extra slides lmtd

1
T T T C,in dA H,in C,out H,out C,in H C 1 1 ln T T U A T T mCp mCp T H T C T H,in T H,out T C H H,in H,out C C,out C,in H,in H,out C,out C,in H C 1 1 and mCp T T Q mCp T T T T T T mCp Q mCp Q T C,out Q x H H H C C C dH mCp dT Q mCp dT dH H,in C,out H,in H H,out C,in ln T T AU T T T T Q ,out C,out C,in T T H C H C H C and Q dA Q U T T dA U T T Q Q dT dT mCp mCp LM H,in C,out H,out C,in Q Q A U T T T T T U H C H C H C H C H C 1 1 mCp mCp U T T dA U T T dA dT dT mCp mCp dT dT H,in C,out H,out C,in ln T T T T H C H C H C H C 1 1 1 dT dT U dA T T mCp mCp dT T U T T H,in C,out 1 T T A dA mCp mCp H,in C,out H,out C,in 1 2 LM H,in C,out 1 2 H,out C,in ln ln T T T T T T T T T T T T T H C T T H,out C,in H C 0 H C Solved analytically if , , are constant T T mCp mCp mCp mCp U T LM is also referred to as LMTD

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Heat Exchangers, LMTD

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Page 1: Extra Slides LMTD

TT

TC,in dAH,in C,out

H,out C,in H C

1 1ln T T

U AT T mCp mCp

TH TC

TH,inTH,out

TC

H H,in H,out C C,out C,in

H,in H,out C,out C,in

H C

1 1 and

mCp T T Q mCp T T

T T T TmCp Q mCp Q

TC,outQx

H H H C C C dH mCp dT Q mCp dT dH

H,in C,outH,in H

H,out C,in

ln T T A U T TT T Q

,out C,out C,inT T

H CH C

H C

and

QdA Q U T T dAU T T

Q QdT dTmCp mCp

LM

H,in C,out H,out C,in

Q QAU T

T T T TU

H C

H C H CH C

H C

1 1

mCp mCp

U T T dA U T T dAdT dT

mCp mCp

dT dT

H,in C,out

H,out C,in

lnT TT T

H C

H C H C

H C

1 1

1

dT dT U dAT T mCp mCp

d T TU

T T

H,in C,out 1T T A

dAmCp mCp

H,in C,out H,out C,in 1 2LM

H,in C,out 1

2H,out C,in

lnln

T T T T T TTT T T

TT T

H CT TH,out C,in H C0

H CSolved analytically if , , are constant

T T mCp mCp

mCp mCp U

TLM is also referred to as LMTD