• 한국산업융합학회 논문집
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• 제26권2_2호
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• pp.255-263
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• 2023

The shell and tube-type heat exchangers have been frequently used in many industrial field because of its simple structure and wide operation conditions and so on. The purpose of this study is to investigate the flow characteristics in single shell of shell and tube-type heat exchanger according to velocity and temperature of hot air released from heat exchanger simulator through numerical analysis. As the results, the temperature was decreased in almost quadratic curve from top to bottom in single shell of the shell and tube-type heat exchanger. Further the changes of pressure and velocity in outlet according to change of inlet temperature were not observed. The cost for operating the shell and tube-type heat exchanger should be compared the supply cost of hot air with that of velocity in order to make a economic decision.

• 교육녹색환경연구
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• 제4권4호
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• pp.1-18
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• 2004

Research has been carried out to study thermal environment in a classroom under three kinds of air diffusion temperature and six kinds of air diffusion direction for ceiling type air conditioner. The velocity and temperature distributions of air in the room calculated by 3-dimensional numerical method(PHOENICS), This present study was also conducted to calculate the Air Diffusion Performance Index(ADPI) for cooling conditions and Predicted Percentage of Dissatisfied(PPD) for heating conditions. This analysis shows that the optimum angle of ceiling type air conditioner's diffusion is $15{\sim}30^{\circ}$ for cooling mode and about $15{\sim}45^{\circ}$ for heating mode in these calculating conditions. And also analysis has been carried out to evaluate thermal comfort of vertical and horizontal cross section of classroom.

• 제어로봇시스템학회논문지
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• 제13권4호
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• pp.344-351
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• 2007

In this paper, we propose an approach to design multi-fuzzy controllers for the superheat and the low pressure that have an influence on energy efficiency and stabilization of air conditioning system with multi-evaporators. Air conditioning system with multi-evaporators is composed of compressor, condenser, several evaporators and several expansion valves. It is quite difficult to control the air conditioning system because the change of the refrigerant condition give an impact on the overall air conditioning system. In order to solve the drawback, we design multi-fuzzy controllers which control simultaneously both three expansion valve and one compressor for the superheat and the low pressure of air conditioning system. The proposed multi fuzzy controllers are given as a kinds of controller types such as a simplified fuzzy inference type. Here the scaling factors of each fuzzy controller are efficiently adjusted by Hierarchical Fair Competition-based Genetic Algorithms. The values of performance index of the simulation results of the A company type compare with simulation results of simplified inference type.

• 한국유체기계학회 논문집
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• 제6권3호
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• pp.44-50
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• 2003

An experiment is conducted for measuring the performance of an air tool, which is operated at 100,000 RPM in an unloaded state with very low torque. A 551 kPa in gauge pressure is supply to the inlet of an air tool. An experimental apparatus is developed as a friction type dynamometer. Inlet total pressure, air flow rate, rotational speed and operating force are measured simultaneously. Torque, output power and specific output power are obtained with different rotational speeds. Those are compared with the experimental results which were obtained by a commercial dynamometer. However, no commercial dynamometers are available for measuring the torque above 30,000 RPM. In order to reduce the rotational speed, a reduction gear is applied between the air tool and the commercial dynamometer. Torque and power obtained by the commercial dynamometer show $55\%$ lower than those obtained by the developed friction type dynamometer, because the mass is added to the rotor of air tool for the braking system of the commercial dynamometer and power loss is generated by the reduction gear. From the compared results, the friction type dynamometer should be applied for measuring the performance of the air tool operating at low torque and high RPM.

• 설비공학논문집
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• 제17권1호
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• pp.56-61
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• 2005

Indoor air quality becomes of a concern recently in view of human health. This study investigates the air diffusion performance and the air change efficiency of a classroom, when outdoor air is introduced in addition to the heating/cooling operation of a ceiling-mounted heat pump. A CFD analysis has been performed to investigate the effect of the discharge angle of the air jets from the heat pump for both parallel and series types of outdoor air system. It is observed that the series type creates more uniform indoor environment compared to the parallel type in general. It can be concluded the discharge angle should not be larger than 40o for the parallel type, in order not to generate thermal stratification in the room.

• 한국태양에너지학회 논문집
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• 제38권2호
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• pp.33-43
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• 2018

PV/Thermal module is the combined system, which consist of a photovoltaic module and solar thermal collector that can obtain electrical power and thermal energy simultaneously. Thus the power generation can be increase by decreasing the temperature of photovoltaic module and thermal energy retrieved from module also can be used for heating system. In this study, Heat transfer performance of air type PV/Thermal module was confirmed with various bottom obstacles that can be installed easily to real photovoltaic module by CFD (computational fluid dynamics) analysis. Eight type obstacles were investigated according to the shape and arrangement. As a result, nusselt number represent heat transfer performance was increased about 86% compare with the basic type PV/Tthermal module that has no obstacle and triangle type obstacle had higher value than other types. But pressure drop was also increased with increment of heat transfer enhancement. Thus the performance factor considering both heat transfer and pressure drop was confirmed and V-fin type obstacle arranged in a row for Reynolds number below 9,600 and protrusion type obstacle arranged in zigzag for Reynolds number above 14,400 were shown higher performance factor than other types. From these results, V-fin type obstacle arranged in row and protrusion type obstacle arranged in zigzag were considered as a proper type for applying to real PV/thermal module according to operating condition. But the heat transfer performance can be changed by the geometric conditions of obstacle such as height, width, length and arrangement. Thus, it could also confirmed that the optimal condition and arrangement of this obstacle need to be found in further study.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.604-608
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• 2004

Experimental study was conducted to increase the oxygen transfer efficiency of air diffusers in clean water. By measuring the bubble size from the bubbly two-phase flow visualization with several air diffusers the size of air bubbles near the top surface of aeration tank seems to be independent on the diffuser types. Considering design parameters for the better breakup of larger bubbles around the air diffusers, advanced conceptual air diffusers using nozzle-type throat showing the higher oxygen transfer efficiencies were made.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.1037-1042
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• 1990

The air-fuel ratio of an internal combustion engine must be controlled with accuracy for the improvements of exhaust emission and fuel consumption. Therefore, it is necessary to measure the exact instantaneous amounts of fuel and suction air, so we carried out the experiments for measuring the air flow velocity in a suction pipe of an internal combustion engine using three types of instantaneous air flowmeter. The results obtained can be summarized as follows: (1) The laminar-flow type flowmeter is able to measure both the average and the instantaneous flow rate, but it is necessary to rectify the pulsating air flow in the suction pipe. (2) The a spark-discharge type flow velocity meter is able to measure the instantaneous air velocity, but it is necessary to choose the suitable electrode form and the spark character. (3) The tandem-type hot-wire flow velocity meter indicates the instantaneous flow velocity and its flow direction.

• Journal of Advanced Marine Engineering and Technology
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• 제28권5호
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• pp.773-781
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• 2004

This research was Performed to raise grade efficiency of Sturtevant type air classifier. to treat powder less than $74\mu\textrm{m}$ particle produced at the crushing process of the dry aggregates manufacturing system or concrete wastes recycling system. The experimental conditions were in the ranges. 0.85 to 5.15 $m^3$/s of primary air flow rate. 0.005 to 0.015 $m^3$/s of secondary air flow rate $30^{\circ}$ to $70^{\circ}$ of auxiliary blades angle. respectively. for 1.7~3.3 kg/min of the powder feed rate. It was found that the grade efficiency of the air classifier was increased as the baffle plate was attached at the expansion region. and the optimal operating conditions of the air flow rates and the blade angle were obtained. The fractional recovery curves from the experiments were well agreement with the theoretical one of Molerus model.

• 한국자동차공학회논문집
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• 제13권2호
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• pp.114-117
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• 2005

Air cleaners in all of the automotive engines have been used for decades. In the early 1920's the oil bath type was the popular shape of air cleaners. The air cleaners of the oil wetted bath type were introduced in 1940's. The shape of the dry pleated paper type media was introduced in the 1950's. This trend still continues with new and innovative media being introduced. Engine air cleaners should have effectively removed and reduced harmful contaminants being ingested into engines. This studies show that both, the ingested contaminant size and concentration need to be controlled. This paper com pare and analyze the characteristics over the economics, engine performances and reduction of noises of power-plus air filters with wet paper which were sticked to heavy duty diesel engine.