Surface air temperature is generally measured at 4 ft. above the ground because
What will be an ideal response?
inaccurate readings might occur if placed too close to the ground
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Estimate the mass diffusivity of methane into air at 300 K, assuming ideal gas behavior.
What will be an ideal response?
Originally 2.00 mol of gas are at standard temperature and pressure If the temperature changes to 47.0°C and the pressure decreases to half of what it was, how many liters do the two moles now occupy? (1 atm = 101 kPa, R = 8.31 J/mol ? K)
What will be an ideal response?
Calculate the Nusselt number and the convection heat transfer coefficient for water at a bulk temperature of 32°C flowing at a velocity of 1.5 m/s through a 2.54-cm-ID duct with a wall temperature of 43°C. Use the Gnielinski correlation and two other correlations given in te text and cmpare the results.
GIVEN
• Water flowing through a duct
• Bulk water temperature (Tb) = 32°C
• Water velocity (V) = 1.5 m/s
• Inside diameter of duct (D) = 2.54 cm = 0.0254 m
• Duct wall surface temperature (Ts) = 43°C
FIND Use three different methods to find (a) The Nusselt number (NuD)
(b) The convective heat transfer coefficient (hc)
ASSUMPTIONS
• Steady state
• Fully developed, incompressible flow
SKETCH
PROPERTIES AND CONSTANTS
for water at a reference temperature equal to the bulk temperature (Tref = 32°C)
Thermal conductivity (k) = 0.619 W/(m K)
Kinematic viscosity (?) = 0.773 × 10–6 m2/s
Prandtl number (Prb) = 5.16
Absolute viscosity (?b) = 763 × 10–6 (Ns)/m2
Prandtl number at surface temperatue(Prs) = 4.06 At the surface temperature of 43°C:
Absolute viscosity (?s) = 626.3 × 10–6 (Ns)/m2
Heavy-water molecules have a mass number of
A) 18. B) 3. C) 12. D) 10. E) 20.