Verification and validation of an advanced guardedhot plate for determination of thermal conductivity

Abstract

The Guarded hot plate method (GHP) is a widely used technique to measure thermal conductivity of thermal insulation specimens in steady-state conditions. In this paper, an advance of GHP has been developed in the Laboratory for Thermal technique and fire protection in Institute IMS. The innovative GHP has been applied for measuring thermal conductivity using additional heat flux meters. The design of this GHP is similar to the design of the plate for GHP apparatus; however, it has different design: smaller width of thermal barrier, which is filled with insulation glue. Heaters inside hot and guard plates are built from wire for thermocouples, which is a unique type of heater. Geometry of heater has been optimized inside plates to achieve uniform temperature distribution along the specimen surface. Temperature uniformity of guarded hot plate and energy balance were experimentally determined. The verification and validation results of improved GHP have been shown. The test method was validated comparing test results of thermal conductivity with results of the round-robin test. Four national companies participated in the round-robin comparison on thermal conductivity measurement by guarded hot plate method. The measurement was performed on the same specimen of thermal insulation material (expanded polystyrene) according to SRPS EN 12667 at temperatures ranging between 10?C-40?C. The measured thermal conductivity of all participants in the round-robin test was input data for statistical processing according to SRPS ISO 5725-2 and ISO 13528. To evaluate the performance of the participants, the ?z? score has been used. Measurements were conducted successively for all participants. Since 2020, the Accreditation Body of Serbia also approved this test method.

Design and thermal test of high-vacuum insulator for heat delivery pipes

“…The adopted solution involves isolating the hot pipe with high-vacuum technologies and a low-emissivity material coating to minimize radiative heat transfer. The work also proposes a new measurement technique for axial losses compensation inspired by the guarded plate method [14,15,16]. Experimental results show that this novel solution reduces the thermal losses by a factor of 5 compared to the traditional solutions, ensuring a primary energy saving [17] in the temperature between 100 °C and 250 °C and considering the same geometry and boundary conditions.…”