Characteristics Of Air Conditioning System Research Articles

Improvement for energy efficiency and control characteristics in variable air volume system using in-situ sensor calibration method based on autoencoder

The accuracy of sensor measurement has an important influence on energy efficiency and control characteristics of air conditioning systems. However, the sensor will inevitably have errors due to sensor installation location or aging in the practical system. In previous studies, the sensor virtual in-situ calibration (VIC) method is proposed to diagnose and calibrate sensor faults based on physics-based methods with plenty of sensors. However, the basic sensors are only installed due to the cost and limited installation space in the practical system, which restrains this method. To address this problem, the autoencoder (AE) based on the internal relationship between sensor variables is applied to establish the sensor model to achieve calibration. This paper studies the applicability of the AE that constructs sensor models with limited sensors, and the accuracy of the VIC method under different working conditions. The results show that the AE can well realize the sensor model construction with high accuracy, which lays a foundation for the implementation of the VIC method. Meantime, the accuracy for different scenarios of the single fault is more than 90.75% after calibration, the concurrent fault can also reach more than 88.5%. The supply air temperature calibration will make the continuous regulating valve keep the normal opening to maintain the air volume and ensure the stability of indoor temperature. The static pressure calibration will increase the energy efficiency of the supply fan by 17%, make the VAV box adjust normally, and avoid the disorder of the control loops. The differential pressure sensor calibration will increase the energy efficiency of the water pump by 21%, and ensure normal water flow. Meantime, the calibration of three sensors reduces the time to reach a stable state by more than 20.6%. The VIC method based on AE makes the application scenario of sensor fault calibration more extensive and universal.

Computational fluid dynamics simulation and performance optimization of an electrical vehicle Air-conditioning system

In vehicles, air conditioning tends to offer efficient thermal conditioning and air circulation inside cabin for passenger comfort from different climate variation. The working performance of air conditioning system in vehicles is an essential factor for thermal comfort and driving safety of the passenger compartment of vehicles. Therefore, it is of great significance to construct a numerical simulation model for theoretical analysis and performance evaluation of vehicle air conditioning system. In current research, the air conditioning system of an electric vehicle is taken as the research subject. Internal flow field characteristics of air conditioning system is investigated by Computational Fluid Dynamics (CFD). Results show that the air flow in air-conditioning system is relatively smooth, and the velocity distribution in the front windshield A area and the driver's field of vision of the left and right windows is not ideal when the defrosting-demisting mode is on; the velocity and air quantity distribution of the two outlets in the middle air duct are not uniform under blowing mode. In view of the uneven distribution of velocity and air quantity, the corresponding optimization scheme is proposed. After optimization, the cell relative velocity of the front windshield is significantly improved, and velocity distribution of the side window glass is slightly increased and the defrosting-demisting performance meets the vehicle defrosting requirements of national standard; after optimization, the air quantity distribution of the air ducts at blowing mode is more uniform, which is conducive to the comfort of the passenger compartment.

Systematic Method for the Energy-Saving Potential Calculation of Air-Conditioning Systems via Data Mining. Part I: Methodology

Air-conditioning systems contribute the most to energy consumption among building equipment. Hence, energy saving for air-conditioning systems would be the essence of reducing building energy consumption. The conventional energy-saving diagnosis method through observation, test, and identification (OTI) has several drawbacks such as time consumption and narrow focus. To overcome these problems, this study proposed a systematic method for energy-saving diagnosis in air-conditioning systems based on data mining. The method mainly includes seven steps: (1) data collection, (2) data preprocessing, (3) recognition of variable-speed equipment, (4) recognition of system operation mode, (5) regression analysis of energy consumption data, (6) constraints analysis of system running, and (7) energy-saving potential analysis. A case study with a complicated air-conditioning system coupled with an ice storage system demonstrated the effectiveness of the proposed method. Compared with the traditional OTI method, the data-mining-based method can provide a more comprehensive analysis of energy-saving potential with less time cost, although it strongly relies on data quality in all steps and lacks flexibility for diagnosing specific equipment for energy-saving potential analysis. The results can deepen the understanding of the operating data characteristics of air-conditioning systems.

Transitioning to high efficiency air conditioning in Saudi Arabia: A benefit cost analysis for residential buildings

This paper assesses the benefits of transitioning to high efficiency air conditioning (AC) equipment for existing units specific to the residential building stock in the Kingdom of Saudi Arabia (KSA). The analysis is based on a calibrated residential building stock model for Saudi Arabia supported by national statistics regarding the characteristics of AC systems. Various housing prototypes, vintages, and locations are included in the analysis. Specifically, the analysis considers the scaling up of the government's High Efficiency AC (HEAC) program which offers 900 Saudi Riyals (240 USD) per unit to consumers for up to 6 split system units with an energy efficiency rating (EER) of 13.0 or more per household. The main findings of the study suggest that upgrading the existing old stock of window units and split systems currently in place to the requirements of HEAC program would generate a reduction in electricity consumption of around 33 TWh/year and 24 million tons of CO2. Due to the effect of the HEAC consumer subsidy, purchasing a high efficiency unit has a simple payback period for the consumer of 5 years which is faster than less efficient AC options. This would come at a cost to the government of approximately 6 Billion USD resulting in an annual income of 3.0 Billion USD from the sale of avoided fuel associated with the saved electricity consumption.

Fault diagnosis and energy consumption analysis for variable air volume air conditioning system: a case study

Several common faults and their causes in variable air volume (VAV) air conditioning system are presented, and the principle of fault diagnosis of air conditioning system is briefly described. The VAV air conditioning system was modeled in TRNSYS, and five typical faults of the cooling mode were simulated. The comparative analysis of the respective under normal operation and fault operation had been made, and the impact of each fault on the energy consumption was also analyzed. The actual operating characteristics of air conditioning system was then evaluated. Further, some parameters under fault operations were compared with those under the normal operation, from which the changing characteristics of parameters could be discovered, and the characteristics can be used to diagnose faults. The simulation results demonstrate that fault can affect the energy consumption of VAV air conditioning system, and the impact of each fault is different. In addition, monitoring the change of energy consumption and operation parameters is helpful in fault diagnosis, and the effective fault diagnosis has great significance to energy-saving of the air conditioning system.

Characteristic Evaluation on the Cooling Performance of an Electrical Air Conditioning System Using R744 for a Fuel Cell Electric Vehicle

The objective of this study was to investigate the cooling performance characteristics of an electrical air conditioning system using R744 as an alternative of R-134a for a fuel cell electric vehicle. In order to analyze the cooling performance characteristics of the air conditioning system using R744 for a fuel cell electric vehicle, an electrical air conditioning system using R744 was developed and tested under various operating conditions according to both inlet air conditions of the gas cooler and evaporator and compressor speed. The cooling capacity and coefficient of performance (COP) forcooling of the tested air conditioning system were up to 6.4 kW and 2.5, respectively. In addition, the electrical air conditioning system with R744 using an inverter driven compressor showed better performance than the conventional air conditioning system with R-134a under the same operating conditions. The observed cooling performance of the developed electrical air conditioning system was found to be sufficient for cooling loads under various real driving conditions for a fuel cell electric vehicle.

이산화탄소를 적용한 승용자동차 냉방시스템의 성능특성에 관한 연구

본 연구의 목적은 이산화탄소를 적용한 자동차용 냉방시스템의 냉방 성능특성을 고찰하는 것이다. 특히 자동차의 실도로 운전 조건을 모사할 수 있도록 실험 조건을 선정하였으며 실제 자동차에 적용된 이산화탄소용 냉방시스템에 대하여 다양한 냉방성능 실험을 진행하였다. 결과적으로, 가스쿨러 입구 공기온도가 증가할수록 냉방용량과 COP는 감소하였고 증발기 입구 공기온도가 증가할수록 냉방용량과 COP는 증가하였다. 또한, 압축기 회전속도가 900 rev/min에서 1800 rev/min으로 증가할수록 냉방용량은 42.2% 증가였으나 냉방 COP는 55.4% 감소하였다. The objective of this study is to investigate cooling performance characteristics of mobile air conditioning system using R744 as an alternative of R-134a. In order to analyze the cooling performance characteristics of the air conditioning system using R744 for a passenger vehicle, the developed air conditioning system using R744 was applied in a real passenger vehicle and tested under various operating conditions with the variation of gas-cooler inlet air conditions, evaporator inlet air temperatures and compressor speeds. As a result, cooling capacity and coefficient of performance (COP) of the tested air conditioning system decreased with the rise of the inlet air temperature of the gas cooler but increased with the rise of the inlet air temperature of the evaporator. In addition, cooling capacity and coefficient of performance (COP) increased by 42.2 % with the rise of the compressor speed from 900 rev/min to 1800 rev/min, but it decreased by 55.4%.

97/05033 Thermal comfort analysis inside a car: Chakroun, W. and Al-Fahed, S. Int. J. Energy Res., 1997, 21, (4), 327–340

In vehicles, air conditioning tends to offer efficient thermal conditioning and air circulation inside cabin for passenger comfort from different climate variation. The working performance of air conditioning system in vehicles is an essential factor for thermal comfort and driving safety of the passenger compartment of vehicles. Therefore, it is of great significance to construct a numerical simulation model for theoretical analysis and performance evaluation of vehicle air conditioning system. In current research, the air conditioning system of an electric vehicle is taken as the research subject. Internal flow field characteristics of air conditioning system is investigated by Computational Fluid Dynamics (CFD). Results show that the air flow in air-conditioning system is relatively smooth, and the velocity distribution in the front windshield A area and the driver's field of vision of the left and right windows is not ideal when the defrosting-demisting mode is on; the velocity and air quantity distribution of the two outlets in the middle air duct are not uniform under blowing mode. In view of the uneven distribution of velocity and air quantity, the corresponding optimization scheme is proposed. After optimization, the cell relative velocity of the front windshield is significantly improved, and velocity distribution of the side window glass is slightly increased and the defrosting-demisting performance meets the vehicle defrosting requirements of national standard; after optimization, the air quantity distribution of the air ducts at blowing mode is more uniform, which is conducive to the comfort of the passenger compartment.