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Comment by loeg | Hacker News Reader

Do the remaining alternatives work, and are they excessively expensive?

> Laboratory test equipment and centrifuges would receive a 12-year exemption as no alternatives are currently available.

Oh, so there are no remaining alternatives that work in these applications.

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Ethane (R-170) is a fine low-temperature refrigerant for lab equipment. The performance characteristics are at least as good as halocarbon refrigerants. The main drawback is flammability but propane has a similar concern and is already widely used in residential refrigerators and similar size systems.

From personal experience things using propane refrigerant seem to make a high pitched noise, I'm not sure if that's a property of the refrigerant or how devices using it are built.

There's no "reason" propane has to be louder but most propane refrigeration systems are used in industrial or cost-conscious applications where making the equipment quiet is less of a priority. When designing pumps it takes a non-trivial amount of engineering effort to ensure that the bulk of the noises emitted are above/below human hearing range.

>widely used in residential refrigerators and similar size systems.

Not in the US (because of the flammability), unless something's changed very recently.

In the last few years, the US has finally started allowing small appliances containing limited quantities of flammable refrigerants.

USA is kind of the exception. In much of the rest of the world, propane or butane are the norm in domestic refrigerators.

Most of the world doesn't build their residential buildings out of light wood frame :/

A fuel-air explosion will not be contained by a reasonable amount of concrete or masonry. The real safety lesson is to control sources of ignition and prevent the buildup of released gases.

If your house is on fire, you best GTFO no matter what kind of refrigerator you have.

American homes have plenty of propane/natgas appliances anyway, so what difference does one more make?

People usually store their propane tanks outdoors.

And they have natural gas piped into the house.

the volume in a pipe is a lot less than what you'd find in a tank, especially considering the pressure in said pipes is usually one tenth of a psi (.6 kPa)

In the US it's typically more like 0.25psi, I don't know about elsewhere.

But it's connected to what you might consider a tank of nearly infinite volume. It's flow rate limited, but it's fast enough to get an entire house to explosion concentration in much less than a day. Perhaps only an hour.

Point is that we humans manage to figure out how to harness things that might be dangerous when they're useful. And hydrocarbon refrigerants can be very useful so we might figure out how to deal with the relatively small danger they pose.

I don't disagree to be clear, I'm just saying treating it differently than a gas pipe isn't totally crazy. A punctured refrigerant line will empty in a few minutes, and it's next to a compressor that'll likely generate a spark when it kicks on. Even if it just means we need to use thicker line, lets do it.

Notably, Propane has almost identical refrigeration characteristics to R-22, so it was an easy drop-in replacement for systems designed for R-22 when that was banned.

I don't see why, they're hardly less flammable

In commercial applications you'll see R-290. It's often used in low temperature applications, like ice cream display freezers. I've seen them in gas stations and pizza shops quite a bit.

> Not in the US (because of the flammability), unless something's changed very recently.

I don't know when it changed but R-290 (propane) is allowed up to 13oz. My ice maker uses it. I believe it must also be sealed without service ports both to prevent leaks and prevent anyone from connecting normal A/C service equipment to the system. Service requires emptying the system then brazing service ports onto the fill pipes (which are left much longer than normal for this purpose).

I've seen pentane used in small refrigerators in the US.

There are a lot of alternatives that are cheap and perform well... but many of those have other safety concerns.

Some common examples are hydrocarbons or ammonia: https://en.wikipedia.org/wiki/Natural_refrigerant

Magnetic refrigeration seems (to a complete layman) to show promise.

https://en.wikipedia.org/wiki/Magnetic_refrigeration

I for one, hope that someone figures out a way to make this cost effective.

I think thermoacoustic coolers are another promising solution.

I remember reading about this in Popular Science in high school. Residential refrigerators powered by this technology by 2006! Twenty years after that magazine article I haven't seen any substantial progress towards a commercial product.

The problem with most alternative refrigerant technologies (magnetocaloric, electrocaloric, thermoelectric) is the same: the temperature deltas tend to be rather small, at best 25 C. That is roughly the thermal performance of the recently published "ionocaloric" cooling system; 20 C is very good for a magnetic system. For air conditioning, a delta of 25 C will just do (assuming outdoor temperature below 50 C!), but heat pumps may need to cross temperature gaps of 40 C or more.

Hydrocarbons work quite well and are (comparatively) minimal impact on climate change. There's been some paranoia about fires, particularly in automotive applications but it's actually a quite small amount needed to do the job.

The problem are large building air conditioning systems, grocery store chillers and industrial machines - they contain an awful lot of coolant and are very expensive to replace which means they tend to last for decades.

Ammonia (another dead simple molecule/process) is used in these services quite often, as far as I know.

From what I understand, at least here in Europe CO2 has been common in recent supermarket and similar installations.

One can buy large building air conditioners that use water to move heat around. There will still be refrigerant somewhere in the system, but there won’t be long refrigerant pipes anywhere.

I don’t know how popular these are. I have seen multiple condo buildings with a water source heat pump in each unit. The usual suspects (Mitsubishi, Daikin, etc) have hydronic systems with outdoor heat pumps on their websites. Chiltrix markets a small-building solution.

Why do centrifuges need refrigerant?

You probably have to sometimes spin biological materials that have to be kept cool.

Because they are temperature-controlled and contain a refrigeration unit.

In biological and medical applications, you might want to have the samples kept cool for stability. You'll transfer them from a fridge or on ice into the cooled centrifuge and back again after you've spun it down. Since in these big units the rotor is often a big hunk of anodised aluminium, it also helps maintain temperature stability.

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