Automotive Air Conditioning System Research Articles

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.

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

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

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.

Performance investigation of CO2 automotive air-conditioning system with ejector at 45 °C ambient temperature

The ejector-expansion system design is an effective approach to improve the cooling performance of transcritical CO2 systems. In this study, a transcritical CO2 air-conditioning system with an ejector for electric vehicles is built up to experimentally investigate the cooling performance at an extreme temperature of 45 °C. The performance improvement is evaluated compared to the corresponding basic system. The effects of electronic expansion valve's (EXV) opening, compressor speed, and fresh air ratio are analyzed. The results show that the ejector can effectively improve system COP by 4.61–16.52 % under test conditions. At 45 °C/27 °C (out-cabin/in-cabin) condition, the optimal COP of 1.52 can be obtained at EXV's opening of 65 %. The entrainment ratio significantly goes up from 0.22 to 0.60 as EXV's opening increases.

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.

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.

Performance analysis of automotive air conditioning systems with electric compressors using R1234yf refrigerant: Insights into power consumption, cooling capacity, and energy efficiency

R1234yf, a low global warming potential (GWP) refrigerant, offers a promising alternative to traditional refrigerants like R134a. This study analyzes automotive air conditioning systems (AAC) equipped with electric compressors and utilizing R1234yf refrigerant. The interrelationships between refrigerant charge, compressor speed, power consumption, cooling capacity, and energy efficiency are examined. The results show that increasing refrigerant charge and compressor speed leads to higher power consumption due to increased compressor work. However, higher refrigerant charges and compressor speeds improve cooling capacity in line with heat transfer principles. As refrigerant charge and compressor speed increase, the energy efficiency, measured by the Coefficient of Performance (COP), tends to decrease, indicating a trade-off between cooling capacity and energy efficiency. Optimizing refrigerant charge and compressor speed is crucial to strike a balance between cooling performance and energy efficiency. R134a outperforms R1234yf, with an average percent difference in COP approximately 25% higher at all compressor speeds. This study contributes to the understanding of AAC system performance and guides the development of energy-efficient automotive air conditioning. Future research can further explore system components and conditions to enhance energy efficiency and advance air conditioning technology.

Energetic performance and life cycle carbon emission of CO2 automotive air conditioning system with an evaporative gas cooler and a dual-evaporator configuration in China

Enhanced actions on climate change have led CO2 air conditioner to take center stage in automotive field. However, its inefficient performance in hot climates limits its further application. A dual-evaporator (D-E) configuration, an evaporative gas cooler (EGC), and their combination (D-E + EGC) were first integrated with the system and experimentally studied in this paper in an attempt to alleviate this problem. Annual energy consumption and life cycle climate performance (LCCP) under four modes (baseline, D-E, EGC, and D-E + EGC) in China were estimated. Results show D-E increases evaporation pressure and EGC is able to decrease discharge pressure. D-E + EGC combines the advantages of both. Thus, improvement percentage in coefficient of performance (COP) brought by D-E + EGC is the highest, followed by those of EGC and D-E. This percentage is more significant at higher ambient temperatures, and even reaches 67.4 % at 45°C outdoor condition. In any mode, annual energy consumption and LCCP in southeast China are double or triple of those in other regions, which shows this system is of high energy consumption and high emission in southeast China. Compared with baseline mode, annual energy consumption and LCCP can be reduced by 3 ∼ 7 % for D-E, 14 ∼ 16 % for EGC, and 18 ∼ 22 % for D-E + EGC. Specifically, D-E + EGC could save up to 890 kWh of electricity and reduce carbon emission by up to 440kgCO2 per vehicle, indicating this technique is a promising way to reduce energy consumption and carbon emission for vehicles equipped with CO2 air conditioners.

Tribology Performance of TiO2-SiO2/PVE Nanolubricant at Various Binary Ratios for the Automotive Air-conditioning System

Tribological properties are crucial for air-conditioning system performance. The properties can be improved using nanolubricant. However, the effect of the binary ratio of hybrid nanolubricants on the tribological performance of automotive systems is limited in the literature. Therefore, the present study investigates the tribology performance of TiO2-SiO2 nanolubricants for application in automotive air-conditioning (AAC) systems. The dispersion of TiO2 and SiO2 into PVE lubricant was carried out using a two-step method. Subsequently, the dispersion stability was assessed qualitatively and quantitatively. The samples were characterised by a volume concentration of 0.010%, with variations in the mixture ratio of 20:80, 40:60, 50:50, 60:40, and 80:20. Coefficient of friction (COF) and wear scar diameter (WSD) values were determined using the Koehler Four-ball Tribo Tester and Light Compound Microscopy. The investigation revealed that each sample experienced a reduction in COF, with the 40:60 ratio demonstrating the best ratio with the most significant decrease of 37.09%. At the same time, the COF decreased by 8.34%, 2.12%, 7.37%, and 15.11% for the nanolubricant samples at 20:80, 50:50, 60:40, and 80:20, respectively. The WSD evaluation showed that the 40:60 ratio has the lowest scar diameter of 0.0344 mm and a 37.09% wear rate decrease compared to pure lubricant. Each sample exhibits superior performance when evaluated for tribological characteristics and performance, particularly in the case of nanolubricants with the 40:60 ratio. The TiO2-SiO2/PVE, characterised by a volume concentration of 0.010%, has remarkable efficacy across different binary ratios, making it highly recommended with a 40:60 ratio for lubricating AAC compressor systems.

Operational stability influenced by lubricant oil charge in the CO2 automotive air conditioning system

In a vapor compression refrigeration system, the oil enhances the efficiency of the compressor but impairs the performance of the heat exchanger. This paper focuses on the experimental study of the influence of oil quantity on the operational stability of CO2 air conditioning system. The operational stability of the system under different oil charge quantity and operating conditions is studied. The experimental results indicate that when the oil circulation rate increases to a certain value, the adjustment of electronic expansion valve (EXV) opening or the compressor speed will cause system fluctuation and the outlet of evaporator gets close to no superheat. The critical oil circulation rate of the experimental system is about 9.2 %. The analysis of the fluctuation shows that it becomes more severe with the increasing of the refrigerant mass flow rate. When the mass flow rate increases from 210 kg∙h − 1 to 250 kg∙h − 1 at 7000 r min−1 of compressor speed, the fluctuation frequency increases from 0.072 Hz to 0.095 Hz. The occurrence of unstable phenomena has remarkable impact on system performance, the maximum difference of this system in instantaneous cooling capacity and COP during the fluctuation period is respectively 0.5 kW and 0.13.

Silver Nanowire-PVB Composite for Reflective Heat Coating

Automotive air conditioning (AAC) is essential, particularly in tropical countries like the Philippines, where temperatures can go beyond 40 °C during the summer. AAC system is installed for the comfort and safety of passengers. However, AAC may consume up to 30% of the fuel and increase fuel consumption by up to 20%. Consequently, increasing fuel consumption can lead to high costs and greenhouse emissions worldwide. Commercially available car tints can block harmful ultraviolet (UV) rays but selectively block IR rays which primarily cause heating. Therefore, sustainable cooling solutions must be developed. This study developed a silver nanowire (AgNW)-PVB (polyvinyl butyral) composite spray coating. The coating decreased the transmittance by at least 30% in the UV region and at least 25% in the near-infrared (NIR). Average transmittance in the visible region (Vis) is as much as 63.50% which highly depends on the concentration of PVB and AgNWs. More AgNWs decrease the transmittance at UV, Vis, and NIR regions.

Performance evaluation of ecofriendly R1234ze(E) refrigerant in an automotive air conditioning system

AbstractA mathematical model for an air conditioning system used in five‐seater cars is developed with R1234ze(E) and R134a refrigerants, consisting of real system geometry like an evaporator, compressor, condenser, and thermostatic expansion valve. The mathematical model includes refrigerant properties, heat transfer, and pressure loss correlations for two‐phase and single‐phase regions. The performance parameters of a system like evaporator cooling duty, condenser heat loss, compressor power, refrigerant flow rate, and compressor volumetric efficiency obtained from a mathematical model are validated with the results of an experimental facility developed with R134a. The uncertainty analysis performed for the testing facility showed below 11% deviation. The simulation and experimental results showed an overall 10%–15% difference. It is found that the experimental cooling capacity with R134a and numerical cooling capacity with R134a show a 4%–12% variation, experimental cooling capacity with R134a and numerical cooling capacity with R1234ze(E) show a 7%–20% variation, and numerical cooling capacity with R134a and numerical cooling capacity with R1234ze(E) show a 5%–15% variation for the given range of compressor speed (500–1500 rpm), and condensing temperature (26–45°C). The study concluded that R1234ze(E) could potentially replace R134a because it has similar thermophysical properties and an average performance difference of up to 10% with R134a. Due to the limitations of the electric motor used to drive the compressor, tests in the current study were conducted at modest compressor speeds (500–1500 rpm). Future research will focus on experiments with high compressor speed (in the range of 1500–4000 rpm) and R1234yf and R1234ze(E) refrigerants for performance evaluation of automobile air conditioning systems.

Design of a Cold Storage with R507A Refrigerant for the Preservation of Twenty-Five Tons of Apples in the Ankara Province

In the absence of proper humidity and temperature conditions, undried fresh foods will experience physiological and biological deterioration, resulting in mass loss and the development of mold. Thanks to this rationale, humanity has endeavored to keep food products from deteriorating. This can be observed through the use of cold rooms constructed by the Ancient Romans using clay and the cooling chambers known as "Yakhchāl" developed by the Persians. The advancement of refrigeration technology has persisted since the era of ancient civilizations. The advent of refrigeration cycles has significantly streamlined the implementation of containment technology. The presence of these systems in residential settings can be attributed to the development of the vapor compression refrigeration cycle and the compact nature of this technology, which enables convenient freezing or cooling of products for storage purposes. Vapor compression refrigeration cycles are still widely employed in various applications, such as office and automotive air conditioning systems, refrigerators, and industrial cold rooms. This study aims to develop an industrial cold room design tailored explicitly for storing and transporting apples, a perishable agricultural commodity. The primary objective is to ensure that the apples are maintained in optimal humidity and temperature conditions, thereby preventing any degradation, even when handling large quantities in Ankara.