 The refrigeration systems that we've looked at thus far in the last lecture are mainly for household applications, be it air conditioning or refrigeration of food. There are many other applications that our refrigeration is applied to and so what we'll be doing in this lecture is taking a look at some of those other different systems and cycles. So we've looked at domestic refrigeration as well as air conditioning, other industrial applications, ice making for personal or human consumption as well as skating rinks. The food processing industry uses refrigeration quite extensively as you can imagine, anything from freeze dried food to freezing food to just even doing any kind of process in developing food. For example, brewing or any of those operations, sometimes you need to cool the things that you're making. The petroleum industry uses refrigeration as well depending upon what particular process you're looking at. So those are some of the industrial applications for refrigeration. Another area that we haven't talked about is cryogenics and so what you're doing here is you're taking a gas and you're converting it into its liquid form. So a popular one nowadays is LNG, liquefied natural gas and that is used to distribute natural gas from different areas of the world to other areas of the world where it's used for electricity generation. It's used for heating of homes. It's also used for cooking. The temperature at which LNG or liquefied natural gas occurs at is about 120 K. So LNG terminals will take gas pipelines as the input and then it goes through the LNG process and then they will put that onto ships and transport it around the world. And then once it gets to the other location, there will be a receiving terminal. They will then transport it throughout that country or that location for use. Liquid oxygen, liquid nitrogen is dropping down 77 K. And then when you get to liquid helium, it's around 20 K, or sorry, hydrogen. And finally liquid helium is around 4 K. Now sometimes if you have a compact system or you need a compact system and you want to get down to the cryogenic temperatures, the Stirling cycle is actually quite useful for achieving cryogenic temperatures in a fairly small compact size. So we looked at the Stirling heat engine. You can reverse that cycle and use it quite effectively as a system for refrigeration or cooling. So those were some of the industrial applications that we can find for refrigeration cycles. What we're going to do now in the next couple of segments, we're going to take a look at a few different cycles that are used for industrial applications. Some of them for liquefaction or cryogenics, others for other systems where you can get lower temperatures than we've been able to get for, for example, our 134A. So that's where we're going to move into now.