New Development in Design of Equipment for Measuring Thermal Conductivity and Heat Flow

Thermal conductivity of materials and heat transmission through complex structures have been studied for many years at the Refrigeration Division of the Trondheim University. This paper describes some of the recent developments in test equipment design and operation.

One fully-automatic guarded hot plate apparatus of the unidirectional type for high accuracy has been put in operation. It is capable of measuring at cold plate temperatures between 80 and 330 K at a typical difference of 10 K. A special method of accelerated balancing was introduced, and is used successfully for a number of different measuring purposes. A description of the control system is given.

The study of convection influence in full-size insulations is continued. A part of this work is done using a large-scale hot box apparatus with a special edge design. Further, a large guarded hot plate equipment with a measuring area of 2 by 3 m² for the same purpose is under construction. The temperature range for this equipment has been extended to 90 K on the cold side with a view to the testing of liquid natural gas tank insulations.

Another important project concerns the heat transmission in natural ground freezing and the use of insulation for frost protection. Three guarded hot plate apparatus of special design are built to measure thermal conductivity of soils and building materials. These apparatus operate at cold plate temperatures between 200 and 320 K.

Some work on the development of transient methods for heat conductivity measurement is also recorded.