Welcome back. So here's our online steam calculator. And again, we need to know what general vicinity the steam tables were in. So, are we in the superheat region, the compressed liquid region, or in the saturation region? Since this is the entrance to the steam turbine, you should have gone to the steam tables, which are these first tables here, the general properties. And since we have pressure and temperature, and we have that information for state one in both bar and degree Celsius. We're all set to just input our data and determine what the enthalpy is at the entrance to the turbine. So, we have 100 bar and 600 degrees Celsius, and we calculate the state conditions. We can either use the results up at the top or the results down here. And what we see is that the enthalpy is 3,626 kilojoules per kilogram, so this is specific enthalpy. And we're also going to take this information with us too, the entropy information. And you'll notice that 6.9045 in kilojoules per kilogram-Kelvin. So entropy has a different set of units than enthalpy. And what we're going to do is use this information to help us determine the state's conditions for different portions of the process. So we're gonna take this information with us. Write these two pieces of information down, then we'll go back to our state diagram. Okay, so we used our online steam calculator to determine the enthalpy at the entrance to the first stage, and we collected the information about entropy when we were there, too. We were also asked to determine the enthalpy at the entrance to the second stage and you could have done that on your own. Or hopefully, you did do that on your own. And remember, we have temperature and pressure was already given to us. The entrance state to the second stage of the turbine was 25 bar and 600 degrees Celsius, giving us an enthalpy of 3,686.8. And again, while you were there, hopefully, you would pick up the information about entropy, as well. And I'll show you how we're gonna use the entropy information here in the rest of this segment. Okay, so so far we've pinned down states one and three completely. So we have the enthalpy and entropy information for those states. So moving on, taking the information we learned about states one and three and the information that we have in the superheat region shown in this table. I want you to give me a guesstimate for the temperature and the enthalpy of the water at the entrance to the condenser. So, hopefully, you have sitting next to you your diagram of the state conditions. I'll just draw a little sketch of it here so we have a point of reference. So remember, we have three isobars. And here's temperature, and here's entropy, and we just determined state one and state three. So one, two, three, four, here's five, and here's six. So, we're asked to find the temperature and enthalpy of the water at the entrance to the condenser. And I intentionally didn't give you the numbers for this. Cuz I want you to be able to practice going back and forth between the schematic and understanding how the schematic relates to the temperature-entropy diagram. So we want the entrance to the condenser. Well, the entrance to the condenser is state four, right there, okay? So we know that state four is defined as the lowest pressure in the system. So, that's a pressure of one bar. And as luck would have it, the table I have provided is for one bar. We're assuming that's in the super heat region, which is a very good assumption. Because remember, we don't like our turbine to experience phase change. So, in general, all of these states are going to be in the super heat region or very close to a fully saturated vapor. But we really don't wanna go into superheat region because droplets would form, and the droplets could pit our rotating machinery, so that becomes a durability issue. So again, this is a superheat tables at one bar. Now, from our previous information at state three, we found the entropy at state three again using the online steam calculator, that it was 7.598 kilajoules per kilogram-Kelvin, and this is a specific entropy. So, we have a pressure of one bar that defines state p4 and we know that the entropy at state three is identically equal to the entropy at state four. So we have state three. We go to our table and we look for the list of entropies. And we see, oh, we're about 7.6. And so, we look at these numbers here. I want you to determine what you think would be a good estimate for the enthalpy at the entrance to the condenser. And if you feel like it, you could say, hey, what do you think the temperature is too? So I want you to get your best guesstimate or estimate of those values, and then come check back with the video, and we'll see how close you are. Okay, so hopefully, you used that table to show you that well, it was about 7.4 entropy at 120 degrees, and you had it 160 degrees, and entropy of about 7.66. And so 7.6, which is about halfway between these two, is 7.59, 7.56 is pretty close. So we can say, hey, the entrance condition to the condenser is a temperature of about 140 degrees and an enthalpy of about 2,760 kilojoules per kilogram, okay. And these are the types of tables that you'll most often work with. The online calculators are becoming more available, but as you saw from our example, we can't access this portion of that database without paying for access. So, if you want free steam tables, you really need to be able to use the tables that are available. So again, this is just an excerpt from a steam table for the superheat region. So we're gonna keep walking around our state diagrams. Now, we've got states one, three, and four fully defined. So let's keep going. Okay, so now we're going to use the data from the water saturation tables to determine the enthalpy and temperature at the exit of the condenser. Again, I want you thinking what number is the exit of the condenser and what state is it on my temperature entropy diagram. So again, we'll do it real quickly here. Here's my little sketch again for my temperature and entropy. And again, we draw our little isobars. And I'm just gonna sketch a part of it now. The exit of the condenser, remember, is the fully saturated condition. Okay, so remember for our numbering scheme here, we have one, two, three, four. So, we're talking about state five, the exit of the condenser. So we know that at state five, we have a fully saturated liquid with a quality of zero. So this excerpt is an excerpt from saturation tables. Remember, when we're in the saturated region, the temperature and pressure are dependent. So, if I tell you the pressure is one bar, the temperature has to be 99.6 degrees Celsius. Okay, that's the saturation temperature for one bar, one atmosphere of pressure. Remember, we only list the saturated liquid values and the saturated vapor values, okay. So, that's the hf is the saturated liquid values, hg is the saturated vapor. And I've given you both the enthalpy and the entropy values, cuz we're going to use that entropy information again. So looking at this table, I want you to think about what's the appropriate value for the enthalpy and temperature at the exit of the condenser. Think about that and we'll answer that next. So that one I thought was pretty straightforward for you. Remember, we're looking at a saturated liquid at the exit of the condenser. So, all we need to do is read the values for the saturated liquid enthalpy and the saturated liquid entropy. And again, once we know the pressure is one bar, the temperature has to be essentially 100 degrees C. Let's keep going. So now we've got states one, three, four, and five fully defined. Now we need to move on. We're gonna take the information that we learned in the previous saturation tables. And we're gonna use that information plus this excerpt from the compressed liquid tables, and we're going to guesstimate the temperature and enthalpy of the water at the entrance to the steam generator. So again, these are data that are for the highest pressure in the system, 100 bar, and again, refresh our memory here. We have the temperature entropy sketch. So again, we put the isobars on here. And state one to two, up to three, down to four, over to five, and then up to six. So in order for us to define six, we have the pressure. That's again, the highest pressure in the system. And we understand that from five to six is an isentropic process. So, in order to determine the enthalpy at state six, we need to know that the entropy at six is equal to the entropy at five. So that was the value we had determined in our previous step. So that's a value of 1.3. So S6=1.303 Kilojoules per kilogram-Kelvin. So using this information from the compressed liquid region of the steam tables, I want you to guesstimate what the enthalpy is at the entrance to the steam generator, and then we'll check your answer when you get back. Cool, so hopefully, you saw that on the table where we had entries for 80 and 140 degrees Celsius, that 1.3 falls pretty close to 100 degrees, right in the middle of those two. So we have an enthalpy of 426.5 at the entrance to the steam generator. Okay, so, so far, we've defined every state in the system except for the state between the two stages of expansion and the turbine. And I want you to, based on this process that we just followed, I want you to think about what tables would you used. Compressed liquid, saturation tables, or superheat tables in order to find the enthalpy at the exit of the first stage of the turbine. And what parameters, temperature, pressure, entropy, enthalpy, what would you use to fully define the state? And we'll start with that in the next unit.
