Intelligent Compressed Air: Refrigerant Dryers and How They Work

We’ve seen in recent blogs that Compressed Air Dryers are an important part of a compressed air system, to remove water and moisture to prevent condensation further downstream in the system.  Moisture laden compressed air can cause issues such as increased wear of moving parts due to lubrication removal, formation of rust in piping and equipment, quality defects in painting processes, and frozen pipes in colder climates.  The three main types of dryers are – Refrigerant, Desiccant, and Membrane. For this blog, we will review the basics of the Refrigerant type of dryer.

All atmospheric air that a compressed air system takes in contains water vapor, which is naturally present in the air.  At 75°F and 75% relative humidity, 20 gallons of water will enter a typical 25 hp compressor in a 24 hour period of operation.  When the the air is compressed, the water becomes concentrated and because the air is heated due to the compression, the water remains in vapor form.  Warmer air is able to hold more water vapor, and generally an increase in temperature of 20°F results in a doubling of amount of moisture the air can hold. The problem is that further downstream in the system, the air cools, and the vapor begins to condense into water droplets. To avoid this issue, a dryer is used.

Refrigerated Dryer

Fundamental Schematic of Refrigerant-Type Dryer

Refrigerant Type dryers cool the air to remove the condensed moisture and then the air is reheated and discharged.  When the air leaves the compressor aftercooler and moisture separator (which removes the initial condensed moisture) the air is typically saturated, meaning it cannot hold anymore water vapor.  Any further cooling of the air will cause the moisture to condense and drop out.  The Refrigerant drying process is to cool the air to 35-40°F and then remove the condensed moisture.  The air is then reheated via an air to air heat exchanger (which utilizes the heat of the incoming compressed air) and then discharged.  The dewpoint of the air is 35-40°F which is sufficient for most general industrial plant air applications.  As long as the compressed air stays above the 35-40°F temperature, no further condensation will occur.

The typical advantages of Refrigerated Dryers are-

  1.  – Low initial capital cost
  2.  – Relatively low operating cost
  3.  – Low maintenance costs

If you have questions about getting the most from your compressed air system, or would like to talk about any EXAIR Intelligent Compressed Air® Product, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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EXAIR Cabinet Cooler vs. Air-To-Air Heat Exchanger

The EXAIR Cabinet Cooler family.

At EXAIR we’ve been providing enclosure cooling solutions for decades, and in many cases those cooling solutions have remained in place for decades as well.  In the time we’ve been in the market with industrial enclosure cooling solutions we’ve encountered a number of alternative means for enclosure cooling.  One of those methods is an air-to-air heat exchanger.

An air-to-air heat exchanger uses the temperature differential between the ambient air surrounding an enclosure and the hot air inside an enclosure to create a cooling effect.  A closed loop system exchanges the heat inside the enclosure with the outside air in an effort to maintain a set internal temperature.  The heat exchange of most air-to-air unit relies on a heat pipe, a heat-transfer device which converts an internal refrigerant liquid into vapor by placing one end of the pipe in contact with the hot environment.  The heated vapor travels to the other end of the pipe which is in contact with a cooler environment.  The vapor condenses back into a liquid (releasing latent heat) and returning to the hot end of the pipe and the cycle repeats.  All in all, a clever solution.

But, this type of a solution does give some cause for concern, especially when considering their use in an industrial environment.  Here are the key points to keep in mind when comparing an air-to-air cooler to an EXAIR Cabinet Cooler.

Required temperature differential based on ambient air temp

An air-to-air heat exchange relies on the ΔT between the ambient air temperature and the internal enclosure air temperature to produce cooling.  If this ΔT is low, or the ambient temperature rises, cooling is diminished.  This means that as the temperatures in your facility begin to rise, air-to-air heat exchangers become less and less effective.  Larger air-to-air heat exchangers can be used, but these may be even larger than the enclosure itself.

EXAIR Cabinet Coolers rely on the ΔT between the cold air temperature from the Cabinet Cooler (normally ~20°F) and the desired internal enclosure temperature (normally 95°F).  The cold air temperature from the Cabinet Cooler is unaffected by increases in ambient temperatures.  The large ΔT and high volume cold air flow produced by a Cabinet Cooler results in more cooling capacity.  And, we can increase cooling capacity from a Cabinet Cooler without increasing its physical footprint, which is already much, much smaller than an air-to-air type of unit.

 

Cooling in high temperature environments

High Temperatures are no problem for EXAIR Cabinet Coolers

Due to their nature of operation, an air-to-air heat exchanger must have an ambient temperature which is lower than the desired internal temperature of the enclosure.  If the ambient air has a higher temperature, air-to-air units provide zero cooling.

Cabinet Coolers, on the other hand, can be used in hot, high temperature environments up to 200°F (93°C).

 

Cooling in dirty environments

An EXAIR NEMA 12 Cabinet Cooler in an extremely dirty environment. Still operating after over 7 years, without any maintenance.

Dirt in the ambient environment will impact cooling performance with an air-to-air heat exchanger.  In order for the air-to-air unit to effectively remove heat, the heat pipe must have access to ambient air.  With any exposure to the ambient environment comes the possibility for the ambient end of the heat pipe to become covered in ambient contaminants such as dust.  This dust will create an insulation barrier between the heat pipe and the ambient air, decreasing the ability for the heat pipe to condense the vapors within.  Because of this, most air-to-air devices use filters to separate the heat pipe from the ambient environment.  But, when these filters become clogged, access to ambient temperatures are reduced, and cooling capacity of the air-to-air unit reduces as well.

Cabinet Coolers have no problem operating in dirty environments.  In fact, it is one of their strengths.  Without any moving parts to wear out or any need to contact ambient air for cooling purposes, a dirty environment poses no problems.  In fact, check out this blog post (and this one) about EXAIR Cabinet Coolers operating maintenance free for years in dirty environments.

 

Size and time required to install

Air-to-air heat exchangers vary in size, but even the smallest units can have large dimensions.  Many applications have limited space on the enclosure, and a large, bulky solution can be prohibitive.  Couple this with the time and modification required to the enclosure to install a large air-to-air unit, and the “solution” may end up bringing additional problems.

Another key aspect of the Cabinet Cooler is its size.  Small, compact, and easy to mount on the top or side of an enclosure, Cabinet Coolers install in minutes to remove overheating problems.  Check out this video to see how simple Cabinet Coolers are to install.

Rising ambient temperatures translate to less natural heat transfer into the ambient environment.  As temperatures rise and overheating electrical components becomes a concern, remember EXAIR Cabinet Coolers as a viable solution.  If you have any questions about how an EXAIR Cabinet Cooler can solve problems in your facility, contact an EXAIR Application Engineer.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

Cabinet Cooler Systems Simple, Quick, and Easy

In this corner EXAIR Cabinet Cooler

In this corner:  EXAIR Cabinet Cooler

 

When compared to air-to-air heat exchangers and refrigerant based air conditioners, Cabinet Cooler systems win hands down.

Companies generally do not have issues with their control panels until the heat of summer. As the ambient conditions get warmer, the temperatures inside electrical panels also rise.  Sensitive electronics start to malfunction and shut down.  A telecommunication company was having the same issues.  They operated an ultra-broadband access service.  When the temperature alarms triggered, the system would shut down and reset.  This on and off cycling concerned the engineers in damaging and reducing the life of the electronics inside the telecommunications control box.

They contacted EXAIR as a possible supplier to retrofit their cabinets in critical areas. They started the conversation with a list of some stringent requirements.  They indicated that they were looking at other options like a refrigerant panel and an air-to-air heat exchanger.  The challenge was on…

Conditions:

Power Consumption: 350 Watts

Maximum Ambient Temp: 150 Deg. F (65 Deg. C)

Cabinet Location: Very limited space

Requirements:

  1. Retrofitting capability and ease of installation to existing cabinets
    1. EXAIR Cabinet Cooler: Excellent. 22mm knockout hole, about 30 minutes to install and weighs 0.5Lbs (0.2Kg).
    2. Refrigerant Type: Poor. Large panel cut outs, roughly 4 hours of installation, and weighs about 30Lbs (13.6Kg)
    3. Heat Exchanger: Poor. Large panel cut outs, roughly 2 hours of installation, and weighs 16Lbs. (7.3Kg)
  2. Fit into tight spaces
    1. EXAIR Cabinet Cooler: Excellent. For this application, it is 5.2” (131mm) high and 1.17” (30mm) diameter.
    2. Refrigerant Type: Poor. 22” (560mm) X 12” (305mm) X 8.5” (216mm). But also need additional room for air flow.
    3. Heat Exchanger: Good. Roughly 11” (279mm) X 16.5” (419mm) X 3.5” (89mm). But also need additional room for air flow.
  3. Able to handle high ambient condition
    1. EXAIR Cabinet Cooler: Excellent. We have a HT version for conditions up to 200 Deg. F (93 Deg. C).
    2. Refrigerant Type: Poor. Limited to about 125 Deg. F (52 Deg. C) maximum.
    3. Heat Exchanger: Good. Limited to 160 Deg. F (71 Deg. C) maximum
  4. Keep internal temperature at or below 95 Deg. F (35 Deg. C)
    1. EXAIR Cabinet Cooler: Excellent. With the high ambient temperature, it has very little effect on the cooling capacity.
    2. Refrigerant Type: Poor. The refrigerant will not work with the high ambient unless a water-cooled condenser is used. Added cost.
    3. Heat Exchanger: Poor. This unit will not be able to keep the temperature below ambient temperatures.
  5. Low maintenance (or maintenance free)
    1. EXAIR Cabinet Cooler: Excellent. No moving parts!!! With filtered compressed air, just put it into the panel and let it run. No PM required.
    2. Refrigerant Type: Poor. Minimum quarterly cleaning of condenser, changing the condenser filter, do electrical checks on compressor and fans, and refrigerant leak checks.
    3. Heat Exchanger: Good. Electrical checks on fans.
  6. Long life span
    1. EXAIR Cabinet Cooler: Excellent. 5 year warranty with units lasting over 10 years.
    2. Refrigerant Type: Poor. With high ambient conditions, the compressors and fans can short cycle causing premature failure.
    3. Heat Exchanger: Good. The fans can quit allowing electronics to heat up.
  7. Low cost (!!!) (This had 3 exclamation marks)
    1. EXAIR Cabinet Cooler: Excellent. Base unit less than $300.00
    2. Refrigerant Type: Poor. Base unit is near $1,500.00
    3. Heat Exchanger: Good. Base unit is near $1,000.00

Overall, in this scenario, there is no comparison. The EXAIR Cabinet Cooler can be mounted in minutes and start supplying cool air to the electrical components.  With no maintenance required and no moving parts, you can get many years of service.  Simple, quick, and easy made EXAIR Cabinet Cooler the correct choice.  All Cabinet Cooler systems are available with a UL Listed NEMA 12, NEMA 4, or NEMA 4X rating. They are CE compliant and available in 316SS for highly corrosive applications. If you have electrical heating issues like the telecommunication company, you can contact one of our Application Engineers for help.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

 

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