• 한국기계가공학회지
• /
• 제11권2호
• /
• pp.159-164
• /
• 2012

The shell & tube heat exchanger is used throughout various industries because of its inexpensive cost and handiness when it comes to maintenance. However, it has many design elements such as the location and the shape of inlet and outlet, the numbers of tubes and baffles, etc. Also, the flow within the shell and the heat transfer are complex. This paper is performed numerical analysis to evaluate capabilities of difference in temperature and pressure drop, which are the performance of channel heat exchanger, one of different types of shell & tube exchanger. Also, factors that affect the performance of channel heat exchanger were selected through design of experiment along with key factors.

• 열처리공학회지
• /
• 제33권2호
• /
• pp.72-79
• /
• 2020

To improve the mechanical properties of most structural materials for industrial applications, the control of microstructure is essential by heat treatment process or plastic deformation process. Since the mechanical behavior of structural materials is significantly influenced by their microstructure, it is inevitably preceded to understand the relationship between microstructure and strengthening mechanisms of materials which can be easily changed by heat treatment. In this regard, the nanoindentation test is useful technique for analyzing the influence of the localized microstructural change on small-scale mechanical behavior of various structural materials. Here, the interesting studies performed on various heat-treated materials are reviewed with focus on micromechanical properties obtained by nanoindentation, which are reported in the available literature.

• 소성∙가공
• /
• 제19권4호
• /
• pp.210-216
• /
• 2010

The importance and interests for saving of energy and cost in industry has grown up. Therefore, process optimization to reduce the process and energy become one of the most important things. The non-heat treated steel, post-heat-treated is no necessary, has attractive points as structural materials. However, establishment of mechanical properties is necessary to apply non-heat-treated steel to structural parts. In this study, for non-heat-treated steel and pre-heat-treated steel, we have investigated microstructure, hardness, the tensile strength, compressive strength. And the FE analysis technology to predict the hardness value of forged part is developed on micro-alloyed steel forged part.

• 설비공학논문집
• /
• 제13권12호
• /
• pp.1223-1229
• /
• 2001

Though conventional calorimetry methods such as differential scanning calorimetry (DSC) and differential thermal analysis (DTA) are used generally in measuring heat of fusion, T-history method has the advantages of a simple experimental apparatus and no requirements of sampling process, which is particularly useful for measuring thermal properties of inhomogeneous phase change materials (PCMs) in sealed tubes. However, random criteria (a degree of supercooling) used in selecting the range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion. In the present study, it was shown that a 40% discrepancy exists between the original T-history and the present methods when analyzing the same experimental data. As a result, a reasonable modification to the original T-history method is proposed.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제11권1호
• /
• pp.32-39
• /
• 2003

Though conventional calorimetry methods such as differential scanning calorimetry and differential thermal analysis are used generally in measuring heat of fusion, T-history method has advantages of a simple experimental apparatus and no requirements of sampling process, which is particularly useful for measuring thermophyical properties of in-homogeneous phase change materials in sealed tubes. However, the degree of supercooling used in selecting a range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion. In the present study, it was shown that a 40% discrepancy exists between the original T-history and the present methods when analyzing the same experimental data. As a result, a reasonable modification to the original T-history method is proposed.

• Journal of the Korean Wood Science and Technology
• /
• 제51권6호
• /
• pp.447-447
• /
• 2023

This study aimed to convert underutilized moso bamboo into high-value added products such as fences, interior materials, lighting fixtures, and accessories. Green moso bamboo poles with a diameter of approximately 10 cm and a length of approximately 3.7 m were heat treated at 140℃ using a large-scale kiln. The processing time was meticulously adjusted through various stages, including pretreatment (6-8 hours at 60℃), cooking (8-10 hours at 100℃), steaming (26-30 hours at 120℃), heating (4-6 hours at 140℃), and finally, cooling (below 80℃). A meticulously designed heat treatment process has enabled efficient mass production of moso bamboo poles with improved qualities, including minimal splitting, moisture levels below 3%, and a specific gravity of 1.05. The focus of this study was to present the physical and drying properties, such as color, dimensional change, specific gravity, moisture content, and splitting, observed during the heat treatment process.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
• /
• pp.27-30
• /
• 2005

다목적실용위성 2호기의 추진계는 (주)한화에서 많은 부분 국산화에 성공하였다. 그중에서 추력기 열차폐막도 현재 설계, 해석, 가공까지 항우연과 함께 국산화에 성공하였다. 열차폐막의 국산화를 위해 기존의 용접 및 전기주조법을 적용하였는데 이때 전기주조법을 통해 일체형으로 제작할 경우 열차폐막의 내경이 용접으로 제작된 형상보다 작게 된다. 그래서 위성의 발사환경에서 열차폐막 끝단과 추력기 노즐 사이의 간섭에 대한 가능성을 검증하기 위해 항우연에서 구조해석을 수행하였으며 이를 바탕으로 제작을 수행하였다. 본 논문에서는 다목적실용위성 2호에 장착될 추력기 열차폐막의 설계, 해석, 가공의 전 과정을 설명하고자 한다.

• 한국기계가공학회지
• /
• 제16권5호
• /
• pp.150-156
• /
• 2017

This study tests the characteristics of heat radiation by applying the pin-height variables to 30-W LED floodlights. The angle of the heat sink enables us to identify the characteristics of the heat radiation based on the temperature distribution. The results of the study are as follows. When the heat sinks are set towards the ground, the heat transfer decreases in speed only to expands the temperature distribution, which adversely affects the characteristics of heat radiation and expands the temperature distribution of PCB with the LED chip. We verify that the characteristics of heat radiation are adversely affected when the height of the cooling pin decreases and the heat radiation area decreases, which impedes the heat transfer and increases the temperature distribution on the heat sink.

• 한국지열·수열에너지학회논문집
• /
• 제14권4호
• /
• pp.35-42
• /
• 2018

Among the various ground source heat pump systems, vertical-type heat pump systems have been distributed greatly. Most of the vertical-type ground source heat pump systems have been designed based on the Korean Ministry of Knowledge Economy Announcement in Korea. In this study, the design process of the vertical-type ground source heat pump system in the announcement was analyzed, and the effects of the design parameters on the ground loop heat exchanger were investigated. Borehole thermal conductivity was the highest dominant design parameter for ground loop heat exchangers. The borehole thermal conductivity was changed according to the pipe and grout thermal conductivity. For optimal design of the ground heat pump system, it is highly recommended that the design process in the announcement will be revised to adopt the various tubes and grout which have higher thermal conductivity. In addition, the certification standard for heat pump unit should be revised to develop the heat pump with a small flow rate.

• Journal of Advanced Marine Engineering and Technology
• /
• 제35권8호
• /
• pp.1048-1054
• /
• 2011

레이저 표면경화처리는 고밀도 에너지 열원에 의해 레이저 조사부위만 급속 가열한 후 표면의 열이 내부로 전도되어 급속히 자기냉각 됨으로써 표면을 경화시키는 방법이다. 이 표면처리 방법은 열처리에 의한 열변형이 거의 없고, 표면경화처리 이후 다른 공정을 수반하지 않는다. 또한 국부적인 가공이 가능하기 때문에 복잡한 형상을 가지는 금형에는 적합한 표면처리 방법이다. 본 연구에서는 열처리에 적합한 빔 프로파일을 가진 고출력 다이오드 레이저를 이용하여 금형재료용 주철의 표면처리를 실시하였다. 프레스 금형 공정에 따른 금형의 형상이 다르기 때문에 적용부위에 따라 시험편을 평면과 모서리부로 나누어 열처리를 실시하였다. 이때 모서리부의 열처리는 광학헤드를 $10^{\circ}$ 기울인 상태에서 진행하였다. 그 결과, 모서리부의 열처리는 평면부와 비교하여 형상에 따른 열전달 루트가 제한되므로, 입열이 집중되기 쉬워 평면 열처리보다 빠른 이송속도에서 경화가 이루어졌다.