# 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]. ∞

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.