• Title/Summary/Keyword: Heat source or sink

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An Immersed-Boundary Finite-Volume Method for Simulation of Heat Transfer in Complex Geometries

  • Kim, Jungwoo;Park, Haecheon
    • Journal of Mechanical Science and Technology
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    • v.18 no.6
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    • pp.1026-1035
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    • 2004
  • An immersed boundary method for solving the Navier-Stokes and thermal energy equations is developed to compute the heat transfer over or inside the complex geometries in the Cartesian or cylindrical coordinates by introducing the momentum forcing, mass source/sink, and heat source/sink. The present method is based on the finite volume approach on a staggered mesh together with a fractional step method. The method of applying the momentum forcing and mass source/sink to satisfy the no-slip condition on the body surface is explained in detail in Kim, Kim and Choi (2001, Journal of Computational Physics). In this paper, the heat source/sink is introduced on the body surface or inside the body to satisfy the iso-thermal or iso-heat-flux condition on the immersed boundary. The present method is applied to three different problems : forced convection around a circular cylinder, mixed convection around a pair of circular cylinders, and forced convection around a main cylinder with a secondary small cylinder. The results show good agreements with those obtained by previous experiments and numerical simulations, verifying the accuracy of the present method.

Numerical Investigation on the Thermal Performance of a Cooling Device for a CPV Module (고집광 태양광 모듈용 냉각 장치의 열성능에 대한 수치 해석적 연구)

  • Do, Kyu Hyung;Kim, Taehoon;Han, Yong-Shik
    • Journal of the Korean Solar Energy Society
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    • v.35 no.1
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    • pp.1-8
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    • 2015
  • In the present study, the effects of the heat spreader thickness and the heat sink size on the thermal performance of a cooling device for a concentrating photovoltaic (CPV) module were numerically investigated. Numerical simulation was conducted by using the simulation tool ICEPAK, commercial software based on the finite volume method. Numerical results were validated by comparing the existing experimental data. The thermal performance of a cooling device, which consisted of a heat spreader and a natural convective heat sink, was evaluated with varying the heat spreader thickness and the heat sink size. The geometric configuration of the natural convective heat sink, such as the fin height, the fin spacing, and the fin thickness, was optimized by using the existing correlation. The numerical results showed that the thermal performance of the cooling device increased as the heat spreader thickness or the heat sink size increased. Also, it was found that the spreading thermal resistance plays an important role in the thermal performance of the cooling device which has the localized heat source.

An overview of Geothermal heat pumps as energy efficient and environmental friendly systems

  • Ahmad, Bilal;Kim, Dong-Hwan;Bahk, Sae-Mahn;Park, Myung-Kyun
    • Proceedings of the SAREK Conference
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    • 2008.06a
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    • pp.294-298
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    • 2008
  • The major threats that human being is facing nowadays are the Climate change, depletion of the fossil fuels at a rapid rate and energy costs. A significant portion of world energy consumption is consumed by domestic heating and cooling. And heat pumps, due to their higher utilization efficiencies as compared to conventional heating and cooling systems, offer an attractive solution to this problem. Among the types of heat pumps, the Geothermal heat pump or Ground-source heat pump is a highly efficient, renewable energy technology for space heating and cooling. The Ground-source heat pump uses the Earth as a heat sink in the summer and a heat source in the winter. And the Earth, having a relatively constant temperature, warmer than the air in winter and cooler than the air in summer, offers an excellent heat source in winter and heat sink in summer.. This paper will discuss an overview of the types of heat pumps, its operation, benefits of using geothermal heat pumps, soil characteristics, and overview of some experimental works. Finally it will briefly discuss the opportunity of using these energy efficient systems (EES) in the HVAC market of South Korea.

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THERMAL DIFFUSION AND RADIATION EFFECTS ON UNSTEADY MHD FREE CONVECTION HEAT AND MASS TRANSFER FLOW PAST A LINEARLY ACCELERATED VERTICAL POROUS PLATE WITH VARIABLE TEMPERATURE AND MASS DIFFUSION

  • Venkateswarlu, M.;Ramana Reddy, G.V.;Lakshmi, D.V.
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.18 no.3
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    • pp.257-268
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    • 2014
  • The objective of the present study is to investigate thermal diffusion and radiation effects on unsteady MHD flow past a linearly accelerated vertical porous plate with variable temperature and also with variable mass diffusion in presence of heat source or sink under the influence of applied transverse magnetic field. The fluid considered here is a gray, absorbing/emitting radiation but a non-scattering medium. At time t > 0, the plate is linearly accelerated with a velocity $u=u_0t$ in its own plane. And at the same time, plate temperature and concentration levels near the plate raised linearly with time t. The dimensionless governing equations involved in the present analysis are solved using the closed analytical method. The velocity, temperature, concentration, skin-friction, the rate or heat transfer and the rate of mass transfer are studied through graphs in terms of different physical parameters like magnetic field parameter (M), radiation parameter (R), Schmidt parameter (Sc), Soret number (So), Heat source parameter (S), Prandtl number (Pr), thermal Grashof number (Gr), mass Grashof number (Gm) and time (t).

The Performance Analysis of Multi Stage Reheater Organic Rankine Cycle According to Heat Sink Temperature Change (냉열원 온도 변화에 따른 다단재열랭킨사이클의 성능해석)

  • Lee, Ho-Saeng;Lim, Seung-Taek;Kim, Hyeon-Ju
    • Journal of Power System Engineering
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    • v.20 no.1
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    • pp.11-17
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    • 2016
  • In this study, the simulation for performance comparison between basic single stage organic rankine cycle, multi stage reheater cycle and multi stage reheater & recuperator cycle was carried out. The multi stage reheater cycle and multi stage reheater & recuperator cycle was designed to improve the efficiency for organic rankine cycle using heat source from industrial waste heat and heat sink from deep ocean water. R245fa was selected as a refrigerant for the cycle and system efficiencies were simulated by the variation of the heat sink temperature and the cycle classification. Performance characteristics were simulated by using the Aspen HYSYS. It was confirmed that the system efficiency was decreased by the increase of heat sink temperature. These results can be considered to be applied as geo-ocean thermal energy conversion in where plenty of geothermal or ocean thermal resource exist.

Effects of Working Fluids on the Performance Characteristics of Organic Rankine Cycle (ORC) Using LNG Cold Energy as Heat Sink (LNG 냉열을 열싱크로 이용하는 유기랭킨사이클(ORC)의 작동유체에 따른 성능 특성)

  • Kim, Kyoung Hoon;Ha, Jong Man;Kim, Kyung Chun
    • Transactions of the Korean hydrogen and new energy society
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    • v.25 no.2
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    • pp.200-208
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    • 2014
  • This paper presents thermodynamic performance analysis of organic Rankine cycle (ORC) using low temperature heat source in the form of sensible energy and using liquefied natural gas (LNG) as heat sink to recover the cryogenic energy of LNG. LNG is able to condense the working fluid at a very low condensing temperature in a heat exchanger, which leads to an increased power output. Based on the mathematical model, a parametric analysis is conducted to examine the effects of eight different working fluids, the turbine inlet pressure and the condensation temperature on the system performance. The results indicate that the thermodynamic performance of ORC such as net work production or thermal efficiency can be significantly improved by the LNG cold energy.

Three Reanalysis Data Comparison and Monsoon Regional Analysis of Apparent Heat Source and Moisture Sink (겉보기 열원 및 습기 흡원의 세 재분석 자료 비교와 몬순 지역별 분석)

  • Ha, Kyung-Ja;Kim, Seogyeong;Oh, Hyoeun;Moon, Suyeon
    • Atmosphere
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    • v.28 no.4
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    • pp.415-425
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    • 2018
  • The roles of atmospheric heating formation and distribution on the global circulation are of utmost importance, and those are directly related to not only spatial but also temporal characteristics of monsoon system. In this study, before we clarify the characteristics of apparent heat source <$Q_1$> and moisture sink <$Q_2$>, comparisons of three reanalysis datasets (NCEP2, ERA-Interim, and JRA-55) in its global or regional patterns are performed to clearly evaluate differences among datasets. Considering inter-hemispheric difference of global monsoon regions, seasonal means of June-July-August and December-January-February, which is summer (winter) and winter (summer) in the Northern (Southern) Hemisphere are employed respectively. Here we show the characteristics of eight different regional monsoon regions and find contributions of <$Q_2$> to <$Q_1$> for the regional monsoon regions. Each term in apparent heat source and moisture sink is shown to come from the ERA-Interim dataset, since the ERA-Interim could be representative of three datasets. The NCEP2 data has a different characteristic in the ratio of <$Q_2$> and <$Q_1$> because it overestimates <$Q_1$> compared to the other two different datasets. The Australia monsoon has been performing better over time, while some regional monsoons (South America, North America, and North Africa) have been showing increasing data inconsistency. In addition, the three reanalysis datasets are getting different marching with time, in particular since the early 2000s over South America, North America, and North Africa monsoon regions. The recent inconsistency among the three datasets that may be associated with the global warming hiatus remains unexplored.

Design of a Heat Dissipation System for the 400kW IGBT Inverter (400kW급 IGBT 인버터용 방열 시스템 설계)

  • 이진우
    • The Transactions of the Korean Institute of Power Electronics
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    • v.9 no.4
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    • pp.350-355
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    • 2004
  • This paper deals with the design of a heat dissipation system, which consists of a heat source of power semiconductor devices, a heat sink ;md a fan for the forced air cooling. It suggests the method of appropriately dividing the whole heat transfer system into analytical subsystems and also presents the correspondent analytic or experimental design equations for the subsystems. The experimental results on the designed heat dissipation system for the 400kW IGBT inverter show less than 10[%] error with respect to the design temperature and therefore verify the validity of the proposed analytical design method in the steady state.

The development of a ground source heat pump using R410A (R410A 대체냉매 적용 지열히트펌프 개발)

  • Kim, Ji-Dong;Chung, Bong-Chul;Jeong, Il-Kwon
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.3 no.1
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    • pp.17-22
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    • 2007
  • The growth of domestic energy demand is rapidly increased for the industrialization and the improvement of the living standards. It is also recognised that the importance of the use of environmentally friendly energy and high efficient equipment. Ground Source heat pumps (GSHP) using earth as heat source or sink are outstanding environmentally friendly energy systems which have high thermal efficiency when compared to conventional heating and cooling system. So government employs a policy and increase investment for expanding renewable energy market volume. Especially is established a system for obligatory usage of renewable energy to achieve 5% renewable energy diffusion rate by 2011. And the market demand for the ground source heat pump is rapidly growing due to its strong advantages. However domestic situation usually have been depended on the import of ground source heat pumps. In this paper, the results of development of a ground source heat pump using refrigerant R410A are reported.

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The development of a ground source heat pump using R410A (R410A 대체냉매 적용 지열히트펌프 개발)

  • Kim, Ji-Dong;Chung, Bong-Chul;Jeong, Il-Kwon
    • Proceedings of the SAREK Conference
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    • 2008.11a
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    • pp.99-102
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    • 2008
  • The growth of domestic energy demand is rapidly increased for the industrialization and the improvement of the living standards. It is also recognised that the importance of the use of environmentally friendly energy and high efficient equipment. Ground Source heat pumps(GSHP) using earth as heat source or sink are outstanding environmentally friendly energy systems which have high thermal efficiency when compared to conventional heating and cooling system. So government employs a policy and increase investment for expanding renewable energy market volume. Especially is established a system for obligatory usage of renewable energy to achieve 5% renewable energy diffusion rate by 2011. And the market demand for the ground source heat pump is rapidly growing due to its strong advantages. However domestic situation usually have been depended on the import of ground source heat pumps. In this paper, the results of development of a ground source heat pump using refrigerant R410A are reported.

  • PDF