Deep learning-based efficiency forecasting of automotive air conditioning system with variable-capacity compressors under different conditions

Carbon dioxide automotive air conditioning (AC) systems have been under development for over a decade. Although the AC system construction is important, a reliable refrigerant leakage detection system is also vital. A detailed thermodynamic simulation model and fault detection and diagnosis (FDD) system, with proposed validation plans, has been developed at Rochester Institute of Technology. A discussion of simulation models that have been developed for various compressors and heat exchangers is presented; they are compared to actual AC systems to develop a realistic experimental setup. Assumptions from previous work are examined and improved. Portions of this paper were previously published in the ECOS'05 and ECOS'07 conference proceedings.

Studies on automotive air-conditioning (AAC) systems involving compressor on-off cycling are still limited. This study focuses on improving the cycling of the AAC system using hybrid nanolubricants and hydrofluoroolefin-1234yf refrigerant. A dynamic model for an AAC system with a thermostatic switch that controls the on-off compressor was developed. The model was built in MATLAB Simulink and based on the state-space model using the fundamental conservation principles at the condenser, evaporator, and expansion valve. The experimental data were used to calculate the AAC system pressure, compressor, heat transfer coefficient of the condenser-evaporator, and expansion valve setting. The validation of the experimental data and the predicted data by the simulation suggested that the dynamic model could predict the AAC system’s performance within ±5% deviation. The AAC system operating with Al2O3-SiO2/PAG nanolubricants has a lower temperature cycling frequency than the AAC system with the original PAG lubricant, representing less energy consumed. In addition, the AAC system with hybrid nanolubricants was performed with lower power consumption and significantly higher cooling capacity than the original system. The present simulation confirmed the feasibility of hybrid nanolubricants for application in an AAC system with a thermostatic switch.

This paper presents the experimental comparative performance analysis of an automotive air conditioning (AAC) system using R1234yf and R134a. For this purpose, an AAC experiment setup used for R134a was built to obtain the drop-in performance of a new refrigerant R1234yf. Among the low global warming potential (GWP) refrigerants, R1234yf was particularly chosen due to its similar thermo-physical properties with R134a. However, the system with R1234yf could not perform as efficiently as R134a can. Therefore, an internal heat exchanger (IHX) was employed to enhance the performance of the R1234yf system. After that, the performances of R1234yf and R134a were compared under various compressor speeds and air stream temperatures. The results showed that the cooling capacity and COP of the system with R1234yf were 17.1 % and 12.4 %, respectively, lower compared to the one with R134a. However, when the IHX was introduced into the system with R1234yf, the cooling capacity and COP values were significantly enhanced by 7.9 % and 4.1 %, respectively.

<div class="htmlview paragraph">As a prelude to the assessment of the global warming impact of automotive air conditioning, fundamental scientific facts about global warming are reviewed. A comprehensive mathematical model is next developed to quantify the total equivalent warming impact (TEWI) of the automotive air conditioning. Using this model, intensive calculations are performed to determine the TEWI of the present R-134a air conditioning system as well as the proposed alternate systems. The calculated results indicate that TEWI of the present R-134a system is higher than those of the flammable subcritical systems (R-152a, R-290 and R-717) but lower than those of the supercritical carbon dioxide system (R-744) and open air (R-729) cycle system. The calculated results show that TEWI of 303 million R-134a automotive air conditioning systems in the worldwide fleet is no more than 0.14% of TEWI of the greenhouse gases emitted annually into Earth's atmosphere due to human activity. According to the TEWI reduction cost estimates developed by the Council of Economic Advisers to the U. S. President, the cost of eliminating automotive air conditioning TEWI should not exceed $12.60 per system over its life span of 12 years. Taking cognizance of the miniscule contribution of automotive air conditioning to the global emissions and the acceptable cost to eliminate them, it is concluded that the most felicitous and cost effective solution to deal with the automotive air conditioning TEWI is to continue to improve the existing R-134a system through reduction of the refrigerant emissions and enhancement of the overall system efficiency.</div>

An automotive air conditioning and heat pump (AAC/AHP) system employing refrigerants R134a and R1234yf was developed and tested in cooling and heating operation modes under broad ranges of compressor speed and air inlet temperature conditions. Using test results, various energetic and exergetic performance parameters of the system were evaluated and compared. The R1234yf system provided on average 5.8% lower cooling capacity, 0.2% higher heating capacity, 11.9% lower COP for cooling and 3.6% lower COP for heating relative to the R134a one. Furthermore, the exergetic efficiency of the R1234yf system were on average 17.6% and 14.7% lower compared to the R134a one in cooling and heating modes, respectively. The major contributor to the exergy destruction in the system is the compressor for both refrigerants and operation modes. These results reveal that R1234yf performs better in heating relative to cooling mode, and it can be used as a replacement for R134a in not only AAC but also AHP systems in expense of slightly lower energy effectiveness.

<div class="section abstract"><div class="htmlview paragraph">In automotive air conditioning systems, compressor is used to convert low pressure low temperature refrigerant into high pressure high temperature refrigerant. Various types of compressors like swash plate, rotary vane, scroll etc. are widely used in the automotive industry for air conditioning applications.</div><div class="htmlview paragraph">In rotary vane compressors, thermal protector is used as a safety device, designed to prevent the compressor from overheating during refrigerant compression process. When the discharge temperature exceeds the preset limit of thermal protector, the thermal protector will activate and stop the electrical supply to compressor clutch to stop the compressor operation thereby preventing potential damage to air conditioning system, engine, and other nearby parts of the vehicle.</div><div class="htmlview paragraph">This technical paper explores the various real-world scenarios for a hot country like India, which may result into higher discharge temperatures of compressor resulting into activation of thermal protector. The research encompasses vehicle level evaluations, replicating real world operating scenarios or misuse scenarios that may be evaluated for a vehicle with different load conditions of the air conditioning system and environmental conditions to consider the deletion of thermal protector from the system. The results of this analysis will be imperative in identifying the conditions that must be evaluated to justify the elimination of thermal protector in a particular compressor, assuring that the system's reliability and safety remains intact.</div></div>

Air conditioning in the automobile has become an important area of research. The performance of an air conditioning system in an automobile depends upon three basic important factors such as compressor speed, evaporator load, and condensing temperature. How these factors when varied affects the COP of the system have been detailed in this review paper. Several performance studies on various refrigerants (R134a, R152a, CO2 and R1234yf) used in the automotive air conditioning system operating with various conditions revealed the better COP for R152a in comparison with R134a, whereas COP of R1234yf and CO2 was observed to be slightly lower than R134a. However, safety measures must be followed while using R152a due to its slightly flammable nature (ASHRAE A2 group). In this work, various alternative air conditioning systems used for automobiles have been presented in detail.

An experimental study on the operational characteristics of a direct expansion based enhanced dehumidification air conditioning system

A bench-top automobile air conditioning (AAC) system using a thermostatic expansion valve was developed. The system was equipped with a coaxial internal heat exchanger (HEX) and charged with R1234yf, a new refrigerant used as an alternative to R134a. The system was tested at the compressor speeds ranging between 1000 rpm and 2600 rpm with increments of 400 rpm. For each compressor speed, the air temperatures at the evaporator and condenser inlets were concurrently changed between 30 °C and 40 °C with increments of 5 °C. The system was operated for the cases of employing and not employing the HEX, and totally 30 test runs were performed. Then, the first law of thermodynamics was applied to the system components to evaluate various steady state performance parameters. The considered parameters were the refrigerant mass flow rate, evaporating temperature, cooling capacity, compressor power, coefficient of performance (COP), condenser heat dissipation rate and discharge temperature of the compressor. It was determined that the experimental system employing the HEX yielded on average 0.8 °C lower evaporating temperature, 2.2% higher cooling capacity, 2.0% lower compressor power and 3.0% higher COP values relative to the system not employing the HEX. These findings reveal that the use of HEX causes a better system performance in terms of the cooling capacity, compressor power and COP. Consequently, the performance of R1234yf AAC systems can be improved with the use of HEX, and thus, the AAC systems using R1234yf can be more competitive with those using R134a.

Nanolubricant been introduced in compressor might improve the performance of automotive air conditioning system. Prior testing of the nanolubricant enhancement performance, an automotive air conditioning (AAC) system test rig base on compact car has to be developed; therefore this paper presented the development process of AAC test rig. There are 15 thermocouples, 2 pressure gauges and power analyzer were assembled on the system in order to analyse its performance. The experiment was conducted with four different charged of refrigerant. The charging was based on initial weight charged. At each quantity of refrigerant charge, performance of the AAC system was evaluated by determining three important parameters which is cooling capacity, compressor work and coefficient of performance (COP). The maximum average COP is achieved at 900 RPM is 7.07. The average and maximum COP enhancement of 7.07 % and 13.34 % were achieved by applying SiO 2 nanolubricant inside the compressor.

This paper analyzes the automotive air conditioning refrigeration cycle system, to establish the mathematical model of the compressor, condenser and evaporator. Using the Matlab to build a simulation model of the automotive air conditioning and refrigeration systems. by the simulation model of automobile air conditioning compressor, condenser and evaporator match the condensing temperature, evaporating temperature, air inlet temperature ,it is shown this model is reasonable

Comparative Performance of an Automotive Air Conditioning System Using Micro-channel Condensers with and Without Liquid-vapor Separation

Refrigerant R134a has been widely utilized in automotive air conditioning systems (AACSs); R134a has a high global warming potential (GWP) of 1430 despite having zero ozone depletion potential (ODP). Coming refrigeration systems must include refrigerants with low GWP and zero ODP. The aim of this experimental study is to evaluate the thermal performance of an (AAC) with different values of compressor speeds, i.e., (1000, 1700, and 2400 rpm) and two thermal loads, i.e., (500 and 1000 Watt) with the absence and presence of liquid suction heat exchanger (LSHX) using R134a. The results showed that adding LSHX enhanced the COP cycle by 7.18%, 10.7%, and 3.09% for the first, second, and third speed, respectively, at 500 Watt, while the enhancements were 10.27 %, 23.3 %, and 11.5 % for the first, second, and third speed, respectively, at 1000 Watt. Increasing the compressor speed decreased COP due to a reduction in RE and increased the compression effect, increasing the work done by the motor on the compressor that caused a reduction in COP. The compressor exergy destruction (X des. Comp.) decreased when LSHX was added by 6.13%, 2.22%, and 18.8% for the first, second, and third speed, respectively. However, X des. comp. increased with compressor speed due to the system’s pressure difference rise because of decreasing evaporation and increasing condensation pressures. As a result, the entropy generation increased. The increase in discharge temperature and pressure of the compressor led to a high friction force between the moving part of the compressor and the refrigerant, so the energy losses increased. Increasing the compressor speed decreased the total exergy performance of the cycle by 5.8 %, 7.5 %, and 16.7 % for the first, second, and third speed, respectively, due to increasing the compressor discharge temperature, increasing the X des. comp. and thermostatic expansion device and decreasing condenser and evaporator. Increasing X des. comp was higher than the destruction in the condenser and evaporator, which canceled the effect of others, so the total exergy performance of the cycle decreased.

This study developed a FNN model for air-conditioning system of a passenger car to predict the cooling capacity; compressor power input and the coefficient of performance (COP) of the automotive air-condition (AAC) system. An experimental rig for generating the require data is development., the experimental rig was introduced at steady-state conditions while varying the compressor speed, air temperature at evaporator inlet, air temperature at condenser inlet and air velocity at evaporator inlet. A computer simulation has been conducted. The results of predicted by FNN are compared with the values obtained from experiments. It has been demonstrated that FNN model for automotive air-conditioning systems performance prediction has high coefficient in predicting the AAC system performance.

Aiming to explore environmentally friendly working fluids replace R134a for automotive air conditioning applications, seven potential pure refrigerants were analyzed first in terms of safety, environmental characteristics, and cycle performances. It was found that the pure refrigerants have some defects when applied individually. However, using the principle of complementary advantages, the mixtures employed in automotive air conditioning can make up for the shortcomings existing in the pure refrigerants. On this basis, the thermophysical models of vapor‐liquid equilibrium, enthalpy, entropy, and critical properties of binary mixtures were established. Also, the properties and cycle performances of 14 blends were investigated, and the results indicated that the predicted models of vapor‐liquid equilibrium have high accuracy, where the average absolute relative deviations of pressures and the average absolute deviations of vapor‐phase mole fractions were less than 2% and 0.005, respectively. M1 (R13I1/R152a [30/70]) and M11 (R13I1/R290 [40.3/59.7]) showed superiorities in cycle performances and environmental and safety characteristics. Moreover, the operating pressures of which were close to that of R134a, and they were expected to become the substitutes for R134a in automotive air conditioners.