Compressed Air Aftercoolers

Air AfterCooler – 70 CFMWhat are compressed air aftercoolers and why are they required? Find out everything you need to know about aftercoolers in this article, including the two most common types, why they’re important, and their role within an air compressor system.

What Is An Aftercooler?

An aftercooler is a mechanical heat exchanger designed to remove the heat-of-compression from a compressed air stream and to condition the air so it can be used in air-operated equipment.

A compressed air aftercooler has three primary functions:

  • Cool air discharged from air compressor via a heat exchanger
  • Reduce compressed air moisture level
  • Protect downstream equipment from excessive heat and moisture

Why Are Air Aftercoolers Required?

Regardless of the type of compressor being used, the compressed air discharged from that air compressor is going to be hot. That temperature will vary according to the type of compressor being used.

Typical Compressor Average Outlet Temperatures:

Oil-Injected Rotary Screw        200°F
Oil-Free Rotary Screw              350°F
2-Stage Reciprocating              300°F
Centrifugal                                 225°F

High-temperature air is typically not usable in air-operated equipment, as heat has a detrimental impact on equipment lubrication and sealing materials. Hot air also contains large quantities of moisture vapor which, as it condenses, contributes to rust, scale build-up, washing out of lubricant and possible freezing issues.

Water exists in a vapor state in all atmospheric air (relative humidity) and as the air is drawn into a compressor and pressurized, this moisture is concentrated in each cubic foot. Due to the high temperature of the air, the moisture remains in a vapor state (above the dew point temperature).

The dewpoint is the temperature at which this air becomes saturated at 100% of its capacity to hold water in a vapor state and, with any additional cooling, must release excess moisture as a liquid. A general rule is that for every 20°F rise in temperature the air can hold twice the moisture load in a vapor state above the dewpoint.

Source: Engineering ToolBox /

As the compressed air cools this water vapor condenses into a liquid form and is removed from the air stream. As an example, if an aftercooler is not used, a 200 cubic feet per minute (CFM) compressor operating at 100 psig can introduce as much as 45 gallons of water into the compressed air system each day.

Types Of Aftercoolers

The two most common types of aftercoolers are air-cooled and water-cooled.

aftercoolerMost air-cooled aftercoolers are sized to cool the compressed air to within 15°F to 20°F of ambient cooling air temperature (approach temperature). As the compressed air cools, up to 75% of the water vapor present condenses to a liquid and can be removed from the system.

A moisture separator, installed at the discharge of the aftercooler, mechanically removes most of the liquid moisture and solids from the compressed air. Utilizing centrifugal force, and in some cases baffle plates, moisture and solids collect at the bottom of the moisture separator. An automatic drain should be used to remove the moisture and solids. Similar to the air-cooled version, the typical water-cooled approach temperature is between 10°F and 15°F.

In stationary compressor installations, where cooling water is available, water-cooled aftercoolers are often used. There are a few advantages to using water as the cooling media:

  • Water has little seasonal fluctuation in temperature
  • Large volumes of cold water can be used
  • Cold water can efficiently approach the ambient air temperature, which eliminates condensation downstream

Air-Cooled Aftercooler

air-cooled aftercooler

Source: Parker /

Air-cooled aftercoolers use ambient air to cool the hot compressed air. The compressed air enters the air-cooled aftercooler. The compressed air travels through either the spiral finned tube coil or a plate-fin coil design of the aftercooler while ambient air is forced over the cooler by a motor-driven fan. The cooler, ambient air removes heat from the compressed air. Liquid water forms as the compressed air cools. The moisture is removed by the moisture separator and drain valve.

Belt Guard Air-Cooled Aftercooler


Source: AKG /

A belt guard air-cooled aftercooler mounts to the compressor’s v-belt guard. The compressor’s belt pulley has fins designed to force ambient air over the compressor and air-cooled aftercooler. The air passing over the aftercooler facilitates the heat transfer. The pulley also sends air over the compressor helping maintain proper operating temperature.

Water-Cooled Aftercooler


Source: Parker /

Water-cooled aftercoolers come in different styles. The most common style for compressed air service is a Shell and Tube Heat Exchanger/Aftercooler. This aftercooler consists of a shell with a bundle of tubes fitted inside. Typically, the compressed air flows through the tubes in one direction as water flows through the shell side in the opposite direction (counter-flow). Heat from the compressed air is transferred to the water. Liquid water forms as the compressed air cools. The moisture is removed by the moisture separator and drain valve.

How To Size An Aftercooler

Coolers are usually sized with a CTD (Cold Temperature Difference) of 10°F, 15°F or 20°F. This means that the compressed air temperature at the outlet of the aftercooler will be equal to the cooling medium temperature plus the CTD when sized for the specified inlet air temperature and flow. The lower that temperature needs to be, the larger the aftercooler needs to be.

The required compressed air temperature is determined by other components downstream in the system. It is critical that each individual component’s maximum temperature is determined and considered to discover the true temperature requirements for the aftercooler.

operating-temps air compressor components

Disclaimer: Individual air compressor components may vary from the chart above; always check with the component manufacturer for specs and tolerances, including typical and maximum operating temperatures.

Compressor manufacturers may include integral aftercoolers as a component of the compressor system. Otherwise, a stand-alone or freestanding aftercooler is a separate unit installed downstream of the compressor.

The aftercooler should be located as close as possible to the discharge of the compressor.

Want to learn more about air compressors? Check out our other articles!

Top Four Trends in Commercial Van Upfitting and How to Capitalize on Them

If you’re a commercial van upfitter, you’ve likely seen a growing number of customers who’ve traditionally selected a pickup or service body truck for a mobile service application, who are now taking a second look at using a van for that job.

That’s because not long ago, in 2008, there were few commercial van options available in the North American market — three full-size vans (Ford E-Series, Mercedes Sprinter, and Chevrolet Express/ GMC Savana) and one compact van (Chevrolet Uplander cargo). Today, that number has more than doubled to 10 van models, offering a much wider range of roof heights, wheelbases, payload capacities, and engines for fleet managers to choose from.

“We’ve definitely noticed an uptick of some customers switching from pickup trucks to vans because there is more choice now, especially with the new small vans and euro-style full-size vans that have entered the market the past few years,” said Jay Cowie, product manager at Ranger Design, a commercial van upfit manufacturer based in Ontario, New York.

With the influx of new van models, how can you seize this opportunity to sell more commercial van products and services? Tailor your offerings to capitalize on these four trends in commercial van upfits.

Trend #1: Rightsizing the Van to the Job

“Fleets are taking a more strategic approach to their business, focused on selecting the right-size van because now there’s more choice,” said Cowie. “Customers aren’t stuck with a one-size-fits-all van, which may be inefficient for certain applications. With greater choice, they can more effectively tailor vehicle selection to increase efficiencies and lower operational costs.”


How can upfitters capitalize on this trend?

  • Expand upfit offerings to fit each available van model
  • Offer modular or adjustable cargo management systems so that technicians can personalize (or right-size) the upfit to their unique needs and workflows in the field.
  • Reimagine how the increased cargo area inside high-roof vans can be optimized — to create new upfit designs that boost worker efficiency and productivity.

Trend #2: Taking Weight Out of Upfits

“Because some of the new vans are bigger and taller with more cargo area, you can fit a lot more gear in it,” said Cowie. “And the more stuff in the van, comes more weight, which increases the risk of overloading the van. So, we’re seeing a shift toward using lighter-weight materials in upfits to increase legal payload capacity.”

Cowie said that Ranger Designs incorporates aluminum and composite materials to reduce overall upfit weight, depending on what mix of materials is best for the customer’s functionality, durability and budget requirements.

How can upfitters capitalize on this trend?

  • Offer lighter-weight upfit options where the customer’s application allows.
  • Help customers assess the cost-benefit of “lightweighting” in terms of productivity gains from increased payload capacity or the potential to “downsize” the vehicle and reduce acquisition costs.

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Trend #3: Higher Demand for Ergonomic Upfits

According to the U.S. Occupational Safety and Health Administration (OSHA), work-related musculoskeletal disorders (MSDs) — typically caused by awkward movements, heavy lifting, and repetitive motion — account for 34 percent of all lost workdays, which can get very expensive for employers.

So, a growing number of fleet managers are looking to equip their vehicles with upfits that improve ergonomics to protect their technicians’ health — and their organization’s bottom line.

“[At Adrian Steel], we start by observing how the [technicians] do their work, so we can create a process flow of the types of equipment they need to access most often and what they need less often,” said Jeff Langley, fleet account executive at Adrian Steel, a manufacturer of commercial van accessories and truck equipment, headquartered in Adrian, Michigan. “We’ll then design an upfit system that positions those high-use items where they can be accessed quickly and easily, so workers can be more safe and productive when performing their job.”

Also, the upfit products themselves can be designed with ergonomics in mind. Take, for example, a bulkhead (between the cabin and cargo areas) that’s contoured to allow the driver seat to recline a few degrees further than a standard bulkhead, improving driver comfort and reducing risk of lower back fatigue. Another example is a drop-down ladder rack, which is especially helpful with the taller Euro-style vans because it enables workers to load and unload ladders from the side of the van, while standing safely at ground level, instead of having to strain and lift awkwardly to load a heavy ladder onto a standard roof rack.

How can upfitters capitalize on this trend?

  • Educate customers on more ergonomic options to standard upfits, such as drop-down ladder racks, contoured bulkheads, grab handles, etc.
  • Study how the vehicle is intended to be used in the field to uncover new ideas for designing upfits that help improve workflow and ergonomics.

Trend #4: Increased Demand for Mobile Power

“We’re seeing a trend toward fleets wanting van interiors that offer a more productive mobile workplace, with increased demand for power ports to run laptops, charge mobile devices, and operate electric tools,” said Langley with Adrian Steel.

VMAC UNDERHOOD 30CFM Air Compressor in VanAt VMAC, we’re seeing similar growth in demand for air power in vans – for fleets that traditionally use pickups or service body trucks to run high-powered air tools, such as impact guns for breaking off heavy-duty lug nuts in a mobile tire service application.

The challenge has been that conventional air compressor systems available for vans — electric drive and gas/diesel drive compressors — are either too underpowered or take up too much cargo space (and weight) to be useful for most mobile service applications. So, the VMAC engineering team has developed the UNDERHOOD 40 CFM air compressor (40 cfm/ 100-150 psi), designed specifically for the commercial van market, with a compact rotary screw compressor. This system is powered by the vehicle’s engine to generate sufficient air power for a wide range of heavy-duty air tools, while minimizing the system’s footprint and weight inside the van’s cargo area.

How can upfitters capitalize on this trend?

  • Expand your product offerings and expertise to account for your customers’ mobile power needs for commercial vans, in terms of electrification and air power.
  • Help customers strike the right balance between maximizing onboard power, while minimizing the system’s weight and impact on cargo capacity.

The Bottom Line

With today’s commercial van landscape, opportunities abound for upfitters that serve the mobile service market. So, as you evaluate your product portfolio, look for any gaps that, if you were to fill them, could open up exciting new revenue streams — and make your company more valuable to customers.

Want to learn more? Read about your air compressor options for service vans!

If you have any questions about this article or anything mobile compressor related, please contact us.

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Factors to consider when purchasing a compressor for your mobile application

It’s time to buy a compressor for your mobile service truck application.  You’ve figured out what type of compressor and how much air flow and pressure you need as well as how it will affect the load capacity of your truck.  Now it’s simply where you can buy that compressor the at the lowest cost, right?  Well not really.  Besides the installation time, there are some important installation details to consider, depending on the type of compressor you’ve chosen and what type of work you’ll be doing. Continue reading “Factors to consider when purchasing a compressor for your mobile application”