Hi,
I have an existing heat exchanger (no longer in use as this was replaced before) which i wish to re-utilize for a different application (different flow and temperatures), but I am not sure if I can really utilize the existing equipment.
My existing heat exchanger has the following design data:
Fluid service: Water on both sides
Fluid details
Hot side:
Flow: 242 m3/hr
DT: 12.6 C (67.6 to 55)
DP: 12 kpa
Cold side:
Flow: 300 m3/hr
DT: 10 C (33 to 43)
DP: 61 kpa
Heat exchanger details:
Q: 3489 kw
LMTD: 23.3
U: 3256 W/m2K
A: 46
Countercurrent
94 plates
1 pass
Now, for my new fluid:
Fluid service: water on both sides
Fluid details
Hot side:
Flow: 200 m3/hr
DT: 10 C (43 to 33)
DP: 100 kpa (max)
Based on the heat load on the hot side, Q is only 2322 kW.
The cold side fluid is not yet designed fully (pump not yet bought), but would like to target of 10C DT max which would translate to ~200 m3/hr (30C to 40C), although the preference is 8C DT (30-38C) which would translate to a flow of 250 m3/hr. This water is going to atmospheric conditions
My initial thought - based on nearly similar flowrates and the Q for the new conditions are lower than what was the original design, it may be usable.
Now as I am into detailing, when I calculated the UA based on the new conditions for the new service, the UAcalc =5x Udesign. This may be due to lower DT across the fluid (less driving force), and in such, I need to compensate with a larger area.
Is the exchanger usable based on Q only, or not? If it is usable, will I not be getting the target temperatures, ie,. instead of 33, it may higher than this, say around 41C (since 10C/5 = 2C)?
Thanks in advance for the help.
Regards,
cat