Chemical Engineering - Chemical Engineering Basics - Discussion

2. 

In a counter flow heat exchanger, hot fluid enters at 170°C & leaves at 150°C, while the cold fluid enters at 50°C & leaves at 70°C. The arithmetic mean temperature difference in this case is __________ °C.

[A]. 20
[B]. 60
[C]. 120
[D].

Answer: Option D

Explanation:

No answer description available for this question.

Ashok Kumar said: (Aug 22, 2016)  
= (170 - 70) / (150 - 50),

ln (100 / 100) is equal to infinity.

Romil Kikani said: (Feb 18, 2017)  
I think it is logarithmic mean, not an arithmetic mean.

Sk Jha said: (Apr 6, 2017)  
@Ashok

I don't think so.

AMTD = (170+150)/2 - (70+50)/2,
= 320/2 - 120/2,
= 160 - 60 = 100 Ans.

Tejprakash said: (Dec 26, 2017)  
Yes, I agree with you @Ashok.

Raj Musale said: (Sep 9, 2019)  
The answer is 100° C.

Nilesh Singh said: (Nov 20, 2020)  
T1 = 170 - 150 = 20,
T2 = 50 - 70 = -20.
AM=20+(-20)/2= infinity.

Neeraj Kumar said: (Sep 28, 2021)  
LMTD= ΔT1/ln(ΔT1/ΔT2)

ΔT1=170-70 = 100.
ΔT2=150-50 = 50.

Then LMTD = 100/Ln(100/100),
= 100/0.
= ~ infinite.

Options D is the right answer.

Nitesh Ghidode said: (Oct 5, 2021)  
It's a log mean temperature difference.

Nitesh Ghidode said: (Dec 1, 2021)  
Answer should be 100 for AMTD and Infinite for LMTD.

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