Short #3 - Saturation

HVAC School - For Techs, By Techs

Bryan Orr

Training, Careers, Airconditioning, Self-improvement, Hvac, Business, Education, Refrigeration, Heating, Ac, Apprenticeship

4.8 • 985 Ratings

🗓️ 12 March 2018

⏱️ 19 minutes

🔗️ Recording | iTunes | RSS

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Summary

This short podcast episode is about saturation and what it means. Bryan covers related topics, including boiling, evaporation, and condensing.

Saturation refers to something that is "full" of something else. In science, "saturation" refers to a substance being in the middle of a phase change. (For example, boiling water stays at 212 degrees until it all boils off and becomes water vapor.) In HVAC, we often use the term to refer to refrigerant with liquid and vapor are present at the same time. The refrigerant is typically both liquid and vapor in the evaporator and condenser; phase changes occur in those two components as refrigerant changes from a liquid to a vapor and vice versa.

Refrigerant tanks are contained systems, so the liquid-vapor mix remains at equilibrium, and the temperature and pressure will change at a predictable rate. That is why we can use the P-T chart to determine the refrigerant type; a given type of refrigerant that is changing state at a given pressure will always be a certain pressure.

The process of changing state is where we can utilize so many more BTUs of heat. When a substance is at saturation, that substance will not increase in temperature so long as it remains in its current state. However, that substance will continue absorbing heat until it fully changes its state. We call the added heat that does NOT contribute to a temperature change "latent heat." Evaporators are so effective at absorbing BTUs of heat because refrigerants have relatively high latent heat of vaporization values; it takes a lot of added heat to make a refrigerant change from liquid to vapor.

However, evaporation can occur WITHOUT boiling. Temperature is only the average heat content, and some faster-moving liquid molecules can still break free and become gas.

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Transcript

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0:00.0	Well, hello, hello there, welcome, welcome to the HVAC school podcast, the
0:06.7	podcast that helps you remember some things you might have forgotten as well as
0:10.6	helps you remember some things you forgot to know in the first place.
0:13.2	I'm Brian and this is a short episode and in this short episode we are going to talk about
0:18.2	saturation and in the process of talking about saturation we're going to talk a little bit about
0:21.6	boiling condensing, sensible, and
0:23.7	latent heat. But before we do that, I want to just remind you that this podcast, like all the others,
0:28.4	in our dossier, I'm not sure if that's the right word, not sure why I used it. I'm not sure it's the right word, but in our bank of
0:36.2	podcasts, they're all supported by our sponsors, our great sponsors. Carrier, Rector Seal, and Mitsubishi Comfort. So here we go.
0:46.2	saturation. What is saturation?
0:48.2	You know, saturation is a word that can mean a lot of different things. In HVACR, we use it in two primary circumstances.
0:56.0	We'll talk about saturation in terms of air saturated with moisture.
1:00.1	So we'll talk about 100% relative humidity air as being completely saturated.
1:05.1	But the most common time that we talk about saturation is in terms of refrigerant being at saturation.
1:10.8	So we'll say a couple different things. We'll say it's saturated, it's at saturation. We'll say it's saturated, it's at saturation, it's in the saturated state.
1:17.2	There's a lot of different, we'll talk about saturation temperature, there's a lot of different examples of us using that
1:22.2	term saturation, saturated in refrigeration and air conditioning
1:26.6	in the refrigerant circuit.
1:27.8	And what we really mean is, is that there is liquid and vapor in the same place at the same time. The most common, you know,
1:35.9	visual example that we see of saturation at work is when we watch a boiling pot of
1:42.0	water. I mean you've heard of this ad nauseum and HVAC when a pot of water boils it boils at
1:47.2	212 in atmospheric pressure. So in this example the matter is fixed, it's water, the pressure is
	...

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