A: So this is a situation with a compressor and we know the CFM and we want to know what the standard CFM would be. So I'm not sure why we're using the steam table, I guess. That's my question to this question.

A: So I was doing the problem in a understanding that like HA should be 40, then I got it like, you know, messed up. So that's why I raised a question. But I actually like, I have to, what do you call it?

A: So there's three questions here. You sent the question about 1170 and we can talk through this problem if you want. But then you sent a snap which was about steam traps.

A: I think it was a good question. I just be good to hear another voice here. Yeah, absolutely.

A: So I'm gonna let you in on a little secret. The enthalpy values in the low pressure air table, right? Air-low pressure are not really reliable values in terms of the absolute magnitude of those numbers.

A: So I took a look at this one for you. And I know you submitted your lines, your lines look fine. And I agree with all of the values that you selected, except for the room enthalpy, which is this one here.

A: So this problem was about a motor driving a fan. Or a motor, a motor driving some equipment where the heat gain was in the room. Yes, I think that using the table as you did is good.

A: So this one was about pressure and volume going through a coil. And yeah, your approach definitely was valid. We actually arrived at the same fundamental solution, me coming from Bernoulli and you coming from the affinity laws.

A: The first Prats Exam, the specific key capacity is given, but it does not say if it is CP or CV, I assume it's CP as none of the problems I have done have every CV for the key equation when it's CV used. The distinction between CP and CV, CP is for constant pressure, heating or cooling. CV is for constant volume heat change.

A: This is from the NC exam. There's a similar problem on NC's practice exam. Oh, I see it's comparing my problem to an NC's problem, which solves it using the maximum operating gauge pressure to find the enthalpy of saturated steam.

A: So I agree that the density of water is a function of water's temperature. That's absolutely true. However, I do not agree that at 120 degrees, the specific gravity is 20% lower.

A: So this example problem was a refrigeration cycle with a cooling capacity given in tons. And this other example was a heat pump operating and cooling mode where the capacity is given in refrigeration tons. So the answer is if it's given in tons, yes, it always refers to the evaporator because the problem is about refrigeration or air conditioning or heat pump that's being operated in cooling mode.

A: This is the answer, so, thank you. So, the question is, which is, this one's very applicable. I talked about the 80% rather principle, but it's problem nine on the practice exam one.

A: I went with that approach and still got the answer. See my solution. And you provide the formula here in the reference handbook for anyone that's looking for this.

A: So this one was about finding the input, horsepower, or the input input head, which is a kind of a funny way to put it. It was a tricky problem. But I started with the horsepower, seven and a half horsepower, and identified that dotted line, the one that you highlighted here.

A: I think you might be thinking about Open cooling towers where the weple temperature outside is the lowest temperature that you can get out Of the air. It's the lowest temperature you can achieve So the weple kind of dictates how much cooling you can do with an open cooling tower as far as an enthalpy wheel An enthalpy wheel is doing something a little bit different. It's it's not a evaporative cooling It's the transfer of sensible and latent energy through the enthalpy wheel.

A: Maybe you're worried, maybe you're not. You're at least aware of the potential for trouble when you use these rule of thumb equations when. Sensible heating and cooling elevation.

A: I was thinking you would use whichever condition has the highest specific volume because when looking at similar problem Of when condensate is removed. We used the higher specific volume. I don't think it's about using the higher value per say I think I Think you want to align the location where you take the specific volume with where the volume flow rate is specified and you should try to align that so Let's say you have an air handler and Let's just make it super simple put a coil in there Fan let's say it's blowing left the right and maybe the problem tells you that a 1000 CFM of Air at a particular condition right entering condition and maybe that entering conditions are fully defined You know the temperature, dry bowl, wet bowl, whatever And it tells you that a thousand CFM entered the unit Then you should probably use the specific volume that corresponds to that entering air condition Because that's where you know the volume If on the other hand the problem statement says an air handler supplies a thousand CFM Then they're telling you something about what's leaving the unit and Maybe they give you the same stuff over here dry bowl wet bulb Then you should probably select the specific volume on this side You basically you want to you want to select the specific volume in the same place where you know the volume flow rate Usually It's the entering condition that's known But not always so you want to try to align that and Usually it doesn't matter So there's a lot of problems where it's just it's not gonna move the needle The The questions to just watch out for and be a little bit extra thoughtful about this are things where there are large changes in temperature and or large changes in humidity Like you're starting from a very hot and humid condition and ending with a very dry and cold condition or vice versa In cases like that you may want to be Put a little bit of extra attention on making sure this checks out But if you have you know 80 degree return air and you're cooling it to 60 degrees and You know there's a very normal amount of latent You're gonna be fine either way So just pick one and move on for me my default is to use the entering condition went into I use the entering condition That's That's never really led me a stray except for the cases that I mentioned where it's extreme changes in temperature or humidity So yeah, definitely don't lose any sleep over that one, but it's a good question It comes up for everyone at some point in the HVAC journey.

A: So we want to subtract from going from 1 to 2. So in this problem, I'll just draw the vapor dome again. This is our state 1.

A: Yeah, the answer is you could. You actually have a choice on this one. So this was a problem about an air handle with bypass.