scholarly journals Defining patterns of heat transfer through the fire-protected fabric to wood

2021 ◽  
Vol 6 (10 (114)) ◽  
pp. 49-56
Author(s):  
Yuriy Tsapko ◽  
Аleksii Tsapko ◽  
Olga Bondarenko
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Heated Surface ◽  
Fire Retardant ◽  
Thermal Action ◽  
Insulating Layer ◽  
A Value ◽  
Flow Through ◽  
Insulating Properties ◽  
Protective Screen

Under the thermal action on wood when applying a protective screen made from fire-retardant fabric, the process of temperature transfer is natural. It has been proven that depending on the thermal properties of the coating of fire-proof fabric, this could lead to varying degrees of heat transfer. Therefore, it becomes necessary to study the conditions for establishing low thermal conductivity and establishing a mechanism that inhibits heat transfer to wood. Given this, a mathematical model has been built of the process of heat transfer to wood when it is protected by a screen made of fire-proof fabric. According to the experimental data on determining the temperature on the non-heated surface of the fabric and the resulting dependences, the density of the heat flow transmitted to wood through fire-proof fabric was determined. Thus, with an increase in the temperature, the density of the heat flow to the surface of the wood through a protective screen made of fire-proof protected coating based on "Firewall-Attic" increases to a value above 16 kW/m2, which is not sufficient for ignition of wood. Instead, the density of the heat flow through the protective screen of fire-proof fabric protected by the "Firewall-Wood"-based coating did not exceed 14 kW/m2. This makes it possible to argue about the compliance of the detected mechanism of formation of heat-insulating properties in the protection of wood and the practical attractiveness of the proposed technological solutions. Thus, the peculiarities of inhibition of the process of heat transfer to wood through a protective screen made of fire-proof fabric under the action of a radiation panel imply the formation of a heat-insulating layer of coked cellular material when decomposing the coating. Thus, on the surface of the fire-proof fabric, a temperature above 280 °C was achieved and, on an untreated surface of the fabric, it did not exceed 220 °C, which is insufficient for the ignition of wood.

scholarly journals A study of sensing heat flow through thermal walls by using thermoelectric module

2015 ◽  
Vol 19 (5) ◽  
pp. 1497-1505 ◽  
Author(s):  
Noppawit Sippawit ◽  
Thananchai Leephakpreeda
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Thermoelectric Module ◽  
Plane Wall ◽  
Thermal Engineering ◽  
Transfer Coefficients ◽  
Thermoelectric Effects ◽  
Flow Through ◽  
Flow Detection ◽  
Engineering Practices

Demands on heat flow detection at a plane wall via a thermoelectric module have drawn researchers? attention to quantitative understanding in order to properly implement the thermoelectric module in thermal engineering practices. Basic mathematical models of both heat transfer through a plane wall and thermoelectric effects are numerically solved to represent genuine behaviors of heat flow detection by mounting a thermoelectric module at a plane wall. The heat transfer through the plane wall is expected to be detected. It is intriguing from simulation results that the heat rejected at the plane wall is identical to the heat absorbed by the thermoelectric module when the area of the plane wall is the same as that of the thermoelectric module. Furthermore, both the area sizes of the plane walls and the convective heat transfer coefficients at the wall influence amount of the heat absorbed by the thermoelectric module. Those observational data are modeled for development of sensing heat flow through a plane wall by a thermoelectric module in practical uses.

The Reynolds Analogy Applied to a Cylinder Rotating in Air

1954 ◽  
Vol 58 (519) ◽  
pp. 205-208 ◽  
Author(s):  
Y. R. Mayhew
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Heat Flow ◽  
Solid Surface ◽  
Fluid Flows ◽  
Flat Plates ◽  
Reynolds Analogy ◽  
Transfer Data ◽  
Turbulent Fluid ◽  
Flow Through

When a turbulent fluid flows past a solid surface whose temperature differs from that of the fluid, the shear stress at the surface and the heat flow from it can be related by means of the Reynolds analogy. This analogy has been improved by Prandtl, Taylor, von Kármán and others, and its validity has been tested for flow through tubes and past flat plates by several investigators. In this note the analogy is checked against shear stress data and heat transfer data for a cylinder rotating in “still” air, when the flow is turbulent.

Performance Indicators for Steady-State Heat Transfer Through Fin Assemblies

1996 ◽  
Vol 118 (2) ◽  
pp. 310-316 ◽  
Author(s):  
A. S. Wood ◽  
G. E. Tupholme ◽  
M. I. H. Bhatti ◽  
P. J. Heggs
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Heat Flow ◽  
Performance Indicators ◽  
Physical Parameters ◽  
State Heat ◽  
Extended Surface ◽  
Flow Through ◽  
Steady State Heat ◽  
Steady State Heat Transfer

A comparative study is presented of several models describing steady-state heat flow through an assembly consisting of a primary surface (wall) and attached extended surface (fin). Attention is focused on the validity of four performance indicators. The work shows that the augmentation factor is the only indicator capable of correctly predicting the behavioral trends of the rate of heat flow through the assembly as the influencing physical parameters are varied.

scholarly journals Thermal Step Response of N-Layer Composite Walls—Accurate Approximative Formulas

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Carl-Eric Hagentoft ◽  
Simon Pallin
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Flow ◽  
Numerical Solutions ◽  
Step Change ◽  
Step Response ◽  
Surface Boundary ◽  
Multilayer Composites ◽  
Flow Through ◽  
Multiple Variables

Abstract For many industrial applications, heat flow through composites relates directly to energy usage and thus is of highest interest. For multilayer composites, the heat flow is a result of multiple variables, such as the temperature gradient over the surface boundaries and each material's thermal conductivity, specific heat, and thickness. In addition, the transient heat flux also depends on how the materials are aligned together. The heat flow through composites can be estimated using advanced computer simulations for applied heat transfer. Although these tools are powerful, they are also time consuming. Therefore, approximations that allow the estimation of heat flow through composites can be very useful. This paper presents approximations to solve transient heat transfer in multilayer composites, with and without an interior surface resistance. Since the energy use for various applications relates to the heat transferred at the surface boundary, the main focus of this paper is to define approximate solutions for interior heat flow. In other words, these approximations are found by applying a unit step change in temperature on one side of a composite and then in real-time emulating the surface heat flux on the opposite side from which the step change occurs. The approximations are presented based on lumped analyses and Laplace network solutions and are validated against analytical and numerical solutions.

scholarly journals The possibilities of application of radiant wall cooling in existing buildings as a part of their retrofit

2019 ◽  
Vol 111 ◽  
pp. 03008
Author(s):  
Michal Krajčík ◽  
Ondřej Šikula
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Numerical Simulations ◽  
Environmental Impacts ◽  
Thermal Response ◽  
Cooling Capacity ◽  
Existing Buildings ◽  
Negative Effects ◽  
Flow Through ◽  
Moderate Climate

In the following years and decades the increase in cooling capacity will put tremendous pressure on the energy infrastructure and severely increase the environmental impacts. In a moderate climate and well thermally insulated buildings like, e.g., in Europe, installation of low-exergy radiant systems could help alleviate these negative effects. Wall systems may be especially suitable for installation in existing buildings, however, their possible applications in buildings retrofit have not been fully explored. We therefore investigate the possible applications of wall cooling in existing buildings by numerical simulations of two-dimension heat flow through a wall fragment. Three wall systems are proposed and compared in terms of thermal response and heat transfer. The effect of various parameters is investigated to facilitate the design of the wall systems.

The Effect of Nonuniform Interfacial Pressures on the Heat Transfer in Bolted and Riveted Joints

1990 ◽  
Vol 112 (3) ◽  
pp. 174-182 ◽  
Author(s):  
C. V. Madhusudana ◽  
G. P. Peterson ◽  
L. S. Fletcher
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Stress Distribution ◽  
Contact Zone ◽  
Plate Thickness ◽  
Interfacial Area ◽  
Interfacial Pressure ◽  
Riveted Joints ◽  
Flow Through ◽  
Contact Spots

In bolted or riveted joints where the interfacial pressure is not uniform, the total resistance to heat flow in a vacuum is the result of two separate components: the microscopic resistance, which arises due to the constraint of the heat flow through the actual microscopic contact spots, and the macroscopic resistance, which exists because the contact zone, over which these microscopic contact spots are located, is only a fraction of the total interfacial area. Presented here is a review of the recent literature addressing the interfacial pressure distribution and the size of the contact zone, in so far as they affect the heat transfer at these interfaces. A survey of the experimental work on contact pressure and the associated heat transfer in bolted joints is presented, along with the size of the actual contact zone which was identified as an important parameter affecting both the microscopic and the macroscopic resistances. An analysis is performed in which it is formally shown that the exact form of the stress distribution within the contact zone is immaterial for the computation of the total microscopic conductance if the available theoretical results for local solid spot conductance are used. If experimental correlations for local solid spot conductance are used, however, the computed total microscopic conductances may differ about 5 to 10 percent, depending on the type of stress distribution chosen. It is also shown that, for a given load, the total microscopic conductance may be increased by increasing the loading radius and/or the plate thickness.

Measurement of Thermal Conduction Through Polymeric Nanowires With the Dual Cantilever Technique

2014 ◽  
Author(s):  
Carlo Canetta ◽  
Arvind Narayanaswamy
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Flow ◽  
Thermal Conduction ◽  
Thermal Conductance ◽  
High Sensitivity ◽  
Conductance Measurement ◽  
Electrospinning Technique ◽  
Flow Through ◽  
Thermal Stimuli

Bi–material microcantilevers, with their high sensitivity to thermal stimuli, are ideally suited sensors for investigating nanoscale heat transfer. We have designed and fabricated low thermal conductance bi–material microcantilevers by minimizing their width and thickness. Using such cantilevers, we have demonstrated heat flux resolution of less than 1 picowatt. A pair of such cantilevers is proposed as a configuration for measuring thermal conductance of a nanostructure suspended between the two. In this technique, two lasers are focused, one on each cantilever. One laser is modulated to vary the temperature at the end of one cantilever, while the second laser senses variation in heat flow through the second cantilever due to thermal conduction along the nanowire. We have determined the resolution of such a conductance measurement by measuring the background conductance between the two cantilevers in the absence of a nanostructure suspended between them. The background conductance is due to other pathways for heat transfer between the cantilevers besides nanostructure conductance. We have measured the background conductance to be as low as 0.05 nWK−1. We present measurements of thermal conductance of polystyrene nanowires performed using the dual cantilever technique. The nanowires are fabricated via electrospinning technique with diameters varying in the range of 150–300 nm. While the polystyrene nanowires present a demonstration of the cantilever technique for measuring thermal conductance, the technique we have developed can be extended to other types of nanostructures so long as they can be suspended between two cantilever ends.

scholarly journals The application of Osborne Reynolds' theory of heat transfer to flow through a pipe

1930 ◽  
Vol 129 (809) ◽  
pp. 25-30 ◽  
Keyword(s):  
Heat Transfer ◽  
Heated Surface ◽  
Local Pressure ◽  
Average Distribution ◽  
Complete Series ◽  
Flow Through ◽  
The Difference ◽  
Hot Surface ◽  
Essential Assumption ◽  
Complete Analogy

In a recent paper Messrs. Eagle and Ferguson describe a very complete series of measurements of the conditions of heat transfer between a brass tube and water flowing through it. They base the discussion of their results on Osborne Reynolds theory of heat transfer according to which there is a complete analogy between the transfer of heat and momentum so that if a hot sheet is moved edgewise through a fluid the distributions of temperature and momentum in the water are identical. The assumption underlying the theory is that any portion of the fluid which comes sufficiently near the heated surface to be moved forward with the speed of the hot surface is also heated to the temperature of that surface, or, alternatively, a portion which is moved forward at a fraction, β, times the speed of the plate is also heated through a temperature equal to β times the difference in temperature between the plate and the fluid. In this manner Reynolds’ theoretical coefficient of heat transfer, κ R , may be calculated. The observed heat transfer coefficient is represented by Messrs. Eagle and Ferguson as κ 0 and their results are expressed in the form F = κ R /κ 0 where F is a fraction determined under a variety of different conditions of experiment. This crude form of Reynolds’ theory suffers from two possible main sources of error, (A) the heated surface may raise the velocity of any portion of the fluid near it through a greater fraction of its own velocity than it raises the temperature expressed as a fraction of its own temperature, the initial temperature of the fluid being taken as zero. This might be expected to give rise to large errors in cases where the thermal conductivity is specially low. (B) The effect of local pressure differences which are inherent in all turbulent motion and alter the momentum of the fluid at any point without altering its temperature is neglected. The essential assumption in Reynolds’ theory is that these local pressure differences have no effect on the average distribution of velocity.

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