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 1
Joseph C. Davis. Radiation Errors in Air Ducts Under Nonisothermal Conditions Using Thermocouples , Thermistors , and a Resistance Thermometer Joseph C. Davis * Studies were made to determine the radiation error in temperature ...
Joseph C. Davis. Radiation Errors in Air Ducts Under Nonisothermal Conditions Using Thermocouples , Thermistors , and a Resistance Thermometer Joseph C. Davis * Studies were made to determine the radiation error in temperature ...
Page 2
... radiation errors for three common types of sensors , used with or without shielding , for a range of air velocities ... error was directly assessed by obtaining measurements with and without radiation shields and comparing them with ...
... radiation errors for three common types of sensors , used with or without shielding , for a range of air velocities ... error was directly assessed by obtaining measurements with and without radiation shields and comparing them with ...
Page 3
... errors due to reradiation of heat from the plastic tubing to the wires ( figs . 1 and 2 ) . The leads running from the ... error because of their low thermal conductivity , which was about 6 Btu hr 1 ft deg F - 1 for chromel and about 13 ...
... errors due to reradiation of heat from the plastic tubing to the wires ( figs . 1 and 2 ) . The leads running from the ... error because of their low thermal conductivity , which was about 6 Btu hr 1 ft deg F - 1 for chromel and about 13 ...
Page 4
... radiation error . The flow was turbulent in the region close to the duct wall even at 300 fpm and the low time constant of the thermocouples caused difficulty in making the thermocouple read- ings in this region . This difficulty was ...
... radiation error . The flow was turbulent in the region close to the duct wall even at 300 fpm and the low time constant of the thermocouples caused difficulty in making the thermocouple read- ings in this region . This difficulty was ...
Page 6
... error in the reference sensor due to radiation or conduction at a velocity of 1400 fpm , even for a At of 50 deg F. This comparison showed that the error of the large reference sensor in the long 10 - in set of shields reached a value ...
... error in the reference sensor due to radiation or conduction at a velocity of 1400 fpm , even for a At of 50 deg F. This comparison showed that the error of the large reference sensor in the long 10 - in set of shields reached a value ...
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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