Tag: hot

Rule #1 – Always Look Cool

Published on by Brian FarnoLeave a comment

The past two weeks here in Cincinnati have reminded me just what humidity is all about. While the static charge in my garage at home is at an all-time low, the humidity is enough to make me wish I had gills to breathe. Even rucking before work has become a rather sweaty event. When I am rucking, one of the 4 Rules of Rucking is, #1 Always Look Cool. This is an idiom as in don’t let people see you sweat. If you are stressed, just stay cool, keep a level head and look the part. A good pair of aviators always helps to hide what your eyes can’t.

Then I open my garage fridge, because every Midwesterner has their old kitchen fridge in the garage, right? Grab a nice cold aluminum can out. And before I can put it in a thermal insulating housing, I see the condensation of the humidity forming on the aluminum. This makes me think of some of the electrical panels I encountered during my time in machine shops.

I once approached a vertical machining center whose spindle chiller, with a thermo-couple failure, had been cooling the spindle continuously during the summer months. This spindle looked like the ice-cold aluminum can I had sitting out on my workbench yesterday. Fully covered in condensate from the humidity in the air. Condensate collected on an aluminum can and leaving a ring of water on a workbench is one thing. Water running down a high-speed spindle and causing issues with a dry machining process is another. This also reminded me of a recent call where a new customer wanted help sizing a Cabinet Cooler System to replace an air-to-air heat exchanger that had failed. When walking through the information needed to size the panel, I reached the Internal Temp Desired field, and there was a pause. While I thought maybe they were checking their notes, they came back with 72°F. I wrote down the value on my notepad, then asked, “That’s oddly specific. Is there a piece of equipment that alarms out over 72°F that we are trying to protect?” The response I received was no. So I asked what the need was for this low set point.

I dug further with them, and it turned out that’s what they kept the engineers’ office set for in the summer, so they thought my question was odd and figured, if they are comfortable there and their computer on their desk operates well, then it must be a good temperature. This is not an incorrect statement. The control cabinet for the machine would operate just fine at 72°F; however, all the electronics that were in the panel were rated up to 104°F before they overheat, so it doesn’t quite make sense to extend the cooling capacity needed to reach that 72°F requested set point. Once we talked this over, we settled on the standard of 95°F for the internal set point with the understanding that by using a thermostatically controlled system, they could adjust it down lower if they really wanted to. In the end, we saved them some energy by sizing the Cabinet Cooler System to meet the demands of their industrial electronics, not what makes a person feel comfortable.

This isn’t always the case; occasionally, there is a panel that requires a low maximum temperature in order to keep a critical piece of equipment stable. This is why we ask the questions to validate any concerns with the data we are viewing as Application Engineers. This is also why we have built in a number of warnings/alerts on our Online Cabinet Cooler Sizing Calculator.

If you have a panel that needs to be cooled, the online calculator has fields for all the information we need. If you want to walk through the math behind the calculator and talk through the reasons we ask for the information that we do, you can either call, email, or even live chat with an Application Engineer, and we will gladly walk you through our process and the math to determine which Cabinet Cooler System is right for your needs.

Brian Farno, MBA – CCASS Application Engineer

BrianFarno@EXAIR.com
@EXAIR_BF

Fundamental Modes of Heat Transfer

Published on by Brian FarnoLeave a comment

Generally I like to write about cool stuff. Whether it is a new product like our TurboBlast Safety Air Gun, an application that really helped cool down a process for a customer, or even something cool I have done like a GORUCK event or training. Well, today is not one of those days, today we are going to talk about the opposite of cool … HEAT and more importantly the methods it is transferred.

1 – Energy Transfer – Heat

The process of how heat is generated all starts with a conversion of energy. Whether it is friction, or converting energy to light, or even converting energy to a different voltage through something like a transformer. No matter how it is generated, heat will begin to transfer. On the molecular level, atoms are storing the energy which will cause electrons to enter into an excited state and rapidly switch between shells. When the electron returns back to a lower shell (closer to the nucleus) energy is released; the energy released is then absorbed by atoms at a lower energy state and will continue until the thermal energy is equal between the two objects. Heat has four fundamental modes of transferring energy from surface to surface and they are as follows:

Conduction
Conduction can also be referred to as diffusion and is the transfer of energy between two objects that have made physical contact. When the two objects come into contact with each other thermal energy will flow from the object with the higher temp to the object with the lower temp. A good example of this is placing ice in a glass of water. The temperature is much lower than the room temperature therefore the thermal energy will flow from the water to the ice.

Radiation
Radiation is the transfer of thermal energy through empty space and does require a material between the two objects. Going back to the how thermal energy is released from atoms; when the electron returns to a lower energy shell the energy is released in the form of light ranging from infrared light to UV light. Energy in the form of light can then be absorbed by an object in the form of heat. Everyone experiences radiation transfer every day when you walk outside; the light from the sun’s radiation is what keeps this planet habitable.

Convection
Convection is the transfer of thermal energy between an object and a fluid in motion. The faster the fluid moves the faster heat is transferred. This relies on the specific heat property of a molecule in order to determine the rate at which heat will be transferred. The low the specific heat of a molecule the faster and more volume of the fluid will need to move in order to get full affect of convection. Convection is used in modern ovens in order to get a more even heat through out the food while cooking.

Advection
Advection is the physical transport of a fluid from point A to point B, which includes all internal thermal energy stored inside. Advection can be seen as one of the simpler ways of heat transfer.

No matter how the heat is transferred to an object, if it needs to be cooled there is a good chance that one of our Application Engineers has approached a similar issue and can help. To discuss, contact us and we will walk through the best method to eliminate the heat you need to.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

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

Heat Transfer – How Energy Can Move

Published on by codybiehleLeave a comment

Heat. One word can bring to mind so many different things from cooking to sun tanning. But what is heat and how does it move. Heat is essentially a form of energy that flows in the form of changing temperatures; this form of energy will flow from high to low. When you describe something as being hot, you are actually describing that the item in question has a higher temperature than your hand thus the thermal (heat) energy is flowing from that object to your hand. This phenomenon is what is referred to as heat transfer. Heat transfer can be observed all the way down to the atomic scale with the property known as specific heat. Every molecule and atom can carry a set amount of energy which is denoted by specific heat; this value is the ration of energy (usually in Joules) divided by the mass multiplied by the temperature (J/g°C).

Energy moving through atoms in an object

But how does this heat move from object to object? On the atomic scale, the atoms are storing the energy which will cause electrons to enter into an excited state and rapidly switch between shells. When the electron returns back to a lower shell (closer to the nucleus) energy is released; the energy released is then absorbed by atoms at a lower energy state and will continue until the thermal energy is equal between the two objects. Heat has four fundamental modes of transferring energy from surface to surface and they are as follows:

Advection
Advection is the physical transport of a fluid from point A to point B, which includes all internal thermal energy stored inside. Advection can be seen as one of the simpler ways of heat transfer.

Conduction
Conduction can also be referred to as diffusion and is the transfer of energy between two objects that have made physical contact. When the two objects come into contact with each other thermal energy will flow from the object with the higher temp to the object with the lower temp. A good example of this is placing ice in a glass of water. The temperature is much lower than the room temperature therefore the thermal energy will flow from the water to the ice.

Convection
Convection is the transfer of thermal energy between an object and a fluid in motion. The faster the fluid moves the faster heat is transferred. This relies on the specific heat property of a molecule in order to determine the rate at which heat will be transferred. The low the specific heat of a molecule the faster and more volume of the fluid will need to move in order to get full affect of convection. Convection is used in modern ovens in order to get a more even heat through out the food while cooking.

Radiation
Radiation is the transfer of thermal energy through empty space and does require a material between the two objects. Going back to the how thermal energy is released from atoms; when the electron returns to a lower energy shell the energy is released in the form of light ranging from infrared light to UV light. Energy in the form of light can then be absorbed by an object in the form of heat. Everyone experiences radiation transfer every day when you walk outside; the light from the sun’s radiation is what keeps this planet habitable.

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.

If you have any questions about compressed air systems or want more information on any of EXAIR’s products, give us a call, we have a team of Application Engineers ready to answer your questions and recommend a solution for your applications.

Cody Biehle
Application Engineer
EXAIR Corporation
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The picture “Energy Transfer – Heat” by Siyavula Education is licensed under CC BY 2.0

Discovery of The Vortex Tube

Published on by Brian FarnoLeave a comment

There are many theories regarding the dynamics of a vortex tube and how it works. Many students have studied them in hopes of advancing the physics or as part of their undergrad studies. The man that started it all was not intentionally researching it, however.

The Vortex Tube was invented by accident in 1928, by George Ranque, a French physics student. He was performing experiments on a vortex-type pump that he had developed and noticed that warm air exhausted from one end and cold air from the other. Ranque quickly changed his focus from the pump to start a company taking advantage of the commercial possibilities for this odd little device that produced both hot and cold air, using only compressed air, with no moving parts. The company was not successful, and the vortex tube was forgotten until 1945 when Rudolph Hilsch, a German physicist, published a widely read paper on the device.

A vortex tube uses compressed air as a power source, has no moving parts, and produces hot air from one end and cold air from the other. The volume and temperature of the two air streams is adjustable with a valve built into the hot air exhaust.  Temperatures as low as -50°F (-46°C) and as high as 260°F (127°C) are possible.

Compressed air is supplied to a vortex tube and passes through nozzles that are tangent to an internal counterbore. As the air passes through it is set into a spiraling vortex motion at up to 1,000,000 rpm. The spinning stream of air flows down the hot tube in the form of a spinning shell, like a tornado (in red). The control valve at the end allows some of the warmed air to escape and what does not escape reverses direction and heads back down the tube as a second vortex (in blue) inside of the low-pressure area of the larger warm air vortex. The inner vortex loses heat and exits through the other end of as cold air.

It is thought that both the hot and cold air streams rotate in the same direction at the same angular velocity, even though they are traveling in opposite directions. A particle of air in the inner stream completes one rotation in the same time of an air particle in the outer stream. The principle of conservation of angular momentum would say that the rotational speed of the inner vortex should increase because the angular momentum of a rotating particle (L) is equal to the radius of rotation (r) times it’s mass (m) times its velocity (v).  L = r•m•v.  When an air particle moves from the outer stream to the inner stream, both its radius (r) and velocity (v) decrease, resulting in a lower angular momentum. To maintain an energy balance for the system, the energy that is lost from the inner stream is taken in by the outer stream as heat. Therefore, the outer vortex becomes warm and the inner vortex is cooled.

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At EXAIR, we have harnessed the cooling power of the vortex tube, and it can be found and utilized in such products as Spot Coolers, Cabinet Coolers, and Vortex Tubes themselves. If you have questions about Vortex Tubes, or would like to talk about any of the EXAIR Intelligent Compressed Air® Products, feel free to contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF