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Abstract

The heat transfer measurements were conducted during pool boiling of water on surfaces with microchannels. Parallel grooves were made on a copper surface with widths ranging from 0.2 mm to 0.5 mm at intervals of 0.1 mm. The inclination angle of the grooves to the horizontal was set at 30° and 60°, and the depth of the microchannel grooves was 0.3 mm. The achieved heat flux ranged from 25 kW/m>² to 1730 kW/m², and the heat transfer coefficients ranged from 12 kW/(m²K) to 475 kW/(m²K). The influence of geometric parameters such as width, inclination angle of the microchannel, surface ex-tension, and Bond number on heat exchange efficiency was examined. A nearly sixfold increase in α (heat transfer coeffi-cient) and a twofold increase in critical heat flux were observed compared to a smooth surface.
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Authors and Affiliations

Robert Mikołaj Kaniowski
1

  1. Kielce University of Technology, Faculty of Mechatronics and Mechanical Engineering, al. Tysiąclecia Państwa Polskiego 7, 25-314 Kielce, Poland
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Abstract

The paper presents the design of a heat exchanger immersed in a water-ice reservoir and the determination of its heat capacity as a lower heat source for the heat pump. This is an innovative solution, the first project on this scale in Poland. Heat absorption from the water-ice tank took place in three stages: from water at a temperature range of 20oC to 0oC, from the water-ice phase change at 0oC, and from ice at a temperature range of 0oC to 10oC. The CFD (Computational Fluid Dynamics) analysis of a heat exchanger performance was performed. It required simulation of water natural convection, water-ice phase change, and heat transfer from the ground. The heat flux absorbed in the designed exchanger was calculated based on the current glycol temperature and the implemented COP (Coefficient of Performance) characteristic of the heat pump. This was done via the user-defined function (UDF) available in Ansys FLUENT. The compiled internal software subroutine was defined based on the DEFINE_ADJUST macro. Moreover, the thermal resistance of ice forming on the pipes was included. The numerical analysis indicated that 66097 kWh of heat would be absorbed from the reservoir in 500 hours of exploitation. The volume fraction of water at the end of the simulation was equal to 26.7% and the volume fraction of ice was equal to 73.3%. The CFD simulation confirmed the heat capacity value of the water-ice storage tank which fulfilled the design requirements.
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Authors and Affiliations

Piotr Tarnawski
1
ORCID: ORCID

  1. Warsaw University of Technology, Plac Politechniki 1, 00-661 Warsaw, Poland
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Abstract

The present study involves computational investigation of effusion cooling over a flat plate through the different shaped holes. The interaction between the film jet and the mainstream flow creates a counter-rotating vortex pair, resulting jet detachment from the surface and insufficient film cooling coverage over the surface. To enhance the effusion cooling performance, shaped holes are used in place of standard cylindrical holes to reduce the effects of the counter-rotating vortex pair. Two different shaped holes i.e., conical-shaped and fan-shaped holes are used in the investigation and compared to the cylindrical holes. A commercial finite element method package COMSOL Multiphysics 5.5 is used to simulate and analyse the three-dimensional combustor liners of gas turbine. Data is presented for total 10 rows of effusion holes with injection angles 30o at blowing ratios 0.25, 1.0 and 3.2. The shaped holes provide better cooling effectiveness by increasing the lateral spread of coolant over the surface wall. The results show that both the shaped hole geometries can generate additional anti-counter rotating vortex pairs, which contribute to reducing the strength of the counter-rotating vortex pair. The coolant penetration and strong shear zones at the interaction of coolant jet and main stream in shaped holes are greatly reduced in comparison with cylindrical holes. For a low blowing ratio of 0.25, the conical-shaped holes exhibited adiabatic effectiveness that was 25% and 19% greater than the cylindrical and trapezoidal-shaped holes respectively. On the other hand, fan-shaped holes provide enhanced adiabatic effectiveness at increased blowing ratios. At higher value of blowing ratio 3.2, the adiabatic effectiveness increased by 13% compared to cylindrical holes and 4% compared to conical-shaped holes. In addition, velocity profiles and two-dimensional streamlines have been examined in order to study the flow be-havior on the surface.
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Authors and Affiliations

Yellu Kumar
1
Adnan Qayoum
1
Shahid Saleem
1

  1. Mechanical Engineering Department, National Institute of Technology Srinagar, J&K, 190006, India
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Abstract

Measurements of thermal diffusivity, heat capacity and thermal expansion of hot work tool steel 32CrMoV12-28 have been carried out in the temperature range from room temperature (RT) to 1000℃. 32CrMoV12-28 steel has been tested for military applications as steel for gun barrels. The thermophysical properties of this steel can be used as input data for numerical simulations of heat transfer in gun barrels. Both the LFA 427 laser flash apparatus in the RT1000℃ temperature range and the LFA 467 light flash apparatus in the RT500℃ temperature range were used for thermal diffusivity tests. Specific heat capacity was investigated in the range RT1000℃. The specific heat was determined by two methods, i.e. the classical method, the so-called continuous-scanning method and the stepwise-scanning method according to EN ISO 11357-4. The paper compares both methods and assesses their suitability for testing the specific heat capacity of barrel steels. Thermal expansion was investigated in the range RT1000℃. Inconel 600 was selected as the reference material during the thermal diffusivity test using LFA 467. Light microscopy (LM), scanning electron microscopy (SEM), and Vickers microhardness measurements were performed to detect changes in the microstructure before and after thermo-physical measurements. We compared the results of measurements of the thermophysical properties of 32CrMoV12-28 steel with the results of our tests for other barrel steels with medium carbon content, i.e. X37CrMoV5-1 (1.2343), 38HMJ (1.8509) and 30HN2MFA. The comparison was made in terms of shifting the effect of material shrinkage towards higher temperatures.
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Authors and Affiliations

Piotr Koniorczyk
1
Mateusz Zieliński
1
Judyta Sienkiewicz
1
Janusz Zmywaczyk
1

  1. Military University of Technology, Faculty of Mechatronics, Armament and Aerospace, gen. Sylwestra Kaliskiego 2, 00-908 Warsaw, Poland
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Abstract

The internal diameter of a tube in a ‘church window’ condenser was estimated using an entropy generation minimization approach. The adopted model took into account the entropy generation due to heat transfer and flow resistance from the cooling-water side. Calculations were performed considering two equations for the flow resistance coefficient for four different roughness values of a condenser tube. Following the analysis, the internal diameter of the tube was obtained in the range of 17.5 mm to 20 mm (the current internal diameter of the condenser tube is 22 mm). The calculated diameter depends on and is positively related to the roughness assumed in the model.
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Authors and Affiliations

Artur Rusowicz
Rafał Laskowski
Andrzej Grzebielec
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Abstract

The paper reviews selected methods of agricultural biogas production and characterizes their technical and technological aspects. The conditions of the anaerobic fermentation process in the reactor with adhesive skeleton bed were analyzed. The required technological criteria for the production of biogas from a substrate in the form of pig slurry were indicated. As part of experimental studies, evaluation of the biogas replacement resistance coefficient and the permeability coefficient as a function of the Reynolds number were made. The method of numerical simulation with the use of a tool containing computational fluid dynamics codes was applied. Using the turbulent flow model – the RANS model with the enhanced wall treatment option, a numerical simulation was carried out, allowing for a detailed analysis of hydrodynamic phenomena in the adhesive skeleton bed. The paper presents the experimental and numerical results that allow to understand the fluid flow characteristics for the intensification of agricultural biogas production.
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Bibliography

[1] Grzegorzewicz J., Gruszecki Z., Sciezynski H., Cieslak R., Smaga M., Jurkowski A., Matyja K., Papuga W.: Bubble Reactor. Patent Office of the Republic of Poland. Patent Application P.174663, 1994 (in Polish).
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[6] Oniszk-Popławska A., Matyka M.: Final report on the field research. “Comprehensive assessment of the conditions for biogas production in the Lubelskie Voivodeship”. Regional Economic Change Management System, 2012 (in Polish).
[7] Jedrczak A.: Biological waste treatment. Przeglad Komunalny (2001), 6, 89–92 (in Polish). [8] Wałowski G.: Developing technique anaerobic digestion in the contex of renewable energy sources. In: Proc. 26th Eur. Biomass Conf., Copenhagen, 14-17 May 2018, 798–808
[9] Kowalczyk-Jusko A.: Biogas plants an opportunity for agriculture and the environment. Fundacja na rzecz Rozwoju Polskiego Rolnictwa, 2013 (in Polish).
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[11] den Boer E., Szpadt R.: Biogas plants as an opportunity for agriculture and the environment]. In: Proc. Conf. on 24 Oct. 2013, Dolnoslaski Osrodek Doradztwa Rolniczego we Wrocławiu (in Polish).
[12] Karłowski J., Kliber A., Myczko A., Golimowska R., Myczko R.: Agronomy in the sustainable development of modern agriculture]. In: Proc. 4th Sci. Conf. of the Polish Agronomic Society, Warszawa, 5-7 Sept. 2011 (in Polish).
[13] Myczko A., Myczko R., Kołodziejczyk T., Golimowska R., Lenarczyk J., Janas Z., Kliber A., Karłowski J., Dolska M.: Construction and Operation of Agricultural Biogas Plants. Wyd. ITP, Warszawa Poznan 2011.
[14] Kołodziejczyk T., Myczko R., Myczko A.: Use of residual non-food cellulosic material for biogas production. Ciepłownictwo, Ogrzewanictwo, Wentylacja 42(2011), 9, 360–363. (in Polish).
[15] Wałowski G.: Interpretation of the mechanism of biogas flow through an adhesive bed in analogy to gas-permeability for a structural model of a porous material. Int. J. Curr. Res. 10(2018), 12, 76225–76228.
[16] Wałowski G.: Multi-phase flow assessment for the fermentation process in monosubstrate reactor with skeleton bed. J. Water Land Dev. 42(2019), 7-9, 150–156.
[17] Myczko A., Kliber A., Tupalski L.: The latest achievements in the field of renewable energy sources along with the presentation of barriers to the implementation of research results into business practice. In: The Latest Developments in the Field of RES, Including the Presentation of Barriers to the Implementation of Research Results in Business Practice and Suggestions for their Solutions (B. Mickiewicz, Ed.), Koszalin 2012 (in Polish).
[18] Wałowski G., Borek, K. Romaniuk W., Wardal W.J., Borusewicz A.: Modern Systems of Obtaining Energy – Biogas. Wydawnictwo Wyzszej Szkoły Agrobiznesu w Łomzy, Łomza 2019 (in Polish).
[19] Strzelecki T., Kostecki S., Zak S.: Modelling of flows through porous media. Dolnoslaskie Wydawnictwo Edukacyjne, Wrocław, 2008. (in Polish).
[20] https://www.ansys.com/products/fluids/ansys-fluent (accessed 15 Apr. 2018).
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Authors and Affiliations

Grzegorz Wałowski
1
ORCID: ORCID

  1. Institute of Technology and Life Sciences, Falenty, Department of Renewable Energy, Poznań Branch, ul. Biskupińska 67, 60-463 Poznań, Poland
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Abstract

Given its high efficiency, low emissions and multiple fuelling options, the solid oxide fuel cells (SOFC) offer a promising alternative for stationary power generators, especially while engaged in micro-combined heat and power (μ-CHP) units. Despite the fact that the fuel cells are a key component in such power systems, other auxiliaries of the system can play a critical role and therefore require a significant attention. Since SOFC uses a ceramic material as an electrolyte, the high operating temperature (typically of the order of 700–900°C) is required to achieve sufficient performance. For that reason both the fuel and the oxidant have to be preheated before entering the SOFC stack. Hot gases exiting the fuel cell stack transport substantial amount of energy which has to be partly recovered for preheating streams entering the stack and for heating purposes. Effective thermal integration of the μ-CHP can be achieved only when proper technical measures are used. The ability of efficiently preheating the streams of oxidant and fuel relies on heat exchangers which are present in all possible configurations of power system with solid oxide fuel cells. In this work a compact, fin plate heat exchanger operating in the high temperature regime was under consideration. Dynamic model was proposed for investigation of its performance under the transitional states of the fuel cell system. Heat exchanger was simulated using commercial modeling software. The model includes key geometrical and functional parameters. The working conditions of the power unit with SOFC vary due to the several factors, such as load changes, heating and cooling procedures of the stack and others. These issues affect parameters of the incoming streams to the heat exchanger. The mathematical model of the heat exchanger is based on a set of equations which are simultaneously solved in the iterative process. It enables to define conditions in the outlets of both the hot and the cold sides. Additionally, model can be used for simulating the stand-alone heat exchanger or for investigations of a semiadiabatic unit located in the hotbox of the μ-CHP unit.
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Authors and Affiliations

Konrad Motyliński
Jakub Kupecki
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Abstract

In the paper the methodology of furnace exit gas temperature calculations by using well known normative standard method CKTI is presented. There are shown changes in methodology approach for three editions of it and in additional developments. Furnace exit gas temperature for two stoker grate boilers is calculated. By using described methods, it was possible to determine their effectiveness by comparing with measurements. Knowledge of the furnace exit gas temperature allows to define the division into irradiated and convection surfaces, which has an impact on the design features of the boiler as well as its dimensions and weight.
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Bibliography

[1] Kashnikov S.P., Tsygankov V.N.: Calculation of Boiler Units. In Examples and Problems. Gosenergoizdat, Moscow 1951 (in Russian).
[2] Kuznetsov N.V., Mitor V.V., Dubovsky I.E., Karasina E.S. (Eds.): Thermal Calculation of Boiler Units. Normative Method (2nd Edn.). Energia, Moscow 1973 (in Russian).
[3] Blokh A.G.: Heat Transfer in Steam Boiler Furnaces. Energoatomizdat, Moscow 1984 (in Russian).
[4] Blokh A.G.: Heat Transfer in Steam Boiler Furnaces, Springer Verlag, 1988.
[5] Kagan G.M.: Thermal Calculation of Boilers. Normative Method (3rd Edn.). NPO CKTI, Sankt-Peterburg 1998 (in Russian).
[6] Ye Weijie, Cheng Leming (Eds.): Thermal Calculation Method for Grate-Firing and Fluidized Bed Industrial Boiler, General Methods of Calculation and Design for Industrial Boiler. Standards Press, Bejing 2003 (in Chinese).
[7] Zhang Y.: Theory and Calculation of Heat Transfer in Furnaces. Elsevier, 2016.
[8] Kamenetskii B.Ya.: Applicability of the standard method for calculating heat transfer in furnaces with stokers. Therm. Eng. 53(2006), 2, 138–142.
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[10] EN 12952-15. Water tube boilers and auxiliary installations – Part 15: Acceptance tests.
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[12] EN ISO 14001:2015. Environmental management systems. Requirements with guidance for use.
[13] PN-N-18001:2004. Occupational health and safety management systems – Requirements
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Authors and Affiliations

Łukasz Rutkowski
1
Ireneusz Szczygieł
2

  1. Boilers Manufacturer SEFAKO S.A., Przemysłowa 9, 28-340 Sedziszów, Poland
  2. Silesian University of Technology Institute of Thermal Technology, Konarskiego 22, 44-100 Gliwice, Poland
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Abstract

Distribution of the exhaust gas temperature within the furnace of a grate boiler greatly depends on its operating parameters such as output. It has a considerably different character than temperature distributions in other types of boilers (with pulverised or fluidised bed), as it varies considerably across the chamber. Results presented in this paper have been obtained through research of a grate-fired hot water boiler with a nominal rating of some 30 MW. Measurements have been taken by introducing temperature sensors into prearranged openings placed in the boiler side walls. Investigation has been carried out for different output levels. Tests involved thermocouples in ceramic coating and aspirated thermocouples. The latter were used to eliminate influence of radiative heat transfer on measured results. Values obtained with both methods have been cross-checked.
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Authors and Affiliations

Piotr Krawczyk
Krzysztof Badyda
Jacek Szczygieł
Szczepan Młynarz
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Abstract

In this paper, the thermodynamic investigation on the use of geothermal water (130°C as maximum) for power generation through a basic Rankine has been presented together with obtained main results. Six typical organic working fluids (i.e., R245fa, R141b, R290, R600, R152a, and 134a) were studied with modifying the input pressure and temperature to the turbine. The results show that there are no significant changes taking place in the efficiency for these working fluids with overheating the inlet fluid to the turbine, i.e., efficiency is a weak function of temperature. However, with the increasing of pressure ratio in the turbine, the efficiency rises more sharply. The technical viability is shown of implementing this type of process for recovering low temperature heat resource.
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Authors and Affiliations

Yan-Na Liu
Song Xiao
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Abstract

The paper presents a literature review on the topic of vapour power plants working according to the two-phase thermodynamic cycle with supercritical parameters. The main attention was focused on a review of articles and papers on the vapour power plants working using organic circulation fluids powered with low- and medium-temperature heat sources. Power plants with water-steam cycle supplied with a high-temperature sources have also been shown, however, it has been done mainly to show fundamental differences in the efficiency of the power plant and applications of organic and water-steam cycles. Based on a review of available literature references a comparative analysis of the parameters generated by power plants was conducted, depending on the working fluid used, the type and parameters of the heat source, with particular attention to the needs of power plant internal load.
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Authors and Affiliations

Szymon Mocarski
Aleksandra Borsukiewicz-Gozdur
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Abstract

This paper concerns analytical considerations on a complex phenomenon which is diffusive-inertial droplet separation from the twophase 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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Bibliography

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Authors and Affiliations

Jarosław Mikielewicz
1
Oktawia Dolna
1
Roman Kwidziński
1

  1. Institute of Fluid Flow Machinery, Polish Academy of Sciences, Fiszera 14, 80-231 Gdansk, Poland
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Abstract

In the present study, energy and exergy analysis has been evaluated for roughened solar air heater (SAH) using arc shaped wire ribs. To achieve this aim, two different types of flow arrangement have been considered. These arrangements are: apex upstream flow and apex downstream flo. In addition to this, a smooth duct SAH has been used for comparative study. The experiments were performed using the mass flow rate of 0.007– 0.022 kg/s on outdoor condition at Jamshedpur city of India. The absorber plate roughness geometry has been designed with relative roughness height 0.0395, rib size 2.5 mm, relative roughness pitch 10 and arc angle 60 . The energetic and exergetic performances have been examined on the basis of the first and second law of thermodynamics. According to the results, there is observed to be the maximum thermal efficiency and exergy efficiency as 73.2% and 2.64%, respectively, for apex upstream flow SAH at 0.022 kg/s, while, at same mass flow rate the maximum thermal efficiency and exergy efficiency is obtained as 69.4% and 1.89%, respectively, for apex downstream flow SAH. In addition to this, results reported that the maximum outlet temperature and temperature difference observed at lower mass flow rate. Also examined the outlet air temperature of SAH with various mass flow rates is very important for both analysis.
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Bibliography

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Authors and Affiliations

Harish Kumar Ghritlahre
1

  1. Department of Energy and Environmental Engineering, Chhattisgarh Swami Vivekanand Technical University, Bhilai, Chhattisgarh, 491107, India
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Abstract

This work presents two-dimensional numerical investigations of fast pyrolysis of red oak in a free fall reactor. The Euler–Lagrange approach of multiphase flow theory was proposed in order to describe the behaviour of solid particles in the gaseous domain. The main goal of this study was to examine the impact of the flow rate of inert gas on the pyrolysis process. Calculation domain of the reactor was made according to data found in the literature review. Volume flow rates were 3, 9, 18, and 25 l/min, respectively. Nitrogen was selected as an inert gas. Biomass pyrolysis was conducted at 550 deg C with a constant mass flow rate of biomass particles equal to 1 kg/h. A parallel multistage reaction mechanism was applied for the thermal conversion of red oak particles. The composition of biomass was represented by three main pseudo-components: cellulose, hemicellulose and lignin. The received products of pyrolysis were designated into three groups: solid residue (char and unreacted particles), primary tars and noncondensable gases. In this work the impact of the volume flow rate on the heating time of solid particle, temperature distribution, yields and char mass fraction has been analysed. The numerical solutions were verified according to the literature results when the flow of nitrogen was set at 18 l/min. The calculated results showed that biomass particles could be heated for longer when the flow rate of nitrogen was reduced, allowing for a greater concentration of volatile matter.
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Authors and Affiliations

Artur Bieniek
1
Wojciech Jerzak
1
Aneta Magdziarz
1

  1. AGH University of Science and Technology, Mickiewicza 30, 30-059, Krakow, Poland
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Abstract

For conventional diesel engines, two of the most widely used global correlations are due to Woschni and Hohenberg. Besides, the modern diesel engines used a new heat transfer coefficient correlation was proposed by Finol and Robinson. In Vietnam, improving engine power density is a trend of improving non-turbocharged base engines by using a supercharging system with exhaust gas energy recovery. Increasing engine power by the turbocharger is limited for two reasons: mechanical stress and thermal stress of the components surrounding the combustion chamber. In general, the heat transfer coefficient has a major effect on heat transfer rate, especially during the combustion process. So, the purpose of this study is to compare the cylinder distribution results from the simulation using the equations of Woschni and Hohenberg and compare to the experiment results when converting an old heavy-duty engine into a turbocharged engine. Results show that the cylinder distribution using Hohenberg’s correlation has a good agreement with the experiment results, especially in the case of a turbocharged engine.
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Authors and Affiliations

Kien Nguyen Trung
1 2

  1. Phenikaa University, Faculty of Vehicle and Energy Engineering, Yen Nghia Ward, Ha-Dong District, Hanoi 12116, Vietnam
  2. Phenikaa Research and Technology Institute, A&A Green Phoenix Group JSC, 167 Hoang Ngan, Trung Hoa, Cau Giay, Hanoi 11313, Vietnam
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Abstract

The conversion of a waste heat energy to electricity is now becoming one of the key points to improve the energy efficiency in a process engineering. However, large losses of a low-temperature thermal energy are also present in power engineering. One of such sources of waste heat in power plants are exhaust gases at the outlet of boilers. Through usage of a waste heat regeneration system it is possible to attain a heat rate of approximately 200 MWth, under about 90°C, for a supercritical power block of 900 MWelfuelled by a lignite. In the article, we propose to use the waste heat to improve thermal efficiency of the Szewalski binary vapour cycle. The Szewalski binary vapour cycle provides steam as the working fluid in a high temperature part of the cycle, while another fluid – organic working fluid – as the working substance substituting conventional steam over the temperature range represented by the low pressure steam expansion. In order to define in detail the efficiency of energy conversion at various stages of the proposed cycle the exergy analysis was performed. The steam cycle for reference conditions, the Szewalski binary vapour cycle as well as the Szewalski hierarchic vapour cycle cooperating with a system of waste heat recovery have been comprised.
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Authors and Affiliations

Paweł Ziółkowski
Janusz Badur
Tomasz Kowalczyk
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Abstract

The paper presents formulas which can be used to determine steam condensation pressure in a power plant condenser in off-design conditions. The mathematical model provided in the paper makes it possible to calculate the performance of the condenser in terms of condensing steam pressure, cooling water temperature at the condenser outlet, and condenser effectiveness under variable load conditions as a function of three input properties: the temperature and the mass flow rate of cooling water at the condenser inlet and the mass flow rate of steam. The mathematical model takes into account values of properties occurring in reference conditions but it contains no constant coefficients which would have to be established based on data from technical specifications of a condenser or measurement data. Since there are no such constant coefficients, the model of the steam condenser proposed in the paper is universally applicable. The proposed equations were checked against warranty measurements made in the condenser and measurement data gathered during the operation of a 200 MW steam power unit. Based on the analysis, a conclusion may be drawn that the proposed means of determining pressure in a condenser in off-design conditions reflects the condenser performance with sufficient accuracy. This model can be used in optimization and diagnostic analyses of the performance of a power generation unit.
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Authors and Affiliations

Rafał Laskowski
1
Adam Smyk
1
Adam Ruciński
1
Jacek Szymczyk
1

  1. Institute of Heat Engineering, Faculty of Power and Aeronautical Engineering, Warsaw University of Technology, Nowowiejska 21/25, 00-665 Warsaw, Poland
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Abstract

One of the most energy-intensive activities for a vehicle is space air conditioning, for either cooling or heating. Considerable energy savings can be achieved if this can be decoupled from the use of fuel or electricity. This study analyzes the opportunities and effectiveness of deploying the concept of passive cooling through the atmospheric window (i.e. the 8– 14 nm wavelength range where the atmosphere is transparent for thermal radiation) for vehicle temperature control. Recent work at our institute has resulted in a skylight (roof window) design for passive cooling of building space. This should be applicable to vehicles as well, using the same materials and design concept. An overall cooling effect is obtained if outgoing (long wavelength greater than 4 nm) thermal radiation is stronger than the incoming (short wavelength less than 4 nm) thermal radiation. Of particular interest is to quantify the passive cooling of a vehicle parked under direct/indirect sunlight equipped with a small skylight, designed based on earlier designs for buildings. The work involved simulations using commercial computational fluid dynamics software implementing (where possible) wavelengthdependency of thermal radiation properties of materials involved. The findings show that by the use of passive cooling, a temperature difference of up to 7–8 K is obtained with an internal gas flow rate of 0.7 cm/s inside the skylight. A passive cooling effect of almost 27 W/m2 is attainable for summer season in Finland. Comparison of results from Ansys Fluent and COMSOL models shows differences up to about 10 W/m2 in the estimations.
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Authors and Affiliations

Umara Khan
1
Ron Zevenhoven
1

  1. Abo Akademi University, Process and Systems Engineering Laboratory, Henrikinkatu 2, 20500 Turku, Finland
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Abstract

This work aims to determine and compare heat generation and propagation of densely packed gold nanoparticles (Au NPs) induced by a resonant laser beam (532 nm) according to the Mie theory. The heat flux propagation is transferred into the materials, which here are: silica glass; soda-lime-silica glass; borosilicate glass; polymethyl methacrylate (PMMA); polycarbonate (PC); and polydimetylosiloxane (PDMS). This analysis aims to select the optimum material serving as a base for using photo-thermoablation. On the other hand, research focused only on Newtonian heat transfer in gold, not on non-Fourier ones, like the Cattaneo approach. As a simulation tool, a computational fluid dynamics code with the second-order upwind algorithm is selected. Results reveal a near-Gaussian and Gaussian temperature distribution profile during the heating and cooling processes, respectively. Dependence between the maximum temperature after irradiation and the glass thermal conductivity is observed confirming the Fourier law. Due to the maximum heating area, the borosilicate or soda-lime glass, which serves as a base, shall represent an excellent candidate for future experiments.
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Authors and Affiliations

Piotr Radomski
1
Paweł Ziółkowski
1
Luciano de Sio
2
Dariusz Mikielewicz
1

  1. Gdansk University of Technology, Faculty of Mechanical Engineering and Shipbuilding, Energy Institute, Narutowicza 11/12, 80-233 Gdansk, Poland
  2. Sapienza University of Rome, Department of Medico-Surgical Sciencesand Biotechnologies, Center for Biophotonics, Piazzale Aldo Moro 5,00185 Roma, RM, Italy
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Abstract

Adsorption refrigeration systems are able to work with heat sources of temperature starting with 50°C. The aim of the article is to determine whether in terms of technical and economic issues adsorption refrigeration equipment can work as elements that produce cold using hot water from the district heating network. For this purpose, examined was the work of the adsorption air conditioning equipment cooperating with drycooler, and the opportunities offered by the district heating network in Warsaw during the summer. It turns out that the efficiency of the adsorption device from the economic perspective is not sufficient for production of cold even during the transitional period. The main problem is not the low temperature of the water supply, but the large difference between the coefficients of performance, COPs, of adsorption device and a traditional compressor air conditioning unit. When outside air temperature is 25°C, the COP of the compressor type reaches a value of 4.49, whereas that of the adsorption device in the same conditions is 0.14. The ratio of the COPs is 32. At the same time ratio between the price of 1 kWh of electric power and 1 kWh of heat is only 2.85. Adsorption refrigeration equipment to be able to compete with compressor devices, should feature COPads efficiency to be greater than 1.52. At such a low driving temperature and even changing the drycooler into the evaporative cooler it is not currently possible to achieve.
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Authors and Affiliations

Artur Rusowicz
Andrzej Grzebielec
Maciej Jaworski
Rafał Laskowski
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Abstract

The paper deals with the wet steam flow in a steam turbine operating in a nuclear power plant. Using a pneumatic and an optical probe, the static pressure, steam velocity, steam wetness and the fine water droplets diameter spectra were measured before and beyond the last turbine low-pressure stage. The results of the experiment serve to understand better the wet steam flow and map its liquid phase in this area. The wet steam data is also used to modify the condensation model used in computational fluid dynamics simulations. The condensation model, i.e. the nucleation rate and the growth rate of the droplets, is adjusted so that results of the numerical simulations are in a good agreement with the experimental results. A 3D computational fluid dynamics simulations was performed for the lowpressure part of the turbine considering non-equilibrium steam condensation. In the post-processing of the of the numerical calculation result, the thermodynamic wetness loss was evaluated and analysed. Loss analysis was performed for the turbine outputs of 600, 800, and 1100 MW, respectively.
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Bibliography

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Authors and Affiliations

Gukchol Jun
1 2
Michal Kolovratník
2
Michal Hoznedl
1

  1. Czech Technical University in Prague, Technická 4, 160 00, Prague, Czech Republic
  2. Doosan Škoda Power s.r.o., Tylova 1/57, 301 28, Pilsen, Czech Republic
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Abstract

The experimental research of environmentally friendly refrigerant HFE-7100 condensation in pipe minichannels was conducted. During the investigations of HFE-7100 condensation in a minichannel with internal diameter 2 mm together with visualization of flow patterns was made. Visualization results were compared with existing flow structure maps. The identification of the range of flow patterns occurrence during the condensation process of low-pressure refrigerant HFE-7100 was made. The tests were performed throughout the whole range of condensation process.
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Authors and Affiliations

Tadeusz Bohdal
Małgorzata Sikora
Katarzyna Widomska
Andrii M. Radchenko
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Abstract

An evaluation method is developed for single blow experiments with liquids on heat exchangers. The method is based on the unity Mach number dispersion model. The evaluation of one experiment yields merely one equation for the two unknowns, the number of transfer units and the dispersive Peclet number. Calculations on an example confirm that one single blow test alone cannot provide reliable values of the unknowns. A second test with a liquid of differing heat capacity is required, or a tracer experiment for the measurement of the Peclet number. A modified method is developed for gases. One experiment yields the effective number of transfer units and approximate values of the two unknowns. The numerical evaluation of calculated experiments demonstrates the applicability of the evaluation methods.
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Authors and Affiliations

Wilfried Roetzel
Chakkrit Na Ranong
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Abstract

A tendency to increase the importance of so-called dispersed generation, based on the local energy sources and the working systems utilizing both the fossil fuels and the renewable energy resources is observed nowadays. Generation of electricity on industrial or domestic scale together with production of heat can be obtained for example through employment of the ORC systems. It is mentioned in the EU directive 2012/27/EU for cogenerative production of heat and electricity. For such systems the crucial points are connected with the heat exchangers, which should be small in size but be able to transfer high heat fluxes. In presented paper the prototype microjet heat exchanger dedicated for heat recovery systems is introduced. Its novel construction is described together with the systematical experimental analysis of heat transfer and flow characteristics. Reported results showed high values of the overall heat transfer coefficient and slight increase in the pressure drop. The results of microjet heat exchanger were compared with the results of commercially available compact plate heat exchanger.
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Authors and Affiliations

Elżbieta Fornalik-Wajs
Dariusz Mikielewicz
Jan Wajs
Michał Bajor

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