What is a Spot Cooler? Well to fully understand that let’s take a dive into what a Vortex Tube is, since at its core an Adjustable spot cooler is a Vortex tube with some bells and whistles that make them easier to use!
The operation of an Vortex Tube is one of the more curious phenomena in fluidics, and a particularly unique method of producing cold air. Since they don’t perform “heat transfer” in the classical sense (see below), there’s no RATE of heat transfer…they’re generating cold air, at rated flow and temperature, instantly.
EXAIR Corporation’s Vortex Tubes come in a range of sizes & cooling capacities, and are integrated into a number of Spot Cooler Products which add convenience and flexibility to their operation.
EXAIR’s Adjustable Spot Cooler incorporates this Vortex Tube technology to produce temperatures ranging from -30°F – +70°F. At a sound level of just 73 dBA when operated at 100 psig and stock generator installed, this compact cooler will keep your operation cool, clean and dry without causing unnecessarily high noise levels.
Through a simple turn of the control knob, you can easily adjust the temperature of the unit. Additionally, the kits come with (2) extra generators (15-H and 30-H) that can be swapped out for the stock generator for more/less cooling power and air consumption. The 15-H generator will deliver up to 1,000 Btu/hr of cooling capacity and the 30-H will provide up to 2,000 Btu/hr of cooling capacity. We have (2) different kits available, Model 3825 Single Point and the Model 3925 Dual Point Kit. The 3825 is recommended for use in applications where you’re cooling a small surface such as solder joints, hot melts, or drilled plastics.
The 3925 system is better served when heat is generated over a larger surface area such as saw blade cooling. The kits use flexible Loc-Line hose to allow you to precisely position the cold airflow onto your target. The Adjustable Spot Cooler provides easy mounting with a swivel magnetic base, allowing you to mount the cooler directly at the most critical point that heat is being generated.
If you’re tired of cleaning up your coolant or have an application that requires dry machining, or you just need to cool something hot! Get one of the Adjustable Spot Cooler systems on order today. They’re in stock ready to ship!
Georges-Joseph Ranque was born on February 7th, 1898 in Ambérieu-en-Bugey, France. The son of a railroad engineer, Léon-Joseph Ranque, it was not much of a surprise that he developed a strong interest in physics. An attendee of the prestigious and highly selective post-secondary school, Lycée Saint-Louis, Georges continued to develop his knowledge in the world of physics. From there he was admitted to École Polytechnique where he continued his studies. For years, Georges was interested in the Pantone carburetor. While developing an industrial pump, he noticed the phenomenon now known as the Ranque effect. The Ranque effect is the known working principle for industrial Vortex Tubes. When a compressed gas is injected into the tube tangentially at high velocity, two streams are created: one hot and one cold.
This cold airflow is then utilized throughout a variety of industrial spot cooling and enclosure cooling processes due to its simplicity and reliability. All that’s needed is a supply of compressed air. In 1931, Georges filed for a patent on his vortex tube. His idea didn’t go too far from there, until the topic was later picked back up by another physicist by the name of Rudolf Hilsch. Rudolf made some improvements to the design he called the “Wirbelrohr”, or “whirl pipe” for those not fluent in German. You’ll commonly hear the term “Ranque-Hilsch tube” used synonymously with the term Vortex Tube for this reason.
So how exactly does this thing work? The truth is no one knows for certain, but there is one commonly accepted theory that explains the phenomenon:
Compressed air is supplied into the tube where it passes through a set of nozzles that are tangent to the internal counter bore. The design of the nozzles forces the air to spin in a vortex motion at speeds up to 1,000,000 RPM. The spinning air turns 90° where a valve at one end allows some of the warmed air to escape. What does not escape, heads back down the tube in the inner stream where it loses heat and exhausts through the other end as cold air.
Both streams rotate in the same direction and at the same angular velocity. Due to the principle of conservation of angular momentum, the rotational speed of the inner vortex should increase. The best way to illustrate this is in Olympic Figure Skating. As the skater is wider, the spinning motion is much slower. As she decreases her overall radius, the velocity picks up dramatically and she spins much quicker. In a Vortex Tube, the speed of the inner vortex remains the same as it has lost angular momentum. The energy that is lost in this process is given off in the form of heat that has exhausted from the hot side of the tube. This loss of heat allows the inner vortex to be cooled, where it can be ducted and applied for a variety of industrial applications.
If you’re fascinated by this product and want to give it a try, EXAIR offers an unconditional 30-day guarantee. We have them all in stock and ready to ship as well, same day with an order received by 2:00 ET. Feel free to get in contact with us if you’d like to discuss how a vortex-based product could help you in your processes.
Okay, in case you haven’t been around the past year or two, and you have no clue where that simple word/statement comes from, then let me be the first to tell you that Ted Lasso is a great show, and you should check it out. So what does that have to do with EXAIR? Well, I like to think that sometimes the Application Engineers here are a lot like the coaching staff on the show. Sometimes we are strategic, we want to assert our experience and knowledge, and others, we are like Ted where we just ensure the thoughts and ideas you have already had.
That’s the fun part of being an Application Engineer here at EXAIR. I get to speak, chat, or email with both existing customers and potential new customers, resellers, and even catalog houses who all are trying to do one thing, improve a process or help someone out. Recently I was working with a manufacturing company trying to determine how fast they can cool a slab of steel with a Super Air Knife. Now, I by no means have a background in thermo like Russ Bowman, but he was busy preparing for our Spring Webinar to share some knowledge on Compressed Air System Storage. (If you haven’t checked a webinar out, most are available on our website in our knowledge base. ) So, I took the time to try and remember some of the tools I learned while at the University of Cincinnati. Thermodynamics was by far one of the hardest classes for me, The Algebra was always easy, I just always looked at the problems sideways I guess, and worried about too many variables. The truth of it is, if you keep it simple you can generally get somewhere close. so I took that approach. First I looked at what heat load would be generated by the steel slab.
I looked at the basic Heat Transfer equation – Q=c x m x ΔT where:
Q = Heat c = specific heat capacity m = mass ΔT = Change in temperature
I was able to locate the mass of the carbon steel plate with 1/2″ thickness. So I calculated the mass of the sheet. Then looked up the specific heat of the same plate, and took the change in temperature from what the customer stated the plate started at and finished at.
This resulted in a heat load. Then to calculate how much cooling a Super Air Knife could provide I utilized another calculation that gives the BTU constant of a cubic foot of air moving and I did decrease the efficiency of the knife due to some assumptions on space and temperature constraints. The resulting factor was the customer would need 6 Super Air Knives to blow the sheet down as it travels 5 feet per minute on a 60′ long conveyor.
This again had several assumptions and I made that very clear to the customer. To convert the amount of air a Super Air Knife puts out and how much cooling it can use, I did make some clear assumptions on the temperature of their atmosphere and the amount of entrainment then I used a calculation that we adapt for Vortex Tubes and Cabinet coolers to determine what cooling load will be achieved if the air pressure or temperature is less than optimal on one of those products.
In the end, the customer received an educated estimation or calculated answer with listed assumptions, to solve their issue with cooling a steel slab before it is stacked together. I really only used two calculations and manipulated some variables to try and make sense of what I knew and what the customer needed. The best part is, this whole process is backed by our 30-day guarantee on stock products which our 48″ Super Air Knife is. So this customer can take my basic math, use my suggestions, place an order, and test it out in their facility for a factual performance test to then proceed with a permanent solution.
Vortex Tubes are unique items that use an ordinary supply of compressed air to create two streams of air, one hot and one cold. We can drop the temperature by as much as 129oF (71.1oC) below inlet temperature on the cold end. It can also be raised as much as 195oF (107.9oC) above the inlet temperature on the hot end. And this can be done without any moving parts, motors, or Freon. Compressed air would be the only input. In this blog, I will cover how to adjust the Vortex Tubes and the resulting effects.
The cold air flow and temperature are easily controlled by adjusting a slotted valve located at the hot air outlet. Opening the valve (turning it counterclockwise) reduces the cold air flow rate and lowers the cold air temperature. Closing the valve (turning it clockwise) increases the cold air flow and raises the cold air temperature. So, how does this apply to cooling?
To go a little deeper, we have to consider cold air temperature and cooling capacity. Cooling capacity is the rate at which heat can be extracted. The higher the cooling capacity, the faster the heat is removed. This deals with temperatures and mass air flow. Like stated above, the colder the air temperature that we create with a Vortex Tube, the less cold air is produced. The two are inversely related. So, we have to find a balance between the temperature and cold air flow. You can find this rate by using Equation 1:
H’ = 1.0746 * Q * (T2 – T1)
H’ – cooling capacity (BTU/hr)
Q – cold air flow (SCFM)
T2 – Final temperature (oF)
T1 – cold air temperature (oF)
With a Vortex Tube, the temperature difference is based on the inlet pressure and Cold Fraction. The Cold Fraction is the amount of compressed air entering the Vortex Tube that will blow out of the cold end. The remaining portion of the air will travel out of the hot end as heated air. We have a chart below that shows the temperature drop on the cold air side and the temperature rise on the hot air side.
Here’s an example. If we use a model 3240 at two different Cold Fractions, we can see the difference in cooling power. At 100 PSIG (6.9 Bar), the model 3240 will use 40 SCFM (1133 SLPM) of compressed air. If we look at two different Cold Fractions: 20% Cold Fraction and 70% Cold Fraction, we can calculate the cooling capacities by Equation 1. In setting some criteria for our example, we will be using 70oF (21oC) compressed air at 100 PSIG (6.9 Bar). Also, we will have a target temperature of 95oF (35oC).
Example 1: At a 20% Cold Fraction and 100 PSIG, the Vortex Tube will generate a cold air temperature drop of 123oF. So, with a 70 oF inlet air temperature, the cold air temperature will be 70 oF – 123 oF = -53 oF. The amount of cold air at 20% Cold Fraction is 0.2 * 40 SCFM = 8 SCFM. Now that we have this information, we can calculate the cooling capacity.
Example 2: At a 70% Cold Fraction and 100 PSIG, the Vortex Tube will generate a cold air temperature drop of 71oF. So, with a 70 oF inlet air temperature, the cold air temperature will be 70 oF – 71 oF = -1 oF. The amount of cold air at 70% Cold Fraction is 0.7 * 40 SCFM = 28 SCFM. Now that we have this information, we can calculate the cooling capacity.
As you can see, Example 1 will give you a much colder air stream, but the cooling capacity is 56% less than Example 2. Or, in other words, in one hour, the Vortex Tube that is set at 70% Cold Fraction can remove 2,903 BTU of heat from an object. While the same Vortex Tube set at 20% Cold Fraction, which is much colder, will only remove 1,279 BTU of heat.
In the above examples, we used 95oF as the target temperature for our application. If the target temperature changes, then so does the relative cooling power generated by a vortex tube. We take this into account when we are performing calculations to determine which model and setting for cold fraction would be best for your application.
EXAIR offers a wide range of sizes and cooling capacities with our Vortex Tubes for different applications. They can be used to cool parts, set materials, and regulate temperatures in environmental chambers. They provide an instant and reliable flow of cold air at different temperatures. In this blog, I showed the difference between cold temperatures and the effect of cooling capacity. If you have an application that requires cooling, you can contact an Application Engineer at EXAIR, and we will be happy to run through these calculations to help you select the correct model.