Question

Steam enters an adiabatic condenser (heat exchanger) at a mass flow rate of 5.55 kg/s where it condensed to saturated liquid water at P = 20 kPa. The change in enthalpy of the steam is – 2,491 kJ/kg. The steam is cooled by water from a river. Environmental regulations require that the maximum increase in the river water temperature is 10°C.

a) What is the minimum mass flow rate of river water through the condenser to cool the steam? The Cp for water = 4.184 kJ/kg/K.

Answer 1

The minimum mass flow rate will be "330 kg/s".

Step-by-step explanation:

Given:

For steam,

`m_(s)=5.55 \ kg/s`

`\Delta h=2491 \ kg/kj`

For water,

`\Delta T=10^(\circ)C`

`(Cp)_(w)=4.184 \ kJ/kg^(\circ)C`

They add energy efficiency as condenser becomes adiabatic, with total mass flow rate of minimal vapor,

⇒
`m_(s)* (\Delta h)=M_(w)*(Cp)_(w)* \Delta T`

On putting the estimated values, we get

⇒
`5.55* 2491=M_(w)* 4.184* 10\\`

⇒
`13825.05=M_(w)* 41.84`

⇒
`M_(w)=330 \ kg/s`