An Analytical Derivation of 2-D Conduction Shape Factors

2003 ◽  
Author(s):  
Devashish Shrivastava ◽  
Robert Roemer
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Shape Factor ◽  
Vessel Wall ◽  
Region Of Interest ◽  
Outer Wall ◽  
Tissue Temperature ◽  
Shape Factors ◽  
Dimensional Parameters ◽  
Tissue Matrix

New, improved formulations to evaluate two commonly used 2-D conduction shape factors, standard and average, are presented for a single, circular vessel eccentrically imbedded in a uniformly heated circular tissue matrix in terms of three non-dimensional parameters. The standard conduction shape factor is defined based on the vessel wall temperature and the outer wall temperature. The average conduction shape factor is defined based on the average tissue temperature and the vessel wall temperature. It is shown that both types of 2-D conduction shape factors are functions of the deposited power. The need to use proper expressions to evaluate conduction shape factors to accurately estimate the heat transfer from/to a region of interest when heating is present is stressed.

Poisson Conduction Shape Factors for “Mixed Case” Counter-Current Heat Transfer Applications

2004 ◽  
Author(s):  
Devashish Shrivastava ◽  
Robert B. Roemer
Keyword(s):  
Heat Transfer ◽  
Vessel Wall ◽  
Source Term ◽  
The Other ◽  
Tissue Temperature ◽  
Shape Factors ◽  
Mixed Case ◽  
Boundary Temperature ◽  
Counter Current ◽  
Current Heat

The effects of a source term and geometry on vessel-vessel and vessel-tissue Poisson conduction shape factors (VVPCSFs and VTPCSFs) are studied for uniformly heated, finite, non-insulated tissues for the ‘mixed case’ i.e., when the tissue boundary temperature lies in between the two vessel wall temperatures. In addition, two alternative formulations for the VTPCSFs are compared; while both formulations use the vessel wall temperature, one uses the tissue boundary temperature, and the other the area averaged tissue temperature. Results show that the VVPCSFs are only geometry dependent and do not depend on the applied power or the two vessel wall and tissue boundary temperatures. Conversely, the VTPCSFs are strong functions of these variables.

A Comparison Between 2-D and 3-D Conduction Shape Factors

2003 ◽  
Author(s):  
Devashish Shrivastava ◽  
Robert Roemer
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Cross Section ◽  
Three Dimensional ◽  
Cylindrical Vessel ◽  
Shape Factors ◽  
Axial Conduction ◽  
Power Deposition ◽  
Tissue Matrix

Conduction shape factors are frequently used in a variety of heat transfer applications to evaluate heat transfer from one three-dimensional body to another three-dimensional body. Previous investigators have used conduction shape factors derived using the 2-D cross-section of the 3-D geometries for non-heating conditions as approximations to 3-D conduction shape factors with heating and no-heating present. This paper investigates the suitability of neglecting the axial conduction and power deposition in deriving expressions for conduction shape factors for the case of a single, cylindrical vessel imbedded concentrically in a cylindrical, uniformly heated tissue matrix. It is shown that 1) conduction shape factors are functions of the deposited power and the temperature distribution and 2) the magnitudes of conduction shape factors are affected significantly by axial conduction.

Heat Transfer Characteristics of Aviation Kerosene in Vertical Upward High Flux Tubes at Supercritical Pressure

2016 ◽  
Author(s):  
Jingxiang Chen ◽  
Yachao Song ◽  
Guoqiang Xu ◽  
Jie Wen ◽  
Haiwang Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Mass Flux ◽  
Steel Powder ◽  
Outer Wall ◽  
Powder Coating ◽  
Supercritical Pressure ◽  
Smooth Tube ◽  
High Flux ◽  
Flux Tubes

An experimental investigation on heat transfer peculiarity of kerosene flowing in vertical upward high flux tubes at supercritical pressure is presented. Three inner-sintered steel powder coating tubes (high flux tubes) and one smooth tube are tested under the different super-critical pressure and different mass flux of kerosene in the experiment. Results are found that all three high flux tubes perform much better than smooth tube at the same parameters of the tube and same working conditions. It can be obviously deduced that the outer wall temperature is reduced by the disturbance in the flow field of the sintered metal coating at the inner tube-side, while the reduced mass flux can increase the wall temperature on the contrary. Heat transfer coefficient is found 2.5 times as the smooth tube, yet both too large and too small particle diameters of metal powder sintered on the tube surface can deteriorate heat transfer. Density and viscosity, thermal conductivity of kerosene at different temperatures and pressures under supercritical pressure can be evaluated by using the extended corresponding state principle, which shows good consistency with the experimental results.

Heat Transfer Considerations for Designing FSW Cryogenic Thermal Structures for Aerospace Applications

2008 ◽  
Author(s):  
Michael A. Langerman
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Wall Temperature ◽  
Outer Wall ◽  
Vibration Damping ◽  
Tank Wall ◽  
Transfer Rates ◽  
Friction Stir ◽  
Damping Characteristics ◽  
Cryogenic Tank

Research was conducted to investigate potential structural design configurations for aerospace cryogenic tank wall applications. The primary design considerations included the vibration damping characteristics under various flight loading conditions and the panel wall thermal resistance under different heat loads. The discussion herein is with regards to the thermal issue, specifically the heat transfer rates across two different panel wall designs that have attractive vibration damping characteristics. The heat transfer rates were evaluated analytically and verified with experimental data. One panel is a corrugated, serpentine-layered design fabricated using friction stir welding. The other panel is an “egg-carton” design fabricated using friction stir spot welding. An important thermal consideration for the cryogenic tank wall design is the minimum outer wall temperature attained during ambient storage or prior to launch. Of the two designs considered herein, neither wall provided sufficient thermal resistance to maintain outer wall temperatures above freezing under ambient conditions. One of the wall designs, however, performed somewhat better. It is shown that when configured with an outer layer of thermal plastic coating both designs could maintain an outer wall temperature within design constraints.

scholarly journals Numerical Investigation of the Combustion in an Improved Microcombustion Chamber with Rib

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Hai Chen ◽  
Wei-qiang Liu
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Wall Temperature ◽  
Mass Fraction ◽  
Equivalence Ratio ◽  
Recirculation Zone ◽  
Outer Wall ◽  
Step Length ◽  
Wall Material ◽  
Temperature Level

This study proposes an improved microcombustor with a rectangular rib to improve the temperature level of the combustor wall. Moreover, the OH mass fraction, temperature distribution, and outer wall temperature of the original and improved combustors of premixed hydrogen/air flames are numerically investigated under various inlet velocities and equivalence ratios. Results show that the improved microcombustor enhances heat transfer between the mixture and wall because its recirculation zone is larger than that of the original, thereby resulting in high wall temperature. Conversely, thermal resistance in the horizontal direction increases with upstream and downstream step lengths. Consequently, the outer wall temperature decreases with step length in the improved combustor. A high equivalence ratio (e.g., 0.6) may result in the destruction of the combustor because the wall temperature has exceeded the acceptable temperature of wall material quartz. Therefore, the improved microcombustor is recommended for micro-thermo-photovoltaic systems.

Convection Heat Transfer in Concentric Micro Annular Tubes With Constant Wall Temperature

2009 ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Koichi Suzuki
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Slip Flow ◽  
Outer Wall ◽  
Bulk Temperature ◽  
Inlet Temperature ◽  
Heat Transfer Characteristics ◽  
Constant Wall Temperature ◽  
Transfer Characteristics ◽  
Adiabatic Case

Heat transfer characteristics of gaseous flows in concentric micro annular tubes with constant wall temperature whose temperature is lower or higher than the inlet temperature were numerically investigated. The slip velocity, temperature jump and shear stress work were considered on the slip boundary. The numerical methodology was based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The computations were performed for two thermal cases. This is, the wall temperature was constant at the outer wall and inner wall was adiabatic (Case i) and the wall temperature was constant at the inner wall and the outer wall was adiabatic (Case ii). The stagnation temperature was fixed at 300 K and the computations were done for the wall temperature which ranges from 250 K to 350 K. The outer tube radius ranged from 20 to 150 μm with the radius ratio 0.02, 0.05, 0.1, 0.25 and 0.5 and the ratio of length to hydraulic diameter was 100. The stagnation pressure was chosen in such a way that the exit Mach number ranged from 0.1 to 0.8. The outlet pressure was fixed at the atmospheric pressure. The heat transfer characteristics in concentric micro annular tubes were obtained. The bulk temperature and the total temperature are compared with those of both cooled and heated cases and also compared with those of the simultaneously developing incompressible flow obtained by SIMPLE algorithm. The results show that the compressible slip flow static bulk temperature along the length is different from that of incompressible flow. Therefore heat transfer characteristics of the gaseous flow are different from those of the liquid flow and also have different trends whether the wall temperature is lower or higher than the inlet temperature. A correlation for the prediction of the heat transfer rate of gas slip flow in concentric micro annular tubes is proposed.

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