Temperature gradient risk

Gradient risk The percentage of people predicted to be dissatisfied due to a difference in air temperature between the ankle and the head. Induced The temperature of the internally induced air flow. 

Airway surfaces, like skin, are continually exposed to the ambient environment. In contrast to skin submucosal vessels, however, w hich shed excess heat by vasodilating when heated and conserve heat by vasoconstricting when chilled, it is unclear how the airway vasculature responds to temperature extremes. Inspiring cold air poses two challenges to conducting airway tissues the risk of tissue injury should inadequate heat reach the airway surface and excessive body heat loss due to increasing the radial temperature gradient. Vasodilation would protect airway tissue but increase heat loss, while vasoconstriction would produce the opposite effect. 

For most HP boilers, the sublayer film temperature gradient is more important than the bulk boiler water chemistry in determining the risk of deposition of salts. If a local overconcentration of salts occurs, waterside scaling and deposition are the inevitable results. 

Scale-up is typically uncritical if excessive cooling rates are avoided. Large temperature gradients can carry the risk of spontaneous solids formation or encrustation on larger scale, when the surface-to-volume ratio is smaller. 

To combine the advantages of packed-bed and catalytic wall microreactors, catalytic bed microreactors were proposed recently. In this novel reactor design, the catalyst is applied on metallic filaments or wires which are incorporated in a microreactor, leading to a low pressure drop and a nanow residence time distribution [87-89]. By insertion of metallic wires a uniform gas distribution and a reduced risk of temperature gradients is obtained. However, similarly to catalytic wall microreactors, an increase in the specific surface area of the grid or wire is required. In addition to metallic wires and grids, modified ceramic tapes can also be used as a catalyst support [90]. 

Thermal stresses During cool-down after cure, high thermal stresses can occur due to inhomogeneous cooling. In order to limit the risk of microcracking, the cool-down temperature gradient should be limited. 

---