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 2
... ther- mometer was used instead of a mercury - in - glass thermometer . 2 Throughout this paper , the more substantive results are given not only in the British units now customary in this country , but also in the International System ...
... ther- mometer was used instead of a mercury - in - glass thermometer . 2 Throughout this paper , the more substantive results are given not only in the British units now customary in this country , but also in the International System ...
Page 3
... ther helped minimize conduction error because of their low thermal conductivity , which was about 6 Btu hr 1 ft deg F - 1 for chromel and about 13 Btu hrft deg F - 1 for constantan as compared copper which is about 200 Btu hr 1 ft -1 ...
... ther helped minimize conduction error because of their low thermal conductivity , which was about 6 Btu hr 1 ft deg F - 1 for chromel and about 13 Btu hrft deg F - 1 for constantan as compared copper which is about 200 Btu hr 1 ft -1 ...
Page 4
... ther- mocouples were placed in two rings around the in- side surface of the duct , one upstream and one downstream from the probe , as well as on the inner surface of the duct along the bottom of the entire length of its measuring ...
... ther- mocouples were placed in two rings around the in- side surface of the duct , one upstream and one downstream from the probe , as well as on the inner surface of the duct along the bottom of the entire length of its measuring ...
Page 5
... of the resistance thermometer in the probe were compared in still air with ob- served readings of another resistance ther- mometer calibrated by the NBS Thermometry 5 laboratory . At the four temperatures within the range of.
... of the resistance thermometer in the probe were compared in still air with ob- served readings of another resistance ther- mometer calibrated by the NBS Thermometry 5 laboratory . At the four temperatures within the range of.
Page 6
... ther- mocouples were read . Analysis showed that the contribution of self - heating of the resistance thermometer or the thermistors due to current flow was negligible . When a reference sensor was calibrated , the cage - like structure ...
... ther- mocouples were read . Analysis showed that the contribution of self - heating of the resistance thermometer or the thermistors due to current flow was negligible . When a reference sensor was calibrated , the cage - like structure ...
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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