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Abstract

This paper studies the influence of different cooling technologies on the power density of a traction machine for heavy-duty distribution transport. A prototype induction machine is built with a housing cooling jacket, potted end-windings, entire winding cooling, and shaft cooling. Electromagnetic finite element and thermal lumped-parameter models are parameterized and verified using test bench measurements. The influence of each thermal resistance along the heat paths is studied and discussed. The results are used for studying different cooling technologies. The results indicate an improvement of the continuous power density up to 108% using shaft cooling and up to 15.6% using entire winding cooling.
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Authors and Affiliations

Benedikt Groschup
1
ORCID: ORCID
Daniel Butterweck
1
Kay Hameyer
1
ORCID: ORCID

  1. Institute of Electrical Machines (IEM), RWTH Aachen University, Schinkelstraße 4, 52062 Aachen, Germany
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Abstract

This paper focuses on the computer cooling capacity using the thermosyphon loop with minichannels and minipump. The one-dimensional separate model of two-phase flow and heat transfer in a closed thermosyphon loop with minichannels and minipump has been used in calculations. The latest correlations for minichannels available in literature have been applied. This model is based on mass, momentum, and energy balances in the evaporator, rising tube, condenser and the falling tube. A numerical analysis of the mass flux and heat transfer coefficient in the steady state has been presented.

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Authors and Affiliations

Jarosław Mikielewicz
Henryk Bieliński
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Abstract

The article concerns computer modelling of processes in cooling systems of internal combustion engines. Modelling objectives and existing commercial programs are presented. It also describes Author’s own method of binding graphs used to describe phenomena in the cooling system of a spark ignition engine. The own model has been verified by tests on the engine dynamometer. An example of using a commercial program for experimental modelling of an installation containing a heat accumulator is presented.

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Authors and Affiliations

Zbigniew Kneba
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Abstract

The article presents a water-cooling system for photovoltaic (PV) modules using a two-axis tracking system that tracks the apparent position of the Sun on the celestial sphere. The cooling system consists of 150 adjustable spray nozzles that cool the bottom layer of PV modules. The refrigerant is water taken from a tank with a capacity of 7 m 3. A water recovery system reduces its consumption with efficiency of approximately 90%. The experimental setup consists of a full-size photovoltaic installation made of 10 modules with an output power of 3.5 kWp combined with a tracking system. The article presents an analysis of the cooling system efficiency in various meteorological conditions. Measurements of energy production were performed in the annual cycle using three different types of photovoltaic installations: stationary, two-axis tracking system and two-axis tracking system combined with the cooling system.
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Authors and Affiliations

Kamil Płachta
1
Janusz Mroczka
1
Mariusz Ostrowski
1
ORCID: ORCID

  1. Wroclaw University of Technology, Faculty of Microsystem Electronics and Photonics, Chair of Electronic and Photonic Metrology, Bolesława Prusa 53/55, 50-317 Wrocław, Poland
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Abstract

Water resources are the main component of natural systems affected by climate change in the Middle East. Due to a lack of water, steam power plants that use wet cooling towers have inevitably reduced their output power. This article investigates the replacement of wet cooling towers in Isfahan Thermal Power Plant (ITPP) with Heller natural dry draft cooling towers. The thermodynamic cycle of ITPP is simulated and the effect of condenser temperature on efficiency and output power of ITPP is evaluated. For various reasons, the possibility of installing the Heller tower without increasing in condenser temperature and without changing the existing components of the power plant was rejected. The results show an increase in the condenser temperature by removing the last row blades of the low-pressure turbine. However, by replacing the cooling tower without removing the blades of the last row of the turbine, the output power and efficiency of the power plant have decreased about 12.4 MW and 1.68 percent, respectively.
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Bibliography

[1] B. Dziegielewski and D. Baumann. Tapping alternatives: The benefits of managing urban water demands. Environment: Science and Policy for Sustainable Development, 34(9):6–41, 2010. doi: 10.1080/00139157.1992.9930929.
[2] D. Marmer. Water conservation equals energy conservation. Energy Engineering, 115(5):48–63, 2018. doi: 10.1080/01998595.2018.12027708.
[3] J.M. Burns, D.C. Burns, and J.S. Burns. Retrofitting cooling towers: estimates required to achieve the next level of CWA 316(b) compliance. In Proceedings of the ASME Power Conference, pages 25–33, 2004. doi: 10.1115/POWER2004-52051.
[4] A. Loew, P. Jaramillo, and H. Zhai. Marginal costs of water savings from cooling system retrofits: a case study for Texas power plants. Environmental Research Letters, 11(10):104004, 2016. doi: 10.1088/1748-9326/11/10/104004.
[5] A.E. Conradie and D.G. Kröger. Performance evaluation of dry-cooling systems for power plant applications. Applied Thermal Engineering, 16(3):219–232, 1996. doi: 10.1016/1359-4311(95)00068-2.
[6] A.E. Conradie, J.D. Buys, and D.G. Kröger. Performance optimization of dry-cooling systems for power plants through SQP methods. Applied Thermal Engineering, 18(1-2):25–45, 1998. doi: 10.1016/S1359-4311(97)00020-3.
[7] J.D. Buys and D.G. Kröger. Dimensioning heat exchangers for existing dry cooling towers. Energy Conversion and Management, 29(1):63–71, 1989. doi: 10.1016/0196-8904(89)90014-9.
[8] Z. Zou, Z. Guan, H. Gurgenci, and Y. Lu. Solar enhanced natural draft dry cooling tower for geothermal power applications. Solar Energy, 86(9):2686–2694, 2012. doi: 10.1016/j.solener.2012.06.003.
[9] S. Bagheri and M. Nikkhoo. Investigation of the optimum location for adding two extra Heller-type cooling towers in Shazand power plant. Proceedings of the 17th IAHR International Conference on Cooling Tower and Heat, pages. 74–83, Australia, 2015.
[10] W. Peng and O.K. Sadaghiani. Presentation of an integrated cooling system for enhancement of cooling capability in Heller cooling tower with thermodynamic analyses and optimization. International Journal of Refrigeration, 131:786–802, 2021. doi: 10.1016/j.ijrefrig.2021.07.016.
[11] M.A. Ardekani, F. Farhani, and M. Mazidi. Effects of cross wind conditions on efficiency of Heller dry cooling tower. Experimental Heat Transfer, 28(4):344–353, 2015. doi: 10.1080/08916152.2014.883449.
[12] A. Jahangiri, A. Borzooee, and E. Armoudli. Thermal performance improvement of the three aligned natural draft dry cooling towers by wind breaking walls and flue gas injection under different crosswind conditions. International Journal of Thermal Sciences, 137:288–298, 2019. doi: 10.1016/j.ijthermalsci.2018.11.028.
[13] A.R. Seifi, O.A. Akbari, A.A. Alrashed, F. Afshari, G.A.S. Shabani, R. Seifi, M. Goodarzi, and F. Pourfattah. Effects of external wind breakers of Heller dry cooling system in power plants. Applied Thermal Engineering, 129: 1124–1134, 2018. doi: 10.1016/j.applthermaleng.2017.10.118.
[14] R.A. Kheneslu, A. Jahangiri, and M. Ameri. Interaction effects of natural draft dry cooling tower (NDDCT) performance and 4E (energy, exergy, economic and environmental) analysis of steam power plant under different climatic conditions. Sustainable Energy Technologies and Assessments, 37:100599, 2020. doi: 10.1016/j.seta.2019.100599.
[15] A. Jahangiri and F. Rahmani. Power production limitations due to the environmental effects on the thermal effectiveness of NDDCT in an operating powerplant. Applied Thermal Engineering, 141:444–455, 2018. doi: 10.1016/j.applthermaleng.2018.05.108.
[16] A.D. Samani. Combined cycle power plant with indirect dry cooling tower forecasting using artificial neural network. Decision Science Letters, 7:131–142, 2018. doi: 10.5267/j.dsl.2017.6.004.
[17] T.L. Bergman, F.P. Incropera, D.P. DeWitt, and A.S. Lavine. Fundamentals of Heat and Mass Transfer. John Wiley & Sons, 2011.
[18] Archive of Isfahan Mohammad Montazeri Power Station. Isfahan, Iran, 1984.
[19] H. Ahmadikia and G. Iravani. Numerical and analytical study of natural dry cooling tower in a steam power plant. Journal of Advanced Materials in Engineering (Esteghlal), 26(1):183–195, 2007. (in Persian).
[20] H.G. Zavaragh, M.A. Ceviz, and M.T.S. Tabar. Analysis of windbreaker combinations on steam power plant natural draft dry cooling towers. Applied Thermal Engineering, 99:550–559, 2016. doi: 10.1016/j.applthermaleng.2016.01.103.
[21] K.F. Reinschmidt and R. Narayanan. The optimum shape of cooling towers. Computers & Structures, 5(5-6):321–325, 1975. doi: 10.1016/0045-7949(75)90039-5.
[22] Isfahan Thermal Power Plant documents, No. C.583 and C.749, Islam Abad Power Plant, Isfahan, Iran, 1988.
[23] I.H. Shames. Mechanics of Fluids. 4th ed. McGraw-Hill, New York, 2003.
[24] C.R.F. Azevedo and A. Sinátora. Erosion-fatigue of steam turbine blades. Engineering Failure Analysis, 16(2):2290–2303, 2009. doi: 10.1016/j.engfailanal.2009.03.007.
[25] H. Kim. Crack evaluation of the fourth stage blade in a low-pressure steam turbine. Engineering Failure Analysis, 18(3):907–913, 2011. doi: 10.1016/j.engfailanal.2010.11.004.
[26] L.K. Bhagi, P. Gupta, and V. Rastogi. Fractographic investigations of the failure of L-1 pressure steam turbine blade. Case Studies in Engineering Failure Analysis, 1(2):72–78, 2013. doi: 10.1016/j.csefa.2013.04.007.
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Authors and Affiliations

Mohamad Hasan Malekmohamadi
1 2
Hossein Ahmadikia
1
ORCID: ORCID
Siavash Golmohamadi
2
Hamed Khodadadi
3

  1. University of Isfahan, Isfahan, Iran
  2. Isfahan Thermal Power Plant, Isfahan, Iran
  3. Department of Electrical Engineering, Khomeinishahr Branch, Islamic Azad University, Isfahan, Iran
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Abstract

In this study, a theoretical model is presented to investigate the performance of a thermoelectric (TE) radiant cooling system combined with photovoltaic (PV) modules as a power supply in a building with an ambient temperature reaching more than 45ºC. The combined system TE/PV performance is studied under different solar radiation by using the hourly analysis program and photovoltaic system software. The thermal and electric characteristics of TE are theoretically investigated under various supplied voltages using the multi-paradigm programming language and numerical computing environment. Also, a theoretical analysis of heat transfer between the TE radiant cooling system and an occupied zone from the side, and the other side between the TE radiant cooling system and duct zone is presented. The maximum power consumption by TE panels and building cooling load of 130 kW is predicted for May and June. The 145 units of PV panels could provide about 50% of the power required by TE panels. The thermal and electric characteristics of TE panels results show the minimum cold surface temperature of 15ºC at a supplied voltage between 6 V and 7 V, and the maximum hot surface temperature of 62ºC at a supplied voltage of 16 V. The surface temperature difference between supplied current and supplied power increases as supplied voltage increases. At a higher supplied voltage of 16 V, the maximum surface temperature difference between supplied current, and supplied power of 150ºC, 3.2 A, and 48 W, respectively. The cooling capacity increases as supplied voltage increases, at a surface temperature difference of –10ºC and supplied voltage of 16 V, the maximum cooling capacity is founded at about 60 W. As supplied voltage decreases the coefficient of performance increases. The maximum coefficient of performance is about 5 at the surface temperature difference of –10ºC and supplied voltage of 8 V.
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Authors and Affiliations

Israa Ali Abdulghafor
1
Mohannad Jabbar Mnati
1

  1. Middle Technical University, Institute of Technology Baghdad, Al-Za’franiya, 10074, Baghdad, Iraq
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Abstract

Optimization plays an important role in scientific and engineering research. This paper presents the effects of using the catenoidal shape to design the structure of a chimney cooling tower. The paper compares some geometrical variations of the catenoid with the reference existing hyperboloidal structure. It also compares internal forces, deformation and stability of the catenoidal structure. The comparison shows some predominance of the catenoid over the popular hyperboloid structure of the shell. The paper attempts to find an optimal shape of the cooling tower in order to reduce the amount of material and labor. The paper utilizes engineering tools and the designing process for chimney cooling towers.
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Authors and Affiliations

Maciej Wiśniowski
1
ORCID: ORCID
Robert Walentyński
1
ORCID: ORCID
Dawid Cornik
1
ORCID: ORCID

  1. Faculty of Civil Engineering, Department of Mechanics and Bridges, ul. Akademicka 5, 44-100 Gliwice, Poland
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Abstract

Heat exhaustion of mining environments can cause a significant threat to human health. The existing cooling strategies for the mine face aim to cool the whole face. However, the necessary cooling space for the face is small, with a considerable amount of energy for cooling being wasted. Necessary cooling space is a space occupied by the workers in the face. This study proposed to build a non-homogeneous thermal environment for cost-effective energy savings in the face. An inlet air cooler was laid out in the intake airway to cool the whole face to some extent, and the tracking air cooler was designed to track the worker who constantly moved to improve the thermal environment. The cooling load and air distribution for this cooling strategy were investigated. In addition, the airflow in the face was solved numerically to estimate the cooling effect. The results revealed that an average energy saving of approximately 35% could be achieved. The thermal environment of the necessary cooling space within at least 10 m was significantly improved. This cooling strategy should be taken into account in mine cooling.
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Bibliography

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[16] S. Wang, L. Jin, Z. Han, Y. Li, S. Ou, N. Gao, Z. Huang, Discharging performance of a forced-circulation ice thermal storage system for a permanent refuge chamber in an underground mine. Appl. Therm. Eng. 110, 703-709 (2017). DOI: https://doi.org/10.1016/j.applthermaleng.2016.08.192
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[18] S. Rahnama, P. Sadeghian, P.V. Nielsen, C. Zhang, S. Sadrizadeh, A. Afshari, Cooling capacity of diffuse ceiling ventilation system and the impact of heat load and diffuse panel distribution. Build. Environ. 185, 107290 (2020). DOI: https://doi.org/10.1016/j.buildenv.2020.107290
[19] H . Shi, Q. Chen, Building energy management decision-making in the real world: A comparative study of HVAC cooling strategies. J. Build. Eng. 33, 101869 (2021). DOI: https://doi.org/10.1016/j.jobe.2020.101869
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[21] T. Ahmad, H.X. Chen, Short and medium-term forecasting of cooling and heating load demand in building environment with data-mining based approaches. Energ. Buildings. 166, 460-76 (2018). DOI : https://doi.org/10.1016/j.enbuild.2018.01.066
[22] P. Guo, C. Chen, Field experimental study on the cooling effect of mine cooling system acquiring cold source from return air. Int. J. Min. Sci. Technol. 23, 453-456 (2013). DOI: https://doi.org/10.1016/j.ijmst.2013.05.008
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[24] G .E. du Plessis, L. Liebenberg, E.H. Mathews, Case study: The effects of a variable flow energy saving strategy on a deep-mine cooling system. Appl. Energ. 102, 700-709 (2013). DOI : https://doi.org/10.1016/j.apenergy.2012.08.024
[25] H .L. Hartman, J.M. Mutmansky, R.V. Ramani, Y. Wang, Mine ventilation and air conditioning, 2012 John Wiley & Sons, California. [26] A.W. Homer, Coal mine safety regulation in China and the USA. J. Contemp. Asia. 39, 4-39 (2009).
[27] A.P. Sasmito, J.C. Kurnia, E. Birgersson, A.S. Mujumdar, Computational evaluation of thermal management strategies in an underground mine. Appl. Therm. Eng. 90, 1144-1150 (2015). DOI: https://doi.org/10.1016/j.applthermaleng.2015.01.062
[28] X. Li, H. Fu, Development of an efficient cooling strategy in the heading face of underground mines. Energies 13 (5), 1116 (2020). DOI: https://doi.org/10.3390/en13051116
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Authors and Affiliations

Xian Li
1
ORCID: ORCID
Yaru Wu
1
ORCID: ORCID
Yunfei Zhang
2
ORCID: ORCID

  1. Linyi University, School of Civil Engineering and Architecture, Linyi 276000, P.R. China
  2. Hohai University, College of Civil and Transportation Engineering, Nanjing 210098, P.R. China
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Abstract

This paper presents the influence of cooling water regulation on power plant net efficiency. It was examined whether, for the non-nominal low-pressure turbine load, it is justified to reduce the cooling water pump load, and how it would affect the unit net efficiency. Calculations for two types of power units were carried out: with condensing and extractioncondensing turbine. The tested condensing power plant consists of three surface condensers. The calculation included four condensers’ connections set up on the cooling water side to check how the cooling water system pressure drop affects the net unit performance. The result has confirmed that implementing serial connection decreases net efficiency when cooling water flow regulation is used, but the mixed connection should be applied when pump load is not controlled. It was proved that the cooling water flow control gives a profit for both units. Net efficiency for combined heat and power plant can be improved by 0.1–0.5 pp, the gain is remarkable below 60% of the low-pressure turbine part load. Flow control implementation in the unit with condensing turbine water control gives a similar profit just below 80% of the turbine load. Next, an influence of the additional limitations of a cooling water system (minimal total pump head, cooling tower) affecting the feasibility of implementing the water control has been considered. Applying a multi-cell forced draft cooling tower does not have a significant impact on results, but when a natural draft cooling tower is used, the flow control range is strongly reduced.
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Bibliography

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[5] Laskowski R.: Wybrane zagadnienia modelowania i optymalizacji skraplaczy energetycznych i wymienników regeneracyjnych. Warszawa: Oficyna Wydawnicza Politechniki Warszawskiej, 2018.
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Authors and Affiliations

Ewa Dobkiewicz-Wieczorek
1

  1. Silesian University of Technology Department of Power Engineering and Turbomachinery, Konarskiego 18, 44-100, Gliwice, Poland
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Abstract

This study investigates mechanical properties of accelerated cooled and self-tempered (AC-ST) H-type S275JR quality steel sections in HEA120 and HEB120 sizes. The cooling process is conducted with a specially manufactured system that sprays a coolant consisting of a water + compressed air mixture on the section surfaces. Cooling times were applied as 10 and 30 seconds using 4 and 12 bar compressed air + water at an average constant pressure of 5 bar and a constant flow rate of 0.08 kg/s. In the HEA120 sections, the highest cooling rate was obtained with 83°C/s in the web region under the cooling time of 30 s and the air pressure cooling condition of 12 bar. At the cooling rate up to 6°C/s, the microstructure is transformed to acicular ferrite and polygonal ferrite phase from Ferrite+Pearlite. But upper bainite phase was formed at a cooling rate of 30°C/s, and a small amount of martensite and lower bainite microstructures were observed at a cooling rate of 60°C/s and above. The hardness in the untreated sections, in the range of 106-120 HB, was increased to 195 HB at a cooling rate of 83 C/s in the web region of the HEA120 section. For a cooling rate of 23°C/s, the maximum compressive residual stresses of –352 MPa are measured in the crotch region of the HEB120. And for a cooling rate of 6°C/s, the maximum tensile residual stresses of 442 MPa were determined in the flange region of the HEA120 section.
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Authors and Affiliations

A. Işıkgül
1
ORCID: ORCID
H. Ahlatci
2
ORCID: ORCID
İ. Esen
3
ORCID: ORCID
Y. Türen
2
ORCID: ORCID
O. Yağız
2
ORCID: ORCID

  1. Karabük Iron Steel Industry Trade and Co. Inc., Research and Development Department, Karabük, Turkey
  2. Karabük University, Department of Metallurgy and Materials Engineering, Karabük, Turkey
  3. Karabük University, Department of Mechanical Engineering, Karabük, Turkey
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Abstract

Financial management in a capital group is very important for its growth and operation. Liquidity risk management can be analyzed regarding their static and dynamic dimensions. The process can also be facilitated by cash management products offered by financial institutions. One of the mechanisms influencing the increase in cash management efficiency of a capital group examined in this article is cash pooling, notably multicurrency cash pooling. This type of product is based frequently on the virtual consolidation. Its essence is the consolidation of cash available on the accounts of individual system participants. Using this solution the capital group can manage surpluses and shortages achieving the “economies of scale” (cost reduction and maximization of interest income). Available one the banking services market solutions offer consolidation in USD, EUR, CHF, GBP. The article presents the definition of cash pooling and the essence of its operation. Based on the literature analysis, the article lists types of cash pooling and benefits associated with it. Following on from the solution described, the article presents a model of multicurrency cash pooling in a capital group, including steps necessary to implement it and proposed technical solutions. The solution is described, can be also successfully applied in capital groups of energy sector. Using multicurrency consolidation is very useful solution in deposits management for transactions concluded in international commodities exchanges.

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Authors and Affiliations

Dawid Ciężki
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Abstract

The most power consuming part in the vapor compression cycle (VCC) is the gas compressor. Heating the refrigerant under constant volume after the compressor increases the condenser pressure, which consequently increases the cooling rate of the VCC. This study examined the influence of heating different refrigerants, i.e. R143a, R22, and R600a on the cooling rate of the VCC. Four experiments have been performed: the first experiment is a normal VCC, i.e. without heating, while in the second, third, and fourth experiments were carried out to raise the temperature of the refrigerant to 50°C, 100°C, and 150°C. It has been found that heating raises the refrigerant pressure in VCC and thereby improves the refrigerant’s mass flow rate resulting in an improvement in the cooling power for the same compressor power. Heating the refrigerant after the mechanical compressor increases the temperature of the condenser as well as the temperature of the evaporator when using refrigerant R134a, which prevents the refrigeration cycle to be used in freezing applications, however using refrigerant R22 or refrigerant R600a promotes the heated VCC to be used in freezing applications. Refrigerant R600a has the lowest operating pressure compared to R134a and R22, which promotes R600a to be used rather than R134a and R22 from a leakage point of view.
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Authors and Affiliations

Mohamed Salama Abd-Elhady
1
Emmanoueil Bishara Melad
2
Mohamed Abd-Elhalim
3
Seif Alnasr Ahmed
1

  1. Mechanical Engineering Department, Faculty of Engineering, Beni-Suef University, Sharq El-Nile, New Beni-Suef, 62521 Beni-Suef, Egypt
  2. Faculty of Technology and Education, Beni-Suef University, Sharq El-Nile, New Beni-Suef, 62521 Beni-Suef, Egypt
  3. Faculty of Technology and Education, Suez University, 43527 Suez, Egypt
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Abstract

This paper presents the results of experimental research on heat transfer distribution under the impinging jets at high jet velocity on curved surfaces. The air jets flow out from the common pipe and impinge on a surface which is cooled by them, in this way all together create a model of external cooling system of low pressure gas turbine casing. Preliminary measurement results from the flat plate case were compared with the results from the curved surface case. Surface modification presented in this paper relied on geometry change of flat surface to the form of a ‘bump’. The special system of pivoted mirrors was implemented during the measurements to capture the heat exchange on curved surfaces of the bump. The higher values of mean heat transfer coefficient were observed for all flow cases with a bump in relation to the reference flow case with a flat plate.
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Authors and Affiliations

Marcin Kurowski
1

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

Systematic attempts to maximise the efficiency of gas turbine units are achieved, among other possibilities, by increasing the temperature at the inlet to the expansion section. This requires additional technological solutions in advanced systems for cooling the blade rows with air extracted from the compressor section. This paper introduces a new mathematical model describing the expansion process of the working medium in the turbine stage with air film cooling. The model includes temperature and pressure losses caused by the mixing of cooling air in the path of hot exhaust gases. The improvement of the accuracy of the expansion process mathematical description, compared with the currently used models, is achieved by introducing an additional empirical coefficient estimating the distribution of the cooling air along the profile of the turbine blade. The new approach to determine the theoretical power of a cooled turbine stage is also presented. The model is based on the application of three conservation laws: mass, energy and momentum. The advantage of the proposed approach is the inclusion of variable thermodynamic parameters of the cooling medium. The results were compared with the simplified models used in the literature: separate Hartsel expansion, mainstream pressure, weighted-average pressure and fully reversible. The proposed model for expansion and the determination of theoretical power allows for accurate modelling of the performance of a cooled turbine stage under varying conditions.
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Authors and Affiliations

Paweł Trawiński
1

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

Work on increasing the efficiency of heat exchangers used in car air conditioning systems may lead to a partial change in the construction of refrigeration systems. One of such changes is the use of smaller gas coolers, which directly translates into a reduction in the production costs of the entire system. The article presents the use of computational fluid dynamics methods to simulate the impact of changing the shape of an internal heat exchanger on the cooling efficiency with R744 as the refrigerant. Internal heat exchangers with different geometry of the outer channels were subjected to numerical analysis. The obtained results of calculations show temperature changes in inner and outer channels on the length of the heat exchanger.

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Authors and Affiliations

Jakub Janus
ORCID: ORCID
Przemysław Jan Skotniczy
Maria Richert
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Abstract

Kidney Cooling Jacket (KCJ) preserves the kidney graft, wrapped in the jacket, against the too fast time of temperature rise during the operation of connecting a cooled transplant to the patient’s bloodstream. The efficiency of KCJ depends on the stationarity of the fluid flow and its spatial uniformity. In this paper, the fluid velocity field inside the three different KCJ prototypes has been measured using the 20 MHz ultrasonic Doppler flowmeter. The simplified 2D geometrical model of the prototypes has been presented using COMSOL Multiphysics to simulate the fluid flow assuming the laminar flow model. By comparing the numerical results with experimental data, the simplified 2D model is shown to be accurate enough to predict the flow distribution of the internal fluid velocity field within the KCJ. The discrepancy between the average velocity measured using the 20 MHz Doppler and numerical results was mainly related to the sensitivity of the velocity measurements to a change of the direction of the local fluid flow stream. Flux direction and average velocity were additionally confirmed by using commercial colour Doppler imaging scanner. The current approach showed nearly 90% agreement of the experimental results and numerical simulations. It was important for justifying the use of numerical modelling in designing the baffles distribution (internal walls in the flow space) for obtaining the most spatially uniform field of flow velocity.
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Authors and Affiliations

Barbara Gambin
1
ORCID: ORCID
Ilona Korczak-Cegielska
2
Wojciech Secomski
1
Eleonora Kruglenko
1
Andrzej Nowicki
1

  1. Department of Ultrasound, Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland
  2. Doctoral Studies of Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland
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Abstract

An integration of the electrical machine and the gearbox is attracting particular attention for the design of modern electric and hybrid drive trains, since it saves overall space and subsequently increases the power density. Another benefit of a high level of integration is that it enables a combined application of oils as both cooling fluid for the electrical machine and as lubrication fluid for the transmission system. In this way, the power density of the integrated drive train can be further increased. During the oil cycling, conductive contaminations may be introduced and subsequently have an influence on the function of the insulation system of the electrical machine. In the present work, the influences of the cooling oil and its conductive contaminations, conductive particles as well as their combination with humidity, on the electrical and dielectric properties of the insulation system are studied. The results show that by application of the cooling oil, the partial discharge inception voltage (PDIV) of the winding insulation increases significantly so that an electrical breakdown is prone to happen before a partial discharge (PD) occurs. With increasing particle contamination, the PDIV of the insulation system decreases significantly, while the capacitance increases. Besides, conductive particles and humidity decrease the surface resistance and surface breakdown voltage of the insulation papers significantly. The results indicate that the conductive particle contaminations can play an important role for the electrical degradation of the insulation system.
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Bibliography

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Authors and Affiliations

Liguo Yang
1
ORCID: ORCID
Florian Pauli
1
Shimin Zhang
2
Fabian Hambrecht
1
Kay Hameyer
1
ORCID: ORCID

  1. Institute of Electrical Machines (IEM), RWTH Aachen University, Aachen, Germany
  2. Lubricant Division, TotalEnergies One Tech Solaize, France
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Abstract

Chunky graphite has been recognized for a long time as one of the major problems in production of heavy section nodular cast iron. A great number of studies have been conducted to describe the chunky graphite formation, but a clear understanding of its appearance and a safe mastering of the melt preparation to avoid chunky graphite are not yet available. In the present work the cooling curves were recorded in large cone blocks and standard TA cup. According to measured data from the cone block, melt characteristics and heat transfer coefficient between casting and mould were adjusted in the ProCAST® simulation software. For a near-eutectic nodular cast iron test melt with 0.7 wt. % Ni, relationship between the area of the cone block affected by chunky graphite and simulation software results has been observed, i.e., thermal modulus and time to solidus.

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Authors and Affiliations

B. Bauer
I. Mihalic Pokopec
M. Petrič
P. Mrvar
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Abstract

The study aims to investigate the effect of semisolid structure and strontium (Sr) addition on the wear behavior of hypoeutectic Al-Si alloy. Semisolid hypoeutectic Al-Si alloy was prepared using cooling slope casting with addition of 0 to 0.93 wt.% Sr. Microstructural study was done using an optical microscope. Vicker microhardness and pin on disc tribometer were used for microhardness and wear testing. When compared to conventional casting, the microhardness of the semisolid hypoeutectic Al-Si alloy improved by 9.8%. Sr addition at 0.43 wt.% resulted in a refined eutectic structure with a 17% increase in hardness over conventional casting. The globular structure α-Al formed during semisolid casting reduced porosity, and the addition of Sr refined the eutectic silicon into a fine fibrous structure that is tightly bound with the Al matrix. These are the primary factors that contribute to the high wear resistance in modified-Sr semisolid alloys.
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Authors and Affiliations

N.M. Anas
1
ORCID: ORCID
S.A. Zakaria
1
ORCID: ORCID
A.S. Anasyida
1
ORCID: ORCID
H. Mohamad
1
ORCID: ORCID
B.K. Dhindaw
2
ORCID: ORCID

  1. Universiti Sains Malaysia, Structural Niche Area. School of Mat erials & Mineral Resources Engineering, Engineering Campus, Malaysia 14300 Nibong Tebal, Pulau Pinang
  2. Indian Institute of Technology Kharagpur 721302, India
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Abstract

This paper identifies and describes the parameters of a numerical model generating the microstructure in the integrated heating-remelting-cooling process of steel specimens. The numerical model allows the heating-remelting-cooling process to be simulated comprehensively. The model is based on the Monte Carlo (MC) method and the finite element method (FEM), and works within the entire volume of the steel sample, contrary to previous studies, in which calculations were carried out for selected, relatively small areas. Experimental studies constituting the basis for the identification and description of model parameters such as: probability function, initial number of orientations, number of cells and number of MC steps were carried out using the Gleeble 3800 thermo-mechanical simulator. The use of GPU capabilities improved the performance of the numerical model and significantly reduced the simulation time. Thanks to the significant acceleration of simulation times, it became possible to comprehensively implement a numerical model of the heating-transformation-cooling process in the entire volume of the test sample. The paper is supplemented by results of performance tests of the numerical model and results of simulation tests.
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Authors and Affiliations

Marcin Hojny
Przemysław Marynowski
ORCID: ORCID
Tomasz Dębiński
ORCID: ORCID
D. Cedzidło
1
ORCID: ORCID

  1. AGH University of Science and Technology, Poland
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Abstract

The solubility of Fe in aluminium alloys is known to be a problem in the casting of aluminium alloys. Due to the formation of various intermetallic phases, the mechanical properties decrease. Therefore, it is important to determine the formation mechanisms of such intermetallic. In this work, A360 alloy was used, and Fe additions were made. The alloy was cast into the sand and die moulds that consisted of three different thicknesses. In this way, the effect of the cooling rate was investigated. The holding time was selected to be 5 hours and every hour, a sample was collected from the melt for microstructural analysis. Additionally, the melt quality change was also examined by means of using a reduced pressure test where the bifilm index was measured. It was found that the iron content was increased after 2 hours of holding and the melt quality was decreased. There was a correlation between the duration and bifilm index. The size of Al-Si-Mn-Fe phases was increased in parallel with the bifilm content regardless of the iron content.
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Bibliography

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[2] Ferraro, S. & Timelli, G. (2015). Influence of sludge particles on the tensile properties of die-cast secondary aluminum alloys. Metallurgical and Materials Transactions B. 46(2), 1022-1034. DOI:10.1007/s11663-014-0260-3
[3] Ma, Z., Samuel, A., Samuel, F., Doty, H. & Valtierra, S. (2008). A study of tensile properties in Al–Si–Cu and Al–Si–Mg alloys: Effect of β-iron intermetallics and porosity. Materials Science and Engineering: A. 490(1-2), 36-51. https://doi.org/10.1016/j.msea.2008.01.028
[4] Zahedi, H., Emamy, M., Razaghian, A., Mahta, M., Campbell, J. & Tiryakioğlu, M. (2007). The effect of Fe-rich intermetallics on the Weibull distribution of tensile properties in a cast Al-5 pct Si-3 pct Cu-1 pct Fe-0.3 pct Mg alloy. Metallurgical and Materials Transactions A. 38(3), 659-670. DOI: 10.1007/s11661-006-9068-3
[5] Tunçay, T., Özyürek, D., Dişpinar, D. & Tekeli, S. (2020). The effects of Cr and Zr additives on the microstructure and mechanical properties of A356 alloy. Transactions of the Indian Institute of Metals. 73(5), 1273-1285. DOI: 10.1007/s12666-020-01970-4
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Authors and Affiliations

E.N. Bas
1
S. Alper
1
T. Tuncay
2
ORCID: ORCID
D. Dispinar
3
ORCID: ORCID
S. Kirtay
1
ORCID: ORCID

  1. Istanbul University-Cerrahpasa, Turkey
  2. Karabuk University, Turkey
  3. Foseco, Netherlands
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Abstract

The paper presents the effect of tin on the crystallization process, microstructure and hardness of cast iron with compacted (vermicular) graphite. The compacted graphite was obtained with the use of magnesium treatment process (Inmold technology). The lack of significant effect of tin on the temperature of the eutectic transformation has been demonstrated. On the other hand, a significant decrease in the eutectoid transformation temperature with increasing tin concentration has been shown. It was demonstrated that tin narrows the temperature range of the austenite transformation. The effect of tin on the microstructure of cast iron with compacted graphite considering casting wall thickness has been investigated and described. The carbide-forming effect of tin in thin-walled (3 mm) castings has been demonstrated. The nomograms describing the microstructure of compacted graphite iron versus tin concentration have been developed. The effect of tin on the hardness of cast iron was given.

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Authors and Affiliations

Grzegorz Gumienny
ORCID: ORCID
B. Kurowska
ORCID: ORCID
P. Fabian
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Abstract

In this study, the microstructures and mechanical properties of X70 pipeline steels produced with varying Mo contents, accelerated cooling rate and intermediate slab blank thickness are systematically investigated. Results showed that the microstructures and mechanical properties of the X70 pipeline steels were strongly affected by Mo addition. The pearlite and proeutectoid ferrite formation is obviously inhibited in containing-Mo steel and the acicular ferrite (AF) is obtained in a wide range of cooling rates. With the increasing the cooling rates, the AF constituent amount increases. The grains can be refined by increasing the thickness of intermediate slab for enhancing the cumulative reduction rates, and meanwhile increase the number density of precipitates. It was proved by simulation and industrial trials that the low-alloy X70 pipeline steels can be produced increasing cooling rates and the thickness of intermediate slab without strength and toughness degradation which also reduce alloy cost.
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Authors and Affiliations

Haijian Xu
1
ORCID: ORCID
Chufei Han
2
Pingyuan Yan
2
ORCID: ORCID
Baochun Zhao
2
ORCID: ORCID
Weijuan Li
1
ORCID: ORCID

  1. School of Materials and Metallurgy, University of Science and Technology Liaoning, Anshan, 114051, P.R. China
  2. Angang Steel Company Limited, Anshan, 114009, P.R. China
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Abstract

Steel is basically used in construction, automobile, buildings, infrastructure, tools, ships, appliances, machines and weapons due to its good mechanical as well as metallurgical properties. Heat treatment of steels significantly enhance its mechanical and metallurgical properties due to the formation of various phases depending upon the type of steel used for specific application. In present study, blank of EN353 grade steel having different sizes were used to investigate the effect of heat treatment and microstructural changes. JMat-Pro software was used to predict the continuous cooling transformation behaviour of EN353 steel. Different phases such as bainite, perlite and other carbide inclusion can be observed in the microstructural examination. Pearlitic microstructure developed for the specimen of size 40×40×40 mm heated at 870°C for 2 hrs and then isothermal heating was performed for same specimen at 600°C for 73 min followed by air cooling.
Relevance Statement: Steel is an important material which is frequently used in almost all areas such as structure building, pressure vessels, transportation and many more other applications. Addition of alloying elements in parent steel significantly improve the metallurgical as well as mechanical properties. Steel properties like tensile strength, toughness, ductility, corrosion resistance, wear resistance, hardness, hot hardness, weldability, fatigue etc. significantly improved with the addition of alloying and heat treatment. Heat treatment processes can be used to improve the properties of steel which are frequently used in many manufacturing industries. Different grades of steels which are heat treated under a set of sequence of heating and cooling to change their physical and mechanical properties so that it can fulfil its function under loading condition. With the help of heat treatment process desired microstructure has been achieved which exhibit good mechanical properties of steels.
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Authors and Affiliations

Lochan Sharma
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ORCID: ORCID
Sandeep Kumar Chaubey
ORCID: ORCID

  1. Chandigarh University, Institute of Engineering, Mechanical Engineering Department, Mohali-140413, Punjab, India
  2. University Centre for Research & Development, Chandigarh University, Mohali-140413, Punjab, India

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