An air heater for an industrial application consists of an insulated, concentric tube annulus, for which air flows through a thin-walled inner tube. Saturated steam flows through the outer annulus, and condensation of the steam maintains a uniform temperature T s on the tube surface. Consider conditions for which air enters a 50-mm-diameter tube at a pressure of 5 atm, a temperature of T m , i = 17 ° C , and a flow rate of m ˙ = 0.03 kg/s , while saturated steam at 2.455 bars condenses on the outersurface of the tube. If the length of the annulus is L = 5 m , what are the outlet temperature T m , o , and pressure p o of the air? What is the mass rate at which condensate leaves the annulus?
An air heater for an industrial application consists of an insulated, concentric tube annulus, for which air flows through a thin-walled inner tube. Saturated steam flows through the outer annulus, and condensation of the steam maintains a uniform temperature T s on the tube surface. Consider conditions for which air enters a 50-mm-diameter tube at a pressure of 5 atm, a temperature of T m , i = 17 ° C , and a flow rate of m ˙ = 0.03 kg/s , while saturated steam at 2.455 bars condenses on the outersurface of the tube. If the length of the annulus is L = 5 m , what are the outlet temperature T m , o , and pressure p o of the air? What is the mass rate at which condensate leaves the annulus?
Solution Summary: The author explains the outlet temperature and pressure drop of the air and mass rate at which the condensate leaves the annulus.
An air heater for an industrial application consists of an insulated, concentric tube annulus, for which air flows through a thin-walled inner tube. Saturated steam flows through the outer annulus, and condensation of the steam maintains a uniform temperature
T
s
on the tube surface.
Consider conditions for which air enters a 50-mm-diameter tube at a pressure of 5 atm, a temperature of
T
m
,
i
=
17
°
C
, and a flow rate of
m
˙
=
0.03
kg/s
, while saturated steam at 2.455 bars condenses on the outersurface of the tube. If the length of the annulus is
L
=
5
m
, what are the outlet temperature
T
m
,
o
, and pressure
p
o
of the air? What is the mass rate at which condensate leaves the annulus?
A two effect system of evaporators with parallel forward feed flow of liquid and vapor is to be designed to concentrate
continuously 10,000 Ib/h of a 10% by weight solution to 40%, the feed being at 150 °F. It is planned to use saturated steam
condensing at 220 °F. Specific Heat of feed liquor is 0.9, while that leaving the first effect is equal to the average specific
heat of feed and product. The overall heat transfer coefficients are 300 and 400 BTU/(f2-hr-°F) for the first and second
effects respectively. The latent heat of vaporization for the vapor leaving the first effect is 1002.3 BTU/lb and 1020 BTU/lb for
the second. Calculate for the steam economy and the heat transfer area in each effect.
Given:
(1)
Required:
and
1. Water flows at the rate of 0.5 kg/s in a 2.5-cm-diameter tube having a length of 3 m. A constant heat flux is imposed at the tube wall so that the tube wall temperature is 40◦C higher than the water temperature. Calculate the heat transfer and estimate the temperature rise in the water. The water is pressurized so that boiling cannot occur.
A shell-and-tube heat exchanger is used to cool compressed liquid methanol
from 176 °F to 104 °F. The methanol flows on the shell side of the
exchanger. The coolant is water that rises in temperature from 50 °F to
86 °F and flows within the tubes at a rate of 68.9 kg s1. Finding the
appropriate thermophysical data and applying the proper equations, you are
required to do the following:
(a)
Calculate i) methanol mass flow rate in the exchanger, ii) methanol
volumetric flowrate at the inlet of the exchanger.
(b) i) For the counter-current flow of the fluids calculate the log
temperature difference, ii) explain the purpose of calculating this
difference, iii) explain, quantitatively, why is the counter-current flow in
heat exchangers preferred to co-current flow.
mean
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