This screencast demonstrates how to use steam tables, and steam tables list certain properties
of steam, and the ones in particular that we're interested in are specific enthalpy, specific internal energy,
and specific volume. They can also list specific entropy, but in this screencast we will focus
on the 3 I mentioned. So what do we mean by specific? This means per unit mass or unit
moles, and in the steam tables that we are going to look at. It will be per mass and
in particular the enthalpy and the internal energy will be in kJ per kg, and the specific
volume will be in meters cubed per kg. So there are three parts of the steam tables that
are usually used. The first ones have to do with saturated steam. What that means is that
you have steam and water in equilibrium. So once you have a pressure or you know the pressure
the temperature is automatically fixed. Vice versa if you know the temperature the pressure
is automatically fixed. The third one we are going to look at is superheated steam, and superheated
steam you are going to need both the pressure and the temperature to find your properties,
because you are beyond the vapor liquid equilibrium line. So let's start with saturated steam.
We can look at 2 different tables, but let's look at the first one, which lists the properties
by pressure. Note we have in this column the different pressures in bar, and in this column we have
temperatures that correspond to these pressures again because this is saturated once you have the
pressure you know the temperature. So let's see how we use this. We are told that we have
saturated steam at 30 bar, and we are looking for the specific enthalpy. So we go to our
table and we find 30 bar. So at 30 bar you see that the temperature is 233.85 degrees
Celsius, and we have our specific volume of both the water and the steam. We have our
specific internal energy, and now we have our specific enthalpy. So we are asked for
the steam. So our specific enthalpy is therefore 2803.2 kJ/kg. If we had wanted instead the enthalpy of the saturated
water, then we would look at this one right here. So let's try another one. Let's say we
want the saturated water and it is at 45 bar, and we are looking for the specific volume. So
let's go to our chart again. Here we are at 45 bar, and here would be all the properties that
we would need for saturated water or steam at 45 bar. Here we want saturated water and
we want the specific volume. So we would look at this value right here. 0.0012696 meters
cubed per kg. So that is the first way that you can use a steam table. Again for saturated
steam. Now we are going to look for our properties under temperature. So let's use this to find
another value. Let's say that we have a pressure that is equal 60 bar and our temperature is equal to
500 degrees C. Now we are looking at this particular part of the table, and the properties we therefore have
are the specific enthalpy, which is 3423.1 kJ/kg. The specific internal energy, which
is 3083.1 kJ/kg and finally our specific volume, which is 0.056671 meters cubed per kg. Again
note that you need both the pressure and temperature to find superheated steam properties. So once you
are comfortable with steam tables you can use their properties to solve mass and and
energy balances that use steam.