1. to satisfy a heating load of 60 kw a designer is faced with two choices:
1. Use hot water at an entering temperature of 80 C.
2. Use saturated steam at 90 C
After her calculations it was determined that she would need 25 times as much water as steam in
terms of mass flow rate.
What is the temperature of the hot water leaving the coil?
Solution
It is given that the heat load, Q is 60 kW.
First the hot water lost heat, whose entering temperature, T 1 = 80 C.
Let temperature of water leaving the coil is T 2 .
Let mass flow rate of water be m w = 25m,
m = mass flow rate of steam.
The temperature of saturated steam is 90C.
The specific heat at const. pressure for water at 80 C , Cp is 4.2 kJ/kg-K.
The steam is in saturated state. Thus the heat removed will only be the latent heat. There
will be no change in temperature of steam.
The latent heat of saturated steam at 90 C is 2284 kJ/kg.
Thus heat lost by steam = Q = (mass