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
... unshielded and again when it was shielded . The studies showed that when the sensors were unshielded and the temperature difference between the duct wall and the air was 50 deg F ( 28 K , approximately ) , the error in the sensors was ...
... unshielded and again when it was shielded . The studies showed that when the sensors were unshielded and the temperature difference between the duct wall and the air was 50 deg F ( 28 K , approximately ) , the error in the sensors was ...
Page 5
... unshielded . Removable legs for the shield are shown in lower left . The errors in uncalibrated temperature - sensing devices are usually determined by comparison of their indications with those of a secondary or pri- mary standard ...
... unshielded . Removable legs for the shield are shown in lower left . The errors in uncalibrated temperature - sensing devices are usually determined by comparison of their indications with those of a secondary or pri- mary standard ...
Page 9
... unshielded sen- sors under the conditions of 1300 fpm ( 6.6 m / s ) air velocity and a △ t of 50 deg F ( 28 K ) , the observed error was about 1 deg F ( 0.6 K ) . For 500 fpm ( 2.5 m / s ) and 300 fpm ( 1.5 m / s ) , under the same ...
... unshielded sen- sors under the conditions of 1300 fpm ( 6.6 m / s ) air velocity and a △ t of 50 deg F ( 28 K ) , the observed error was about 1 deg F ( 0.6 K ) . For 500 fpm ( 2.5 m / s ) and 300 fpm ( 1.5 m / s ) , under the same ...
Page 10
... ( UNSHIELDED ) 1300 FPM ( UNSHIELDED ) △ THERMISTOR • THERMOCOUPLE □ RESISTANCE THERMOMETER 500 FPM ( SHIELDED ) -THERMOCOUPLE -THERMISTOR -RESISTANCE THERMOMETER 0.5 O 5 10 O 40 45 50 15 20 25 30 35 DIFFERENCE IN TEMPERATURE OF DUCT ...
... ( UNSHIELDED ) 1300 FPM ( UNSHIELDED ) △ THERMISTOR • THERMOCOUPLE □ RESISTANCE THERMOMETER 500 FPM ( SHIELDED ) -THERMOCOUPLE -THERMISTOR -RESISTANCE THERMOMETER 0.5 O 5 10 O 40 45 50 15 20 25 30 35 DIFFERENCE IN TEMPERATURE OF DUCT ...
Page 11
... unshielded sensors due to radiation was about 3.8 deg F ( 2.1 K ) at 300 fpm ( 1.5 m / s ) 3.0 deg F ( 1.7 K ) at 500 fpm ( 2.5 m / s ) . At 1300 fpm ( 6.6 m / s ) the expected error with the sensors unshielded would be about 1 deg F ...
... unshielded sensors due to radiation was about 3.8 deg F ( 2.1 K ) at 300 fpm ( 1.5 m / s ) 3.0 deg F ( 1.7 K ) at 500 fpm ( 2.5 m / s ) . At 1300 fpm ( 6.6 m / s ) the expected error with the sensors unshielded would be about 1 deg F ...
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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