A simplified analytical model for radiation dominated ignition of solid fuels exposed to multiple non-steady heat fluxes

2022 ◽  
Vol 237 ◽  
pp. 111866
Author(s):  
Roberto Parot ◽  
José Ignacio Rivera ◽  
Pedro Reszka ◽  
José Luis Torero ◽  
Andrés Fuentes
Keyword(s):  
Analytical Model ◽  
Heat Fluxes ◽  
Solid Fuels ◽  
Steady Heat

Analytical Model Quantifying the Net Coolant Flow Rate to a Microstructured Copper Surface validated with Two-Phase PIV Measurements

2021 ◽  
Author(s):  
Matt Harrison ◽  
Joshua Gess
Keyword(s):  
Heat Transfer ◽  
Analytical Model ◽  
Flow Rate ◽  
Circular Disk ◽  
Nucleate Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Two Phase

Abstract Using Particle Image Velocimetry (PIV), the amount of fluid required to sustain nucleate boiling was quantified to a microstructured copper circular disk. Having prepared the disk with preferential nucleation sites, an analytical model of the net coolant flow rate requirements to a single site has been produced and validated against experimental data. The model assumes that there are three primary phenomena contributing to the coolant flow rate requirements at the boiling surface; radial growth of vapor throughout incipience to departure, bubble rise, and natural convection around the periphery. The total mass flowrate is the sum of these contributing portions. The model accurately predicts the quenching fluid flow rate at low and high heat fluxes with 4% and 30% error of the measured value respectively. For the microstructured surface examined in this study, coolant flow rate requirements ranged from 0.1 to 0.16 kg/sec for a range of heat fluxes from 5.5 to 11.0 W/cm2. Under subcooled conditions, the coolant flow rate requirements plummeted to a nearly negligible value due to domination of transient conduction as the primary heat transfer mechanism at the liquid/vapor/surface interface. PIV and the validated analytical model could be used as a test standard where the amount of coolant the surface needs in relation to its heat transfer coefficient or thermal resistance is a benchmark for the efficacy of a standard surface or boiling enhancement coating/surface structure.

Mechanical Behavior of Bolted Joints Under Steady Heat Conduction

1994 ◽  
Vol 116 (1) ◽  
pp. 42-48 ◽  
Author(s):  
H. Kumano ◽  
T. Sawa ◽  
T. Hirose
Keyword(s):  
Heat Conduction ◽  
Mechanical Behavior ◽  
Maximum Stress ◽  
Heat Fluxes ◽  
Bolted Joints ◽  
Electric Heater ◽  
Thick Plates ◽  
Thermal Changes ◽  
Steady Heat Conduction ◽  
Steady Heat

Bolted joints in heat exchangers, cylinder heads in combustion engines, and so on are subjected to heat fluxes. It is necessary to examine the mechanical behavior of such bolted joints under thermal changes in order to establish an optimal design. This paper deals with mechanical behavior of bolted joints, in which two hollow cylinders and two rectangular thick plates made of aluminum are fastened at room temperature by a bolt and nut made of steel, and are subjected to thermal changes or steady heat conduction. Temperature distributions of the joints are analyzed using the finite difference method. Then, methods for estimating an increment in axial bolt force and a maximum stress produced in the bolts are proposed. In the experiments, the aforementioned bolted joints are put in a furnace. Furthermore, the rectangular thick plates fastened by a bolt and nut are heated by an electric heater. Then, the temperatures on the surfaces of the clamped parts and the bolts are measured with thermocouples. The increase in axial bolt force and the maximum stress produced in the bolts under steady heat conduction or thermal changes are measured. The analytical results are in fairly good agreement with the experimental ones.

scholarly journals Development of an Analytical Model to Determine the Heat Fluxes to a Structural Element Due to a Travelling Fire

2021 ◽  
Vol 11 (19) ◽  
pp. 9263
Author(s):  
Marion Charlier ◽  
Jean-Marc Franssen ◽  
Fabien Dumont ◽  
Ali Nadjai ◽  
Olivier Vassart
Keyword(s):  
Analytical Model ◽  
Fire Test ◽  
Fire Spread ◽  
Heat Fluxes ◽  
Thermal Impact ◽  
Structural Element ◽  
Transient Heating ◽  
Simple Manner ◽  
Basic Assumptions ◽  
Surrounding Structure

The term “travelling fire” is used to label fires which burn locally and move across the floor over a period of time in large compartments. Through experimental and numerical campaigns and while observing the tragic travelling fire events, it became clear that such fires imply a transient heating of the surrounding structure. The necessity to better characterize the thermal impact generated on the structure by a travelling fire motivated the development of an analytical model allowing to capture, in a simple manner, the multidimensional transient heating of a structure considering the effect of the ventilation. This paper first presents the basic assumptions of a new analytical model which is based on the virtual solid flame concept; a comparison of the steel temperatures measured during a travelling fire test in a steel-framed building with the ones obtained analytically is then presented. The limitations inherent to the analyticity of the model are also discussed. This paper suggests that the developed analytical model can allow for both an acceptable representation of the travelling fire in terms of fire spread and steel temperatures while not being computationally demanding, making it potentially desirable for pre-design.

scholarly journals An Analytical Model for Natural Convection in a Rectangular Enclosure with Differentially Heated Vertical Walls

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3220
Author(s):  
Alberto Fichera ◽  
Manuel Marcoux ◽  
Arturo Pagano ◽  
Rosaria Volpe
Keyword(s):  
Natural Convection ◽  
Aspect Ratio ◽  
Analytical Model ◽  
Numerical Solutions ◽  
Heat Fluxes ◽  
Rectangular Enclosure ◽  
Nusselt Numbers ◽  
Pressure Fields ◽  
Vertical Walls ◽  
Temperature And Velocity Fields

This paper proposes an analytical model for natural convection in a closed rectangular enclosure filled by a fluid, with imposed heat fluxes at the vertical walls and adiabatic horizontal walls. The analytical model offers a simplified, but easy to handle, description of the temperature and velocity fields. The predicted temperature, velocity, and pressure fields are shown to be in agreement with those obtained from a reliable numerical model. The Nusselt numbers for both the analytical and numerical solutions are then calculated and compared, varying both the aspect ratio of the enclosure and the Rayleigh number. Based on the comparisons, it is possible to assess the dependence of the reliability of the analytical model on the aspect ratio of the enclosure, showing that the prediction error rapidly decreases with the increase of the enclosure slenderness.

An Analytical Model for Prediction of Tool Temperature Fields during Continuous and Interrupted Cutting

1994 ◽  
Vol 116 (2) ◽  
pp. 135-143 ◽  
Author(s):  
R. Radulescu ◽  
S. G. Kapoor
Keyword(s):  
Analytical Model ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Time History ◽  
Heat Fluxes ◽  
Temperature Fields ◽  
Heat Transfer Analysis ◽  
Interface Temperature ◽  
Tool Temperature ◽  
Interrupted Cutting

An analytical model for prediction of tool temperature fields in metal cutting processes is developed. The model can be applied to any continuous or interrupted three-dimensional cutting process. To accurately represent the heating and cooling cycles encountered during interrupted cutting, the analysis predicts time dependent heat fluxes into the cutting tool. A time history of this heat flux is obtained by performing an energy balance on the chip formation zone. The variation with time of the tool temperature fields is determined from a heat transfer analysis with prescribed heat generation rate. The analysis requires the cutting forces as inputs. The model tool-chip interface temperatures agree well with the experimental tests reported in the literature, for all cutting conditions and work materials investigated. The results indicate that the tool-chip interface temperature increases with cutting speed during both continuous and interrupted cutting.

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