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Early Conquests of Ranjit Singh

Water enters ...

Question

Water enters a counter flow heat exchanges 15°C, flowing at the rate of 1300 kg/hr. It is heated by oil $(C_{p} = 2 k J / k g K)$ flowing at the rate of 550 kg/hr from the inlet temperature of 94°C. The actual heat transfer from oil to water if effectiveness is equal to 0.94 is

15.2kW

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19.4kW

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28.6kW

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22.7kW

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Solution

The correct option is D 22.7kW
$ϵ = 0.94 = \frac{Q_{a c t}}{Q_{m a x}}$

$C_{C} = m_{C} C_{P C} = (\frac{1300}{3600}) (4.186) = 1.511 \frac{k W}{k}$

$C_{h} = m_{h} C_{p h} = (\frac{500}{3600}) 2 = 0.305 \frac{k W}{k} = C_{m i n}$

$Q_{a c t} = ϵ Q_{m a x} = ϵ C_{m i n} (T_{h i} - T_{c i})$

$= 0.94 \times 0.305 (94 - 15) = 22.7 k W$

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Water enters a counter flow heat exchanges 15°C, flowing at the rate of 1300 kg/hr. It is heated by oil (Cp=2kJ/kgK) flowing at the rate of 550 kg/hr from the inlet temperature of 94°C. The actual heat transfer from oil to water if effectiveness is equal to 0.94 is

The correct option is D 22.7kWϵ=0.94=QactQmax CC=mCCPC=(13003600)(4.186)=1.511kWk Ch=mhCph=(5003600)2=0.305kWk=Cmin Qact=ϵQmax=ϵCmin(Thi−Tci) =0.94×0.305(94−15)=22.7kW

Water enters a counter flow heat exchanges 15°C, flowing at the rate of 1300 kg/hr. It is heated by oil $(C_{p} = 2 k J / k g K)$ flowing at the rate of 550 kg/hr from the inlet temperature of 94°C. The actual heat transfer from oil to water if effectiveness is equal to 0.94 is