I recently grabbed a cheap (as in 70€) air cooler to chill a room (45m³).

Expectedly the inner workings of the cooler are quite basic, a pump circulates water from a reservoir through some kind of paper honeycomb structure in a waterfall-like manner. A ventilator sucks the hot air from the room through the honeycomb structure, where the air transfers its heat to the cold water.

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The cooler neither has a connection to a water pipe, nor is there an outlet for outgoing air.

Right now I am using cold tab water (around 10°C), but the cooler is not very effective. Leaving it on for three hours in the closed room yielded no change in room temperature, the water only got slightly warmer.

My ideas to improve efficiency:

  • Add salt to water and cool it down to around 0°C
  • Replace paper honeycombs with aluminum structure
  • Replace current pump (Hmax = 0.75m, Qmax = 260l/h) with better one to enhance flow through honeycombs

What else could I try to boost the cooling power of my air cooler?

  • What’s the humidity level in your environment and climate? Evaporative coolers need dry air to provide to cooling, essentially a desert like climate. If air is moist, it can’t evaporate water fast enough to provide cooling. To understand why evaporative cooling works, read the Wikipedia article
    – Tyson
    Commented Jul 21, 2018 at 14:16
  • I agree you seem unaware of the essential law of physics which makes this thing "work", specifically enthalpy of vaporization. Read up. Commented Jul 22, 2018 at 6:08

1 Answer 1


This type of evaporative cooler is incapable of reducing the temperature of an entire room. None of the interventions you list would improve the performance. Adding salt would corrode the device.

This device might provide some benefit if the air output is directed onto a single person.

  • OK, thanks for the info. I would like to follow that up with a quick question: What is the main difference to a fully fledged mobile AC unit (not a split unit) that uses a refrigerant like R290 or similar? Is it the efficiency of the recuperator?
    – pat3d3r
    Commented Jul 21, 2018 at 12:53
  • A full fledged mobile AC unit is a closed cycle heat pump which uses a lot more power than the simple open cycle water evaporator cooler. In dryer parts of the US evaporative coolers (aka water fans or swamp coolers) were used because they were cheaper to buy and to operate. They increase the humidity of the air in the house which is desirable in an arid or semi-arid climate. Modern refrigeration units have largely replaced them. Commented Jul 21, 2018 at 16:05
  • Although the refrigeration units are much more expensive to buy and maintain, they have gotten much more efficient, they are quiet, and they will really bring the temperature down without having a wind tunnel directed into the room. Commented Jul 21, 2018 at 16:08

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