Radiation Errors in Air Ducts Under Nonisothermal Conditions Using Thermocouples, Thermistors, and a Resistance ThermometerU.S. National Bureau of Standards, 1969 - 12 pages Studies were made to determine the radiation error in temperature measurements made with thermocouples, thermistors, and a resistance thermometer in moving air at velocities ranging from 300 to 1300 fpm when the temperature of the duct wall surrounding the air stream was from 0 to 50 deg F higher than that of the air in the center of the duct. To eliminate all but the variable under study, conduction errors were minimized to a point where they were almost nonexistent by using Chromel P-constantan thermocouple wire and by employing other techniques. Radiation effects were studied when the probe housing the three types of temperature sensors was unshielded and again when it was shielded. Under the test conditions that prevail in the testing of air conditioners and heat pumps in laboratories, it should be possible to reduce the error in temperature measurement of the moving air to about 0.2 deg F by a suitable combination of air mixers, duct insulation, radiation shields, and calibration techniques. (Author). |
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Page 4
... fabricated from No. 36 Chromel P - constan- tan wire supported by a plastic cage - like structure . The six lead wires were bare and were strung back and forth in the cage so that about 5 in of the wire was exposed to the moving air ...
... fabricated from No. 36 Chromel P - constan- tan wire supported by a plastic cage - like structure . The six lead wires were bare and were strung back and forth in the cage so that about 5 in of the wire was exposed to the moving air ...
Page 5
... fabricated especially for the refer- ence sensor . The sensor and its shields were placed immediately upstream from the probe . These are shown in figure 6. The diameter of the inner shield was 1 in and of the outer shield was 2 in ...
... fabricated especially for the refer- ence sensor . The sensor and its shields were placed immediately upstream from the probe . These are shown in figure 6. The diameter of the inner shield was 1 in and of the outer shield was 2 in ...
Page 9
... fabricated from No. 36 wire ( AWG ) . Array was immediately upstream from the probe . velocity of 500 fpm . It was for the array of ther- mocouples immediately upstream from the probe . The cross - sectional temperatures , it will be ...
... fabricated from No. 36 wire ( AWG ) . Array was immediately upstream from the probe . velocity of 500 fpm . It was for the array of ther- mocouples immediately upstream from the probe . The cross - sectional temperatures , it will be ...
Page 12
... fabricated with material having a lower emissivity than methyl methacry- late , which has an emissivity of about 0.7 to 0.9 , or one which is wrapped with a covering of reflective foil , would have a smaller radiation error when used as ...
... fabricated with material having a lower emissivity than methyl methacry- late , which has an emissivity of about 0.7 to 0.9 , or one which is wrapped with a covering of reflective foil , would have a smaller radiation error when used as ...
Common terms and phrases
15 cents 50 deg F access door Achenbach air mixing air velocity aspirated assembly automatic data processing Building Science Series Bureau of Standards calibration Cement and Concrete Chromel P-constantan thermocouple Concrete Properties Conditions Using Thermocouples curves deg F 28 determined Dewar flask diameter DIFFERENCE IN TEMPERATURE duct wall error in temperature experimental Faison FPM UNSHIELDED heat pumps heated section ice bath immediately upstream inlet air inner shield Institute for Applied instrument room insulated Interrelations Between Cement junction box large reference sensor mercury-in-glass thermometers minimizing conduction errors moving air National Bureau Nonisothermal Conditions OBSERVED READINGS platinum resistance thermometer Portland Cement radiation error radiation shields Reinhold Publ SENSORS dag F set of shields shielded probe shielded sensors shown in figure small reference sensor techniques temperature difference temperature measurement temperature sensors test conditions test duct test probe thermal conductivity thermistors thermo thermocouple wire types of sensors U.S. Government Printing velocity of 300
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