Transient Hydrodynamic Phenomena and Conjugate Heat Transfer During Cooling of Water in an Underground Thermal Storage Tank

2004 ◽  
Vol 126 (1) ◽  
pp. 84-96 ◽  
Author(s):  
E. Papanicolaou ◽  
V. Belessiotis
Keyword(s):  
Heat Transfer ◽  
Storage Tank ◽  
Conjugate Heat Transfer ◽  
Transient Flow ◽  
Thermal Storage ◽  
Hot Water ◽  
Uniform Temperature ◽  
Thermal Fields ◽  
Flow And Heat Transfer ◽  
Insight Into

The flow and heat transfer phenomena inside an underground thermal storage tank, initially filled with hot water at an almost uniform temperature and then left to interact with the cold surroundings, are studied numerically. The purpose of the study is to gain insight into how these phenomena affect the heat losses to the surroundings, before a new charging process takes place. A two-dimensional numerical model to solve for the transient flow and thermal fields within the tank coupled with the heat transport through the tank walls and within the ground are employed. Natural convection is found to dominate at the early transients when a strong recirculation develops, with a Rayleigh number characteristic of turbulent flow. A low-Re k−ε turbulence model is used for the computation. As time proceeds and the temperature differences between water and surroundings decrease, the recirculation decays and the heat transfer is dominated by thermal diffusion. The ground properties are varied, mainly in order to account for different moisture contents in the ground. Comparisons are made under realistic conditions with preliminary experimental results showing satisfactory agreement.

scholarly journals Fabrication and Performance Evaluation of Cold Thermal Energy Storage Tanks Operating in Water Chiller Air Conditioning System

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4159
Author(s):  
Xuan Vien Nguyen
Keyword(s):  
Heat Transfer ◽  
Cold Storage ◽  
Storage Tank ◽  
Air Conditioning ◽  
Thermal Storage ◽  
Hot Water ◽  
Operating Costs ◽  
Heat Transfer Fluid ◽  
Storage Tanks ◽  
Air Conditioning System

In this study, cold and thermal storage systems were designed and manufactured to operate in combination with the water chiller air-conditioning system of 105.5 kW capacity, with the aim of reducing operating costs and maximizing energy efficiency. The cold storage tank used a mixture of water and 10 wt.% glycerin as a phase-change material (PCM), while water was used as heat transfer fluid (HTF). The cold storage heat exchanger was made of polyvinyl chloride (PVC). On the other hand, the thermal storage tank used water as the storage fluid with a capacity of 50 L of hot water per hour. The thermal storage did not use a pump for water transfer through the heat exchanger, so as to save energy and operating costs. In this paper, the operating parameters of the cold and thermal storage tanks are shown according to the results of experimental research, including the temperatures of cooling and heating load, heat transfer fluid, and cold storage material during the discharge process, as well as the discharge duration. The system assisted the air conditioner in cooling the internship workshop space at the university with an area of 400 m2, contributing to a remarkable reduction in air-conditioning system operating costs during the daytime. Furthermore, the system recovered waste heat from the compressor of the water chiller, and a thermal storage system was successfully built and operated, providing 50 L of hot water at a temperature of 60 °C per hour to serve the everyday needs of school students. This design was suitable for the joint operation of cold and thermal storage tanks and the water chiller air-conditioning system for cooling and heating applications.

LES Analysis of Flow and Heat Transfer in a Rib-Roughened Duct in Clockwise and Anti-Clockwise Rotation Regimes

2017 ◽  
Author(s):  
Alessandro Salvagni ◽  
Domenico Borello
Keyword(s):  
Heat Transfer ◽  
Constant Heat Flux ◽  
Rectangular Duct ◽  
Clockwise Rotation ◽  
Constant Heat ◽  
Flow And Heat Transfer ◽  
Axis Parallel ◽  
Secondary Motion ◽  
Heat Transfer Effects ◽  
Insight Into

We report on an LES study of effects of stabilising/destabilising rotation on heat transfer over a ribbed surface in a rectangular duct at Re = 15000. The duct bottom wall, ribbed by flow-normal, equally-spaced square-sectioned ribs, was uniformly heated (except for the ribs) by a constant heat flux. The duct was rotated with angular velocity corresponding to the rotation number of 0.3, around an axis parallel to the ribs in counter-clockwise (clockwise) direction, thus destabilising (stabilising) the ribbed-wall adjacent flow. These well-resolved LES gave some new insight into the rotation effects on flow and heat transfer providing information that are not easily accessible by experiments. An attempt was made to identify the heat transfer effects due to the rotation-induced modifications of the secondary motion.

Numerical Prediction of Combustor Heatshield Flow and Heat Transfer With Sub-Grid-Scale Modelling of Pedestals

2001 ◽  
Author(s):  
John K. Luff ◽  
James J. McGuirk
Keyword(s):  
Heat Transfer ◽  
Life Prediction ◽  
Conjugate Heat Transfer ◽  
Energy Equation ◽  
Flow And Heat Transfer ◽  
Extra Energy ◽  
Scale Modelling ◽  
Heat Transfer Calculation ◽  
Proper Account ◽  
Good Agreement

A goal for computational analysis of combustors is to produce a tool for life prediction. An important part of this will be the prediction of the temperature field in the combustor walls. The complex geometries of combustor components make this a formidable task. In this paper a 3D coupled numerical flow/conjugate heat transfer calculation procedure is presented for a combustor heatshield. Proper account must be taken of the blockage and heat transfer effects of pedestals. A scheme has been developed to account for these effects without resolving the pedestals in the computational grid. Extra sink terms are included in the momentum equations to account for pedestal pressure drop. An extra energy equation is solved to determine the local pedestal temperature and to account for heat transfer between pedestals and fluid. This treatment has been validated against empirical data for arrays of pedestals in ducts with good agreement for friction factor and Nusselt number. The methodology is then applied to a generic heatshield geometry to indicate that a viable computational route has been developed for combustor heatshield analysis.

Mathematical Modeling of Transient Flow and Heat Transfer in Gas Stirred Molten Steel

2001 ◽  
Author(s):  
J. L. Xia ◽  
T. Ahokainen
Keyword(s):  
Heat Transfer ◽  
Molten Steel ◽  
Thermal Stratification ◽  
Transient Flow ◽  
Liquid Interface ◽  
Turbulent Dispersion ◽  
Steel Ladle ◽  
Bubble Liquid ◽  
Flow And Heat Transfer ◽  
Heat Transfer Correlations

Abstract Transient two phase flow and heat transfer in a gas-stirred steel ladle are numerically investigated. An Eulerian two fluid approach is used. The drag, lift and turbulent dispersion forces are taken into account for the interface interactions. Different interface heat transfer correlations such as Ranz-Marshall and Hughmark relations are used to examine the influence of heat transfer between gas-liquid interface on the flow. The flow pattern, the histories of both gas and molten steel temperatures, and the thermal stratification history are presented. Results show that gas injection can homogenize thermal field and result in a thermal stratification of about 2 °C only (not complete homogenization). The different heat transfer correlations examined for the bubble-liquid interface have negligible impact on the flow and thermal fields. Predictions are compared with experimental data measured in an industrial ladle and a reasonable agreement is achieved.

Conjugate heat transfer study of hypersonic flow past a cylindrical leading edge composed of functionally graded materials

2021 ◽  
pp. 095440622110481
Author(s):  
Bibin John ◽  
Sudhanva Kusuma Chandrashekhara ◽  
Vivekkumar Panneerselvam
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Functionally Graded Materials ◽  
Isotropic Material ◽  
Conjugate Heat Transfer ◽  
Thermal Protection ◽  
Leading Edge ◽  
Functionally Graded ◽  
Graded Materials ◽  
Flow And Heat Transfer

Aero-thermodynamic analysis of a cylindrical leading edge placed in a hypersonic stream is carried out using an in-house developed conjugate heat transfer (CHT) solver. Isotropic and functionally graded materials (FGM) are tested as heat shields to understand the effects of the material property on the flow structure and aerodynamic heating associated with the mutual coupling of fluid flow and heat transfer. A simplified partitioned approach is employed to couple the independently developed fluid flow and heat transfer solvers to perform conjugate heat transfer studies. This framework employs a cell-centred finite volume formulation with an edge-based algorithm. Both strong and loose coupling algorithms are implemented for the data transfer across the fluid–solid interface. A test case of hypersonic flow over a cylindrical leading edge composed of an isotropic material is considered to validate the accuracy and correctness of numerical formulation adopted in the in-house solver. The significance of solid domain materials on the conjugate heat transfer has been studied by considering both isotropic material and FGM. The loosely coupled CHT solver required 10 times less simulation time when compared with the strongly coupled CHT solver. The interface heat flux evolution over time showed a decreasing trend, whereas an increasing trend was for the interface temperature. The current study strongly recommends CHT analysis for the design of thermal protection system of space vehicles. The thermal performance of FGMs composed of various volume fractions of Zirconia and Titanium alloy (Ti6Al4V) is assessed. The temperature distributions obtained from the CHT analysis shows that FGM with a power index of unity is a good material choice for thermal protection systems.

Integrated Fluxes in Magneto-Hydrodynamic Mixed Convection in a Cavity Sustained by Conjugate Heat Transfer

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Orkodip Mookherjee ◽  
Shantanu Pramanik
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Flux ◽  
Kinetic Energy ◽  
Mixed Convection ◽  
Conjugate Heat Transfer ◽  
Numerical Study ◽  
Horizontal Magnetic Field ◽  
Flow And Heat Transfer ◽  
Stationary Interface

Abstract A numerical study of magneto-hydrodynamic mixed convection in a cavity has been conducted to investigate the influence of magnetic field on integrated flux of thermal energy, linear momentum, and kinetic energy. Shear force through lid motion establishes the forced convection effect and buoyancy force due to differential heating of the moving lid and the stationary interface ensures the natural convection phenomenon. Additionally, conduction through the solid slab with prescribed temperature at the outer surface attached to the cavity induces conjugate heat transfer. Further, the top and bottom walls throughout the domain are kept insulated and a uniform horizontal magnetic field is applied on the interface toward left. Fluid flow and heat transfer characteristics are examined for a range of Hartmann number (Ha): 0, 10, 50, and 120 at fixed values of Reynolds number, Grashof number, and Prandtl number of 300, 9 × 104 and 0.71, respectively. The result shows that the transport of heat in the near wall regions of the fluid domain is primarily governed by diffusion, whereas advection appears stronger in the central region of the cavity. Increase in magnetic field strength from Ha = 0 to 120 gradually suppresses the recirculating structure of the flow signifying a reduction in advective strength as depicted by the decrease in the value of total integrated heat flux from 25.15×10-3 to 6.0×10-3. The reduction in heat flux, momentum fluxes, and kinetic energy fluxes with increase in magnetic field has been well correlated in the range of 0≤Ha≤120.

Numerical Research of Roughness Effects on Flow and Heat Transfer Characteristics in Flat Microchannels

2009 ◽  
Author(s):  
Heming Yun ◽  
Baoming Chen ◽  
Binjian Chen
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Reynolds Number ◽  
Conjugate Heat Transfer ◽  
Entrance Length ◽  
Heat Transfer Characteristics ◽  
Roughness Effects ◽  
Relative Roughness ◽  
Flow And Heat Transfer ◽  
Numerical Research

Roughness effects on flow and heat transfer in flat microchannels has been numerically simulated by using CFD with fluid-solid conjugate heat transfer techniques, the surface roughness has been modeled through a series triangular toothed roughness cells. In this paper, the influence for roughness on the entrance length of flow and heat transfer has been emphasized, the influence for relative roughness on transitional Reynolds number has been also analyzed at the same time.

Experimental Study on Single-Phase Gas Flow in Microtubes

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
T. T. Zhang ◽  
L. Jia ◽  
C. W. Li ◽  
L. X. Yang ◽  
Y. Jaluria
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Single Phase ◽  
Slip Flow ◽  
Experimental System ◽  
Flow Region ◽  
Flow And Heat Transfer ◽  
Wide Range ◽  
Physical Insight ◽  
Insight Into

An experimental system for single-phase gas flow in microtubes has been developed. The effects of viscous heating and compressibility on the flow and temperature field were studied for a wide range of governing parameters. Also, an analytical/numerical model of the flow was developed. Numerical results for the flow and heat transfer in the slip flow region were found to agree quite well with the experimental data, lending support to the model. The study provides greater physical insight into and understanding the effects of viscous dissipation and compressibility in microtube flow and the associated heat transfer. In addition, the combined experimental and numerical simulation approaches of the process can be used for control and optimization of systems based on microtube heat transfer.

scholarly journals Numerical Simulation Study for the Performance of a Large Solar Hot Water System With Horizontal Storage Tank

2015 ◽  
Author(s):  
Ru Yang ◽  
Geng-Yi Lin
Keyword(s):  
Numerical Simulation ◽  
System Performance ◽  
Storage Tank ◽  
Large Scale ◽  
Cooling System ◽  
Water System ◽  
Thermal Storage ◽  
Hot Water ◽  
Design Parameters ◽  
Total Load

A large solar hot water system can be utilized to provide driving energy for heating system, heat-driven cooling system, as well as to provide hot water. This research addresses the effects of the storage tank design parameters on the performance of a large-scale solar hot water system with a horizontal storage tank. Most literatures only considered the stratification performance of the thermal storage tank itself instead of considering the overall system performance. Also, there is lack of experimental research data available for the design purpose. Therefore, this study employs a numerical simulation technique to study the design parameters effect of a horizontal thermal storage tank on the performance of a large-scale solar hot water system. In this study, the ANSYS-CFX program is employed to calculate the flow and temperature distributions inside horizontal thermal storage tank. Then the inlets and outlets of the tank are combined with the TRNSYS program to simulate the entire system performance under the weather of three representative cities of Taiwan, (Taipei, Taichung and, Kaohsiung). The results of the present study indicate that the vertical stratification baffles in the tank have important effects on system performance improvement. Quantitative increase of solar fraction of the total load is obtained. The comparison with the system with vertical storage tank is provided. The results of the present study can provide important reference for the large solar hot water system design in improving system efficiency.

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