• 한국추진공학회지
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• 제23권2호
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• pp.27-37
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• 2019

쉘-튜브 열교환기가 나로우주센터 추진기관종합시험장(PSTC)에 설치되었으며, 이 열교환기는 극저온의 헬륨을 고온의 열매유와 열교환하여 약 500 K 까지 가열시키는 역할을 한다. 열교환기에서 토출되는 헬륨의 온도가 설계보다 100 K 낮게 나옴에 따라, 성능저하의 원인으로 열매유의 격막효과가 지목되었다. CFD 해석을 통해 격막효과의 유무를 확인하였으며, 격막효과에 의한 열교환기 성능저하는 미미한 것으로 판단되었다. 추가적으로 열교환기의 성능을 증가시키기 위하여 열매유 교체에 따른 열교환기 성능 변화를 알아보았다. 열매유를 사용하는 열교환기의 성능향상을 위해서는 500 K 부근에서 점성이 낮아야 하고, 열전도도가 높아야 한다는 것을 확인할 수 있었다. 추진기관종합시험장에서 운용된 극저온 헬륨과 고온 열매유의 열교환 시스템의 시험 결과를 본 논문에서 확인할 수 있다.

• 설비공학논문집
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• 제21권12호
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• pp.656-662
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• 2009

In this paper, the heat resistance reliability of an axial smoke exhaust fan was investigated. An axial smoke exhaust fan should be capable of operating at $250^{\circ}C$ for 2 hours. The heat resistance reliability was evaluated by the heat resistance reliability test. A B10 life with a 90% confidence level was estimated to be about 48 minute. The failure occurred in the motor due to high temperature. The main failure mechanisms of the motor were melting of bond and insulating paper and burning of insulating materials in the coil. The heat resistance reliability was improved by changing the way to unite the core and the coil and by replacing the insulating paper and the insulating materials of the coil. A B10 life with a 90% confidence level of a modified axial smoke exhaust fan was estimated to be over 120 minute.

• International Journal of Air-Conditioning and Refrigeration
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• 제14권1호
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• pp.14-18
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• 2006

This study was performed to investigate the heat transfer characteristics of the circular fin-tube heat exchanger. This paper contains the experimental data for the seven kinds of fin geometries. The correlation of Stasiulevicius agreed with the experimental data at high Reynolds number, however not well at low Reynolds number. The Nusselt number was well correlated with Graetz number, and showed a transition near Gz=10. An empirical correlation proposed in the present study agreed well with the experimental data.

• International Journal of Air-Conditioning and Refrigeration
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• 제13권3호
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• pp.152-157
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• 2005

This paper reviews the literature on the performance of fin-and-tube heat exchangers under frosting and defrosting conditions. The effects of frosting and defrosting on the following parameters were discussed: frost growth, overall heat transfer coefficient, surface roughness, and surface characteristics on the heat exchanger. Comparisons of the experimental results and empirical correlations that were obtained from open literature were presented. In addition, a review of the defrosting methods was conducted.

• 설비공학논문집
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• 제14권8호
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• pp.676-682
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• 2002

This paper has been made to investigate the thermal performance characteristics for the several types of heat sinks such as extruded heat sink, aluminum foam heat sink, layered heat sink. The various types heat sinks are prepared and tested for natural convection as well as forced convection. The experimental results for natural convection are compared to those for three types of heat sink so that the appropriate heat sink can be designed or chosen according to the heating conditions. The overall heat transfer performances for layered heat sink, extruded heat sink and aluminum foam heat sink are almost comparable to those under natural convection and forced convection. The forced convection of layered heat sink become 1.2 times as high as those of extruded heat sink, and the forced convection of extruded heat sink become 1.2 times as high as those of aluminum foam heat sink. This study shows that bar height, bar distance and number of bar for layered heat sink are important parameters, which have a serious influence on thermal performance for layered heat sinks.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1258-1263
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• 2004

The present study proposes a new structure for a heat spreader which could embody a thin thickness, any shapes and high heat flux per unit area. It is on the structure for the formation of vapor passages and the support of the case of the heat spreader. A screen mesh is used as the one. To verify the validity of the one, the heat spreader of 1.4mm and 1.6mm thickness was made with 14 mesh and 100 mesh number. In this paper, The performance test of heat spreader conducted in order to compare with the heat transfer performance of conventional heat pipe. As the results, The heat spreader has excellent cooling and heat transfer performance.

• 한국압력기기공학회 논문집
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• 제16권1호
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• pp.56-64
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• 2020

The safety related heat exchangers have been evaluated for their performance during the operation of the nuclear power plant. The evaluation program for the safety related heat exchanger was developed in 2010 and used by KHNP based on EPRI TR-10739 algorithms. The spend fuel pool heat exchanger is one of the safety related heat exchanger in the nuclear power plant and also evaluated for their performance. Recently the performance evaluation for the spend fuel pool heat exchanger was not available because of the decreased heat in the spend fuel pool due to the long term overhaul. This paper analyzes the main cause of evaluation failure in the evaluation process and suggests the criteria for the heat exchanger performance evaluation during the long term overhaul.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.224-230
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• 1998

Non-heat-treated type material has been investigated for formability compared to heat-treated material. It is very important in automation of metal forming, since it has difficulties of controlling heat treating system by the computer and has bottle neck problem related with heat treatment. In this paper, we have concerned about mechanical properties of non-heat-treated material after the forging. To compare the characteristics between heat-treated material and non-heat-treated material, tensile, compression and fatigue test has been performed. Considering results of mechanical properites of non-heat-treated material, it can replace heat-treated material. Therefore non-heat-treated material may be applied to cold forging.

• 한국산업융합학회 논문집
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• 제7권4호
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• pp.331-340
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• 2004

This paper presents a feasibility study of a fresh air load reduction system by using an underground double floor space. The fresh air is introduced into the double slab space and passes through the opening bored into the footing beam. The air is cooled by the heat exchange with the inside surface of the double slab space in summer, and heated in winter. This system not only reduces sensible heat load of the fresh air by heat exchange with earth but also reduces latent heat load of the fresh air by ad/de-sorption of underground double slab concrete. In this paper, we used a model for evaluation of fresh air latent heat load reduction by hygroscopic of air to earth exchange system taking into account coupled heat and moisture transfer of underground double floor space. In conclusion it shows the validity of the proposed method for a design tool and the quantitative effect of the system.

• 대한기계학회논문집
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• 제7권4호
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• pp.417-424
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• 1983

This paper presents two methods of obtaining approximate analytic solutions for the temperature distributions and heat flow to two-dimensional transient heat conduction problems in a finite strip with constant thermal properties using the Heat Balance Integral. The methods introduced in this study are as follows; one using the Heat Balance Integral only, and the other successively using the Heat Balance Integral and an exact analytic method. Both methods are applicable to a large number of the two-dimensional unsteady conduction problems in finite regions such as extended surfaces with uniform thickness, but in this paper only solutions for the unsteady problems in a finite strip with boundary condition at the base expressed in terms of step function are provided as an illustration. Results obtained by both methods are compared with those by the exact two-dimensional transient analysis. It is found that both approximate methods generate small time solutions, which can not be obtained easily by any exact analytic method for small values of Fourier numbers. In the case of applying the successive use of the Heat Balance Integral and Laplace transforms, the analysis shows good agreement with the exact solutions for any Fourier number in the range of Biot numbers less than 0.5.