met11
Chemical
- Nov 13, 2012
- 47
Hello,
I'm developing a sheet to determine the length of tube required to vaporize or condense a given stream. Using the various methods (i.e. Steiner and Taborek (1992), Kattan, Thome and Favrat (1998a,b,c), I can determine the local heat transfer coefficient (alpha) as a function of the vapor quality x. My question is: when determining the average condensing/boiling heat transfer coefficient to use (i.e. in a Q = UALMTD type calc.), if I were going from quality 0 to quality of 1 at the outlet (boiling everything) or vice versa for condensing, would it be safe to assume the heat transfer coefficient is the average of all the local coefficients at each x? (say calculated in increments of 0.01)
i.e. if the tube were 6m long, every 6cm then x would be assumed to go up by 0.01.
I'm just looking to see if this would provide something reasonable enough. I know the detailed method would be to do stepwise increments in length, see how much condenses/boils and then re-calculate the new quality. Has anyone ever encountered this, or does everyone here just pop it into HTRI/Aspen/Chemcad and see what happens?
I'm developing a sheet to determine the length of tube required to vaporize or condense a given stream. Using the various methods (i.e. Steiner and Taborek (1992), Kattan, Thome and Favrat (1998a,b,c), I can determine the local heat transfer coefficient (alpha) as a function of the vapor quality x. My question is: when determining the average condensing/boiling heat transfer coefficient to use (i.e. in a Q = UALMTD type calc.), if I were going from quality 0 to quality of 1 at the outlet (boiling everything) or vice versa for condensing, would it be safe to assume the heat transfer coefficient is the average of all the local coefficients at each x? (say calculated in increments of 0.01)
i.e. if the tube were 6m long, every 6cm then x would be assumed to go up by 0.01.
I'm just looking to see if this would provide something reasonable enough. I know the detailed method would be to do stepwise increments in length, see how much condenses/boils and then re-calculate the new quality. Has anyone ever encountered this, or does everyone here just pop it into HTRI/Aspen/Chemcad and see what happens?
