in this video we're diving into the basic refrigerant circuit a Cornerstone of cooling systems both refrigeration and air conditioning let's start with two fundamental principles first heat moves from a higher temperature to to a lower temperature this is why a hot cup of coffee cools down in a cold room heat moves from the higher temperature coffee out into the room and this decreases the temperature of the coffee heat only stops moving once the temperature of the coffee in the room are exactly the same second the relationship between pressure and temperature is key higher pressure means higher temperature and vice versa these principles guide the entire Refrigeration process and will help you understand what's happening inside the system our goal is to move heat from a place we don't want it to a place where it doesn't bother us in refrigeration this means moving it away from the food to the space outside of the refrigerator or the freezer for an air conditioner this means cooling a space by moving heat from in inside the building to outside the building the ideal gas law tells us that the pressure volume and temperature of a gas are all related when we compress a gas its pressure and temperature rise and when we decrease pressure the temperature drops this simple concept is at the heart of how air conditioning and refrigeration systems work specifically by pressurizing and depressurizing the refrigerant which is the gas inside the system that can also turn into a liquid and back to a gas [Music] again when heat is moved and the temperature changes this is called sensible heat and we can measure this type of heat exchange with a thermometer sensible heat changes the temperature of an object without changing its state like from liquid to Vapor or vapor to liquid latent heat on the other hand changes the state without changing the temperature like when water boils it absorbs absorbs heat but remains at 212° F until it all becomes steam we use this latent heat in the refrigerant circuit to move more heat more quickly when the refrigerant boils or condenses the word latent just means hidden because we can't measure it with a thermometer but we know that the heat is contributing to the change from liquid to gas gas or boiling or gas to liquid otherwise known as condensing now let's look at the refrigeration cycle starting with the compressor it compresses the refrigerant this means it squeezes the molecules of refrigerant together increasing its pressure and temperature think of it as the heart of the system pumping the refrigerant through the circuit and for now also think of it as a pressure increaser the condenser is the heat rejector the metering device is the pressure decreaser or the pressure dropper and the evaporator is the heat absorber so one more time compressor is the pressure pressure increaser condenser is the heat rejector the metering device is the pressure decreaser and the evaporator is the heat absorber remember for heat to be absorbed the evaporator must be a lower temperature than the air moving over it because heat moves from hot to cold for the condenser to reject heat it must be hotter than the air moving over it back to the compressor again as the refrigerant enters the compressor it is a cool vapor and the molecules are moving pretty slow inside the compressor the molecules of this cool gas get smashed together so they move faster and get hotter remember higher pressure equals higher temperature when the refrigerant leaves the compressor it's hot and under high pressure this is where the condenser comes in in the condenser the refrigerant releases its heat to the surroundings and condenses into a liquid this process rejects heat out of the refrigerant and changes the state from fully Vapor to fully liquid think of the condenser as the Heat rejector and in the case of your air conditioner at home this heat is rejected outside this is why if you put your hand over top of a split system condenser you'll notice that it blows hot air out that's the heat being rejected from inside the house the metering device then drops the pressure of the refrigerant quite dramatically this sudden drop starts the boiling or flashing process this cools it down even fur further and prepares it to enter the evaporator where the real magic happens this metering device may be a TXV an electronic expansion valve a piston or a capillary tube or some other device but it's always the pressure dropper or pressure decreaser next is the evaporator which is the cold part of the system where the real magic happens here the cold refrigerant absorbs heat from from the environment which is the indoor air in AC or the heat from inside the freezer or refrigerator in refrigeration this refrigerant actually boils or vaporizes during this process despite it being called boiling inside this evaporator it does this at a much lower temperature than water does when we're boiling it on a stove this effectively removes heat and cools the space this is why I also call the evaporator the heat absorber the evaporator is the part in the system that actually makes the air a lower temperature or what we would call cold air and it does this by absorbing heat into itself that it then later rejects in the condenser I want to say this again remember unlike water that boils hot the refrigerant in our system boils cold it absorbs heat from its surroundings when it's boiling this unique property allows refrigerants to effectively transfer heat keeping our food fresh and our rooms comfortable we're able to control the temperature at which refrigerant boils and condenses by changing the pressure like we discussed earlier in the video with the ideal gas law lower pressure equals lower temperature higher pressure equals higher temperature and that completes the refrigerant cycle the vaporized refrigerant then returns to the compressor to start the process all over again through this continuous cycle refrigeration and air conditioning systems provide the cooling we rely on every day there's so much more to learn but you just learn some fundamentals of thermodynamics the science of moving heat and physics the science of stuff so feel free to brag to your friends thanks for watching if you're willing give this video a thumbs up and drop us a comment don't forget to hit that Bell icon to stay updated with all of our future videos and as a quick reminder HVAC school isn't just a YouTube channel dive deeper with us at our main website hvacr school.com curious for more knowledge on the go we've got you covered tune in the HVAC School podcast available on all your favorite podcast apps and while you're at it join our thriving Facebook group also don't miss out on our free mobile applications available for both iPhone and Android we're all about Community vortex byx