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Content available remote An improved Müller-Steinhagen and Heck model for two phase pressure drop modeling at high reduced pressures
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Mikielewicz D. , Mikielewicz J.
Journal of Power Technologies
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2022
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tom Vol. 102, nr 3
81--87
EN
Better understanding of two-phase fluid behavior is required to optimize the design models of the components containing a twophase refrigerant. This is important since applications increasingly seek to operate in the region of high reduced pressure values, for instance the vapor generator, which is a key heat exchanger in the Organic Rankine Cycle system and the high temperature heat pump. Implementations are carried out at high evaporation saturation temperatures where the refrigerant transformation to vapor occurs at temperatures higher than 90°C. Analysis of the literature analysis shows there is a gap in knowledge regarding two-phase flow for synthetic refrigerants at high saturation temperatures. Reliable prediction of pressure drop in two-phase flows is an important prerequisite for accurate optimization of thermal systems. The total pressure drop of a fluid derives from the variation of potential and kinetic energy of the fluid and friction on the channel walls or between the phases (60-120oC) and moderate reduced pressures (0.2-0.5). This paper presents a modification to the established Müller-Steinhagen and Heck (1986) model for two phase pressure drop in relation to high values of reduced pressures. Model validation has been done in comparison to reliable experimental data obtained by Charnay et al. (2015) for R245fa at reduced pressures above 0.5. The modification constitutes a significant improvement on the calculations presented in the literature, including by the authors of experimental data.
2
Content available Influence of thermodynamics on the development of technology and science
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Mikielewicz J. , Mikielewicz D.
Archives of Thermodynamics
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2024
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tom Vol. 45, no 2
51--61
EN
Understanding thermodynamics can be challenging due to its dealing with abstract concepts such as entropy and energy transfer. This paper outlines six principles of thermodynamics, whose application necessitates a coherent overarching philosophy. The problems studied often entail complex mathematical equations, relying on a strong foundation in physics and mathematics. Moreover, comprehending thermodynamics requires a shift in thinking, focusing on macroscopic properties of matter rather than microscopic interactions, as in other branches of physics. Thermodynamics also introduces a new philosophy in science – the concept of irreversible phenomena, rooted in the heat flow theory, which is currently being extrapolated to other scientific domains. Notably, this involves extending the concept of work to systems performing various types of work beyond volume change.
3
Content available Development of ORC’s for micro power generation
100%
Mikielewicz J. , Mikielewicz D.
Eco-Energetics : technologies, environment, law and economy
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2018
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tom T. 1
51--72
EN
In the paper, new trends in development of micro power generation of heat and electricity are presented. New type of CHP for domestic usage is developed in the Institute of Fluid-Flow Machinery PAS and methods of its design are presented. The most promising trends in equipment of ORC cycle for this purpose were discussed. Main attention was focused on micro-heat exchangers design based on micro-channels and micro-jets. In our opinion future development of high power heat exchangers will be based on nets micro-heat exchangers.
4
Analiza porównawcza pracy kotła kondensacyjnego i tradycyjnego wyposażonych w mikrosiłownię ORC
100%
Mikielewicz D. , Mikielewicz J.
Technika Chłodnicza i Klimatyzacyjna
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2019
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tom nr 6-7
242--245
5
Analiza obiegów termodynamicznych opartych na acetonie
100%
Mikielewicz J. , Matysko R.
Technika Chłodnicza i Klimatyzacyjna
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2019
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tom nr 6-7
246--250
6
Content available Diffusive-inertial droplet separation model from two-phase flow
80%
Mikielewicz J. , Dolna O. , Kwidziński R.
Archives of Thermodynamics
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2021
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tom Vol. 42, no 3
141--158
EN
This paper concerns analytical considerations on a complex phenomenon which is diffusive-inertial droplet separation from the two-phase vapour-liquid flow which occurs in many devices in the power industry (e.g. heat pumps, steam turbines, organic Rankine cycles, etc.). The new mathematical model is mostly devoted to the analysis of the mechanisms of diffusion and inertia influencing the distance at which a droplet separates from the two-phase flow and falls on a channel wall. The analytical model was validated based on experimental data. The results obtained through the analytical computations stay in a satisfactory agreement with available literature data.
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