1.
1
Exercise booklet
Calculating vapor quantities
Authors : Patrick Delpech, Etienne Hoonakker
199-201613
Steam – water sub-station Source Collard et Trolart

2.
2
1) Calculating energy quantities – HND level
Q = M × Δh
When :
Q : enthalpy in [Wh]
M : mass in [kg]
Δh : [Wh/kg]

3.
3
Question 1 :
What quantity of heat (in [kWh]) is required to produce 65 [kg] of vapour at 100 [°C] (212°F) from water at 60
[°C] (140°F) ?
Babcock Steam Boiler
Question 2 :
What quantity of heat (in [kWh]) is required to produce 65 [kg] of vapour at 2 [bar] of effective pressure from
water at 45 [°C] (113°F) ?

4.
4
Question 3 :
What will be the quantity of energy (in [kWh]) restored by the condensation of 3 tonnes of saturated vapour,
initially at 15 [bar], knowing that the condensed water (condensates) will be immediately discharged at 201.45
[°C] (395°F) ?
Question 4 :
What will be the quantity of heat provided by the condensation of 3 tonnes of saturated vapour initially at 5
[bar], the condensates having been discharged at 60 [°C] (140°F) ?

5.
5
2) Calculating power – HND level
P = qm × Δ h
When :
P : power in [W]
qm : mass flow of vapour in [kg/h]
Δh : [Wh/kg]

6.
6
Question 1:
What power is necessary to vaporise 65 [kg/h] of water at 15 [°C] (59°F) at atmospheric pressure (in [kW])?
Steam boiler Direct Industry
Question 2:
What power is required to produce 15 [t/h] of saturated vapour at 4 [bar] (effective) from water at 60 [°C]
(140°F) (in [MW]) ?

7.
7
Question 3:
What power in [kW] will be provided by the condensation of 0.3 [t/h] of saturated vapour initially at 15 [bar],
the condensates having been discharged at 60 [°C] (140°F) ?
Water- steam sub-station – source Direct Industry

8.
8
3) Calculating vapour flow rates – HND level
qm = P / Δ h
When :
P : power in [W]
qm : mass flow of vapour in [kg/h]
Δh : [Wh/kg]

9.
9
Question 1:
What, in [kg/h] is the flow rate of vapour at 4 [bar] necessary to provide 750 [kW] knowing that the
condensates from the exchanger are discharged at 60 [°C] (140°F) ?
CPCU Steam Sub-station – source Axis
Question 2:
What will be the flow rate of condensates in [litres/h], discharged at 85 [°C] (185°F), from an exchanger of
1,200 [kW], supplied with vapour at 6 [bar]?

10.
10
4) Summary exercises – HND level

11.
11
Q1: We have vapour available at 4 [bar]. We want to heat 15 [m3
/h] of water in an exchanger from 70 [°C] to
110 [°C] (158°F to 230°F).
With condensates discharging at 80 [°C] (176°F), what vapour flow rate will be required?
Before doing the calculation the problem will be represented in the diagram below, with all the data.
Q2 : On the horizontal vapour/water exchanger below, indicate the vapour inlet, the condensates outlet and
the water inlet/outlet.
Source Spirax

12.
12
Q3 : 45 [m3
/h] of water at 45 [°C] (140°F) is heated in a vapour/water exchanger supplied by 1.5 [t/h] of
vapour at 8 [bar].
Knowing that the condensates are discharged at 85 [°C] (185°F), calculate the water outlet temperature of the
exchanger (after having represented the data on the diagram below).

13.
13
5) Summary exercises (contd.) – HND level

14.
14
Question 1:
15,000 [m3
/h] of air at -10 [°C] (14°F) is heated by a coil supplied with 220 [kg/h] of vapour at 4 [bar].
The coil is clogged and the condensates are discharged at abnormally high temperatures of 135 [°C] (275°F).
After having represented the problem on the image below, calculate to what the temperature the air is heated.
Question 2:
We have cleaned the coil from the previous exercise, thereby increasing its thermal exchange with the air.µ
The condensates are now discharged at 55 [°C] (131°F).
Supposing that the vapour and air flow rates remain the same, to what new temperature is the air heated ?

15.
15
Question 3:
Complete the table:

16.
16
6) Vapour table – HND level