How a fridge works

Published

In this video Matt shows us how a modern refrigerator works.

Video Transcript:

 

Hi, I’m Matt from eSpares and in this video I’m going to show you how a fridge works.

Now we all know it’s important to keep fresh food in the fridge. The bacteria that allows food to go off can’t really live below five degrees Celsius, so keeping our food in the fridge keeps it fresh for longer. Now the process of refrigeration is actually quite a straightforward one. If you lick the back of your hand, and then blow on it, it starts to feel cool straight away. That’s because as that liquid evaporates into a gas it draws heat away from the skin. And in a fridge we’ve just got a continuous process where a refrigerant is being allowed to turn from a liquid into a gas and then being turned back into a liquid again. Let’s take a look at the back of this old Zanussi fridge freezer, and we’ll start down here with the compressor.

It’s essentially an electric pump, which is pushing a refrigerant around a closed system. First along the outside of the fridge, then the inside of the fridge, before returning back to the other side of the compressor, to continue the cycle. Now in the old days they used to use Ammonia as the refrigerant and that was quite toxic, they then changed to Freon, which you may remember as the stuff that did the damage to the ozone layer. This fridge freezer uses isobutane. It doesn’t really matter what the refrigerant is, it just needs to be a substance that can easily turn from a liquid to a gas and back to a liquid again.

So starting on the high pressure side of the compressor, our refrigerant gas gets very hot, much like a bike pump gets hot as you put the air under pressure when you’re inflating a tire. And that heat is radiated away in this condenser coil. It’s like an ordinary household central heating radiator. And you can actually feel when it’s on, it’s very hot on this side, getting cooler as you move across so that by the time it’s over here, our refrigerant has cooled down sufficiently to be condensed into a liquid, where it goes and sits in a reservoir at the bottom of the appliance.

Our liquid refrigerant then passes into this thing, which is called a filter/dryer. And that just traps any contaminants and removes any moisture which is important because the refrigerant now passes into this, what looks like a wire, it’s actually a very fine capillary pipe. And that feeds up to the inside of the fridge to the evaporator coils. Now on your fridge or freezer you may not be able to see the evaporation coils, they are probably behind a panel in the back or the top of the unit.

But on this Hotpoint fridge freezer you can actually see the evaporation coils here, they actually form part of the shelf structure. So after passing through that fine capillary, our refrigerant liquid passes into this much larger diamiter coil where it’s allowed to expand and evaporate into a gas and that draws the heat away from the inside of the unit. Now at this point the pump, or compressor, is now drawing that gas through the whole system, to be recycled and used again.

Everything is encased in a very thick layer of insulation to make sure that the only heat that is drawn away is from the contents and the inside of the freezer. Most fridges will be cooled by evaporation coils in exactly the same way, although on some fridge freezers cold air is simply drawn up from the freezer unit into the fridge.

Now the big problem with the refrigeration process is that every time we open the door we let moist air in, and that air condenses into water, which needs to go somewhere.

On a fridge it condenses on to this back panel where it drains down and out through this drain hole. And in the freezer compartment that moisture builds up as frost, and in a freezer like this you’ll need to manually defrost, by turning it off and draining away the water as it melts. On a frost-free or auto-defrost freezer, the compressor will periodically stop and there are heating elements around the evaporator coils, which will heat up and melt away the frost and that water will drain away at the back of the appliance. And all that water ends up in this evaporation tray. And that just sits on top of the compressor where it’s nice and warm, and that just evaporates all that water away. So there we go, that’s how a fridge works.

Now if you need any spare parts for a fridge or freezer, you can find them for all makes and models on the eSpares website.

Thanks for watching.