• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.92-97
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• 2011

Nowdays the most critical problem is global warming and the most important reason is the high emition of carbondioxide. 23% of the use of carbondioxide is used in building and decreasing the use of it is very important. One of the biggest factor that can decrease the use of energy is developing the heat conducting ratio of the materials we use in building. Heat conducting ratio is the important factor in the use of reducing energy comsumation. In this research, there are methods about how to measure the heat conducting ratio, and the existing the representing measuring method which is Heat Flow Meter HFM 436, Laser Flash Analysis and find out about the TCi of the new method C-Therm and compare the results.

• 분석과학
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• 제19권4호
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• pp.323-332
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• 2006

This paper discusses several low-temperature heat-tranfer fluids, including water-based inorganic salt, organic salt, alcohol/glycol mixtures, silicones, and halogenated hydrocarbons in order to choose the best heat-transfer fluid for the newly designed direct contact refrigeration system. So, it contains a survey on commercial products such as propylene glycol and potassium formate as newly used in super market and food processing refrigeration. The stability of commercial fluids at the working temperature of $-20^{\circ}C$ was monitored as a function of time up to two months. And organic and inorganic compositions of candidate fluids were obtained by analytical instruments such as ES, XRF, AAS, ICP-AES, GC, and GC-MS. Analysis results indicate that commercial propylene glycol is very efficient and safe heat transfer fluids for the direct cooling system with liquid phase.

• 설비공학논문집
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• 제29권11호
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• pp.570-579
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• 2017

In this study, we examined the multi-stage piston-type air compressors typically used in a railroad vehicle, and the heat transfer efficiency was analyzed according to the design conditions of the heat exchanger (a compressor component module for cooling the compressed high temperature air). For the fin-tube heat exchanger used in the most air compressors, numerical analysis was performed to analyze heat transfer by defining the various rectangle tube sizes and the number of fin-per-unit area as design variables under the same flow rate of compressed air. Also, this analysis compared the temperature of the compressed air. Regarding environmental conditions for analysis, the flow rate of the external cooling air was measured and the mean value of the values was applied. And a "turbulence model" was considered in both the external flow of the cooling air and the internal flow inside the tube. From the results of analysis, it was found that the change of the aspect ratio value of the tube greatly influences the heat transfer efficiency of the compressed air, and influences if the fin density is relatively small. As a result, the optimum design specifications of the heat exchanger for air compressors were confirmed based on the analysis of the heat transfer efficiency, according to the design conditions of fin and tube by the operating temperature range of the compressed air.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 춘계 학술대회논문집
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• pp.176-180
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• 2001

For windshield defrosting, flow analysis of inner room(vehicle) and heat conduction on the windshield surface are undertaken. Simulation for defrosting enthalpy method is usedand verification of heat and fluid flow analysis for room is done in cavity flow. The defrosting process is three dimensional phenomena and phase is changing. The result of defrosting analysis are well presenting the phase change and these results offer basic design data for defrosting phenomena.

• 에너지공학
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• 제26권1호
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• pp.9-22
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• 2017

A combined thermal and flow analysis was carried out to study the behavior and performance of a small, commercial LTD (Low-Temperature-Differential) heat engine. Laminar-flow solutions for annulus and channel flows were employed to estimate the viscous drags on the piston and the displacer and the pressure difference across the displacer. Temperature correction factors were introduced to account for the departure from the ideal heat transfer processes. The analysis results indicate that the work required to overcome the viscous drags on engine moving parts and to move the displacer is much smaller than the moving-boundary work produced by the power piston for temperature differentials in the neighborhood of $20^{\circ}C$ and engine speeds below 10 RPS. A comparison with experimental data reveals large degradations from the ideal heat transfer processes. Thus, heat-transfer devices inside the displacer cylinder are recommended.

• 설비공학논문집
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• 제12권9호
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• pp.802-809
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• 2000

This study numerically analyzes the thermal and flow characteristics inside the header in PFHE(parallel-flow heat exchanger) by employing a three-dimensional turbulence modeling. The following quantities are examined by varying the injection angle of the working fluid, the location of entrance and the shape of entrance: flow nonuniformity, heat transfer rate, and flow distribution in each passage. The result shows that the degree of significance among the parameters affecting the header part is in the order of the injection angle, the shape of entrance, and the location of entrance. The result also indicates that heat transfer rates compared to the reference model are increased by about 152% for the angle of injection of -$20^{\circ}C$, by about 127% for the shape of entrance with right and left long rectangular form, and by about 108% for the location of entrance located at the lowest Position.

• 한국항공운항학회지
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• 제23권3호
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• pp.8-17
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• 2015

In this research, low fidelity air/heat load analysis was conducted for the intake of high speed vehicle. For air/heat load calculations, aerodynamic properties at the surface and the boundary layer edge were estimated using Taylor-Maccoll equation for conical flow, shockwave relation and Prandtl-Meyer expansion equation for internal and external flow. Couette flow assumption and Reynolds analogy were used in order to calculate convective heat transfer coefficient. In order to calculate skin friction coefficient for heat transfer coefficient analysis, Van Driest method II and Reference Enthalpy method were considered. An axis symmetric SCRAMJET model was selected as a reference configuration for verifying the proper implementation of the present method. Comparison of the results using the present method and Computational Fluid Dynamic analysis showed that the present method is valuable for efficiently providing pressure and heat loads for air-intake structure design of the high speed air vehicle.

• 대한기계학회논문집B
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• 제20권2호
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• pp.720-729
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• 1996

An analysis of convective boiling heat transfer for refrigerant mixtures is performed for an annular flow to investigate the degradation of the heat transfer rate. Annular flow is selected in this study because a great portion of the evaporator in the refrigeration and air conditioning system is known to be in the annular flow regime. Mass transfer effect due to composition difference between liquid and vapor is included in this analysis, which is considered to be one of driving forces for the mass transfer at the interface. Due to the concentration gradient at the interface the mass transfer is interfered, so is the evaporative heat transfer at the interface. The mass transfer resistance makes the interface temperature slightly higher and, as a result, the heat transfer coefficients decrease compared with those without mass transfer effects. The degradatioin of the heat transfer rate reaches its maximum at a certain composition. The composition difference between vapor core and vapor at the interface has a direct effect on the temperature difference between the vapor core and the interface and the degradation of the heat transfer rate. Correction factor $C_{F}$ for the mixture effects is added to the correlation for pure substances and the flow boiling heat transfer coefficients can be calculated using the modified equation.n.

• 한국지열·수열에너지학회논문집
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• 제12권4호
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• pp.33-39
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• 2016

A ground source heat pump (GSHP) system is recommended as a heating and cooling system to solve the pending energy problem in the field of air conditioning, because it has the highest efficiency. However, higher initial construction cost works as a barrier to the promotion and dissemination of GSHP system. In this study, numerical analysis on the characteristics of high density polyethylene (HDPE) pipe with spiral inside was executed. The heat transfer and flow characteristics of it were compared with those of a conventional smooth HDPE pipe. The heat transfer coefficient and pressure drop of the spiral HDPE pipe were higher than those of the smooth HDPE pipes at the same fluid flow rate. By decreasing the flow rate, the spiral HDPE pipe represented similar values of heat transfer coefficient and pressure drop to the smooth HDPE pipe. The lower flow rate of the spiral HDPE pipe comparing with it of the smooth HDPE pipe is estimated to reduce the length of the ground loop heat exchanger.

• Advances in Energy Research
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• 제8권3호
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• pp.125-136
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• 2022

Entropy generation along with exergetic analysis is carried out using turbulent nanofluid flow in the heat exchanger. To obtain the optimized percentage constituent of nanofluid, the nanofluid volume concentrations is varied for the given input conditions. For different Reynolds number of the fluid and heat capacity rate ratio between the streams, the heat transfer improvements are studied in terms of nano particles diameter. Parametric analysis is carried out for a counterflow heat exchanger using turbulent nanofluid flow with exergetic efficiency along with entropy generation number as performance parameters. The exergetic efficiency provides realistic approach in the design of nanofluid applications in heat exchanger leading to conservation of energy.