HEAT TRANSFER INVESTIGATION FOR A MULTILAYER INSULATION SYSTEM VIA RADIATIVE-CONDUCTIVE APPROACH UNDER LOW TEMPERATURE CONDITIONS IN SPACE

2020 ◽  
Vol 19 (2) ◽  
pp. 70
Author(s):  
G. N. Lacerda ◽  
M. F. Curi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Field ◽  
Insulation System ◽  
Final Temperature ◽  
Space Applications ◽  
Conduction Heat Transfer ◽  
Stationary Temperature Field ◽  
Layer Density ◽  
Multilayer Insulation

Thermal insulation is an important area, not restricted to mechanical engineering, but widely studied in environmentalissues, such as global warming and, above all, energy-saving, since controlling the heat flux on microprocessorsthrough temperature control on components in space applications. This work focuses on controlling the temperature incomponents that could not lose or gain so much heat in space, especiallywhen the overall safety of sending satellites onspecific missions is required. To ensure that, Multilayer Insulation (MLI) is used. With fluid mechanics and radiation-conductionheat transfer theory, it was possible to calculate the transient and stationary temperature field and heat flux inMLI. The boundary temperatures are specified at 300K and 4K. The results, from solving the resulting discretized ODE,simulated with fsolve and odeintScipy subroutines in Python, able to solve the equations numerically, were shown. Thedata given by the simulation was able to indicate the impacts of varying the layer density, emissivity of screen, the distancebetween screens and the perforation coefficient in stationary and transient approaches. A way to simulate the performanceof MLI numerically was presented. Modifying emissivity (e) showed variations higher than in the perforation coefficient(ξ). Layer density controls the distance between layers (d ), changing the conduction heat transfer. In the transient casesimulation, it was possible to notice that varying parameters impact in time to reach steady-state and final temperature.

scholarly journals Spatiotemporal distribution of the temperature field inside the thin heated foil during impacting liquid spray

2021 ◽  
Vol 2119 (1) ◽  
pp. 012171
Author(s):  
V V Cheverda ◽  
T G Gigola ◽  
P M Somwanshi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Field ◽  
Heat Transfer Coefficient ◽  
Infrared Image ◽  
Image Sequence ◽  
Spatiotemporal Distribution ◽  
Average Heat Transfer Coefficient ◽  
Average Heat ◽  
Liquid Spray

Abstract The spatiotemporal distribution of the temperature inside a constantan foil during impacting spray is resolved experimentally in the present work. The received infrared image sequence will be used to find the local and average heat transfer coefficient of the foil. In the future, the results obtained will be used to calculate the heat flux in the region of the contact line of each drop.

scholarly journals A Theorem for Finding Maximum Temperature in Wet Grinding

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
J. L. González-Santander ◽  
G. Martín
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Field ◽  
Integral Form ◽  
Stationary Regime ◽  
Time Dependent ◽  
Maximum Temperature ◽  
Theoretical Computation ◽  
Constant Heat ◽  
Workpiece Surface

We consider the solutions found in the literature for heat transfer in surface grinding, assuming a constant heat transfer coefficient for the coolant acting on the workpiece surface and a constant or linear heat flux profiles entering into the workpiece. From the integral form of the time-dependent temperature field reached in the workpiece, assuming the previous conditions, we prove that the maximum temperature always occurs in the stationary regime on the workpiece surface within the contact zone between the wheel and the workpiece. This result assures a very rapid method for the theoretical computation of the maximum temperature.

Measurement of Heat Flux From Fires

Volume 4 ◽  
2004 ◽  
Author(s):  
Cecilia S. Lam ◽  
Alexander L. Brown ◽  
Elizabeth J. Weckman ◽  
Walter Gill
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Unit Area ◽  
Inverse Heat Conduction ◽  
Thermal Impact ◽  
Temperature Changes ◽  
One Dimensional ◽  
Conduction Heat Transfer ◽  
Flux Measurements

Heat flux is an important parameter for characterization of the thermal impact of a fire on its surroundings. However, heat flux cannot be measured directly because it represents the rate of heat transfer to a unit area of surface. Therefore, most heat flux measurements are based on the measurement of temperature changes at or near the surface of interest [1,2]. Some instruments, such as the Gardon gauge [3] and the thermopile [2], measure the temperature difference between a surface and a heat sink. In radiation-dominated environments, this difference in temperature is often assumed to be linearly related to the incident heat flux. Other sensors measure a surface and/or interior temperature and inverse heat conduction methods frequently must be employed to calculate the corresponding heat flux [1,4]. Typical assumptions include one-dimensional conduction heat transfer and negligible heat loss from the surface. The thermal properties of the gauge materials must be known and, since these properties are functions of temperature, the problem often becomes non-linear.

scholarly journals Modelling of Heat Transfer at the Solid to Solid Interface

2016 ◽  
Vol 61 (1) ◽  
pp. 341-346 ◽  
Author(s):  
M. Rywotycki ◽  
Z. Malinowski ◽  
J. Falkus ◽  
K. Sołek ◽  
A. Szajding ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Field ◽  
Objective Function ◽  
Boundary Surface ◽  
Physical Experiment ◽  
Work Piece ◽  
Error Norm ◽  
Solid Interface ◽  
Two Samples

In technological process of steel industry heat transfer is a very important factor. Heat transfer plays an essential role especially in rolling and forging processes. Heat flux between a tool and work piece is a function of temperature, pressure and time. A methodology for the determination of the heat transfer at solid to solid interface has been developed. It involves physical experiment and numerical methods. The first one requires measurements of the temperature variations at specified points in the two samples brought into contact. Samples made of C45 and NC6 steels have been employed in physical experiment. One of the samples was heated to an initial temperature of: 800°C, 1000°C and 1100°C. The second sample has been kept at room temperature. The numerical part makes use of the inverse method for calculating the heat flux and at the interface. The method involves the temperature field simulation in the axially symmetrical samples. The objective function is bulled up as a dimensionless error norm between measured and computed temperatures. The variable metric method is employed in the objective function minimization. The heat transfer coefficient variation in time at the boundary surface is approximated by cubic spline functions. The influence of pressure and temperature on the heat flux has been analysed. The problem has been solved by applying the inverse procedure and finite element method for the temperature field simulations. The self-developed software has been used. The simulation results, along with their analysis, have been presented.

scholarly journals Calculation of Some Integrals Arising in Heat Transfer in Geothermics

2010 ◽  
Vol 2010 ◽  
pp. 1-13 ◽  
Author(s):  
J. L. G. Santander ◽  
P. Castañeda Porras ◽  
J. M. Isidro ◽  
P. Fernández de Córdoba
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Field ◽  
Heat Exchanger ◽  
Ambient Temperature ◽  
Periodic Oscillation ◽  
Field Evaluation ◽  
Borehole Heat Exchanger

We calculate some integrals involved in the temperature field evaluation of the ground, heated by a borehole heat exchanger. This calculation allows a faster computation of that component of the temperature field which involves the periodic oscillation of the ambient temperature or the ambient heat flux.

scholarly journals Heat Transfer Simulations of Sinusoidal Filter

2020 ◽  
Vol 6 (4) ◽  
Author(s):  
Jan Kořínek
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Natural Convection ◽  
Thermal Model ◽  
Air Flow ◽  
Final Temperature ◽  
Ansys Fluent ◽  
Active Cooling ◽  
Heat Transfer Simulation

<p class="TEEAbstract"><span lang="EN-US">This article covers various types of heat transfer simulations of a sinusoidal filter. First part is focused mainly on natural convection case including a detailed geometry thermal model of the sinusoidal filter considering air-flow in surroundings. Further, a comparison of the simplified and detailed geometries and their influences upon the final temperature field is presented. For a selected case of natural convection, comparison of two identical geometries in Ansys Fluent and StarCCM+ is showed. In the last part of this paper, results for the heat transfer simulation of the sinusoidal filter in a distributor case with active cooling are presented.</span></p>

Developments for Copper-Graphite Composite Thermal Cores for PCBs for High-Reliability and High-Temperature RF Systems

2016 ◽  
Vol 2016 (HiTEC) ◽  
pp. 000073-000078
Author(s):  
David L. Saums ◽  
Robert A. Hay
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Thermal Expansion ◽  
Thermal Design ◽  
High Heat Flux ◽  
Space Applications ◽  
Graphite Composite ◽  
Printed Circuit ◽  
Bulk Thermal Conductivity

Summary System designs that have only conduction cooling available, that must operate in harsh or challenging environments, present significant challenges to the system thermal engineer. A second thermal design challenge is continued miniaturization of semiconductor devices and increased functionality per square centimeter of semiconductor die, resulting in continued increases in device heat flux. Elimination of packaging materials allows more efficient heat transfer as thermal resistances from one material to another are reduced or designed out. When possible, concurrent elimination of package materials that have low bulk thermal conductivity and replacement with high thermal conductivity materials will improve heat transfer efficiency. Attachment of the resulting unpackaged semiconductor device can then be made directly to the circuit carrier; however, care must be taken regarding increases in potential for damage or failure due to mismatched coefficient of thermal expansion (CTE). Continuing reductions in die size that result in higher heat flux exacerbate this potential failure mechanism at the die-to-substrate level. This is further worsened in harsh environment (i.e., vibration, shock, high moisture, rapid power cycling) and/or high operating temperature conditions. For aerospace, military, geothermal, and other applications where increasingly high heat flux radio frequency (RF), microwave, and processor semiconductors are attached directly (with solders, silver sintering pastes, or other joining materials) to an organic or ceramic printed circuit card, efficient and rapid heat transfer becomes critical. These are frequently also applications where forced convection (air or liquid) may be unavailable to the system design engineer. One solution for thermal management design problems of this type has traditionally been the incorporation of one or more heavy copper layers within a complex multilayer printed circuit board (PCB). This solution, however, has come under increasing scrutiny in recent years due to concerns for weight (especially in airborne and space applications) and the potential for severe CTE mismatch between semiconductor die materials with relatively low thermal expansion values and the relatively very high value of copper. Therefore, development of CTE-matched alternative materials to replace a heavy copper layer has been a focus for development activities. A suitable selection must, however, have a bulk thermal conductivity that is as close to that of copper as is practicable. Recent developments of a copper-graphite composite material in sheet form that can be employed in standardized PCB manufacturing processes are described in this presentation.

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