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Author: Ronald J. Holyer Publisher: ISBN: Category : Heat Languages : en Pages : 112
Book Description
A system has been designed and constructed to measure thermal conductivity by the series comparative method in the temperature range 4 to 300K. A sample temperature of 77K was reached when the cylindrical sample chamber 3-1/4 inches in diameter and 8-3/4 inches long was evacuated to a pressure of 0.000003 Torr and submerged in a bath of liquid nitrogen held in a 5-1/2 liter stainlesssteel dewar. Temperatures as low as 4.2K could be obtained if the sample chamber were submerged in liquid helium. Temperatures between that of the liquid bath and room temperature were obtained by electrical heating. A simple Wheatstone bridge circuit, one arm of which was a copper resistance thermometer made from 140 ohms of B and S No. 36 copper wire, served to regulate automatically the electrical heating so as to give a drift in sample temperature of less than 0.002 deg/min. Measurements were attempted from 77K to 300K on a sample of n-type single-crystal silicon with an impurity concentration of 5X10 to the 15th power cu cm. Armco iron was used as a standard. Temperatures were measured with copper vs constantan thermocouples. The thermal conductivity of the sample was found to range from 8.7 watt/cm-degK at 98K to 1.8 watt/cm-degK at 255K. These values agree with those of Carruthers et al. Within 7% and of Glassbrenner and Slack within 10%. (Author).
Author: Ronald J. Holyer Publisher: ISBN: Category : Heat Languages : en Pages : 112
Book Description
A system has been designed and constructed to measure thermal conductivity by the series comparative method in the temperature range 4 to 300K. A sample temperature of 77K was reached when the cylindrical sample chamber 3-1/4 inches in diameter and 8-3/4 inches long was evacuated to a pressure of 0.000003 Torr and submerged in a bath of liquid nitrogen held in a 5-1/2 liter stainlesssteel dewar. Temperatures as low as 4.2K could be obtained if the sample chamber were submerged in liquid helium. Temperatures between that of the liquid bath and room temperature were obtained by electrical heating. A simple Wheatstone bridge circuit, one arm of which was a copper resistance thermometer made from 140 ohms of B and S No. 36 copper wire, served to regulate automatically the electrical heating so as to give a drift in sample temperature of less than 0.002 deg/min. Measurements were attempted from 77K to 300K on a sample of n-type single-crystal silicon with an impurity concentration of 5X10 to the 15th power cu cm. Armco iron was used as a standard. Temperatures were measured with copper vs constantan thermocouples. The thermal conductivity of the sample was found to range from 8.7 watt/cm-degK at 98K to 1.8 watt/cm-degK at 255K. These values agree with those of Carruthers et al. Within 7% and of Glassbrenner and Slack within 10%. (Author).
Author: Jack Ekin Publisher: OUP Oxford ISBN: 0198570546 Category : Science Languages : en Pages : 704
Book Description
Written in an accessible and readable style, the book provides a truly integrated, step-by-step approach to the design and construction of low-temperature measurement apparatus. It presents a practical perspective of heat transfer, materials selection, construction techniques, wiring, thermometry, sample mounting, and electrical contacts, and recent developments in superconductor data analysis and scaling theory. The graphs, clear examples, and seventy appendix data tables are a treasure trove of practical information.
Author: Erik J. Offner Publisher: ISBN: Category : Heat Languages : en Pages : 120
Book Description
A steady state, axial flow thermal conductivity test apparatus was designed and constructed to operate between room temperature and approximately 4 Kelvin, and to be compatible with existing electronic instrumentation and a continuous flow cryostat. The test design included a radiation shield that had its temperature profile matched to that of the sample to minimize radiation heat transfer losses. The cryostat was used to provide the controllable, low temperature test environment in which the test apparatus would operate. A special wiring bundle was constructed to ensure proper connection of the test device to the required electronic instrumentation, which was controlled from a computer by custom written software. Once assembled, the thermal conductivity of a high purity copper sample was measured over the temperature range from 45 to 300 Kelvin and compared to literature recommended values. The test was performed a second time to check repeatability of the measurements over a range of temperature. Next, the thermal conductivity of a high purity niobium sample was measured and compared to literature recommended values. This test was also performed twice. When completed, these tests had demonstrated the accuracy and repeatability of the measurement of thermal conductivity by the test apparatus over the range of temperatures specified and over a range of conductivities. Finally, the thermal conductivity of a sample of the bulk metallic glass Vitreloy 1 was measured over the same temperature range. As far as was known, this was the first time the thermal conductivity of this particular material had been tested below 400 Kelvin.
Author: Ronald J. Holyer
Author: Ronald J. Holyer
Author: Ronald J. Holyer
Author: Thomas Edward Waterman
Author: Daniel R. Flynn
Author: Frederic I. Davis
Author: Jack Ekin
Author: Jacob Nicolaas Haasbroek
Author: 
Author: Gregg E. Childs
Author: Erik J. Offner