Dear Scientist/Engineers,
I have a problem regarding a copper cooling coil and its overall heat transfer coefficient. A copper cooling coil with a 5 cm inner diameter is used to condense steam at a temperature 96.7◦C and pressure 0.9bar. Cooling water enters the coil at a temperature of 15◦C. The steam condenses at a rate of 0.1 kg s−1.
At the bottom of the condenser is an opening of diameter 1 cm, where condensate exits and flows to a collection tank, which is open to the atmosphere at pressure 1 bar. The pipe connecting the two tanks has an inner diameter of 1cm and a total length of 20m.
The level of the liquid in the collection tank is located 2 m below the liquid level in the condenser.
The heat transfer coefficient due to condensation on the outside of the cooling coil is 5000 Wm^-2 K^-1. If the mass flow rate of the cooling water is 5kg s^-1, what is the overall heat transfer coefficient of the cooling coil?
Liquid water:
- heat capacity: 4.2 kJ kg^-1 K^-1
- viscosity: 10^-3 Pa s
- thermal conductivity: 0.6 W m^-1 K^-1
- heat of vaporization: 2400 kJ kg^-1
Use the Dittus-Boelter correlation:
Nu = 0.023Re^0.8Pr^0.4
I have this following equation:
ṁCpc(Tc2-Tc1) =UA*[((TH −TC1)−(TH −TC2))/(ln((TH − TC1)/(TH − TC2)))]
So far I know that I have 2 unknowns which are the length of the cooling coil and water leaving the cooling coil. In addition to these missing parameters, I am also missing the diameter of the outer diameter of the cooling coil.
But I am not sure which other equation to use.
Should I assume that the wall has a negligible thickness (ignore the d0ln(d0/di)/2k from the equation below)?
1/U= 1/hi+diln(d0/di)/2k +(di/d0)/h0
Based on the inner surface area of the cooling coil.
Please help me, thanks.
Attached Files
Edited by Dudesons123, 19 August 2017 - 10:35 AM.