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Conduction, thermal composite walls

Determination of thermal conductivity of composite wall apparatus... [Pg.458]

Figure 9.6 shows a composite wall made up of three materials with thermal conductivities k, k2, and k2, with thicknesses as shown and with the temperatures T1, T2, T2, and jT4 at the faces. Applying equation 9.12 to each section in turn, and noting that the same quantity of heat Q must pass through each area A ... [Pg.390]

Related Calculations. The method described for calculating the overall heat-transfer coefficient is also used to calculate the overall resistance to conduction of heat through a composite wall containing materials in series that have different thicknesses and thermal conductivities. For this case, each individual heat-transfer coefficient is equal to the thermal conductivity of a particular material divided by its thickness. The amount of heat transferred by conduction can then be determined from the formula... [Pg.288]

Example 2.4 Estimation of heat flow through a composite wall with constant thermal conductivities A pipe with an outside diameter of 10 cm and a length of 110 m is carrying hot fluid. The pipe is insulated with 0.5 cm thick silica foam and 10 cm thick fiberglass. The pipe wall is at 120°C and the outside surface of the fiberglass is at 30°C. Estimate the heat flow in the radial direction of the pipe. The thermal conductivities of silica foam and fiberglass are 0.055 and 0.0485 W/(m K), respectively. [Pg.64]

Conduction with Resistances in Series A steady-state temperature profile in a planar composite wall, with three constant thermal conductivities and no source terms, is shown in Fig. 5-3a. The corresponding thermal circuit is given in Fig. 5-3b. The rate of heat transfer through each of the layers is the same. The total resistance is the sum of the individual resistances shown in Fig. 5-3b ... [Pg.5]

FIG. 5-3 Steady-state temperature profile in a composite wall with constant thermal conductivities k kg, and kc and no energy sources in the wall. The thermal circuit is shown in (b). The total resistance is the sum of the three resistances shown. [Pg.5]

In practice we often encounter plane walls that consist of several layers of different materials. The tbermal resistance concept can still be used to detennine the rate of steady heat transfer through such composite walls. As you may have already guessed, this is done by simply notiifg that the conduction resistance of each wall i.s IJkA connected in series, and using the electrical analogy. That is, by dividing the temperature difference between two surfaces at known temperatures by the total thermal resistance between them. [Pg.156]

Conduction of Heat 169 Thermal Conductivity 169 Hollow linder 170 Composite Walls 170 Fluid Films 170... [Pg.769]

Consider a composite wall made of three parallel slabs of cross-sectional area A (Fig. 2.3), The thickness and thermal conductivity of these slabs are 13 and k, respectively. Heat is transferred from a hot fluid at temperature 7 through this composite wall to a cold fluid at temperature To- Coefficients of heat transfer on the hot and cold sides are hi and ho, respectively. [Pg.45]

Expanded polystyrene foam (EPS) has different applications, because of its physical form (beads) and properties (higher permeability to water and less effective adhesion to facing materials than polyurethane). The expansion gases, pentane and steam, escape fairly rapidly from the foam, so the thermal conductivity of the foam filled with air is about twice that of the best polyurethane foam—a 50 mm thick slab of foam has a U-value of 0.5-0.6 Wm K . EPS mouldings can be used as shutters (formwork) for pouring concrete in a composite wall. The two EPS layers are connected at intervals to fix the thickness of the concrete. Extruded polystyrene foam (XPS) is used in plank form for insulation imder the concrete floor of houses, and in roofing panels. [Pg.349]

From these we can also define the thermal conductance through the composite wall as [7 = 1 /RA, that is, the rate of heat transfer per degree of temperature drop per square meter, from which follows the heat transfer as... [Pg.183]

Example 2.4 Estimation of heat flow through a composite wall with constant thermal conductivities A pipe... [Pg.64]

T.T. Lie determined in 1972 the thermal conductivity of clay bricks with densities between 700 and 2100 kg/m His research showed that the thermal conductivity increases linearly up to 100 C. Commonly used bricks have densities between 1600 and 2000 kg/mL The thermal conductivity of the wall is influenced by the composition of the pieces and the structure of its components. [Pg.451]

Thermal Conductivity of Laminar Composites. In the case of laminar composites or layered materials (cf. Figure 1.74), the thermal conductance can be modeled as heat flow through plane walls in a series, as shown in Figure 4.36. At steady state, the heat flux through each wall in the x direction must be the same, qx, resulting in a different temperature gradient across each wall. Equation (4.2) then becomes... [Pg.335]

In curing of epoxy-amine compositions, especially in casting large-size thick-wall products, the process — due to a high thermal effect and low thermal conductivity — frequently passes into the nonisothermal mode (quasiadiabatic, or reaction front propagation) so that it becomes practically uncontrollable. [Pg.139]


See other pages where Conduction, thermal composite walls is mentioned: [Pg.484]    [Pg.164]    [Pg.79]    [Pg.252]    [Pg.193]    [Pg.200]    [Pg.201]    [Pg.80]    [Pg.107]    [Pg.430]    [Pg.816]    [Pg.57]    [Pg.2078]    [Pg.177]    [Pg.109]    [Pg.568]    [Pg.168]    [Pg.78]    [Pg.432]    [Pg.273]   
See also in sourсe #XX -- [ Pg.170 ]

See also in sourсe #XX -- [ Pg.166 ]

See also in sourсe #XX -- [ Pg.170 ]

See also in sourсe #XX -- [ Pg.170 ]

See also in sourсe #XX -- [ Pg.170 ]




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Estimation of heat flow through a composite wall with constant thermal conductivities

Thermal conductivity composites

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