The importance of accurately characterizing the thermal conductivity (k) of agricultural products has been previously discussed here. Furthering this discussion is understanding how thermal conductivity is influenced by temperature. This can be directly related to process safety such as freezing of raw materials, packaging and storage, as well as cooking requirements.
C-Therm’s Trident Platform provides users with 3 different yet complementary methods for thermal property characterization allowing for a well-rounded kit with the ability to test solids, liquids, powders and pastes at sub-ambient, ambient and elevated temperature conditions. This variety in measurement technique is particularly applicable to the agricultural industry which encompasses a vast assortment of sample types including live-stock products, natural organic materials, processed foods and more.
All results presented herein were obtained using the TPS method on the Trident Platform. The TPS technique gives users with the ability to manually set up experimental parameters and tune them specifically to their materials of interest. C-Therm offers different sized TPS sensors to accommodate a wide range of sample types/sizes as well as high-temperature options. Learn more about Trident.
Figure 1. Measuring the Thermal Conductivity of Honey Using C-Therm’s Flex Transient Plane Source (TPS)
Due to honey’s relatively viscous nature, thermal transport primarily occurs via diffusion rather than convection like in many other liquids. As such, trends in the thermal performance of honey can be better understood by viewing it as a solid material such as a polymer. This can be related to the large number of hydrocarbons and relatively low amount of water content (15-18 wt%) present in the sample matrix. In this work, a no name honey was tested from 5 to 55ºC and the thermal conductivity was found to range from 0.569 to 0.362 W/mK, respectively.
Experimental results followed a trend similar to what would be expected in a typical polymer (i.e. thermal conductivity decreased as a function of temperature). As temperature increases, thermal transport pathways become less efficient and heat dissipation capabilities are decreased. It should be noted that the stated results are that of a specific honey sample and different brands/products thermal properties may vary due to factors such as water content, additives, etc.
As a means of comparison, the RT value obtained using TPS was compared to previous data obtained by C-Therm using the Modified Transient Plane Source (MTPS), as well as recent (2018) work published by Monika Bozikova et al. who employed the Transient Hot Wire (THW) technique. All three methods are stated to have an accuracy rating of 5% or better and as shown in the Figure 3 results from all three methods are in good agreement.
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