Parametric height influence analysis on thermal radiation and convection applied to real ovens

2021 ◽  
pp. 095440892110375
Author(s):  
Sílvio Aparecido Verdério Júnior ◽  
Vicente Luiz Scalon ◽  
Santiago del Rio Oliveira ◽  
Elson Avallone ◽  
Paulo César Mioralli ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Numerical Models ◽  
Radiation Heat Transfer ◽  
Geometric Optimization ◽  
Operating Conditions ◽  
High Productivity ◽  
Order Of Magnitude ◽  
Lower Height ◽  
Heat Exchanges

Due to their greater flexibility in heating and high productivity, continuous tunnel-type ovens have become the best option for industrial processes. The geometric optimization of ovens to better take advantage of the heat transfer mechanisms by convection and thermal radiation is increasingly researched; with the search for designs that combine lower fuel consumption, greater efficiency and competitiveness, and lower costs. In this sense, this work studied the influence of height on heat exchanges by radiation and convection and other flow parameters to define the best geometric height for the real oven under study. From the dimensions and real operating conditions of continuous tunnel-type ovens were built five numerical models of parametric variation, which were simulated with the free and open-source software OpenFOAM®. The turbulent forced convection regime was characterized in all models. The use of greater heights in the ovens increased and intensified the recirculation regions, reduced the rates of heat transfer by thermal radiation, and reduced the losses of heat by convection. The order of magnitude of heat exchanges by radiation proved to be much higher than heat exchanges by convection, confirming the results of the main references in the technical-scientific literature. It was concluded that the use of ovens with a lower height provides significant increases in the thermal radiation heat transfer rates.

Analysis to Reduce Thermal Stress in Oxide Single Crystal During Czochralski Growth

2004 ◽  
Author(s):  
Shigeki Hirasawa ◽  
Hiroyuki Ishibashi ◽  
Kazuhisa Kurashige ◽  
Akihiro Gunji
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Temperature Distribution ◽  
Thermal Radiation ◽  
Single Crystal ◽  
Radiation Heat Transfer ◽  
Heat Transfer Analysis ◽  
Czochralski Growth ◽  
Radiation Heat ◽  
Radial Temperature

Temperature distributions and thermal stress distributions in a semi-transparent GSO crystal during Czochralski (CZ) single crystal growth were numerically investigated by thermal radiation heat transfer analysis and anisotropy stress analysis. As GSO has special optical properties, such as semi-transparency at a wavelength shorter than 4.5 μm, thermal radiation heat transfer was calculated by the Monte Carlo method. These calculations showed that thermal stress is caused by the radial temperature distribution on the outside of the upper part of the crystal. To reduce this temperature distribution, the following three manufacturing conditions were found to be effective: use a sharp taper angle of the crystal, install a lid to the top of the insulator, and install a ring around the tapered part of the crystal.

scholarly journals Experimental studies and mathematical modeling on the effects of rapid airflow and baking temperature during baking

2020 ◽  
pp. 469
Author(s):  
Mazidah Mior Zakuan Azmi ◽  
Anvarjon Ahmedov ◽  
Farah Saleena Taip
Keyword(s):  
Heat Transfer ◽  
Volume Expansion ◽  
Numerical Models ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Transfer Model ◽  
Temperature Profiles ◽  
Convection Oven ◽  
Baking Process ◽  
Cake Baking

Rapid airflow in oven will influence the heat transfer in baking process therefore the purpose of this study is to experimentally and numerically investigate the effects of operating conditions on the heat transfer mechanism and volume expansion during baking. Cakes are baked in an air fryer and convection oven with constant speed 5.11 m/s and 0.88 m/s respectively at 150, 160, 170 °C in different baking times. A heat transfer model was defined to describe the influence of baking temperature on internal cake temperature by Fourier’s law. It was observed that the presence of rapid airflow (air fryer) and increment in oven temperature yielded an increase in volume expansion but produced a less moist product. Cakes baked in the presence of rapid airflow at 150 °C were moister but with little volume expansion in the cakes compared to convection oven-baked cakes. Significant correlation between the numerical models with experimental temperature profiles were recorded during complete cake baking process.

A CFD Assessment of Engine Core Zone Casing Heat Transfer

2019 ◽  
Author(s):  
Zixiang Sun ◽  
Nicholas J. Hills ◽  
Richard Scott
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Convection Heat Transfer ◽  
Aircraft Engine ◽  
Operating Conditions ◽  
Steady Flows ◽  
Radiation Heat ◽  
Core Zone ◽  
The Public ◽  
The Core

Abstract A systematic CFD investigation was conducted to assess the core zone (CZ) casing heat transfer of a large civil aircraft engine. Three key engine operating conditions, maximum takeoff (MTO), cruise (CRZ) and ground idle (GI) were analyzed. Steady flows were assumed. Turbulence was simulated using the realizable k-epsilon model in conjunction with the scalable wall function. Buoyancy effect was taken into account. Radiation was calculated using the discrete ordinate (DO) model. It was shown that the forced convection heat transfer dominates in most of the casing surface in the core zone, and radiation is of second importance in general. However, in some areas where both convection and radiation heat transfer are weak but the latter is relatively greater in magnitude than the former, radiation heat transfer could thus become dominant. In addition, the overall impact of radiation on casing heat transfer increases from MTO to CRZ and GI conditions, as the strength of engine load decreases. The overall effect of buoyancy on casing heat transfer is small, but could be noticeable in some local areas where flow velocity is low. The insight into heat transfer features on the engine core zone casing supported by quantified CFD evidences is the first in the public domain, as far as authors are aware.

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