Engineering, 23.04.2021 15:40 jessicawelch25
A 1.75-cm diameter naphthalene mothball is suspended in an air stream at 280 K, 1.0 atm, and constant velocity of 1.4 m/s. Solid naphthalene exerts a vapor pressure of 2.8 Pa at 280 K. Consequently, the naphthalene very slowly sublimes into the passing air stream, with the rate limited by convective mass transfer. The density of solid naphthalene is 1.14 g/cm3, and the molecular weight is 128 g/mole. How long will it take for the mothball to shrink to half of its original diameter? Remember: as the mothball shrinks, its diameter is decreasing, which in turn affects the Reynolds and Sherwood numbers.
Answers: 3
Engineering, 04.07.2019 18:10
Which of the following ziegler nichols tuning methods the response of the controller to a step input should exhibit an s-shaped curve? a)-open loop mode b)-closed loop mode c)-both modes (open & closed) d)-none of the modes (open & closed)
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Engineering, 04.07.2019 18:20
Air flows over a heated plate à t a velocity of 50m/s. the local skin factor coefficient at a point on a plate is 0.004. estimate the local heat transfer coefficient at this point.the following property data for air are given: density = 0.88kg/m3 , viscosity 2.286 x 10 ^-5 kgm/s , k = 0.035w/mk ,cp = 1.001kj/kgk. use colburn reynolds analogy.
Answers: 1
Engineering, 04.07.2019 19:20
Air enters a horizontal, constant-diameter heating duct operating at steady state at 290 k, 1 bar, with a volumetric flow rate of 0.25 m°/s, and exits at 325 k, 0.95 bar. the flow area is 0.04 m2. assuming the ideal gas model with k = 1.4 for the air, determine (a) the velocity at the inlet and exit, each in m/s, and (c) the rate of heat transfer, in kw flow rate, in kg/s, (b) the mass kg 0.3
Answers: 2
Engineering, 06.07.2019 05:10
Air contained in a piston-cylinder assembly undergoes a process from an bar. the initial pressure of 1 bar and temperature of 400 k to a final pressur initial volume of air is 0.2 m3. the process is described by pv- constant. assuming ideal gas behavior and neglecting kinetic and potential energy effects, determine the a)-mass of air, in kg b)-work for the process, in kj c)-heat transfer for the process, in kj pts
Answers: 1
A 1.75-cm diameter naphthalene mothball is suspended in an air stream at 280 K, 1.0 atm, and constan...
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