Understanding Refrigeration Basics

History

In the Australian context is the beginning of refrigeration, and very few people know that a gentleman by the name of James Harrison was actually the inventor of vapor compression refrigeration as we know it, and he’s from Geelong.

First Ice Maker

It was a system that used ether as a refrigerant, which we don’t use today, and it was used to make ice. And the ice, I learned recently, was used in the morgue in Geelong.

And yes, the Americans tend to dispute this a lot, and they claim to have built the first system, but if you do the research as I did, we found that that was actually in 1852. So we did beat the Americans to the refrigeration game.

Basic Refrigeration Cycle

Now, refrigeration in its simplest sense, basicly has four components. And I need to explain these because all about how systems use energy depends on basic understanding of refrigeration.

So this little diagram here really shows that. We have a compressor, a condenser, expansion valve and an evaporator.

Every refrigeration or air conditioning system will have those four components. So we’ll start with the compressor.

Now, remember, it’s a vapor compression system. That’s the fundamental principle here. So a vapor compression system takes vapor, it compresses that to a gas, which is hot and at a high pressure– still a gas. From there, it goes into a condenser, which typically is the outdoor unit with the fans on it, where the gas is first cooled, and then it condenses, which is what the name suggests. So it becomes a liquid.

The liquid comes out of that unit.The liquid travels to this important device called the expansion valve.

What that does is pretty much what happens when you open a bottle of Coke. That release of pressure causes some of it to evaporate.

It immediately cools down. Still a liquid. That liquid then travels into the evaporator, where it  absorbs the heat, evaporates

because if something evaporates, it has to absorb heat turns into a vapor, makes that thing cold,  and there’s air traveling over that.

So that’s where the cooling is being done, and that vapor then finds its way to the compressor,  and the cycle repeats itself.

So all of these things, except the expansion valve, use energy. But all four of them need to be running the right way to minimize the energy use, and that’s

How does a refrigeration cycle work?

So if you look at that in a different pictorial representation, you’ve got a compressor, which is the little diagrammatic thing at the top. A condenser, which typically looks like what you see there on the slide on the right-hand side.

That’s the air cooled condenser. Expansion valve, which is the little valve thing, which most people won’t see because it’s hidden.

And then the evaporator, which is the unit inside the cool room. The expansion valve on the evaporator are the cold bits of the refrigeration system, and the compressor and the condenser are the warm bits.

So they need to be outside, of course, because you don’t want them inside your cool room, and the correct location of those is one thing we’ll talk about later.

So where is refrigeration energy used? Or where is refrigeration used in an energy system and refrigeration system?

Components energy consumption

Now, most of the energy is used by the compressor. Just kind of logical because it does all the hard work of compressing the vapor, but by no means is that the only energy that is being used.

We have the condenser fans, which I showed you before, and we have the evaporator fans, and they use a lot of energy because they tend to run all the time. And it always surprises people to realize

how much energy is actually being used, for example, by the evaporator fans. And it’s often very easy to save energy with the fans and more difficult to save it with the compressor.

So you go for the low hanging fruit. So that’s why fans are quite important in the discussion.

And then we have the defrost seeders, and this is where it’s kind of sad because we spend a lot of money in terms of energy to generate refrigeration, and about 20% of that is just used to make ice.

It doesn’t do us any good. It just makes ice in your fridge or it makes ice in your cool room, and then we have to spend more money on more power to defrost that.

This doesn’t happen in your home fridge. It just defrosts by itself. But in a supermarket or something, there’s actually electric heaters in there which melt the ice back down again. So you pay for the ice twice when you make it and when you melt it. So we can do things to minimize that defrost energy as well.

Commercial refrigeration and industrial refrigeration

Now, when it comes to refrigeration, there are two main areas, commercial refrigeration and industrial refrigeration.

commercial and industrial refrigeration

Like a dichotomous industry we have, the commercial refrigeration uses the air cooled systems you see on the left of the slide. It uses the freon refrigerants or the synthetic refrigerants, and it uses copper because copper is compatible with freons, and copper is relatively cheap and easy to install. You just have to solder it.

Ammonia is generally used for the big side of the industry. Ammonia doesn’t like copper, so you have to use steel. So you need a different set of trades people to do ammonia install.

So generally, that’s why it’s a dichotomous industry. You have the industrial installers using big industrial systems, using their bunch of trade people, and then you have the commercial industry.

Commercial refrigeration vs industrial refrigeration

Much of what we’ll be talking about today is commercial because that’s where most of us  encounter refrigeration. So commercial refrigeration of the left side of the table is usually the smaller systems stuff that you encounter.

So cool rooms, small freezer rooms, supermarkets, air conditioning. That’s all done with commercial refrigeration technology and it’s normally closed to the public because up to now, and I emphasize up to now, these refrigerants have been safe.

They haven’t been toxic and they are not flammable. That’s about to change. The gases that we currently use, and a couple of them listed there are multiple, and you see besides all those  funny numbers, 404a, 124a, 410a, 407C, 407F, 448A, and I can carry on.

That’s only 10% of the refrigerants out there. There are two other gases coming in. Carbon dioxide, believe it or not, is becoming a very important refrigerant, and hydrocarbons.

barbecue gas is actually quite a good refrigerant. And on the industrial side it’s mainly ammonia, but increasingly also carbon dioxide.

So we’re actually going to this interesting evolution in our industry is that one common refrigerant is being used on both sides, and this dichotomous refrigeration industry might come together, but that’s just a little aside.

So ammonia, you’ll find that in the big cold stores, you’ll find it out in the low margin areas in Melbourne where you have the big cold stores or the big meat works, and that’s where it’s used.

It’s very, very efficient, and that’s the reason why it’s being used. But normally, not where there’s public access because ammonia is highly toxic.

So you would not use ammonia in your domestic fridge, and you would not use ammonia in the supermarket.

OK, so that’s the commercial and industrial. So 95% of the walk-in cool rooms, which is the topic of this refrigeration masterclass, use commercial refrigeration.

Early refrigerants

through a number of evolution. But it started off with a whole lot of refrigerants that are using substances that were available at the time, what we call natural refrigerants.

Evolution use of refrigerant

So ammonia, carbon dioxide, ether. These gases were used initially. And then a little bit later, they started developing other things like sulfur dioxide and methyl chloride, which were very toxic and very aggressive.

So if you speak to the old generation of fridges, the guys who are now thoroughly retired,

they all tell you long stories about working with methyl chloride and sulfur dioxide, and a lot of fridges did get killed back then.

So it was nasty stuff. And because of that, the so-called safety refrigerants were developed CFCs, the HCFCs, and unfortunately, with them, many of the problems that we have today.

So this gives you a bit of an overview of the refrigerants that are still– or that ever were in use.

Refrigerants types

Any two categories the synthetic refrigerants and the natural refrigerants. So synthetics are substances that do not exist in nature, which is an important point because it means that there’s no mechanism to digest them when they escape, and that’s part of the reason why they have  environmental downsides because when they are released to the environment, they linger sometimes for hundreds of years.

Synthetic refrigerants and natural refrigerants

If you look at the table, all the substances with marked red have been phased out or are being phased out for those reasons. Refrigerants have two measures of damage to the environment.

The one is the ozone depleting potential or ODP. That was recognized back in the 80s, and the badly ozone depleting gases were banned 1989 already.

You remember the slip slop slap all, you might even be too young to remember the slip slop slap, but that was done to prevent protect us from the damage of the ozone layer, which is slowly busy mending now that we’ve done this.

So the CFCs and the HCFCs, they were banned back in 1989. And just recently, the HFCs which are the follow up refrigerants after that are also being banned.

And the reason for them being banned is because they have a high global warming potential. And at this point, I tend to give you an idea of the magnitude of that. R404a is a very good example.

It’s a gas that’s still commonly used in supermarkets. One kilogram of 404a, if it was a liquid, would fit into a large drink glass. One kilogram for 404a is equivalent to four tons of CO2 in it’s global warming potential.

Now, what is four tons of CO2? Four tons of CO2 is what your car with a big six cylinder car  

would emit if you drive it for 25,000. So that is a large amount of fuel that you have to consume in your car to generate the same as one kilogram of that gas, and a supermarket might have a ton of it in there, and 20% of it might leak every year.

So that’s why the impact of refrigeration, up to now on climate change, has been disproportionately large.

Refrigeration and air conditioning have an impact greater than all of transport for that reason alone, and that’s the reason why these gases are being phased out.

So all of those are now marked red, and I’ll explain on the next slide why. And the only synthetic refrigerants still left or that’s still being– well, it’s actually just come onto the market is a category called the HFOs.

They’re flammable. And then the category below that, which I’ve marked green, the naturals.

So ammonia. And I can say ammonia. Every one of you generates 18 grams of ammonia every day, whether you like it or not.

So ammonia is natural. Carbon dioxide– you exhale carbon dioxide all day. And then hydrocarbons, we use it on our barbecue every day if we were to barbecue every day.

Which refrigerant are you using?

I get interesting responses to that, but typically, this will be the answer. So most likely you’ll be using gases like R134a, 407F, 507, and 404a, and all of these are HFCs, and all of these are about to be phased down or phased out.

Or you could still be using R22, which is an HCFC, and that’s already been phased out. So if you’ve got R22, you better get rid of it fairly quickly or you may not get it.

And then there are a category of blended refrigerants that have come onto the market as intermediate stopgap solutions

So you might have 448a, which we’ll see you through for a number of years. However, if you’re lucky, your system might be on either carbon dioxide or something like R290, which is propane or ammonia.

As of 1st of January of this year of 2018, all HFCs have commenced to phase down. It’s the amount of gas that is imported into the country. We don’t manufacturer refrigerants in this country, so it’s quite easy for our government to control.

Refference:

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top