Finite-Element Simulation for Thermal Modeling of a Cell in an Adiabatic Calorimeter

This research obtains a mathematical formulation to determine the heat transfer in a transient state, in a calorimeter cell, considering an adiabatic system. The development of the cell was established and the mathematical model was transiently solved, which approximated the physical phenomenon under the cell operation. A numerical method for complex geometries was used to validate performance. The results obtained in the transient heat transfer in a cylinder under boundary and initial conditions were compared using an analytical solution and numerical analysis employing the finite-element method with commercial software. The study from the temperature distribution can afford, selection between a cylindrical and spherical geometry, design criteria that are generated by changing parameters such as dimension, temperature, and working fluids to develop an adiabatic calorimeter to measure the heat capacity in fluids. We show the mathematical solution with its initial and boundary conditions as well as a comparison with a numerical solution for a cylindrical cell with a maximum error from 0.075% in the temperature value, along with a theoretical and numerical analysis for a temperature difference of 1 °C.

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Heat Transfer From an Isothermal Vertical Surface With Adjacent Heated Horizontal Louvers: Numerical Analysis

Journal of Heat Transfer ◽

10.1115/1.1481357 ◽

2002 ◽

Vol 124 (6) ◽

pp. 1072-1077 ◽

Cited By ~ 14

Author(s):

M. Collins ◽

S. J. Harrison ◽

D. Naylor ◽

P. H. Oosthuizen

Keyword(s):

Heat Transfer ◽

Finite Element ◽

Numerical Analysis ◽

Transfer Rate ◽

Radiative Heat ◽

Element Model ◽

Vertical Surface ◽

Two Dimensional ◽

Conjugate Conduction ◽

Steady Laminar

The present study examines the influence of heated, horizontal, and rotatable louvers on the convective and radiative heat transfer from a heated or cooled vertical isothermal surface. The system represents an irradiated Venetian blind adjacent to the indoor surface of a window. Detailed heat transfer results were obtained using a steady, laminar, two-dimensional, conjugate conduction/convection/radiation finite element model for two window temperatures (warm and cool compared to ambient) and irradiation levels, two louver to surface spacings, and three louver angles. The effect of the heated louvers on the heat transfer rate from the surface has been demonstrated.

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Heat Transfer and Thermodynamic Analyses of Some Typical Encapsulated Ice Geometries During Discharging Process

Journal of Heat Transfer ◽

10.1115/1.3111262 ◽

2009 ◽

Vol 131 (8) ◽

Cited By ~ 6

Author(s):

David MacPhee ◽

Ibrahim Dincer

Keyword(s):

Heat Transfer ◽

Viscous Dissipation ◽

Entropy Generation ◽

Flow Rate ◽

Initial Conditions ◽

Spherical Geometry ◽

Heat Transfer Fluid ◽

Slab Geometry ◽

Flow Parameters ◽

The Difference

This study deals with the process of melting in some typical encapsulated ice thermal energy storage (TES) geometries. Cylindrical and slab capsules are compared with spherical capsules when subjected to a flowing heat transfer fluid (HTF). The effect of inlet HTF temperature and flow rate as well as the reference temperatures are investigated, and the resulting solidification and melting times, energy efficiencies, and exergy efficiencies are documented. Using ANSYS GAMBIT and FLUENT 6.0 softwares, all geometries are created, and the appropriate boundary and initial conditions are selected for the finite volume solver to proceed. Sufficient flow parameters are monitored during transient solutions to enable the calculation of all energy and exergy efficiencies. The energetically most efficient geometric scenario is obtained for the slab geometry, while the spherical geometry exergetically achieves the highest efficiencies. The difference between the two results is mainly through the accounting of entropy generation and exergy destroyed, and the largest mode of thermal exergy loss is found to be through entropy generation resulting from heat transfer accompanying phase change, although viscous dissipation is included in the analysis. All efficiency values tend to increase with decreasing HTF flow rate, but exergetically the best scenario appears to be for the spherical capsules with low inlet HTF temperature. Energy efficiency values are all well over 99%, while the exergy efficiency values range from around 72% to 84%, respectively. The results indicate that energy analyses, while able to predict viscous dissipation losses effectively, cannot correctly quantify losses inherent in cold TES systems, and in some instances predict higher than normal efficiencies and inaccurate optimal parameters when compared with exergy analyses.

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