Tag: Cooling Application

Calculating Air Volume for Cooling

Published on by Lee EvansLeave a comment
Motores_en_el_robot
Robot motor in need of cooling

 

dims
Accompanying information about motor in need of cooling

Usually, when discussing application solutions we can make recommendations for proper product based on experience, empirical test data, and application parameters.  Sometimes, though, we need to take things just a little further and aim to dial in the recommended solution before any testing ever occurs.

I recently had an exercise in this, involving the need to cool the robot motor shown in the photo above.  This motor, existing in two forms (one weighing 23kg and the other weighing 25kg) is currently operating, creating heat, and registering a temperature of 90°C.  The desired operating temperature is 60°C, and we can safely assume an ambient temp. no higher than 35-40°C.

The questions posed to me were:  “Which product should be used to cool this motor?  And, how do you know?”  So, I took a certain degree of liberty (though not much) in considering the motor in question is comprised of copper windings, and these windings comprise the total weight of the motor.

Considering this, our knowns for this application were:

Weight:                              23kg and 25kg

Material:                            Copper

Starting temp:                   90°C

Ending temp:                    60°C

 

What we didn’t know was:

Specific heat of copper:                  (determined to be 0.385 Joules/g°C)

Amount of airflow to cool this motor by 30°C:                     XXX cubic feet per minute

 

This airflow was determined using the process shown below, and the resulting calculations shown below.

heat load calc process
Process to calculate the required airflow in a cooling application

 

heatcalcs
The calculations used to determine the required airflow in this application

 

Super Air Amplifier Performance Specs
Performance specifications of our Super Air Amplifiers

The end result was confirmation that EXAIR model 120022, our 2” Super Air Amplifier, can use just 15.5 SCFM of compressed air at 80 PSIG to produce an airflow to cool this motor.  And, thanks to the skills of the team here at EXAIR we have the numbers to back up that claim.

If you have an application with a similar need and think we may be able to help, contact an EXAIR Application Engineer.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

Which Vortex Tube Do I Need?

Published on by Dave WoernerLeave a comment

Last week, I wrote a brief introduction to vortex tubes, titled “One Item Generates ¼ Ton of Refrigeration and Fits in the Palm of your Hand.” In it I introduced the Vortex Tube and the other products made from Vortex Tubes: Cabinet Coolers, Cold Guns, Adjustable Spot Cooler and Mini Coolers. I also introduced the idea of a cold fraction.  Today, I want to talk about specific Vortex Tube models.

The flow from the cold side of the Vortex Tubeis characterized in two different ways. First, we characterize the air by ΔT (temperature drop) from the starting compressed air temperature. With a supply pressure of 100 PSIG, the drop in temperature can range from 54° to 123° Fahrenheit. Second, we characterize the flow of air in Standard Cubic Feet per Minute. The different models of vortex tube are design to provide a range of flows and temperature.

Vortex Tube Specification
Vortex Tube Specification Chart

When facing this list you have numerous choices that can be daunting. My priorities for selecting a Vortex Tube for a customer are twofold. First, you need the Vortex Tube that will work in your application. Second, I want to choose the model with the least amount of compressed air in order to solve their problem with the least amount of air possible. The smallest Vortex Tube is a model 3202. It also utilizes the least amount of compressed air, 2 SCFM. At 100 PSIG and an 80 percent cold fraction, it will produce a cold flow of 1.6 SCFM at 54° F  below your compressed air temperature. If your compressed air temperature is starting at 70° F, your cold temperature will 16° F. All of the Vortex Tubes will be able produce this same temperature drop, but depending on which Vortex Tube you use will determine the volume of flow produced at that temperature.

1.6 SCFM of flow 54° F below compressed air temperature will take 135 BTU/HR away from a small 100°F box, which is enough energy to cool a needle, a small sensor, or a tiny camera, but what if you have a bigger area you need to cool. Then you need to use a Vortex Tube that will produce more flow. The 3202, 3204, and 3208 will all produce air at the same temperature, but the 3204 and 3208 will produce more volume of cold air.  With the same parameters as above (100 PSIG of inlet pressure and 80 percent cold fraction) the 3204 will produce 3.2 SCFM of cold air and cool 275 BTU/Hr. out of a 100° F environment. The 3208 will produce 6.4 SCFM of cold air and cool 550 BTU/Hr. These larger Vortex Tubes could be used to cool a closed circuit camera in a hot environment or a small drill bit where coolant is prohibited or undesired. From here our product continue to produce more volume of flow and we can go up to our largest Vortex Tube, 3299 which will use 150 SCFM of compressed and cool up to 10,200 BTU/HR.

What if you have an application where you don’t need more air but 16°F  isn’t cold enough? Then you can adjust your cold fraction. Adjusting the cold fraction will allow you to increase the temperature drop. Opening the brass hot valve, will lower the cold fraction. As more air is allowed to escape out of the hot end of the Vortex Tube, the temperature and the flow rate of the cold flow decrease.  If you need to cool below a 50% cold fraction we recommend the 3400 series Vortex Tubes. At 100 PSIG this would occur when you need more than 100° F temperature drop.

Vortex Tubes can be used in a variety of cooling application. If you have any question about the topic discussed above please contact me or another application engineer.

Dave Woerner
Application Engineer
DaveWoerner@EXAIR.com
@EXAIR_DW

Vortex Tube Cooling: One Vortex Tube, Multiple Targets, Will This Work?

Published on by Neal RakerLeave a comment

VortexTubes

I had this question posed to me the other day. The customer asks, “I have three, small, enclosed spaces that are all within about five feet of each other. I’d like to put vortex tube cooling into each space. Can I do it with one vortex tube or will I have to use three of them?”

Imagine if you will, the cold air output of a single vortex tube being split three ways and ducted into each of these small chambers. While it is definitely technically possible to do, it isn’t always a feasible idea from the point of view of lost cooling power. Also, anytime that you can split up the effect you are trying to create whether that be cooling with a Vortex Tube or blowing off a large target that has many features to it, generally it is better practice to divide the application solution up to be applied over multiple, smaller units rather than one large one.

In this customer’s case, he wanted to save money on the purchase of multiple vortex tubes by purchasing one model 3230 vortex tube and plumbing the cold air output to his three cooling chambers. The problem is that the ambient temperature outside the boxes is rather hot and also contains high humidity. How exactly is this a problem?  You might ask. The problem is in all of the heat lost in cooling down the cold air distribution pipe (the pipe, hose or tube delivering the cold air into the chambers) that lies outside each box. That results in a net temperature gain (higher temperature) of the cold air you are trying to use for cooling the chambers or enclosures. With that lost cooling power, the customer runs a risk of not having sufficient cooling power to offset the heat load in each chamber. There is also the issue of back-pressure being presented to the Vortex Tube itself from the cold air distribution piping. When subjected to back-pressure, vortex tubes will lose their cooling capacity. Finally, there is the problem of getting equal cooling power delivered to each chamber. In this case, the solution of piping cold air to each chamber would cause an un-even distribution of the cold air with the closest chamber receiving the lion’s share of the cooling, leaving the other two under-cooled.

So, what is a better way to do this?  The method I suggested to the client was to use three of our model 3208 (8 SCFM) vortex tubes, allowing for direct connection of the vortex tube cold air output to each chamber. The cold air no longer has to cool down the cold air piping thus leaving more cooling power for each chamber, there is no back-pressure issue, and finally and probably most importantly would be the total air consumed would only be 24 SCFM in this case (3 x 8 SCFM) vs. 30 SCFM with a single larger vortex tube. That is a 20% savings on compressed air use in a straight up comparison. Depending on how many hours a day the system would be used, the difference in purchase price could be made up by lower operating cost in less than a year.

Neal Raker
Application Engineer
nealraker@exair.com

Adjustable Spot Cooler Keeps Wheel Speed Sensors Cool for Assembly Operations

Published on by Neal RakerLeave a comment

abs_wheel_sensor

Wheel speed sensors are part of the feedback loop for a vehicle’s computer system to monitor the condition of the various systems and react accordingly. The wheel speed sensors monitor wheel speed at all four wheels and compares them to one another to activate traction control or the anti-locking braking system depending on the conditions of the road and traffic situation.

One of our customers recently called in and was looking for a way to keep these sensors cool prior to the manufacturing assembly process. Cooled sensors made for much easier installation into the wheel hub assembly.

The customer has a small cooling chamber of about 2 cubic feet and they wanted to keep it at 0°C. The external environment has a maximum, summer-time temperature of about 40°C. There is not any heat being produced by the sensors themselves, so we only have to worry about the external environment temperature.

The customer did not want to go the route of making a major purchase of a pre-made cooling chamber. Their preference was to make their own cooling chamber, using what they already had in place and using a Vortex Tube to provide the cooling. Running the necessary calculation, the application required approximately 280 Btu/hr. to maintain the target temperature.

In order to generate 280 Btu/hr. with 0°C as the target temperature, the net output flow of the Vortex Tube needs to be at approximately -10 to -15 degrees C. It is then just a matter of determining how much volume of cold air flow that is necessary to accomplish the goal. For this application, a 30 SCFM vortex tube set at 50% cold fraction and operating at 100PSIG would get the application to where it needs to be in terms of providing sufficient cooling power.

I did throw one curve to the customer though. Instead of suggesting a plain Vortex Tube, I suggested our model 3730 (Adjustable Spot Cooler). The reasons for suggesting the Adjustable Spot Cooler are that is it much more user friendly as it has heat shielding and sound muffling already built into its design. Also, it has complete flexibility to change the temperature of the output flow to be in the range that we needed for the application.

ASC

They took the advice and went with my suggestion. They now have a refrigerated chamber at the assembly area in order to chill down the sensors and problem is solved.

If you have a similar application where you need to create a small, chilled space on the manufacturing floor, consider building your own unit with a Vortex Tube or even Adjustable Spot Cooler as your cooling source.

Neal Raker, Application Engineer
nealraker@exair.com