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# hot water tank tube HX

## hot water tank tube HX

(OP)
hi folks
i am missing something
i am required so size immersed copper U-tube HX in a tank

known
required heat capacity (kw)
Hot side
Th in : 120 °C
Th out : ?

Cold side
Tc in vessel : 20°
Tc out : ?

Vessel target temperature : 80°C

LMTD method not applicable since not all temperatures are known

any past experience on how to approach this tube in vessel HX
how to approach temp in tank that will change during the heating process?
is mass flow on cold side of HX same as product out flow from tank?
what typical U values for copper U-tube bundles?
any specific reference for this application would be appreciated
Replies continue below

### RE: hot water tank tube HX

"Vessel target temperature : 80°C", so my guess is:

Cold side
Tc in vessel : 20°C
Tc out : 80°C

I recommend Kern's Process Heat Transfer.

any past experience on how to approach this tube in vessel HX YES.
how to approach temp in tank that will change during the heating process? TREAT IT AS A CSTR.
is mass flow on cold side of HX same as product out flow from tank? YES.
what typical U values for copper U-tube bundles? NO INFO ON HOT FLUID. LOOK IN KERN'S OR PERRY'S.
any specific reference for this application would be appreciated KERN'S.

Good Luck,
Latexman

### RE: hot water tank tube HX

Then you set up a spread sheet and estimate various flows or Ts.
Calculate based on those and then repeat until the results converge (relax).
Then you can play with changes in flows and Ts and see what the impact is.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

### RE: hot water tank tube HX

For unsteady state batch heat transfer from non isothermal heating source, see eqn 11-35b in the chapter on heat transfer equipment design in Perry Chem Engg Handbook 7th edn. Overall htc U has 2 components : natural convection htc on the outside of the tubes, and forced convection htc on the inside of the tubes - Perry has discussions on these also.

### RE: hot water tank tube HX

HOMEWORK PROBLEM !!!!

MJCronin
Sr. Process Engineer

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