In general, processing and manipulation with foods and food raw materials have significant influence on their physical properties. The article is focused on thermophysical parameters measurement of selected foods and food raw materials. There were examined thermal conductivity and thermal diffusivity of selected materials. For detection of thermal parameters was used instrument Isomet 2104, which principle of measurement is based on transient methods. In text are presented summary results of thermal parameters measurement for various foods and food raw materials as: granular materials -corn flour and wheat flour; fruits, vegetables and fruit products -grated apple, dried apple and apple juice; liquid materials -milk, beer etc. Measurements were performed in two temperature ranges according to the character of examined material. From graphical relations of thermophysical parameter is evident, that thermal conductivity and diffusivity increases with temperature and moisture content linearly, only for granular materials were obtained non-linear dependencies. Results shows, that foods and food raw materials have different thermal properties, which are influenced by their type, structure, chemical and physical properties. From presented results is evident, that basic thermal parameters are important for material quality detection in food industry.

The article deals with the impact of selected external factors on the temperature of photovoltaic module surfaces. Primary aim of this research is creation of temperature model for photovoltaic module, which would be usable under the real climatic conditions in Central Europe region. Fully autonomous measuring system was designed and created for temperature monitoring of different parts of photovoltaic modules. The measuring system consists of 24 temperature sensors, voltage inverter, control unit, transfer modules, receiver modules and temperature measuring module. The experiments were performed on photovoltaic modules installed on the roof of the University of Life Sciences in Prague during summer 2018. The temperature of photovoltaic modules significantly depends on the climatic conditions, which were monitored by the weather station. The temperature and the solar radiation dependencies for polycrystalline and monocrystalline photovoltaic modules were obtained in experiments conducted. The temperature relations were measured for different parts of photovoltaic module – active parts of photovoltaic module, frame, non-active parts of photovoltaic module, as well as ambient temperature. Final mathematical description of polynomial graphical dependencies was obtained after application of fitting procedure and regression analysis.

Due to expansion of utilisation of photovoltaics in ordinary households, the question arises how this phenomenon affects the electric power of photovoltaic modules. The article deals with the electric power analysis of photovoltaic modules as a function of two very important factors. The first examined factor was partial shading, and the second factor was the intensity of reflected radiation. In order to determine the dependence of module power on the aforementioned parameters, a measurement system under laboratory conditions has been prepared. For identification of the reflected radiation effect on the power of the photovoltaic module, a series of measurements was performed on 7 different surfaces with the same radiation source. It is evident from obtained experimental result that the ratio of reflected irradiation on the solar module power is 1.29%. By simulation of partial shading of photovoltaic module, the decrease of 86.15% in its output power was identified.

Moisture content is one of the most important properties of wood. The primary purpose of this paper is to examine the dependence between thermal properties and different moisture contents of softwood, hardwood and medium hardwood samples with dimensions of 100 x 100 mm and a thickness of 10 mm (measured using the transient method). Different moisture contents of the wood samples under consideration were achieved by a gradual drying treatment in the laboratory setting. The final results obtained represent the arithmetic means computed from ten sets of measurements. The measured relationship between the thermal conductivity and the mass specific heat of the wood samples was found to indicate an increasing trend, whereas the relationship between the thermal diffusivity and the moisture content of the wood samples showed a non-linear decreasing trend. On the basis of the results obtained, it can be concluded that the thermal properties of wood are greatly affected by the type of wood and changes in the wood moisture content, which mainly depend on wood structure and water conduction in wood.

Božiková M., Hlaváč P., Híreš Ľ., Hlaváčová Z., Valach M., Vozárová V., Malínek M. (2017): Temperature effect on various biooils physical parameters. Res. Agr. Eng., 63: 145-151.The article deals with thermal and rheological properties of two selected biooils (PL 64S -sample No. 1, and PL 04N -sample No. 2). For thermal parameters measurements, Hot wire method was used, for detection of rheological parameters rheometer Anton Paar MCR 102 was used and the density was measured by densimeter DM 40. For both biooil samples, two series of thermophysical parameters measurements were made. In the first series thermal conductivity and thermal diffusivity were measured at constant laboratory temperature. The second series was focused on identification of thermophysical parameters changes during temperature stabilisation. The parameters as dynamic viscosity, kinematic viscosity and density were measured in the temperature range (20-50°C). For samples with constant temperature basic statistical characteristics were calculated -standard deviation and probable error in %. For relations of thermal and rheological parameters to temperature nonlinear dependencies were obtained. The polynomial functions of the second degree were used for thermal parameters and exponential functions for rheological parameters.