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Special Cases of Heat Exchanger

A condenser h...

Question

A condenser having effectiveness 0.647, in which the water flows through tube of 25mm diameter at the rate of 0.05Kg/s. The length of the heat exchanger if the OHTC is 230 $W / m^{2 o} C$ and specific heat of water is 4.18

12 m

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4 m

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6 m

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9 m

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Solution

The correct option is A 12 m

d = 25 mm = 0.025m
$U = 230 W / m^{2} - K$
$C p_{w} = 4180 J / k g - K$
$\in= 0.647$
$m_{w} = 0.05 k g / s$

$E f f e c t i v e n e s s f o r c o n d e n s e r (\in) = 1 - e^{- N T U}$
c = 0 for condenser
$0.647 = 1 - e^{- N T U}$
NTU = 1.041

$\frac{U A}{˙ m c_{p}} = 1.041$

$\frac{230 \times π d \times L}{0.05 \times 4180} = 1.041$

$\frac{230 \times π \times 0.024 \times L}{0.05 \times 4180} = 1.041$

$\Rightarrow L = 12.04 m$

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A condenser having effectiveness 0.647, in which the water flows through tube of 25mm diameter at the rate of 0.05Kg/s. The length of the heat exchanger if the OHTC is 230 W/m2oC and specific heat of water is 4.18

The correct option is A 12 m d = 25 mm = 0.025m U=230W/m2−K Cpw=4180J/kg−K ∈=0.647 mw=0.05kg/s Effectiveness for condenser(∈)=1−e−NTU c = 0 for condenser 0.647=1−e−NTU NTU = 1.041 UA˙mcp=1.041 230×πd×L0.05×4180=1.041 230×π×0.024×L0.05×4180=1.041 ⇒L=12.04m

A condenser having effectiveness 0.647, in which the water flows through tube of 25mm diameter at the rate of 0.05Kg/s. The length of the heat exchanger if the OHTC is 230 $W / m^{2 o} C$ and specific heat of water is 4.18