some explanations seem to you to be laboured or too elementary please
have patience and remember that there are others who will appreciate and
better understand the simplified approach.
If you come across any words or phrases that are unfamiliar to you in
the Steam Theory Pages, please email
them to me so that I can create a glossary of terms.
We all know
what happens when the kitchen kettle begins to boil. Steam comes out
of the spout and if the lid isnt a good fit it begins to bob up
What happened inside the kettle between putting in the cold water and
the steam coming out of the spout?
Almost as soon as you put the kettle of cold water on the fire, or the
burner, the heat began to make its way through the metal of the kettle
and into the water. The continuous flow of heat warmed up the water
and made it hotter end hotter until the water began to boil.
As soon as the water began to boil it had reached the stage where it
couldnt take in any more heat. But as the kettle was still on
the fire, or the burner, heat was still trying to get into the water.
What happened then?
A change took place in the water. The extra heat that was trying to
find room in the water was shot out immediately in the form of vapour.
In other words, the extra heat began to evaporate or convert the water
This water vapour is what is known as steam.
If we left the kettle alone long enough the water would continue to
be evaporated by the incoming heat until all of it had been converted
do we use steam?
Why do we
use steam for heating workshops and rooms; for boiling jam; for turning
wet stock into paper; for heating the water that washes dirty clothes
at laundries or cooking cans of peas; for evaporating chemical liquors;
for driving turbines and engines and pumps; for doing the thousands
of jobs in all branches of industry? Why steam in particular? Why is
it in such common use throughout the civilised world?
It is because there is such a common need for heat and pressure energy
(or power energy, if you like) and steam happens to be such a convenient
and economical way of conveying large quantities of heat and pressure
energy from one place to another. Steam is easy to make and it is made
from water of which there is plenty in the world. Steam is easy to control
and is such a very versatile commodity.
For a very simple demonstration of the heat and pressure energy in steam,
let's go back to the kettle in the kitchen. First, we will test the
steam for hotness. If you put a thermometer into the boiling water and
again into the steam at the mouth of the spout, the second reading would
be the same as the first because the steam is the same temperature as
the boiling water.
Now lets test the steam for pressure energy. This time we dont
need to measure temperature. All we need do is watch the kettle lid
bobbing up and down. It is the pressure energy in the steam which is
making the lid bob.
HEAT IN STEAM for the continuing story...