• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.121-125
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• 2008

In this study, the characteristics of internal flow and the heat transfer performance of dimpled plate heat exchanger were numerically investigated. For the numerical analysis, conjugate heat transfer method between cold fluid - plate - hot fluid was studied with appropriate boundary conditions. Velocity magnitude, temperature and pressure distribution were obtained from the simulation. Correlations for fanning f-factor and Colburn j-factor were obtained from numerical results and compared to the experimented data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1548-1553
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• 2003

An experimental study of the absorption process of water vapor into a lithium bromide solution was performed. For the purpose of development of high performance absorption chiller/hater utilizing lithium bromide solution as working fluid, it is the most effective to improve the performance of absorber with the largest heat transfer area of the four heat exchangers. The experimental apparatus was composed of a plate type absorber which can increase the heat exchange area per unit volume to investigate more detail characteristics instead of the conventional type, horizontal tube bundle type. The size of plate absorbers were made for $0.4m{\times}0.6m$ and the design object of a refrigeration capacity was lRT. In this experiment, three kind plate absorbers which were flat plate, dimple plate and groove plate were used. The results were less than the design object values, that is, the refrigeration capacity was about $0.3{\sim}0.4RT$ and the overall heat transfer coefficient was $500{\sim}600kcal/m^2h^{\circ}C$ at the standard conditions.

• 한국산학기술학회논문지
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• 제17권1호
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• pp.591-596
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• 2016

굴뚝의 백연을 줄이기 위하여 6종의 전열판을 선정하여 각각에 대한 열유동 특성을 연구하였다. 본 연구에서는 전열판의 열전달 성능(열전달 능력, 압력강하, 난류운동 에너지, 열전달계수 등)을 조사하기 위하여 상용 전산유체역학 프로그램인 ANSYS CFX Ver.14를 활용하여 균일유동 조건에서 수치해석을 수행하였다, 다른 유로구조를 가지는 6종의 전열판에 대한 전산해석으로부터 기본형, 사각형, 삼각형, 파형 열교환기의 열유동 과정이 모사되었다. 균일유동 해석으로부터 6종 열교환기들의 열전달 능력, 압력강하, 난류운동 에너지, 열전달계수들은 다른 경향을 보였으며, 유로 내의 열유동 특성은 주어진 유량, 전열판 형상, 종횡비에 좌우됨을 알 수 있었으며, 동일 파형에서는 종횡비가 낮을수록 열전달 성능이 우수하였다. 본 연구의 결과는 백연저감용 열교환기의 설계 기초자료로 활용될 것이다.

• 설비공학논문집
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• 제10권2호
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• pp.193-201
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• 1998

A heat exchanging system employing the impinging air jet is still widely used In the various fields due to its inherent merits that include the easiness in engineering applications and the high heat and/or mass transfer characteristics. The purpose of this study is to investigate the enhancement of heat transfer and flow characteristics by placing a turbulence promoters in front of heat exchanging surface. In this study, a series of circular rods are placed at the upstream of a flat plate heat exchanger that is located at potential core region(H/W=2) of a two-dimensional impinging air jet. Heat transfer enhancement is achieved by inserting turbulence promoter that results in the flow acceleration and disturbance of boundary layer. The average Nusselt number of the flat plate with the turbulence promoters is found to be around 1.42 times higher than that of the flat plate without the turbulence promoters. Based on the results of flow visualization with a smoke wire, it is confirmed that the heat transfer enhancement is caused by the flow separation and disturbance of boundary layer by inserting the turbulence promoter.

• 한국표면공학회지
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• 제46권6호
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• pp.283-289
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• 2013

The experimental study for the temperature uniformity on the wafer using liquid-vapor phase heat transfer mechanism is performed. For the experiment, the heater plate which is consist of stainless steel container, working fluid and electrical heater is designed, manufactured and tested at the range of 600 to $850^{\circ}C$. The results showed that the phase change type heater plate was much more uniform and stable temperature on the heater plate surface and wafer than the uniform heat flux type heater plate at the atmospheric condition. Also, the results of 300 mm outer diameter of heater plate showed that the same temperature uniformity compared with 230 mm.

• 대한기계학회논문집B
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• 제24권1호
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• pp.60-67
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• 2000

An experimental investigation on transient heat transfer phenomena of impinging diesel-spray on a flat plate in a pressurized chamber is carried out. A diesel spray is injected from a single-hole nozzle and impinges to a heated flat plate in the chamber. A fast-response thermocouple installed in the top surface of the plate measures the transient variation of surface temperature of the plate under various conditions of the chamber pressures. Utilizing the semi-infinite model, the temporal variation of the heat flux on the plate is determined. Effects of various parameters, such as vertical distances between the nozzle and the plate, radial distances from the injection-axis, and the chamber pressures, on the heat flux characteristics of impinging diesel-spray are studied.

• 한국추진공학회지
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• 제3권2호
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• pp.66-74
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• 1999

본 연구에서는 송풍기의 출력이 일정한 상태에서 열전달 계수의 증가를 가져오기 위한 방법으로 다공판을 이용하였다. 이 방법은 다공판에 의한 운동량 감소 등의 몇 가지 단점이 있지만 특정한 조건에서 사용될 때, 정체 유동 영역에서 다공판이 없는 경우보다 최고 2배 이상 열전달 계수가 증가하였다. 본 연구에서는 정확하고 간편한 실험을 위하여 액정을 온도 지시계로 사용하였으며, 액정을 이용하면 열전대 등을 온도 지시계로 이용하는 실험보다 훨씬 간단하고 정확한 실험이 가능하다는 것을 알 수 있었다.

• 한국가시화정보학회지
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• 제17권2호
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• pp.58-66
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• 2019

This study investigated heat transfer and flow characteristics of a sweeping jet issued from a rectangular nozzle with a thin plate. A thin vertical aluminum plate was attached on outlet of fluidic oscillator to increase velocity of central area with Coanda effect and enhance heat transfer performance. From visualization and PIV experiments, sweeping jet with a thin plate has larger velocity distribution in center region than that of the normal sweeping jet while oscillating frequency is similar as the normal one. Thermographic phosphor thermometry method was used to visualize the temperature field and Nu distribution of plate with impinging sweeping jet with thin plate. Four Reynolds numbers and three jet-to-wall distances were selected as parameters. It is found that heat transfer performance in the low jet-to-wall spacing was enhanced as the cooled area was expanded. However, when the jet-to-wall spacing became greater than 8dh, heat transfer performance became similar due to reduced impinging velocity.

• 대한기계학회논문집B
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• 제25권10호
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• pp.1346-1354
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• 2001

The heat transfer characteristics off swirling air jet impinging on a heated flat plate have been investigated experimentally. The main object is to enhance the heat transfer rate by increasing turbulence intensity of impinging jet with a specially designed swirl generator. The mean velocity and turbulent intensity profiles of swirling jet were measured using a hot-wire anemomety. The temperature distribution on the heated flat surface was measured with thermocouples. As a result the swirl effect on the local heat transfer rate on the impinging plate is confined mainly in the small nozzle-to-plate spacings such as L/D<3 at the stagnation region. For small nozzle-to-plate spacings, the local heat transfer in the stagnation region is enhanced from the increased turbulence intensity due to swirl motion, compared with the conventional axisymmetric impinging jet without swirl. For example, the local Nusselt number of swirling jet with swirl number Sw=0.75 and Sw=1 is about 9.7-76% higher than that of conventional impinging jet at the radial location of R/D=0.5. With the increase of the nozzle-to-plate distance, the stagnation heat transfer rate is decreased due to the diminishing axial momentum of the swirling jet. However, the swirling impinging jet for all nozzle-to-plate spacings tested in this study does not enhance the average heat transfer rate.

• 센서학회지
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• 제13권2호
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• pp.139-143
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• 2004

This paper presents a method that the engine oil condition is detected using a natural convection heat transfer in a engine oil. A sensor circuit maintains a constant temperature difference between a heat plate and engine oil for detecting a natural convection heat transfer rate on the constant temperature. The natural convection heat transfer rate is measured by a current through the heat plate of the sensor circuit. The sensor is tested by a fresh oil. 6,000 km and 10,000 km driven oil in the oil temperature range from $20^{\circ}C$ to $100^{\circ}C$. In the experimental result, when the current through the heat plate is altered by variation of a engine oil temperature and flows driven oil more than fresh oil, the sensor could inform a engine oil deterioration to a car driver.