DEVELOPMENT OF A FLOW NETWORK SIMULATION PROGRAM PART II – THERMAL ANALYSIS

J. LIM,K. Y. YANG 한국자동차공학회 2013 International journal of automotive technology Vol.14 No.3

An in-house simulation program is developed that can conveniently be utilized to predict flow and thermal characteristics such as velocity, pressure and temperature in any flow network systems comprising multiple flow components such as pipe, pump, heat exchanger, valves, etc. The program consists of two parts, the flow analysis for computing velocity and pressure and thermal analysis for temperature. The flow analysis portion of the program was dealt with in the Part I of the paper. Here, the thermal analysis part of the program is discussed. For the thermal analysis, first the flow analysis should be carried out to find out velocity and pressure in the network system, since this flow information is used as the input data for the thermal analysis. The mathematical and numerical formulations in the thermal analysis are very similar to those in the flow analysis. A thermal energy balance equation is applied to each thermal element with the unknown temperatures at nodes, while in the flow analysis both energy and mass conservation equation are applied to each flow element with two unknowns,velocity and pressure, at each node, so as to establish a set of non-linear algebraic equations that is to be iteratively solved by the Newton-Raphson scheme. In the program, five different flow and thermal elements respectively are treated, and believed to represent a variety of the network flow system in many practical engineering applications. However, the program can easily be extended to incorporate additional elements if necessary. In order to demonstrate the validity and applicability of the program, a comprehensive example of the engineering problems encountered in the vehicle development is introduced, and the solution process as well as accuracy of obtained results are discussed. Throughout the study, it is found that the program can most efficiently be used to find an optimal design concept among many potential design options in an early conceptual design phase of the vehicle development.

Thermal Analysis for Simulation of Metal Additive Manufacturing Process Considering Temperature- and History-Dependent Material Properties

정선호,박은교,강재원,조진연,김정호,김기철 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.1

Additive manufacturing (AM) technology is increasingly being used in the aerospace industry due to its advantages for aerospace components such as reduction of weight. A deep understanding of the behavior and properties of additively manufactured materials or parts is required to effectively carry out the certification process which is inevitable for aerospace components. However, since AM has so many parameters that affect the performance of products, the help of high-fidelity process simulation techniques is essential to fully analyze and understand their effects. In this research, we propose a new method to effectively implement the thermal analysis for process simulations of laser powder-bed fusion technique, a representative AM technique for metal materials, using existing commercial finite element analysis software. Thermal analysis for simulations of AM process is performed and the melt pool size is compared with test results to verify the accuracy of the simulation. In AM process simulations, material properties may vary significantly with temperature, and they are also dependent on the temperature history of the material because whether the current state is a powder or solid state is determined by the maximum temperature value in the past temperature history. Therefore, in this paper, user-defined subroutines and field variables are implemented so that the temperature history of each integration point for the finite element analysis can be properly tracked and appropriate material properties can be assigned accordingly. Using the proposed methods, thermal analysis for AM process simulations can be performed successfully with good accuracy compared with the existing test results.

Thermal-Analysis Modeling of High-Current Solid Targets for Radioisotope Production

Seuk-Kyu Kim,김재홍,Sang-Rok Kim 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.3

The large-scale production of various radioisotopes is usually done with a disk-type target system in which solid target materials are located in a stack with forced-water cooling. For the production of radioisotopes, metallic solid targets are irradiated by energetic protons produced by accelerators, which are capable of producing beam currents in excess of several hundreds of microamperes. Although the production yields of radioisotopes can be enhanced by employing a high-current proton beam, the maximum beam power (beam energy multiply by beam currents) deposited on targets is limited by the thermal characteristics of the target material and is associated with the loss of the target material due to high temperatures above the melting point. In this work, a computer program is applied to estimate the thermal transfer in solid targets during beam irradiation. The SRIM (stopping and ranges of ions in matter) 2003 program is used to calculate the energy deposited in the target material by using a quantum-mechanical treatment of ion-atom collisions. A detailed thermal analysis of such a solid target system under different bombardment conditions is made by means of a finite element analysis method. The results of a parameter study will be presented and discussed with the objective of maximizing the beam current limit of the solid target design employed at the 100 MeV proton accelerator facility at the Proton Engineering Frontier Project (PEFP). The large-scale production of various radioisotopes is usually done with a disk-type target system in which solid target materials are located in a stack with forced-water cooling. For the production of radioisotopes, metallic solid targets are irradiated by energetic protons produced by accelerators, which are capable of producing beam currents in excess of several hundreds of microamperes. Although the production yields of radioisotopes can be enhanced by employing a high-current proton beam, the maximum beam power (beam energy multiply by beam currents) deposited on targets is limited by the thermal characteristics of the target material and is associated with the loss of the target material due to high temperatures above the melting point. In this work, a computer program is applied to estimate the thermal transfer in solid targets during beam irradiation. The SRIM (stopping and ranges of ions in matter) 2003 program is used to calculate the energy deposited in the target material by using a quantum-mechanical treatment of ion-atom collisions. A detailed thermal analysis of such a solid target system under different bombardment conditions is made by means of a finite element analysis method. The results of a parameter study will be presented and discussed with the objective of maximizing the beam current limit of the solid target design employed at the 100 MeV proton accelerator facility at the Proton Engineering Frontier Project (PEFP).

CFD-Based Evaluation of the Efficiency for Solar Collectors with Fresnel Lenses

( Kyeong Sik Kang ),( Gwi Hyun Lee ) 한국농업기계학회 2023 한국농업기계학회 학술발표논문집 Vol.28 No.2

The main objectives of this study are to evaluate the performance of a solar thermal collection system utilizing Fresnel lenses through CFD simulation. Solar energy is an infinite energy source, and it can be used for heating and thermal systems. The efficiency of solar thermal energy systems is primarily dependent on the efficiency of the collector unit, leading to the development of various solar thermal systems. In this research, CFD numerical analyses were conducted on two types of solar collection systems using Fresnel lenses to maximize the efficiency of solar energy collection. The first system consists of 16 small Fresnel lenses, a square pipe through which the heat transfers medium flows, and the collector component, forming a flat plate type collector. The second system comprises a single large Fresnel lens and a double-cylinder shell-type absorber that absorbs heat from the lens. To perform CFD analysis, the geometry of the solar thermal collection system was created using 3D modeling software, and a mesh was generated on the 3D model. Subsequently, ANSYS Fluent 2022 R2 software was used to establish the physical models describing the fluid dynamics and heat transfer within the solar thermal collection system, along with setting boundary conditions involving external heat sources. Numerical analysis was then conducted using the software, and the results of both systems were analyzed. While the flat plate collector averaged 60-70% efficiency, a single large Fresnel lens with the double cylindrical shell absorber outperformed it by approximately 5% with an average efficiency of 65-75%. A satisfactory agreement was found when comparing the experimental data from previous studies with the results of this research. In the future, it is anticipated that this system can be further analyzed under various conditions, including different heat transfer media and solar radiation levels. A solar collector of the single large Fresnel lens had demonstrated higher efficiency, and it is believed that improvements in performance and cost-related challenges could make it suitable for applications requiring high energy efficiency, such as hot water supply and heating and cooling systems.

암반공동 열에너지저장소 주변 암반의 열-수리-역학적 연계거동 분석

박정욱(Jung-Wook Park),Jonny Rutqvist,류동우(Dongwoo Ryu),신중호(Joong-Ho Synn),박의섭(Eui-Seob Park) 한국암반공학회 2015 터널과지하공간 Vol.25 No.1

본 연구에서는 TOUGH2-FLAC3D 연계해석기법을 이용하여 암반공동에 고온의 열에너지를 30년간 저장하는 경우 주변 암반에 야기되는 열-수리-역학적 연계거동을 살펴보았다. 열에너지저장에 따른 암반의 거동 특성 및 환경 영향을 예측하고 이에 대한 제어기준을 수립하기 위한 기초 연구로서, 저장소 주변 암반에서 발생하는 열-수리 흐름과 역학적 거동의 상호작용에 대하여 검토하였다. 기본해석으로서 결정질 암반 내 원통형 공동에 350℃의 대용량 열에너지를 저장하는 경우를 모델링하였으며, 열에너지저장소의 단열성능은 고려하지 않았다. 암반 내 열전달의 주요 메카니즘은 암반의 전도에 의한 것으로 판단되며, 암반의 역학적 거동은 수리적 요소보다는 열적 요소에 지배적인 영향을 받는 것으로 나타났다. 암반과 지하수 가열에 따른 유효응력 재분포 양상과 열팽창으로 인한 암반 변위 및 지표 융기를 검토하였으며, 주변 암반에서의 전단파괴 위험도를 정량적인 수치를 통해 제시하였다. 암반 가열에 따른 열팽창으로 인하여 지표면에서 수 cm의 융기가 발생하였으며, 저장공동 상부에 인장응력이 크게 발달하면서 전단파괴의 위험도가 증가하는 것으로 나타났다. The thermal-hydrological-mechanical (T-H-M) behavior of rock mass surrounding a high-temperature cavern thermal energy storage (CTES) operated for a period of 30 years has been investigated by TOUGH2-FLAC3D simulator. As a fundamental study for the development of prediction and control technologies for the environmental change and rock mass behavior associated with CTES, the key concerns were focused on the hydrological-thermal multiphase flow and the consequential mechanical behavior of the surrounding rock mass, where the insulator performance was not taken into account. In the present study, we considered a large-scale cylindrical cavern at shallow depth storing thermal energy of 350℃. The numerical results showed that the dominant heat transfer mechanism was the conduction in rock mass, and the mechanical behavior of rock mass was influenced by thermal factor (heat) more than hydrological factor (pressure). The effective stress redistribution, displacement and surface uplift caused by heating of rock and boiling of ground-water were discussed, and the potential of shear failure was quantitatively examined. Thermal expansion of rock mass led to the ground-surface uplift on the order of a few centimeters and the development of tensile stress above the storage cavern, increasing the potential of shear failure.

저압 배선선로의 과부하 및 단락사고 발생시 전선의 열해석에 관한 연구

이상호,오홍석 한국화재소방학회 2002 한국화재소방학회논문지 Vol.16 No.3

최근 전계-열계해석 소프트웨어의 발전에 힘입어 전계-열계 해석 이론을 바탕으로 컴퓨터 시뮬레이션에 의한 전기화재의 정확한 원인분석과 조사가 체계적으로 연구되고 있으나, 매우 미흡한 실정이다. 따라서 본 논문에서는 국내 L사 제품(600V, VVF)의 전선을 모델로 하여 과부하 및 단락사고시 발생되는 전류 크기에 따른 전선의 열해석을 전계-열계 유한요소법(Flux2D)을 통하여 컴퓨터 시뮬레이션 하고자 한다. Recently, with the growth of software for electro-thermal analysis, it has been studied the precise analysis and investigation of cause for the electrical fire using computer simulation on the basis of theory for electro-thermal analysis. But it is very lacking for the precise analysis and investigation of cause for the electrical fire. In this paper, we have simulated the thermal analysis for electrical wire according to the value of current in a overload and a short with the electrical wire of the L's company product(600 V VVF) using the electro-thermal finite element method(Flux2D).

PMV 시뮬레이션의 불확실성 분석

안기언(Ahn Ki-Uhn),박철수(Park Cheol-Soo) 한국건축친환경설비학회 2011 한국건축친환경설비학회 학술발표대회 논문집 Vol.2011 No.3

The purpose of this study is to investigate the impact of uncertain parameters on PMV simulation runs. The uncertain parameters were chosen from the literature and the uncertainty propagation is introduced to treat the parameters which are not deterministic but stochastic. The Latin Hypercube Sampling (LHS) method, one of the Monte Carlo techniques, was selected for uncertainty propagation and die EnergyPlus was selected as an analysis simulation tool for the thermal comfort analysis. All of the precesses was automated in the Matlab platform. In the paper, tile impact of uncertainty on thermal comfort assessment in simulation are addressed.

확률론적 분석 기법을 이용한 해수온도차에너지 이용 냉난방 사업의 경제성 평가

김재엽,김현제 한국자원공학회 2019 한국자원공학회지 Vol.56 No.1

Faced with an energy transition era, more reliable economic analyses become mandatory for various businesses using new and renewable energy. This paper presents an economic analysis reflecting various uncertainties through one of the most widely used probabilistic economic analyses, called Monte Carlo simulation. In addition, by conducting a sensitivity analysis aimed at the main variables used in the probabilistic economic analysis, the influence level of each main variable on economic improvement of businesses using ocean thermal energy is specifically clarified. The methodologies and results of this study can be applied to micro-level economic analyses and policy decision-making to disseminate the use of ocean thermal energy on air-conditioning and heating systems. 에너지 전환시대에 직면한 오늘날, 신재생에너지원을 활용한 사업 수행 시 신뢰성 있는 경제성 평가가 그 어느 때보다 크게 요구되고 있다. 본 연구에서는 확률론적 경제성 분석 기법 중 몬테카를로 시뮬레이션(Monte Carlo simulation)을 이용하여 해수온도차에너지 냉난방 도입 시에 수반되는 불확실성을 고려한 경제성 분석을 수행하였다. 또한 해수온도차에너지 이용 냉난방 도입 시 경제성 평가에 활용된 주요 변수들을 대상으로 민감도 분석을 수행하여각 변수들에 발생한 변동이 경제성 분석 결과에 얼마나 큰 영향을 미치는지를 구체적으로 파악하였다. 본 연구의 방법론과 결과는 향후 보다 세분화된 변수를 바탕으로 한 경제성 분석 및 해수온도차에너지 냉난방 확대를 위한 정책적의사결정에 널리 활용될 수 있을 것이다.

도시구조 유형별 기온 형성 특성에 관한 연구

여인애,윤성환 대한건축학회지회연합회 2007 대한건축학회지회연합회 학술발표대회논문집 Vol.2007 No.1

This study aims at constructing EGIS DB of a coastal area Haeundae and performing statistical analysis for understanding urban structure and for ultimately accomplishing numerical simulation. The accomplished results of this study are as follows. 1)Building Information Database is constructed as integrating digital maps and building register file into an GIS Database. 2)EGIS DB is constructed as mesh data with environmental information data and preceding building information database. 3)EGIS DB is converted into statistical data supporting to accomplish statistical analysis and calculate urban structure factors' figures according to frequency analysis . 4) On the base of 18 urban planning items of study area, 6 component is pulled out according to Principal Com ponent Analysis and whole study area is grouped as 8 types. 5) To evaluate thermal environment of 8-type group, summer thermal environment simulation is carried out by UCSS (Urban Climate Simulation System) Box Model and the result is analysed on the side of air temperature and heat budget.

Development and evaluation of gypsum/shape-stabilization phase change materials using large-capacity vacuum impregnator for thermal energy storage

Lee, Jongki,Wi, Seunghwan,Yun, Beom Yeol,Yang, Sungwoong,Park, Ji Hun,Kim, Sumin Elsevier 2019 APPLIED ENERGY Vol.241 No.-

<P><B>Abstract</B></P> <P>The cost of energy use in buildings around the world is gradually increasing. To achieve energy saving in buildings, among the Thermal Energy Storage (TES) systems available, the use of Latent Heat Storage (LHS) is being actively studied. To effectively use an LHS system, Phase Change Materials (PCMs) are applied to buildings, and thus Shape-Stabilization PCMs (SSPCMs) must also be used. In this study, SSPCMs were manufactured using a large-capacity vacuum impregnation machine, and consisted of Exfoliated graphite nanoplatelets (xGnP) and n-octadecane. The SSPCMs were divided according to size (A, B, C, and D). SSPCMs were applied to a gypsum board (GB). Through a compressive strength test, a weight of 5% was applied to GB_A5, and the strength was reduced by 23.1% compared to GB and 50.1% for GB_A10. The thermal properties were analyzed based on a dynamic thermo-graphic analysis and dynamic heat flow analysis. From both analyses, it was confirmed that the GB with SSPCM showed a sufficient latent heat range and a corresponding exothermic range, compared to the reference GB. Based on EnergyPlus 8.5., a cooling energy reduction of approximately 3.4% was achieved through the addition of 10% SSPCMs to GB under the operating conditions. Therefore, it was proven that the application of SSPCMs to building materials is reasonable for achieving energy saving in buildings.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Shape-Stabilization Phase Change Material (SSPCM) was made n-octadecane with xGnP. </LI> <LI> SSPCM manufacturing process was conducted using novel vacuum impregnator. </LI> <LI> Thermally enhanced gypsum board was 1.91 °C higher in exothermic range than reference. </LI> <LI> Energy simulation results showed a saving of 11.39 kWh in performance. </LI> </UL> </P>