In order to describe the fluid flow through the porous centre, made of identical spheres, it is necessary to know the pressure, but in fact -the pressure distribution. For the flows in the range that was traditionally called laminar flow (i. e. for Reynolds numbers (Bear, 1988;Duckworth, 1983;Troskolański, 1957) from the range 0,01 to 3) it is virtually impossible with the use of the tools directly available on the market. Therefore, many scientists who explore this problem have concentrated only on the research of the velocity distribution of the medium that penetrates the intended centre (Bear, 1988) or pressure distribution at high hydraulic gradients (Trzaska & Broda, 1991, 2000Trzaska et al., 2005). It may result from the inaccessibility to the measurement methods that provide measurement of very low hydrostatic pressures, such as pressure resulting from the weight of liquid located in the gravitational field (Duckworth, 1983;Troskolański, 1957). The pressure value c. 10 Pa (Troskolański, 1957) can be generated even by 1 mm height difference between the two levels of the free water surface, which in fact constitutes the definition of gauging tools of today measuring the level of the hydrostatic pressure.Authors proposed a method of hydrostatic pressure measurement and devised a gauging tool. Then a series of tests was conducted aiming at establishing what is the influence of various factors, such as temperature, atmospheric pressure, velocity of measurement completion, etc. on the accuracy and method of measurements. A method for considerable reduction of hysteresis that occurs during measurement was also devised.The method of measurement of small hydrostatic difference measurements allows for the accuracy of measurement of up to 0.5 Pa. Measurement results can be improved successfully by one order of magnitude, which for sure would entail necessary temperature stabilization of the tool. It will be more difficult though to compensate the influence of atmospheric pressure on the measurement process.
The growing interest in the exploitation of marine deposits has resulted in the development of research on deposits and technologies for their exploitation. For several years, the authors have been dealing with one of the most important problems in the deep sea mining of mineral deposits, namely transport from great depths. This publication presents theoretical considerations regarding the use of calcium carbide as a source of energy for transport from the seabed. The authors proposed three lines of the course of the decomposition reaction of calcium carbide and then analyzed the possibility of their use. From the obtained results it can be concluded that the maximum depth of use of a simple CaC2 distribution is about 1 km, while using the method proposed by the authors based on the “balance of forces” (using an additional medium) it is possible to apply this method to any depth occurring on Earth.
Knowledge of pressure distribution (or differential pressure ) determines the fluid flow description through the porous medium. In the case of big Reynolds numbers it is not difficult, but for laminar flows (i.e. for Re numbers Bear, 1988;Duckworth, 1983;Troskolański, 1957) from the scope 0.01 to 3) this description is virtually impossible on the basis of the tools available on the market. The previous study focused on the difficulty of measurement in the case of small differences of pressure and suggested a new original method for the measurement. A new unit for the measurement was constructed consisting of two separate measurement containers. Then the measurements were conducted, which necessitated temperature stabilization of the device and compensation of the atmospheric pressure influence on the measurement process.This paper presents the results of the continuation of research concerning the methods and equipment for the measurement of very small pressure differences. The paper includes also the experience gained from the new measurement unit, which was presented in figures 1-5 subsequently presenting the concept of measurement of small values of hydrodynamic pressure with compensation of atmospheric pressure influence fig. 1; illustration presenting the state corresponding to the case of the lack of flow through the tested item fig 2; state corresponding to the fluid flow through the tested item fig. 3; then the description of the measurement of pressure drop on the tested item fig. 4 and the measurement methodology (relations (1) - (20)). Picture of the measurement unit and its components - fig. 5. Furthermore, the authors present an exemplary measurement series and focus on the method of measurement and data processing -tables 1-8 and figures 6-8. Table 4 presents the comparison of the measurement unit used in the previous research and the new one -presented in the paper. It should be noted that the structure has been simplified and the measurement accuracy has increased.Keywords: small values of differential pressure, measurement, filtration, manometers Znajomość rozkładu ciśnienia (lub różnicy ciśnień) determinuje opis przepływu płynu przez ośrodek porowaty. W przypadku dużych liczb Reynoldsa nie nastręcza to większych trudności, lecz dla przepływów laminarnych (tj. dla liczb Re (Bear, 1988;Duckworth, 1983;Troskolański, 1957) z zakresu 0.01 do 3)
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