World's Best Intercooler Water Spray, Part 1

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 droplets.

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 Pump

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 high pressure. 

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 injection pump...) Espresso Coffee Machines Carpet Cleaners Vacuum cleaners Irons   Ironing Presses Steam Generators Steam Cleaning Systems Disco Smoke Machines Medical Equipment Dental Equipment Water Gasifying Equipment Vending Machines Air Conditioners Cooling Systems

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 water-use-to-effective-cooling ratio.

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.

Power Supply

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 AUD$65.

But what about installing a 240V inverter in a car? We’ve already covered that in Mains Power for Your Car! and we’ll come back to the installation process in next week’s article.

The Nozzle

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 between.

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 reservoir).

Used with the Ulka pump, the following spray volumes are achieved:

¼ inch Tip Capacity Size	Orifice Diameter (mm)	Core Number	Approx flow with Ulka pump
			(ml/minute)	(litres/hour)
1	0.51	210	130	7.8
4	1.1	220	400	24

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.

How Cool? 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 exchanger. 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...

The Hose

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.

The Reservoir

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.

The System

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 spray

The Parts Component Supplier 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 optimism. 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 system!

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