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
... difference between the duct wall and the air was 50 deg F ( 28 K , approximately ) , the error in the sensors was about 3.8 deg F ( 2.1 K ) for an air velocity of 300 fpm ( 1.5 m / s ) and 1.0 deg F ( 0.6 K ) for an air velocity of 1300 ...
... difference between the duct wall and the air was 50 deg F ( 28 K , approximately ) , the error in the sensors was about 3.8 deg F ( 2.1 K ) for an air velocity of 300 fpm ( 1.5 m / s ) and 1.0 deg F ( 0.6 K ) for an air velocity of 1300 ...
Page 2
... differences between the duct wall and the moving air , and to indicate application techniques that would minimize ... difference The tests employed a well - insulated , round metal duct with an air - mixing device near the in- let ...
... differences between the duct wall and the moving air , and to indicate application techniques that would minimize ... difference The tests employed a well - insulated , round metal duct with an air - mixing device near the in- let ...
Page 4
... difference in temperature between the moving air and the duct wall , there were low radial temperature gradients and almost no fluc- tuation in temperature in the region immediately surrounding the probe . Throughout the rest of the ...
... difference in temperature between the moving air and the duct wall , there were low radial temperature gradients and almost no fluc- tuation in temperature in the region immediately surrounding the probe . Throughout the rest of the ...
Page 5
Joseph C. Davis. 3. Calibration DIFFERENCE IN TEMPERATURE BETWEEN THE MOVING AIR AND THE DUCT. were shielded , fitted snugly into the inner of two 10 - in - long concentric shields just upstream from the probe . This reference sensor and ...
Joseph C. Davis. 3. Calibration DIFFERENCE IN TEMPERATURE BETWEEN THE MOVING AIR AND THE DUCT. were shielded , fitted snugly into the inner of two 10 - in - long concentric shields just upstream from the probe . This reference sensor and ...
Page 6
... difference between the observed readings of the two thermometers . The thermocouples , thermistors , and the large reference sensor were calibrated four times within a year , and the small reference sensor twice , one year apart . These ...
... difference between the observed readings of the two thermometers . The thermocouples , thermistors , and the large reference sensor were calibrated four times within a year , and the small reference sensor twice , one year apart . These ...
Common terms and phrases
15 cents 50 deg F access door Achenbach air velocity aspirated assembly automatic data processing Building Science Series Bureau of Standards cage-like structure Cement and Concrete change in performance 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 lead wires 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 set of shields shielded probe 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 unshielded sensors velocity of 300
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