Tag: air to air heat exchanger

Refrigerated Air Dryers

Published on by johnball2014Leave a comment

Whenever air gets compressed, it reduces the space for the water molecules to remain as a vapor; which causes condensation.  For this, compressed air dryers are an important part of a compressed air system.  They are designed to remove moisture to prevent condensation further downstream in the system.  The three main types of dryers are refrigerated, desiccant, and membrane. For this blog, I will cover the refrigerant-type compressed air dryers.

Compressed air dryers are rated with a dew point rating.  A dew point is the temperature at which the air has a relative humidity of 100%.  Since the air cannot become more saturated with water than 100%RH, water will condense and fall out like “rain”.  You can see this effect during the cool mornings when dew forms on the grass.  Compressed air dryers are designed to reduce the dew point temperature of your compressed air.  For a refrigerant type, they are near the dew point temperature of 38oF (3oC).  Like a refrigerator, they use refrigerant to cool the compressed air.  We cannot go below this temperature as it could form ice inside the dryer.  But, as long as the ambient temperature does not go below 38oF (3oC), liquid water will not be present in the pneumatic system. 

There are two main types of refrigerated air dryers; cycling and non-cycling.  Cycling type refrigerant air dryers will cool a liquid mass, generally a glycol-water mixture, to a set-point and turn off.  The liquid will go through an air-to-liquid heat exchanger to remove the heat from the compressed air.  Referring to the cycling action, when the liquid mass goes above the set point, the refrigeration system will restart and cool the liquid mass again.  The cycling refrigerant air dryers are more expensive, but they are more efficient. 

Non-cycling refrigerant air dryers are more common.  The refrigeration system continues to run through an air-to-air heat exchanger to cool the compressed air.  It is similar to your AC system in your car.  With this type of system, they are more susceptible to the environment, i.e., temperature, elevation, and humidity.  So, adjustments are required for proper installation. 

With both types of refrigerant dryers, the internal compressed air section is very similar.  They will have a filter separator to remove the liquid that is created from the condensation from the cold temperatures.  They also have an additional air-to-air heat exchanger.  This will provide two important features for the refrigerated air dryers.  As the cold air leaves the refrigerant section, it helps to cool the incoming compressed air.  This will make the system more efficient.  And as the hot incoming compressed air helps to warm the cold air leaving the dryer, it will stop the condensation of liquid water on the outside of the pipes.  Like the dew forming on the grass during cool mornings, the same will occur with the compressed air piping system. 

Moisture-laden compressed air can cause issues such as increased wear on the pneumatic tools, the formation of rust in piping and equipment, quality defects in painting processes, and frozen pipes in colder climates.  Regardless of what products you’re using at the point-of-use, a compressed air dryer is undoubtedly a critical component of the compressed air system.  Delivering clean, dry air to your EXAIR Products or other pneumatic devices will help to ensure a long life out of your equipment.  If you wish to discuss more about your compressed air system or how EXAIR can provide a more efficient way to use that compressed air, an Application Engineer will be happy to assist you. 

John Ball, CCASS


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

Photo: Grass morning dew by RuslanSikunov.  Pixabay License

Intelligent Solutions for Electrical Enclosure Cooling Educational Webinar

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Warmer temperatures are quickly approaching, which may seem like a welcome change for personal reasons, but in a processing line, the increased temperatures can wreak havoc on sensitive components found in an electrical control panel.

EXAIR Corporation will be hosting a FREE webinar titled “Intelligent Solutions for Electrical Enclosure Cooling” on May 23, 2018 at 2:00 PM EDT.

(click on the photo to register – it’s FREE!)

By attending this interactive session, you will learn the difference between the 3 most common NEMA ratings for electrical control panels found in an industrial setting, NEMA Type 12, 4 and 4X. We’ll provide examples of traditional, yet unreliable, methods of cooling and the concerns associated with using these types of devices.

Next we will explain how ignoring heat related issues can cause machines to shut down due to failed electrical components, resulting in lost production and increased maintenance costs, negatively affecting a company’s bottom line.

In closing, we’ll show how using an engineered, compressed air operated solution can reduce  downtime by providing a low cost, maintenance-free way to cool and purge control panels with no moving parts.

CLICK HERE TO REGISTER

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN

2” Flat Super Air Nozzles Separate Sheets of Metal Film

Published on by johnball2014Leave a comment

Heat Exchanger plates

An overseas company manufactures brazed plate heat exchangers. This type of heat exchanger has a series of corrugated plates that are stacked onto each other. It is designed to create a turbulent flow for better heat transfer in a very compact size. The plates inside the heat exchanger are made of 321 stainless steel which is basically a 304 type of stainless steel but with a titanium stabilizer. This company would receive plain sheets of stainless steel material that were stacked on each other in a column. The dimensions of the plates were as follows: 305mm wide by 520mm long with a thickness of 0.5mm (12” Wide X 20.5” Long X 0.02” thick respectively). Each sheet weighed 635 grams (1.4 lbs.). They would set a stack of the stainless-steel sheets at the beginning of a press machine. The press machine would form the corrugated design into the face of the sheet. They were using a pick-and-place vacuum system to lift one sheet at a time to place inside the press. They started having problems with their process when occasionally two or three sheets would stick together. The underlying sheet could either fall onto the floor which would bend the sheet or be stacked inside the press which would cause an improper corrugation. Both issues were causing much scrap as well as downtime in their process .

They contacted EXAIR to find a way to improve the efficiency of their process. They wondered if static could be causing the “sticking” issues. Generally, static forces are really noticed with sheets made of plastic or non-conductive materials. The stronger the static force, the more issues with sticking and misalignment. EXAIR does offer Static Eliminators to remove static forces in applications just like this. But, with plain metal sheets, static is not a problem as the ions are able to balance themselves.

Typically, the main cause for metal sheets to “stick” together is surface tension. Liquid like water has a strong affinity to itself within the molecular structure, called cohesion, and to the surface that it lies on, called adhesion. The cohesion plus the adhesion to the metal surface can have a strong enough force to overcome the weight of the sheets. To break the surface tension, an additional force is required.  An example of surface tension is with nylon tent material. The surface tension of water is strong enough to keep rain drops from penetrating the fabric. If you break the surface tension by touching the tent material, the surface will start to leak water. The same goes for the thin sheets of metal. We just need to break the surface tension to allow the sheets to separate.

2″ Flat Super Air Nozzle

I recommended two pieces of the model 1122, 2” Flat Super Air Nozzles. This nozzle gives a flat air pattern to force air between the sheets. Surface tension is based on force over length. Once the sheets start to separate, the contact length will decrease thus reducing the “sticking” force caused by surface tension. In this application, the amount of cohesion and adhesion forces caused by surface tension were unknown. Oil, water, and other liquids have different surface tensions which would require different amounts of blowing forces. To ensure the proper amount to separate the sheets, I recommended the shim set, model 1132SS.

The shims have different thicknesses that can be installed easily into the 2” Flat Super Air Nozzle to change the amount of blowing force.  In conjunction with a regulator, this customer could “dial” in the proper amount of force required to counteract the surface tension from any type of liquid that may be on the surface of the sheets.  I had them mount one nozzle at two different corners to help “peel” the sheets apart. The customer also tied in a solenoid valve into the compressed air system to cycle on the 2” Flat Super Air Nozzles only during the time when the vacuum system wanted to grab the top sheet. This reduced the amount of compressed air needed for their operation.  After the installation, the procedure ran smoothly without downtime and scrap waste.

If your application is creating scrap and downtime caused by sheets sticking together, EXAIR has many types of products to help eliminate this. Whether the “stickiness” is caused from static or liquid adhesion, an Application Engineer can direct you to the best product to eliminate the “stickiness”. For the overseas company above, we were able to apply a sharp flat burst of air to overcome the surface tension between the sheets.

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

 

Heat Exchanger Plates by epicbeer.  Creative Common by 2.0

 

Types Of Compressed Air System Dryers

Published on by exaircorpLeave a comment

Many times, when discussing product selection with a customer, we commonly reference supplying as clean and dry air as possible to promote peak performance. In iron piping systems for example, when moisture is present, rust can develop which can reduce the performance of end use compressed air operated devices like air tools or cause issues on the exhaust side as you could exhaust unwanted mist onto a surface, like in a painting operation.

Example of a desiccant dryer

Typically, an efficient and properly installed industrial compressed air system will include some type of dryer to remove any moisture that may be present in the supply.

Let’s take a look at the various types of dryers available.

Refrigerant and desiccant dryers are two of the more commonly used types of dryers.

Refrigerant based systems have several stages. The compressed air first passes through an air to air heat exchanger  which initially cools the air. The air is then delivered to an air to refrigerant exchanger where an external source of liquid refrigerant further cools the air and sends it to a separator, where the water vapors condensate and are removed through a drain trap. Now that the air is dry, it is then cycled back to the air to air exchanger where it is heated back to ambient temperature and exits the system.

Desiccant dryers typically incorporate 2 tanks containing a porous desiccant which causes the moisture to sort of “cling” to the surface. In these systems, compressed air flows through one tank, while, using it’s own regeneration cycle, heated or unheated air is blown through the desiccant in the other tank to remove the moisture and dry the air.

Membrane Dryers are typically used at the end use product. These types of systems utilize membranes to dissipate water vapor as it passes through the material, while allowing a small amount of the dry air to travel the length of the membrane to sort of “wipe” the condensate and remove it from the system.

Deliquescent Dryers use a drying agent which absorbs any moisture in the air. As the vapors react with the desiccant, like salt, the desiccant liquefies and is able to be drained at the bottom of a tank. These are the least expensive dryers to purchase and maintain because they have no moving parts and require no power to run.

When a dryer is being considered for a particular setup, there are 3 common reference points used when determining the dryers rating – an inlet air temperature of 100°F, supply pressure of 100 PSIG and an ambient air temperature of 100°F. Changes in supply pressure or temperature could change the performance of a particular dryer. You want to follow the manufacturer’s recommendations when dealing with variances as they will typically provide some type of conversion.

For help with this or any other topics relating to the efficient use of compressed air, please give us a call, we’d be happy to help.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN

 

Heated Desiccant Dryers image courtesy of Compressor1 via creative commons license