Cold Air Guns & Vortex Tubes - Adjusting the Temperature for your Application

Cold Air Guns and vortex tubes are popular spot cooling products that are used in a wide variety of applications, ranging from cooling cutting tools such as band saw and circular saw blades, router bits, lathe tools, HSS drills and milling cutters used for machining of metals, plastics, paper and wood. They are also commonly used to cool parts, dehumidify gas samples, cool sensors, test thermostats and many other applications where an instant and reliable supply of clean cold air is required. Vortex tubes and Cold Air Guns have no moving parts and use only a clean dry source of compressed air for creating cooling capacities up to 6000 btuh (1758 watts).

Since every application is unique and the cold air temperature and air flow required will be different, we wanted to ensure that customers have an easy way to adjust the air to meet their needs. On all of ITW Vortec’s vortex tubes and Cold Air Guns (except for our Mini Cold Air Guns) we have added an adjustable option. There is an adjustment valve at the hot end of all 106, 208, 308 and 328 series vortex tubes which allows the user to adjust the temperature of the cold air exiting out the opposite end. The same is true of Vortec’s Cold Air Gun product lines-there is a convenient adjustment knob on these models. When the valve or knob is turned counterclockwise, the temperature and the flow of the cold air is reduced. Correspondingly, as the valve is turned clockwise, the temperature and the flow of cold air is increased.

The temperature of the cold air depends not only on how the adjustment valve is set, it also depends on the temperature and pressure of the compressed air that is supplied to the vortex tube or Cold Air Gun. As the temperature of the compressed air increases, so does the cold air temperature, by the same amount. As the compressed air pressure drops, the cold air temperature rises. The performance specifications advertised for all of Vortec’s products is when 70°F (21°C) / 100 psig (6.9 bar) filtered and dried compressed air supplied to it. Many of these products can achieve temperatures that are 100°F (56°C) below the compressed air temperature.

Customers occasionally ask: “how do I adjust the vortex tube (or Cold Air Gun) for my application?”  For most customer’s applications, the maximum cooling capacity (or the most btus per hour) is required for best results. In these applications the customer does not require a specific temperature to be maintained, he or she is just looking for the quickest and most efficient way to keep something from overheating. In these applications maximum cooling capacity is achieved when the vortex tube is set at 60% to 70% cold fraction. This means that 60% to 70% of the air entering the vortex tube exits out the cold end. (And of course, 30% to 40% exits from the hot end.) For example, a model 610 Cold Air Gun consumes 15 scfm of air when it is operated at 100 psig. When it’s adjustment knob is adjusted to produce 9 to 10 cfm cold air flow, then it set at its maximum cooling capacity. Cooling capacity is calculated by this formula:

Cooling Capacity Formula

The chart indicates how far to turn the adjustment valve or the knob on the vortex tube or Cold Air Gun to achieve this 60 to 70% cold fraction, (this chart is applicable only when the compressed air inlet pressure is 100 psig (6.9 bar) and there is no backpressure imposed on the cold air flow):

Cold Air Gun Adjustable Cooling Chart

Other applications may require a specific cold air temperature, such as cooling a gas sample below its dew point temperature or cooling a thermostat below a certain set point. In these types of applications, the vortex tube or Cold Air Gun will need to be adjusted to the cold fraction that produces the desired temperature under the compressed air conditions (temperature, pressure and dew point) present. Consideration must be taken into account, that if any of the compressed air conditions change, then the cold air temperature will likely change also. Therefore if theapplication is critical, it may be important to monitor the compressed air conditions present at the vortex tube, to ensure they stay within the desired parameters.

As always, if you ever have any questions about how to get the most out of your compressed air system, please do not hesitate to call.

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