= 1.0 Btu/lbm-°F) of a diesel engine from 190°F to 140°F, using air (c = 0.245 Btu/lbm F) with an inlet11-80E A single-pass crossflow heat exchanger is used to cool jacket water (cptemperature of 90°F. Both airflow and water flow are unmixed. If the water and air mass flow rates are 92,000 lbm/h and 400,000 lbm/h, respectively, determine the log mean temperaturedifference for this heat exchanger.FIGURE P11-80EAir flow(иктіхеd)Water flow(апmixed)

Question
Asked Dec 4, 2019
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= 1.0 Btu/lbm-°F) of a diesel engine from 190°F to 140°F, using air (c = 0.245 Btu/lbm F) with an inlet
11-80E A single-pass crossflow heat exchanger is used to cool jacket water (cp
temperature of 90°F. Both airflow and water flow are unmixed. If the water and air mass flow rates are 92,000 lbm/h and 400,000 lbm/h, respectively, determine the log mean temperature
difference for this heat exchanger.
FIGURE P11-80E
Air flow
(иктіхеd)
Water flow
(апmixed)
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= 1.0 Btu/lbm-°F) of a diesel engine from 190°F to 140°F, using air (c = 0.245 Btu/lbm F) with an inlet 11-80E A single-pass crossflow heat exchanger is used to cool jacket water (cp temperature of 90°F. Both airflow and water flow are unmixed. If the water and air mass flow rates are 92,000 lbm/h and 400,000 lbm/h, respectively, determine the log mean temperature difference for this heat exchanger. FIGURE P11-80E Air flow (иктіхеd) Water flow (апmixed)

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Expert Answer

Step 1

Heat loss by jacket of water:

Heat loss by water
Q= m,(c), (T-7)
92000x1x (190-140)
Q4600000Btu /h
Heat gain by air
=m,(c,) (t-4)
4600000 400000 x 0.245 x (t, -90)
4600000
400000 x 0.245
06
t=136.938°F
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Heat loss by water Q= m,(c), (T-7) 92000x1x (190-140) Q4600000Btu /h Heat gain by air =m,(c,) (t-4) 4600000 400000 x 0.245 x (t, -90) 4600000 400000 x 0.245 06 t=136.938°F

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Step 2

Difference between inlet of water and air exit temperature:

Temp.diff.between inlet of water and exit of air:
AT T-1
AT 190-136.938
AT 53.062 F
Temp.diff.between outlet of water and inlet of air:
AT = T-
AT = 140-90
AT, = 50°F
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Temp.diff.between inlet of water and exit of air: AT T-1 AT 190-136.938 AT 53.062 F Temp.diff.between outlet of water and inlet of air: AT = T- AT = 140-90 AT, = 50°F

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Step 3

The log mean temperatu...

ΔΤ-ΔΤ
Im CF
ΔΤ
In
AT
= 51.515°F
Im,CF
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ΔΤ-ΔΤ Im CF ΔΤ In AT = 51.515°F Im,CF

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