REFRIGERATION AND AIR CONDITIONIN

[Music] it's a hot humid day and steve and ted have worked up a sweat playing baseball it'll feel good to get out of the hot sun inside it's much cooler that's because ted has an air conditioner this is one kind of cooling device the refrigerator in the kitchen is another kind of cooling device how does it work a basic principle of refrigeration is that cold is the absence of heat to make something like lemonade cold it's necessary to remove heat let's see how heat is removed from a refrigerator we'll begin by looking at the basic working parts this model of an electric refrigerator shows the condenser the compressor driven by an electric motor and cooling coils which run through the freezer the coils are usually made of metal but transparent plastic has been used here to show liquid inside as the liquid boils inside the tubing it removes heat from the refrigerator to understand how let's consider another liquid more familiar to us water you've seen things cool by water in ironing sprinkling water over the material being pressed helps prevent wrinkling it also prevents the cloth from getting too hot absorbs much of the heat from the iron as the water absorbs the heat it evaporates changing to steam heat is absorbed whenever a liquid evaporates so evaporation is a cooling process this principle applies to all liquids rubbing alcohol is another example an alcohol rub down gives you a soothing cool feeling the alcohol cools the skin because it evaporates quickly even at body temperature as it evaporates changing from a liquid to a gas the alcohol absorbs heat from the skin so alcohol cools by evaporation consider another liquid freon the freon has been kept in a vacuum bottle because it has a very low boiling point so low that when it is poured into the test tube the freon changes from a liquid to a gas almost instantly this rapid evaporation absorbs heat quickly bringing the temperature in the tube down below zero fahrenheit this liquid freon is the refrigerant used in most home refrigerators today as the refrigerant evaporates in the coils of a refrigerator it absorbs heat from inside the refrigerator keeping it cool this is the essential principle by which a refrigerator works in this animated diagram you can see that as the refrigerant evaporates changing from a liquid into a gas the gas is not released into the air instead it is channeled through the tubing leading down into the compressor the compressor compresses the gas forcing it into the condenser coils under great pressure under this pressure the gas condenses becoming a liquid again back in its liquid form the refrigerant is ready to be released once again into the cooling coils the refrigerant is used over and over evaporation condensation and evaporation again the refrigerant is moved by the compressor which is powered by an electric motor so electricity supplies the energy in a gas refrigerator gas provides the energy at the bottom of the refrigerator is a burner where the energy from gas is released as heat the heat from this flame provides the energy needed to move the refrigerant to where it will evaporate in much the same way as the refrigerant evaporates in the coils of an electric refrigerator as a refrigerant evaporates remember it absorbs heat but what happens to this heat the heat is carried by the gas to the condenser here the gas gives up its heat as it is condensed back into a liquid in this way the refrigerator absorbs heat from one place and releases it at another to keep this heat from returning to the cooling coils the coils are separated from the condenser by the refrigerator box heat is moved outside the box keeping things cool inside that's how the refrigerator works an air conditioner works in much the same way as a refrigerator removing the case reveals the working parts these parts are similar to the ones used in the refrigerator in front are the cooling coils where heat is absorbed by the refrigerant as it evaporates from the cooling coils the gaseous refrigerant moves along tubing to a compressor just as in the refrigerator here the gas is compressed and pumped into condenser coils in the condenser coils heat is released from the refrigerant as it is condensed from a gas back into a liquid near the condensing coils in the air conditioner is a fan the fan blows air across the coils speeding the removal of heat so heat is released from the condensing coils after being absorbed at the cooling coils just as in the refrigerator unlike the refrigerator the air conditioner does not have its own insulated box instead the room in which it is mounted is its box the front part of the air conditioner where heat is absorbed extends into the room the back part of the air conditioner where heat is released extends outside in this way heat is removed from inside the house this is how an individual room air conditioner works this office building does not have an individual air conditioner for each room instead it has one large air conditioner which is part of a central air conditioning system this is the outdoor unit where heat is released through the grill you can see a large fan which blows air across the condenser coils inside the building in this unit are the cooling coils a fan circulates air from the cooling coils up through the metal ductwork to the various rooms in each room there are two sets of vents near the floor are vents through which the cool air is blown into the room as the cool air absorbs heat from the room it becomes lighter and rises toward the ceiling having absorbed heat from the room the air reaches another set of vents where the air is drawn out of the room to be cool once again this animated drawing shows how the air circulates through the room we call this process convection convection currents like these are also found in a room having an individual air conditioner this is how warm air is brought to the air conditioner to be cooled and re-circulated in this room air conditioner you can see a fan which helps circulate the air in normal use the fan is hidden behind a protective grille which has a filter to remove dust from the air the temperature of the air is controlled by a thermostat the air moving through this air conditioner remember is cooled in much the same way as these drinks were cooled in the refrigerator by the removal of heat whenever we cool something we absorb heat from one place and move it to another you've seen how this is accomplished by refrigeration and air conditioning you