Heat insulation exterior walls

The exterior walls, the basin divider partitions, and the heat-exchanger flume are constructed of concrete block on poured concrete footers. The basin was made watertight by placing prefabricated asphalt matting directly on the soil and on the inside surfaces of the walls of the still. Two-inch-thick Foamglass insulation was placed around the perimeter walls so that the edge heat losses would be comparable to those of much larger stills. 

An exterior wall of a house may be approximated by a 4-in layer of common brick [A = 0.7 W/m C] followed by a 1.5-in layer of gypsum plaster [k = 0.48 W/m °C]. What thickness of loosely packed rock-wool insulation [A = 0.065 W/m °C] should be added to reduce the heat loss (or gain) through the wall by 80 percent... 

Example 5.11 The electrically heated oven in Fig. 5.63a is used for the surface treatment of thin, square metal plates that are covered on both sides. The oven has a square base of side length a = 1.50 m. The radiation emitting surface of the heating elements has emissivity s = 0.85 their distance from the metal plate is b = 0.25 m. 12.5 kW power is supplied to each of the two rows of heating elements being well insulated against the exterior. The non-insulated side walls of the oven have emissivity = 0.70. At steady-state the surface temperature of the heating elements reaches 750 K. Determine the temperature of the side walls and the temperature of the covered metal plate. 

Heat losses in residential buildings occur primarily via convection from the roof ( 25-35%) followed by air leakage and walls ( 15-25% each). Adequate insulation in roof and exterior walls is therefore a significant energy-saving investment. Table 5.7 compares thermal conductivity and environmental merits of different insulation materials (Dewick and Miozzo, 2002). The insulation efficiency is typically... 

Heat insulation of exterior walls of buildings can be done by a variety of methods and rigid EPS foam is well suited for most of them, i.e., application of reinforced plaster renderings over EPS board, or use of EPS insulation board and a coating of fabric-reinforced plaster. A coating of EPS foam (2 m of 10 cm thick) (which is equivalent to 10 litres of petroleum) can help to save 1200 litres of heating oil over a 50 year span. 

One of the two vertical walls terminating a battery of coke ovens or a bench of gas retorts it is generally constructed of refractory bricks and heat-insulating bricks with an exterior facing of building bricks. 

Btu/(hr) (ft2)(°F/ft) i = inside wall pipe o = outside wall surface of pipe Heat loss from fluid inside pipe through exterior insulation to outside air. Combined convection and radiation ... 

The heat loss through a firebrick furnace wall 0.2 in thick is to be reduced by addition of a layer of insulating brick to the outside. What is the thickness of insulating brick necessary to reduce the heat loss to 400 W/m2 The inside furnace wall temperature, is 1573 K. the ambient air adjacent to the furnace exterior is at 293 K and the natural convection heat transfer coefficient at the exterior surface is given by h S.OAT11 23 W/in2 K, where AT is the temperature difference between the surface and the ambient air,... 

To reduce heat losses, the exterior flat wall of a furnace is to be insulated. The data presented to you are... 

In order to increase the thermal resistance of a typical exterior fimne wall, such as the one shown in Example 11.11, it is customary to use 2 X 6 studs instead of 2X4 studs to allow for placement of more insulation within the wall cavity. A typical exterior (2X6) frame wall of a house consists of the materials shown in the accompanying figure. Assume an inside room temperature of 68°F and an outside air temperature of 20°F writh an exposed area of 150 ft. Determine the heat loss through this wall. 

Temperature differential or cold wall effect It is not imcommon to see blistering in a vessel at the uninsulated areas or areas that are heat sinks. The blistering caused by this temperature differential (AT) between the exterior and interior areas of the metal may be partly overcome by force curing to drive off the residual solvents in the film. However, the real solution may be to insulate the exterior surface in order to reduce the temperature differential AT. 

Microsphere Insulation. Good thermal-insulation performance has also been achieved by using packed, hollow glass spheres, typically of a size ranging from 15 to 150/xm in diameter and coated on the exterior with a film of low emittance material such as aluminum. These hollow spheres, which generally have a wall thickness of 0.5-2.0 m, substantially increase the conduction thermal resistance but markedly reduce the heat capacity and the mass relative to solid particles. Further, hollow microspheres offer a lightweight and low heat capacity alternative to MLI. A comparison of these two insulations is presented in Table 7.4. 

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