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 6
... Curves show- ing the errors determined in this manner , and used for corrections for both reference sensors , are shown in figure 8. A small uncertainty is indicated at the bottom of the curves for each reference sensor by a horizontal ...
... Curves show- ing the errors determined in this manner , and used for corrections for both reference sensors , are shown in figure 8. A small uncertainty is indicated at the bottom of the curves for each reference sensor by a horizontal ...
Page 9
... curves showing the effect of radiation when the three sensors were measuring the temperature of the moving air at 500 and 1300 fpm , and figure 11 , curves showing the effect when the sensors were measuring this temperature at 300 fpm ...
... curves showing the effect of radiation when the three sensors were measuring the temperature of the moving air at 500 and 1300 fpm , and figure 11 , curves showing the effect when the sensors were measuring this temperature at 300 fpm ...
Page 11
... curves and the resistance thermometer curves , and from the con- stancy of their relative positions , that the thermo- couples had changed , not the thermistors or the resistance thermometer . Uncertainties occurring in the experimental ...
... curves and the resistance thermometer curves , and from the con- stancy of their relative positions , that the thermo- couples had changed , not the thermistors or the resistance thermometer . Uncertainties occurring in the experimental ...
Page 12
... curves will apply but will have a negative sign . Under conditions often occurring in a psychro- metric calorimeter for measuring the capacity of air - conditioning equipment when the air velocity is 1300 fpm and At = 5 deg F , the ...
... curves will apply but will have a negative sign . Under conditions often occurring in a psychro- metric calorimeter for measuring the capacity of air - conditioning equipment when the air velocity is 1300 fpm and At = 5 deg F , the ...
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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