• Proceedings of the Membrane Society of Korea Conference
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• 1998.10a
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• pp.115-117
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• 1998

생물 발효 공정에 의해 생산된 부탄올 수용액은 농도가 희박하여 농축 공정이 필요하다. 기존의 농축 공정 중 투과증발공정은 공비혼합물이나 비점이 근접한 혼합물등을 분리하는데 에너지가 적게 들고, 분리 효과가 뛰어나며, 조업이 용이하고, 공정이 차지하는 공간이 적다는 장점을 가지고 있다. 산업적으로 관심을 갖는 5 wt% 이하의 부탄올 수용액을 효과적으로 농축시키기 위해 투과증발공정이 사용된다. 현재 투과증발공정에 사용되는 막에는 elastomeric membrane, plasma treated membrane, UV-grafted membrane, polymer blend membrane이 연구 개발되어 사용되고 있는데, 이중 플라즈마 처리방법을 통해 막을 제조 할 경우, 플라즈마 대상 물질의 선택 폭이 넓고, 분리물과 막간의 친화력을 향상 시키기 위해 분리물과 유사한 화학구조를 갖게 할 수 있으며, 형성된 코팅 층이 crosslinking되어 안정성을 갖는 장점이 있다. 따라서 본 연구에서는 플라즈마 처리법을 통해 투과증발막을 제조하고 제조된 막을 부탄올 농축에 사용하여 막의 성능을 조사하였고, 막의 성능과 접촉 각, sorption, heat of mixing간의 상관 관계에 대해 살펴 보았다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.11
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• pp.873-879
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• 2014

In the present study, water vapor is injected at various positions in a Clean Dry Air (CDA) system such as a system inlet duct, compressor inlet, and compressor outlet by humidified air turbines. The application of evaporative cooling reduces the compression work and enhances the Energy Consumption Index (ECI) per unit volume. The main purpose of this study is to investigate the compressor power performance with different inlet air temperatures and humidity conditions. It is found that the actual power consumption and discharge flow are significantly influenced by the inlet air temperature as well as relative humidity. The results obtained during this study are compared both numerically and experimentally and are found to be in very good agreement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.517-522
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• 2013

Small size ice-cream maker has two evaporators having different evaporating temperatures of $4^{\circ}C$ and $-8^{\circ}C$. In such case, ice-cream maker system design becomes complicated because multiple capillary tubes affects one another. In this study, performance analysis was conducted for the soft ice-cream maker having two evaporators operating at different temperatures. The compressor was analyzed using efficiency models, the capillary tube was modeled assuming one-dimensional flow, the condenser and the evaporators were modeld based on UA-LMTD method. The refrigeration cycle simulation program was developed applying the enthalpy, pressure and mass balance on each component. Comparison of the test data with the simulated results for R404A revealed that evaporator temperatures of refrigerator and freezer agreed within $3^{\circ}C$.

• Journal of Energy Engineering
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• v.10 no.3
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• pp.253-265
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• 2001

This paper investigates a PI control problem for the evaporator superheat, i.e., temperature difference between the two-phase region and the exit region of an evaporator, for multi-type air-conditioning/refrigeration system. Mathematical model describing the characteristics of compressor, condenser, evaporator, and electronic expansion valve are first derived. Then, two transfer function from the current input applied to an electronic expansion valve to the wall-temperatures of an evaporator tube at two-phase region and superheated region, respectively, are derived. The stability of the closed loop system with the PI controller designed it analyzed by using Nyquist stability criterion. Simulation results are provided.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.114-121
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• 2013

In order to estimate the efficiency of an evaporative heat exchanger having mini channel, the equations to calculate heat exchanger properties, those are air temperatures and water temperatures etc, are derived from the governing equations based on the Navier-Stokes equation, even though there are several assumptions to make problem simplify. There are three heat transfer zones at the mini channel heat exchanger depending on the water condition. So, there are three governing equations and solutions to calculate the properties. As the results of this study, the equations to calculate a saturation point and a dry point are derived to evaluate an evaporative heat exchanger having micro channel. It is supposed to predict and evaluate the performance of a mini channel heat exchanger with evaporation of liquid.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.5
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• pp.513-522
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• 2013

In the present work, a numerical study of a horizontal falling film evaporator in a multi-effect distillation (MED) plant is performed. Tube bundles in the evaporator are described as porous media, and a volume-averaged method is applied. To calculate the fluid flow and phase change in the evaporator due to heat transfer in the system, FLUENT and user-defined functions (UDF) are used. To observe the performance of the evaporator under different operational conditions, tests are conducted for a steam mass flux ranging from 0.5 to 2.5 $kg/m^2s$ in the horizontal tube, for mass fraction of the noncondensable gas in the tube inlet ranging from 0% to 1%, and for film Reynolds numbers ranging from 100 to 1,000 for the falling film. The evaporation rate increases with the steam mass flux and Reynolds number. In contrast, the evaporation rate decreases by 0.87% with a 1% increase in the mass fraction of the noncondensable gas in the tube.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.1
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• pp.21-28
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• 2017

Indirect evaporative cooling, which utilizes a cooling effect obtained by the evaporation of water, is energy-effective compared to the conventional vapor compression method. It is also eco-friendly, due to the non-usage of CFC refrigerant. In this study, three indirect evaporative cooler samples of the cross flow type(size: $300mm{\times}300mm{\times}300mm$, channel pitch: $5mm{\times}5mm$, $5mm{\times}7mm$, $7mm{\times}7mm$) were made using plastic/paper composites. Tests were conducted to measure indirect evaporative efficiencies and pressure drops. Results showed that the efficiency was the highest for the $5mm{\times}5mm$ sample, owing to the largest surface area. The saved electrical energy was also the greatest for that sample. The pressure drop of the wet channel was larger than that of the dry channel as expected. A theoretical model was proposed, which underestimated both the indirect evaporation efficiency and the pressure drop.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.702-715
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• 1990

This paper describes behaviors of two-phase open channel flow inside the flash chamber of a horizontal Multi-Stage-Flash evaporator numerically along with the experimental observations. Bubble trajectories and the velocity and temperature distributions of the liquid phase were predicted by using the particle-source-in-cell(PSI-Cell) method with the appropriate bubble motion/growth equations. Size and number of bubble nuclei embedded in the incoming liquid(brine) were taken into account as important parameters in addition to the conventional ones such as the velocity, degree of inlet superheat, inlet opening height, and the liquid level. Bubble motions, which are unsteady, appeared to be mostly determined by the buoyancy and the drag forces. The calculations, though a number of simplifying assumptions were made, reasonably simulated the hydrodynamic behaviors of the two-phase horizontal stream observed in the experiments. The simulated temperature distributions also agreed fairly well with the other's measurements. Non-equilibrium allownaces, evaluated from the simulated temperature distributions, were within the range of those obtained from the existing correlations, and reduced with the increases of the number and size of incoming bubble nuclei due to vigorous flashing.

• Journal of Energy Engineering
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• v.9 no.4
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• pp.366-371
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• 2000

본 연구는 동적형 빙축열시스템에 있어서 증발판이 축열조 상부에 설치되어 생성된 얼음을 주기적으로 분리, 이탈시켜 하부에 설치된 축열조에 저장하는 기존의 하베스트형 빙축열시스템과는 반대로 축열조 내에 증발판을 설치하여 수중에서 얼음을 생성시키고 분리시켜 부럭에 의해 얼음을 띄워 저장하는 새로운 방식의 수중 하베스트형 빙축열시스템 개발에 관한 연구이다. 본 방식은 축열조 내에 증발판이 설치되어 제빙과 탈빙이 이루어짐으로서 기존 시스템에 설치되는 순환펌프나 순환수 분배기 및 배관 등의 설비가 불필요하고, 또한 조내 물과 증발판이 직접접촉에 의해 열교환이 이루어지므로 기존 공기 중에서의 열교환 방식보다 전열효율이 우수한 장점을 가지고 있다. 따라서 본 연구에서는 상기의 수중 빙제조 방식에있어 빙 제조시와 방냉시 축열조의 열특성을 실험적으로 밝혀 시스템 최적화 및 성능 향상에 대한 기초 자료를 제공하고자 하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.2-2
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• 1998

고체 추진제의 연소율(burning rate)은 연소의 동적 기동을 이해할 수 있을 뿐 아니라 추진제의 성능을 판단할 수 있는 중요한 수단이기 때문에 많은 연구가 진행되어 왔다. 특히 AP계의 고체추진제 표면에서는 발열반응인 분해반응(decomposition) 이외에도 기체로 증발되는 증발되는(evaporation or sublimation)이 존재한다. 증발반응으로 인하여 연소율은 외부압력의 변화에 대하여 반응하게 되며 실험적으로 $r_{b}$= a $p^n$의 관계를 보여주고 있다. 즉, 연소율(burning rate)은 연소실 압력 P의 n승에 비례하며 여기서 n은 실험적으로 결정되는 지수이다. 그러나 압력지수 n은 일반적으로 온도와 압력의 함수이기 때문에 실험적으로 이 측정하기는 매우 어려운 일이다. 또한 QSHOD 가정을 사용하여 고체 추진제의 연소 응답함을 해석하기 위해서 추진제의 민감계수(sensitivity parameters)에 관한 관계식이 필요하며 이러한 관계식은 추진제의 정상연소율에 관한 관계식으로부터 얻을 수 있다.다.