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ISSN : 1229-3059(Print)
ISSN : 2287-2302(Online)
Journal of the Computational Structural Engineering Institute of Korea
Vol.32 No.1 pp.7-13

DOI : https://doi.org/10.14775/ksmpe.2019.18.2.007

Numerical Analysis on the Thermal and Fluid in Air Conditioning Duct for Marine Offshore

Eun-Ho Lee1,Si-Young Kwak1,2†
1Industrial Technology(Industrial Materials and Smart Manufacturing Engineering), Korea University of Science and Technology(UST), Daejeon, 34113, Korea
2Digital Manufacturing Process Group, Korea Institute of Industrial Technology(KITECH), Siheung, 15014, Korea
Corresponding author: Tel: +82-31-8084-8801; E-mail: vlvwlw@kitech.re.kr
June 15, 2018 July 9, 2018 July 11, 2018

Abstract


This study is about distributions of heat transfer in air conditioning duct used for marine and oil drilling ship. As the convective heat transfer coefficient increased, heat transfer was conducted dynamically to inside as it exited to the outlet of duct. So, it was checked that the amount of heat transfer generated at duct increased as the convective heat transfer coefficient increased. In case the convective heat transfer coefficient was low, the temperature of duct showed the relatively high temperature distribution due to the temperature influence of internal fluid as the heat transfer between the outside and inside of the duct. In case of temperature distribution generated the volume of the duct along the change of the convective heat transfer coefficient, it was found out that the temperature descended as heat transfer was promoted and the convective heat transfer coefficient increased.



해양 구조물용 공조덕트 열유동에 관한 수치해석

이은호1,곽시영1,2†
1과학기술연합대학원대학교 생산기술전공(산업소재 및 스마트제조공학과), 2한국생산기술연구원 디지털제조공정그룹

초록


    1. Introduction

    Among offshore plants, the submersible semi-drilling rig has air ducts for ventilation in columns and pontoons, which correspond to bridges.

    The air duct generally used in submersible semi-drilling rigs is a lightweight, watertight air duct, which is installed as a module inside the column. It has a corrugation part on the surface in the longitudinal direction, which is designed to increase strength and reduce weight.

    As the strength of the lightweight, watertight air duct is increased by the corrugation part, the air duct can be made thinner and the total weight can be reduced, allowing for more efficient air duct use in submersible drilling rigs. Thus, major oil companies in Europe and other regions generally try to reduce the weight of newly constructed drilling rigs.[1-4]

    As shown in Fig. 1, for the air ducts installed in the column of drilling rigs, the duct is produced simply with flat-surface steel plates and the ends are connected by welding. Therefore, this study analyzes the heat and flow inside the air duct through numerical analysis.

    2. Heat Flow Analysis Method

    This study investigated an air duct with a diameter of 550 mm, as shown in Fig. 2. First, the effects of the corrugations inside the duct on the flow field and heat transfer were examined.

    Fig. 3 shows the boundary conditions for the heat flow analysis of the air duct. To ensure flow stability, the inlet and outlet were created by extruding them by five times and seven times the hydraulic radius.

    As shown in the figure, the convective heat transfer coefficient for the outside of the lightweight watertight duct was set as a variable. The ambient temperature in the atmosphere was assumed to be 25℃. In addition, it was assumed that air flowed into the inlet at 1 m/s and passed through the duct at a temperature of 50℃. The air at the outlet was assumed to have the atmospheric pressure.[5-7]

    Fig. 4 shows the control volume for heat flow analysis. The thickness of the duct, which was a solid area, was 3 mm and consisted of five mesh layers.

    Fig. 5 shows the radial inner temperature distribution along the length of the lightweight watertight duct. The temperature was checked with virtual sensors at five points in 250-mm intervals from the duct inlet. The 250-mm point was the middle position between the corrugated tubes.

    3. Results of Heat Flow Analysis

    Fig. 6 shows the temperature distribution inside the duct according to the change in the convective heat transfer coefficient on the external surface of the lightweight watertight duct. As shown in this figure, heat transfer occurred on the duct surface and heat exchange with the outside occurred when the fluid flows through the duct. As a result, the inside of the duct cooled slowly.

    As the convective heat transfer coefficient increased, there was active heat transfer to the inside as the fluid flowed out through the duct outlet.

    Fig. 7 shows the temperature distribution at each point according to the change in convective heat transfer. Here, the zero point of the X-axis indicates the center of the duct. In general, as the fluid passed through the duct, heat transfer to the outside of the duct occurred. Thus, the inside of the duct cooled more when it was closer to the outlet.

    It was observed that as the convective heat transfer coefficient increased, heat transfer accelerated and the heat was transfered deeper into the duct.

    Fig. 8 shows the temperature distribution for the solid duct region. As shown in this figure, when the convective heat transfer coefficient was low, the heat transfer between the outside and inside of the duct slowed and the duct temperature increased due to the effect of the internal fluid temperature. In contrast, as the convective heat transfer coefficient increased, heat transfer was accelerated and the duct surface temperature decreased.

    An examination of the temperature distribution on the inner and outer surfaces of the duct confirmed that the inner surface had a higher temperature distribution because the temperature of the working fluid was high. In contrast, the outer surface had a lower temperature distribution due to the convective heat transfer with the outside.

    Depending on the moving direction of the working fluid inside the duct, when the fluid passed through the outlet, heat transfer accelerated and the temperature distribution decreased.

    Fig. 9 shows the heat transfer in the duct. As the convective heat transfer coefficient increased, the heat transfer in the duct increased. This is because as the convective heat transfer coefficient on the outer surface of the duct increased, the heat transfer with the working fluid flowing inside the duct was accelerated.

    Fig. 10 shows the temperature distribution inside the duct according to the change in the convective heat transfer coefficient. It can be seen that as the convective heat transfer coefficient increased, heat transfer accelerated and the temperature decreased.

    4. Conclusions

    As a result of the heat transfer analysis of the air duct applied to offshore structures, the following conclusions were reached.

    • (1) As the convective heat transfer coefficient increased, the fluid flowed out through the duct outlet and active heat transfer occurred. Therefore, it was observed that the heat transfer in the duct increased as the convective heat transfer coefficient increased.

    • (2) When the convective heat transfer coefficient was low, the heat transfer between the outside and inside of the duct slowed and the duct temperature increased due to the effect of the internal fluid temperature.

    • (3) For the temperature distribution in the duct volume according to the change in the convective heat transfer coefficient, it was observed that as the convective heat transfer coefficient increased, the heat transfer accelerated and the temperature decreased.

    Figure

    KSMPE-18-7_F1.gif
    Air conditioning duct for marine offshore
    KSMPE-18-7_F2.gif
    Analysis model
    KSMPE-18-7_F3.gif
    Control volume shape for CFD analysis
    KSMPE-18-7_F4.gif
    Control volume for fluid and solid
    KSMPE-18-7_F5.gif
    Sensing positions at length and radial direction
    KSMPE-18-7_F6.gif
    Result of temperature distributions in Fluid region
    KSMPE-18-7_F7.gif
    Comparison of temperature distributions at positions
    KSMPE-18-7_F8.gif
    Result of temperature distributions at solid region
    KSMPE-18-7_F9.gif
    Result of heat transfer distribution at duct surface
    KSMPE-18-7_F10.gif
    Result of temperature distribution at duct

    Table

    Reference

    1. Yi, C. S., Chin, D. H., “Numerical Analysis of the Development of an Air Conditioning Duct for Marine and Oil Drilling Ships”, Journal of the Korean Society of Manufacturing Process Engineers, Vol. 16, No. 2, pp. 50-55, 2017.
    2. Park, J. Y., Yi, C. S., Chin, D. H., “Numerical Analysis on the Development of Shut off Damper for Tsunami at Nuclear Plant”, Journal of the Korean Society of Manufacturing Technology Engineers, Vol. 23, No. 5, pp. 471-477, 2014.
    3. Yi, C. S., "Numerical Analysis of the Kitchen Hood Ventilation System for Marine Environment", Journal of the Korean Society of Manufacturing Process Engineers, Vol. 14, No. 5, pp. 96-101, 2015.
    4. Yi, C. S., Jang, S. C., Choi, J. H., "Numerical Analysis on Hood Shape Improvement of LocalVentilation System", Korean Journal of Air-Conditioning and Refrigeration Engineering, Vol. 21, No. 4, pp. 260-265, 2009.
    5. Jang, S. C., Jung. W. B., Yi. C. S., "A Study on Performance Improvement of Gear Type Vane Damper in Marine/Offshore FD Fan", Journal of the Korean Society of Manufacturing Process Engineers, Vol. 14, No. 2, pp. 7-13, 2015.
    6. Seo, J. H., Kim, B. T., Chin, D. H., Yoon, M. C., Kwak, J. S., "Comparison of the Contact Characteristics for Sealing strips of the Tsunami Damper", Journal of the Korean Society ofManufacturing Process Engineers, Vol. 14, No. 1, pp. 21-28, 2015.
    7. Lim, K. B., Lee, K. S. and Lee, C. H., "A Numerical Study on the Characteristics of Flow Field, Temperature and Concentration Distribution According to Changing the Shape of Separation Plate of Kitchen Hood System," Trans. Korean Soc. Mech. Eng. B., Vol. 30, No. 2, pp. 177-185, 2006.