Performance Of Air Conditioning System Research Articles

METHODOLOGY FOR AUTOMOTIVE AIR-CONDITIONING CONTROL OPTIMIZATION USING ARTIFICIAL NEURAL NETWORKS

The transient nature of automotive air conditioning systems control is generally achieved through proportional–integral–derivative controllers (PID’s) parameters tunning. Due to the vast database available from decades of automotive manufacturers design and expertise, Artificial Neural Networks (ANN) might be able to identify underlying patterns to predict and properly tune the air-conditioning PID control systems under different thermal requirements. Recently, advances in computational capability have enabled compact embarked systems to rapidly solve complex, multi-variable sets of equations, thus allowing for ANN to promptly calculate tunning parameters and act upon PID controllers. As any new application, technical literature is still scarce. On this research, a coupled PID and 6-layers perceptron ANN system was devised, programmed and used to simulate how an air-conditioning system performance can be optimized through proportional–integral–derivative controllers tuning. This proposed setup response was then compared to a conventional heuristic PID tunning method (Ziegler Nichols) to demonstrate how ANN’s can more rapidly stabilize the system output.

Modeling of a solar-powered thermoelectric air-conditioning system using a random vector functional link network integrated with jellyfish search algorithm

In this study, the performance of a solar thermoelectric air-conditioning system (STEACS) is predicted using advanced optimized artificial intelligence models. A STEACS powered by solar PV panels is experimentally tested under different cooling loads varying from 65.0 to 260 W. The obtained experimental data are used to train and test the model. The model consists of a random vector functional link (RVFL) network optimized by one metaheuristic optimizer such as jellyfish search algorithm (JFSA), artificial ecosystem-based optimization (AEO), manta ray foraging optimization (MRFO), and sine cosine algorithm (SCA). The inputs of the model were time, solar irradiance, ambient temperature, wind speed, and humidity. The predicted responses of the investigated system are the input current of PV, the average temperature of the air-conditioned room, the cooling capacity, and the coefficient of performance. The accuracy of the four models is evaluated using eight statistical measures. RVFL-JFSA outperformed the other models in predicting all responses with a correlation coefficient of 0.948–0.999 and, consequently, it is recommended to use it to model STEACS system.

Performance and economic evaluation of CO2 (R744) air conditioning system driven by compressed air engine

Traditional building air conditioning uses electricity or thermal energy to drive the refrigeration cycle. The energy released by the expansion of compressed air can also be used for driving the refrigeration cycle. Moreover, the expanded low-temperature air can be used in the air conditioning system too. In this paper, three forms of CO2 air conditioning systems driven by novel reciprocating piston compressed air engines were designed, namely EAGC (Exhaust Air for Gas Cooler), EAS (Exhaust Air for Sub-cooler), and EASC (Exhaust Air for Space Cooling), to analyze the performance and economics of CO2 air conditioning systems combined with compressed air energy storage technology. Twenty-seven typical cities were selected in different climate regions in China to evaluate the systems' performance and running cost under outdoor temperature changes and different electricity prices. The results show that compared with the electricity-driven CO2 air conditioning system, the three systems can greatly improve the system COP (Coefficient of Performance) but still cannot reach the performance level of the conventional freon refrigeration systems. However, in cities like Beijing and Shanghai with the large peak-to-valley electricity price difference, EASC system compared to the electricity-driven R410A air conditioning system running costs are lower, the average running cost per hour can be saved 11.96% and 16.35%, respectively. This means that the CO2 air conditioning system with compressed air energy storage technology has a certain economic application value and can be popularized on reasonable occasions. This innovative system design can help solve the contradiction between supply and demand of building energy, realize leisure energy consumption, and reduce the economic cost of energy consumption on the demand side.

Effects of different air inlet temperatures and regeneration air inlet velocities on the performance of Hybrid Desiccant Air Conditioning System

A hybrid desiccant air conditioning unit is treated as an effective alternative to the conventional air conditioning system due to independent control of humidity, temperature, and eco-friendliness. The decrease in environmental impact and energy saving is more when the desiccant recovered by utilizing “free” thermal energy. This current work has experimented with a performance study of a hybrid desiccant air conditioning unit for typical humid and hot Indian (Aligarh) climatic conditions. Here, the effects of different air inlet temperatures at the process section, i.e. (28, 29.5, 31, 32.5, 34, 35.5 and 37°C) and regeneration section, i.e. (50-58.8°C) and different regeneration air inlet velocities (2.5 and 4.5 m/s) on the performance of hybrid desiccant air conditioning system are analyzed. Thus, optimization of performance parameters i.e. refrigerating effect, heat rejection rate, VCOP, ECOP, compressor work, dehumidification effectiveness, moisture removal capacity, DCOP, regeneration effectiveness and regeneration rate is identified for attaining maximum efficiency of hybrid desiccant air conditioning system under above operating states.

Experimental research on refrigeration performance of air conditioning system of pure electric passenger cars with economizer

Aiming at solving the problems of the high compressor discharge temperature, the high discharge pressure, the insufficient cooling capacity, and the reduced system efficiency in the air-conditioning system of pure electric passenger cars in the summer high temperature environment, this paper develops a low pressure economizer using the principle of the quasi-two-stage compression cycle. The heat pump air conditioning system of the air-supplemented pure electric passenger car is set up to study its refrigeration performance. The results show that in a high environment temperature of 50?C, compared with the non-supplemented system, the discharge temperature in the low pressure supplemental gas system drops by 13.54?C, the refrigeration capacity reduces by 2.0%, the compressor power drops by 3.4%, and the refrigeration coefficient increases by 1.4%.

Influence of the Ceiling Mounted Localized Air Distribution System Performance in the Human Body

This work presents a numerical study of the influence of the ceiling mounted localized air distribution system performance in the human thermal behavior. In his study a coupling of the Computational Fluids Dynamics and the Human Thermal Modelling is used to evaluate the thermal comfort, the indoor air quality and the Draught Risk. The input data, of the coupling numerical models, are evaluated in the Building Dynamics Modelling. The virtual chamber geometry is generated using the Computational Aided Design system and the occupants’ geometry is generated using empirical equations, based on occupant height and weight. The ADI (Air Distribution Index) and the ADTI (Air Distribution Turbulence Index), used to evaluate the Heating Ventilating and Air Conditioning system performance, depends of the thermal comfort level, the indoor air quality level, the Draught Risk level, the effectiveness for heat removal, the effectiveness for contaminant removal and the effectiveness for airflow removal. The study is made in a virtual chamber occupied by twelve virtual manikins and equipped with twelve seats, six desks and with a ceiling mounted localized air distribution system. The ceiling mounted localized air distribution system is equipped with an inlet system and an extraction system located above the head level.

Effect of Room Characteristics on Control Performance of Air-Conditioning System

Effect of Room Characteristics on Control Performance of Air-Conditioning System

Experimented plant factory’s air conditioning system performance evaluation

Experimented plant factory’s air conditioning system performance evaluation

Rheological Properties of TiO2/POE Nanolubricant for Automotive Air-Conditioning System

The enhancement of nanolubricant rheological properties can improve the performance of automotive air-conditioning systems. The rheological properties of the TiO2/POE nanolubricant were investigated in this study at 0.01 to 0.1% volume concentrations and temperatures ranging from 0 to 100°C. TiO2 nanoparticles were dispersed in the base lubricant of Polyol-ester (POE RL68H) lubricant in two steps. The dynamic viscosity was measured with an Anton-Paar Rotational Rheometer. According to the findings, the TiO2/POE nanolubricant behaved as Newtonian fluids at all volume concentrations and temperatures. The dynamic viscosity increment of nanolubricants up to 1.75% only occurred for 0.1% volume concentration and temperature of 90 to 100°C. Meanwhile, when compared to POE lubricant, nanolubricants with volume concentrations of 0.01 and 0.05% showed a decrement trend in dynamic viscosity of up to 1.8%. Finally, the TiO2/POE nanolubricant improved the rheological properties of the POE lubricant for use in automotive air-conditioning systems.

Real-time monitoring of occupancy activities and window opening within buildings using an integrated deep learning-based approach for reducing energy demand

Occupancy behaviour in buildings can impact the energy performance and operation of heating, ventilation and air-conditioning (HVAC) systems. HVAC, which uses conventional control strategies or “fixed” setpoint schedules, could not adjust to the conditioned spaces' actual requirements, resulting in building spaces being over or under-conditioned. While the unintended opening of windows can lead to substantial heat loss and consequently raises energy consumption. To optimise building operations, it is necessary to employ solutions such as demand-driven controls, which can monitor the utilisation of indoor spaces and provide the actual thermal comfort requirements of occupants. This study presents a novel vision-based deep learning framework for occupancy activity detection and recognition including the manual window operations in buildings. A region-based Convolutional Neural Network (R-CNN) model was trained and deployed to a camera for real-time detection and recognition. Based on the field experiments conducted within a case study University building, overall accuracy of 85.63% was achieved for occupancy activity detection and 92.20% for window operation detection. Building energy simulation and various scenario-based cases were used to assess the impact of such an approach on the building energy demand and provide insights into how the proposed detection method can enable HVAC systems to respond to dynamic changes within indoor spaces. Results showed that the proposed approach could reduce the over-or under-estimation of occupancy heat gains compared with the use of “fixed” or static profiles. In addition, the approach can help alert building users or managers about windows left open unintentionally, which can reduce unnecessary ventilation heat losses. Furthermore, the approach can also predict the room CO2 concentration and advise occupants about a suitable natural ventilation strategy. The study highlighted the potential of the multi-purpose detection approach, but further development is necessary, including optimisation of the deep learning model, full integration with HVAC controls and further model training and field testing.

Intelligent performance prediction of air conditioning systems based on refrigerant temperatures

Efficient management of energy in buildings necessitates the accurate evaluation of the air conditioning (AC) system performance. Ideally, the system must be operated with its cooling capacity matching the cooling load demand, and with maximum possible performance. This paper presents a simplified method that can predict cooling capacity in operative AC installations with limited input information. It is developed using an artificial neural network (ANN) with Bayesian regularization. The training data are generated by numerical simulations of operating scenarios representing the real system operation. The refrigerant temperatures at the inlet and outlet of the evaporator and the condenser are selected as inputs for the proposed method to predict the cooling capacity in relevant operating scenarios, thereby eliminating the need for a flow meter and facilitating implementation on operative systems. The ANN model is developed to capture the performance of different systems by using a data normalization method. The ANN prediction is tested on both simulation scenarios and experimental data with different nominal capacities. The results show that the ANN model can successfully predict cooling capacity variations using limited input parameters with RMSE and ΔQ-e,rel 0.09 kW and 3.99%, respectively.

Experimental study on an air-cooled air conditioning unit with spray evaporative cooling system

Improving the coefficient of performance (COP) of air conditioner with air-cooled condenser is a challenge especially in areas with hot weather. A spray evaporative cooling system is coupled with the air-cooled condenser of an air conditioning unit, and influence of different outdoor temperatures, mass flow rates of nozzles and operation modes of spray system on the performance of air conditioning system under are investigated. Experimental results show that the application of spray evaporative cooling system has significant effect on the performance improvement of the unit and the improvement rate rises as outdoor temperature increases. By using the spray evaporative cooling system in hot weather conditions, the power consumption can be reduced up by 22% and the COP can be improved by around 42.6%. Even if the spray energy consumption is taken into account, the values of COP are higher than the threshold value of the secondary energy efficiency (3.2). This study demonstrates that an air-cooled air conditioning unit coupled with spray cooling system is a kind of energy-efficient technique, which has a significant potential to improve the unit performance and reduce the electricity demand.

Design and experimental validation of a new condenser of an automotive air conditioning unit to address non-uniform air velocity distributions

• The front anti-collision beam in a car leads to air maldistribution. • A six-path condenser is an optimization of the traditional four-path condenser. • The new condenser shows better capacity with the anti-collision beam. • The cooling performance of automobile air conditioning system is improved. To improve the efficiency of automobile air conditioning and reduce the impact of non-uniform air velocity distributions caused by the front anti-collision beam on automobiles, we designed a new six-process condenser and tested it under different working conditions. A baffle was positioned to simulate the anti-collision beam during the experiment. We analyzed the condenser by itself and the system level performance of this newly designed condenser under three working conditions compared to a traditional four-process condenser. Condenser heat exchange capacity, condenser inlet pressure, system refrigerant flow rate, refrigerant flow resistance, thermal imaging of condenser outlet air, overall system cooling capacity, and coefficient of performance were compared. The coefficient of performance of the system with this new condenser improved by 8.5%, 7.8%, and 10.3% for the three tested working conditions.

An ion mass transfer model of electrodialysis regenerator for inorganic salt liquid desiccants

The solution dehumidification air-conditioning system shows great energy-saving potential in humid area, which is significant to the energy consumption in buildings as air-conditioning costs more than half energy in buildings under this climate. The electrodialysis regeneration is suitable for liquid desiccant in humid area as this method needs no heat and mass transfer with environmental air, and the heating and cooling of liquid desiccant are also not needed in this regeneration approach. In order to improve the mass transfer coefficient in electrodialysis regenerator, the ion mass transfer mechanism of liquid desiccant with ultra-high concentration is investigated in this paper. An ion mass transfer model of electrodialysis regenerator for inorganic salt liquid desiccant with ultra-high concentration is established based on the Nernst-Plank equation, which can be solved by the finite difference method. The current coefficient model is corrected and the accuracy of the ion mass transfer model of electrodialysis regenerator is verified by the experiment. Theoretical research shows that when the dehumidification requirement is met, the initial solution concentration, operating current and circulation flow rate should be reduced to achieve better performance of solution dehumidification air conditioning system.

A comprehensive review of life cycle climate performance (LCCP) for air conditioning systems

Life Cycle Climate Performance (LCCP) is a widely accepted metric to evaluate the carbon footprint of air conditioning (AC) systems “from cradle to grave.” This paper: (1) reviews the invention and evolution of LCCP, including a comprehensive timeline and bibliography; (2) documents the successful application of LCCP in the replacement of HFC-410A with HFC-32 in room air conditioners; (3) compares the conceptual frameworks and the operational approaches; and 4) reflects on the drawbacks of current LCCP research and points out possible future work. The major policy-relevant findings are: 1. The indirect emissions caused by energy consumption is 70 to 80 percent of the LCCP of AC systems in most countries but will decline in importance as electric power supply shifts rapidly from fossil fuel to renewable energy sources, which have near-zero carbon intensity; 2. The embodied greenhouse gas (GHG) emissions in refrigerant manufacture are, in most cases, negligible but the physical and chemical properties are crucial for system optimization for low carbon footprint; 3. The LCCP metric can be used for multiple purposes such as refrigerant selection and AC system architecture optimization; and 4. Data limitations in material manufacturing and the carbon intensity of electric power are the most significant challenges. Finally, this paper describes a variety of methods to fill in data gaps, including the correction factor method , the data-driven method , and the database searching method . The next-generation LCCP will be an enhanced evaluation process considering local climate, heat islands, and local power supply characteristics.

Climatic division for the design of HVAC systems

Different climate characteristics put forward different requirements for the performance of air conditioning system. Climatic division has been proposed to facilitate the selection or design of HVAC systems to match indoor cooling/heating loads of buildings better. However, humidity parameter and distinction of sensible and latent loads are usually ignored, bringing problems to the operation and control of HVAC systems. Therefore, this study proposed a novel climatic division method for China during the cooling period taking the coupling effect of cooling and dehumidification of HVAC systems into account. The humidity-based cooling degree-day was firstly taken as an index to evaluate the influence of outdoor humidity parameter. Then, 96 cities, whose cooling loads are particularly affected by the humidity, were selected for further analysis. Indoor cooling loads were calculated using EnergyPlus and the climatic division based on sensible heat ratio and total cooling load was presented. Finally, on the basis of the novel climatic division, hourly sensible cooling load and latent cooling load of representative cities in each zone were analyzed to get the characteristics of load boundary and frequency distribution. A new design method was therefore proposed and discussed, paving a new way for the customized design of HVAC systems for each climate zone.

Improving Performance of Heating, Ventilation, and Air-Conditioning System of Electric Vehicle Using Evaporative Cooling: A Model-Based Analysis

Improving Performance of Heating, Ventilation, and Air-Conditioning System of Electric Vehicle Using Evaporative Cooling: A Model-Based Analysis

Miscibility analysis of polyol-ester based oil SW32 with R404A and low-GWP refrigerant R452A

• An experimental analysis is conducted to compare the miscibility of R452A and R404A refrigerant with lubricant SW32. • The saturation vapor pressure of the refrigerant/lubricant mixture is measured for varying oil mass fraction and temperature. • Oil refrigerant phase separations are studied and a phase diagram is developed for R404A and R452A. • R452A demonstrated a higher miscibility region compared to R404A. Refrigerant/lubricant miscibility plays an important role in the overall thermal performance and reliability of refrigeration and air-conditioning systems. R452A is considred a viable replacement of R404A refrigerant due to its comparible thermophysical properties and low global warming potential. In this paper, the miscibility of a polyol ester based oil SW32 is experimentally investigated with R404A and R452A by varying the oil mass fraction from 5% to 70% over the temperature range of 243.15K to 313.15K. The results revealed R452A is completely miscible with SW32 oil up to 30% oil mass fraction over the whole temperature range considered in the study followed by R404A which showed complete miscibility up to 20% oil mass fraction. Liquid phase separation showed the presence of three different types of immisicibility present for both refrigerant at higher oil mass fractions. Moreover, the low-global warming potential alternative, R452A demonstrated an 18% higher miscibility region with SW32 oil compared to R404A.

Experimental investigation and non-dimensional regression analysis of condensation heat transfer of R-600a over finned tubes

In this study, condensation heat transfer of R-600a (Iso-butane) has been analyzed experimentally over different finned tubes varying different parameters. These parameters like saturation pressure, wall sub-cooling temperature, fin geometry, refrigerant properties, and coolant flow rate are major factors affecting the performance of refrigeration and air-conditioning (RAC) systems. The parameters were varied within the range of operating conditions for most of refrigeration and air-conditioning systems. Based upon experimental data and exclusive analysis, best performing sets of different parameters have been concluded, and also a generalized correlation in non-dimensional form covering different parameters has been developed.

Air Conditioning System Performance of a City Hotel Appraised for Energy Use Efficiency

This paper presents results of a study on split air conditioning (AC) performance of a city hotel in Bali, Indonesia. The study applied a practical global approach to appraising the performance of existing AC systems and their installation in a city hotel. The results obtained indicate that improper AC system selection and installation potentially reduces their energy performance which include COP (coefficient of performance), EER (energy efficiency ratio), and SEI (system efficiency index). The finding also shows that improper system selection and installation has damaged 54 unit compressors of 90 AC systems installed in a particular building within three years’ period. Overall number of compressors that have been damaged in three years can reach 76 units accounted for about 23.1% of the total AC systems installed in the hotel. It is also found a reduction on AC system cooling capacity.