• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.952-961
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• 1989

The purpose of this study is to investigate the behavior of operational and design factors on the performance characteristics of a horizontal fin-tube heat exchanger under phase change conditions for refrigerant. The flow and heat transfer in the heat exchanger are simulated numerically taking into account the variations of heat transfer coefficients, thermodynamic and flow properties of refrigerant, and the axial heat conduction in the tube wall. As the results of this study, it was found that the annular flow model was more reasonable physically than the homogeneous one for the two phase flow of refrigerant and axial heat conduction of tube wall did not have a great influence on the analysis. The effects of refrigerant pressure, mass flow rate of air, diameter of tube and the number of fins per unit length of tube were also discussed.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.1
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• pp.64-71
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• 2012

While a conventional ECS mainly consisted of an air cycle machine and heat exchangers, a new concept of a phase change heat exchanger was added to improve the transient performance of the ECS. As a result, an ECS modeling program including the phase change heat exchanger is newly developed to estimate its effect in various flight conditions such as take-off, maneuver, cruise, and landing. The simulation result regarding a virtual flight profile has confirmed the new ECS fulfilled the requirement by showing the temperature of the cooling air returned from the bay was always kept below $80^{\circ}C$. Through this study, the new ECS concept with PCHE was verified successfully.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.8
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• pp.805-814
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• 2011

Aluminum plate-fin heat exchangers (ALPHEs) are widely used in petroleum and gas-treated processes. The performance of the ALPHE is strongly dependent on the distribution characteristics of the header and the distributors of each fluid. In this paper, we define the aspect ratio in the side-entry type distributor and analyze the distribution characteristics using CFD-based numerical methods. The phenomena of velocity deviation and distribution with the aspect ratio and the inlet Reynolds number were analyzed by applying relative and absolute maldistribution parameters, and an optimum aspect ratio with the inlet Reynolds number was presented.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3164-3169
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• 2013

In this study, a series of CFD analysis was performed in order to predict the leaving water temperature and the slope of in-situ thermal response tests of the vertical-type geothermal heat exchangers. The geothermal heat exchanger and surrounding ground formation were modeled using GAMBIT and simulation was used by utilizing FLUENT which is commercial CFD code. Comparing with the results of CFD and in-situ thermal response tests, the results of CFD was presented good agreement with $0.5^{\circ}C$ difference of Leaving Water Temperature and with 1.6% difference of the Slope.

• Resources Recycling
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• v.9 no.3
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• pp.13-21
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• 2000

This study describes to analyze the heat transfer characteristics of waste solvent recovery system using a double pipe heat exchanger heating solvent by the hot oil. The solvent recovery system consists of the feeding pump, the double pipe heat exchanger, the vacuum spray chamber, and the condenser. A double pipe heat exchanger consists of the first section to conduct the heating of solvent to the thermal saturated point and the second section to evaporate the saturated solvent. The heat transfer area for vaporization of water, benzene and alkylbenzene was predicted by the heat balance modelling and experimentally measured from the temperature distribution as a function of solvent flow rate and heating temperature. The required heat transfer area for vaporization was increased with increasing solvent flow rates and with decreasing heating temperatures due to decreased quantity of transferred heat per the unit area. Theoretical modelling of the heat transfer area for solvents vaporization in the pipe showed good agreement with experimental results. Results showed to be suitable for the waste solvent recovery using a double pipe heat exchanger.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.4
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• pp.447-451
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• 2015

The objective of this study is to predict the structural characteristics of a heat exchanger mounted on an aircraft engine using finite element analysis. The plastic fracture and life of the heat exchanger were estimated by a thermo-mechanical analysis. Tensile tests were conducted under high temperature conditions (700, 800, 900, 1000 K) using five specimens to obtain the mechanical properties of the Inconel 625 tubes. To assess the structural characteristics of the heat exchanger, the full and partial models were applied under the operating conditions given by the thermo-mechanical and inertial load. As a result, the case, tubesheet, flange, and mounting components have a reasonable safety margin to the allowable stress assuming a fatigue strength of Inconel 625 of 10000 cycles under 1000 K.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.6
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• pp.810-820
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• 1985

배기 decoupling chamber룰 갖고 있는 맥동 연소 급수가열기에 대한 수학적인 모델링과 관련된 컴퓨터 시뮬레이션을 하였고, 이 때 계에 대한 맥동 현상과 관련된 열적 및 동적 특성을 고려 였다. 시뮬레이션결과 시동기간에 대한 계의 각 부분에서 일어나는 열전달, 압력 및 온도를 구 였고 또한 해석의 제한성과 개선의 필요성을 논의하였다. 이 연구에서 얻어진 결과는 도관에서 맥동에 의한 대류열전달을 예측하기 위한 모델을 세우는데 활용될 수 있다.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.3
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• pp.59-70
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• 2020

Obtaining external forced convection heat transfer from bubble boiling and validating it with experimental results using cryogenic liquids are suggested to derive total heat transfer coefficient with pool boiling condition in the case of coil type heat exchanger with a bundle of tubes and to overcome the limitation of using the empirical correlation. Experiment is conducted with pool boiling heat transfer of saturate liquid nitrogen with helical coil type heat exchanger using liquid oxygen as hot stream fluid. Experimentally measured heat transfer coefficient is well-agreed with the estimated curve considering nucleate boiling and forced convection induced by bubble rise.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1137-1143
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• 2011

The IHX (intermediate heat exchanger) of a VHTR (very high-temperature reactor) is a core component that transfers the high heat generated by the VHTR at $950^{\circ}C$ to a hydrogen production plant. Korea Atomic Energy Research Institute manufactured a small-scale prototype of a PCHE (printed circuit heat exchanger) that was being considered as a candidate for the IHX. In this study, as a part of high-temperature structural integrity evaluation of the small-scale PCHE prototype, we carried out high-temperature structural analysis modeling and macroscopic thermal and elastic structural analysis for the small-scale PCHE prototype under small-scale gas-loop test conditions. The modeling and analysis were performed as a precedent study prior to the performance test in the small-scale gas loop. The results obtained in this study will be compared with the test results for the small-scale PCHE. Moreover, these results will be used in the design of a medium-scale PCHE prototype.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.179-187
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• 2002

Finite element analysis was performed to evaluate the integrity of the tubes in the fixed tubesheet of horizontal type heat exchanger under operating condition. For the finite element analysis of the heat exchanger, tubes and tubesheets were equivalently modeled with concentroidal hexagonal columns and solid plates having equivalent properties for the convenience of finite element modeling, respectively. Load combination of tube pressure and thermal expansion most likely to precipitate possible failure of the tubes was selected and applied to the finite element analysis. The compressive stresses of the tubes were calculated based on displacements of each tube, which were obtained from anile element analysis. Finally, the maximum tube stress was compared with the design criterion of ASME Boiler and Pressure Vessel Code Section VIII.