Moisture would find its way into insulation by vapour pressure unless it is prevented by

Related MCQs

• 200 kg of solids (on dry basis) is subjected to a drying process for a period of 5000 seconds. The drying occurs in the constant rate period with the drying rate as, Nc = 0.5 × 10-3 kg/m2 .s. The initial moisture content of the solid is 0.2 kg moisture/kg dry solid. The interfacial area available for drying is 4 m2 /1000 kg of dry solid. The moisture content at the end of the drying period is (in kg moisture/kg dry solid).
• In a laboratory test run, the rate of drying was found to be 0.5 x 10-3 kg/m2 .s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m2 /kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is
• The ratio of the actual vapour pressure to the pressure of saturated vapour at the prevailing dry bulb temperature is known as
• The insulation ability of an insulator with the presence of moisture would
• A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2 .°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be
• A sphere 15 cm in diameter is covered with 5 cm of insulation (k = 0.057 kcal/m-hr-?C). The inside and outside surface temperature of the insulation are 315?C and 80?C respectively. The heat loss per sq. m of the outside surface will be closer to
• The mass of water vapour per kg of the pressure of saturated vapour at the air is known as
• 1000 kg of wet solids are to be dried from 60% to 20% moisture (by weight). The mass of moisture removed in kg is
• A wet solid is to be dried from 80% to 50% moisture (on wet basis). Calculate the moisture to be evaporated for 10 tonns of dried product?
• For a given ambient air temperature with increase in the thickness of insulation of a hot cylindrical pipe, the rate of heat loss from the surface would