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LMTD for Steam Heated Reboiler

LMTD for Steam Heated Reboiler

LMTD for Steam Heated Reboiler

(OP)
I am a 30+ engineer and am a little embarrased to ask.
But how does one handle Q = U*A*LMTD for a Steam Heated Reboiler?
The main issue seem to be LMTD determination
The process side is a constant boiling temperature.
Neglecting steam superheat & steam subcooling, the steam is a constant condensing temperature.
The greater temperature difference equals the lesser tempeature difference
The arithmetic LMTD = (Greater DT - Lesser DT)/LN [(greater DT)/lesser DT]
= (0) / LN [1]
= (0) / (0)
Any comments would be appreciated

RE: LMTD for Steam Heated Reboiler

As far as I know you cannot apply LMTD when you've to deal with change of phase. Try epsilon-NTU method

RE: LMTD for Steam Heated Reboiler

Just use DT. DT = Greater DT = Lesser DT.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

RE: LMTD for Steam Heated Reboiler

How could it be possible to have Greater DT = Lesser DT? You should have a change of state on both sides of the HX. It's a bit strange to me

RE: LMTD for Steam Heated Reboiler

If both fluids in your exchanger are isothermal then the LMTD, the GTD, and the LTD are all equal. You can prove this by applying L'Hopital's rule to the LMTD equation.

-Christine

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