Automotive Air Conditioning Research Articles

Analysis of refrigerant pipe pressure drop of a CO2 air conditioning unit for vehicles

This study investigates the pressure drop in refrigerant pipes of a CO2 automotive air conditioning unit. A test rig to measure the pressure drop of arbitrarily shaped pipes is presented. As boundary conditions at the inlet of the test section, mass flow, pressure and enthalpy of the refrigerant are independently adjustable to values that cover the whole operating range of a CO2 automotive air conditioning system for cars in the premium segment. Numerical analysis using CFD and a one-dimensional modelling tool is carried out. The pressure drop for the suction pipe reaches values of up to 500 mbar. CFD simulation predicts the pressure drop with an error of 25.7% for single-phase flow whereas the deviation using one-dimensional models is 46.5%. During two-phase flow the error increases to 55.8% with one-dimensional models and 42.4% using CFD.

Analysis of a CO2 Transcritical Refrigeration Cycle with a Vortex Tube Expansion

A carbon dioxide (CO2) refrigeration system in a transcritical cycle requires modifications to improve the coefficient of performance (COP) for energy saving. This modification has become more important with the system’s more and more widely used applications in heat pump water heaters, automotive air conditioning, and space heating. In this paper, a single vortex tube is proposed to replace the expansion valve of a traditional CO2 transcritical refrigeration system to reduce irreversible loss and improve the COP. The principle of the proposed system is introduced and analyzed: Its mathematical model was developed to simulate and compare the system performance to the traditional system. The results showed that the proposed system could save energy, and the vortex tube inlet temperature and discharge pressure had significant impacts on COP improvement. When the vortex tube inlet temperature was 45 °C, and the discharge pressure was 9 MPa, the COP increased 33.7%. When the isentropic efficiency or cold mass fraction of the vortex tube increased, the COP increased about 10%. When the evaporation temperature or the cooling water inlet temperature of the desuperheater decreased, the COP also could increase about 10%. The optimal discharge pressure correlation of the proposed system was established, and its influences on COP improvement are discussed.

An optimized ANN for the performance prediction of an automotive air conditioning system

This article presents the prediction of the thermal performance of an automotive air conditioning system (AACS) by using an artificial neural network (ANN). The ANN has predicted the cooling capacity, compression work, and coefficient of performance (COP) of the AACS for a range of input parameters like refrigerant charge, compressor speed, and blower speed under a steady state. The ANN, optimized for a 3–10–3 configuration with the Levenberg-Marquardt algorithm, has shown a good agreement with the experimental values with a correlation coefficient higher than 0.999, mean relative error (MRE) between 5.0% and 6.49%, and low range of root mean square error (RMSE) and error index (EI). The impact of normalized and unnormalized data along with the type of input parameters on the model performance is also observed with a large number of experimental data. This investigation shows that a suitably designed ANN can provide better accuracy and higher reliability. It can be used as a predictive tool for an AACS that generally has a wide variation of operating conditions.

Heat Transfer Analysis of Conventional Round Tube and Microchannel Condensers in Automotive Air Conditioning System

In this paper, an experimental analysis of conventional air-cooled and microchannel condensers in automotive vapor compression refrigeration cycle concerning heat transfer coefficient and energy using R134a as a refrigerant was presented. The performance of two condensers and cycles tested regarding ambient temperature which it was varied from 40oC to 65oC, while the indoor temperature and load have been set to be 23oC and 2200 W respectively. Results showed that the microchannel condenser has 224 % and 77 % higher refrigerant side and air side heat transfer coefficient respectively than the coefficients of the conventional condenser. Thus, the COP, in case of using the microchannel condenser, was found to be 20 % higher than that of the conventional cycle. Also, the microchannel condenser has a 50 % smaller volume than the conventional. Therefore, it provides more space in the car engine container occupied with other components.

Energy and exergy analysis of compact automotive air conditioning (AAC) system

Automotive Air conditioning (AAC) is a unit that uses a high measure of energy from a car total engine power. In equatorial climate country such as Malaysia, high usage of AAC is inevitable due to hot, humid and rainy weather throughout the year. An understanding about the energy and exergy losses is essential to find the potential improvement to maximise the efficiency in an AAC system. The main objective of this study is to study the performance of energy and the exergy of a compact automotive air conditioning system. This cycle uses R134a and PAG lubricant as the working fluid. The different ranges of initial refrigerant charge and compressor speed have been tested on the AAC to evaluate the effect of different major thermodynamic parameters in performance. A theoretical model is developed to work out the thermodynamic parameters such as coefficient of performance, exergy destruction ratio, component efficiency defect as well as the dimensionless exergy balance for the AAC system components. The results of this study have shown that most of the energy has been destructed in evaporator part. In order to maximize the efficiency and performance of AAC system, further optimization needs to be done in order to improve the evaporator component.

Comparative Study of Single and Composite Nanolubricants in Automotive Air-Conditioning (AAC) System Performance

Various studies by leading experts have shown the effectiveness of nanolubricant in improving the performance of the automotive air conditioning (AAC) system. Along with the advancement of technology, composite nanolubricant have been introduced and have been proven to have better properties than normal nanolubricant. The Al2O3-SiO2/PAG composite nanolubricant have better stability, better heat transfer, and improve tribology characteristic compare to its individual single nanoparticles nanolubricant. However, until now no experiments were conducted to test the effectiveness of composite nanolubricant in the AAC system. An experimental study is then taken by testing the Al2O3-SiO2/PAG in AAC system. The results of this experiment have been compared with results of the previous study that uses Al2O3/PAG and SiO2/PAG in AAC system. It is found that the composite nanolubricant have a high enhancement in the COP and does reduce the compressor work of the AAC system. The comparison between Al2O3-SiO2/PAG, Al2O3/PAG and SiO2/PAG nanolubricant demonstrates that Al2O3-SiO2/PAG, has better performance in term of compressor work reduction and COP enhancement at an average of 28.7 % and 31.64 %, respectively. At last, it was recommended to use the Al2O3-SiO2/PAG nanolubricant for application in AAC system.

Composite nanolubricants in automotive air conditioning system: An investigation on its performance

AAC system is an important and necessary system in a vehicle in giving thermal comfort to the automotive cars passenger by reducing the surrounding temperature. The experimental investigation on performance of AAC system using composite nanolubricant provides useful data for future development of automotive cars due to its efficiency in improving the system performance. The AAC test bench was developed and utilized from Perodua Kancil. Cooling capacity, compressor work and coefficient of performance (COP) of AAC system using pure lubricant and Al2O3-SiO2/PAG composite nanolubricants had been investigated at different refrigerant charges (95 to 155g) and different speeds (900 to 2100 rpm). The result shows that the cooling capacity and COP of composite nanolubricants increased compared to pure lubricant. Meanwhile, the compressor work was reduced. Cooling capacity and COP are relatively increased by 59.91% and 7.72% respectively compared to based lubricant. The maximum reduction achievement for compressor work is by 9.35% with 155g refrigerant charge and at 2100 rpm. Therefore, Al2O3-SiO2/PAG composite nanolubricants is recommended to be used as the compressor lubrication to enhance AAC performances system.

Automotive air conditioning system with an internal heat exchanger using R1234YF and different evaporation and condensation temperatures

Automotive air conditioning system with an internal heat exchanger using R1234YF and different evaporation and condensation temperatures

Effect Of Engine Speed On The Performance Of Automotive Air Conditioning System Using R134a And R152a As Refrigerants

This paper presents a numerical approach in the investigation on the effect of engine speed on the performances of automotive air conditioning system using R134a and R152a as refrigerants. In the near future, R152a refrigerant is projected to replace R134a as working fluid in vehicle air conditioning systems. In this study, four engine rotations, i.e., 1000, 2000, 3000 and 4000 rpm that represent: idle, city, medium speed and high speed conditions, respectively, were investigated. In the modeling, the evaporating and condensing temperatures were assumed constant at 5°C and 45°C, respectively. The results showed that coefficient of performances (COPs) of the automotive air conditioning using R152a were higher than that of R134a for all engine speeds. The COP improvement of R152a increased with the increase in engine speed. At engine rotation of 4000 rpm, the COP improvement was by as much as 6.4%. The disadvantage of R152a compared to R134a was in its high discharge temperature. This condition is anticipated to affect the reliability of the compressor in the long run.

Thermodynamic Analysis of Various Refrigerants for Automotive Air Conditioning System

This study investigates numerically the thermodynamic analysis of various refrigerants on the basis of vapor compression refrigeration cycle. The refrigerants studied are R134a, R152a, R1234yf, R404A, R407C, R410A and R507A. The aim of this research is to find the alternative refrigerant of R134a numerically. EES Professional V9.944-3D is used in the modeling of thermodynamic cycle of VCRC and calculating the performance parameters of VCRC. The comparison of thermodynamic VCRC for all the refrigerants is made. The performance parameters include: cooling capacity, input power of compressor, COP, compression ratio and discharge temperature. These parameters are calculated at engine speeds of 1000 rpm, 2000 rpm and 3000 rpm, condenser temperature of $$50\,^{\circ }\hbox {C}$$ and evaporator temperature of $$5\,^{\circ }\hbox {C}$$ . The compressor volumetric efficiencies are taken as 0.75, 0.65 and 0.55 corresponding to engine speeds of 1000 rpm, 2000 rpm and 3000 rpm. The results of performance parameters for all refrigerants studied are exported to MATLAB R2017a software where the comparative analysis is performed. Results show that R152a is the only refrigerant which can be used as alternative in current AACS with minimum modification. The cooling capacity of R152a is slightly less than that of R134a, while its COP is found to be higher than that of R134a. R152a shows the highest COP improvement of 5.33% at engine speed of 1000 rpm. It has very low GWP and almost same saturation pressure corresponding to condenser and evaporator temperature as that of R134a, so it can serve as alternative refrigerant in current AACS.

Thermophysical property measurements on tetrabutylphosphonium sulfate ionic semiclathrate hydrate consisting of the bivalent anion

To develop the “hydrate thermal energy storage technology”, it is desired to reveal the mechanism of the thermophysical property manifestation on ionic semiclathrate hydrate. The influence of valence on thermophysical properties has not been investigated so far. In the present study, the phase equilibrium temperatures and the dissociation heats of tetrabutylphosphonium sulfate ((TBP)2SO4) ionic semiclathrate hydrate were experimentally studied. (TBP)2SO4 hydrate consists of the bivalent anion, SO42−. The highest phase equilibrium temperature was 6.5 °C at the mass fraction range from 0.363 to 0.384. The largest dissociation heat was (168.8 ± 2.4) kJ·kg−1 at the mass fraction 0.374. These values of the phase equilibrium temperature and the dissociation heat were respectively lower and smaller than those of the ionic semiclathrate hydrates with the monovalent anion. As a new choice for thermal energy storage medium, (TBP)2SO4 hydrate would be suitable to the automotive air conditioner and the cold chain for blood or perishable foods.

Flavisolibacter aluminii sp. nov., a novel member of the genus Flavisolibacter isolated from an automotive air conditioning system.

A Gram-stain-negative, aerobic, non-motile, rod-shaped, and yellow-pigmented bacterium, designated strain ID1709T, was isolated from an automotive air conditioning system collected in Korea. Analysis of 16S rRNA gene sequence similarity showed that strain ID1709T had 92.2-94.3% similarities with the type strains of members of the genus Flavisolibacter. The major cellular fatty acids were iso-C15:0, iso-C15:1 G, iso-C17:0 3-OH, and summed feature 3 (C16:1ω7c and/or C16:1ω6c). The predominant respiratory quinone was MK-7. The polar lipids comprised phosphatidylethanolamine, aminoglycophospholipid, two unidentified aminolipids, and three unidentified lipids. The DNA G + C content of the strain was 35.6 mol%. Based on phenotypic, chemotaxonomic, and genotypic data, strain ID1709T represents a novel species in the genus Flavisolibacter, for which the name Flavisolibacter aluminii sp. nov. (= KACC 19451T = KCTC 52778T = NBRC 112870T), is proposed.

Support vector regression modeling of the performance of an R1234yf automotive air conditioning system

This study aims at modelling various performance parameters of an automotive air conditioning (AAC) system using support vector regression (SVR), a novel soft modelling technique. For this purpose, a bench-top AAC system was set up, charged with alternative refrigerant R1234yf, and tested in a wide range of operating conditions. Next, the cooling capacity and coefficient of performance of the AAC system were evaluated. Then, the proposed SVR was trained by using some of the input-output data pairs, and the performance of model predictions was tested using the remaining data. It was determined that the SVR model yielded very accurate predictions.

Energy saving in automotive air conditioning system performance using SiO2/PAG nanolubricants

The use of automotive air conditioning (AAC) nowadays is essential because of the hot climate and global warming. The AAC increases the overall fuel consumption in order to cool down the car cabin, hence releases more CO2 into the atmosphere. Nanotechnology can be implemented into the lubricant of the AAC compressor which can aid in reducing the power consumption. Therefore, this paper investigates the effect of SiO2/PAG nanolubricants on the AAC performance and energy saving. The SiO2/PAG nanolubricants were prepared using the two-step method. The sedimentation observation and UV–Vis spectrophotometer evaluation confirmed the stability of the nanolubricants. The tribology analysis revealed the coefficient of friction of SiO2/PAG nanolubricants better than the original PAG lubricants. The performance parameters and power consumption (energy saving) of AAC system using SiO2/PAG nanolubricants were compared with PAG lubricants. The condenser pressure and the pressure ratio of the AAC system decreased by an average of 10.8% and 5.6%, respectively. The volumetric heat absorb increased up to 3% and the coefficient of performance increased by an average of 21%. The compressor work and power consumption of the AAC system reduced by 16.5% and 4%, respectively. As a conclusion, it was recommended to use 0.05% volume concentration of SiO2/PAG nanolubricants in AAC compressor for optimum system performance and energy saving.

Application of response surface methodology in optimization of automotive air-conditioning performance operating with SiO2/PAG nanolubricant

The effect of compressor speed, initial refrigerant charge and volume concentrations of SiO2/PAG nanolubricant on the performance of automotive air-conditioning (AAC) system are investigated in this study. Response surface method (RSM) was used in designing the experimental work and is based on face composite design. The developed quadratic models from RSM were helpful to envisage the response parameters namely heat absorbs, compressor works, and coefficient of performance (COP) to identify the significant relations between the input factors and the responses. The results depicted that adding SiO2 nanoparticle into PAG lubricant will enhance the COP of AAC. Optimization of independent variables was performed using the desirability approach of the RSM with the goal of maximizing the heat absorb and COP, consequently, minimizing the compressor work. The results revealed that the optimal condition with a high desirability of 73.4% for the compressor speed of 900 rpm, refrigerant charge of 95 g and volume concentration of 0.07%. At this condition, the AAC system operated with 193.99, 23.28 kJ kg−1 and 8.27, respectively, for heat absorb, compressor work and COP. DoE based on RSM was capable of optimizing the significant parameters which affect AAC performance.

Solar photovoltaic based air cooling system for vehicles

Abstract The conventional automotive air conditioning system was driven by internal combustion engine or power battery, which increased the oil consumption and vehicle carbon emission. In this study, a direct current (DC) air conditioning system powered by solar photovoltaic module (PV) has been designed to solve the problem of temperature increasing inside the vehicle when stops in the broiling summer. The purpose of this work is to design a whole DC air conditioning system with R134a as refrigerant, replacing the power source with solar energy. The result shows that the environmental condition in the vehicle has obviously improved by the DC air conditioning system, meeting the requirements of human bodies. In addition, in the experiment, the minimum refrigerating capacity should be ∼1500 W, maintaining the thermal equilibrium inside the vehicle under the sun blazing, when the vehicle stops and no person inside. The work will prompt further research of solar energy and development of solar electric vehicle air conditioning system.

Exergetic Investigation of a R1234yf Automotive Air Conditioning System with Internal Heat Exchanger

This study presents the exergetic investigation of an automotive air conditioning (AAC) system with the refrigerant R1234yf experimentally. The air-conditioning system is based on the conventional mechanical compression refrigeration cycle. An internal heat exchanger (IHX) has been added to the system in order to provide performance enhancement. The influence of the IHX investigated at different compressor speeds and air stream temperatures. Experimental measurements were collected by using a data-acquisition system, and the results were obtained by performing exergetic analysis. The exergy destruction, exergy efficiency and the total exergy destruction per cooling capacity were calculated. The analysis results were compared with a baseline system which operates with the refrigerant R134a. Furthermore, an empirical correlation was proposed for the determination of the total exergy destruction per cooling capacity for various compressor speeds for evaluating the system performance without doing further experiments. As a result, the exergetic efficiency of the system was improved by introducing IHX to the system. Moreover, it was observed that the temperature rise in the air stream decreased the exergy efficiency and increased the total exergy destruction per cooling capacity.

Thermodynamic analysis of compound cycle system for automotive waste heat recovery and air conditioning refrigeration

A compound cycle system, which integrates an automotive waste heat recovery (WHR) and air conditioning (A/C) refrigeration functions, is proposed in this paper. The models of this compound cycle system, independent organic Rankine cycle (ORC) system and independent A/C system are built by Aspen Plus software. R134a and R1234yf are selected as working fluids because of their common use in air conditioning system. R245fa is employed as working fluid for independent ORC system as a comparison. The targets of this analysis are more power output and smaller heat transfer area. Linear weighted method is applied to optimize this multi-objective problem using the working fluid flow rate and WHR evaporating pressure as variables. The simulation results indicate that the compound system behaves better than independent system both in the power output and heat transfer area with the same working fluid. The independent system with R245fa-R134a generates the most power output of 13.01 kW. The compound system with R1234yf shows the smallest total heat transfer area and total heat transfer area decreasing ratios (THTADRs) are 6.2–14.8% comparing with independent systems.

Developmens of alternative systems for automotive air conditioning - A review

Vapor-compression refrigeration (VCR) systems are still the most widely used type of automotive air conditioning (A/C) systems in spite of their high energy consumption and negative environmental effects. Although the significant amount of research conducted during the last three decades, the automotive alternative (A/C) systems are yet immature. Despite some remaining constraints only (VCR)-type of A/C systems, powered by electric energy and used in EV’s, have reached the commercialization level. Also thermoelectric A/C systems powered by recovered exhaust energy and used for seat occupant cooling as well as (VCR) A/C systems powered by solar energy, are developed to the extent that they can be commercialized in the near future. Whereas the other alternative systems still suffer from many challenges that make them unable to satisfy the severe requirements of automotive air conditioning. Among those challenges: Large system size and complexity which do not realistically work in the demanding automotive environment, low coefficient of performance (below one for most of them) which prevents them from competing with the conventional (VCR) systems, high initial cost and lack of enough heat to power most of the systems. However alternative A/C systems have the advantage of being eco-friendly. A future development roadmap is presented to overcome the above-mentioned challenges.

차량용 CO₂ 에어컨 사이클 성능 향상을 위한 일체형 팽창기-압축기 성능 해석

A design combining the use of a compressor and expander was introduced in order to improve the cycle performance of a CO₂ automotive air conditioning system. Both the compressor and expander used were of rotary vane type and were designed to share a common shaft in a housing. Numerical simulation was carried out to evaluate the merit of the combined unit. In a typical automotive air conditioning operating conditions, the COP of the system was improved by 8.7% by the application of the combined unit. The compressor input was reduced by 5.2% through use of the expander output. In addition, about 3.06% increase in the cooling capacity was obtained through isentropic expansion in the expander. Our study noted that, as the pressure difference between the gas cooler and the evaporator becomes larger, the COP of the system improved increases unless the mass flow rate in the expander exceeds that in the compressor.