Numerical Investigation of Metal-Foam Filled Liquid Piston Compressor Using a Two-Energy Equation Formulation Based on Experimentally Validated Models

2013 ◽  
Author(s):  
Chao Zhang ◽  
Jacob H. Wieberdink ◽  
Farzad A. Shirazi ◽  
Bo Yan ◽  
Terrence W. Simon ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Equation ◽  
Cfd Simulation ◽  
Metal Foam ◽  
Piston Compressor ◽  
Interfacial Heat Transfer ◽  
Cfd Simulations ◽  
Fluid Mixture ◽  
Liquid Piston ◽  
Transfer Term

The present study presents CFD simulations of a liquid-piston compressor with metal foam inserts. The term “liquid-piston” implies that the compression of the gas is done with a rising liquid-gas interface created by pumping liquid into the lower section of the compression chamber. The liquid-piston compressor is an essential part of a Compressed Air Energy Storage (CAES) system. The reason for inserting metal foam in the compressor is to reduce the temperature rise of the gas during compression, since a higher temperature rise leads to more input work being converted into internal energy, which is wasted during the storage period as the compressed gas cools. Liquid, gas, and solid coexist in the compression chamber. The two-energy equation model is used; the energy equations of the fluid mixture and the solid are coupled through an interfacial heat transfer term. The fluid mixture, which includes both the gas phase and the liquid phase, is modeled using the Volume of Fluid (VOF) method. Commercial CFD software, ANSYS FLUENT, is used, by applying its default VOF code, with user-defined functions to incorporate the two-energy equation formulation for porous media. The CFD simulation requires modeling of a negative momentum source term (drag), and an interfacial heat transfer term. The first one is the pressure drop due to the metal foam, which is obtained from experimental measurements. To obtain the interfacial heat transfer term, a compression experiment is done, which provides instantaneous pressure and volume data. These data are compared to solutions of a zero-dimensional compression model based on different heat transfer correlations from published references. By this comparison, a heat transfer correlation which is most suitable for the present study is chosen for use in the CFD simulation. The CFD simulations investigate two types of metal foam inserts, two different layouts of the insert (partial vs. full), and two different liquid piston speeds. The results show the influence of the metal foam inserts on secondary flows and temperature distributions.

A Correlation for Interfacial Heat Transfer Coefficient for Turbulent Flow Over an Array of Square Rods

2005 ◽  
Vol 128 (5) ◽  
pp. 444-452 ◽  
Author(s):  
Marcelo B. Saito ◽  
Marcelo J. S. de Lemos
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Transfer Coefficient ◽  
Turbulent Flow ◽  
Transfer Coefficient ◽  
Energy Equation ◽  
Local Thermal Equilibrium ◽  
Equation Modeling ◽  
Interfacial Heat Transfer Coefficient ◽  
Interfacial Heat Transfer

Interfacial heat transfer coefficients in a porous medium modeled as a staggered array of square rods are numerically determined. High and low Reynolds k-ϵ turbulence models are used in conjunction of a two-energy equation model, which includes distinct transport equations for the fluid and the solid phases. The literature has documented proposals for macroscopic energy equation modeling for porous media considering the local thermal equilibrium hypothesis and laminar flow. In addition, two-energy equation models have been proposed for conduction and laminar convection in packed beds. With the aim of contributing to new developments, this work treats turbulent heat transport modeling in porous media under the local thermal nonequilibrium assumption. Macroscopic time-average equations for continuity, momentum, and energy are presented based on the recently established double decomposition concept (spatial deviations and temporal fluctuations of flow properties). The numerical technique employed for discretizing the governing equations is the control volume method. Turbulent flow results for the macroscopic heat transfer coefficient, between the fluid and solid phase in a periodic cell, are presented.

CFD Simulations of Natural Convection/Radiation Heat Transfer Within the Fuel Regions of a Truck Cask for Normal Transport

2007 ◽  
Author(s):  
Venkata V. R. Venigalla ◽  
Miles Greiner
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Generation ◽  
Cfd Simulation ◽  
Radiation Heat Transfer ◽  
Thermal Capacity ◽  
Generation Rate ◽  
Heat Generation Rate ◽  
Radiation Heat ◽  
Cfd Simulations

A two-dimensional finite volume mesh is constructed that accurately represents the geometry of a legal weight truck cask, including four PWR fuel assemblies inside. CFD simulations calculate buoyancy driven gas motion as well as natural convection and radiation heat transfer in the gas filled fuel regions. They also calculate conduction within the cask solid components. The cask is in a normal transportation environment. The fuel and cask temperatures are calculated for ranges of fuel heat generation rate and cladding emissivity, for both helium and nitrogen backfill gas. The cask thermal capacity, which is the fuel heat generation rate that brings the peak fuel cladding to its temperature limit, is also determined. The results are compared to simulations in which the gas speed is set to zero, to determine the effect of buoyancy induced motion. The allowable heat generation rate is 23% higher for helium than for nitrogen due to helium’s higher thermal conductivity. Increasing the cladding emissivity by 10% increases the allowed fuel heating rate by 4% for nitrogen, but only 2% for helium. The higher value for nitrogen is caused by the larger fraction of heat transported by radiation when it is the backfill gas compared to helium. The stagnant-gas calculations give only slightly higher cladding temperatures than the gas-motion simulations. This is because buoyancy induced gas motion does not greatly enhance heat transfer compared to conduction and radiation for this configuration. The cask thermal capacity from the stagnant-CFD calculation is therefore essentially the same as that from the CFD simulation. This suggests that future cask thermal calculations may not need to include gas motion. These results must be experimentally benchmarked before the CFD methods can be used with confidence for designing transport casks. Basket surface temperatures calculated in this work can be used as the basis for boundary condition in those experiments.

scholarly journals Transient 3D CFD Simulation of a Stationary Vane, Oil Free, Rotary Compressor

2019 ◽  
Vol 63 (4) ◽  
pp. 308-318 ◽  
Author(s):  
Balázs Farkas ◽  
Jenő Miklós Suda
Keyword(s):  
Cfd Simulation ◽  
Piston Compressor ◽  
Working Fluid ◽  
Rotary Compressor ◽  
Heat Sources ◽  
Cfd Model ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Rolling Piston ◽  
Good Agreement

The evaluation of a newly designed oil-free rotary compressor is presented based on transient 3D Computational Fluid Dynamics (CFD) simulations. The simulations are performed at low compression ratios and low pressure ratios and low rotational speeds. To place the results into context, the data presented in related literature was processed and summarized. The methods related to the CFD model of the newly designed compressor were developed, summarized and evaluated. The accessed CFD data are in good agreement with the results of the former rolling piston compressor related investigations. The oil free operation prevents the contamination of the working fluid from lubricant. Since the compressor is planned to work in open cycle within the sensitive environment of thermal heat sources contamination free operation has to be accomplished. However, oil-free operation also results in significantly lower performance based on the modelling results.

Direct Simulation of Interstitial Heat Transfer Coefficient Between Paraffin and High Porosity Open-Cell Metal Foam

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Yuanpeng Yao ◽  
Huiying Wu ◽  
Zhenyu Liu
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Change Process ◽  
Energy Equation ◽  
Metal Foam ◽  
Equation Model ◽  
High Porosity ◽  
Direct Simulation ◽  
Open Cell ◽  
Transfer Region

The interstitial heat transfer coefficient (IHTC) is a key parameter in the two-energy equation model usually employed to investigate the thermal performance of high porosity open-cell metal foam/paraffin composite phase change material. Due to the existence of weak convection of liquid paraffin through metal foam during phase change process, the IHTC should be carefully determined for a low Reynolds number range (Re = 0–1), which however has been rarely addressed in the literature. In this paper, a direct simulation at foam pore scale is carried out to determine the IHTC between paraffin and metal foam at Re = 0–1. For this purpose, the cell structures reflecting realistic metal foams are first constructed based on the three-dimensional (3D) Weaire–Phelan foam cell to serve as the representative elementary volume (REV) of metal foam for direct simulation. Then, by solving the Navier–Stokes equations and energy equation for the REV, the influences of Reynolds number (Re), Prandtl number (Pr), foam porosity (ε), and pore density (PPI) on the dimensionless IHTC, i.e., the Nusselt number Nuv, are investigated. According to the numerical results, a correlation of Nuv at Re = 0–1 is proposed for metal foam/paraffin composite material, which covers both diffusion-dominated interstitial heat transfer region (Re ≤ 0.1) and convection-dominated interstitial heat transfer region (0.1 < Re ≤ 1). Finally, the applicability of this correlation in the two-energy equation model for solid–liquid phase change of paraffin in metal foam is validated by comparing the model predicted melting front with that of experimental observations made in this study. It is found that the IHTC correlation proposed in this study can be used in the two-energy equation model for well predicting the phase change process of paraffin in metal foam.

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