Air Velocity and Temperature Measurement

How about doing a pitot tube traverse for the flowrate and using an RTD for the temperature?

I need some protable arrengment. I need manometer if i use pitot tube. Manometer is made by glass which may brake due to vibration. When i use RTD the reading can change with change of air velocity though the temperature is same. So can i proceed with pitot tube and RTD arrangment?. Please clarify me about my mentioned those doughts.

Another thing is that i also need two 4-20 mA outputs corresponds to velocity and temperature.

Suggest you use clear plastic tubing for your manometer if you are worried about breaking glass. Your RTD will indicate a change of temperature only if there is a change in temperature, irrespective of any air flow change.

This,

Wind Velocity Meter On GlobalSpec

and a thermometer.

Mining is one of the most inhospitable environments for technology and man. You have heat, dust, water, vibration, and explosive atmospheres to mention just a few of the worries of this subterranean environment. So if you cannot find test equipment already certified for this hostile environments, expect failures.

I am a NEBB (National Environmental Balancing Bureau) certified supervisor. It is very difficult to make a traverse without duct work and a rotating vane anemometer is a choice depending upon your accuracy requirements. Normally you want 6 to 10 diameters to get an accurate reading. A flow hood is the best bet and it can average the temp, the velocity and volume, they are spendy anywhere from 1 to 5 K.

Hope this helps

I hope you don't mind, I'm ' camping ' on a response you made to the mining ( minning? )

question. The info. you offered was great.

What is the difference between CAB , TAB and your specialty? If Plans & Specs refer to NEBB as a reference in checking airflow, does it automatically mean we have to have it certified?

Thanks,

Jim M.

2nd request, please help.

I hope you don't mind, I'm ' camping ' on a response you made to the mining ( minning? )

question. The info. you offered was great.

What is the difference between CAB , TAB and your specialty? If Plans & Specs refer to NEBB as a reference in checking airflow, does it automatically mean we have to have it certified?

Thanks,

Jim M.

You can measure the velocity of the airusing a pitot tube and temperature by a thermocouple or thermometer.

malay321,

What is the intent of your measurements? Determine the amount of heat added to the mining tunnel? Determine the amount of cooling air needed to keep the equipment from overheating? What is the material mined? Is it explosive? What are the electrical requirements involved? How often do you need to take these measurements (continuously, hourly, daily, etc.)? How accurate must the measurements be? All of these may affect the type of sensors/instrumentation used.

As noted by Guest, most pitot tubes require a duct extension in which to straighten the flow to produce a "traverse" to determine average flow. I'm assuming because of the moving equipment, no duct extensions are practical. Therefore, an anemometer is more logical, either a rotating vane or hot-wire anemometer (no hot-wire if explosive conditions). A hot-wire anemometer will also give you temperature readings. If your equipment is using a radiator for engine cooling there must be a fan producing the flow through the radiator. Measure the temperature of the fluid in the radiator, or surface temperature of the radiator, and adjust for the fan output, if known. If the fan is connected to the engine shaft, then measure the approximate flow using the anemometer. If continuous measurement is required, build brackets to support the equipment, watch the electrical requirements, consider wireless transmission of results due to movement of the equipment.

Be careful when trying to measure a air face velocity in turbulent air flow, we have done a large amount of work looking at flow profiles coming off a radiator faces using a laser doppler anemometer, at a wind tunnel in the UK. The first 20 mm of air coming off the radiator face would give you very poor data, depending on the spot measured, whether a fin or tube is present, fin type, etc. Small rotating vanes positioned in several areas across the radiator face, at least 50 mm from the face can give some repeatable and reliable data. Best of all if you can calibrate these with the radiator in a wind tunnel, you can achieve an accuracy of 3% with care. If trying to measure the mean air outlet air temperature, you must use several probes to get an idea of the temperature. We use 16 probes on the outlet of our test radiator when in the calorimetric wind tunnel, and you still struggle to get a true mean temperature. If cost isn't an option, position a fine mesh screen downstream of the radiator outlet and measure the screen temperature using a thermal imaging camera, this will give a good idea of the outlet temperature profile also. Just be careful with the emissisivity setup. A good contact you do these tests on a daily basis is Young Calibration, in the UK. They have several radiator and chargecooler heat exchanger wind tunnels. They can be contacted at www.youngcalibration.co.uk