Saturated water with a quality of 0.55 and a temperature of 120 oC enters an uninsulated diffuser at a velocity of 180 m/s. The mass flow rate is 1.5 kg/s. If the water is to exit as saturated water vapor at a temperature of 120 oC, with negligible velocity, determine the necessary heat transfer rate.

Explanation:

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In this case, the energy balance for the given uninsulated diffuser is:

Thus, we shall remember that the inlet mass equals the outlet mass and the outlet velocity is negligible, for that reason we obtain:

Hence, solving for the heat, we need the enthalpy at the inlet, which at 120°C for a liquid-vapor mixture results:

Moreover, at 120 °C the outlet enthlapy as saturated steam is:

(Values extracted from Cengel, Thermodynamics 7th edition). In such a way, the required heat inlet is:

Notice that the term having the velocity should be divided by 1000 to obtain  it in kJ/kg.

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explanation:

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