A New Steady-State Calorimeter for Measuring Heat Transfer through Cryogenic Insulation

Abstract

One of the most important problems in the continuing effort to understand the heat transfer mechanism in cryogenic insulation and to develop more effective insulating materials is the accurate determination of the effective thermal conductivity of insulating materials. Although a number of calorimeters [^1–5] have been designed and built to date, almost all of them suffer from certain limitations which restrict their accuracy and limit the temperature range over which they can yield satisfactory data. Among the best known efforts in the construction and use of calorimeters are the flat-plate calorimeters [^1–4] and the cylindrical calorimeter [⁵], The flat-plate calorimeters can potentially yield high accuracy with a number of materials, but they require extensive guards to shield against extraneous heat transfer, are difficult to operate, expensive to build [⁴], require a long time before reaching steady state, and may necessitate the use of expensive electronic feedback equipment to satisfy the demands of high accuracy [²]. The available cylindrical calorimeters are simple to operate and cheaper to build, but they can only operate over limited temperature ranges and are subject to errors due to conduction along the fill and vent piping and uncertainty as to whether or not they actually achieve steady state.