Acoustic properties of the porous material in a car cabin model

This paper predicts the acoustic properties of the porous material in a car cabin model by using an appropriate experimental method, and it verifies the estimated acoustic properties by conducting the FEM (Finite Element Method) analysis. A simplified vibro-acoustic system imitating a car cabin is set up. The car cabin is made of six rigid walls, and a flexible panel is mounted on the front firewall position. The porous material is applied to the inner surface of the panel and modifies the coupling between the panel and the cabin air cavity. The panel is mechanically excited by using an electromagnetic shaker, which is imitating the structure-borne noise. The radiated noise is recorded by using pressure microphones at the different locations inside the car cabin. Based on the model proposed, the effect of the porous material on the acoustic properties is investigated by using the Sound Pressure Level (SPL) at the microphone locations. Finally, the experimentally acquired acoustic properties of the porous material are compared with the numerical analysis of FEM. The simulation results show that the proposed model agrees well with the experiment data. The noise propagating inside the car cabin is predicted to be of similar level in both the experimental method and in the numerical analysis

Employing a Modified Diffuser Momentum Model to Simulate Ventilation of the Orion CEV (DRAFT)

Computational Fluid Dynamics (CFD) is used to model the flow field in the Orion CEV cabin. The CFD model employs a momentum model used to account for the effect of supply grilles on the supply flow. The momentum model is modified to account for non-uniform velocity profiles at the approach of the supply grille. The modified momentum model is validated against a detailed vane-resolved model before inclusion into the Orion CEV cabin model. Results for this comparison, as well as that of a single ventilation configuration are presented

Validation of a 5-zone-car-cabin model to predict the energy saving potentials of a battery electric vehicle’s HVAC system

This paper presents a 5-zone-car-cabin model which is able to simulate the car cabin’s thermal condition depending on several influencing parameters. This includes the solar radiation, to which special attention is paid in this paper. In addition, a generic methodology for parameter optimization considering measurements on a reference vehicle is presented. Thus, a very high degree of determination of the model was achieved. This paper is motivated by the impact of auxiliary loads on overall energy consumption in battery electric vehicles. The further use of the model is intended to calculate the energy saving potentials of the heating, ventilation, and air conditioning system by reducing or increasing the target interior temperature. This is necessary for a predictive control of secondary consumers

Federated Object Detection for Quality Inspection in Shared Production

Federated learning (FL) has emerged as a promising approach for training machine learning models on decentralized data without compromising data privacy. In this paper, we propose a FL algorithm for object detection in quality inspection tasks using YOLOv5 as the object detection algorithm and Federated Averaging (FedAvg) as the FL algorithm. We apply this approach to a manufacturing use-case where multiple factories/clients contribute data for training a global object detection model while preserving data privacy on a non-IID dataset. Our experiments demonstrate that our FL approach achieves better generalization performance on the overall clients' test dataset and generates improved bounding boxes around the objects compared to models trained using local clients' datasets. This work showcases the potential of FL for quality inspection tasks in the manufacturing industry and provides valuable insights into the performance and feasibility of utilizing YOLOv5 and FedAvg for federated object detection.Comment: Will submit it to an IEEE conferenc

TRANSIENT PERFORMANCE EVALUATION OF AUTOMOTIVE SECONDARY LOOP SYSTEMS

Automotive air-conditioning is a high impact technology where improvements in energy consumption and environmental performance can make a significant difference in fuel efficiency and comfort. The mandatory phase out of R134a as refrigerant in the European Union has set the stage for new systems and alternative refrigerants. While some of these refrigerants, such as R152a or R290, have a low Global Warming Potential, their flammability requires secondary loop systems to be used. The added thermal mass of such systems may increase power consumption and delay cool down while benefitting thermal comfort during start/stop operation. The recent revival of electric vehicles, as well as the associated focus on air-conditioning energy consumption, provides new challenges and opportunities. This research focuses on the performance evaluation of refrigerants R152a and R290 during transient operation in secondary loop systems, quantification of thermal storage benefits for start/stop operation, and investigation of energy saving potentials in electric vehicles through the use of advanced air-conditioning system controls and cabin preconditioning. A test facility was built to dynamically test secondary loop systems over a wide range of pull down conditions and drive cycles using a passenger cabin model and associated controls. It was shown that R290 is a viable alternative in secondary loop systems and system performance may be on par or better compared to R134a direct expansion systems. The preservation of cooling capacity and thermal comfort during off-cycle periods were quantified for a secondary loop system, as well as a combined ice storage system. System efficiency increases with longer off-cycle periods compared to direct expansion systems. Advanced compressor control strategies and the use of cabin preconditioning can make use of this characteristic and improve energy efficiency by more than 50%. Ice storage may be used in combination with cabin preconditioning to preserve comfort for an extended driving time with reduced use of the vapor compression cycle. A Modelica model of the secondary loop system was developed and validated with experimental data. The model enables dynamic simulation of pull-down and drive cycle scenarios and was used to study the effects of coolant volume and coolant concentration on transient performance

Impact of Front-end Air Flow Conditions on AC Performance and Real-World Fuel Economy

Active grille shutter (AGS) in a vehicle provides aerodynamic benefit at high vehicle speed by closing the front-end grille opening. At the same time, this causes lesser air to flow through the cooling module which includes the condenser. This results in a higher head pressure (AC compressor discharge pressure of the refrigerant). Higher head pressure causes the compressor to work more thereby possibly negating the aerodynamic benefits. This thesis shows a model-based method to quantify the fuel consumption in different scenarios to justify the AGS position (fully open or fully closed) to have better fuel economy. The impact of AGS is more felt at highway speed, so the AGS will be open at low speed or idle. This thesis focuses on the tradeoff between the aerodynamic performance and the compressor power consumption at high vehicle speeds and mid-ambient conditions (26.7°C and 32.2°C). The results from the steady-state simulations show a tiny reduction in the fuel consumption rate for AGS closed condition by comparing to AGS open condition; while the results for the transient cycle show a remarkable reduction in the fuel consumption rate when the vehicle reaches the highest speed of 128.7 km/h. However, at the low-speed range, there is no benefit in fuel economy with AGS closed, as expected

제습제 코팅 열교환기를 적용한 전기자동차용 히트펌프 시스템 성능 분석

학위논문(박사) -- 서울대학교대학원 : 공과대학 기계항공공학부(멀티스케일 기계설계전공), 2021.8. 김민수.In this study, a heat pump system of an electric vehicle (EV) with a novel dehumidifier is suggested and validated by modeling and experiment. The aim of the study is the determination of the energy consumption of the proposed system. The driving range of a conventional EV sharply drops when operating the MHP system for heating or defogging. Because the traditional MHP consumes a lot of energy since it used the condensing method to remove moisture. It means that the air temperature must be lower than dew points to occurs condensation on the metal fins of a heat exchanger, then the air should be reheated to supply into the cabin. In this study, to solve this irrational process for dehumidification, a solid desiccant coated heat exchanger (DCHE) is introduced which is able to heat and mass transfer simultaneously for removing water vapor in the cabin air and recovering waste heat from power electronics and electric machineries (PEEM). To attach the desiccant material onto the metal fin of a heat exchanger, a binder should be necessary. Thus, the proper pair of the desiccant and binder is selected. After analyzing the physical properties of the adsorbent, the optimum binder contents ratio is obtained. Then, the numerical model of the DCHE was developed base on the thermal resistance method to predict the adsorption performance of the DCHE. To validate the predicted results, the DCHE was fabricated and the test facility was also constructed. The simulation results show good agreement with the experimental data. To obtain the power consumption of the MHP, the numerical model of the MHP was developed. The compressor characteristics were determined by preliminary test since it is a crucial component of the MHP and it strongly affects the performance of the MHP system. Similar to the DCHE model, heat exchangers of the MHP also modeled using the thermal resistance method by discrete as small segments. To validate the developed MHP model, the experimental apparatus was constructed and conducted experiments. As a result, the simulation results reveal small differences as compared with the experimental data. Owing to determine the effect of the DCHE on the energy consumption of the MHP to satisfy the cabin target condition, the simulation was conducted by integrated the developed numerical model in the Simulink program. Simulation results reveal that the system with DCHE achieves a reduction in energy consumption as compared to the traditional system. Because the DCHE led to decreasing the operation time of the MHP by adsorption the water vapor in the cabin air, and by heating to approach the cabin air temperature to the setpoint. In conclusion, the novel configuration which is utilized the DCHE in the automobile heat pump system is suggested in this study. And the DCHE effects on the energy reduction of the automobile heat pump system were investigated. Conclusively, the DCHE helps to reduce energy consumption.차량 탑승객의 열쾌적성과 운전 안전성 확보를 위하여, 냉난방 공조 시스템을 가동하여 차량실내 냉난방 및 김서림 제거한다. 이러한 공조시스템을 운전하기 위한 에너지 소비는 불가피하다. 기존 내연기관 차량의 경우, 충분한 연소열량을 활용하여 난방 및 김서림 방지를 위해 사용할 수 있었다. 하지만 전기자동차의 경우, 내연기관 차량과 달리 충분한 열원이 존재하지 않을뿐더러 탑재된 배터리에 저장된 에너지량에 따라 주행거리가 의존적이므로, 공조시스템을 운전할수록 전기자동차의 주행거리가 급감하는 문제가 존재한다. 이를 해결하기 위해서는 공조시스템의 에너지 사용량을 줄이고 효율을 높여야 한다. 기존 차량에서는 김서림 제거를 위하여, 실내공기를 이슬점보다 낮게 만들어 공기내 수분이 열교환기에 응축시켜 제습한 후 재가열하여 실내로 공급하는 방법을 보편적으로 사용하고 있다. 이는 불합리적인 에너지 소비를 야기한다. 이러한 문제를 해결하기 위해, 고체 제습제를 활용하여 공기내 수분을 직접 흡착시켜 제습하는 방안을 고안하였다. 또한, 모터 및 인버터와 같은 전장품들의 폐열을 회수하여 공조에 활용하기 위해 추가 열교환기를 고려하였다. 본 연구에서, 제습제 코팅 열교환기 (DCHE, Desiccant coated heat exchanger)를 제안하고, 해당 열교환기를 적용한 전기자동차용 히트펌프 시스템의 에너지 사용량에 대한 분석을 실시하였다. 이를 위하여, 차량실내 열적 모델, 제습제 코팅 열교환기 모델, 그리고 차량용 히트펌프 모델을 구축 및 검증하였다. 탑승자의 호흡 및 피부에서 증발하는 수분량을 계산하여 차량실내 열적 모델을 구축하고, 다른 연구진의 모델과 비교 검증하였다. 제습제 코팅 열교환기의 해석 모델을 열 및 물질 저항 모델을 활용하여 차분화하여 구축하였다. 이 해석 모델을 검증하기 위하여, 다양한 조건에서 DCHE의 흡착 성능측정을 실험하여 그 결과를 예측 성능과 비교하였다. 제습제 코팅 열교환기는 흡착제와 접착제의 비율에 따른 흡착성능을 분석한 결과를 바탕으로 제작하였다. 차량용 히트펌프 실험장비를 구축하고 다양한 조건에서 실험하였으며, 그 결과를 차량용 히트펌프 해석 모델의 예측 성능값과 비교하여 검증하였다. 따라서, 개발 및 검증된 모델을 Simulink에 활용하여 다양한 운전조건에 대한 시스템의 소비동력에 미치는 영향을 분석하였다. 그 결과, 기존 전기자동차에 비하여 제습제 코팅 열교환기를 적용할 경우, 차량용 히트펌프의 냉매압축기 소비동력이 줄어든다는 결론을 얻었다. 본 연구에서 제시한 제습제 코팅 열교환기를 전기자동차에 적용한다면, 전기자동차용 공조시스템이 사용하는 에너지를 줄임으로써, 겨울철 차량의 주행거리를 확보할 수 있을 뿐만 아니라 미래 전기자동차의 보급 및 확산에도 기여할 수 있을 것으로 기대한다.Chapter 1. Introduction 1 1.1. The motivation of the study 1 1.2. Literature survey 11 1.2.1. Desiccant coated heat exchanger 11 1.3. Objectives and scopes 16 Chapter 2. Electric vehicle thermal loads analysis 19 2.1. Introduction of the cabin model 19 2.2. Numerical model of the cabin thermal load 20 2.3. Numerical model of the wet air 27 2.4. Validation of the cabin model 32 2.5. Sensitivity analysis of the cabin model 36 2.5.1. Ambient temperature and the number of passengers 38 2.5.2. Vehicle velocity profile 40 2.6. Summary 44 Chapter 3. Design and performance analysis of the desiccant coated heat exchanger 45 3.1. Introduction of the DCHE 45 3.1.1. Principle of the adsorption 46 3.1.2. Selection of the solid desiccant and the binder 49 3.2. Physical properties of the adsorbent 55 3.2.1. The surface area of the adsorbent 55 3.2.2. The image analysis using the scanning electron microscope 64 3.2.3. The vapor sorption capacity of the adsorbent 71 3.3. Numerical analysis of the DCHE 78 3.4. Experimental of the DCHE 87 3.4.1. Experiment set-up of the desiccant coated heat exchanger 87 3.4.3. Experimental validation of the DCHE model 96 3.5. Alternate control methods for DCHE 98 3.5.1. Absolute humidity gap method 98 3.5.2. Absolute humidity slope method 99 3.5.3. Water contents ratio method 101 3.5.4. Integrated area ratio method 103 3.6. Summary 105 Chapter 4. Design and performance analysis of the heat pump 107 4.1. Introduction of the automobile heat pump 107 4.1.1. Selection of the refrigerant 107 4.1.2. Selection of the lubricant 115 4.2. Numerical analysis of the automobile heat pump 117 4.2.1. Calculation method and assumption 117 4.2.2. Compressor 119 4.2.3. Heat exchangers 120 4.2.4. Expansion device 126 4.3. Experiment of the automobile heat pump 126 4.3.1. Experimental apparatus 127 4.3.2. Data reduction and uncertainty analysis 136 4.3.3. The optimum charge amounts 139 4.3.4. Performance of the heat pump system 143 4.3.5. Validation of the heat pump model 148 4.4. Summary 153 Chapter 5. Integrated System Simulation 155 5.1. Introduction 155 5.2. Simulation conditions 163 5.3. Simulation results 164 5.3.1. Effect of the additional heat exchanger 164 5.3.2. Effect of the DCHE frontal area 168 5.3.3. Effect of the fresh-recirculation air ratio 171 5.3.4. Effect of the ambient temperature 175 5.3.5. Effect of the DCHE inlet coolant temperature 180 5.3.6. Effect of the number of the passenger 184 5.3.7. Effect of the refrigerant type 187 5.3.8. Effect of the number of the DCHE 192 5.4. Summary 196 Chapter 6. Conclusions 199 References 203 국 문 초 록 222박

Air Quality and Airflow Characteristic Studies for Passenger Aircraft Cabins

This chapter summarizes the work done at the Airliner Cabin Environment Research Lab (ACERL) related to air quality, airflow characteristics, and human thermal comfort inside aircraft cabins. The laboratory is part of the Institute for Environmental Research (IER) at Kansas State University. It has a Boing 767 mockup cabin, bleed air simulator, and a Boeing 737 actual aircraft section that were all utilized to conduct experimental studies to understand air quality inside aircraft cabins. The studies summarized in this chapter include particle image velocimetry (PIV) investigations, particle dispersion, computational fluid dynamics (CFD) simulations, tracer gas and smoke visualization studies, and bleed air investigations. The chapter also summarizes other related studies including virus dispersion, air quality monitoring devices, and related developed air quality standards. The scope of this chapter is to summarize the setup and results of each of the above categories. This summary along with the cited references provides results for full size aircraft cabin environments, helps validate data for CFD simulations, and provides comparison data for other similar studies. This helps improve the design of future aircraft cabins and their ventilation systems and recommends changes to maintenance practices done that can improve the health and safety of humans inside these enclosed compartments