Vehicle Air Conditioning System Research Articles

SIMULATION OF VEHICLE COOLING LOADS AT DIFFERENT ORIENTATIONS

This paper presents a numerical simulation of the effect of vehicle orientation on the hourly vehicle cooling load profile. This profile enables prediction of a maximum cooling load and hence maximum cooling capacity to be supplied for equipment selection. The correlations and equations proposed by ASHRAE and previous researchers and compressed Singapore weather data from the open literature were used. Four vehicle orientations: North, East, South, and West were considered for a 1.6L Proton Wira Aeroback passenger car. The steady-state heat balance concept was adopted for the cooling load model. A validation exercise indicates that the simulation results are within 6% of published results. In this study, the cooling load profile predicts a maximum load between 12.00 noon and 1.00 pm for all typical days due to high values of solar radiation intensity and outdoor air dry bulb temperature compared to other hours. The highest cooling load occurs when the front wind screen is facing East in March/April at 2.71 kW. Thus, with a 5% safety factor, the highest cooling load is estimated at 2.85 kW. When the cooling capacity is estimated at 10% higher than this maximum cooling load, the proposed design evaporator coil cooling capacity is then estimated at 3.13 kW. This cooling load/capacity provides a basis for new vehicle air-conditioning system development, especially for future full electric vehicles.

Experimental investigations on the performance of solar powered cabin air ventilator

Sultanate of Oman witness a long summer with mostly clear blue skies and typically higher ambient temperatures as seen in other GCC countries. This type of environment warrants the use of high capacity and reliable air conditioning systems, both at resident buildings and vehicles. During summer, cars parked directly under the sun, experience a very high temperature rise inside its cabin in the range of near to 50 °C. This high cabin air temperature often causes thermal discomfort to passengers entering the parked car and also has a serious impact on the cars air-conditioning systems, as it takes longer time to bring back the thermal comfort inside the cabin. The studies also revealed that the high cabin temperature often causes health hazards to occupants, especially to infants. Current research paper, reports an experimental study carried out on a parked car, with instrumentation to identify the various the temperature zones inside the car cabin. This experiential study is aimed to improve the thermal comfort inside the cabin through solar powered cabin air ventilator for effective management of cabin air temperature. The study was carried on a chosen vehicle parked at a set direction and location exposed to day long sunlight at Muscat for considerable period of time. Firstly, the study identified the various temperature zones inside the car cabin and ventilation driven with a 10 Wp solar panel was developed to accomplish the required air exchange inside the cabin, along with continues instantaneous heat rejection through steady air exchange between inside and outside environment. A simple ventilator was developed by means of two fans which drove out the hot trapped air and a secondary fan to cool down the temperature inside the car by providing fresh air for limited time. The experimental investigation showed that the vehicle cabin temperature was typically 10 °C lower when ventilator was turned on. On a typical day on month of May, the cabin air temperatures was approximately 21 °C higher than the ambient air temperature, while with the developed ventilator the difference between the cabin and outside air temperature was reduced by 50% approximately. With the ventilator in operation, it was observed that time taken to reduce the cabin air temperature through vehicle air conditioning system to a satisfactory level was much quicker; typically it took less than the half of the time compared to those values tested without ventilator. Thus indicating, the power saving potential of the developed system as the desired level of thermal comfort can be achieved within the shorter period of time. The reduction in time taken to cool down the cabin temperature to the acceptable limits has direct two fold effects; firstly, the fuel consumption for cooling purpose is reduced and secondly, increased thermal comfort level inside the cars cabin. However, the temperature drop pattern was not similar all around the cabin, due to the varied level of cabin sunlight exposure. Temperature drop at the front of the car was lower than in middle and rear of the car. From the study it can be concluded that, with solar powered ventilator, the temperature inside the car was nearly 10 °C lesser compared to cabin without ventilator and it also helps in to bring back the thermal comfort inside the cabin nearly within half time vis-à-vis cabin without ventilation.

An Expert Fault Diagnosis System for Vehicle Air Conditioning Product Development

The paper describes the development of the vehicle air-conditioning fault diagnosis system in automotive industries with expert system shell. The main aim of the research is to diagnose the problem of new vehicle air-conditioning system development process and select the most suitable solution to the problems. In the vehicle air-conditioning manufacturing industry, process can be very costly where an expert and experience personnel needed in certain circumstances. The expert of in the industry will retire or resign from time to time. When the expert is absent, their experience and knowledge is difficult to retrieve or lost forever. Expert system is a convenient method to replace expert. By replacing the expert with expert system, the accuracy of the processes will be increased compared to the conventional way. Therefore, the quality of product services that are produced will be finer and better. The inputs for the fault diagnosis are based on design data and experience of the engineer.

축냉 시스템이 차 실내 열 쾌적성에 미치는 영향에 관한 실험적 연구

Abstract : This paper presents the experimental study of cabin thermal comfort using a cold storage heat exchanger in a vehicle air-conditioning system. Recent vehicle-applied ISG functions for fuel economy and emission, but when vehicles stop, compressors in the air-conditioning system stop, and the cabin temperature sharply increases, making passengers feel thermal discomfort. This study conducts thermal comfort evaluation in the vehicle, which is applied to a cold storage system for the climate control wind tunnel test and the vehicle fleet road test with various airflow volume rates and ambient temperatures blowing to the cold storage heat exchanger. The experimental results, in the cold storage system, air discharge temperature is 3.1-4.2°C lower than current air-conditioning system when the compressor stops and provides cold air for at least 38 extra seconds. In addition, the blowing airflow volume to the cold storage heat exchanger with various ambient temperature was examined for the control logic of the cold storage system, and in the results, the airflow volume rate is dominant over the outside temperature. For this study, a cold storage system is economically useful to keep the cabin at a thermally comfortable level during the short period when the engine stops in ISG vehicles.

Electric vehicle air conditioning system performance prediction based on artificial neural network

In this study, electric vehicle air conditioning system (EVACS) performances with scroll compressor and electronic expansion valve (EEV) were experimentally investigated by varying scroll compressor speed, EEV opening and environment temperature. An artificial neural network (ANN) model for EVACS performances (such as refrigerant mass flow rate, condenser heat rejection, refrigeration capacity and compressor power consumption) prediction was developed based on experimental data. The ANN model was tested with two transfer functions (logsig and tansig) and different hidden neurons (3–13) using Levernberg-Marquardt algorithm. The optimized ANN was determined as a configuration of 4-13-4 with logsig transfer function, which demonstrated the best capability with mean relative errors, root mean square errors and correlation coefficients in the range of 0.92–2.71%, 0.0044–0.0141 and 0.9975–0.9998, respectively.

Analysis of leakage factors affecting ECV performance in variable compressor

Solenoid operated electromagnetic control valve (ECV) using in an external variable displacement swash plate type compressor is widely used for air conditioning control system because of its low energy consumption and high efficient characteristics. ECV controls the entire vehicle air conditioning system by means of a pulse width modulation (PWM) system that supplied from an external controller. Different pressure ports located within ECV has important functions to control the air/refrigerant flow through its internal passages. The flow paths are preciously maintained with acceptable ranges of leakage (gap) between the parts inside it which is followed by effective design and critical dimensioning of its internal features. Therefore, it saves energy losses from the solenoid operation as well as ensures the balance of forces within it. The research paper highlights analysis of the leakages (at different pressure ports) and dimensioning tolerance factors that affects the ECV performance.

Aspects of Modeling and Optimizing Air Circulation Currents in a Car Cabin

Air conditioning system is one of the main components of modern cars, which defines the level of comfort, its performances directly affecting the car performances. In order to have a car with high level of thermal comfort, the air-conditioning system must be efficient in terms of energy, it has to perform many functions regarding the microclimate control (control of temperature, humidity, filtration), and in addition must fulfill safety and security functions in circulation (demisting and defrosting). Also vehicle air-conditioning system can significantly influence fuel economy and tailpipe emissions of conventional and hybrid electric vehicles (HEV) and reduce electric vehicle (EV) range.

Simulation Study on Characteristics of Ultra-Low Temperature Heat Pump Air Conditioning System for Pure Electric Vehicles

In view of high discharge temperature of compressor, the heating performance attenuated seriously, even unable to work properly and other issues of normal heat pump air conditioning system for electric vehicles under low temperature conditions, a gas-mixing heat pump air conditioning system for pure electric vehicles is designed. Based on the first law of thermodynamics and coupling properties among all components, the mathematical model of this system is established. The analog computation of main performance parameters of this system is carried out by this model, having a better match in comparison with experimental results. By simulation, the results show that the system can effectively solve the problems of high exhaust temperature from compressor and heating performance attenuation seriously of non-gas-mixing heat pump air conditioning system for pure electric vehicles under low temperature condition.

Emissions of halocarbons from mobile vehicle air conditioning system in Hong Kong

During the implementation of Montreal Protocol, emission inventories of halocarbons in different sectors at regional scale are fundamental to the formulation of relevant management strategy and inspection of the implementation efficiency. This study investigated the emission profile of halocarbons used in the mobile vehicle air conditioning system, the leading sector of refrigeration industry in terms of the refrigerant bank, market and emission, in the Hong Kong Special Administrative Region, using a bottom-up approach developed by 2006 IPCC Good Practice Guidance. The results showed that emissions of CFC-12 peaked at 53 tons ODP (Ozone Depletion Potential) in 1992 and then gradually diminished, whereas HFC-134a presented an increasing emission trend since 1990s and the emissions of HFC-134a reached 65,000 tons CO2-equivelant (CO2-eq) by the end of 2011. Uncertainty analysis revealed relatively high levels of uncertainties for special-purpose vehicles and government vehicles. Moreover, greenhouse gas (GHG) abatements under different scenarios indicated that potential emission reduction of HFC-134a ranged from 4.1 to 8.4×105tons CO2-eq. The findings in this study advance our knowledge of halocarbon emissions from mobile vehicle air conditioning system in Hong Kong.

Performance Study of Electric Compressor in Non-Electric Vehicle

The usage of electric compressor inside conventional non-electric vehicle is a new shifts in current vehicle air conditioning system which currently using belt-driven compressor to operate. The usage of belt-driven compressor causes the compressor speed to vary with engine speed rotation, which we cannot control. The usage of electric compressor to replace the belt-driven compressor makes the speed to be according to the cooling load and thus reducing engine load. The current research activity focuses on the development of electric compressor using direct current (DC) from vehicles battery to replace current belt-driven in vehicle air conditioning system. Performance study is focusing on temperature inside cabin, cooling capacity, compressor power consumption and coefficient of performance (COP). The DC compressor speed is varying at 1800, 2000, 2200, 2400, 2500 and 3000 rpm at internal heat load of 1000W with temperature set-point of 20°C. The system uses On/Off controller and compared to belt-driven compressor. The overall experimental results in better energy efficiency at the expense of lower cooling capacity.

Localized Cooling for Human Comfort

Author(s): Wang, Mingyu; Wolfe, Edward; Ghosh, Debashis; Bozeman, Jeffrey; Chen, Kuo-huey; Han, Taeyoung; Zhang, Hui; Arens, Ed | Abstract: Traditional vehicle air conditioning systems condition the entire cabin to a comfortable range of temperature and humidity regardless of the number of passengers in the vehicle. The A/C system is designed to have enough capacity to provide comfort for transient periods when cooling down a soaked car. Similarly for heating, the entire cabin is typically warmed up to achieve comfort.Localized heating and cooling, on the other hand, focuses on keeping the passenger comfortable by forming a micro climate around the passenger. This is more energy efficient since the system only needs to cool the person instead of the entire cabin space and cabin thermal mass. It also provides accelerated comfort for the passenger during the cooling down periods of soaked cars. Additionally, the system adapts to the number of passengers in the car, so as to not purposely condition areas that are not occupied.The present paper reports on a fundamental study of localized cooling to achieve comfort in a vehicle environment. The individual cooling streams are evaluated by human comfort riders for effectiveness and limitations. Based on the local cooling studies, combination local cooling strategies are then created and evaluated by riders.

Efficient and ‘Green’ Vehicle Air Conditioning System Using Electric Compressor

Reducing energy consumption and ensuring thermal comfort are two important considerations in designing vehicle air conditioning system. Alternative approach to reduce energy consumption proposed in this study is to use an electrically-driven compressor (EDC) powered by a 12-volt lead-acid vehicle battery which is charged by the alternator. This system makes the speed of compressor to be independent of the engine crankshaft speed. Typical belt-driven compressor of automotive air conditioning system (AAC) caused cooling capacity to vary with engine speed. The current research activity focuses on the experimental investigation on cabin temperature and fuel consumption of a 1.3 liter 5 seater hatchback vehicle on roller dynamometer at variable speed of 1800, 2000, 2200, 2400 and 2500rpm with internal heat load of 1000W at temperature set-point of 21°C. The overall experimental results show that the performance of EDC is better than the conventional belt-driven system with the opportunity for a better energy control.

Performance Study of Hydrocarbon Mixture for Green Vehicle Air-conditioning System

Experimental tests were conducted to monitor vehicle air-conditioning system in real life using hydrofluorocarbons (HFC-R134a) and hydrocarbon refrigerant as the working fluid for the compressor. The major variable for this study is vehicle speed. The tests were conducted on a roller dynamometer using a 5 door A-segment hatchback vehicle with a 1.3liter petrol engine to stimulate an actual vehicle on a level road with HVAC unit operating at a temperature set point of 21°C and blower speed at 2. The weight and internal heat load from passengers are taken into considerations with ambient temperature of 30°C and humidity of surrounding conditions at 50-65%. The result shows positive improvements on temperature distribution and fuel conservation with a possibility to be as an alternative refrigerant without any necessity of changing parts in the current system.

Heat pump air conditioning system for pure electric vehicle at ultra-low temperature

When the ordinary heat pump air conditioning system of a pure electric vehicle runs at ultra-low temperature, the discharge temperature of compressor will be too high and the heating capacity of the system will decay seriously, it will lead to inactivity of the heating system. In order to solve this problem, a modification is put forward, and an experiment is also designed. The experimental results show that in the same conditions, this new heating system increases more than 20% of the heating capacity; when the outside environment temperature is negative 20 degrees, the discharge temperature of compressor is below 60 degrees.

Thermodynamic assessment of active cooling/heating methods for lithium-ion batteries of electric vehicles in extreme conditions

The battery cooling/heating with active methods is required for EVs (electric vehicles) in the extreme temperature conditions. This work presents a new active battery cooling/heating method based on PCS (phase change slurry) cycle. Two typical often used active cooling/heating methods so-called the direct cabin air blow and refrigerant circulation are also illustrated in detail. The thermodynamic assessment is conducted on these battery active cooling/heating methods with both of 1st Law and 2nd Law analysis. The variations of extra thermal load to the vehicle air-conditioning system are investigated as changes of ambient temperature, humidity and thermal load for the direct cabin air blow method. The simulation results show that the direct cabin air blow method causes more extra thermal load to the air-conditioning system without considering the cabin ventilation effect. The PCS cycle method performs higher exergy efficiency than that of using refrigerant circulation method.

Control Algorithm Optimization of Electric Air Conditioning Based on ADVISOR

In order to develop more energy-saving control algorithm, an electric vehicle air conditioning system model is established. Electric air conditioning system compressor model, compartment thermal load model, heat transfer model, controller model and temperature calculation model are built based on certain pure electric commercial vehicle air conditioning system. A compound control method applying fuzzy and PID theory is put forward in this paper. A secondary development of EV model is established in ADVISOR. As the result shows, the Fuzzy-PID control method is more accuracy and consuming less energy. Optimized control algorithm for air conditioning is realized.

The Project Design for Cold Energy Recovery of LNG Vehicle Air-Conditioning System

A kind of potential fuel for vehicles is Liquefied Natural Gas (LNG) whose cryogenic energy can be recovered for vehicles air-conditioning system. In this paper, LNG city bus air-conditioning system utilizing LNG cold energy is concerned to be subject investigated. The design requirements of cold energy recovering for LNG city bus air-conditioning system are introduced and the project design is presented.

Calculation of Coach Body Heat Transfer Coefficient for the High-Speed Railway Train in China

The coach body of the high-speed railway train is required to have a good thermal insulation performance. It can keep a comfort passenger environment and decrease demand for the cooling load of air-conditioning system. The determination of coach body heat transfer coefficient (K-value) is critical for the efficient design of vehicle air-conditioning system. A heat transfer coefficient calculation model is especially proposed for the typical aluminum section thermal insulating wall structure of high-speed trains coach body in china, on the basis of the fin heat transfer mechanism. For the train type of CRH3G, the calculating coach body heat transfer coefficient is in good agreement with the experimental value. So the proposed calculation method can significantly improve the computational efficiency of the K-value for the high-speed railway trains which have the typical aluminum section insulation wall structures, and provide a trustable basis for the coach body structure optimization design.

휜 타입 내부열교환기 적용에 따른 차량용 냉방시스템 성능 특성

내부열교환기를 이용한 에어컨 시스템은 작동유체인 R134a의 고압측 액상냉매와 저압측 기상냉매의 상호 열교환을 통해 시스템의 응축 효율을 증가시켜 에너지 효율을 개선시킨다. 이는 에어컨 시스템의 성능 향상 및 경량화를 가능하게 하여 차량 연비 향상과 냉매 누출을 최소화할 수 있으며, 또한 현 R134a 대비 대체냉매 (R1234yf 등)의 동등 냉방성능 확보를 가능하게 하는 기술이다. 본 연구에서는 내측 압출 파이프 및 외측 사이 고효율 냉각 휜 (fin)이 삽입된 이중관 형태의 내부열교환기 상세 설계를 위해, 냉각 휜의 높이 및 내측 압출 파이프 내부형상 등의 다양한 형상 설계인자 변경에 따른 열전달 성능 및 압력강하 특성을 살펴보았다. 가장 우수한 내부열교환기 성능은 난류형성을 위한 내측관 형상이 라이너 및 세레이션 겸용 타입이었으며, 이는 내부열교환기가 장착되지 않은 경우보다 냉방시스템 성능이 약 6.4%, 시스템 COP는 약 9.2% 향상된 결과를 나타내었다. Internal heat exchanger (IHX) apparatus using the temperature difference between high and low pressure lines in vehicle air conditioning system is a good method to enhance the cooling performance. In this study, we designed various double-pipe internal heat exchangers which have inner fins between the internal pipe and external pipe. We also measured the performance characteristic (pressure drop, cooling capacity, compressor work and coefficient of performance (COP)) of the modified internal heat exchangers that had the change of the fin height and the inside shape of the internal pipe. This experimental results indicated that the liner and serration type internal heat exchanger was the best cooling performance. In addition, the air conditioning system with the liner and serration type internal heat exchanger showed the improved performances of about 6.4% and 9.2%, respectively, for the cooling capacity and COP.

An Experimental Study on Cycle Performance of the Mobile Air Conditioner with and without Indoor Fan Operation

Operating characteristic of an air conditioning system for vehicle is dynamic and anomalous. Due to the dynamic behavior of the system, the performance measurement should be taken in account in many different kind of environmental condition with various thermodynamic variables. One of the driving conditions of the system, rotating speed of the compressor for air conditioning is the most important factor consideration that is directly connected to the vehicle engine through clutch and belt. The engine was simulated with 18.5KW class AC motor to drive the compressor. Two environmental chambers are built in this study to simulate operation condition of the system.