Wyniki wyszukiwania - Biblioteka Nauki

1

Experimental study of a two-phase ejector for CO2 transcritical refrigeration system

100%

Haberschill P. , Nehdi E. , Kairouani L. , Elakhdar M. A.

Archives of Thermodynamics

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2021

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tom Vol. 42, no 4

217--246

EN

The geometry and operating parameters have an important influence on the performance of ejectors. The improvement of the refrigeration cycle performance and the design of the ejectors for the compression energy recovery requires a detailed analysis of the internal ejector working characteristics and geometry. To this aim, an experimental investigation of an ejector refrigeration system is conducted to determine the effect of the most important ejector dimensions on ejector working characteristics and system performance. Different dimensions of ejector components are tested. The influence of the ejector’s geometrical parameters on the system performance was analysed. The experiments with respect to the variation of ejector geometry such as the motive nozzle throat diameter, the mixing chamber diameter and the distance between the motive nozzle and diffuser were carried out. There exist optimum design parameters in each test. The experimental results show that the performance (entrainment ratio and a compression ratio of the ejector) increases significantly with the position between the primary nozzle and the mixing chamber. A maximum entrainment ratio of 57.3% and a compression ratio of 1.26 were recorded for the different parameters studied. The results obtained are consistent with experimental results found in the literature.

2

Design and optimisation of exhaust system of light turboprop airplane

88%

Stalewski W.

Journal of KONES

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2016

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tom Vol. 23, No. 2

341--348

EN

Innovative exhaust system for light turboprop airplane has been developed and optimised. Apart from the basic function of removing exhaust from turboprop engine, the system supports cooling of the engine bay. To do this, the system removes hot air from the engine bay, utilising the ejector-pump effect, where the exhaust stream generates under-pressure, sucking the hot air through the ejector slot and removes the air together with the exhaust gases. The design and optimisation of the exhaust system has been conducted based on computational methods of Computer-Aided Design and Optimisation and Computational Fluid Dynamic. Three-dimensional analysis of flow around the airplane (including effect of propeller) and inside the exhaust system was conducted by application of URANS solver ANSYS FLUENT. Using these software the trajectories of exhaust particles, both inside the exhaust ducts and outside the airplane, have been determined. Parametric model of the designed exhaust system has been developed using the in-house software PARADES. As design parameters the diameter, length and direction of exhaust ducts as well as few parameters describing a shape of the ejector, have been established. The optimisation process aimed at designing of the exhaust system, which removes the exhaust gases possibly far away from the airframe, especially during a descent flight of the airplane. Additional objectives were maximisation of the mass flow rate of hot air sucked through the ejector and minimisation of the drag force generated by external part of the exhaust system. The optimised exhaust system should have also fulfilled requirements of permissible total-pressure losses inside the exhaust ducts. The optimised exhaust system has been implemented on the light turboprop airplane and validated during flight tests.

3

Geothermal heat pumps with two-phase condensing ejector

75%

Bergander M.

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tom Vol. 4

1-12

EN

The paper describes the development of a novel vapor compression cycle for refrigeration with regenerative use of the potential energy of two-phase flow expansion, which in traditional systems is lost in expansion valves. The new cycle includes a second step compression by an ejector device, which combines the compression with simultaneous throttling of the liquid. The compressor compresses the vapor to approximately 2/3 of the final pressure and additional compression is provided in an ejector, thus the amount of mechanical energy required by a compressor is reduced and the efficiency is increased. Investigations described here were performed under the funding from the US Department of Energy. The thermodynamic model was developed for R22 refrigerant, showing a possible efficiency improvement of 38% as compared to the traditional vapor compression cycle. The theoretical work was followed by building a 10 kW prototype and practical demonstration of 16% energy savings in the first attempt.

PL

W artykule opisano rozwój systemów chłodniczych wykorzystujących energię potencjalną dwufazowego rozprężanie, która jest tracona w tradycyjnych systemach. Nowy cykl zawiera dodatkowy etap sprężania przy użyciu ejektora, który łączy sprężanie z jednoczesnym dławieniem płynu. Kompresor spręża pary do około 2/3 końcowego ciśnienia, a dodatkowe sprężanie ma miejsce dzięki ejektorowi. Z tego względu całkowita energia dostarczana do kompresora jest zmniejszona i tym samym sprawność jest podniesiona. Prace opisane w artykule były prowadzone dzięki wsparciu Ministerstwa Energii USA. Model termodynamiczny został rozwinięty dla czynnika R22, pokazując możliwe podniesienie sprawności o 38% w porównaniu do tradycyjnego cyklu sprężania. Prace teoretyczne zostały wzbogacone przez wybudowany 10kW prototyp i pokaz rzeczywistej oszczędności 16% energii przy pierwszej próbie.

4

Badania obiegu strumienicowego dla układu klimatyzacji solarnej

75%

Trela M. , Butrymowicz D. , Karwacki J. , Ochrymiuk T. , Śmierciew K.

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tom nr 132

287-296

PL

W referacie zaprezentowano ideę klimatyzacji solarnej opartej na zastosowaniu strumienicowego urządzenia chłodniczego napędzanego ciepłem promieniowania słonecznego. Przedstawiono stanowisko badawcze, wstępne wyniki badań uzyskane dla czynnika R-123 oraz wyniki modelowania numerycznego strumienicy parowej.

EN

The basic principles of solar air-conditioning based on the ejection refrigeration system motivated by solar radiation heat has been presented. The testing rig, preliminary test results obtained with R-123 refrigerant as well as numerical modeling results of vapour ejector have been presented in the paper.

5

Thermodynamic analysis of a new dual evaporator CO2 transcritical refrigeration cycle

75%

Abdellaoui E. Y. , Kairouani L. K.

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6

Zagadnienia produkcji chłodu z niskotemperaturowych źródeł ciepła z zastosowaniem strumienicowych układów chłodniczych

51%

Pawluczuk A. , Butrymowicz D.

Instal

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2016

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tom nr 11

26--32

PL

Przedstawiono podstawowe zagadnienia zastosowania układów chłodniczych strumienicowych w aspekcie wykorzystania niskotemperaturowego ciepła odpadowego jako źródła napędowego. Oceniono efektywność energetyczną tych układów oraz scharakteryzowano stosowane w nich czynniki robocze. Omówiono aspekty aplikacji inżektora dwufazowego w tych układach.

EN

Review on applications of ejection refrigeration systems with usage of low grade heat sources as motive heat was presented. The energy efficiency of these systems was assessed along with short analysis of the potential working fluids. The issues of application of two-phase vapour-liquid injectors in these systems were presented.

7

Trzecia łódź jednopienna z Ostrowa Lednickiego

38%

Radke K.

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tom 16

81-98

EN

In the introduction, this paper refers to two previous actions aimed at extracting dugout boats from the bottom of Lake Lednica (in 1960 and 1982). The main part of the text presents the third action, carried out in 2016 by underwater archaeologists and students from the Department of Underwater Archaeology, Nicolaus Copernicus University. The paper explains the subsequent stages and procedures of investigations. All the difficulties and complications that arose from the circumstances of the deposition, the raw material from which the boat was made and the size of the object are emphasised. As shown by the 1997 study, the boat is made of wood from the lime tree. The boat is now 930 cm in length and 86 cm in width. The bow looks like a slightly oval pyramid; the stern was formed in the shape of a small overhang and could have been about 1 m longer. The dugout has three bulkheads: the first is the same height as the sides, the second one is shorter than the sides by about 6 cm and the third, formed stepwise (?), starts at the same height as the starboard and keeps this height to the crack, after which it is gradually lowered, going down about 5 cm below the port. The average thickness of the starboard is 5.5 cm, while the port is 4.5 cm thick. The thickness of the bottom at the stern break, ranges from 4 cm to 8.5 cm; in other breaks, it reaches as much as 19 cm. The dugout boat is poorly preserved. It has at least nine transverse cracks and one longitudinal crack ending at the first bulkhead. Part of the damage dated certainly back from the period of the destruction of the bridge; however, a thin layer of sediments covering the side or bulkhead wood did not protect the dugout from the anchors of modern fishing boats. The boat was dated using the C14 method (680 ± 120 BP); calibrated, this points to a very wide range of dates, between 980 and 1454. However, a stratigraphic analysis indicates that the boat fell to the bottom sometime between the period the bridge was completed (964) and the last major repair of the bridge captured by dendrochronological analyses (1023). The first stage of the action consisted in the underwater exploration of the bottom deposits with a water-type ejector. This was used for removing the sediments filling the inside of the boat and those within a belt of a small width on the outside of the sides of the dugout, so that they were clearly visible to a height of approx. 10 cm. The boat was filled with a layer consisting of a large number of strongly compacted chips, which produced a few artefacts: 11 potsherds, five bone fragments and a handle of a wooden cup that was preserved in two fragments. After the whole boat had been cleaned, underwater measurements were taken, which enabled the detailed drawing documentation of the dugout in situ. The second stage consisted in cleaning the area outside the boat with 25–30 cm wide and approx. 40 cm-deep trenches running along both sides of the boat and below them. The sides were cleaned gradually, in 2 m long-fragments, to prevent uncontrolled suction of the boat from the bottom and to reduce the possibility of accidental damage. After completing the exploration of each fragment, separated from the others with natural cracks, the released parts were slipped onto a properly prepared tin ‘trough’, surfaced using a buoyancy balloon and transported close to the shore.In the third stage of the campaign, special frames were prepared for each of the nine elements. After the individual parts had been put on the frames in water, they were brought to the surface with them, secured and transported to the Conservation Laboratory in Toruń. After completing all conservation and reconstruction procedures, the dugout boat will be made available to visitors at the Museum of Polish History in Warsaw.