• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.611-617
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• 2008

Nowadays Plate Heat Exchanger (PHE) is widely used in different industries such as chemical, food and pharmaceutical process and refrigeration due to the efficient heat transfer performance, extreme compact design and efficient use of the construction material. In present study, discussed main conception of plate heat exchanger and applied in vacuum. PHE and aimed apply in the fresh water generator which installed in ship to desalinate seawater to fresh water use heat from engines. The experiment is proceeded to investigate the heat transfer between cold and hot fluid stream at different flow rate and supply temperature of hot fluid. Generated fresh water as outcome of the system. PHE is an important part of a condensing or evaporating system. One of common assumptions in basic heat exchanger design theory is that fluid is to be distributed uniformly at the inlet of each fluid side and throughout the core. However, in practice, flow mal-distribution is more common and can significantly reduce the heat exchanger performance. The flow and heat transfer are simulated by the k-$\varepsilon$ standard turbulence model. Moreover, the simulation contacted flow maldistribution in a PHE with 6 channels.

• 설비공학논문집
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• 제12권2호
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• pp.150-160
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• 2000

Turbulent natural convective flow and heat transfer in a square enclosure with horizontal partition are investigated numerically. The enclosure is composed of a lower hot and a upper cold horizontal walls and adiabatic vertical walls. Partitions carried with the upward, downward, and both control plates are attached perpendicularly to the one of the vertical insulated walls, respectively. The low Reynolds number $k-\varepsilon$ model is adopted to calculate the turbulent thermal convection. The governing equations are solved by using the finite element method with Galerkin method. The computations have been carried out by varying the length of partition, the position of control plates, and the Rayleigh number based on the temperature difference between two horizontal walls and the enclosure height for water(Pr=4.95). When the control plates are attached at the edge of partition, the stability of oscillating flow grows wrose with the increase of Rayleigh number and the partition length. The heat transfer rate has been reducer than that of no control plate due to the restraint of control plates with the increase of Rayleigh number.

• 한국태양에너지학회 논문집
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• 제32권6호
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• pp.22-28
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• 2012

The purpose of this study was to show how tomaintain high efficiency and to use reasonably when being applied the cold-heat storage systems to the showcase. An experimental study was performed to manufacture the showcase system in a laboratory. Comparing the result at general operation condition with that of the new condition using ice storage system, this study showed the effects of the refrigerant sub-cooling, and with using inverter. Using ice storage system, the ice making process was operated during midnight being not needed the cooling of the showcase through the continuous running of the condenser unit. And then, the refrigerant was sub-cooled using the stored cold-heat after being discharged from the air cooling condenser during the day time. Through the experiments, the load transfer rate for the showcase using inverter and ice storage was estimated about 30.0%. And showed that the total power consumption of the showcase with inverter could be reduced about 37% than that of the showcase without inverter.

• 한국해양학회지
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• 제7권1호
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• pp.19-23
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• 1972

온난한 해면위를 비교적 한냉한 대기가 통과할 때 공기와 수면 사이의 열교환량을 알기 위하여서는 해면에서의 현열방출량과 증발량을 측정하여야 하나, 이것들을 직접 측정하기란 현상 자체가 미세하고 측정범위가 너무나 광범위 하기 때문에 매우 어려운 점이 많다. 이런 점들을 극복하기 위하여 Jacobs91949, 1951)와 Manabe(1958)는 기온, 풍속, 증기압과 표면해수온도만을 사용하여 열교환량을 추정할 수 있는 실험식을 구하였다. 이 실험식들은 기온과 표면해수온도와의 차가 크면 클수록 열교환량이 증가함을 나타냈다. 겨울철에 우리나라 동해는 cP기단의 영향으로 한파의 내습이 빈번하고 강한 북서풍이 상존하기 때문에 대기와 해면 사이에 열교환이 왕성한 것은 기정사실이며, 이것에 대한 연구는 Matsumoto(1948, 1967), Manabe(1957, 1958), Kondo(1964), Fujita and Honda(1966)등 여러명의 일본 기상학자들이 관심을 갖고 다루어 왔으나, 이들은 한결같이 동해에서의 열수지 보다 물수지에 관심이 많았고, 일본본토의 강설량과 상관관계를 주로 연구하였다. 본 논문에서는 한국과 일본에서 이미 관측된 해양 및 기상자료를 이용하여 혹한을 동반한 1963년 1월과 난동의 1964년 1월, 그리고 평년의 1965년 1월의 열수지를 계산 비교하고, 이에 따른 여름철의 냉수괴의 세력을 비교 검토하여 보았다.

• 설비공학논문집
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• 제7권2호
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• pp.287-297
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• 1995

In this study, the geometry consists of a two-dimensional rectangular enclosure with localized heating from below. The size and the location of the heater on the floor has been varied, and one of the vertical walls remains at a low temperature simulating a cold window. The governing equations for momentum, energy and continuity, which are coupled with turbulent equations have been solved using a finite volume method. A low Reynolds number $k-{\varepsilon}$ model has been incorporated to solve the turbulent kinetic energy and the dissipation rate. The heat transfer characteristics and the thermal environmental characteristics of the room have been obtained for various system parameters in a room with a partially heated floor.

• 설비공학논문집
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• 제18권11호
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• pp.915-922
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• 2006

Considering heat pipe design principles in fabrication and operational performances, water is one of the most recommended working fluids to make mid to low tempera lure heat pipes. But the conventional water heat pipes might encounter the failure in a cold start-up operation when socked at a chilling temperature lower than the freezing point. If they are subjected to a heat supply for start-up at a temperature around $-20^{\circ}C$, the rate of the vapor flow and the corresponding heat transfer from the evaporator to the condenser is so small that the vapor keeps to stick on the surface of the chilling condenser wall, forming an ice layer, resulting in a liquid deficiency in the evaporator. This kind of problems was resolved by Kang et al. in 2004 by adopting a gas loading heat pipe technology to the conventional water heat pipes. This study was conducted to examine a chilling start-up procedure of gas loading heat pipes by investigating the behaviors of heat pipe wall temperatures. And the thermal resistance of the gas loaded heat pipe that depends on the operating temperatures and heat loads was measured and examined. Two water heat pipes were designed and fabricated for the comparison of performances, one conventional and the other loaded with $N_2$ gas. They were put on start-up test at a heat supply of 30 W after having been socked at an initial temperature around $-20^{\circ}C$. It was observed that the gas loaded one had succeeded in chilling start-up operation.

• Journal of Advanced Marine Engineering and Technology
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• 제40권3호
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• pp.152-156
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• 2016

폐수 열원 히트펌프 시스템은 목욕탕, 공장 또는 하천수 등을 히트펌프의 열원으로 사용한다. 증발기는 폐수로부터의 오염을 완화시키기 위하여 휜이 없는 나관식(bare tube) 열교환기가 주로 사용되고 있다. 대부분의 열 저항은 관외를 흐르는 폐수측에 생성되는 파울링에 의한 것이며, 히트펌프의 성능을 급격하게 감소시킨다. 따라서 본 연구에서는 나관식 열교환기 하부에서 버블 유동층을 형성시키고 세정 볼을 사용하여 관 외측의 파울링을 저감시키는 장치를 개발하였다. 실험 조건으로, 냉수온도 $20^{\circ}C$, 폐수 온도 $40^{\circ}C$, 관 내측 유량 100L/h, 수조 내 물의 양 50L, 열교환기 면적 $0.161m^2$ 이다. 실험결과 세정 볼 없이 버블유동층만 형성한 경우에는 버블유동층이 없는 경우에 비해 파울링에 의해 생성된 열 저항이 약 56% 감소되었으며, 세정 볼의 개수 밀도가 8,000(Number of $ball/m^3$) 일 때, 파울링에 의해 생성된 열 저항은 버블유동층 및 세정 볼이 없을 때와 비교하여 약 86% 감소되었다.

• Journal of Biosystems Engineering
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• 제27권6호
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• pp.565-572
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• 2002

In order to control the root-zone temperature of greenhouse crops in the hydroponics at hot and cold season, heat pump system for cooling and heating was built and tested in this work. The system was air-to-water type and vapour compression type. The heating and cooling mode was selected by the four way valve. Capacity of the compressor was 3.75㎾ and heat transfer area of the evaporator and the condenser were 3.05㎡ and 0.6㎡, respectively. According to the performance test, it could supply heat of 42,360 to 64,372kJ/h depending on the water circulation rate of 600 to 1,500ℓ/h, respectively, when indoor air temperature was 10∼20$\^{C}$. COP of heat pump system was 3.0 to 4.0 in the heating mode. But, COP of the cooling mode was 1.3 to 2.1 at indoor temperature of 20∼35$\^{C}$. The feasibility test in the greenhouse the developed heating and cooling system was installed, showed that the heating cost of the developed system was only about 13% of that of the conventional heating system. The heating cost of the developed system was 367won/day(electric consumption 9.7㎾h/day), while that of the conventional system was 2,803won/day(oil consumption 7.7ℓ/day) at the same heating mode.

• 설비공학논문집
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• 제16권4호
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• pp.390-396
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• 2004

A double-inlet pulse tube refrigerator was fabricated as a U-shape with $\Phi$19.0 mm${\times}$125 mm regenerator packed by #200 stainless steel mesh and $\Phi$12.7 mm${\times}$125 mm pulse tube. A pressure sensor was installed at the inlet of the regenerator and a differential pressure sensor was installed across the bypass. Amplitude of the pulsating pressure was independent of the opening of the orifice and the bypass valves. Helium flow through the orifice and the bypass was calculated based on the measured pressure. Energy loss through the orifice and the bypass was evaluated with the measured pressure and the calculated helium flow rate. The energy loss, which is equivalent to the refrigeration capacity at the cold end of the ideal pulse tube refrigerator, was mainly generated through the orifice. It was proportional to the opening of the orifice valve, but the real refrigerator displayed the best performance at the optimized opening of the orifice valve. This optimized performance of the tested pulse tube refrigerator can be explained by additional refrigeration losses. As an example, the shuttle heat transfer loss of the pulse tube was calculated from the measured experimental data.

• 설비공학논문집
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• 제9권3호
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• pp.312-322
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• 1997

The natural convective flow in a two-dimensional square enclosure with horizontal partitions is investigated numerically. The enclosure was composed of the lower hot and the upper cold horizontal walls and the adiabatic vertical walls, and two identical partitions were positioned perpendicularly at the mid-height of the right and left walls, respectively. The governing equations are solved by using the finite element method with Galerkin method. Calculations are made for different partition lengths, partition conductivites, and Rayleigh numbers based on the temperature difference between two horizontal walls and the enclosure height with water(Pr=4.95). An oscillatory motion of the natural convective flow is affected significantly by the variation of the gap width and Rayleigh number. When the gap width is comparatively short, the heat transfer rate is raised with the increase of the thermal conductivity of partitions. However, for sufficiently large gap widths at higher Rayleigh numbers, the average Nusselt numbers of the conductive partitions are smaller than those of the adiabatic partitions.