• 설비공학논문집
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• 제12권3호
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• pp.235-243
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• 2000

A theoretical model for laminar filmwise condensation along an isothermal vertical wall at constant pressure has been formulated on the basis of conservation laws and other fundamental physical principles. The model was applied to the prediction of the influences of variable thermophysical properties of liquid and vapor layers in the filmwise condensation of superheated vapor of Rl2, R134a, R142b and R152a. The dimensionless velocity component method was employed in the transformation of the governing equations and their boundary conditions, and the polynomial method was used for treating variable thermophysical properties of liquid and vapor. Physical quantities, such as the dimensionless thickness of the liquid layer, local heat transfer rate and mean heat transfer coefficient, were investigated for different values of the superheated temperature of the stagnant vapor far from the wall. It was found that the value of mean heat transfer coefficient of R134a was higher than other refrigerants for the change of the superheated temperature.

• 센서학회지
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• 제32권1호
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• pp.39-43
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• 2023

Microscale thermophysical property measurements of liquids have been developed considering the increasing interest in the thermal management of cooling systems and energy storage/transportation systems. To accurately predict the heat transfer performance, information on the thermal conductivity, heat capacity, and density is required. However, a simultaneous analysis of the thermophysical properties of small-volume liquids has rarely been considered. Recently, we proposed a new methodology to simultaneously analyze the aforementioned three intrinsic properties using heater-integrated fluidic resonators (HFRs) in an atmospheric pressure environment comprising a microchannel, resistive heater/thermometer, and mechanical resonator. Typically, the thermal conductivity and volumetric heat capacity are measured based on a temperature response resulting from heating using a resistive thermometer, and the specific heat capacity can be obtained from the volumetric heat capacity by using a resonance densitometer. In this study, we analyze methods to improve the thermophysical property measurement performance using HFRs, focusing on the effect of the ambience around the sensor. The analytical method is validated using a numerical analysis, whose results agree well with preliminary experimental results. In a vacuum environment, the thermal conductivity measurement performance is enhanced, except for the thermal conductivity range of most gases, and the sensitivity of the specific heat capacity measurement is enhanced owing to an increase in the time constant.

• 대한기계학회논문집B
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• 제22권5호
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• pp.596-606
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• 1998

Thermophysical properties and the compressive strength of concrete used in nuclear power plants in Korea were measured. The chemical composition of the concrete was also analyzed. The measured thermophysical properties include the density, the thermal conductivity, the thermal diffusivity and the specific heat for a wide temperature range of 20.deg. C to 1100.deg. C. The chemical composition of Korean concrete is similar to that of US basaltic concrete and the thermophysical properties are strongly temperature dependent. The density, the conductivity and the diffusivity decrease with an increase in temperature, and particularly the conductivity and the diffusivity are a 50-perdent decrease at 900.deg. C as compared with these values at room temperature. The specific heat increases until 500.deg. C, decreases from 700.deg. C to 900 .deg. C, and then increases again when temperature is above 900.deg. C. The measurement beyond 1100.deg. C is not acceptably accurate because the concrete decomposes to a liquid phase from a solid phase at that temperature. The results of this study can be applied, for example, to an analysis of the molten core-concrete interaction (MCCI) phenomenon of concrete structures at high temperature will also require those property data, especially for high temperature ranges.

• 한국추진공학회지
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• 제14권3호
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• pp.39-51
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• 2010

실제 기체 상태 방정식에 대한 이론적 원리가 조사되었으며 초임계 조건을 포함한 다양한 압력과 온도 조건에서 액체 로켓 엔진의 추진제로서 사용되는 산소, 수소, 메탄의 열역학적 상태량에 대하여 비교 연구되었다. 또한 이상 기체 상태 방정식을 적용하였을 경우와 실제 기체 상태 방정식(SRK 상태 방정식과 PR 상태 방정식 및 ECS 원리)을 적용하였을 경우의 열역학적 상태량에 대한 비교 연구가 수행되었다. 단일 성분이 액상인 영역에서의 열역학적 상태량 차이가 관찰되었으며 오차 범위에 대한 결과가 고찰되었다.

• 설비공학논문집
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• 제25권5호
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• pp.233-239
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• 2013

The Thermophysical properties of thermal conductivity, viscosity, and heat capacity for $CO_2$ slurry ($CO_2$ gas and $CO_2$-hydrate mixture) having a high gas phase volume fraction were predicted using the conventional mixture models and the TRAPP model under hydrate formation conditions. Based on the calculated thermophysical properties, the heat transfer coefficient and pressure drop of the $CO_2$ slurry in the tube were predicted. The thermal conductivity of $CO_2$ slurry ranged from 0.02 to 0.2 W/m-K, and the mixture viscosity was larger than that of pure $CO_2$ by 1.9~2.7 times. The heat capacity of $CO_2$ slurry ranged from 63 to 68% of that for pure $CO_2$. The predicted heat transfer coefficient of $CO_2$ slurry was 6 times higher than that of pure $CO_2$. In the separate model, the estimated pressure drop increased with an increase of $CO_2$-hydrate mole fraction, and was 60% of that of pure $CO_2$.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.762-769
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• 2024

The TMSR-SF0 simulator is an integral effect thermal-hydraulic experimental system for the development of thorium molten salt reactor (TMSR) program in China. The simulator has two heat transport loops with liquid FLiNaK. In literature, the 95% level confidence uncertainties of the thermophysical properties of FLiNaK are recommended, and the uncertainties of density, heat capacity, thermal conductivity and viscosity are ±2%, ±10, ±10% and ±10% respectively. In order to investigate the effects of thermophysical properties uncertainties on the molten salt heat transport system, the uncertainty and sensitivity analysis of the heat transfer characteristics of the simulator system are carried out on a RELAP5 model. The uncertainties of thermophysical properties are incorporated in simulation model and the Monte Carlo sampling method is used to propagate the input uncertainties through the model. The simulation results indicate that the uncertainty propagated to core outlet temperature is about ±10 ℃ with a confidence level of 95% in a steady-state operation condition. The result should be noted in the design, operation and code validation of molten salt reactor. In addition, more experimental data is necessary for quantifying the uncertainty of thermophysical properties of molten salts.

• 한국항공우주학회지
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• 제38권8호
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• pp.823-833
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• 2010

액체 로켓 및 항공용 엔진 연료로서 사용되는 케로신의 열역학적 상태량을 연구하기 위해 surrogate 모델이 조사되었다. 초임계 조건에서 실제 기체 상태 방정식(SRK 상태 방정식, PR 상태 방정식)과 NIST SUPERTRAPP(ECS 원리)을 이용하였을 경우의 밀도 분포가 기존의 실험 결과와 비교되었다. 또한 surrogate 모델의 종류에 따른 열역학적 상태량의 오차 범위에 대한 고찰이 수행되었다. 탄화 수소 계열 연료에 대해서는 PR 상태 방정식과 ECS 원리가 높은 정확도를 나타내지만 압력, 온도와 같은 작동 환경에 따라 적절한 surrogate 모델을 선별하여 선택해야 함을 확인하였다.

• 한국추진공학회지
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• 제17권6호
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• pp.48-58
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• 2013

4개 화학종의 케로신 대체 모델과 다양한 상태 방정식을 이용하여 초임계 압력 조건의 스월 인젝터에서의 열역학 상태량 및 유동 특성을 연구하였다. 상태방정식에 따른 열역학 물성치의 정량적인 비교와 함께 large eddy simulation 및 예조건화 기법을 적용하여 스월 인젝터에서의 유동 특성 해석이 수행되었다. 초임계 스월 인젝터 내에서 열역학 물성치를 비교 조사하였고 상태량 예측 정확도가 인젝터에서의 유동 특성에 상당한 영향을 미치는 것이 관찰되었다. Redlich-Kwong-Peng-Robinson 상태 방정식이 넒은 온도 영역에서 가장 적절한 결과를 제시하였다.

• 오토저널
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• 제13권2호
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• pp.88-102
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• 1991

In this study, thermophysical properties of the ceramic dielectrics such as BaOTiO$_{2}$, SrOTiO$_{2}$, MgOTiO$_{2}$, were measured by a single rectangular pulse heating method. The values of thermal diffusivities, specific heats, and thermal conductivities were measured as a function of temperature range from room temperature to 1300k. The measured thermal properties of one group of ceramic material were compared with those of other group and discussed in detail in connection with the chemical composition. Thus, some criteria for thermal design with the electric-electronic ceramic material were proposed.

• 대한기계학회논문집A
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• 제20권1호
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• pp.172-179
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• 1996

For mechanical systems operating at high tempertature, thermal fatigue phenomenon has been recognized as a major cause of mechanical component failures. To evaluate cumulative fatigue damage as a conesquence of thermal fatugue on real time, the stress tranfer function(Green's function) approach is popularly used. The objective of this paper is to investigate the effect of thermophsical properties on the stress tranfer function. For this purpose a modified Green's function approach considering temperature-dependent thermophysical properties is proposed. Two case studies were performed and the proposed approach agrees well with full finite element analysis.