Discharge of Thermal Storage Tanks via Immersed Baffled Heat Exchangers: Numerical Model of Flow and Temperature Fields

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Yan Su ◽  
Jane H. Davidson
Keyword(s):  
Heat Exchanger ◽  
Discharge Rate ◽  
Thermal Storage ◽  
Flow Speed ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Stored Energy ◽  
Tube Heat Exchanger ◽  
Temperature And Velocity Fields ◽  
Cylindrical Baffle

A model of a thermal storage tank in which stored energy is extracted via an immersed heat exchanger is presented and used to predict transient temperature and velocity fields in tanks with and without baffles. The heat exchanger is modeled as a porous medium within the storage fluid. A simple cylindrical baffle that creates an annular space in which a coiled tube heat exchanger is positioned provides a modest increase in the rate of energy extraction compared to a tank with no baffle. The improved discharge rate is attributed to an increase in the flow speed across the heat exchanger. A baffle with greater hydraulic resistance slows the flow and reduces performance.

Discharge of Thermal Storage Tanks via Immersed Baffled Heat Exchangers: Numerical Model of Flow and Temperature Fields

2007 ◽  
Author(s):  
Yan Su ◽  
Jane H. Davidson
Keyword(s):  
Heat Exchanger ◽  
Discharge Rate ◽  
Thermal Storage ◽  
Flow Speed ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Stored Energy ◽  
Tube Heat Exchanger ◽  
Temperature And Velocity Fields ◽  
Cylindrical Baffle

A model of a thermal storage tank in which stored energy is extracted via an immersed heat exchanger is presented and used to predict transient temperature and velocity fields in tanks with and without baffles. The heat exchanger is modeled as a porous medium within the storage fluid. A simple cylindrical baffle that creates an annular space in which a coiled tube heat exchanger is positioned provides a modest increase in the rate of energy extraction compared to a tank with no baffle. The improved discharge rate is attributed to an increase in the flow speed across the heat exchanger. A baffle with greater hydraulic resistance slows the flow and reduces performance.

Simulation of Temperature Field of Soil Inside Drilling around a Vertically Buried Single-U-Tube Ground Heat Exchanger

2011 ◽  
Vol 393-395 ◽  
pp. 943-946
Author(s):  
Zhen Yu Du
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Soil Temperature ◽  
Moisture Transfer ◽  
Temperature Fields ◽  
Tube Heat Exchanger ◽  
Heat Transfer Efficiency ◽  
Ground Source ◽  
Practical Engineering ◽  
One Year

In this paper, the mathematical physical model of the heat and moisture transfer, which is about a vertical single-U-tube heat exchanger of a ground source heat pump (GSHP), is used to simulate the soil temperature fields inside drilling around a vertical single-U-tube ground source heat exchanger. The soil temperature fields inside drilling in the GSHP project running for one year are computed numerically. It shows that soil structure, cooling and heating load, cooling and heating period, and convalescence period have been determined by practical engineering conditions, the distance in the plane between drillings have a huge influence on heat transfer effect, only when the distance is designed reasonably, can it be possible to make sure normal heat transfer efficiency.

CFD Modeling and Analysis of a Shell-and-Tube Heat Exchanger

2008 ◽  
Author(s):  
Ender Ozden ◽  
I˙lker Tarı
Keyword(s):  
Heat Exchanger ◽  
Turbulence Modeling ◽  
Turbulence Models ◽  
Temperature Fields ◽  
Cfd Modeling ◽  
Shell Side ◽  
Cfd Simulations ◽  
Tube Heat Exchanger ◽  
Shell And Tube ◽  
Side Flow

A shell-and-tube heat exchanger is modeled and numerically analyzed using a commercial finite volume CFD package. The heat exchanger is small, has a single shell and a single tube pass, and its shell side is baffled. The baffles are 25% or 36% cut single-segmental baffles. Tube layout is the staggered layout with a triangular pitch. There is no leakage from baffle orifices and no gap between the baffles and the shell. It is observed that the shell side flow and the temperature distributions are very sensitive to modeling choices such as mesh, order of discretization and turbulence modeling. Various turbulence models are tried for the first and second order discretizations using two different mesh densities. CFD predictions of shell side pressure drop and overall heat transfer coefficient are obtained and compared with Kern and Bell-Delaware method results. After selecting the best modeling approach, the sensitivity of the results to flow rates and the baffle spacing is investigated. It is observed that the flow and temperature fields obtained from CFD simulations can provide valuable information about the parts of the heat exchanger design that need improvement. Correlation based approaches may indicate the existence of the weakness but CFD simulations can also pin point the source and the location of it. Using CFD together with experiments may speed up the design process and may improve the final design.

Research of Combined Heating and Cooling by Solar Ground-Source Heat Pump and PCM Thermal Storage

Solar Energy ◽  
2005 ◽  
Author(s):  
Li-Xia Wu ◽  
Mao-Yu Zheng
Keyword(s):  
Heat Exchanger ◽  
Solar Energy ◽  
Cooling System ◽  
Storage System ◽  
Thermal Storage ◽  
Cold Climate ◽  
Coefficient Of Performance ◽  
Tube Heat Exchanger ◽  
Heating And Cooling ◽  
Ground Source

In severely cold climate, significant amount of energy is used to heat buildings. Both the theoretical computation and experiments show that it is difficult and uneconomical to use solar energy collected merely in winter. A new method has been developed to store solar energy during summer, fall, and spring for winter heating. This paper presents in details the combined heating and cooling system by solar ground-source heat pump (GSHP) and short-term phase change material (PCM) thermal storage. The hybrid system and season-shift mode can make the sustainable use of solar energy possible. As for the above system, the solar energy collected is stored into soil through the U-tube heat exchanger. In winter, the thermal energy is taken out for heating using the GSHP. At the end of the heat supply season, the underground soil temperature may drop below 0°C. Then some heat exchangers begin to store the heat into soil while others stop. In summer, the U-tube heat exchanger is used to produce low temperature water without compressor to cool the room. The project was supported by the Energy Conservation Laboratory at Harbin Institute of Technology (HIT). The whole systems, which have run for over two years, consist of a flat plate solar hot water system installed on the roof, a soil thermal storage system, a GSHP system, a PCM thermal storage system and heating-cooling system. The measured results show an average heating coefficient of performance (COP) of 3.2 in winter and the cooling coefficient of performance (COP) of 18.0 in summer. The PCM thermal storage system has been investigated by numerical simulation and experiments in the cold climate. In most time of winter, the PCM thermal storage system was used to supply heat, while solar GSHP was also used during continuous cloudy days and severely cold days. The result shows that above method is feasible. The most advantage of this system is that it does not need the usual energy equipment. The numerical analysis has been used to investigate the thermal energy balance of the underground soil. The variation of the soil temperature field around the U-tube heat exchanger has also been studied, not only for the single exchanger but also for multiple exchangers. The underground soil makes the yearly thermal balance possible because the solar energy supplies the heat that is extracted from the soil for heating in winter. Then this system can operate for a long period.

Thermomechanical Design of a Heat Exchanger for a Recuperative Aeroengine

2006 ◽  
Vol 128 (4) ◽  
pp. 736-744 ◽  
Author(s):  
Harald Schoenenborn ◽  
Ernst Ebert ◽  
Burkhard Simon ◽  
Paul Storm
Keyword(s):  
Thermal Analysis ◽  
Heat Exchanger ◽  
Boundary Conditions ◽  
Stress Analysis ◽  
Element Model ◽  
Automatic Generation ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Engine Operation ◽  
Aero Engines

Within the framework programs of the EU for Efficient and Environmentally Friendly Aero-Engines (EEFEA) MTU has developed a highly efficient cross-counter flow heat exchanger for the application in intercooled recuperated aeroengines. This very compact recuperator is based on the profile tube matrix arrangement invented by MTU and one of its outstanding features is the high resistance to thermal gradients. In this paper the combined thermomechanical design of the recuperator is presented. State-of-the-art calculation procedures for heat transfer and stress analysis are combined in order to perform a reliable life prediction of the recuperator. The thermal analysis is based upon a 3D parametric finite element model generation. A program has been generated, which allows the automatic generation of both the material mesh and the boundary conditions. Assumptions concerning the boundary conditions are presented as well as steady state and transient temperature results. The stress analysis is performed with a FEM code using essentially the same computational grid as the thermal analysis. With the static temperature fields the static loading of the profile tubes is determined. From transient thermal calculations successive 3D temperature fields are obtained which enable the determination of creep life and LCF life of the part. Finally, vibration analysis is performed in order to estimate the vibration stress of the profile tubes during engine operation. Together with the static stress a Goodman diagram can be constructed. The combined analysis shows the high life potential of the recuperator, which is important for economic operation of a recuperative aero-engine.

scholarly journals Study on Shell-and-Tube Heat Exchanger Models with Different Degree of Complexity for Process Simulation and Control Design

2018 ◽  
Author(s):  
Javier Bonilla
Keyword(s):  
Heat Exchanger ◽  
Molten Salt ◽  
Heat Exchangers ◽  
Control Strategies ◽  
Thermal Storage ◽  
Working Fluid ◽  
Tube Heat Exchanger ◽  
Test Loop ◽  
Shell And Tube ◽  
Thermal Oil

Many commercial solar thermal power plants rely on indirect thermal storage systems in order to provide a stable and reliable power supply, where the working fluid is commonly thermal oil and the storage fluid is molten salt. The thermal oil - molten salt heat exchanger control strategies, to charge and discharge the thermal storage system, strongly affect the performance of the whole plant. Shell-and-tube heat exchangers are the most common type of heat exchangers used in these facilities. With the aim of developing advanced control strategies accurate and fast dynamic models of shell-and-tube heat exchangers are essential. For this reason, several shell-and-tube heat exchanger models with different degrees of complexity have been studied, analyzed and validated against experimental data from the CIEMAT-PSA molten salt test loop for thermal energy systems facility. Simulation results are compared in steady-state as well as transient predictions in order to determine the required complexity of the model to yield accurate results.

Numerical Investigation on a Flat - Tube Heat Exchanger in Metal Foam

2019 ◽  
Author(s):  
Bernardo Buonomo ◽  
Furio Cascetta ◽  
Anna di Pasqua ◽  
Piera Ginetti ◽  
Oronzio Manca
Keyword(s):  
Heat Exchanger ◽  
Numerical Solutions ◽  
Metal Foam ◽  
Volume Averaging ◽  
Temperature Fields ◽  
Ansys Fluent ◽  
Flat Tube ◽  
Flow Equations ◽  
Tube Heat Exchanger ◽  
Flat Tubes

Abstract A numerical analysis on a heat exchanger in aluminum foam with flat tubes is accomplished. The flow equations in two-dimensional steady state regime are written considering the local volume averaging process. The foam considered as an open porous medium is modelled in local thermal non-equilibrium (LTNE) under the Darcy-Brinkman-Forchheimer hypothesis. The metal foam behaviors such as porosity and pore density (pore per inch, PPI) are assigned equal to 0.9353 and 20. Several configurations of the flat tube with different dimensions are considered. A fixed surface temperature on the flat tube is selected and several mass flow rates are examined. The numerical solutions are carried out by means of the Ansys-FLUENT code Pressure drop in the system and average heat transfer coefficient on the flat tube external surfaces are presented. Moreover, pressure and temperature fields are reported for the different configurations. At the end, a comparison with the same scheme characterized by a circular tube is accomplished.

Influence of Convalescence on Soil Temperature Field around a Vertically Buried Single-U-Tube Ground Heat Exchanger

2011 ◽  
Vol 121-126 ◽  
pp. 1651-1655
Author(s):  
Zhen Yu Du ◽  
Yi Xing Zhang
Keyword(s):  
Temperature Field ◽  
Heat Exchanger ◽  
Soil Temperature ◽  
Moisture Transfer ◽  
Thermal Response ◽  
Geological Structure ◽  
Temperature Fields ◽  
Tube Heat Exchanger ◽  
Depth Direction ◽  
Single Well

The mathematical physical model of the heat and moisture transfer in the single-U-tube heat exchanger of a ground source heat pump (GSHP) is validated using observed data from the practical rock-soil thermal response test on a resident district in Taiyuan, the soil is layered according to the geological structure of an actual drill in the depth direction in this model. Inputting the dynamic design cooling and heating load of the district into the Realizable turbulent model in Fluent, the temperature fields of a single well in the GSHP project running for 1 year in 2 conditions in which convalescence is considered and not, are simulated numerically. It shows that it rather necessary to take the influence of convalescence into consideration while predicting the soil temperature field of a GSHP system running for a long term, or may not correspond to the reality and make a wrong theory guide to the practical engineering.

Genetic Algorithm Optimization of a Compact Heat Exchanger Modeled Using Volume Averaging Theory

2012 ◽  
Author(s):  
David Geb ◽  
Feng Zhou ◽  
George DeMoulin ◽  
Ivan Catton
Keyword(s):  
Genetic Algorithm ◽  
Heat Exchanger ◽  
Fitness Function ◽  
Volume Averaging ◽  
Averaging Theory ◽  
Temperature Fields ◽  
Tube Heat Exchanger ◽  
Finned Tube Heat Exchanger ◽  
Multiple Parameter ◽  
Volume Averaging Theory

This paper proposes and implements a new methodology for optimizing Compact Heat Exchangers (CHXs) using a Volume Averaging Theory (VAT) model and a Genetic Algorithm (GA) optimizer. This method allows for multiple-parameter optimization of CHXs by design of their basic morphological structures, and is applied to a Finned-Tube Heat Exchanger (FTHX). A consistent model is used to describe transport phenomena in a FTHX based on VAT, which allows for the volume averaged conservation of mass, momentum, and energy equations to be solved point by point, with the morphology of the structure directly incorporated into the field equations. The equations differ from known equations and are developed using a rigorous averaging technique, hierarchical modeling methodology, and fully turbulent models with Reynolds stresses and fluxes in the space of every pore. These averaged equations have additional integral and differential terms that must be dealt with in order for the equation set to be closed, and recent work has provided this closure. The resulting governing equation set is relatively simple and is discretized and solved using the finite difference method. Such a computational algorithm is fast running, but still able to present a detailed picture of the temperature fields in both of the fluid flows as well as in the solid structure of the heat exchanger. A GA is integrated with the VAT-based solver to carry out the FTHX optimization, which is a ten parameter problem, and the FTHX’s effectiveness is selected as the fitness function to be optimized. This method of using the VAT-based solver fully integrated with a GA optimizer results in an all-in-one tool for performing multiple-parameter constrained optimization on FTHXs.

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