Cooling water flows through the 25 . 4-mm -diameter thin-walled tubes of a steam condenser at 1 m/s. and a surface temperature of 350 K is maintained by the condensing steam. The water inlet temperature is 290 K. and the tubes are 5 m long. (a) What is the water outlet temperature? Evaluate water properties at an assumed average mean temperature, T m = 300 K. (b) Was the assumed value for T m , reasonable? If not, repeat the calculation using properties evaluated at a more appropriate temperature. (c) A range of tube lengths from 4 to 7 in is available lo the engineer designing this condenser. Generate a plot to show what coolant mean velocities are possible if the water outlet temperature is w remain at the value found for part (b). All other conditions remain the same.
Cooling water flows through the 25 . 4-mm -diameter thin-walled tubes of a steam condenser at 1 m/s. and a surface temperature of 350 K is maintained by the condensing steam. The water inlet temperature is 290 K. and the tubes are 5 m long. (a) What is the water outlet temperature? Evaluate water properties at an assumed average mean temperature, T m = 300 K. (b) Was the assumed value for T m , reasonable? If not, repeat the calculation using properties evaluated at a more appropriate temperature. (c) A range of tube lengths from 4 to 7 in is available lo the engineer designing this condenser. Generate a plot to show what coolant mean velocities are possible if the water outlet temperature is w remain at the value found for part (b). All other conditions remain the same.
Solution Summary: The author calculates Remold's number for the type of flow as follows: lrho =997kg/m
Cooling water flows through the
25
.
4-mm
-diameter thin-walled tubes of a steam condenser at 1 m/s. and a surface temperature of 350 K is maintained by the condensing steam. The water inlet temperature is 290 K. and the tubes are
5 m
long.
(a) What is the water outlet temperature? Evaluate water properties at an assumed average mean temperature,
T
m
=
300
K. (b) Was the assumed value for
T
m
, reasonable? If not, repeat the calculation using properties evaluated at a more appropriate temperature. (c) A range of tube lengths from 4 to 7 in is available lo the engineer designing this condenser. Generate a plot to show what coolant mean velocities are possible if the water outlet temperature is w remain at the value found for part (b). All other conditions remain the same.
A 10mm diameter and 20m long smooth tube is maintained at a constant surface temperature. Water enters the tube at 25 °C with mass flow rate of 0.01 kg/s.
Properties of water at average mean temperature are: K= 0.65W/m.K, dynamic viscosity = 0.486X10^-3 Kg/m.s, Pr = 3.12
The flow at the end of the pipe is ?
Current Attempt in Progress
Consider pressurized water, engine oil (unused), and Nak (22 %/78%) flowing in a 20-mm-diameter tube.
(a) Determine the mean velocity, in m/s, the hydrodynamic entry length, in m, and the thermal entry length, in m, for each of the fluids
when the fluid temperature is 366 K and the flow rate is 0.014 kg/s.
(b) Determine the mass flow rate, in kg/s, the hydrodynamic entry length, in m, and the thermal entry length, in m, for water and engine
oil at 300 and 400 K and a mean velocity of 0.018 m/s.
Part A
Your answer is incorrect.
Determine the mean velocity, in m/s, the hydrodynamic entry length, in m, and the thermal entry length, in m, for each of the fluids
when the fluid temperature is 366 K and the flow rate is 0.014 kg/s.
Liquid
water
engine oil
Nak
(m/s)
!
i
XALA(M)
xer (m)
Attempts: unlimited Submit Answer
Consider pressurized water, engine oil (unused), and Nak (22%/78%) flowing in a 20-mm-diameter tube.
(a) Determine the mean velocity, in m/s, the hydrodynamic entry length, in m, and the thermal entry length, in m, for each of the fluids
when the fluid temperature is 366 K and the flow rate is 0.01 kg/s.
(b) Determine the mass flow rate, in kg/s, the hydrodynamic entry length, in m, and the thermal entry length, in m, for water and engine
oil at 300 and 400 K and a mean velocity of 0.022 m/s.
Part A
Determine the mean velocity, in m/s, the hydrodynamic entry length, in m, and the thermal entry length, in m, for each of the fluids
when the fluid temperature is 366K and the flow rate is 0.01 kg/s.
Liquid
Um (m/s)
Xfdh (m)
Xfd,t (m)
water
i
engine oil
i
i
i
Nak
i
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