Water flows through a horizontal coil heated from the outside by high-temperature flue gases. As it passes through the coil, the water changes state from liquid at 200 kPa and 80°C to vapor at 100 kPa and 125°C. Its entering velocity is 3 
and its exit velocity is 200 
. Determine the heat transferred through the coil per unit mass of water.
Enthalpies of the inlet and outlet streams are:
Inlet: 334.9 kJ? 
;Outlet: 2726.5 kJ?
What will be an ideal response?
We can write the energy balance (per unit mass) as
From the problem statement, we have ?H = 2726.5 – 334.9 = 2391.6 kJ 
, and no shaft work is done. Since there is a large change in velocity from inlet to outlet, we will take into account the change in kinetic energy, which is
. So, we have
Even for this huge change in velocity, the change in kinetic energy is a very small part of the overall heat requirement.
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