Automotive Air Conditioning Research Articles

Experimental investigation on the influence of lubricant oil on CO2 nucleate pool boiling heat transfer characteristics

As a natural working fluid, CO2 is considered the most promising alternative refrigerant to hydrofluorocarbons. In the fields of automotive air conditioning and commercial heat pumps, transcritical CO2 cycles show significant potential for performance enhancement. Although there are many studies on CO2 flow boiling in the open literature, few studies involve CO2 nucleate boiling heat transfer, which is the dominant mechanism of CO2 flow boiling heat transfer process. This study is proposed to conduct experimental investigations of CO2 nucleate boiling heat transfer. The influences of evaporation temperature, heat flux and lubricant oil addition on boiling heat transfer performance and bubble dynamic characteristics are discussed. The results show that in pure CO2 nucleate boiling, heat flux increase leads to higher bubble density and bubble diameter in bulk liquid, which in turn enhances boiling heat transfer. The effect of evaporation temperature increases on bubble diameter is significant. The reduction in bubble diameter weakens the convective heat transfer caused by bubble motion, which leads to less variation in the CO2 nucleate boiling heat transfer coefficient with evaporation temperature. Lubricant oil addition significantly changes the bubble dynamics of CO2 nucleate boiling process, leading to larger bubble density and smaller bubble diameter. Moreover, the oil diffusion at the phase interface notably affects the heat transfer performance, resulting in greater differences in the boiling heat transfer characteristics of the mixtures compared to that of pure CO2. The mixture boiling heat transfer coefficient is collectively influenced by evaporation temperature, heat flux and oil concentration. The experimental results suggest that the heat transfer coefficient of the mixture with an oil concentration of 0.5 % increases by an average of 25 % compared to pure CO2 at an evaporation temperature of 0 °C. At higher evaporation temperatures and high oil concentrations (>1%), oil addition leads to heat transfer deterioration. Findings from this work can provide a better understanding of oil effect on refrigerant boiling heat transfer and a fundamental basis for heat exchanger design of CO2 systems.

A Comparative Analysis of Machine Learning Techniques for Predicting the Performance of Microchannel Gas Coolers in CO2 Automotive Air-Conditioning Systems

The automotive industry is increasingly focused on developing more energy-efficient and eco-friendly air-conditioning systems. In this context, CO2 microchannel gas coolers (MCGCs) have emerged as promising alternatives due to their low global warming potential (GWP) and environmental benefits. This paper explores the application of machine learning (ML) algorithms to predict the thermohydraulic performance of MCGCs in automotive air-conditioning systems. Using data generated from an experimentally validated numerical model, this study compares various ML techniques, including both linear and nonlinear regression models, to forecast key performance metrics such as refrigerant outlet temperature, pressure drop, and heat transfer rate. Spearman’s correlation was employed to develop performance maps, whereas the R2 and MSE metrics were used to evaluate the models’ predictive accuracy. The linear models gave around 70% forecasting accuracy for pressure drop across the gas cooler and 97% accuracy for refrigerant outlet temperature, whereas the nonlinear models achieved more accurate predictions, with an accuracy ranging from 71% to 99%. This implies that nonlinear regression generally performs better than linear regression models in assessing the overall thermohydraulic performance of microchannel gas coolers. This research brings forth new ideas on how ML methods can be applied to enhance efficiency and effectiveness in gas coolers, contributing to the development of more eco-friendly automotive air-conditioning systems.

Impacts of non-uniform airflow over gas cooler on the performance of transcritical CO2 air conditioning

The air flowrate and air inlet temperature over gas cooler in transcritical CO2 air conditioning for vehicles are easily unevenly distributed due to the influence of upstream obstacles. The unevenly distributed airflow affects heat exchange between CO2 and air, thus influencing the cooling capacity and power consumption of the air conditioning system. This study delves into the implications of such non-uniform airflow on the operational performance of transcritical CO2 air conditioning through simulation analysis. It elucidates the mechanisms by which the uneven distribution pattern, uneven distribution direction and non-uniformity affect the cooling capacity of transcritical CO2 air conditioning system. Moreover, the conditions of inhomogeneous airflow for enhanced heat transfer are explored by decoupling inhomogeneous flow rate and inhomogeneous temperature. Results indicate that non-uniform airflow of air temperature distributed as TB-HT (high in top and low in bottom) and air flowrate as TB-HB (high in bottom and low in top) increases the cooling capacity of 27.7 % at non-uniformity of 55 %. Conversely, uneven airflow of flowrate and temperature both distributed as LR-HL (high in left and low in right) at 40 % non-uniformity leads to a wastage of compressor power up to 1/2. These findings reveal the dual impacts of non-uniform airflow on the performance of transcritical CO2 air conditioning system, which emphasizes the importance of considering these impacts when designing automotive CO2 air conditioning systems.

Research on thermal comfort of human body under localized automotive air conditioning

Abstract In this study, we design localized automotive air conditioning to balance the contradiction between the thermal comfort of the driver in the cockpit and the energy saving and environmental protection of an automobile's air conditioner. The simplified model of a certain car cockpit is selected as the research object. Three types of air outlet structures of localized automotive air conditioning are designed, and numerical simulation is performed to study flow field distribution and human thermal comfort in the cockpit under different air outlet combinations of localized automotive air conditioning. The final evaluation result indicates that the thermal comfort of the driver is good under localized automotive air conditioning. Moreover, the energy-saving effect of localized automotive air conditioning is remarkable and its cooling rate is faster. Localized automotive air conditioning achieves about 41.4% more energy saving than ordinary automotive air conditioning.

Analysis of Automotive Air Conditioning System Performance with Alternative Refrigerants to R-134a

This work analyzed the performance of the automotive air conditioning system, operating with several alternative refrigerants to R-134a. For this, a thermodynamic model of the automotive vapor compression cycle was implemented to determine the COP of the system, the refrigeration capacity, and the consumption of the compressor. The model considers the compressor rotation speed, ambient temperature, cabin temperature, air speed in the condenser, and volumetric airflow in the evaporator as operating parameters. The refrigerants chosen for the analysis were R-152a, R-1234yf, R-290, R-410A, and R-32. The simulation was carried out with climatic data from the city of Riobamba, and temperatures inside the cabin were measured experimentally. The study shows that the refrigerant R-152a has a COP 10% better than R-134a and could be an alternative for direct replacement of refrigerant. On the other hand, R-1234yf presented a COP 9% lower than that of R-134a, which requires adjustments in the sizing of components to provide the same cooling capacity as R-134a. Finally, R-290, R-410A, and R-32 refrigerants have lower performance and higher compressor consumption. Keywords: automotive air conditioning, vapor compression cycle, COP, cooling capacity, refrigerants. Resumen En este trabajo se analizó el desempeño del sistema de aire acondicionado automotriz operando con varios refrigerantes alternativos al R-134a. Para ello, se implementó un modelo termodinámico del ciclo de compresión de vapor automotriz para determinar el COP del sistema, la capacidad frigorífica y el consumo del compresor. El modelo considera como parámetros de funcionamiento la velocidad de giro del compresor, temperatura ambiente, temperatura del habitáculo, velocidad del aire en el condensador y flujo volumétrico del aire en el evaporador. Los refrigerantes escogidos para el análisis fueron el R-152a, R-1234yf, R-290, R-410A, y el R-32. La simulación se realizó con datos climáticos de la ciudad de Riobamba y temperaturas del interior del habitáculo medidas experimentalmente. El estudio muestra que el refrigerante R-152a presenta un COP 10% mejor que el R-134a, pudiendo ser una alternativa para un remplazo directo de refrigerante. Por otro lado, el R- 1234yf presentó un COP 9% menor que el del R-134a, con lo cual se requieren ajustes en el dimensionamiento de componentes para proporcionar la misma capacidad de refrigeración que el R-134a. Finalmente, los refrigerantes R-290, R-410A y R-32 presentan un menor rendimiento y mayor consumo de compresor. Palabras Clave: aire acondicionado automotriz, ciclo de compresión de vapor, COP, capacidad frigorífica, refrigerantes.

Study of the Incidence of CO and CO2 Gas Emission Levels and Temperature, of the Automotive Air Conditioning System Inside an Interprovincial Bus at Different Environmental and Operating Conditions

The present curricular integration work proposes to analyze the levels of CO and CO2 gas emissions in the passenger compartment of an interprovincial bus, considering environmental and functional conditions, to obtain values that are analyzed, allowing to know the comfort conditions of the passenger, and considering an ideal temperature of 22∘C. The study was carried out on the selected route during the bus route, both in the central and peripheral urban sectors, where the influx of users is notable throughout the day. The field measurements were carried out (August 5-10), inside the passenger compartment of an interprovincial bus, considering operating variables of the automotive air conditioning system, such as condition, OFF, air recirculation, and air renewal. Data were collected in the passenger compartment’s front, middle, and rear sections. An IAQ TESTO 440 gas analyzer was used through the CO2 and the CO probe, located at a height of 1.1 m from the floor, which was considered as the average respiratory level of the passenger, generating the data in lapses of 10 min. Once the analysis has been carried out, the data is tabulated and the concentration levels of emissions produced by the users’ exhalation are determined. Finally, by tabulating the data, it was possible to know the concentration percentages of the gas emissions produced by the users, in the different locations of the passenger compartment. It is recommended that for future research, a study be carried out with data collected from a full day of travel. Keywords: Air conditioning, optimization, gas emissions, air quality, passenger cabin, comfort, gas analyzer, interprovincial transport. Resumen Este trabajo de integración interna propone analizar el CO2 y las emisiones de CO2 en el habitáculo de los autobuses interurbanos, teniendo en cuenta las condiciones ambientales y funcionales, para obtener los valores analizados, que permitan conocer el estado de confort del pasajero. Teniendo en cuenta la temperatura ideal de 22∘C. En la ruta seleccionada, el estudio se realizó a lo largo de la ruta del bus, tanto en la zona céntrica como en la semiurbana donde hay una gran cantidad de usuarios a lo largo del día. Se realizaron mediciones de campo (del 5 al 10 de agosto) al interior del habitáculo de un bus interurbano, teniendo en cuenta variables operativas del sistema de aire acondicionado del vehículo como condición, apagado, recirculación de aire y cambio de aire. Los datos se recopilan en las partes delantera, media y trasera de la cabina. El analizador de gases IAQ TESTO 440 se utiliza como medio para los detectores de CO2 y CO, colocado a una altura de 1,1 metros del estanque, que se considera la frecuencia respiratoria media del pasajero, produce datos en un tiempo breve en 10 minutos. Una vez que se completa el análisis, se tabulan los datos y se determina la concentración exhalada del usuario. Finalmente, es posible conocer el porcentaje de emisiones generadas por el usuario, en diferentes puntos del habitáculo. Se recomienda que se realice un estudio con los datos recopilados en el transcurso de un día de viaje para futuras investigaciones. Palabras Clave: emisiones de gases, transporte interprovincial, analizador de gases, aire acondicionado, calidad del aire, habitáculo de pasajeros.

Energy and Exergy Analysis of R600a as a Substitute for R134a in Automotive Air Conditioning System

Energy and Exergy Analysis of R600a as a Substitute for R134a in Automotive Air Conditioning System

Numerical analysis of scroll compressor performance with pre-discharge valve for low-temperature heat pumps

Scroll compressors are a crucial component of automotive air conditioning systems. When operating at off-designed working conditions, over-compression can occur in the scroll compressor. A pre-discharge valve (PDV) is proposed to enhance the performance of the scroll compressor under off-design working conditions. The performance of the scroll compressor with a PDV for a low-temperature heat pump system is simulated. The results show that the scroll compressor with the PDV structure has lower pressure in the compression chambers and improved over-compression compared to conventional scroll compressors. The use of the PDV also leads to a reduction in the temperature of the refrigerant gas in the compression chambers and a decrease in the leakage between the compression chambers. As the evaporating temperature increases from −25 °C to −5 °C, the mass flow rate and volumetric efficiency increase, and the discharge temperature decreases. At an evaporating temperature of −5 °C, the discharge temperature at the center discharge port of the scroll compressor with the PDV is reduced by 2.4 °C compared to the conventional scroll compressor. The input power of the scroll compressor is reduced by 165.4 W–897.7 W. The volumetric efficiency and the isentropic efficiency are improved by 0.13 % and 6.63 % respectively.

Fuzzy-based thermal management control analysis of vehicle air conditioning system

Automotive air conditioning (ACC) system designers faced unique challenges in satisfying customer demands for efficient and comfortable operation across a broad temperature range. The AAC system's effective or fixed temperature setting makes this possible. Many climate control models, like the state flow switching controller in MATLAB control, must handle heating and cooling due to a single Simulink/environment software and frequently contain steady-state error (SSE). The present research proposes to design an automatic temperature control scheme and fuzzy logic control (FLC) for an automotive air-conditioned (AAC) system. In addition, it employs MATLAB Simulink/environment software to model the fuzzy control technique to analyze the AAC system's response. A simulation has been set up to evaluate the suggested system performance to match a selection of user-specified reference temperatures and compressor speeds. Compared with a PID-controlled AAC system, the proposed FLC-based system reduced the undershoot to only 2.30% from 33.30% respectively, and was robust, quicker, and better at controlling temperature.

Transitioning to low GWP refrigerants in automobiles: A numerical simulation study on R1234yf/R152a’s heat transfer characteristics in porous microchannels

Automobile air conditioning systems significantly contribute to vehicle energy consumption. The transition to new, environmentally sustainable refrigerants in place of traditional ones is a critical trend shaping the future of this industry. The prevalent refrigerant R134a, used in automotive air conditioning, is environmentally detrimental, necessitating the development of low Global Warming Potential refrigerants as viable long-term alternatives. This study examines the flow heat transfer characteristics of the proposed refrigerant blend R1234yf/R152a in porous microchannel tubes via numerical simulation. It assesses the impact of heat flux, mass flow rate, saturation temperature, and wall superheat on the Jakob number, vaporization core density, and boiling heat transfer coefficient. Furthermore, it compares these parameters with those of R134a and R1234yf to evaluate the potential of R1234yf/R152a as a substitute. The findings indicate that the Jakob number differences among the three refrigerants are negligible. Notably, R1234yf/R152a consistently exhibits higher vaporization core density and the highest boiling heat transfer coefficient, coupled with the lowest pressure drop, thereby affirming its suitability as a heat transfer-efficient alternative. These insights could inform the enhancement and gradual transition from R134a in automotive air conditioning systems.

Numerical simulation of flow distribution characteristics in carbon dioxide microchannel evaporator

Microchannel heat exchangers find widespread use in household and automotive air conditioning due to their compact structure and high efficiency. However, two-phase refrigerant flow mal-distribution in microchannels limits their application. For the CO2 heat pump, the performance reduction by flow mal-distribution could be as large as 20%. This study proposed an approach to mitigate flow mal-distribution by inserting a perforated tube into the header of a microchannel evaporator in CO2 heat pump. Numerical simulations were carried out to investigate the impact of perforated tube parameters and CO2 inlet conditions on flow distribution. Results show a 24.4% increase in total non-uniformity (S) of flow distribution with a perforated tube. A higher number of openings and smaller diameters enhance uniformity, with the 10-hole, 2 mm diameter perforated tube proving most effective. Additionally, the most uniform flow distribution was achieved at an inlet CO2 mass flow rate of 30 g/s and a vapor quality of 0.2. And the flat tubes with an insertion depth of 5 mm and a cross-section of 16 × 2 mm is the most beneficial for uniform flow distribution.

Tribology Evaluation on a Four-Ball Tribometer Lubricated by Al2O3/PAG Nanolubricants

Nanolubricants can improve the tribological properties for application in automotive systems. By reducing the friction rate of the internal components with nanolubricants, the service life of a compressor used in automotive air conditioning (AAC) can be extended. The investigation aims to determine the optimal volume concentration of nanolubricants for achieving the highest performance in tribological properties. Al2O3 nanoparticles dispersed in a polyalkylene glycol (PAG ND12) base at volume concentrations of 0.01%, 0.03%, and 0.05% were investigated to improve the lubrication system in the AAC compressor. The stability investigations were carried out by comparing absorbance conditions using a UV-Vis Spectrophotometer at each volume concentration for 210 days. Koehler's four-ball tribometer was used to measure coefficient of friction (COF) and friction torque at a load of 40.0 kg and a speed of 1200 rpm. The stability study of nanolubricant yielded average absorbance values of 0.752, 0.755, and 0.684, respectively. The average COF values of the nanolubricants of 0.01%, 0.03%, and 0.05% were 0.104, 0.078, and 0.117, while the pure lubricant was 0.095. Further investigation on friction torque resulted in a decrease in the pure lubricant of 0.064%, and for nanolubricant Al2O3/PAG ND12, a decrease of 0.087%, 0.057%, and 0.092%, respectively. The results indicated that a concentration of 0.03% produced the greatest reduction in COF and torque, namely 0.0078% and 0.0578%, correspondingly. Therefore, it is recommended to use Al2O3/PAG ND12 nanolubricant at a volume concentration of 0.03% because it is the most optimal in terms of stability and has the highest COF and frictional torque reduction.

Investigation Of Automotive Air Conditioning Using Eco-Friendly R600a As An Alternative Refrigerant To R134a

One of the main reasons for replacing R134a with R600a is the impact of global warming. In this study, a numerical approach was applied to investigate changes in automotive air conditioning (AAC) performance due to the replacement of R134a with R600a. A thermodynamic evaluation was carried out with evaporating and condensing temperatures of 5oC and 45oC, respectively. The study simulates AAC performance at five engine rotation speeds: 1000, 2000, 3000, 4000 and 5000 rpms. The results show that replacing R134a with R600a reduces the cooling capacity and input power by 45.42% and 47.02%, respectively. However, due to the dominant decrease in input power as compared to the decrease in cooling capacity, the COP of AAC increases by 2.93%. Although the increment in COP is relatively small, this replacement greatly contributes to the reduction of greenhouse gas emissions that causes the problem of global warming due to the lower GWP of R600a as compared to R134a.

The emission reduction potential and cost-effectiveness of low-GWP refrigerants in electric vehicle air conditionings

Electric vehicles play a crucial role in the carbon neutrality transformation of urban transportation, provided that they are powered by electricity generated from renewable (rather than fossil-based) generation sources. However, the substantial indirect emissions from electric vehicle air conditioning energy consumption and the significant direct emissions from HFCs (hydrofluorocarbons) refrigerants pose considerable challenges. In order to identify low-GWP (global warming potential) refrigerants -such as R1234yf, R744, and R290 - that can effectively minimize carbon emissions while maintaining certain cost-effectiveness, this paper establishes the relevant life-cycle analysis and life-cycle cost analysis models for electric vehicle air conditioning. The results obtained show that, in 2022, the total carbon emissions of China’s automotive air conditioning fleet were approximately 162 million tons CO2-eq. The nationwide average carbon emissions ranking of various refrigerant heat pumps is R290 < R1234yf < R744 < R134a. The Net Present Value (NPV) of the life cycle cost for R134a electric vehicle heat pump is estimated to be around 11,500 yuan. Among the three low-GWP refrigerants, the life cycle cost of R290 is significantly lower than that of R134a under nationwide average conditions, while R744 exhibits the best life cycle performance in certain cold cities/regions.

Experimental investigation of air-conditioning electrical compressor using binary TiO2–SiO2 polyol-ester nanolubricants

As electric vehicles (EVs) continue to replace conventional gasoline vehicles, maintaining thermal comfort within the car requires additional energy to operate the automotive air-conditioning (AAC) system. This work aims to optimise the electrically driven compressor (EDC) system utilising polyol-ester (POE)-based binary nanolubricants to enhance performance and minimise the size of the EV battery and AAC components. A binary nanolubricant was formulated using a two-step method of formulation. The TiO2–SiO2/POE binary nanolubricant was prepared at different volume concentrations ranging from 0.01 to 0.1 %. The experiment was conducted for the 1200–3840 rpm compressor speed with different initial refrigerant charges between 120 and 160 g. The heat absorption rose by up to 44.2 % while utilising the binary nanolubricant at a volume concentration of 0.03 %. The coefficient of performance (COP) reached its maximum value of 2.43 at a refrigerant charge of 160 g and compressor speed of 1860 rpm. Furthermore, the binary nanolubricant significantly reduced the expansion valve discharge temperature, exhibiting a substantial decrease of up to 51.6 %. The highest COP increment, up to 23.4 %, was achieved at a volume concentration of 0.03 %. Hence, it is recommended to utilise 0.03 % TiO2–SiO2/POE binary nanolubricant to achieve optimal performance in the AAC-EDC system.

Performance of adjustable multilayer film based on radiation cooling and electrochromism

Energy and environmental challenges caused by the excessive consumption of fossil fuels are major concerns worldwide, and the use of automotive air conditioning can increase total fuel consumption by 10% to 30%, thereby exacerbating these problems. To reduce the energy consumption for automotive air conditioning, a multilayer-film design based on radiative cooling and electrochromic modulation is proposed for regulating the temperature inside vehicles. The designed multilayer-film not only passively realizes temperature drop but also actively regulates the entry of solar radiation, which can help the vehicle air conditioning system to adjust the interior temperature autonomously. To verify its effectiveness, a film-applied empty box device is designed for radiometric temperature measurement. Experimental results indicate that the maximum interior temperature drop of the multilayer film increases by approximately 9.8 ℃ compared with that of single-layer films in the sunlight irradiation, and dynamic temperature regulation of about 4.6 ℃ can be achieved by adjusting the transmittance of the multilayer film. To study the environmental adaptability of the multilayer film, experiments are conducted on an outdoor film-applied device during the summer and winter in Shenyang, China (<inline-formula><tex-math id="Z-20241025175516">\begin{document}$\rm 41^\circ44'N, 123^\circ39'E$\end{document}</tex-math></inline-formula>), the place which is characterized by a typical temperate continental climate. Results indicate that under high temperature conditions of 30–40 ℃ in summer, the maximum internal temperature drop of the multilayer film reaches 12.9 ℃; while under low temperature conditions of 0–15 ℃ in autumn and winter, the maximum internal temperature drop is only 1.9 ℃, preventing the interior temperature from being too low. In addition, the maximum interior temperature drop increases with the solar radiation intensity and ambient temperature increasing. Therefore, the proposed multilayer-film design, with its potential for temperature self-regulation, provides a promising solution for reducing energy consumption and improving passenger comfort.

Predviđanje performansi sistema za klimatizaciju automobila kroz duboko učenje

Automotive Air Conditioning System (AACS) involves phase change of the refrigerant, to provide a comfortable environment in the vehicle cabin. The phase change is governed by many complex equations. Therefore, a technique that can validate the results and predict the system performance is required to avoid tedious calculations. Deep Neural Networks (DNN) are better at learning complex non-linear relationships between performance metrics. Experimental data is used to train the specified DNN model. Compressor speed, air temperature at the inlet of the evaporator, and refrigerant flow rate are used as input, while coefficient of performance, compressor work, and heat loss have been used as output parameters to train the model. Predicted results are compared by using statistical measures such as Root Mean Square Error, Mean Square Error as well as Correlation Coefficient. Based on the results obtained, the specified DNN model can be effectively used in predicting and validating the performance of the AACS.

Investigating New Environmentally Friendly Zeotropic Refrigerants as Possible Replacements for Carbon Dioxide (CO2) in Car Air Conditioners

The widespread use of automobiles and the increased duration spent within automobiles equipped with air conditioning systems have prompted various countries to enforce regulations that advocate for eco-friendly cooling substances (refrigerants) characterized by a slight global warming potential (GWP) and the absence of an ozone depletion potential (ODP). The imperative for automobiles to possess air conditioning systems that are both high-performing and eco-conscious has emerged as a means to mitigate their ecological impact, reduce fuel usage, and minimize carbon emissions. Zeotropic refrigerants, with a lower GWP than traditional alternatives, contribute to sustainability in car air conditioning by reducing the environmental impact and enhancing the energy efficiency, aligning with global regulations and fostering innovation in the automotive industry. This shift signifies a commitment to mitigating climate change and adopting environmentally conscious practices. The objective of the present study is to introduce blends of zeotropic refrigerants based on CO2 (R-744), namely R455A (a blend of R-744, R-32, and R-1234yf), R469A (a blend of R-744, R-32, and R-125), and R472A (a blend of R-744, R-32, and R-134a), to enhance the thermodynamic performance of pure CO2 refrigerant. Through the utilization of the Aspen HYSYS V11 software, an investigation is carried out involving thermodynamic energy and exergy analyses, as well as system optimization for an automotive air conditioning (AAC) system utilizing these novel zeotropic refrigerant blends, in comparison with the use of R-744 as the refrigerant. The study delves into the impact of parameters such as average evaporator temperature, condenser/cooler pressure, refrigerant flow rate, and condenser/cooler outlet temperature on AACs’ output parameters and subsequently presents the findings. The outcomes reveal that, under equivalent operational circumstances, the adoption of R455A, R469A, and R472A offers improvements in coefficient of performance (COP) by 35.4%, 18.75%, and 2%, respectively, when compared to R744. This shift is advantageous as it mitigates leakage-related issues stemming from the elevated operational pressure of R744 and eliminates the need for cumbersome equipment. R455A and R469A obtain the greatest COP and exergy efficiency (ηex) values, measuring 4.44 and 4.55, respectively, at the identical operating conditions with optimal condenser/cooler pressures of the examined blends. Furthermore, eco-friendly refrigerants R455A and R472A are recommended for integration into AAC systems in vehicles, as they help combat global warming and protect natural surroundings and leakage issues.

Dynamic Characteristics of an Automotive Air-Conditioning Electromagnetic Clutch

The automotive air conditioning (AC) electromagnetic clutch plays a crucial role in accurately controlling power transmission between the engine and the compressor, ensuring the proper operation of the AC system. The aim of this paper is to provide high-quality experimental data for researchers who are interested in simulating the dynamic process of an AC electromagnetic clutch and also to assess the adaptiveness of empirical equations to describe the AC electromagnetic clutch performance that is limited in discussion in existing studies. In this study, an automotive AC electromagnetic clutch characteristic test system was employed along with an infrared (IR) camera to conduct comprehensive experimental analyses. The test system enabled the evaluation of various parameters, including the clutch torque output, compressor exhaust pressure, and temperature of the friction surface. The results revealed that the torque and exhaust pressure were closely associated with the on/off time and rotational speed, with a peak value observed around 3000 rpm. Additionally, longer break-in time, higher rotational speeds, and shorter on/off time led to varying increases in the temperature of the friction surface. These findings provided a theoretical foundation for optimizing the design and control of automotive AC electromagnetic clutches. By enhancing design or adjusting control strategies, these clutches can better handle high-load and high-frequency working conditions.

Generating Correlations for Specific Volume, Enthalpy, and Entropy of Opteon: Utilizing a Novel Data Fitting Method

Establishing precise data correlations is a fundamental necessity for effective design, simulation, and optimization of chemical processes. While several correlation-generating methods for data fitting exist, each brings a unique degree of complexity and accuracy. This study introduces a distinctive method, appropriately named, Proportional Nodes Method, for correlating data on surfaces with two independent variables, focusing on precise estimations of correlations for boundary curves and nodal variation at selected points. The application of the proportional node method results in a lower average percentage deviation than the Chebyshev polynomial method (±0.978 for the method utilizing Chebyshev polynomials and ±0.5378 for the Proportional Nodes Method). This novel method exhibits lower complexity and generates correlations with superior simplicity and accuracy. Furthermore, the method effectively develops correlations for three properties—specific volume, enthalpy, and entropy of superheated Opteon, a widely-used refrigerant in automotive air-conditioners. The resulting data shows a satisfactory percentage deviation from the actual data (<+0.22% for a specific volume, <+0.124 for enthalpy and <+0.125 for entropy). In addition, correlations have been generated for the saturated vapour. This method's potential extends to developing correlations for non-overlapping data with two independent variables, making it a powerful tool for chemical process optimization.