 In the last lecture what we looked at was the ideal rank and cycle. Now in this lecture what we'll be doing is we'll take a look at actual rank and cycles as well as some of the things that we can do to try to improve the efficiency, the thermal efficiency of this cycle. So the places where we can lose thermal efficiency or where we depart from the ideal rank and cycle will be pressure drop within our heat transfer devices so that is the boiler and the condensing unit. As well we will not always compress or expand isentropically and consequently we have irreversibilities within the system. So if we take a look at a TS diagram for the rank and power cycle and I'll draw out the ideal oops sorry so we started state one we go in our pump to state two go through the boilers super heat up to state three and then we expand down through the turbine and enter the compressor at state four. Now in reality what is going to happen is we're not going to follow this cycle exactly the way that we have shown and in reality what will happen is we have inefficiencies during the compression process and if you recall we quantified that with the adiabatic efficiencies we have eta p for the pump that we can prescribe and then we would get into a two actual state and as we then go into the boiler what will happen is we will have pressure drops so the pressure will ever so slightly drop in the boiler we go up to the same temperature within our boiler but the difference there is due to a pressure drop and then when we expand in our turbine we will not expand isentropically but we will actually increase in entropy and so you might expand out to that state there and so this here would be adiabatic efficiency within the turbine so the component efficiency and then finally we then go into the condensing unit and again we will have pressure drops and so the pressure will drop down and and so we have a difference between our ideal cycle and the real world cycle as illustrated by the difference in the blue line from the black line now what we're always after as engineers is we want ways to be able to make this cycle as efficient as possible and so what I'm going to talk about now are some of the approaches or or things you can do in order to improve the thermal efficiency so I'm going to refer to this as being thermal efficiency games and they're not really games but they're things that you can do in order to improve the thermal efficiency of your cycle so recall the thermal efficiency is equal to the network divided by the heat and and network we said was q in minus q out so that's the way that we've defined it looking at our ts diagram now when we look at this what we have is our heat in is here q in and the heat rejected is there q out now recall when we talked about entropy we had the clausius inequality so that was an expression we had and with that we can say that heat in q in is equal to the area under the curve two to three so that results from the clausius inequality and we can also say q out equals area under one through four so with that if I shade this area in here we can write that the network of the cycle is equal to the shaded area because that would represent the difference between q in and q out so if we want to increase thermal efficiency notice that thermal efficiency we have the network in the numerator if we want the network to increase what we want to do is increase that shaded blue area so things that we can do to increase that area and consequently increase the thermal efficiency of the rank we can do the following things one thing we can do is reduce the condenser pressure and what would that do well if we look back on this diagram here that would drop one through four lower and it would make the area of q out less and consequently that would help increase the thermal efficiency we can super heat the fluid to a higher temperature so what would super heating do a super heating would move this point up even higher and that would then increase the area under the curve which is another way of doing things so that's good and a final thing we can do is we can raise the boiler pressure and so by raising the boiler pressure what we would be doing is this curve here would move up and consequently we would be at a higher point and generating more blue area under our curve and ultimately you can go to i'd mentioned earlier pressure whereby you go super critical and for that you don't even stay in the two phase region and that would be a super critical rank and power cycle but those are different things that you can do in order to increase the thermal efficiency of the rank cycle and consequently in the systems that we're going to be looking at in this lecture we'll be looking at ways of ultimately increasing that blue shaded area