Saturated steam coming off the turbine of a steam power plant at 40°C condenses on the outside of a 3-cm-outerdiameter, 35-m-long tube at a rate of 63 kg/h. Determine the rate of heat transfer from the steam to the cooling water flowing through the pipe. The properties of water at the saturation temperature of 40°C are hfg

Respuesta :

Answer:

Q = 30.07 kJ/sec

Explanation:

GIVEN DATA:

temperature of steam = 40 degree celcius

mass flow rate = 63 kg/h

from saturated water tables,

from temperature 40 °, enthalpy of evaporation[tex]h_f[/tex] value is 2406 kj/kg

rate of heat transfer (Q) can be determine by using following relation

[tex]Q = \dot{m} h_f[/tex]

putting all value to get Q value

Q = 45 *2406

Q = 108270 kJ/h

[tex]Q = 108270 *\frac{1}{3600} kJ/s[/tex]

Q = 30.07 kJ/sec

Explanation:

According to the water table, the value of enthalpy of evaporation at a temperature of [tex]40^{o}C[/tex] is 2406.0 kJ/kg.

Hence, we will calculate the rate of heat transfer by using the formula as follows.

               Q = [tex]m \times h_{fg}[/tex]

where,  m = mass

           [tex]h_{fg}[/tex] = enthalpy of evaporation

Putting the given values into the above formula as follows.

              Q = [tex]m \times h_{fg}[/tex]

                  = [tex]63 kg/h \times 2406.0 kJ/kg[/tex]

                  = 151578 kJ/h

or,              = [tex]151578 \times \frac{1}{3600} kJ/s[/tex]

                  = 42.105 kW

Thus, we can conclude that rate of heat transfer from the steam to the cooling water flowing through the pipe is 42.105 kW.