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  • 1. Ahangar Zonouzi, S.
    et al.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Safarzadeh, H.
    Aminfar, H.
    Trushkina, Y.
    Mohammadpourfard, M.
    Ghanbarpour, Morteza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Salazar Alvarez, G.
    Experimental investigation of the flow and heat transfer of magnetic nanofluid in a vertical tube in the presence of magnetic quadrupole field2018In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 91, p. 155-165Article in journal (Refereed)
    Abstract [en]

    In this paper, the effects of applying magnetic field on hydrodynamics and heat transfer of Fe3O4/water magnetic nanofluid flowing inside a vertical tube have been studied experimentally. The applied magnetic field was resulted from quadrupole magnets located at different axial positions along the tube length. The variations of the local heat transfer coefficient and also the pressure drop of the ferrofluid flow along the length of the tube by applying the magnetic quadrupole field have been investigated for different Reynolds numbers. The obtained experimental results show maximum enhancements of 23.4%, 37.9% and 48.9% in the local heat transfer coefficient for the magnetic nanofluid with 2 vol% Fe3O4 in the presence of the quadrupole magnets located at three different axial installation positions for the Reynolds number of 580 and the relative increase in total pressure drop by applying the magnetic field is about 1% for Re = 580. The increase of the heat transfer coefficient is due to the radial magnetic force toward the heated wall generated by magnetic quadrupole field acting over the ferrofluid flowing inside the tube so that the velocity of the ferrofluid in the vicinity of the heated wall is increased. It is also observed that the enhancement of heat transfer coefficient by applying magnetic quadrupole is decreased with increasing the Reynolds number.

  • 2. Anwar, Z.
    et al.
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Dryout characteristics of natural and synthetic refrigerants in single vertical mini-channels2015In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 68, p. 257-267Article in journal (Refereed)
    Abstract [en]

    Experimental results on dryout of seven refrigerants (R134a, R1234yf, R152a, R22, R245fa, R290 and R600a) in small, single vertical tubes under upward flow conditions are reported in this study. The experiments were conducted under a wide range of operating conditions in stainless steel tubes (0.64-1.70. mm and 213-245. mm heated length). The effects of operating parameters like mass flux, vapor quality, saturation pressure and channel size are discussed in detail. In general, dryout heat flux increased with increasing mass flux, and with increasing tube diameter. No effect of varying saturation temperature was observed. The experimental findings were compared with well-known macro and micro-scale correlations from the literature and it was found that Wu's correlation (in modified form) quite satisfactorily predicted the whole database. A new correlation for prediction of heat flux at dryout conditions is also proposed.

  • 3. Anwar, Z.
    et al.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Flow boiling heat transfer and dryout characteristics of R152a in a vertical mini-channel2014In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 53, p. 207-217Article in journal (Refereed)
    Abstract [en]

    This article reports on flow boiling heat transfer and dryout characteristics of R152a in a vertical mini-channel. The experiments were carried out with a resistively heated stainless steel tube (1.60mm in diameter and 245mm heated length) at 27 and 32°C saturation temperature. Five mass fluxes in the range 100-500kg/m2s with heat fluxes from 5 to 245kW/m2 were tested. Under similar operating conditions experiments were repeated with R134a in the same setup to compare thermal performance of R152a. The results showed that the heat transfer was strongly influenced by the applied heat flux with insignificant convective contributions. The dryout heat flux increased with increasing mass flux but no effect of varying operating pressure was noticed. The experimental results for heat transfer and dryout heat flux were compared with well-known macro and micro-scale correlations from the literature.

  • 4.
    Anwar, Zahid
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration. Department of Mechanical, Mechatronics and Manufacturing Engineering (KSK-Campus), University of Engineering and Technology, Lahore, Pakistan .
    Palm, Björn E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Flow boiling heat transfer, pressure drop and dryout characteristics of R1234yf: Experimental results and predictions2015In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 66, p. 137-149Article in journal (Refereed)
    Abstract [en]

    Flow boiling heat transfer, pressure drop and dryout characteristics of R1234yf in a vertical stainless steel test section (1.60mm inside diameter and 245mm heated length) under upward flow conditions are reported in this article. The experiments were carried out at 27 and 32°C saturation temperatures with five mass fluxes in the range of 100-500kg/m2s while the applied heat flux was in the range of 5-130kW/m2. The experiments were carried out with gradual increase of the applied heat flux til completion of dryout. Under similar conditions, tests were repeated with R134a in the same test setup to compare thermal performance of these two refrigerants. The results showed that boiling heat transfer was strongly controlled by the applied heat flux and operating pressure with insignificant dependence on mass flux and vapor quality. The frictional pressure drop increased with mass flux and vapor quality and decreased with increasing saturation temperature as expected. Signs of dryout first appeared at vapor qualities of 85%, with the values generally increasing with increasing mass flux. The effect of varying system pressure was insignificant. The experimental results (boiling heat transfer, pressure drop and dryout heat flux) were compared with the predictions from well-known correlations (for macro and micro-scale channels) from the literature.

  • 5.
    Bitaraf Haghighi, Ehsan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Nikkam, Nader
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Anwar, Zahid
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lumbreras, Itziar
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Behi, Mohammadreza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Mirmohammadi, Seyed A.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Poth, Heiko
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Cooling performance of nanofluids in a small diameter tube2013In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 49, p. 114-122Article in journal (Refereed)
    Abstract [en]

    This article reports convective single-phase heat transfer performance in laminar flow for some selected nanofluids (NFs) in an open small diameter test section. A 0.50 mm inner diameter, 30 cm long stainless steel test section was used for screening single phase laminar convective heat transfer with water and five different water based NFs. Tested NFs were; Al2O3 (two types), TiO2 (two types) and CeO2 (one type), all 9 wt.% particle concentration. The effective thermal conductivity of the NFs were measured with Transient Plane Source (TPS) method and viscosity were measured with a rotating coaxial cylindrical viscometer. The obtained experimental results for thermal conductivity were in good agreement with the predicted values from Maxwell equation. The local Shah correlation, which is conventionally used for predicting convective heat transfer in laminar flow in Newtonian fluids with constant heat flux boundary condition, was shown to be valid for NFs. Moreover, the Darcy correlation was used to predict the friction factor for the NFs as well as for water. Enhancement in heat transfer for NFs was observed, when compared at equal Reynolds number, as a result of higher velocity or mass flow rate of the NFs at any given Reynolds number due to higher viscosity for NFs. However, when compared at equal pumping power no or only minor enhancement was observed.

  • 6.
    Bitaraf Haghighi, Ehsan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Utomo, Adi T.
    Ghanbarpour, Morteza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Zavareh, Ashkan I. T.
    Poth, Heiko
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Pacek, Andrzej
    Palm, Bjoern E.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Experimental study on convective heat transfer of nanofluids in turbulent flow: Methods of comparison of their performance2014In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 57, p. 378-387Article in journal (Refereed)
    Abstract [en]

    Turbulent convective heat transfer coefficients of 9 wt% Al2O3/water and TiO2/water nanofluids inside a circular tube were investigated independently at the Royal Institute of Technology, KTH (Sweden) and at University of Birmingham (UK). The experimental data from both laboratories agreed very well and clearly show that Nusselt numbers are well correlated by the equations developed for single phase fluids with the thermophysical properties of nanofluid. The heat transfer coefficients of nanofluids can be compared with those of the base fluids at the same Reynolds number or at the same pumping power. As the same Reynolds number requires higher flow rate of nanofluids therefore such comparison shows up to 15% increase in heat transfer coefficient. However, at equal pumping power, the heat transfer coefficient of Al2O3 nanofluid was practically the same as that of water while that of TiO2 was about 10% lower. Comparing performance at equal Reynolds number is clearly misleading since the heat transfer coefficient can always be increased by increased pumping power, accordingly, the comparison between the fluids should be done at equal pumping power.

  • 7. Discetti, S.
    et al.
    Bellani, G.
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Serpieri, J.
    Sanmiguel Vila, C.
    Raiola, M.
    Zheng, X.
    Mascotelli, L.
    Talamelli, Alessandro
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Ianiro, A.
    Characterization of very-large-scale motions in high-Re pipe flows2019In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Very-large-scale structures in pipe flows are characterized using an extended Proper Orthogonal Decomposition (POD)-based estimation. Synchronized non-time-resolved Particle Image Velocimetry (PIV) and time-resolved, multi-point hot-wire measurements are integrated for the estimation of turbulent structures in a pipe flow at friction Reynolds numbers of 9500 and 20000. This technique enhances the temporal resolution of PIV, thus providing a time-resolved description of the dynamics of the large-scale motions. The experiments are carried out in the CICLoPE facility. A novel criterion for the statistical characterization of the large-scale motions is introduced, based on the time-resolved dynamically-estimated POD time coefficients. It is shown that high-momentum events are less persistent than low-momentum events, and tend to occur closer to the wall. These differences are further enhanced with increasing Reynolds number.

  • 8.
    Ghanbarpour, Morteza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Bitaraf Haghigi, Ehsan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Thermal properties and rheological behavior of water based Al2O3 nanofluid as a heat transfer fluid2014In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 53, p. 227-235Article in journal (Refereed)
    Abstract [en]

    An experimental investigation and theoretical study of thermal conductivity and viscosity of Al2O3/water nanofluids are presented in this article. Various suspensions containing Al2O3 nanoparticles were tested in concentration ranging from 3% to 50% in mass and temperature ranging from 293K to 323K. The results reveal that both the thermal conductivity and viscosity of nanofluids increase with temperature and particle concentration accordingly while the increase in viscosity is much higher than the increase in thermal conductivity. The thermal conductivity and viscosity enhancement are in the range of 1.1-87% and 18.1-300%, respectively. Moreover, the results indicate that the thermal conductivity increases nonlinearly with concentration, but, linearly with the increase in temperature. In addition, the experimental results are compared with some existing correlations from literature and some modifications are suggested. Finally, the average heat transfer coefficient at different basis of comparisons including equal Reynolds number, fluid velocity and pumping power is studied based on the experimental thermal conductivity and viscosity in fully developed laminar and turbulent flow regimes. It is found that equal Reynolds number as a basis of comparison is highly misleading and equal pumping power can be used to study the advantage of using nanofluid instead of the base fluid.

  • 9.
    Giri, Asis
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Park, Hyun Sun
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Sehgal, Balraj
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Analysis of bubble dynamics in explosive boiling of droplet with fine fragmentation2005In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 29, no 3, p. 295-303Article in journal (Refereed)
    Abstract [en]

    If a high temperature liquid comes into contact with cold and volatile liquid, rapid (or explosive) evaporation may occur spontaneously or triggered by the impact of a pressure wave. This event generating a shock wave is called a steam explosion. It involves many multiphase flow and heat transfer phenomena. One of the more important phenomena in a steam explosion is the fine fragmentation of the hot liquid, which determines the explosive heat transfer from the hot liquid to the cold liquid and the vaporisation rate of the cold liquid. When a small hot single drop (similar to1 mm) interacts with the coolant, a vapour bubble is formed around the drop. It was observed experimentally that these vapour bubbles grow and collapse. During this process, the small hot droplet fragments and generates finer particles. To understand the fine fragmentation process during a steam explosion, in this study, this phenomenon was examined by using non-linear stability analysis of vapour bubble dynamics based on a concept developed by Inoue et al. [Chem. Eng. Commun. 118 (1992) 189]. From the analysis, it was observed that higher spherical modes were very much unstable during collapse process, which decided the size of the fragmented particles. Vapour shell between molten metal and coolant was considered unstable if the amplitude of one of the spherical modes was greater than vapour shell thickness. In addition, the mass of fragmented particles during each cycle of vapour bubble dynamics was predicted from the analysis. The calculated results were found to be in reasonable agreement with the previously reported [J. Non-Equil. Thermodyn. 13 (1988) 27] experimental results.

  • 10.
    Grozdek, Marino
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Experimental investigation of ice slurry flow pressure drop in horizontal tubes2009In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 33, no 2, p. 357-370Article in journal (Refereed)
    Abstract [en]

    Pressure drop behaviour of ice slurry based on ethanol-water mixture in circular horizontal tubes has been experimentally investigated. The secondary fluid was prepared by mixing ethyl alcohol and water to obtain initial alcohol concentration of 10.3% (initial freezing temperature -4.4 degrees C). The pressure drop tests were conducted to cover laminar and slightly turbulent flow with ice mass fraction varying from 0% to 30% depending on test conditions. Results from flow tests reveal much higher pressure drop for higher ice concentrations and higher velocities in comparison to the single phase flow. However for ice concentrations of 15% and higher, certain velocity exists at which ice slurry pressure drop is same or even lower than for single phase flow. It seems that higher ice concentration delay flow pattern transition moment (from laminar to turbulent) toward higher velocities. In addition experimental results for pressure drop were compared to the analytical results, based on Poiseulle and Buckingham-Reiner models for laminar flow, Blasius. Darby and Melson, Dodge and Metzner, Steffe and Tomita for turbulent region and general correlation of Kitanovski which is valid for both flow regimes. For laminar flow and low buoyancy numbers Buckingham-Reiner method gives good agreement with experimental results while for turbulent flow best fit is provided with Dodge-Metzner and Tomita methods. Furthermore, for transport purposes it has been shown that ice mass fraction of 20% offers best ratio of ice slurry transport capability and required pumping power.

  • 11.
    Guemes, A.
    et al.
    Univ Carlos III Madrid, Aerosp Engn Res Grp, Leganes, Spain..
    Vila, C. Sanmiguel
    Univ Carlos III Madrid, Aerosp Engn Res Grp, Leganes, Spain..
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Vinuesa, Ricardo
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Schlatter, Philipp
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Ianiro, A.
    Univ Carlos III Madrid, Aerosp Engn Res Grp, Leganes, Spain..
    Discetti, S.
    Univ Carlos III Madrid, Aerosp Engn Res Grp, Leganes, Spain..
    Flow organization in the wake of a rib in a turbulent boundary layer with pressure gradient2019In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 108, p. 115-124Article in journal (Refereed)
    Abstract [en]

    The effect of a streamwise pressure gradient on the wake developed by wall-attached square ribs in a turbulent boundary layer is investigated experimentally. Favourable-, adverse- and zero-pressure-gradient conditions (FPG, APG and ZPG, respectively) are reproduced at matched friction Reynolds number and non-dimensional rib height. Flow-field measurements are carried out by means of Particle Image Velocimetry (PIV). Turbulence statistics are extracted at high resolution using an Ensemble Particle Tracking Velocimetry approach. Modal analysis is performed with Proper Orthogonal Decomposition (POD). We demonstrate that a non-dimensional expression of the pressure gradient and shear stress is needed to quantify the pressure-gradient effects in the wake developing past wall-attached ribs. We suggest the Clauser pressure-gradient parameter beta, commonly used in the literature for the characterization of turbulent boundary layers under the effect of a pressure gradient, as a suitable parameter. The results show that, in presence of an adverse pressure gradient, the recirculation region downstream of the rib is increased in size, thus delaying the reattachment, and that the peak of turbulence intensity and the shed eddies are shifted towards larger wall-normal distances than in the ZPG case. The observed changes with respect to the ZPG configuration appear more intense for larger magnitude of beta, which are more likely to be obtained in APG than in FPG due to the reduced skin friction and increased displacement thickness.

  • 12.
    Hansson, Roberta Concilio
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Park, Hyun Sun
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Dinh, Truc-Nam
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Simultaneous high speed digital cinematographic and X-ray radiographic imaging of a intense multi-fluid interaction with rapid phase changes2009In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 33, no 4, p. 754-763Article in journal (Refereed)
    Abstract [en]

    As typical for the study of the vapor explosions, the qualitative and quantitative understanding of the phenomena requires visualization of both material and interface dynamics. A new approach to multifluid multiphase visualization is presented with the focus on the development of a synchronized highspeed visualization by digital cinematography and X-ray radiography. The developed system, named SHARP (simultaneous high-speed acquisition of X-ray radiography and photography), and its image processing methodology, directed to an image synchronization procedure and a separate quantification of vapor and molten material dynamics, is presented in this paper. Furthermore, we exploit an intrinsic property of the X-ray radiation, namely the differences in linear mass attenuation coefficients over the beam path through a multi-component system, to characterize the evolution of molten material distribution. Analysis of the data obtained by the SHARP system and image processing procedure developed granted new insights into the physics of the vapor explosion phenomena, as well as, quantitative information of the associated dynamic micro-interactions.

  • 13. Lal, Sreeyuth
    et al.
    Moonen, Peter
    Poulikakos, Lily D.
    Partl, Manfred N.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. Swiss Federal Laboratories for Materials Science and Technology, Switzerland.
    Derome, Dominique
    Carmeliet, Jan
    Turbulent airflow above a full-scale macroporous material: Boundary layer characterization and conditional statistical analysis2016In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 74, p. 390-403Article in journal (Refereed)
    Abstract [en]

    Convective drying of macroporous materials is governed by the complex interaction between airflow above and into the material, the roughness of the air material interface and the characteristics of the material pore system. In this study, we experimentally investigate this interplay in detail and at fullscale, using porous asphalt (PA) as a model material. The characteristics of the turbulent flow in the immediate vicinity of the material surface are studied with full-scale wind tunnel experiments at three flow speeds over two types of PA with different surface porosities and surface pore sizes, and are compared to similar measurements over a smooth and impermeable reference material. It is shown that, above a certain wall-normal distance, turbulence profiles can be scaled to make them independent of the flow speed. However, at low speed, the scaling breaks down due to a combination of organized turbulent structures of high intensity and a low turbulence background. No generally valid scaling applicable at all tested air speeds is found close to the surface, where drying occurs. Hence, realistic drying experiments must be performed at full scale and for the entire range of velocities of interest.

  • 14.
    Li, Liangxing
    et al.
    State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University.
    Li, Huixiong
    State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University.
    Chen, Tingkuan
    State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University.
    Experimental investigation on the moving characteristics of molten metal droplets impacting coolant2008In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 32, no 4, p. 962-972Article in journal (Refereed)
    Abstract [en]

    This paper reports the results of an experimental investigation on the moving characteristics of molten metal droplets impacting coolant free surface. A visualization experimental facility of molten fuel coolant interactions (MFCI) is designed and set up in the present study. The lead–bismuth (Pb–Bi) alloys are employed as the metal materials. An automatic control circuit is designed and applied to control the release of the molten droplets. High-speed camera is employed to record the movement of the molten metal droplets falling down and into a coolant pool. Based on the analysis of the experimental data, a so-called “J-region” of the droplet’s velocity–time curves was found and the melt droplet enters the “J-region” when it impacts the free water surface. In the “J-region”, the velocity of the melt droplet decreases rapidly and suddenly at first, and then increases again. The droplet gradually reaches a comparatively steady velocity when it leaves the “J-region”. The present study provides essential information for further study on the fragmentation behavior of high-temperature molten droplets in coolant.

  • 15. Lin, C.
    et al.
    Yu, S. -M
    Wong, W. -Y
    Tzeng, G. -W
    Kao, M. -J
    Yeh, P. -H
    Raikar, R. V.
    Yang, James
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
    Tsai, C. -P
    Velocity characteristics in boundary layer flow caused by solitary wave traveling over horizontal bottom2016In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 76, p. 238-252Article in journal (Refereed)
    Abstract [en]

    The characteristics of horizontal velocity in the bottom boundary-layer flow induced by a solitary wave propagating over a horizontal bottom are presented experimentally, using high-speed particle image velocimetry (HSPIV). The ratio of wave height to water depth varies from 0.096 to 0.386 and the flow inside the boundary layer is laminar. The results show that the horizontal velocity profiles can be mainly classified into two categories with respect to the passing of the solitary wave-crest at the measuring section: the pre-passing (or acceleration) phases under favorable pressure gradient and post-passing (or deceleration) phases under adverse pressure gradient. For the velocity distributions obtained during the pre-passing phases, a nonlinear regression analysis was used to precisely determine the time-dependent characteristic length and velocity scales underlying these profiles. A similarity profile of the horizontal velocity is established first using the time-dependent free-stream velocity and boundary layer thickness as the characteristic velocity and length scales, respectively. In addition, the displacement thickness, the momentum thickness, and the energy thickness are also considered as alternative length scales. All these four representative thicknesses are closely related to each other, demonstrating that any one amongst them can be regarded as the characteristic length scale. The forms of similarity profiles for the non-dimensional velocity distributions are somewhat analogous to the results of steady boundary layer flow over a thin plate under with pressure gradient, but with different coefficients or powers. While during the post-passing phases, flow reversal which acts like an unsteady wall jet and moves in the opposite direction against the wave propagation occurs after the passage of solitary wave-crest. The thickness of flow reversal layer increases with time. A similarity profile is proposed for the velocity distributions corresponding to occurrence of the extreme value in the maximum negative velocity of flow reversal. Variations of the maximum negative velocity and the thickness of flow reversal with the time right after the start of flow reversal are also discussed in detail. Moreover, the non-dimensional time leads of the horizontal velocities at different heights in the boundary layer over the free-stream velocity are evidenced to be more noticeable toward the bottom, and also in lower ratio of wave height to water depth. A similarity profile for the non-dimensional time lead versus the non-dimensional height above the bottom surface is also presented.

  • 16.
    Lundström, Hans
    et al.
    KTH Research School University of Gävle, Department of Indoor Environment.
    Sandberg, Mats
    KTH Research School University of Gävle, Department of Indoor Environment.
    Mosfegh, Bahram
    Temperature dependence of convective heat transfer from fine wires in air: A comprehensive experimental investigation with application to temperature compensation in hot-wire anemometry2007In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 32, no 2, p. 649-657Article in journal (Refereed)
    Abstract [en]

    Heat transfer from a fine wire to air has been experimentally investigated. High accuracy measurements, where both the air temperature and wire temperature have been varied systematically and independently have made it possible to map the behavior of the heat transfer process for different velocities, air temperatures, and wire temperatures. Based on these results a compensation method is proposed which makes it possible to temperature compensate hot wires of large aspect ratio and at low Reynolds numbers for anemometry measurements with velocity calibration only at one air temperature.

  • 17.
    Mallor, Fermin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Raiola, M.
    Sanmiguel Vila, C.
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Discetti, S.
    Ianiro, A.
    Modal decomposition of flow fields and convective heat transfer maps: An application to wall-proximity square ribs2019In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, p. 517-527Article in journal (Refereed)
    Abstract [en]

    In this work the modal decomposition of convective heat transfer distributions in turbulent flows is explored. The organization and thermal footprint of the turbulent flow features generated downstream of wall-proximity two-dimensional square ribs immersed in a turbulent boundary layer are investigated experimentally. This study employs modal decomposition to investigate whether this analysis can allow identifying which characteristics of the flow topology are responsible for the Nusselt-number augmentation, aiming to uncover the underlying physics of heat-transfer enhancement. Heat transfer and flow velocity measurements are performed at a Reynolds number (based on the free-stream velocity and rib side-length) equal to 4600. Square ribs are tested for two different gap spacings from the wall (0.25 and 0.5 ribs side-length) and in wall-attached configuration. A low-thermal-inertia heat transfer sensor coupled with high-repetition-rate Infrared (IR) thermography is designed to study the unsteady variation of the convective heat-transfer coefficient downstream of the obstacles. Flow-field measurements are performed with non-time-resolved Particle Image Velocimetry (PIV). A modal analysis with Proper Orthogonal Decomposition (POD) is applied to both convective heat-transfer maps and velocity-fields. The comparison of the Nusselt-number spatial modes of the clean turbulent boundary layer configuration and of the configurations with the ribs shows a variation of the spatial pattern associated with oscillations with strong spanwise coherence, opposed to the thin elongated streaks which dominate the convective heat transfer in the clean turbulent boundary layer. In configurations where the convective heat transfer is enhanced by coherent structures located close to the wall, similar eigenspectra are observed for both flow field and convective heat transfer modes. The results of the modal analysis support a picture of a direct relation between the coherence of near-wall flow features and heat-transfer augmentation, providing a statistical evidence for the fact that near-wall coherent eddies are extremely efficient in enhancing heat transfer.

  • 18.
    Maqbool, Muhammad Hamayun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Experimental investigation of dryout of propane in uniformly heated single vertical mini-channels2012In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 37, p. 121-129Article in journal (Refereed)
    Abstract [en]

    This article presents dryout results of propane in single vertical circular minichannels made of stainless steel with internal diameters of 1.70 mm and 1.224 mm. The heat flux is increased in steps up to occurrence of dryout. The effects of different parameters such as mass flux, saturation temperature, vapour quality and internal diameter on the dryout are investigated. The results show that the dryout heat flux increases with the increase in mass velocity, with the decrease of vapour quality and with the increase of internal diameter. Almost no effect of saturation temperature on dryout heat flux is observed. Generalised CHF correlations developed for macro and micro scale from the literature are also compared with the experimental results.

  • 19.
    Maqbool, Muhammad Hamayun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Investigation of two phase heat transfer and pressure drop of propane in a vertical circular minichannel2013In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 46, p. 120-130Article in journal (Refereed)
    Abstract [en]

    This article reports the flow boiling heat transfer and pressure drop results of propane in a vertical circular stainless steel minichannel having an internal diameter of 1.70 mm and a heated length of 245 mm. Two phase heat transfer and pressure drop experiments have been performed at saturation temperatures of 23, 33 and 43 degrees C. Heat flux is varied from 5 to 280 kW/m(2) and mass flux is varied from 100 to 500 kg/m(2) s. The results show that the two phase frictional pressure drops, as expected, are increased with the increase of mass flux, vapour qualities and with the decrease of saturation temperature. The heat transfer coefficients are showed to increase with the increase of heat flux and saturation temperature while the influence of mass flux and vapour quality is observed as insignificant. After incipience of dryout, the decrease in heat transfer coefficient and also the two phase frictional pressure drop, especially at higher mass fluxes, is observed. The two phase frictional pressure drop correlations of Muller-Steinhagen and Heck and Friedel and two phase flow heat transfer correlations of Cooper and Liu and Winterton well predicted the experimental results.

  • 20. Martinez-Galvan, Eduardo
    et al.
    Anton, Raul
    Carlos Ramos, Juan
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Influence of surface roughness on a spray cooling system with R134a. Part I: Heat transfer measurements2013In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 46, p. 183-190Article in journal (Refereed)
    Abstract [en]

    Experimental measurements in a spray cooling test rig were carried out for two different heater surface roughnesses and for two different types of nozzles with the dielectric refrigerant R134a. In this paper, results of the heat transfer measurements are presented. The analysis of the results explains the influence of the volumetric flow rate, the surface roughness and the type of nozzle (through the spray parameters) on the spray cooling boiling curve, on the Nusselt number and on the efficiency. It has been found that the effect of a smooth roughness is to delay the onset of the nucleate boiling, but once this regime has started, boiling is so fast that the CHF (Critical Heat Flux) is reached at lower heater temperatures and lower heat fluxes. In a companion paper the sprayed refrigerant film thickness measurements and its relation with the heat transfer measurements are presented.

  • 21. Martinez-Galván, Eduardo
    et al.
    Carlos Ramos, Juan
    Anton, Raul
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Influence of surface roughness on a spray cooling system with R134a. Part II: Film thickness measurements2013In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 48, p. 73-80Article in journal (Refereed)
    Abstract [en]

    Experimental measurements in a spray cooling test rig were carried out for two different heater surface roughnesses and for two different types of nozzles with the dielectric refrigerant R134a. In this paper, results of the sprayed refrigerant film thickness measurements are presented. The influence of the volumetric flow rate, the surface roughness and the type of nozzle (through the spray parameters) on the total average film thickness is analyzed and discussed. In a companion paper, results of the heat transfer measurements are presented. It has been found that there is a relation between the variations of the average Nusselt number and of the film thickness along the spray cooling boiling curve. The heat transfer regimes along that curve are related not only to a variation in the average Nusselt number but also to changes in the film thickness. The qualitative analysis of those variations served to better understand the heat transfer mechanisms occurring during the spray cooling.

  • 22. Martínez-Galván, E.
    et al.
    Antón, R.
    Ramos, J. C.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Effect of the spray cone angle in the spray cooling with R134a2013In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 50, p. 127-138Article in journal (Refereed)
    Abstract [en]

    Spray cooling experiments were performed to study the effect of the spray cone angle on heat transfer and film thickness. The experiments were carried out for three different types of nozzles. Results for heat transfer and film thickness for different flow rates are presented working with the dielectric refrigerant R134a and on a heater with low surface roughness. The behavior of the heat transfer with respect to the spray cone angle shows that as the spray cone angle decreases, there is a delay in the onset of the nucleated boiling regime. As a result, thermal performance worsens as the spray cone angle decreases. On the other hand, in the nucleate boiling regime film thickness increases as the spray cone angle decreases. The qualitative analysis of these variations serves to better understand the heat transfer mechanisms that occur during the spray cooling technique.

  • 23. Mei, Y.
    et al.
    Gong, Shengjie
    KTH. School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
    Gu, H.
    Ma, Weimin
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    A study on steam-water two phase flow distribution in a rectangular channel with different channel orientations2018In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 99, p. 219-232Article in journal (Refereed)
    Abstract [en]

    Experimental study on steam-water two phase vertical and inclined upward flow (15–90°) was performed in a rectangular channel with cross section of 17 mm × 10 mm under atmospheric pressure to investigate the phase distribution and the average void fraction in the cross section which were obtained from the local void fraction measurement by a conductivity probe. The inlet superficial velocities of the steam and water varied from 0.72 to 3.85 m/s and from 0.11 to 0.3 m/s respectively. A high speed camera was used to identify the flow patterns. Experimental results show that the phase distribution curves are significantly affected by channel orientation and the average void fraction first decreases and then increases with the increase of orientation. Based on the drift-flux model, two parameters, namely, the distribution parameter (C0) and the drift velocity (Ugm) have been studied in detail. Both the distribution parameter and the drift velocity are found to be functions of orientation. The distribution parameter decreases with the increase of orientation while the drift velocity first increases and then decreases with the increase of orientation., Based on the experimental data, an improved drift-flux model is proposed especially for the slug and churn flow, which predicts the void fraction in an inclined channel with good accuracy.

  • 24.
    Morteza, Ghanbarpourgeravi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Nader, Nikkam
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Khodabandeh, Rahmatollah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Toprak, Mohammet S
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Muhammed, Mamoun Ali
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Thermal performance of screen mesh heat pipe with Al2O3 nanofluid2015In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 66, p. 213-220Article in journal (Refereed)
    Abstract [en]

    This study presents the effect of Al2O3 nanofluid (NF) on thermal performance of screen mesh heat pipe in cooling applications. Three cylindrical copper heat pipes of 200 mm length and 6.35 mm outer diameter containing two layers of screen mesh were fabricated and tested with distilled water and water based Al2O3 NF with mass concentrations of 5% and 10% as working fluids. To study the effect of NF on the heat pipes thermal performance, the heat input is increased and then decreased consecutively and the heat pipes surface temperatures are measured at steady state conditions. Results show that using 5 wt.% of Al2O3 NF improves the thermal performance of the heat pipe for increasing and decreasing heat fluxes compared with distilled water, while utilizing 10 wt.% of Al2O3 NF deteriorates the heat pipe thermal performance. For heat pipe with 5 wt.% Al2O3 NF the reduction in thermal resistance of the heat pipe is found to be between 6% and 24% for increasing and between 20% and 55% for decreasing heat fluxes, while the thermal resistance increased between 187% and 206% for increasing and between 155% and 175% for decreasing steps in heat pipe with 10 wt.% of Al2O3 NF.

  • 25.
    Owhaib, Wahib Suleiman
    et al.
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Experimental investigation of single-phase convective heat transfer in circular microchannels2004In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 28, no 2-3, p. 105-110Article in journal (Refereed)
    Abstract [en]

    In this study, the heat transfer characteristics of single-phase forced convection of R134a through single circular micro-channels with 1.7, 1.2, and 0.8 mm. as inner diameters were investigated experimentally. The results were compared both to correlations for the heat transfer in macroscale channels and to correlations suggested for microscale geometries. The results show good agreement between the classical correlations and the experimentally measured data in the turbulent region. Contrary, none of the suggested correlations for microchannels, agreed with the test data. In the laminar regime, the heat transfer coefficients were almost identical for all three diameters.

  • 26.
    Owhaib, Wahib Suleiman
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Martín-Callizo, Claudi
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Flow boiling visualization in a vertical circular minichannel at high vapor quality2006In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 30, no 8, p. 755-763Article in journal (Refereed)
    Abstract [en]

    This paper reports on an experimental study of saturated flow boiling of R134a inside a circular vertical quartz tube coated with a transparent heater. The inner diameter of the tube was 1.33 mm and the heated length 235.5 mm. The flow pattern at high vapor qualities and the dryout of the liquid film were studied using a high speed CCD camera at the mass fluxes 47.4 and 124.4 kg/m(2) s in up flow at 6.425 bar. The heat fluxes ranged from 5 to 13.6 kW/m(2) for the lower mass flux and from 20 to 32.4 kW/m(2) for the higher mass flux.

    The behavior of the flow close to dryout was found to be different at low and high mass flux. At low mass flux the location of the liquid front fluctuated with waves passing high up in the tube. In between the waves, a thin film was formed, slowly evaporating without breaking up.

    At high mass flux the location of the liquid front was more stable. In this case the liquid film was seen to break up into liquid streams and dry zones on the tube wall.

  • 27.
    Park, Hyun Sun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Hansson, Roberta Concilio
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Sehgal, Balraj
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Fine fragmentation of molten droplet in highly subcooled water due to vapor explosion observed by X-ray radiography2005In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 29, no 3, p. 351-361Article in journal (Refereed)
    Abstract [en]

    Experimental investigation of the fine fragmentation process during vapor explosion was conducted in a single drop system employing continuous high-speed X-ray radiography and photography. A molten tine drop of 0.7 g at 1000 degreesC was dropped into a water pool, at highly subcooled temperatures of about 20 degreesC, and the explosion was triggered by an external shock pulse of about 1 MPa. X-ray radiographs show that a shell of finely fragmented melt particles accelerates to the vapor bubble boundary during the period of vapor bubble expansion in the explosion process. For tests with highly subcooled coolant, a local explosion due to an external trigger pulse resulted in the stratified explosion along the melt surface. An analysis to estimate mixing depth during the stratified explosion indicated that about 20% of droplet mass was fragmented due to the stratified explosion with a 1 MPa trigger pulse. Finely particles generated during the vapor explosion process were quantified from high-speed X-ray radiography images.

  • 28. Theofanous, T. G.
    et al.
    Dinh, Truc-Nam
    Tu, J. P.
    Dinh, A. T.
    The boiling crisis phenomenon - Part II: dryout dynamics and burnout2002In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 26, no 6-7, p. 793-810Article in journal (Refereed)
    Abstract [en]

    This is Part II of a two-part paper on the boiling crisis phenomenon. Here we report on burnout experiments conducted on fresh and aged heaters in pool boiling. Critical heat fluxes (CHFs) were found to vary from 50% to 140% of the hydrodynamic limit, previously thought to exist at well-wetting conditions. The burnout events were captured in action (for the first time), using highspeed, high-resolution infrared thermometry. Based on these observations and in conjunction with the levels of CHF reached, we are led to conclude that the phenomenon cannot be (macro)hydrodynamically limited, at east at normal pressure and gravity conditions. Based on infrared thermometry, and aided by X-ray radiography data on void fraction, the case for a scale separation phenomenon in high heat flux pool boiling is argued. This indicates that boiling crisis is controlled by the microhydrodynamics and rupture of an extended liquid microlayer, sitting and vaporizing autonomously on the heater surface. Further. the detailed dynamics of this microlayer, as revealed by our experiments. demonstrates that all previous thermally based models of boiling crisis are inappropriate.

  • 29. Theofanous, T. G.
    et al.
    Tu, J. P.
    Dinh, A. T.
    Dinh, Truc-Nam
    The boiling crisis phenomenon - Part I: nucleation and nucleate boiling heat transfer2002In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 26, no 6-7, p. 775-792Article in journal (Refereed)
    Abstract [en]

    This paper (Part I) and the companion paper (Part II, Exp. Therm. Fluid. Sci. 26 (6-7) (2002) 793- 810) present results of an experimental study on nucleate pool boiling. The experiments were conducted under highly-controlled conditions, using electrically heated, vapor-deposited sub-micron metallic films. A high-speed. high-resolution infrared camera was used to visualize dynamic thermal patterns on the heater's surface over a broad range of heat fluxes, starting from the onset of nucleation and up to boiling crisis. Both fresh heaters and aged heaters were experimented with. The heaters' surface nanomorphology and chemistry were characterized with atomic force microscopy, scanning electron microscopy, and X-ray diffraction spectroscopy. First-of-a-kind experimental data on nucleation and boiling heat transfer at high heat fluxes are presented, and a stark difference between fresh and aged heaters is revealed. Remarkable are the origin, evolution and dynamics of the heater dryout process (leading to burnout), identified quantitatively and captured in action for the first time.

  • 30. Wang, Ke
    et al.
    Zhang, Youjia
    KTH, School of Engineering Sciences (SCI), Physics.
    Gong, S.
    Bai, B.
    Ma, W.
    Dynamics of a thin liquid film under shearing force and thermal influences2017In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 85, p. 279-286Article in journal (Refereed)
    Abstract [en]

    Study of liquid film dynamics promotes understanding the critical heat flux (CHF) of boiling heat transfer, which occurs as the liquid layers (micro-layer and macro-layer) near the heater wall lose their integrity. Since the measurement at micro-scale is a challenge, and further complicated by the chaotic nature of the boiling process, profound knowledge on the thin liquid film dynamics is not well documented in the existing literature. In the present paper, we employ a confocal optical sensor system to study the dynamics and the integrity of a thin liquid film sheared by the co-flowing air from above and heated from below in a horizontal aluminum channel. The results indicate that the entrainment governs the liquid film thinning process under adiabatic or lower heat flux conditions, whereas the evaporation becomes more pronounced in a higher heat flux system. The detailed evolution of liquid film is discussed. Based on our experimental observations, the critical film thickness of an integral film is related to the condition of the heating surface and the heat flux. For a specific surface, the critical film thickness remains constant under a defined heat flux and increases with the increasing heat flux. A spectrum analysis is also implemented to analyze the film instability. It is concluded that the heat flux is the dominant factor to govern the film instability compared with the effect of differential velocities of gas and liquid flow.

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