1. You are given the following information of available streams that needs to be
ID: 702086 • Letter: 1
Question
1. You are given the following information of available streams that needs to be either cooled or heated as described below Stream Inlet Temp. Outlet Temp. Flow Rate Heat capacity, C Lb/hr 20,600 27,800 23,000 25,000 Btu/Lb.OF 320 200 500 280 1 140 320 240 480 0.7 0.6 0.5 0.8 4 Assumptions: Uo- 125 Btu/ft2.0F Cost of per year of heat Exchanger: (A) (350) (0.14]- S/year Cost of cooling water per year: (Mw)(8500)(5x10) $/year, MW-Lb/hr Cost of steam/year- (Msteam) (8500)(0.001)- $/year, Mass of steam (Msteam)- Lb/hr Cooling water is available at 75 °F and can be heated to no more than 120 °F Saturated steam is available at 540 °F Temperature difference (Th-Tc) limit is 20 °F also called temperature approach Find the optimum (best) arrangements with minimal total cost per year 0.75Explanation / Answer
While considering the above problem, heat integration using the same streams is difficult as the outlet temperature would cross each other.
But we can estimate the total cost of the individual Heat exchanger from the above data as follows.
A. Calculate Q: m Cp (T2-T1)
Stream 1: 2595600 BTU/hr
Stream 2: 2001600 BTU/hr
Stream 3: 2990000 BTU/hr
Stream 4: 4000000 BTU/hr
B. Calculate LMTD
C. Calculate area, A- Q/U LMTD
D. Calculate Utility required from Q–m Cp (Th-Tc)
E. Calculate the cost of Heat exchanger from Area; cost of utility.
F. Total cost of HE (counter current)
1. Stream 1: 20026 $/ yr
2. Stream 2: 3844 $/yr
3. Stream 3: 24179$/yr
4. Stream 4: 6410 $/yr
If heating is followed by cooling then prefer stream 1 followed by stream 2 which is by far optimum option.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.