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Number of results: 11
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Abstract

In the paper, the results of numerical simulations of the steam flow in a shell and tube heat exchanger are presented. The efficiency of different models of turbulence was tested. In numerical calculations the following turbulence models were used: k-ε, RNG k-ε, Wilcox k-ω, Chen-Kim k-ε, and Lam-Bremhorst k-ε. Numerical analysis of the steam flow was carried out assuming that the flow at the inlet section of the heat exchanger were divided into three parts. The angle of steam flow at inlet section was determined individually in order to obtain the best configuration of entry vanes and hence improve the heat exchanger construction. Results of numerical studies were verified experimentally for a real heat exchanger. The modification of the inlet flow direction according to theoretical considerations causes the increase of thermal power of a heat exchanger of about 14%.
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Abstract

Aim: The aim of this study was to analyze the effect of bovine follicular fluid on the survival, morphology and kinetic parameters of bovine thawed spermatozoa under laboratory conditions. Materials and methods: The semen from 5 bulls of proven fertility was incubated in follicular and physiological fluid for 8 hours. During this time assessment using the CASA system was performed. At the beginning and the end of incubation process evaluation by flow cytometry was conducted. Results: The results of the sperm motility assessment showed a significant decrease in the analyzed parameters both in the follicular and physiological fluid. A significant reduction in all parameters characterizing movement properties in the semen incubated in the follicular fluid was found. In the physiological fluid, a similar trend was demonstrated only for the following proper- ties: VAP, VSL, VCL, ALH, BCF. A significant difference was found for both fluids in: VCL (p=0.026), ALH (p=0.038) and LIN (p<0.001) at the beginning of incubation. The results of the plasma membrane integrity assessment showed a statistically significant increase in the percent- age of dying sperm at the 8th hour of the incubation in the follicular fluid. In the case of semen incubation in physiological fluid, a statistically significant decrease in the percentage of live non-damaged cells was found with a simultaneous increase in the subpopulation of undamaged dead cells. Conclusions: Follicular fluid rapidly accelerates the capacitation process. The results of flow cytometry support the hypothesis concerning the ability of follicular fluid to prolong sperm sur- vival.
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Abstract

The paper presents the results of calculations related to determination of temperature distributions in a steel pipe of a heat exchanger taking into account inner mineral deposits. Calculations have been carried out for silicate-based scale being characterized by a low heat transfer coefficient. Deposits of the lowest values of heat conduction coefficient are particularly impactful on the strength of thermally loaded elements. In the analysis the location of the thermocouple and the imperfection of its installation were taken into account. The paper presents the influence of determination accuracy of the heat flux on the pipe external wall on temperature distribution. The influence of the heat flux disturbance value on the thickness of deposit has also been analyzed.
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Abstract

The suitability of low-cost impedance sensors for microbiological purposes and biofilm growth monitoring was evaluated. The sensors with interdigitated electrodes were fabricated in PCB and LTCC technologies. The electrodes were golden (LTCC) or gold-plated (PCB) to provide surface stability. The sensors were used for monitoring growth and degradation of the reference ATCC 15442 Pseudomonas aeruginosa strain biofilm in invitro setting. During the experiment, the impedance spectra of the sensors were measured and analysed using electrical equivalent circuit (EEC) modelling. Additionally, the process of adhesion and growth of bacteria on a sensor’s surface was assessed by means of the optical and SEM microscopy. EEC and SEM microscopic analysis revealed that the gold layer on copper electrodes was not tight, making the PCB sensors susceptible to corrosion while the LTCC sensors had good surface stability. It turned out that the LTCC sensors are suitable for monitoring pseudomonal biofilm and the PCB sensors are good detectors of ongoing stages of biofilm formation.
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