Tag: cooling capacity

Electrical Cabinet Cooling with EXAIR Cabinet Cooler System

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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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Twitter: @EXAIR_BB

Video Blog: Medium Vortex Tube Cooling Kit

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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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Find us on the Web
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Twitter: @EXAIR_BB

Wearing Out Your Sole

Published on by John BallLeave a comment
3925 Adjustable Spot Cooler
3925 Adjustable Spot Cooler

A shoe manufacturer had a special abrasion test that was required by his customer to test special rubber compounds. The set up was to run a small chain across the bottom of the rubber sole.  The chain was looped to continuously rub against the sole of the shoe.  As they began their wear testing, they noticed that the chain was getting hot from the friction.  The heat would get high enough to change the composition of the rubber and cause a premature failure.  To properly test for wear, they needed to cool the chain.

As they discussed their application with me, they required the chain to be at a specific temperature. I suggested the model 3925 Adjustable Spot Cooler System.  This system comes with a dual point hose kit, a magnetic base, a filter separator, and two additional generators.  The generators of the Adjustable Spot Cooler are a piece which controls the total volume of air through the cooler. They can be switched in and out to produce more or less cooling capacity of the Adjustable Spot Cooler. The main concern was to keep the chain temperature constant.  With a temperature control knob and the additional generators, they could dial in the cooling capacity to keep the chain at the desired temperature.  If the chain was too cold, the sole would not wear properly, and if the chain was too hot, it would change the composition of the rubber material.

They mounted the Adjustable Spot Cooler to the abrasion machine with the dual points blowing on each side of the chain. They quickly noticed that they could keep the chain cooler than the specified temperature.  As a trial, they replaced the generator to the 30 SCFM (850 SLPM) flow rate.  This increased the cooling capacity of the Spot Cooler.  With the higher cooling capacity, they could increase the speed of the abrasion machine to shorten the failure cycle.  This was a great benefit to have as they were testing different rubber compounds to determine the best product; a pronounced advantage in research and development.

If you find out that heat is causing problems in your application, you can contact an Application Engineer at EXAIR for help in finding the correct cooling product. In this instance, friction was the culprit and the Adjustable Spot Cooler was the solution.

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

The Effect of Back Pressure on a Vortex Tube Part 2, Calculating Btu/Hr.

Published on by Brian FarnoLeave a comment

My previous blog post was about how Vortex Tubes react when there is back pressure due to a restriction on either the hot or cold discharge of the Vortex Tube.  In it I mentioned that there is a formula to calculate what the cooling capacity (Btu/Hr) will be if there is no way to avoid operating the Vortex Tube without back pressure on the discharge. That is the calculation focus of this blog – calculating Btu/hr of a Vortex Tube with back pressure.

To continue with the same example, the calculations from the previous blog are shown below.  Last time the example Vortex Tube was operating at 100 psig inlet pressure, 50% cold fraction, and 10 psi of back pressure. We will need some additional information to determine the Btu/Hr capacity. The additional information needed is the temperature of the supplied compressed air as well as the ambient air temperature desired to maintain.  For the example the inlet compressed air will be 70°F and desired ambient air temperature to maintain will be 90°F.

(100 psig + 14.7 psia) / (10 psig + 14.7 psia) = X / 14.7 psia
4.6437 = X / 14.7
X= 14.7 * 4.6437
X = 68.2628
(Values have been rounded for display purposes)

The calculation above gives the compensated operating pressure (X = 68.2628) which will be needed for the BTU/hr calculation. The rated air consumption value of the Vortex Tube will also need to be known.  A 30 SCFM rated generator will be used for this example, the normal BTU capacity of a Vortex Tube with a 30 SCFM generator is 2,000 BTU/hr.

First, determine the new consumption rate by establishing a ratio of the compensated pressure (68.2628 psi) against the rated pressure (100 psi) at absolute conditions (14.7 psia).

(68.2628 PSIG + 14.7 (atmospheric pressure)) / (100 PSIG (rated pressure) + 14.7) = .7233
.7233 x 30 SCFM  = 21.7 SCFM Input 

Second, the volumetric flow of cold air at the previously mentioned cold fraction (50%) will be calculated.  To do this multiply the cold fraction setting (50%) of the Vortex Tube by the compensated input consumption (21.7 SCFM) of the Vortex Tube.

50% cold fraction x 21.7 SCFM input = 10.85 SCFM of cold air flow

Third, the temperature of air that will be produced by the Vortex Tube will need to be calculated.  For this consult the Vortex Tube performance chart which is shown below. To simplify the example the compensated operating pressure (68.2628 psi) will be rounded to 70 psig and to obtain the 70 psig value the mean between 80 psig and 60 psig performance from the chart will be used.

Cold Fraction
EXAIR Vortex Tube Performance Chart

For the example: A 70 psig inlet pressure at 50% cold fraction will produce approximately an 88°F drop.
Fourth, subtract the temperature drop (88°F) from the temperature of the supplied compressed air temperature (70°F).

70°F Supply air – 88°F drop = -18°F Output Air Temperature

Fifth,  determine the difference between the temperature of the air being produced by the Vortex Tube (-18°F) and the ambient air temperature that is desired (90°F).

90°F ambient – -18°F air generated = 108°F difference.

The sixth and final step in the calculation is to apply the answers obtained above into a refrigeration formula to calculate BTU/hr.

1.0746 (BTU/hr. constant for air) x 10.85 SCFM of cold air flow x 108°F ΔT = 1,259 BTU/hr.

In summary, if a 2,000 BTU/hr. Vortex tube is operated at 100 psig inlet pressure, 50% cold fraction, 70°F inlet air to maintain a 90°F ambient condition with 10 psi of back pressure on the outlets of the Vortex Tube the cooling capacity will be de-rated to 1,259 BTU/hr.  That is a 37% reduction in performance.  If a back pressure cannot be avoided and the cooling capacity needed is known then it is possible to compensate and ensure the cooling capacity can still be achieved.  The ideal scenario for a Vortex Tube to remain at optimal performance is to operate with no back pressure on the cold or hot outlet.

Brian Farno
Application Engineer Manager
BrianFarno@EXAIR.com
@EXAIR_BF