This article was first published in 2005.
Sound the trumpets!
What we have here, ladies and gentlemen, is the best intercooler water spray
we have ever seen. We’re talking a mist of droplets so small that they evaporate
before they hit the ground. A mist with quite incredible cooling properties –
enough to make a conventional intercooler water spray look like the primitive
garden irrigation system it so often is. A pump that generates over 220 psi of
pressure while still being quiet. A professional quality brass nozzle with an
integral filter and non-drip check valve that develops an ultra-fine mist of
If you want the best results, forget windscreen washer pumps, headlight
washer pumps, and miniature garden irrigation nozzles. You simply have NEVER
seen an intercooler spray system like this.
The heart of this system is the pump – and what a pump it is! For years we’ve
been looking for a really good ultra-high pressure pump that will cope with
water. Fuel pumps won’t – they corrode internally. Multi-diaphragm pumps (as
used in boat and recreational vehicle potable water supply systems) can generate
good pressures (eg 60 psi) but they’re expensive and noisy. (Plus they usually
have a built-in pressure switch that requires the use of a bypass if the pump
isn’t to continually stop and start.) We’ve even looked at the Aquamist water
injection pump; it’s an absolute leader in high pressure, low volume 12V water
pumps – but the huge cost has always put us off.
But it’s the Aquamist pump that sent us off in the right direction. Rather
than using rotating rollers (like a high pressure fuel pump) or diaphragms
compressed one after the other (like a diaphragm pump), the Aquamist pump uses a
pulsating piston. The piston, powered by an electro-magnet, slides back and
forth, pushing ahead of it little bursts of water that soon add up to a very
And guess what? Just the same design of pump is used in espresso and
cappuccino coffee machines! Except instead of costing mega-bucks like the
Aquamist pump, you can have your very own Italian-made Ulka vibrating pump for
under AUD$106! (And if you live in Italy ,
probably for one-third of that.) So that it can be used in coffee machines
around the world, the Ulka pump is made in 110V AC and 220V AC models. But hold
on, what about using it in cars? Well, because of the technological advances
made in recent years with mains power inverters, for just an extra sixty
Australian bucks you can power it straight from the car battery!
Just AUD$166 for a durable pumping system capable of over 15 Bar (218 psi) –
and actually designed to pump water?! You can see why we’re excited.
The Ulka pump is not confined in OE use just to high pressure coffee
machines. Here’s a list of uses the manufacturer provides... perhaps we should add
‘intercooler water spray’! (And of course, the design makes for a superb water
Here’s the manufacturer’s performance specs for the Ulka E5EX pump. As can be
seen, flow drops off with increased pressure - but this means that you can
control the flow of the pump just by changing nozzle size... and the pump doesn’t
get overloaded. The curve also shows it’s possible to flow over 200cc a minute
at a pressure of 10 Bar (145 psi) and 100cc a minute at 15 bar (218 psi)!
When measured, the pump did even better than this, with a peak recorded
pressure of 25 Bar, or 360 psi!
These performance stats are just stunning. Why? Well, generally, the higher
the pressure you can run, the smaller will be the droplet size coming from a
high quality nozzle. We’re getting ahead of ourselves a little, but flowing a
low volume of water at a very high pressure gives fantastic efficiency in the
In addition to its very high pressure, the Ulka pump has another attribute –
it can provide enough suction to draw up water from a reservoir mounted below
it. This feature gives greater flexibility in pump mounting position.
As mentioned above, the Ulka pump needs an AC high voltage power supply to
operate. However, it draws only 50 watts and so pretty well any 12>240V
inverter will work the pump. The one we selected from the local auto parts store
was branded ‘Pro User’ and provides up to 150W continuous and 300W peak – far
more than required in this application. Further, the inverter includes low
voltage, over-temperature and short-circuit protection. Despite its low-buck
brand name, inside it looks good and in service it performs faultlessly. It cost
But what about installing a 240V inverter in a car? We’ve already covered
Mains Power for Your Car! and we’ll come
back to the installation process in next week’s article.
The Spraying Systems Company of the
US make amongst
the world’s best water spray nozzles. They’ve got nozzles sized to flow from
hundreds of litres a minute to a few millilitres a minute. And everything in
The nozzles used in this application are in the Unijet small capacity range.
These assemblies consist of a ¼ inch TT male body spray nozzle holder, a screen
strainer incorporating a check valve, a spray tip and a tip retainer. All the
components are top quality brass.
The check valve stops the valve from dribbling when the pump is off (even
if the nozzle is located below the level of the pump) and the strainer stops the
tip being blocked by foreign material that might be contained in the water
(however, you should still always strain the water you’re adding to the
Used with the Ulka pump, the following spray volumes are achieved:
¼ inch Tip Capacity Size
Orifice Diameter (mm)
Approx flow with Ulka pump
Note: the factory nomenclature used for these tips can be confusing. These
part numbers are from Page 255 of the Spraying Systems 60B-M catalog (current at
the time of writing).
The two nozzles shown here provide excellent atomisation without having spray
orifices so small that they easily block. (However, the Spraying Systems
strainer/check valve that fits inside the nozzle should always be used.) If you
need a larger flow, we suggest you use multiple nozzles.
The nozzle assembly (including strainer and cap) costs AUD$12 and the
precision nozzles are $21 each.
Evaporating a kilogram (ie a litre) of water requires 2257 kilo-joules of
energy – and that’s a lot! If the nozzle flows 400 ml/minute, and if all the
water evaporates, each minute 903 kilo-joules of energy are extracted. One joule
per second is the equivalent of 1 watt, so fully evaporating 400 ml/min of water
provides a cooling power of 15 kilowatts! Even a 130 ml/min spray provides a
potential cooling power of just under 5kW.
The key point is that the water must
evaporate – it is this change of state from water to a gas which absorbs the
energy. If the water droplets do not evaporate, they basically provide almost no
cooling performance. And the key to getting water to evaporate is to use very
small drops – an atomised mist – which dramatically increases the
surface-area-to-volume-ratio of each drop, promoting evaporation.
In addition to drop size, the rate of evaporation will also depend on the
relative humidity of the air (if you like, an indicator of how much ‘room’ there
is left in the air for evaporated water) and the temperature of the heat
With a good enough spray, there is no technical reason why the temperature of
the intercooler cannot be brought lower than ambient. After all, that’s how
evaporative air conditioners work...
It’s possible to get barbed hose fittings for both the nozzle and the pump
and connect them together with high pressure hose held on with hose-clamps.
However, we found in bench testing that time after time, the hose would blow-off
either the pump or nozzle – we’re talking high pressure here! You may be able to
get away with running two hose-clamps at each end but to ensure reliability, we
chose instead to get an industrial hose with high pressure fittings made up to
suit. This cost AUD$45.
The feed hose to the pump handles effectively no pressure and so any hose
that is durable enough to withstand the heat of the engine bay can be used.
Modern engine bays are usually too cramped to fit in a dedicated water spray
container, and so we made use of the existing windscreen washer spray reservoir.
In the guinea pig vehicle this is a substantial 6 litres – enough to run the
smaller of the two spray nozzles continuously for over 45 minutes! Even with the
windscreen washer drawing from the same container, with sophisticated triggering
of the spray, refills should only be needed every two or three tanks of fuel.
Including the pump, inverter, nozzle and high pressure hose, the ultra high
pressure spray will set you back about AUD$250. Oh yes, and you need a way of
switching the system on and off.
Sound expensive? Not when you start looking at the alternatives - compared to
the hassle and cost of an intercooler upgrade, a really high quality spray can
save you a lot of days and dollars...
Next week: installing the
Ulka E5EX coffee machine pump
In Australia, Jumbo Coffee on 02 9666 6114
12 > 240V AC 150W inverter
Auto parts accessory shop
Spraying Systems Unijet ¼ inch TT male body spray nozzle holder, screen
strainer, spray tip and a tip
In Australia, Spraying Systems on 03 93180511
Custom high pressure connecting hose
Industrial hose supplier eg EnZed
It’s now five years since we first wrote about a sophisticated intercooler
water spray. The series, which starts at
Intelligent Intercooler Water Spray - Part 1,
covered the development of the Labtronics/AutoSpeed intelligent intercooler
water spray controller. At the time we were pretty damn happy with the
intelligent controller – and its success over the years since has confirmed our
But we weren’t so happy with the spray hardware – especially the pump, which
comprised a good quality windscreen washer pump. (We also mentioned the ‘heavy
duty’ boat pressure pumps, capable of about 45 psi – but they were noisy and
expensive.) Well, now we have the pump hardware to match the rest of the