Moo-Yeon Lee

Study on Cooling Performance Characteristics of Air Conditioning System Using R744 for a Passenger Vehicle

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%.

Study on the Performance Characteristics of the Roof Mounted Electrical Air Conditioning System Using Inverter Scroll Compressor

Abstract The objective of this study is to investigate the cooling performance of the roof mounted air-conditioning system using electric driven scroll compressor for zero emission vehicles. This air conditioner with air source was used R-134a as a refrigerant and tested under various operating conditions such as refrigerant charge amount and indoor temperature, and compressor frequencies. Experimental results revealed that at all tested compressor frequencies, heat transfer rate of the evaporator increased and the cooling COP increased with the indoor temperature. In addition, the heat transfer rate of the evaporator was over 25.0kW sufficient for the cooling loads of an electric bus. Key Words : Cooling capacity, COP, Compressor work, Heat pump, R-134a 본 논문은 지식경제부에서 지원하는 산업원천기술개발사업의 일환으로 수행되었음 . * 교신저자 : 이동연(dylee@ynu.ac.kr)접수일 11년 08월 23일 수정일 11년 09월 22일 게재확정일 11년 10월 06일 기호설명 COP : 성능 (coefficient of performance) Hz : 주파수 (frequency) i : 엔탈피, (kJ/kg) . m : 질량유량 (kg/h) Q & : 열전달률, (W)

Thermophysical Characteristics of the Ferrofluid in a Vertical Rectangle

The article aimed to analytically investigate the thermophysical behaviors of a ferrofluid in a vertical rectangle with the variation of intensity of the magnetic field, viscosity of the ferrofluid and boundary conditions. The governing equations of the ferrofluid include the continuity, momentum and energy equations for describing the thermal-fluidic behaviors of the ferrofluid and the Maxwell equation and magnetization equation are also added to consider rotating effect of the nano-sized particles. The flow behavior and heat transfer characteristics of the ferrofluid with the intensity of the magnetic field, viscosities of the ferrofluid and boundary conditions were analyzed through isotherms, velocity profiles and both mean and local Nusselt numbers. As a result, the isotherms of the ferrofluid in the vertical rectangle increased with the increase of the magnetic volume fractions and magnetic field intensities. In addition, the mean Nusselt numbers increased with the increase of magnetite volume fractions at all magnetic field intensities because of the combined effects of both heat conduction by magnetite and the magnetic volume force.

Performance Characteristics of the Electrical Air Conditioning System for the Zero Emission Passenger Vehicle

The objective of this study is to investigate the cooling performances of the electrical air-conditioning system using electric driven scroll compressor for zero emission passenger vehicles. This air conditioner with air source was used R-134a as a refrigerant and installed in a real zero emission passenger vehicle for tests under various driving conditions. The cooling performance of the electrical air conditioner was affected by driving velocities and conditions of the tested vehicle. The condensing rate of the condenser during driving is better than that of the idle condition. The average cool down temperature in the cabin room decreased on average with the increase of the outdoor temperature from to . In addition, the cooling performances were sufficient for cooling loads of the tested passenger car under tested conditions.

Performance Characteristics of the Thermal Management System for Passenger Hydrogen Fuel Cell Vehicle

Abstract The objective of this study is to investigate performance characteristics of the thermal management system for passenger hydrogen fuel cell vehicle under various operating conditions. The thermal management systems comprised of a stack cooling system, an electric device cooling system and an air conditioning system for a passenger room were tested with driving conditions. As a result, in highway driving mode, the cooling performance of the stack cooling system with air conditioning on condition was 28.8 % lower than that of the air conditioning off condition. And cooling load of the electric cooling system in the city driving mode was 65.6% higher than that of the highway driving mode. Key Words : Cooling Performance, Fuel Cell Vehicle, Stack, Thermal Management System 본 논문은 지식경제부에서 지원하는 개발사업의 일환으로 수행되었음. * 교신저자 : Moo-Yeon LeeTel: +82-10-5440-8421 e-mail: mylee@katech.re.kr접수일 11년 12월 28일 수정일 12년 03월 05일 게재확정일 12년 03월 08일 기호설명 ITD : 입구온도차 (Inlet temperature difference,

Study on the Performance Characteristics of the Thermosyphon Used for the Vehicle Operated at Low Temperature Conditions

The objective of this study is to investigate low temperature performance characteristics of the thermosyphon with/without wick. Thermosyphons using water as the working fluid are tested with variations of wick, charge amount of the working fluid, outdoor temperature, and heat load for the evaporator section at a low temperature. As a result, the heat transfer of thermosyphon was optimized at the charge amount of 40% and increased with the rise of the outdoor temperatures.

Numerical study on the thermal performance characteristics of the stack system for FCEV

The objective of this study is to numerically investigate the heat transfer rate for evaluating the thermal performances of the stack thermal system using the commercial software. In order to perform this, the cooling performances of the stack system for fuel cell electric vehicle were tested under both driving road conditions including the general driving road and uphill driving road and operating conditions with and without of the air conditioning system. The heat transfer rate of the stack radiator for the stack system was increased with the increase of the inlet air flow velocity. The heat transfer rate of the stack radiator increased by 105.3% at the coolant flow rate of 20 l/min and 221.3% at the coolant flow rate of 120 l/min with the increase of the air flow velocity from 2 m/s to 10 m/s. 9.45 ℃ of inlet coolant temperature of the stack radiator at the severe driving condition of the slope of 8% and velocity of 50 km/h showed higher 85.3% than 5.1 ℃ of inlet coolant temperature at the general driving condition of the slope of 0% and velocity of 120 km/h. In addition, as the fuel cell electric vehicle with the air conditioning system operation was driving under severe uphill driving condition, the radiator coolant temperature for a stable stack operation could be exceeded over 70 ℃.

Precision-structural Design for Scanning Probe Microscopes

Abstract Nano-measurement systems such as scanning probe microscopes should be protected against external disturbances. For the design of a scanning probe microscope, the external vibrations need to be characterized and the vibrational properties of the structural frame itself should be modeled. Also, the influences of the external vibration on the apparatus need to be known for its utmost precision. In this paper, the combined vibrational-characteristics of the floor and the structural frame are analyzed and experimentally investigated.요 약 주사탐침현미경과 같은 나노 측정 시스템은 외란으로부터 보호를 받아야만 한다 . 주사탐침현미경의 설계를 위해 외부 진동진동의 특성을 파악해야 하고, 구조프레임 자체의 진동 해석 해야 한다. 또한 장치의 최고 정밀도를 파악하기 위하여, 외부진동의 영향을 분석해야 한다. 본 논문에서는 바닥진동과 구조프레임을 동시에, 진동 분석과 실험을 통하여 진동 특성을 조사하였다. Key Words : Structural frame design, Scanning probe microscope, Vibration isolator, Transmissibility This research was supported by Future-based Technology Development Program(Nano Fields) through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology (2010-0019110)