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[rofice]

Hi all,

I want to calculate area of cooler. Below are details of streams

Temperature Hot in = 70 C

Temperature Hot out = 50 C

Temperature Cold in (water) = 25 C

Temperature Cold out = ?

Mass flow rate of Hot stream = 20kg/s

Cp of hot stream = 0.86 kj/kg-c

Cp of cooling water = 4.18 kj/kg-c 

 

By using formula Q=m*cp*delta(t), = 20*0.86*(70-50) = 344 KW

 

Also Q = U*A*delta(t)

where U = 0.85 W/(m²K).

and delta(t) = LMTD (I am making assumption that cooler operates in true counter flow) 

Now my question is, how I need to select optimum temperature of cooling water out? Because if I select outlet temperature in such manner that LMTD is high then area of cooler will be low which result into low capital investment but at the cost of high utility consumption and vice versa. It is apparent that there must be an optimum between two conditions: much water and small surface or little water ad large surface.

Please guide me in deciding optimal conditions?

 

Regards

Rofice

Edited by rofice, 27 November 2017 - 12:05 PM.