Heat Transfer – 3 Types

When you have two objects and they are of different temperatures, we know from experience that the hotter object will warm up the cooler one, or conversely, the colder object will cool down the hotter one.  We see this everyday, such as ice cooling a drink, or a fan cooling a person on a hot day.

The Second Law of Thermodynamics says that heat (energy) transfers from an object of a higher temperature to an object of a lower temperature. The higher temperature object has atoms with higher energy levels and they will move toward the lower energy atoms in order to establish an equilibrium. This movement of heat and energy is called heat transfer. There are three common types of heat transfer.13580963114_f222b3cdd9_z

Heat Transfer by Conduction

When two materials are in direct contact, heat transfers by means of conduction. The atoms of higher energy vibrate against the adjacent atoms of lower energy, which transfers energy to the lower energy atoms, cooling the hotter object and warming the cooler object. Fluids and gases are less heat conductive than solids (metals are the best heat conductors) because there are larger distances between atoms.  Solids have atoms that are closer together.

Heat Transfer by Convection

Convection describes heat transfer between a surface and a liquid or gas in motion. The faster the fluid or gas travels, the more convective heat transfer that occurs. There are two types of convection:  natural convection and forced convection. In natural convection, the motion of the fluid results from the hot atoms in the fluid moving upwards and the cooler atoms in the air flowing down to replace it, with the fluid moving under the influence of gravity. Example, a radiator puts out warm air from the top, drawing in cool air through the bottom. In forced convection, the fluid, air or a liquid, is forced to travel over the surface by a fan or pump or some other external source. Larger amounts of heat transfer are possible utilizing forced convection.

Heat Transfer by Radiation

Radiation refers to the transfer of heat through empty space. This form of heat transfer does not require a material or even air to be between the two objects; radiation heat transfer works inside of and through a vacuum, such as space. Example, the radiation energy from the sun travels through the great distance through the vacuum of space until the transfer of heat warms the Earth.

EXAIR‘s engineered compressed air products are used every day to force air over hot surfaces to cool, as well as dry and/or blow off hot materials. Let us help you to understand and solve your heat transfer situations.

To discuss your application and how an EXAIR Intelligent Compressed Air Product can improve your process, feel free to contact EXAIR, myself, or one of our other Application Engineers. We can help you determine the best solution!

Brian Bergmann
Application Engineer

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The picture “Energy Transfer – Heat” by Siyavula Education is licensed under CC BY 2.0

Expand Flexibility of Cabinet Coolers with Side Mount Kits

Last week I wrote about the Thermostat Options for Smart Cooling utilizing the EXAIR Cabinet Cooler Systems.  You can see read that blog post here.  Today we will touch base on the Side Mount Kits as an option to expand the flexibility for the installation and operation.

Sometimes there isn’t room above an electrical panel to fit the Cabinet Cooler, even though it takes just 5″ to 7.25″ of space above. In these cases, the Side Mount Kit is available to handle any of the Cabinet Cooler sizes and NEMA ratings. EXAIR offers (6) models of Side Mount Kits –

  • Model 4909 – For NEMA 12 Cabinet Coolers up to 550 BTU.hr (139 Kcal/hr), Aluminum construction
  • Model 4910 – For NEMA 12 Cabinet Coolers , 650 BTU//hr (165 Kcal/hr) and higher, Aluminum construction
  • Model 4906 – For NEMA 4 and 4X Cabinet Coolers up to 550 BTU/hr (139 Kcal/hr), Type 303 Stainless Steel
  • Model 4907 – For NEMA 4 and 4X Cabinet Coolers, 650 BTU/hr (165 Kcal/hr) and higher, Type 303 Stainless Steel
  • Model 4906-316 – For NEMA 4 and 4X Cabinet Coolers up to 550 BTU/hr (139 Kcal/hr), Type 316 Stainless Steel
  • Model 4907-316 – For NEMA 4 and 4X Cabinet Coolers, 650 BTU/hr (165 Kcal/hr) and higher, Type 316 Stainless Steel

side_mounts_new

The NEMA 4 and 4X Cabinet Coolers must be mounted vertically for the unit to properly resist the ingress of liquids and maintain the integrity of the cabinet NEMA rating.

The Side Mount Kits install into a standard electrical knockout (1-1/2 NPS) for easy installation.

If you have any questions about the Side Mount Kits, Cabinet Coolers and/or Thermostat Options or any of the EXAIR Intelligent Compressed Air® Products, 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 System for Electrical Enclosure Cooling

If you watched the Webinar we hosted recently (if not, Watch It here) then you know that the EXAIR Cabinet Cooler System is an intelligent solution for electrical enclosure cooling.  The use of a Thermostat Control system is a key component to a system that provides the needed cooling while keeping compressed air usage to a minimum. There are several choices available, and I will cover those for you today.

The thermostat control systems are the most effective way to operate a Cabinet Cooler. They work by activating the the cooler only when the internal temperature of the enclosure reaches a preset, critical level. Thermostat controlled cooler systems are the best option when a cabinet will experience fluctuating heat loads, caused by operational, environmental, and seasonal changes.

Cabinet Cooler Systems that are ordered from the factory with thermostat control include a solenoid valve and thermostat.  The solenoid valve is available in 110-120VAC, 50/60 Hz, 240VAC, 50/60 Hz, and 24VDC and is UL Listed and CE and RoHS compliant. The thermostat is rated for 24V-240V AC or DC, 50/60 Hz and is UL Recognized and CSA Certified.

Solenoids
Solenoid Valves – 24 VDC, 110 VAC, and 240 VAC Available

 

The thermostat is factory set at 95°F (35°C). It will typically hold an internal cabinet temperature to +/- 2°F (1°C). The thermostat can be adjusted up or down if a different internal temperature is desired by turning the slotted temperature adjusting sleeve, with a 1/16 turn being approximately a 5°F change.

9017_thermoPRINT
Thermostat

 

The solenoid and thermostat components are rated to match and maintain the Cabinet Cooler System and cabinet NEMA rating, and can be NEMA 12, NEMA 4 or NEMA 4X. A Thermostat Control can be added to an existing Continuous Operation Cabinet Cooler System, please consult the factory for help in selecting the right kit.

4825SS
NEMA Type 4X Cabinet Cooler System, which includes the Solenoid Valve and Thermostat

If you have any questions about the Cabinet Coolers and Thermostat Options or any of the EXAIR Intelligent Compressed Air® Products, 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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High Temperature Vortex Tube for Sensor Cooling

Last year I worked with a power company that was having issues with Position Feedback Sensors overheating causing erroneous readings and early failures.  The sensors were located above a steam turbine, and the ambient temperatures reached 128°F with spikes to 140-150°F.  The customer had called in looking for a way to keep the sensors cool, using minimal compressed air, and in a robust package.  After reviewing the details, we recommended the High Temperature Vortex Tube, model HT3210.  While using just 10 SCFM of 100 PSIG compressed air, the HT3210 provides 8 SCFM of cold air at a temperature drop of 54°F from the supply air temperature.  Bathing the sensor with this cool air keeps prevents it from heating up and has eliminated the bad readings and prevented the early failures.

The customer recently implemented the same fix for another set of sensors.

Plant Photo
Power Generation Process, with (3) Position Feedback Sensors
Sensor
Position Feedback Sensor

The High Temperature Vortex Tube is a special Vortex Tube offering from EXAIR that utilizes a brass generator and hi-temp seal for use in ambient temperatures up to 200°F.  Simply supply clean, dry compressed air, and get cold air starting at 50-54°F lower than the supply air temperature.  With sizes ranging from 2 to 150 SCFM, there is a Vortex Tube that will meet most applications.

Vortex tube
High Temperature Vortex Tube

If you have questions about the Vortex Tubes, or would like to talk about any of the EXAIR Intelligent Compressed Air® Products, 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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Video Blog: Medium Vortex Tube Cooling Kit

EXAIR offers (3) Vortex Tube Cooling Kits, and the video below will provide an overview of the medium size offering, for refrigeration up to 2800 BTU/hr (706 Kcal/hr.)

If you have questions regarding Vortex Tube Cooling Kits or 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 Application Details Guide

The EXAIR website is valuable resource for reviewing and getting information about the many Intelligent Compressed Air® Products that we manufacture and sell.  It is a good place to learn more about the products, how they work, calculate air savings, see the many styles and materials of construction and much, much more.

If you have a specific application and would like us to review the process parameters and get our recommendation as to the best way to solve the issue, you can utilize the Application Assistance Worksheet located on the Left Menu Bar on many of the Product Pages.

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Clicking on the Application Assistance Worksheet will provide you with a couple of ways to access the form.  Choosing one of the options will present you with the form below.

ApplicationDetailsGuide

This form has sections regarding Process Description, Part Specifications, Product Movement, and Other for general information.  By filling out this form with as much detail possible, and then online submitting or emailing to applications@exair.com, one of our Application Engineers will review and be in contact with you to further discuss in preparation for presenting a solution for you.

Or – to discuss your processes and how an EXAIR Intelligent Compressed Air® Product can provide a beneficial service, feel free to contact EXAIR and myself or one of our other Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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Quick, Cool, and Quiet – The EXAIR Adjustable Spot Cooler

I recently had the pleasure of assisting a caller with a cooling application. We’ve written before (more than once) about cooling applications & product selection, and I had a very similar conversation with this caller. Since the need was for cooling as quickly as possible to ambient temperature, the caller was keen on talking about Vortex Tubes.

This application entails operators placing small products, by hand, under the cold air flow for rapid cooling.  Now, a Vortex Tube can produce VERY low temperatures…down to -40F…so operator safety had to be addressed.  By keeping the Cold Fraction (the percentage of supply air flow which is directed to the cold end) high, we can also keep the temperature high enough to not present a hazard (i.e., frostbite) but still plenty low enough for effective cooling.

Since sound level was also a concern, we discussed mufflers…with Hot and Cold Mufflers installed on a Medium Vortex Tube (models 3215, 3225, or 3230, which were what we narrowed our discussion to,) a sound level of 81-84 dBA will be produced.  That’s within OSHA’s limits for 8-hour exposure, but isn’t exactly “communication-friendly” for operators that need to talk to each other on a regular basis.

The Model 3825 Adjustable Spot Cooler System incorporates the performance of the three Vortex Tube models that we were talking about into a convenient mag base mounted assembly, fitted with a cold muffler, flexible cold air hose, and additional sound level suppression to 72-74 dBA…which makes a significant difference in areas where operator conversation is critical.

EXAIR's Adjustable Spot Cooler provides cold air, on demand - quiet and easy!
EXAIR’s Adjustable Spot Cooler provides cold air, on demand – quiet and easy!

The temperature control knob allowed them to dial in the optimal cold air flow, keeping the temperature low enough, and flow high enough, for rapid cooling of the parts.

If you’d like to find out just how cool an EXAIR Vortex Tube/Spot Cooling Product can make your application, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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