In this paper, the differences in mechanical strength tested during the static tensile and compression test of Scots pine (Pinus sylvestris L.), European larch (Larix decidua) and Norway spruce (Picea abies) wood exposed to continuous soaking in water with a salinity of 7‰ were determined. The value of salinity corresponded to the average salinity on the Polish Baltic coast. This paper also aimed to examine the content of mineral compounds absorbed during four cycles of two weeks each. The essence of the statistical research was to identify the effect of the mineral range compounds and salts depending on the mechanical strength of the wood. Based on the results of the experiments, it can be concluded that the medium used has a specific effect on the wood species’ structure. The effects of soaking on the wood parameters depend obviously on the type of wood. A tensile strength test of pine, as well as the tensile strength other species, was enhanced by incubating it in seawater. A native sample’s initial mean tensile strength was 82.5 MPa, which increased to 94.8 MPa in the last cycle. It was found that the larch wood had the lowest tensile strength difference (9 MPa) of the woods studied in the current study. Four to six weeks of soaking was necessary to notice an increase in tensile strength.
The aim of this article is to show how the situation of domestic biofuels in Poland and the alternative fuels sector is changing. On the basis of our own research and the available literature, changes in the production potential of Poland in the field of alternative fuels/biofuels are examined. Moreover, the reasons for changes in the production structure are analyzed. The flexibility of production potential to changes in legal conditions is assessed, and the value of sectors and their future are determined. This paper discusses legal and market aspects related to selected renewable energy sources used in Polish transport. Based on a review of literature and statistical data, the production and use of methyl esters and bioethanol are characterized in detail. Analysis of legal regulations enables the presentation of targets regarding renewable energy source (RES) use in transport by 2030. The results of studies conducted in 2020 are discussed with regard to the value (attractiveness) of methyl esters, bioethanol, electromobility and liquid bio-hydrocarbons, and these are compared and contrasted with the result from earlier years since 2010.
The objective of this paper was to create a mathematical model of vacuum drops in a form that enables the testing of the impact of design parameters of a milking cluster on the values of vacuum drops in the claw. Simulation tests of the milking cluster were conducted, with the use of a simplified model of vacuum drops in the form of a fourth-degree polynomial. Sensitivity analysis and a simulation of a model with a simplified structure of vacuum drops in the claw were carried out. As a result, the impact of the milking machine’s design parameters on the milking process could be analysed. The results showed that a change in the local loss and linear drag coefficient in the long milk duct will have a lower impact on vacuum drops if a smaller flux of inlet air, a higher head of the air/liquid mix, and a higher diameter of the long milk tube are used.
The goal of the work was to propose and verify the model of temperature changes of the convective dried biomass depending on the drying time. The algebraic temperature model of the convective dried solid, giving the possibility of its direct calculation, was based on the logistic function of growth. Temperature model was verified for convective dried biomass: vegetable and wood (poplar and willow wood chips) significantly differing in initial moisture content. Parameter W in the temperature model, defined as the coefficient of temperature rate changes reaches greater values in higher temperature of drying air and for wood biomass which has lower initial moisture content. Empirically selected parameter W allows to verify the temperature model with the relative error less than 5%.
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