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1
Content available Development of ORC’s for micro power generation
Mikielewicz Jarosław, Mikielewicz Dariusz
Eco-Energetics : technologies, environment, law and economy
|
2018
|
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.
2
Content available Possibilities of heat transfer augmentation in heat exchangers with minichannels for marine applications
Mikielewicz D., Wajs J.
Polish Maritime Research
|
2017
|
S 1
133-140
EN
In the paper, new trends in the development of microchannel heat exchangers are presented. The exchangers developed in this way can be applied in marine industry. Main attention is focused on heat exchanger design with reduced size of passages, namely based on microchannels. In authors’ opinion, future development of high power heat exchangers will be based on networks of micro heat exchangers.
3
Wyznaczanie współczynnika wymiany ciepła metodą Wilsona w kompaktowym mikrostrugowym wymienniku ciepła
Muszyński T., Andrzejczyk R.
Chłodnictwo : organ Naczelnej Organizacji Technicznej
|
2016
|
R. 51, nr 1-2
10--17
PL
Artykuł przedstawia konstrukcję prototypowego, modułowego mikrostrugowego wymiennika ciepła. Przeprowadzone badania cieplno-przepływowe w układzie woda-woda, umożliwiają określenie efektywności wymiany ciepła, charakterystyk cieplno przepływowych, oraz wielkości współczynnika przejmowania ciepła. Przeprowadzone eksperymenty posłużyły do weryfikacji stosowalności istniejących korelacji opisujących wymianę ciepła w obszarze uderzającej mikrostrugi, do projektowania kompaktowych wymienników ciepła.
EN
The work presents the new construction ofmicrojets heat exchanger. Authors introduced their own experimental results. The data were prepared based on water-water flow configuration. Those experiments were used to created hydraulic and heat transfer flow characteristic of heat exchanger as well as calculation of heat transfer coefficients. At the end of work authors were compared their own experimental data base with well-known correlation from open literature to project and optimization microjets heat exchangers.
4
Content available Performance analyses of helical coil heat exchangers. The effect of external coil surface modification on heat exchanger effectiveness
Andrzejczyk R., Muszyński T.
Archives of Thermodynamics
|
2016
|
Vol. 37, no. 4
137--159
EN
The shell and coil heat exchangers are commonly used in heating, ventilation, nuclear industry, process plant, heat recovery and air conditioning systems. This type of recuperators benefits from simple construction, the low value of pressure drops and high heat transfer. In helical coil, centrifugal force is acting on the moving fluid due to the curvature of the tube results in the development. It has been long recognized that the heat transfer in the helical tube is much better than in the straight ones because of the occurrence of secondary flow in planes normal to the main flow nside the helical structure. Helical tubes show good performance in heat transfer enhancement, while the uniform curvature of spiral structure is inconvenient in pipe installation in heat exchangers. Authors have presented their own construction of shell and tube heat exchanger with intensified heat transfer. The purpose of this article is to assess the influence of the surface modification over the performance coefficient and effectiveness. The experiments have been performed for the steady-state heat transfer. Experimental data points were gathered for both laminar and turbulent flow, both for co current- and countercurrent flow arrangement. To find optimal heat transfer intensification on the shell-side authors applied the number of transfer units analysis.
5
Content available Parametric study of fluid flow and heat transfer over louvered fins of air heat pump evaporator
Muszyński T., Kozieł S. M.
Archives of Thermodynamics
|
2016
|
Vol. 37, no. 3
45--62
EN
Two-dimensional numerical investigations of the fluid flow and heat transfer have been carried out for the laminar flow of the louvered fin-plate heat exchanger, designed to work as an air-source heat pump evaporator. The transferred heat and the pressure drop predicted by simulation have been compared with the corresponding experimental data taken from the literature. Two dimensional analyses of the louvered fins with varying geometry have been conducted. Simulations have been performed for different geometries with varying louver pitch, louver angle and different louver blade number. Constant inlet air temperature and varying velocity ranging from 2 to 8 m/s was assumed in the numerical experiments. The air-side performance is evaluated by calculating the temperature and the pressure drop ratio. Efficiency curves are obtained that can be used to select optimum louver geometry for the selected inlet parameters. A total of 363 different cases of various fin geometry for 7 different air velocities were investigated. The maximum heat transfer improvement interpreted in terms of the maximum efficiency has been obtained for the louver angle of 16° and the louver pitch of 1.35 mm. The presented results indicate that varying louver geometry might be a convenient way of enhancing performance of heat exchangers.
6
Content available Vapordynamic thermosyphon – heat transfer two-phase device for wide applications
Vasiliev L., Vasiliev L., Zhuravlyov A., Shapovalov A., Rodin A.
Archives of Thermodynamics
|
2015
|
Vol. 36, no. 4
65--76
EN
Vapordynamic thermosyphon (VDT) is an efficient heat transfer device. The two-phase flow generation and dynamic interaction between the liquid slugs and vapor bubbles in the annular minichannel of the VDT condenser are the main features of such thermosyphon, which allowed to increase its thermodynamic efficiency. VDT can transfer heat in horizontal position over a long distance. The condenser is nearly isothermal with the length of tens of meters. The VDT evaporators may have different forms. Some practical applications of VDT are considered.
7
Content available remote New trends in development of ORC's for micropower generation
Mikielewicz J., Mikielewicz D.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
|
2014
|
nr 145
91--94
EN
In the paper, new trends in development of micropower 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.
8
Content available Zastosowanie korelacji opisujących wymianę ciepła w obszarze uderzających mikrostrug do projektowania kompaktowych wymienników ciepła: cz. 1. Budowa modelowego wymiennika ciepła i jego charakterystyka
Muszyński T., Andrzejczyk R.
Pomiary Automatyka Kontrola
|
2014
|
R. 60, nr 11
1021--1024
PL
W artykule przedstawiono konstrukcję prototypowego, modułowego mikrostrugowego wymiennika ciepła. Przeprowadzone badania cieplno przepływowe w układzie woda-woda, umożliwiają określenie efektywności wymiany ciepła, charakterystyk cieplno przepływowych, oraz wielkości współczynnika przejmowania ciepła. Eksperymenty w dalszej części publikacji posłużą do weryfikacji stosowalności istniejących korelacji opisujących wymianę ciepła w obszarze uderzającej mikrostrugi.
EN
The article presents experimental studies on a compact heat exchanger with heat transfer intensification by means of impinging microjets. The pursuit to provide high performance of heat exchangers is a response to the demand both in economics and in the universal tendency to miniaturization of industrial equipment. This paper presents the design of a prototype, modular microjet heat exchanger. The modular design of the heat exchanger allows to change its geometrical dimensions, as well as changing the heat exchange membrane material. Schematics, view of test section and design of the heat exchanger are shown in Figures 1 to 4. The study of heat transfer in water-water flow, allows to determine the heat transfer efficiency, the characteristics of heat transfer, and the heat transfer coefficient values. Data were collected for the pressure drops in heat exchanger not exceeding 15 kPa, i.e. such as in conventional heat exchangers. Hydraulic characteristics of a model heat exchanger are shown in Figures 5 and 6. Additionally for the two experimental series, comparison of the performance of tested heat exchanger with standard pipe in the pipe heat exchanger has been made, as shown in Figure 9. Conducted experimental research, in the following part of publication will be used to verify the applicability of the existing correlations of heat transfer in microjet impingement area.
9
Content available Experimental and theoretical study of surface cooling using a single microjet
Mikielewicz D., Muszyński T.
Transactions of the Institute of Fluid-Flow Machinery
|
2010
|
nr 122
95-110
EN
The experimental research of heat transfer due to impingement of a single microjet of water and air has been studied on a specially designed rig. Systematic data on radial wall temperature distribution were collected, which enabled development of empirical correlation for heat transfer coefficient applicable both for air and water flows. Two microjet nozzle diameters were studied, i.e. 180 and 260 ěm. The correlation describing the heat transfer coefficient was later used in validation of a model of a single microjet impinging on a flat plate, developed earlier by the authors. Such analytical model of microjet is of a great value in future analysis as it enables to carry out for example sensitivity tests or to appropriately select operational parameters. The presented model is quite general and its further modifications are possible when some of the imposed assumptions are relaxed. More experiments on the structure of a single microjet are needed which will confirm the correlation presented in the paper.
10
Propane pool boiling heat transfer on horizontal tube
Vasiliev L., Zhuravlyov A., Khrolenok V., Novikov M., Rak A., Mazyuk V.
Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika
|
1999
|
Z. 67
339--347
EN
An experimental investigation of propane boiling heat transfer was done on single horizontal smooth tubes and tubes with porous coverings. Three modes of heat transfer were determined on evaporation surfaces with increasing heat flux: free convection, a transitional mode (the average vapor bubble population was negligible) and developed boiling. The existence of the region length depends on saturation pressure, the kind of evaporation surface, and the direction of heat flux change. On heat flux reduction, a strong heat-flux hysteresis phenomenon was observed: the picture regarding changes of heat transfer regimes the same, but boiling extended into the region which was occupied by free convection. In the wide range of saturation pressures and heat fluxes, the intensity of heat transfer on the samples with porous coatings is high than that on the smooth surface samples. The research carried out showed that an application of metal porous covering with electric arc gas-thermal spraying allows one to increase significantly (3-5 times as high in the region of low heat loads, q < 8 kW/m2, and 2.5-3 times in the region of high heat fluxes, q > 8 kW/m2) the heat transfer intensity for propane boiling on horizontal tubes.
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