioning

• Heat pipe-assisted finned adsorber for vehicle air conditioning. • Heat and mass transport between the heat pipe, fins and adsorbent particles. • Parametric study on SCP, COP and AAMR of FAM-Z02/water adsorber bed. • Optimal bed configuration considering number of fins and minimized weight. Adsorption cooling system (ACS) driven by engine waste heat is an attractive alternative to vehicle air conditioning (A/C) system. To find a compact and efficient solution for onboard application, a heat pipe-assisted finned adsorber unit tube (AUT) packed with FAM-Z02 adsorbent was studied numerically. Based on the integrated physical prototype, a three-dimensional numerical model was developed to investigate adsorption/desorption characteristics combined with experimentally validated heat pipe model and adsorption isotherm model. Moreover, specific cooling power (SCP), coefficient of performance (COP) and adsorber bed to adsorbent mass ratio (AAMR) were quantified to evaluate cooling capacity and system performance. It is found that, compared with adsorber without heat pipe, a 15.3% increment of SCP and 19.1% increment of COP can be achieved in the FAM-Z02/water based adsorber due to the contribution of heat pipe, and the AUT has an optimal SCP of 64.19 W/kg at the cycle time of 8510 s. The smaller adsorbent particle size leads to more refrigerant adsorbing/desorbing under the same cycle time, and FAM-Z02 with 0.1 mm diameter provides optimal SCP of 66.7 W/kg for ACS due to smaller particles possess less intra-particle mass transfer resistance. When the cool source temperature and heat source temperature are 300 K and 365 K respectively, higher SCP can be achieved due to the larger cyclic water uptake. Heat pipe-assisted finned adsorber offers a viable solution for coolant’s application in onboard ACS, and a 6-fin adsorber packed with 0.1 mm-diameter FAM-Z02 is considered optimal under lower adsorption temperature and higher desorption temperature.

Optimization of radial flexible mechanism in scroll compressor based on oil film lubrication analysis

PurposeThe leakage problem caused by machining error, assembly error, wearing and thermal deformation has been the main factor hindering the development of scroll compressor. This paper aims to investigate the lubrication characteristics of radial clearance and further optimize the radial clearance, which can reduce the leakage in the tangential direction of the working chamber.Design/methodology/approachThis paper establishes a model of radial clearance oil film lubrication in scroll compressor. And, the method to solve the Reynolds and energy equations is presented, as well as the dimensionless and discretization by finite element difference method. To verify the established model, performance experiment of scroll compressor for electric vehicle air conditioning system is also carried out.FindingsBased on the presented model, the temperature field and distribution of the oil film in the radial clearance are analyzed. And the influence of the structural parameter on the radial clearance is further discussed. The optimum radial clearance could be achieved at β = 40°–42°, where the orbiting scroll is in the state of rotary balance. And, the simulation results coincide well with the experimental results.Originality/valueThis work provides an effective model to evaluate the lubrication characteristics of radial clearance in scroll compressor, which can provide guidance for the design of scroll compressor.

A review of research on vehicle exhaust dispersion model based on CFD simulation technology

CFD, comprising multiple types of softwares, involves complex technological theories and is used to solve profound issues with a huge amount of calculation. Given the complexity and profundity, this study selects Fluent, OpenFOAM and Star-CCM+ as representatives to review the application of the CFD simulation technology in the vehicle exhaust dispersion models. Fluent, a commercial CFD software, started relatively early and has so far been the most widely used in the field of motor vehicle exhaust dispersion research; OpenFOAM, is open source and has a large number of models and algorithms. Apart from supporting pure model research, OpenFOAM has broad application prospects in coupling with the mesoscale model WRF to improve the accuracy of pollutant dispersion simulation; Star-CCM+, less applied in the research field of vehicle exhaust dispersion, focuses more on vehicle air conditioning system, vehicle radiator, refueling, vehicle aerodynamic noise source simulation and other related fields. The research provides theoretical basis and scientific reference for the application of CFD in the field of urban block-scale air quality research. In the future, with the rapid development of computer technology and the introduction of new theories and intelligent algorithms, CFD technology is very likely to achieve new breakthroughs and continue to enjoy even wider application in the research of motor vehicle exhaust dispersion.

An experimental investigation on the frosting and defrosting process of an outdoor heat exchanger in an air conditioning heat pump system for electric vehicles

The heat pump air conditioning system is a promising solution for energy conservation and ensuring a good driving range can be maintained. Micro-channel heat exchangers are used as outdoor heat exchangers to improve the heat transfer efficiency. A heat pump system introduces frosting problems to the outdoor heat exchanger, especially in a low temperature and high humidity environment. This study conducted an experiment on the frosting and defrosting process of the outdoor heat exchanger of a heat pump air conditioning system for electric vehicles. The surface of the outside heat exchanger had an uneven distribution of the frost layer owing to the variation in the liquid-phase refrigeration occupation. Thermal parameters of the system were obtained. The suction pressure was sensitive to the frosting process, decreasing from (0.15–0.25) to (0.02–0.1) MPa, and it can be used as a frosting monitoring parameter. The frosting and defrosting behavior was also studied at a micrometer scale on the surface of the heat exchanger. The ice bridge phenomenon was observed in the frosting process. Hydrophilic and hydrophobic treatments of the heat exchanger surface were conducted for compassion and it was found that the hydrophilic treatment of the surface of the outdoor heat exchanger of the vehicle heat pump effectively slows frosting. Future experimental research should investigate the effects of superhydrophobic and superhydrophilic surface treatments, in addition to hydrophilic and hydrophobic surface treatments on the performance of the heat exchanger, to improve the performance of the overall heat pump system.

Prediction of Vehicle Driver’s Facial Air Temperature With SVR, ANN, and GRU

The facial air temperature has a significant impact on the driver’s thermal comfort. Machine Learning models have been proved to be evidently effective in temperature predicting. In this study, three models are employed to predict the drivers’ facial temperature in a certain series of vehicles, which are Support Vector Regression (SVR), Artificial Neural Network (ANN), and Gated Recurrent Unit (GRU) respectively. We conduct an electric vehicle air-conditioning system experiment to collect the datasets of drivers’ head temperature and 6 input features for model training. And we divide the training and testing datasets in two different ways. In these two ways, the testing datasets are the last 20% of datasets in each condition, and the datasets in the last condition respectively. The evaluation of these models’ performance is exerted with Root Mean Squared Error (RMSE), Mean Absolute Error (MAE), and the coefficient of determination (R2). The MAE of these three models are SVR: 0.8096, ANN: 0.4984, GRU: 0.7289 in the trained working conditions, and SVR: 1.0946, ANN: 0.7878, GRU: 0.7837 in the untrained working conditions. The results of MAE show that the performance of the ANN is the best among the three models when tested with the trained and untrained test datasets, and the same conclusion can be got from the R2 and RMSE. Moreover, the accuracies of these models are lower when the tested dataset is collected in new working conditions. According to the results above, ANN may be the preferred method for vehicle drivers’ facial air temperature prediction.

A novel multistage constant compressor speed control strategy of electric vehicle air conditioning system based on genetic algorithm

This study establishes a passenger cabin-coupled air conditioning model that the heat exchangers adopted in the air conditioning model, are calibrated by testing, during which the parameters for establishing the passenger cabin model are measured. The cabin temperature simulation results of the air conditioning model proposed in this paper fit well with the test results, with a maximum difference of 3 °C. A genetic algorithm (GA) optimization-based multistage constant-compressor speed (MCCS) air conditioning system control strategy is proposed. This control strategy sets the cabin temperature as the input control factor and the compressor speed as the output factor, and different cabin temperature ranges correspond to the MCCSs, which are optimized by the GA. The presented strategy is contrasted with the most commonly used on/off controllers and the proportional integral derivative (PID) controller, and an engineering-applied (EA) air conditioning control strategy. The proposed controller can maintain passenger cabin thermal comfort and save energy simultaneously, and it can be easily applied in engineering. Based on the simulation results, the MCCS controller can save 17.5, 7.5, and 5.8% more energy consumption than the on/off, PID, and EA controllers. Moreover, it can improve the coefficient of performance of the air conditioning system by 5.3 and 3.9% more than the PID and EA controllers. Therefore, the proposed MCCS controller can increase the operation efficiency of electric vehicles AC system.

Intelligent of Electric Vehicle Heat Pump Air Conditioning Control System

Traditional fuel vehicles consume a lot of fuel and cause serious environmental pollution. At present, when environmental protection is being paid more and more attention, Electric vehicles have received extensive attention from countries all over the world for their advantages in energy safety, environmental protection and long-term development. Electric vehicles have received extensive attention from countries all over the world for their advantages in energy safety, environmental protection and long-term development. With the rapid development of electric vehicles, as the main energy consumer, following the electrical system, the air-conditioning system has become an important factor restricting the power, economy and durability of electric buses. At the same time, compared with the current electric heating PTC method commonly used in electric vehicles, heat pump air conditioners can increase the working range of electric vehicles. Therefore, the application of large-scale energy-saving systems, high-efficiency energy-saving systems, and electric vehicle air-conditioning systems is developed, it is of great significance to the promotion of electric vehicles. This article aims to intelligently study the control system of the electric vehicle air-conditioning heat pump.

Design optimization of external variable displacement compressor with R1234yf for vehicle air conditioning system

Due to the high global warming potential of the HFC-based R134a, it should be replaced by the HFO-based R1234yf as a working fluid for automotive air conditioning systems. In this study, for the external variable compressor whose stroke volume is controlled by the external signal used in the R134a air conditioning system, the optimization design of the compressor as the operating refrigerant changes from R134a to R1234yf is proposed. In order to analyze the working performance of the compressor a compressor simulation program was developed, and the drop-in test with R1234yf has been evaluated to replace R134a in the air conditioner system. From the drop-in test, both the cooling capacity and the coefficient of performance for the R1234yf decrease about 4 ~ 5% under the maximum stroke volume condition depending on the compressor operating speeds. And in the TEO5 control mode, where the lowest air temperature behind the evaporator is controlled at 5°C, it was found that there is only less than 4% reduction of the cooling capacity, while the coefficient of performance drops by up to 17% due to the increased compressor power. From the simulation result, we found that the reduced coefficient of performance of R1234yf might stem mainly from the increased losses by the suction and the discharge valves. By redesigning the suction and discharge valves within the designable range, as the results, the coefficient of performance is improved 1% at the MSV condition and 8% under the TEO5 control mode, respectively.

Energetic, economic, environmental investigation of carbon dioxide as the refrigeration alternative in new energy bus/railway vehicles’ air conditioning systems

New energy transportation is an important link for the future development of global energy industry, while higher and more precise requirements for the new energy vehicles’ air conditioning systems are also needed with its rapid development. Because of the stringent environmental and energy problems, the natural refrigerant CO2 (carbon dioxide) is investigated in this paper as an ideal alternative of the conventional HFC (Hydrofluorocarbon, R407C) used in bus/railway vehicle air conditioning systems. First, after constructing the thermodynamic simulation models and developing the operational strategies under the one-dimensional simulation of thermodynamic cycle, the thermodynamic performances of both CO2 and R407C systems are comprehensively compared under all the annual heating/cooling conditions, which showed that CO2 system performs absolutely better in heating but not good enough in cooling mode. Then, based on the annual climate data of 116 cities/regions, the daily heating/cooling loads and corresponding power consumptions, COPs of both CO2 and R407C systems are clearly summarized, thereafter the life cycle climate performances (LCCP) and total costs are obtained. As results, the annual comprehensive ratios of CO2 performances over R407C are 0.949, 1.047, 0.915 from energetic, environmental and economic aspects. By drawing the contour maps, an innovative concept of CO2 equators are proposed and described in detail from energetic, environmental and economic perspectives. By formulating the annual operation strategy of the CO2 system on the vehicle, obtaining its annual comprehensive performance, and comprehensively considering the energy consumption index, environmental protection index and economic index of the CO2 system from the global application perspective, this study has filled the research gap mentioned above, which would also be a significant reference for researchers, manufacturers, component suppliers and policy makers.

Operation strategy and performance investigation of a high-efficiency multifunctional two-stage vapor compression heat pump air conditioning system for electric vehicles in severe cold regions

Cooling and heating are indispensable for electric vehicles (EVs) in severe cold regions due to the hot summer caused by global warming. A multifunctional two-stage vapor compression (MTSC) heat pump air conditioning system (HPAC) with its operation strategies is proposed, which can operate in not only single-stage vapor compression (SSC) cooling and heating mode, but also two-stage vapor compression (TSC) heating mode under ambient temperatures as low as −35 °C. Then a simulation model is developed, and comparative analyses among the MTSC HPACs with different refrigerants, and between MTSC HPACs and SSC HPACs are conducted. The influences of intermediate pressure and pressure drop on performance are discussed. Besides, exergy analysis and second law performance are presented. It is found that the MTSC HPAC attains a 6% to 30% higher coefficient of performance (COP) than the SSC HPAC when the evaporating temperature changes from −10 °C to −20 °C, and 156% to 85% higher energy efficiency than the positive temperature coefficient (PTC) heaters when the evaporating temperature varies from −25 °C to −45 °C. The COP of R290 is slightly higher than that of R410A, R32 and R454C. Furthermore, the main exergy destruction appears in compressors, accounting for 40% to 45%.

Computational fluid dynamics simulation and performance optimization of an electrical vehicle Air-conditioning system

In vehicles, air conditioning tends to offer efficient thermal conditioning and air circulation inside cabin for passenger comfort from different climate variation. The working performance of air conditioning system in vehicles is an essential factor for thermal comfort and driving safety of the passenger compartment of vehicles. Therefore, it is of great significance to construct a numerical simulation model for theoretical analysis and performance evaluation of vehicle air conditioning system. In current research, the air conditioning system of an electric vehicle is taken as the research subject. Internal flow field characteristics of air conditioning system is investigated by Computational Fluid Dynamics (CFD). Results show that the air flow in air-conditioning system is relatively smooth, and the velocity distribution in the front windshield A area and the driver's field of vision of the left and right windows is not ideal when the defrosting-demisting mode is on; the velocity and air quantity distribution of the two outlets in the middle air duct are not uniform under blowing mode. In view of the uneven distribution of velocity and air quantity, the corresponding optimization scheme is proposed. After optimization, the cell relative velocity of the front windshield is significantly improved, and velocity distribution of the side window glass is slightly increased and the defrosting-demisting performance meets the vehicle defrosting requirements of national standard; after optimization, the air quantity distribution of the air ducts at blowing mode is more uniform, which is conducive to the comfort of the passenger compartment.

Coupling Effect of Air Flow Rate and Operating Conditions on the Performance of Electric Vehicle R744 Air Conditioning System

The air flow rate on the gas cooler side is one of the key parameters affecting the performance and running safety of transcritical CO2 electric vehicle air conditioning systems. After experimentally analyzing the effects of the air volume flow rate in the gas cooler on the cycle parameters and system performance, a novel method to evaluate the optimal air flow rate was proposed. In addition, the effect of the gas cooler air volume flow rate on the key performance parameters of the system (e.g., optimal discharge pressure) was explored. Finally, the coupling effects of the compressor speed, ambient temperature and optimal air flow rate on the system performance was also exhaustively assessed. It was found that as the discharge temperature, the CO2 temperature at the gas cooler outlet and the discharge pressure did not vary more than ±2%, the corresponding gas cooler air volume flow rate was optimal. For the single-row and dual-process microchannel evaporator used in this work, the recommended value of the optimal gas cooler air volume flow rate was 2500 m3·h−1. The results could provide reference for the fan speed design of electric vehicle CO2 air conditioning systems, especially for the performance under idling model.

Numerical and experimental investigation of multi-halide chemisorption system for exhaust gas heat recycling

Multi-halide sorbents have been found positive in reducing sorption hysteresis, and can work at a higher cooling temperature and a lower heating temperature when compared with the conventional single-halide sorbent. Thus, the size and weight of the existing systems for converting engine exhaust gas heat into cooling energy can be reduced. The working performance of the simplified system is analyzed by numerical simulation and experimental tests in this paper. The pressure-dependent X-T reaction model of the multi-halide sorbent is established based on a large amount of sample test data and the system performance is then simulated by ANSYS. Besides, a novel multi-halide sorption refrigeration prototype is built after the theoretical demonstration. The test refrigeration power is slightly lower but the COP from test is slightly higher than the calculation results because the heat and cold energy loss is ignored in the calculation. The differences between the calculated and experimental refrigeration power and COP are within 0.6 kW and 0.03, respectively. The prototype has a good adaptability to normal summer temperature and the maximum specific cooling power (SCP) gets to about 300 W∙kg−1. In summary, the multi-halide sorption system can recover the engine exhaust gas heat effectively to meet the cooling demand of the automotive vehicle, reducing the cooling cost of the vehicle air conditioning system by about 80%.