Theoretical and Experimental Study of Single-Needle Thermal Conductivity Probe

The thermal conductivities of materials (k However, due to the vast number of designs and applications of TCPs, sources of errors with using the probes are diverse. As a result, in this thesis, possible sources of errors in TCPs (single needle) were investigated. The sources include probe sizes, heating powers, sampling media, selection of TCP materials, location of the thermocouple, axial heat conduction, thermal contact resistance, initiating time t

Theoretical and Experimental Study of Single-Needle Thermal Conductivity Probe

The thermal conductivities of materials (k However, due to the vast number of designs and applications of TCPs, sources of errors with using the probes are diverse. As a result, in this thesis, possible sources of errors in TCPs (single needle) were investigated. The sources include probe sizes, heating powers, sampling media, selection of TCP materials, location of the thermocouple, axial heat conduction, thermal contact resistance, initiating time t

Testing Study on Moisture Content Effect on Thermal Conductivity for Clay

Thermal conductivity is one of the key factors influence the heat exchange performance of Ground-coupled heat pump systems (GCHP), which is effected significantly by soil moisture content around the ground heat exchanger system. The clay thermal conductivity under moisture content of 0, 5%, 10%, 15%, 20%, 25% and 30% were determined through thermal conductivity probe experiment. The results showed a variation with three phases of the thermal conductivity changes with clay moisture content, that firstly, the thermal conductivity increased slowly with a moisture content of 0~5%, secondly, which sharply increased with a high positive linear correlation when the moisture content was 5%~25%, then the growth tendency was slow even began to fall, as well as the correlation equation of the second phase was fitted. This study provides methodological and theoretical references for the further research on the influence factors of thermal conductivity under various situations.

Estimation of thermal conductivity of short pastry biscuit at different baking stages

Thermal conductivity of a food material is an essential physical property in mathematical modelling and computer simulation of thermal processing. Effective thermal conductivity of non-homogeneous materials, such as food matrices, can be determined experimentally or mathematically. The aim of the following research was to compare the thermal conductivity of short pastry biscuits, at different baking stages (60-160 min), measured by a line heat source thermal conductivity probe and estimated through the use of thermo-physical models. The measures were carried out on whole biscuits and on powdered biscuits compressed into cylindrical cases. Thermal conductivity of the compacted material, at different baking times (and, consequently at different moisture content), was then used to feed parallel, series, Krischer and Maxwell-Eucken models. The results showed that the application of the hot wire method for the determination of thermal conductivity is not fully feasible if applied directly to whole materials due to mechanical changes applied to the structure and the high presence of fats. The method works best if applied to the biscuit component phases separately. The best model is the Krischer one for its adaptability. In this case the value of biscuit thermal conductivity, for high baking time, varies from 0.15 to 0.19 Wm^–1 K^–1, while the minimum, for low baking time, varies from 0.11 to 0.12 Wm^–1 K^–1. These values are close to that reported in literature for similar products.