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Number of results: 21
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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

The effect of shell side and coil side volume flow rate on overall heat transfer coefficient, effectiveness, pressure drop and exergy loss of shell and helical coil heat exchanger were studied experimentally under steady state conditions. The working fluid, i.e., water was allowed to flow at three different flow rates of 1, 2, and 3 l/min on shell side (cold water) and at 1, 1.5, 2, 2.5, and 3 l/min on coil side (hot water) for each shell side flow rate at the temperatures of 298±0.4K and 323±0.4K, respectively. The results found that the overall heat transfer coefficient increased with increasing both shell side and coil side volume flow rates. The inner Nusselt number significantly increased with the coil side Dean number.

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Authors and Affiliations

Rajesh Kumar
Prakash Chandra
Prabhansu
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Abstract

The paper presents an experimental investigation of a silicone based heat exchanger, with passive heat transfer intensification by means of surface enhancement. The main objective of this paper was to experimentally investigate the performance of a heat exchanger module with the enhanced surface. Heat transfer in the test section has been examined and described with precise measurements of thermal and flow conditions. Reported tests were conducted under steady-state conditions for single-phase liquid cooling. Proposed surface modification increases heat flux by over 60%. Gathered data presented, along with analytical solutions and numerical simulation allow the rational design of heat transfer devices.

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Authors and Affiliations

Tomasz Muszyński
Rafał Andrzejczyk
Il Wong Park
Carlos Alberto Dorao
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Abstract

Heat transport when two surfaces of solids come into contact is an important phenomenon in many metallurgical processes. Determining the boundary conditions of heat transfer allows to obtain the correct solutions of the heat conduction equation. The paper presents models for determining the heat transfer coefficient between steel materials in contact. Experimental tests were carried out to measure the temperature changes of the contacting samples made of steel S235 (1.0038) and steel 15HM (1.7335) under the pressure of 10, 15 and 20 MPa. There was a large temperature difference between the samples. The results of the experiment were compared with numerically calculated temperatures and the value of the heat transfer coefficient was determined at different pressure values depending on the time.
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Authors and Affiliations

A. Przyłucka-Bednarska
1
ORCID: ORCID
M. Rywotycki
1
ORCID: ORCID
K. Sołek
1
ORCID: ORCID
Z. Malinowski
1
ORCID: ORCID

  1. AGH University of Science And Technology, Faculty of Metals Engineering and Industrial Computer Science, Al. Mickiewicza 30, 30-059 Krakow, Poland
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Abstract

The heat transfer coefficient during the pool boiling on the outside of a horizontal tube can be predicted by correlations. Our choice was based on ten correlations known from the literature. The experimental data were recovered from the recent work, for different fluids used. An evaluation was made of agreement between each of the correlations and the experimental data. The results of the present study firstly showed a good reliability for the correlations of Labuntsov [10], Stephan and Abdeslam [11] with deviations of 20% and 27%, respectively. Also, the results revealed acceptable agreements for the correlations of Kruzhlin [6], Mc Nelly [7] and Touhami [15] with deviations of 26%, 29% and 29% respectively. The remaining correlations showed very high deviations from the experimental data. Finally, improvements have been made in the correlations of Shekriladze [12] and Mostinski [9], and a new correlation was proposed giving convincing results.
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Bibliography

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[3] T. Baki, A. Aris, and M. Tebbal. Investigations on pool boiling of refrigerant R141b outside a horizontal tube, Archive of Mechanical Engineering, 68(1):77–92, 2021. doi: 10.24425/ame.2021.137042.
[4] T. Baki. Survey on the nucleate pool boiling of hydrogen and its limits. Journal of Mechanical and Energy Engineering, 4(2):157–166, 2020. doi: 10.30464/jmee.2020.4.2.157.
[5] T. Baki. Pool boiling of ammonia, assessment of correlations. International Journal of Air-Conditioning and Refrigeration, 29(02):2150012, 2021. doi: 10.1142/S2010132521500127.
[6] G.N. Kruzhilin. Free-convection transfer of heat from a horizontal plate and boiling liquid. Doklady AN SSSR (Reports of the USSR Academy of Sciences), 58(8):1657–1660, 1947.
[7] M.J. Mc Nelly. A correlation of rates of heat transfer to nucleate boiling of liquids. Journal of Imperial College Chemical Engineering Socoiety, 7:187–34, 1953.
[8] H.K. Forster, and N. Zuber. Dynamics of vapor bubbles and boiling heat transfer. AIChE Journal, 1(4):531–535, 1955. doi: 10.1002/aic.690010425.
[9] I.L. Mostinski. Application of the rule of corresponding states for calculation of heat transfer and critical heat flux. Teploenergetika, 4(4):66–71, 1963.
[10] D.A. Labuntsov. Heat transfer problems with nucleate boiling of liquids. Thermal Engineering, 19(9):21–28, 1972.
[11] K. Stephan, and M. Abdelsalam. Heat-transfer correlations for natural convection boiling. International Journal of Heat and Mass Transfer, 23(1):73–87, 1980. doi: 10.1016/0017-9310(80)90140-4.
[12] I.G. Shekriladze. Boiling heat transfer: mechanisms, models, correlations and the lines of further research. The Open Mechanical Engineering Journal, 2:104–127, 2008. doi: 10.2174/1874155X00802010104.
[13] V.V. Yagov. Nucleate boiling heat transfer: Possibilities and limitations of theoretical analysis. Heat and Mass Transfer, 45(7):881–892, 2009. doi: 10.1007/s00231-007-0253-8.
[14] S. Fazel and S. Roumana. Pool boiling heat transfer to pure liquids. In WSEAS Conf, 2010.
[15] T. Baki, A. Aris, and M. Tebbal. Proposal for a correlation raising the impact of the external diameter of a horizontal tube during pool boiling. International Journal of Thermal Sciences, 84:293–299, 2014. doi: 10.1016/j.ijthermalsci.2014.05.023.
[16] M.G. Kang. Effect of surface roughness on pool boiling heat transfer. International Journal of Heat and Mass Transfer, 43(22):4073–4085, 2000. doi: 10.1016/S0017-9310(00)00043-0.
[17] M.G. Kang. Local pool boiling coefficients on a horizontal tubes. Journal of Mechanical Science and Technology, 19(3):860–869, 2005. doi: 10.1007/BF02916134.
[18] J.S. Mehta and S.G. Kandlikar. Pool boiling heat transfer enhancement over cylindrical tubes with water at atmospheric pressure, Part II: Experimental results and bubble dynamics for circumferential V-groove and axial rectangular open microchannels. International Journal of Heat and Mass Transfer, 64:1216–1225, 2013. doi: 10.1016/j.ijheatmasstransfer.2013.04.004.
[19] S.K. Das, N. Putra, and W. Roetzel. Pool boiling of nano-fluids on horizontal narrow tubes. International Journal of Multiphase Flow, 29(8):1237–1247, 2003. doi: 10.1016/S0301-9322 (03)00105-8.
[20] G. Prakash Narayan, K.B. Anoop, G. Sateesh, and S.K. Das. Effect of surface orientation on pool boiling heat transfer of nanoparticle suspensions. International Journal of Multiphase Flow, 34(2):145–160, 2008. doi: 10.1016/j.ijmultiphaseflow.2007.08.004.
[21] D. Gorenflo, F. Gremer, E. Danger, and A. Luke. Pool boiling heat transfer to binary mixtures with miscibility gap: Experimental results for a horizontal copper tube with 4.35~mm O.D. Experimetal Thermal Fluides Sciences, 25(5):243–254, 2001. doi: 10.1016/S0894-1777(01)00072-3.
[22] Z.H. Liu and Y.H. Qiu. Enhanced boiling heat transfer in restricted spaces of a compact tube bundle with enhanced tubes. Applied Thermal Engineering, 22(17):1931–1941, 2002. doi: 10.1016/S1359-4311(02)00111-4.
[23] Y.H. Qiu and Z.H. Liu. Boiling heat transfer of water on smooth tubes in a compact staggered tube bundle. Applied Thermal Engineering, 24(10):1431–1441, 2004. doi: 10.1016/j.applthermaleng.2003.11.021.
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[33] J.M.S. Jabardo, G. Ribatski, and E. Stelute. Roughness and surface material effects on nucleate boiling heat transfer from cylindrical surfaces to refrigerants R-134a and R-123. Experimetal Thermal Fluides Sciences, 33(4):579–590, 2009. doi: 10.1016/j.expthermflusci.2008.12.004.
[34] D. Jung, K. An, and J. Park. Nucleate boiling heat transfer coefficients of HCFC22, HFC134a, HFC125 and HFC32 on various enhanced tubes. International Journal of Refrigeration, 27(2):202–206, 2004. doi: 10.1016/S0140-7007(03)00124-5.
[35] S.P. Rocha, O. Kannengieser, E.M. Cardoso, and J.C. Passos. Nucleate pool boiling of R-134a on plain and micro-finned tubes. International Journal of Refrigeration, 36(2):456–464, 2013. doi: 10.1016/j.ijrefrig.2012.11.031.
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Authors and Affiliations

Touhami Baki
1
ORCID: ORCID
Djamel Sahel
2
ORCID: ORCID

  1. Mechanical Faculty, Gaseous Fuels and Environment Laboratory, USTO-MB, El-M'Naouer, Oran, Algeria
  2. Department of Technical Sciences, Amar Telidji of Laghouat, Algeria
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Abstract

The paper presents the solution to a problem of determining the heat flux density and the heat transfer coefficient, on the basis of temperature measurement at three locations in the flat sensor, with the assumption that the heat conductivity of the sensor material is temperature dependent. Three different methods for determining the heat flux and heat transfer coefficient, with their practical applications, are presented. The uncertainties in the determined values are also estimated.

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Authors and Affiliations

Dawid Taler
Sławomir Grądziel
Jan Taler
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Abstract

The following paper presents the method for solving one-dimensional inverse boundary heat conduction problems. The method is used to estimate the unknown thermal boundary condition on inner surface of a thick-walled Y-branch. Solution is based on measured temperature transients at two points inside the element's wall thickness. Y-branch is installed in a fresh steam pipeline in a power plant in Poland. Determination of an unknown boundary condition allows for the calculation of transient temperature distribution in the whole element. Next, stresses caused by non-uniform transient temperature distribution and by steam pressure inside a Y-branch are calculated using the finite element method. The proposed algorithm can be used for thermal-strength state monitoring in similar elements, when it is not possible to determine a 3-D thermal boundary condition. The calculated temperature and stress transients can be used for the calculation of element durability. More accurate temperature and stress monitoring will contribute to a substantial decrease of maximal stresses that occur during transient start-up and shut-down processes.
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Authors and Affiliations

Sławomir Grądziel
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Abstract

In the paper a method developed earlier by authors is applied to calculations of pressure drop and heat transfer coefficient for flow boiling and also flow condensation for some recent data collected from literature for such fluids as R404a, R600a, R290, R32,R134a, R1234yf and other. The modification of interface shear stresses between flow boiling and flow condensation in annular flow structure are considered through incorporation of the so called blowing parameter. The shear stress between vapor phase and liquid phase is generally a function of nonisothermal effects. The mechanism of modification of shear stresses at the vapor-liquid interface has been presented in detail. In case of annular flow it contributes to thickening and thinning of the liquid film, which corresponds to condensation and boiling respectively. There is also a different influence of heat flux on the modification of shear stress in the bubbly flow structure, where it affects bubble nucleation. In that case the effect of applied heat flux is considered. As a result a modified form of the two-phase flow multiplier is obtained, in which the nonadiabatic effect is clearly pronounced.

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Authors and Affiliations

Dariusz Mikielewicz
Jarosław Mikielewicz
Rafał Andrzejczyk
Blanka Jakubowska
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Abstract

Heating surfaces in power boilers are exposed to very high heat flux. For evaporator protection against overheating, internally helically ribbed tubes are used. The intensification of the heat transfer and the maintenance of the thin water layer in the intercostal space, using ribbed tubes, enables better protection of the power boiler evaporator than smooth pipes. Extended inner surface changes flow and thermal conditions by influencing the linear pressure drop and heat transfer coefficient. This paper presents equations that are used to determine the heat transfer coefficient. The results of total heat transfer, obtained from CFD simulations, for two types of internally ribbed and plain tubes are also presented.

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Authors and Affiliations

Karol Majewski
Sławomir Grądziel
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Abstract

Experimental investigation was conducted on the thermal performance and pressure drop of a convective cooling loop working with ZnO aqueous nanofluids. The loop was used to cool a flat heater connected to an AC autotransformer. Influence of different operating parameters, such as fluid flow rate and mass concentration of nanofluid on surface temperature of heater, pressure drop, friction factor and overall heat transfer coefficient was investigated and briefly discussed. Results of this study showed that, despite a penalty for pressure drop, ZnO/water nanofluid was a promising coolant for cooling the micro-electronic devices and chipsets. It was also found that there is an optimum for concentration of nanofluid so that the heat transfer coefficient is maximum, which was wt. %=0.3 for ZnO/water used in this research. In addition, presence of nanoparticles enhanced the friction factor and pressure drop as well; however, it is not very significant in comparison with those of registered for the base fluid.

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Authors and Affiliations

Amir Arya
Saeed Shahmiry
Vahid Nikkhah
Mohamad Mohsen Sarafraz
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Abstract

Solar air heater is regarded as the most common and popular solar thermal system and has a wide range of applications, from residential to industrial. Solar air heater is not viable because of the low convective heat transfer coefficient at the absorber plate which contributes to decreasing the thermal efficiency. Artificial coarseness on the plain surface is the most effective method to enhance heat transfer with a moderate rate of friction factor of flowing air in the design of solar air heater duct. The different parameters and different artificial coarseness are responsible to alter the flow structure and heat transfer rate. Over the years different artificial roughness and how its geometry affects the performance of solar air heater have been thoroughly studied. Various investigators report the correlations between heat transfer and friction factors. In the present study, a comparison of several artificial coarseness geometries and methods with a view to enhancing the performance of solar air heater has been made. A brief outline has also been presented for future research.
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Authors and Affiliations

Manoj Kumar Dubey
1
Om Prakash
1

  1. National Institute of Technology Patna, Patna, Bihar 800005, India
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Abstract

In this experimental investigation, the critical heat flux (CHF) of aqua-based multiwalled carbon nanotube (MWCNT) nanofluids at three different volumetric concentrations 0.2%, 0.6%, and 0.8% were prepared, and the test results were compared with deionized water. Different characterization techniques, including X-ray diffraction, scanning electron microscopy and Fourier transform infrared, were used to estimate the size, surface morphology, agglomeration size and chemical nature of MWCNT. The thermal conductivity and viscosity of the MWCNT at three different volumetric concentrations was measured at a different temperature, and results were compared with deionized water. Although, MWCNT-deionized water nanofluid showed superior performance in heat transfer coefficient as compared to the base fluid. However, the results proved that the critical heat flux is increased with an increase in concentrations of nanofluids.

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Authors and Affiliations

D. Vasudevan
D. Senthil Kumar
A. Murugesan
C. Vijayakumar
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Abstract

The interrelation between fuzzy logic and cluster renewal approaches for heat transfer modeling in a circulating fluidized bed (CFB) has been established based on a local furnace data. The furnace data have been measured in a 1296 t/h CFB boiler with low level of flue gas recirculation. In the present study, the bed temperature and suspension density were treated as experimental variables along the furnace height. The measured bed temperature and suspension density were varied in the range of 1131–1156 K and 1.93–6.32 kg/m3, respectively. Using the heat transfer coefficient for commercial CFB combustor, two empirical heat transfer correlation were developed in terms of important operating parameters including bed temperature and also suspension density. The fuzzy logic results were found to be in good agreement with the corresponding experimental heat transfer data obtained based on cluster renewal approach. The predicted bed-to-wall heat transfer coefficient covered a range of 109–241 W/(m2K) and 111–240 W/(m2), for fuzzy logic and cluster renewal approach respectively. The divergence in calculated heat flux recovery along the furnace height between fuzzy logic and cluster renewal approach did not exceeded ±2%.

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Authors and Affiliations

Artur Błaszczuk
Jarosław Krzywański
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Abstract

This paper focuses on assessment of the effect of flue gas recirculation (FGR) on heat transfer behavior in 1296t/h supercritical coal-fired circulating fluidized bed (CFB) combustor. The performance test in supercritical CFB combustor with capacity 966 MWthwas performed with the low level of flue gas recirculation rate 6.9% into furnace chamber, for 80% unit load at the bed pressure of 7.7 kPa and the ratio of secondary air to the primary air SA/PA = 0.33. Heat transfer behavior in a supercritical CFB furnace between the active heat transfer surfaces (membrane wall and superheater) and bed material has been analyzed for Geldart B particle with Sauter mean diameters of 0.219 and 0.246 mm. Bed material used in the heat transfer experiments had particle density of 2700 kg/m3. A mechanistic heat transfer model based on cluster renewal approach was used in this work. A heat transfer analysis of CFB combustion system with detailed consideration of bed-to-wall heat transfer coefficient distributions along furnace height is investigated. Heat transfer data for FGR test were compared with the data obtained for representative conditions without recycled flue gases back to the furnace through star-up burners.
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Authors and Affiliations

Artur Błaszczuk
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Abstract

This paper presents the results of studies in two phase gasliquid flow around tube bundle in the model of shell tube heat exchanger. Experimental investigations of heat transfer coefficient on the tubes surface were performed with the aid of electrochemical technique. Chilton-Colburn analogy between heat and mass transfer was used. Twelve nickel cathodes were mounted on the outside surface of one of the tubes. Measurement of limiting currents in the cathodic reduction of ferricyanide ions on nickel electrodes in aqueous solution of equimolar quantities of K3Fe(CN)6and K4Fe(CN)6in the presence of NaOH basic solution were applied to determine the mass transfer coefficient. Controlled diffusion from ions at the electrode was observed and limiting current plateau was measured. Measurements were performed with data acquisition equipment controlled by software created for this experiment. Mass transfer coefficient was calculated on the basis of the limiting current measurements. Results of mass transfer experiments (mass transfer coefficient) were recalculated to heat transfer coefficient. During the experiments, simultaneously conducted was the the investigation of two-phase flow structures around tubes with the use of digital particle image velocimetry. Average velocity fields around tubes were created with the use of a number of flow images and compared with the results of heat transfer coefficient calculations.

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Authors and Affiliations

Daniel Zając
Marcin Karaś
Roman Ulbrich
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Abstract

The Bulletin of the Polish Academy of Sciences: Technical Sciences (Bull.Pol. Ac.: Tech.) is published bimonthly by the Division IV Engineering Sciences of the Polish Academy of Sciences, since the beginning of the existence of the PAS in 1952. The journal is peer‐reviewed and is published both in printed and electronic form. It is established for the publication of original high quality papers from multidisciplinary Engineering sciences with the following topics preferred: Artificial and Computational Intelligence, Biomedical Engineering and Biotechnology, Civil Engineering, Control, Informatics and Robotics, Electronics, Telecommunication and Optoelectronics, Mechanical and Aeronautical Engineering, Thermodynamics, Material Science and Nanotechnology, Power Systems and Power Electronics.

Journal Metrics: JCR Impact Factor 2018: 1.361, 5 Year Impact Factor: 1.323, SCImago Journal Rank (SJR) 2017: 0.319, Source Normalized Impact per Paper (SNIP) 2017: 1.005, CiteScore 2017: 1.27, The Polish Ministry of Science and Higher Education 2017: 25 points.

Abbreviations/Acronym: Journal citation: Bull. Pol. Ac.: Tech., ISO: Bull. Pol. Acad. Sci.-Tech. Sci., JCR Abbrev: B POL ACAD SCI-TECH Acronym in the Editorial System: BPASTS.

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Authors and Affiliations

Rafał Andrzejczyk
Tomasz Muszyński
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Abstract

Experimental research has been carried out in a supercritical circulating fluidized bed combustor in order to indicate the effect of the bed particle size on bed-to-wall heat transfer coefficient. The bed inventory used were 0.219, 0.246 and 0.411 mm Sauter mean particles diameter. The operating parameters of a circulating fluidized bed combustor covered a range from 3.13 to 5.11 m/s for superficial gas velocity, 23.7 to 26.2 kg/(m2s) for the circulation rate of solids, 0.33 for the secondary air fraction and 7500 to 8440 Pa pressure drop. Furthermore, the bed temperature, suspension density and the main parameters of cluster renewal approach were treated as experimental variables along the furnace height. The cluster renewal approach was used in order to predict the bed-to-wall heat transfer coefficient. A simple semi-empirical method was proposed to estimate the overall heat transfer coefficient inside the furnace as a function of particle size and suspension density. The computationally obtained results were compared with the experimental data of this work.
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Authors and Affiliations

A. Błaszczuk
W. Nowak
S. Jagodzik
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Abstract

The purpose of this work is to find a correlation for heat transfer to walls in a 1296 t/h supercritical circulating fluidised bed (CFB) boiler. The effect of bed-to-wall heat transfer coefficient in a long active heat transfer surface was discussed, excluding the radiation component. Experiments for four different unit loads (i.e. 100% MCR, 80% MCR, 60% MCR and 40% MCR) were conducted at a constant excess air ratio and high level of bed pressure (ca. 6 kPa) in each test run. The empirical correlation of the heat transfer coefficient in a large-scale CFB boiler was mainly determined by two key operating parameters, suspension density and bed temperature. Furthermore, data processing was used in order to develop empirical correlation ranges between 3.05 to 5.35 m·s-1 for gas superficial velocity, 0.25 to 0.51 for the ratio of the secondary to the primary air, 1028 to 1137K for bed temperature inside the furnace chamber of a commercial CFB boiler, and 1.20 to 553 kg·m-3 for suspension density. The suspension density was specified on the base of pressure measurements inside the boiler’s combustion chamber using pressure sensors. Pressure measurements were collected at the measuring ports situated on the front wall of the combustion chamber. The obtained correlation of the heat transfer coefficient is in agreement with the data obtained from typical industrial CFB boilers.

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Authors and Affiliations

Wojciech Nowak
Artur Błaszczuk
Szymon Jagodzik
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Abstract

The energy saving tendencies, in reference to residential buildings, can be recently seen in Europe and in the world. Therefore, there are a lot of studies being conducted aiming to find technical solutions in order to improve the energy efficiency of existing, modernized, and also new buildings. However, there are obligatory solutions and requirements, which must be implemented during designing stage of the building envelope and its heating/cooling system. They are gathered in the national regulations.

The paper describes the process of raising the energy standard of buildings between 1974–2021 in Poland. Therefore, the objective of this study is to show energy savings, which can be generated by modernization of thermal insulation of partitions of existing buildings and by the use of different ways of heat supply. The calculations are made on the selected multi-family buildings located in Poland, with the assumption of a 15 years payback time.

It is shown that it is not possible to cover the costs of the modernization works by the projected savings with the compliance to the assumption of 15 years payback time.

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Authors and Affiliations

A. Życzyńska
T. Cholewa
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Abstract

The main purpose of this study is to analyze the thermomechanical behavior of the dry contact between the brake disc and pads during the braking phase. The simulation strategy is based on softawe ANSYS11. The modeling of transient temperature in the disc brake is actually used to identify the factor of geometric design of the disc to install the ventilation system in vehicles. The thermal-structural analysis is then used with coupling to determine the deformation established and the Von Mises stress in the disc, the contact pressure distribution in pads. The results are satisfactory compared to those of the specialized literature.

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Authors and Affiliations

Ali Belhocine
Mostefa Bouchetara
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Abstract

Cooling is indispensable for maintaining the desired performance and reliability over a very huge variety of products like electronic devices, computer, automobiles, high power laser system etc. Apart from the heat load amplification and heat fluxes caused by many industrial products, cooling is one of the major technical challenges encountered by the industries like manufacturing sectors, transportation, microelectronics, etc. Normally water, ethylene glycol and oil are being used as the fluid to carry away the heat in these devices. The development of nanofluid generally shows a better heat transfer characteristics than the water. This research work summarizes the experimental study of the forced convective heat transfer and flow characteristics of a nanofluid consisting of water and 1% Al2O3(volume concentration) nanoparticle flowing in a parallel flow, counter flow and shell and tube heat exchanger under laminar flow conditions. The Al2O3 nanoparticles of about 50 nm diameter are used in this work. Three different mass flow rates have been selected and the experiments have been conducted and their results are reported. This result portrays that the overall heat transfer coefficient and dimensionless Nusselt number of nanofluid is slightly higher than that of the base liquid at same mass flow rate at same inlet temperature. From the experimental result it is clear that the overall heat transfer coefficient of the nanofluid increases with an increase in the mass flow rate. It shows that whenever mass flow rate increases, the overall heat transfer coefficient along with Nusselt number eventually increases irrespective of flow direction. It was also found that during the increase in mass flow rate LMTD value ultimately decreases irrespective of flow direction. However, shell and tube heat exchanger provides better heat transfer characteristics than parallel and counter flow heat exchanger due to multi pass flow of nanofluid. The overall heat transfer coefficient, Nusselt number and logarithmic mean temperature difference of the water and Al2O3/water nanofluid are also studied and the results are plotted graphically.

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Bibliography

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Authors and Affiliations

R. Dharmalingam
K.K. Sivagnanaprabhu
J. Yogaraja
S. Gunasekaran
R. Mohan

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