 The next topic that we're going to take a look at is that of air conditioning processes. Now these fall under the area that we call with an acronym called HVAC heating ventilation and air conditioning. So with this what we're going to be doing is we're going to be looking at different air conditioning processes. Now these would be air conditioning processes for example in the building they might be currently in. So heating, cooling, humidification, things like that. But the processes that we will be considering are the following. So we're going to look at the simplest would be simple heating where you're adding thermal energy to an airstream to heat it for example in the winter. Simple cooling that would be our air conditioning process when it's hot outside and we want to cool. There's also humidification. Sometimes you want to add moisture to the air for example now in North America it's winter and things can be quite dry and so when you condition the air you will want to add moisture in order to bring the relative humidity up to a more comfortable level otherwise your skin will crack. And then at other times of the year for example if you're in a very hot and humid climate you'll sometimes want to remove moisture so that's what we refer to as being dehumidifying. So these are some of the processes that we will be looking at as part of heating ventilation and air conditioning and we'll also be looking at combinations of these. Now we talked about the psychrometric chart last class or last module and what we said is that the psychrometric chart it is a beautiful shortcut for being able to do these calculations very quickly. However remember that it only applies if you're dealing with atmospheric air at one atmosphere so 101.325 kPa. If they take place at different pressures then you need to have a different chart that has been corrected for your elevation or you need to use the equations that we looked at earlier. So that is heating ventilation and air conditioning, air conditioning processes. What we're now going to do is we're going to go through and look at heating ventilation and air conditioning in a generic manner and I'll show you the schematics as well as the equations that we'll be using and then we'll dive in a little further and look at individual processes and then in the next lecture we'll be looking at solving problems so that's where we're going with HVAC applications.