In an air heating system, heated air at 40°c and 105 kpa absolute is distributed through a 0.2 m × 0.3 m rectangular duct made of commercial steel at a rate of 0.5 m3/s. determine the pressure drop and head loss through a 30-m-long section of the duct. the roughness of commercial steel surfaces is ε = 0.45 m. the dynamic viscosity of air at 40°c is μ = 1.918 × 10–5 kg/m·s, and it is independent of pressure. the pressure drop is pa. the head loss is m.

Frost wedging occurs when water seeps into a crack in a rock, freezes, and causes the crack in the rock to widen. t or f

As part of an industrial process, air as an ideal gas at 10 bar, 400k expands at steady state through a valve to a pressure of 4 bar. the mass flow rate of air is 0.5 kg/s. the air then passes through a heat exchanger where it is cooled to a temperature of 295k with negligible change in pressure. the valve can be modeled as a throttling process, and kinetic and potential energy effects can be neglected. (a) for a control volume enclosing the valve and heat exchanger and enough of the local surroundings that the heat transfer occurs at the ambient temperature of 295 k, determine the rate of entropy production, in kw/k. (b) if the expansion valve were replaced by an adiabatic turbine operating isentropically, what would be the entropy production? compare the results of parts (a) and (b) and discuss.

How many neutrons does plutonium -196 with an atomic number of 78.