Gradient thermal

In a study (206) of the moisture gain of foamed plastic roof insulations under controlled thermal gradients the apparent permeabiUty values were greater than those predicted by regular wet-cup permeabiUty measurements. The moisture gains found in polyurethane are greater than those of bead polystyrene and much greater than those of extmded polystyrene. 

Skirts are used in vessels and towers. They transmit high axial and bending loads and offer favorable geometry for thermal gradients. In piping, when loads are beyond the capacity of lugs and tmnnions, skirts are often favored. 

Under most circumstances the equiUbtium shape of silicon crystals is octahedral, ie, the slowest-growing faces are (111). However, external conditions can radically alter that shape. For example, when growth is from the vapor, concentration gradients in the gas stream may affect the shape, and when growth is from the melt, the shape is primarily determined by thermal gradients in the melt. 

Tungsten tetrachloride [13470-14-9], WCl, is obtained as a coarse, crystalline, deHquescent soHd that decomposes upon heating. It is diamagnetic and maybe prepared by the thermal-gradient reduction of WCl with aluminum (10). 

Tungsten tetrabromide [12045-94-2] WBr, black orthorhombic crystals, is formed by the thermal-gradient reduction of WBr with aluminum, similar to the reduction of WCI4 (10). 

Container. The battery container is made up of a cover, vent caps, lead bushings, and case. Cost and appHcation are the two primary factors used to select the materials of constmction for container components. The container must be fabricated from materials that can withstand the abusive environment the battery is subjected to in its appHcation. It must also be inert to the corrosive environment of the electrolyte and soHd active materials, and weather, vibration, shock, and thermal gradients while maintaining its Hquid seal. 

Hot and cold sections of the case that are adjacent to each other will reduce thermal gradients and thus reduce case distortion. 

Because of the possibility of voids between layers, it is preferable not to use multilayer vessels in applications where they will be sub-jec ted to fatigue. Inward thermal gradients (inside temperature lower than outside temperature) are also undesirable. 

The direction of vapour transport across a thermal gradient... 

Hot and eold seetions of the ease that are adjaeent to eaeh other will reduee thermal gradients, and thus reduee ease distortion. Horizontally split easings are easier to open for inspeetion than vertieally split ones, redueing maintenanee time. 

Thermal Gradients may be measured or calculated by means of heat flow formulas, etc. After they are established it is likely to be found from the formula that for most cyclic heating conditions the tolerable temperature gradient is exceeded. This means that some plastic flow will result (for a ductile alloy) or that fracture will occur. Fortunately, most engineering alloys have some ductility. However, if the cycles are repeated and flow occurs on each cycle, the ductility can become exhausted and cracking will then result. At this point it should be recognized that conventional room temperature tensile properties may have little or no relation to the properties that control behavior at the higher temperatures. 

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