I wrote this in the summer of 2019, but started to see blanket adverts for the device – or identical devices – in 2020. The prices are ridiculous in some cases.
Be aware that the device does not work to anything like the levels these ads claim. And also note that it applies to all those “New Air Conditioner Needs No Installation” ads you will be seeing on social media and newsfeeds. So be careful. The original article follows.
Early in July 2019, I saw the Chillmax Air advertised on TV in one of those shouty ads. Then, the same evening, I was shopping in Asda and saw it on display. I am an idiot for things like this, and bought it on impulse so I could test whether it worked or not.
As a chemist, I’m well aware that in order to cool a large space effectively you’re going to need something with a big fan and a special refrigerant. In practical terms, that means a fairly large device holding a motor-driven compressor, a closed radiator filled with the refrigerant, a fan to suck air in and blow it across the radiator, and a wide exhaust pipe through the wall or window to get rid of the “removed heat”. In many cases, you also need to collect or drain the condensed water that comes out of the air as it cools. A typical air conditioner for a small or medium-sized room will be about the size of bedside cabinet. The Chillmax Air is not much bigger than six CD cases glued into a cube.
If you’ve used a normal desk fan you will know that you only feel “cooler” if you’re sweating a bit. That’s because the fan evaporates your sweat as it pushes air over it, and that evaporation is accompanied by a small cooling effect – it’s called “evaporative cooling”. If you’re not sweating, you don’t feel any cooler. Conversely, if the surrounding air is very humid, then no matter how powerful your fan is, you will feel little or no cooling because sweat can only evaporate if the air has capacity to hold additional moisture (I’ll explain that a bit more later, because it is really the factor that determines whether the Chillmax is any good).
As an aside, many liquids exhibit the evaporative cooling effect. In the case of diethyl ether (the stuff they used to use as an anaesthetic), if you force it to evaporate very quickly you can even freeze water (if you do it properly). However, ether is both highly flammable and toxic, so apart from demonstrating it in the school lab (where I remember it from, along with the massive headache it gave me), it doesn’t have much practical application these days. Early refrigerators used it, which was spectacularly dangerous.
The Chillmax Air uses the evaporative cooling effect of water, and this is much less than with ether – similar to sweat, in fact. The unit consists of a reservoir at the top, which you fill with normal tap water, and this drips down on to a radiator unit which has ten sideways-stacked fibre panels in it through which a fan blows air. The water evaporates from the fibre panels, and the evaporatively cooled air comes out through the front grille. According to the marketing spiel on the TV ads, you’d be forgiven for thinking you’re going to get frostbite if you sit too close. I knew this wasn’t going to happen, but I wanted to know just how effective the Chillmax was.
When I first set it up and turned it on, the first thing I noticed was that the fan is quite powerful, so you get a good flow of air directed at you – but note that that it’s only about 5″ in diameter, so it can’t beat a proper desk fan for air flow. The air did seem a little cooler compared with what my desk fan was blowing at me, but it also felt ‘softer’ – that’s very important, and I’ll explain later. But the big question was how much cooler was the exhaust air?
I fired up my trusty data logger and left it in front of my desk fan for 30 minutes for the control data. Then I moved it and suspended it in front of the Chillmax for the same period of time. This is what it recorded (red line is the switch over point).
The ambient temperature where I ran the test was about 29ºC. The Chillmax brought this down by about 4ºC.
So, the Chillmax definitely cools the air that passes through it. Let’s work on the assumption that it would be able to get the same 4ºC drop no matter what the ambient temperature was. If your room is 38ºC, pulling it down to 34ºC still means it’s bloody hot. And also note that since the Chillmax is physically so small, the cooling is very localised – it won’t cool a room down.
But there’s more to it than that. I mentioned that the exhaust from the Chillmax felt ‘softer’. I knew what it was, but my data logger shows it in numbers.
These are is the data for relative humidity recorded at the same time as the temperature measurement, above (red line is the switch over). The humidity went up dramatically.
As I’ve already explained, the Chillmax works by evaporating water on fibrous panels by forcing air across them. That water has got to go somewhere, and in this case it comes out as vapour in the cooled air. In the right light, you can actually see it – it’s essentially fog. And just like when it’s foggy outside, and everywhere gets damp, this vapour can condense on surfaces. My data logger collected some and began to drip during the test, and I have since discovered that it also condenses on the front grille and can drip periodically, so you’d need to be careful what you had underneath it if you placed it on a shelf. The fan is quite powerful enough to project the drips forward slightly when they drop.
The ambient humidity in the room where I did the test was about 44%RH. The Chillmax sent that up to over 70%RH.
It’s this elevation of the humidity of the cooled air which really brings into question whether the Chillmax is worth the investment. You’re probably aware that you can have a hot summer day in the high 20s where it is pleasant and comfortable, but a cooler and overcast day might be horribly sticky – or muggy. That’s because of the humidity, or water vapour in the air.
The amount of water vapour that air can hold varies with the temperature. Once you reach the maximum, any extra vapour condenses out – misted up windows, dampness, even drips and pools of moisture on window sills or under lamp posts. Cold air can only hold a small amount of moisture before condensation occurs, but hot air can carry much more. Although ‘humidity’ technically refers to the amount of water in the air, the figure most people are referring to when they say it is relative humidity. This is the amount of moisture in the air expressed as a percentage of the maximum amount it could hold at that temperature, hence the units %RH. It’s a very complicated subject, but the important factor for us here is that when it is warm or hot, higher relative humidity is uncomfortable. Indeed, you may have seen weather forecasts where they give the actual temperature and the ‘feels like’ equivalent – that’s a reference to the ‘heat index’, which takes into account the effect of the %RH. Here’s a graphical chart for that.
As an example, if the temperature is 30ºC and 50%RH, it will feel like 31ºC. If the humidity goes up to 80%RH, then it will feel like 38ºC. If the temperature is 35ºC at 50%RH, it will feel like 41ºC. But if the humidity goes up to 80%RH, it’ll feel like 57ºC! The calculation for this is complex (you should see how long my Excel formula for it is) and non-linear, and the increase in ‘feels like’ is greater at higher temperatures. It also contains an element of opinion/perception, which is why there’s no point using numbers above about 60ºC, but it is what the forecasters use. Incidentally, the official health designations for the colours are: yellow – caution; amber – extreme caution; orange – danger; and red – extreme danger.
This is where the problems come in for the Chillmax Air. If it’s 35ºC and 40%RH, it’ll feel like 37ºC. Cool the air to 31ºC and send the humidity up to 80%RH, and it’ll feel like 41ºC. So it’s actually hotter in terms of comfort. Do the same comparison when the surrounding temperature is 38ºC, and the ‘feels like’ goes from 43ºC to over 50ºC!
At lower temperatures the Chillmax will produce a slight net cooling effect, but at higher temperatures – the ones you likely to be wanting to use it in – it makes things worse. But even at these slightly lower temperatures, the full 4ºC drop is cut somewhat simply because higher humidity makes it feel warmer.
Proper air conditioners remove water from the air they cool – so much so that the best ones have humidifiers in them to stop the cooled air from being too dry. This removal of moisture is why the air from proper air conditioners feels crisp, as opposed to the ‘softness’ of moist air. The Chillmax does the opposite of normal A/Cs, and adds moisture.
Aesthetically speaking, the Chillmax is a cube – more or less – about 15cm along each side. There are two buttons on the top rear, one which changes the fan speed to one of three settings (or off), with a blue LED for each, and another button that turns the night light on or off. There’s a flap on the top front through which you add the water. The radiator system is a plastic-framed insert which you access by pulling the front grille out. It slots in and out easily. You can’t officially replace the fibre inserts in the radiator, but you can buy the whole radiator assembly from JML for £15. My only major gripe is the power cable. The jack plug that goes into the Chillmax is quite stubby and doesn’t go into the socket very far, so it is easy to dislodge it. However, the cable itself is quite long, and the mains plug is a moulded UK type.
JML claims the Chillmax can run for up to 10 hours per fill, but this is undoubtedly on the lowest of the three fan speeds. At top speed, it runs out in less than three hours. To be fair to it, you do still get a cooling effect on the lowest speed, and since the water lasts longer then, less of it will be getting pumped into the air at any one time. JML sells the humidification as a positive without relating it to the comfort relationship between temperature and %RH, but note what I said above. If you want to cool down in humid weather, it isn’t just the temperature that needs to come down, certainly not a mere 4ºC drop, and definitely not if that means pushing high humidity even higher.
Does it really work?
Well, it does cool the air by a few degrees, but it also sends the humidity up. So if it is already humid and sticky, the cooling effect is completely cancelled out by the extra stickiness. If it’s really hot, then no, it doesn’t work. However, to be fair to it, at lower temperatures (under about 26ºC) it does produce a slight cooling effect.
Will it cool more if I use ice water?
No. Evaporative coolers are not influenced significantly by the temperature of the water used in them. The temperature of the air that comes out depends on the temperature (and humidity) of the air going in, and the science of evaporation. Only this evaporation results in the cooling effect observed.
Will it cool more if I put the filter in the freezer?
It might – until the filters defrost. And when it’s over 30ºC they’ll defrost in minutes. Passing warm air over ice will obviously cool it, but once the ice is gone you’re back to evaporative cooling, and as I explained above – irrespective of what other people say – evaporative cooling depends on the temperature and humidity of the inlet air, and the amount of water being evaporated. You cannot overrule science with opinion.
The other thing is that if the filters are iced up, there will be melt water which won’t evaporate, and that will come out of the front as liquid.
Can I use it to cool my PC?
Someone found this article on the search term “jml chillmax air for pc cooling”. If they mean what I think they mean, no, there is absolutely no way you want to be blowing damp air into your PC.
Can you get larger versions?
You can certainly get larger evaporative coolers. The working principle is that the larger the surface area of water, and the greater the airflow over that water, then the greater will be the possible drop in temperature at the front end. However, cooling effectiveness is influenced greatly by the RH of the air going in.
If the air is very dry, then a large evaporative cooler might be able to drop inlet air at 30ºC down by as much as 10ºC. However, if the inlet air is very humid, the temperature drop could be as little as 1ºC. In the UK, the realistic temperature drop you could expect on a non-humid day for a large cooler would be around 5-6ºC, but on a sticky day you’d only get about a 3ºC drop.
Suppliers of these devices say that they need good ventilation or extraction, and I would imagine that’s so the humid air can escape. If you’re evaporating more water to get better cooling on larger devices, you’re also producing a lot more water vapour. Be careful if you read any of the reviews – people may have noticed cooling in already cooler conditions, but trust me – if it’s very warm and humid, you will not notice any effect.
People say it works
Be careful when you read those one-line reviews. If you test it when it’s only 20ºC outside – as many of these people have – then yes, it blows noticeably cooler air at you. But science is involved, and at temperatures around 26ºC the effect will be negligible, and above that it will actually make you feel hotter. The fact that it increases humidity is the key factor. Remember that the reason you even found this article was probably because it’s over 30ºC outside – the more above that it is, then the more hits I get.
So, does the Chillmax work?
It cools the inlet air by a few degrees at best. In that sense, it works. But it sends the humidity of that air up considerably, and this cancels out the benefits of the cooling effect in the instances where I tried it (i.e. when it is very hot). The ‘heat index’ is the key issue, as explained above.
Only the air being directed at you is cooler. The device cannot cool down a room. It’s far too small for that.
The increased humidity does produce condensation, so you have to be careful to keep it away from electrical sockets where it might drip on them. The cooler also contains a fair volume of water when full, so you don’t want to knock it over.