Bubble Dynamic Parameters Research Articles

Unveiling the underlying physics of two-phase boiling heat transfer enhancement through shearing of coalescing bubbles

The upcoming energy scarcity problem has driven research toward developing energy-efficient two-phase heat exchangers essential for various cooling applications. This research is rooted in the principles of pool boiling, essential for effective heat transfer in various heat exchangers. A well-known reported problem in heat exchangers is the dry-out phenomena of heated surfaces due to bubble coalescence. To tackle this undesirable problem, an innovative technique has been introduced in this study, which involves the shearing of bubbles through liquid jet impingement over the heated surface. The study has been carried out in a two-dimensional domain numerically, in the wall superheat range of 9–16 K. To study the underlying physics involved in this pool boiling phenomenon, the bubble dynamics parameters such as departure frequency, bubble diameter, cold spot (bubble base) temperature, and vapor volume fraction have been analyzed. The results show that with the jet shearing effect, a maximum enhancement of 25% in heat transfer rate is observed at higher wall superheat. The investigation also highlights that the liquid jet enhances vapor volume fraction, indicating enhanced steam generation, particularly an enhancement of 27% observed at elevated wall superheat. An early onset necking effect is also observed with the shearing effect, which leads to the formation of smaller bubbles with higher departure frequencies. This study is a benchmark to the fundamental physics of enhancing two-phase heat transfer through bubble shearing, offering promising insights for energy conservation in two-phase heat exchanger design, particularly within the context of pool boiling.

Transient instability characteristics of fluid film bearings induced by bubble inclusion

Bubble inclusion in the tribo-pair leads to two-phase fluid lubrication. Upon the initial introduction of air bubbles to the tribo-pair, it can lead to instability in the operational state. A numerical model is formulated by coupling the fluid Reynolds equation, bubble dynamics equation, and rotor dynamics equation. Various parameters, such as hydrodynamic pressure, fluid carrying capacity, rotor trajectory, and equilibrium position, are employed to characterize the impact of operational and fluid interface parameters on the bubble entrainment process. The findings reveal that the hydrodynamic pressure plays a crucial role in establishing the correlation between velocity and fluctuations in kinetic parameters. Surface tension predominantly influences bubbles within the dispersion region, while surface dilatational viscosity affects the entire domain. Lower surface dilatational viscosity or neglecting surface tension can trigger larger fluctuations in the rotor trajectory. Changes in liquid-phase viscosity result in fluctuations in bubble behavior and dynamics parameters, influenced by the equilibrium position and the effect of hydrodynamic pressure. Higher initial gas-phase volume fractions lead to a more pronounced reduction in fluid-carrying capacity and increased system instability.

Experimental investigation on bubble dynamic behaviors in pool boiling of surfactant solutions

In this study, pool boiling experiments on copper surfaces with different roughness levels (Ra = 0.61 μm and Ra = 0.15 μm) using sodium dodecyl sulfate (SDS) solutions at various concentrations (0.1 CMC, 1 CMC, 5 CMC, and 10 CMC) are investigated. Our study focuses on the impact of SDS concentration, wall superheat, surface roughness, and bubble behavior on boiling heat transfer. The results show that an increase in SDS concentration could improve the heat transfer. However, when the SDS concentration reaches 10 CMC, there is a deterioration in heat transfer. Additionally, rough surfaces show better heat transfer performance compared to smooth surfaces. The presence of surfactant not only promotes bubble nucleation but also reduces the bubble departure diameter and inhibits bubble coalescence. Multiple bubbles are formed from the same nucleation site in surfactant solutions with high concentrations (5 CMC, 10 CMC). Various bubble dynamic parameters, including instantaneous size, departure diameter, growth time, waiting time, and departure frequency are obtained and compared with existing empirical correlations in the literature. It is found that the bubble growth in both deionized water (DI water) and surfactant solutions is mainly influenced by the near-wall thermal conditions, aligning with the thermal diffusion mechanism. In addition, the bubble departure diameters in both DI water and surfactant solutions gradually increase with increasing Jakob number (Ja). The growth time and waiting time in the surfactant solution both decrease with increasing Ja number, leading to a significant rise in the departure frequency. In contrast, the bubble growth time in DI water increased and the waiting time decreased with increasing Ja number, resulting in a relatively stable departure frequency. A new empirical formula is proposed for fDd0.5 based on the surface tension coefficient, surface roughness, and Ja number, which demonstrates good rationality.

An Improved Heat Flux Partitioning Model of Nucleate Boiling Under Saturated Pool Boiling Condition

Abstract An improved heat flux partitioning model of pool boiling is proposed in this study to predict the material-conjugated pool boiling curve. The fundamental rationale behind the improved model is that the heat convection is only governed by far-field mechanisms while the heat quenching and evaporation are partially subjected to near-field material-dependent mechanisms. The quenching heat flux is derived dependently on thermal-effusivities of solid and liquid respectively based on the transient heat conduction analyses. The evaporative heat flux correlates the material-dependent bubble dynamics parameters including bubble departure frequency and nucleation site density together to yield a new analytical form and support the theoretical reflections of material-conjugated boiling behaviors. The proposed model can approximately capture the material-related impacts on boiling heat transfer coefficients and simulate pool boiling curves validated by the use of experimental results.

Experimental investigation of flow orientation effects on cryogenic flow boiling

Cryogenic flow boiling physics is of paramount importance for future cryogenic space applications employing Cryogenic Fluid Management (CFM) technologies. This experimental study investigates the two-phase flow and heat transfer performance of LN2 flow boiling across five distinct flow orientations: vertical upflow, vertical downflow, horizontal flow, 45° inclined upflow, and 45° inclined downflow. The study employed the steady-state heating method within a circular heated tube featuring an 8.5-mm inner diameter and a 680-mm heated length. High-speed video recordings were utilized to capture two-phase flow patterns and interfacial behaviors across various flow orientations. The experiments covered a wide range of operating conditions, including mass velocities ranging from 351.80 to 1572.77 kg/m²s and inlet pressures from 297.14 to 1032.97 kPa, primarily with near-saturated inlet subcooling. Distinct two-phase flow patterns and regime transitions were identified for each flow orientation. Symmetrical flow patterns were evident in vertical orientations, whereas non-vertical orientations exhibited asymmetric flow stratifications, primarily influenced by the buoyancy force in a terrestrial gravity environment. Bubble dynamic parameters were quantified, and bubble collision and dispersion phenomena were visualized. Analyzing heat transfer performance based on local flow boiling curves and variations in heat transfer coefficients (HTCs), it was observed that vertical upflow demonstrated the most enhanced heat transfer performance, while vertical downflow exhibited the lowest. As mass velocity exceeded 830 kg/m²s, the differences in heat transfer among orientations became less distinct, emphasizing the role of flow inertia in mitigating the influence of flow orientation. A direct comparison of microgravity HTC data from a recent study by the authors against the 1-ge HTC data indicated enhanced heat transfer performance in microgravity for flow orientation configurations in terrestrial gravity. However, this enhancement progressively diminished as the heat flux increased. Distinct HTC trends were observed as mass velocity increased for different flow orientations and gravity levels.

An efficient method for processing high-speed infrared images of nucleate boiling on thin heaters at low heat flux

In recent years, there have been many studies on boiling with high-speed infrared cameras. The infrared image contains not only the information of temperature field, but also the information of bubble dynamics. The identification of different heat transfer modes is fundamental to the identification of bubbles. Although many studies have proposed their own methods, they differ greatly from each other and require laborious and time-consuming manual trial and error processes. The research community is in dire need of an efficient method for infrared image processing. This article proposes a self-adaptive method based on statistics to identify different heat transfer modes and nucleation sites which can be executed by computer automatically and rapidly. A series of pool nucleate boiling experiments using thin titanium foil heaters are carried out, and the temperature and heat flux distributions are analyzed. Based on distinguishing outliers from heat flux data, this method can identify different heat transfer modes (evaporation, convection and transient conduction), and then nucleation sites and bubble dynamics parameters. The experimental data and other open-access data from literatures are used to for validation. A number of evaluation parameters are considered and relatively satisfactory performance are achieved.

Coupled bubble dynamics and interaction mechanisms of adjacently nucleated vapor bubbles under subcooled pool boiling regime

The present work investigates the plausible modes of interaction between two adjacently located vapor bubbles growing on high wettability surface during subcooled nucleate pool boiling. The study becomes important as the phenomenon of bubble interaction has a significant impact on the resulting bubble dynamic parameters as well as on microlayer dynamics of the respective vapor bubbles. As against the symmetric growth of microlayer in the case of isolated pool boiling, microlayers of mutually interacting vapor bubbles no longer remain symmetric and tend to deplete relatively faster, thereby influencing the resulting wall heat transfer rates. Toward this, the microlayers and dynamics of adjacently located interacting vapor bubbles have been mapped in a simultaneous manner using thin-film interferometry and high-speed rainbow schlieren deflectometry as a function of varying subcooling levels. Results of the experiments revealed that parameters such as non-dimensional spacing between the two vapor bubbles, supplied heat flux, and degree of subcooling have a strong impact on the mechanism of bubbles' interaction, which, in turn, influence the bubble departure frequency, bubble diameter, and microlayer dynamics. Three dominant modes of bubble interaction, hydrodynamic interaction (HI), thermal interaction (TI), and coalescence (C), were identified as a function of the level of subcooling. Quantification of the experimental data showed that the equivalent diameter of the vapor bubble increases with an increase in the level of heat flux, while it decreases with an increase in the subcooling level. Additionally, the secondary nucleation affects the liftoff time and movement of the primary bubble and can hydrodynamically deplete the microlayer of the first bubble even when the bubbles are far apart, with the depletion rates showing a strong dependence on the growth rate and location of the secondary nucleation.

Review on bubble dynamic of subcooled flow boiling-part b: Behavior and models

Subcooled flow boiling is extensively applied in engineering systems and greatly improves efficiency owing to bubbles' existence and associated heat exchange enhancement. However, accidents may occur as a result of the lack of understanding and control over subcooled flow boiling, which may lead to unnecessary losses. In this respect, bubble dynamic of subcooled flow boiling disposes of an important research significance, which pushes further the understanding of the boiling mechanism. The purpose of this review is to discuss bubble dynamic involved in subcooled flow boiling and summarize current research status on the so-far-utilized models and applications in this field. In this respect, this review discussed the bubble behavior of a bubble life cycle briefly, where key bubble dynamic parameters have also been introduced. In addition, bubble growth, departure, and lift-off behavior, as well as influencing factors were discussed. Finally, recent advances in bubble sliding and the application of bubble dynamic in boiling simulation have been presented. This article's content deeply contributes to a further understanding of subcooled flow boiling, and the application of bubble dynamic to realize the heat transfer enhancement, subsequently allowing for gains in system efficiency and safety margins.

Experiments to understand bubble base evaporation mechanisms and heat transfer on nano-coated surfaces of varying wettability under nucleate pool boiling regime

Absolute surface wettability effects on the characteristics of nucleate pool boiling heat transfer under saturated conditions are investigated with water as working fluid. Wettability of the base surface (ITO-coated sapphire) is modified by coating 60 nm thick SiO2 film using different thin film deposition techniques. In this way, two surfaces with modified wettability (30 o and 65 o static contact angles) have the same surface chemistry with negligible variation in surface roughness, while the base surface itself acts as the third surface with 90 o static contact angle. Experiments are conducted for various constant heat flux conditions. Bubble dynamics and temperature distributions of the substrate surface are mapped in-situ using high speed videography and IR thermography, respectively. Pool boiling curves and overall heat transfer coefficient curves, obtained from the recorded IR images, showed that the overall boiling performance increases with enhanced surface wettability. The observed enhancement has been explained on the basis of the modified bubble dynamics and the associated bubble base evaporation mechanism. The bubble dynamics parameters such as bubble departure diameter and departure frequency, and nucleation site density (NSD) were found to get altered so as to augment the total evaporative heat flux with increasing surface wettability. The heat transfer coefficients and heat transfer rates corresponding to bubble base evaporation for isolated vapor bubble revealed that higher wettability surfaces outperform the surfaces with lower wettability in heat transport through bubble base evaporation. The corresponding underlying mechanisms have been identified. In addition, it was found that the microlayer evaporation mechanism is more efficient as compared to that based on pure contact line evaporation in transporting the heat away from the surface.

Experimental investigation and new correlation for the bubble departure diameter of methane and ethane binary mixtures during nucleate pool boiling

Methane and ethane are the main components of liquefied natural gas (LNG) and mixed-refrigerant liquefaction cycles. The pool boiling characteristics and bubble dynamic parameters of methane/ethane mixtures are important for the design and optimization of LNG systems. In this study, visual experiments were carried out to investigate the pool boiling of methane, ethane and their mixtures on a horizontal flat surface. Heat transfer characteristics and bubble departure diameters were acquired at 0.3 MPa for different concentrations of the mixtures. The bubble departure diameter increases with the increase in superheat temperature and dimensionless Jacob number for all concentrations of the mixture. The non-linear variation with concentrations of the bubble departure diameter can be observed due to the effects of mixtures. The bubble departure diameters for mixtures were predicted by twelve existing correlations, with Cole's correlation having the lowest mean absolute relative deviation (MARD) of 46.28%, with only 38.78% points within ±30% deviation. Therefore, a new model for mixtures was developed based on force equilibrium analysis in this study. Marangoni force is taken into account in the proposed model, as well as the effects of mass transfer on the bubble growth rate in mixtures. The MARD of the new model is 18.78%, which is better than all the twelve existing correlations.

Experimental investigation on the steam condensation dynamic characteristics at low steam mass flux

An experimental study has been performed to investigate the dynamic characteristics of steam direct contact condensation at low steam mass flux. Visible steam bubble parameters can be identified through the image processing algorithm. The maximum dimensionless diameter of steam bubble is calculated and the analysis model of identifying condensation regime is developed to predict transition boundaries of steam chugging and oscillatory bubble regimes. The pressure oscillation waveforms in pipe and in pool are distinguished. In chugging regime, the pressure pulse wave transforms to continuous wave in pool as water temperature increasing, however, in oscillatory bubble regime, continuous wave becomes pulse wave because of increased bubble pulsation volume. The oscillation frequencies are obtained from four different methods of bubble dynamic parameters, pressure pulse periods, pressure frequency spectrums in pipe and in pool to reveal the oscillation mechanism. The low-frequency component in chugging regime increases with water temperature increasing, while the intermediate-frequency component in chugging regime and the frequency in bubble regime decreases.

Bubble dynamics of R-134a/POE and R-123/MO mixture on enhanced surfaces having pores on sub-tunnels

Structured enhanced surfaces are widely used to promote the nucleate boiling heat transfer in a refrigeration system, where a compressor oil circulates. However, there is a significant lack of understanding of the mechanism or predictive models, especially on the boiling of refrigerant/oil mixtures on enhanced surfaces. In this study, as a building block, the bubble dynamic data as well as the heat transfer coefficients were obtained for the refrigerant/oil mixtures on pored surfaces. The test mixtures included R-134a/polylester (POE) and R-123/mineral oil (MO). The results showed that the oil degraded the size of the departing bubbles. The degradation was more severe for R-123/MO than R-134a/POE, and it increased as the saturation temperature increased. The sequence of degradation among samples generally followed the reverse order to the magnitude of the heat transfer coefficient of the pure refrigerant. Similarly, the oil degraded the frequency. The degradation was, in general, in reverse order to the degradation of the bubble departure diameter. The oil also degraded the nucleation site density. As for the heat transfer coefficient, the degradation was more significant at a higher saturation temperature, and for R-134a/POE than for R-123/MO. The changes of bubble dynamic parameters as well as the thermo-physical properties of the refrigerants were shown to be responsible. A heat transfer prediction model was developed based on the bubble dynamic parameters.

A review on correlations of bubble growth mechanisms and bubble dynamics parameters in nucleate boiling

A review on correlations of bubble growth mechanisms and bubble dynamics parameters in nucleate boiling

Forced Convective Boiling in a Vertical Annular Test Section With Seawater Coolant

Abstract In case of some nuclear reactors, seawater is used as an emergency resource to remove the decay heat from the reactor core. This study aims to improve the understanding of boiling heat transfer with seawater coolants. Under the boiling conditions with seawater, the mass transfer of the dissolved impurities to the heated surface is expected to significantly impact the heat transfer characteristics. The focus of this experimental work is to measure the differences of the heat transfer performance between seawater and tapwater with electrically heated cylindrical section in a vertical annulus. High speed visualization is performed to quantify and characterize the bubble dynamics parameters. The experimental results indicate an enhanced heat transfer coefficient with seawater in the initial transient under saturated boiling followed by an asymptotic reduction to values similar to tapwater. Under subcooled boiling, a consistent reduced heat transfer coefficient was observed in seawater for a range of heat fluxes. The high speed visualization of subcooled boiling showed fewer and smaller bubbles nucleating off the heat transfer surface in seawater indicating a lower evaporative flux as compared to tapwater.

Experimental investigation on the effect of surface characterization of electrodes on the gas bubble dynamics in electrolyte flow and performance of FLA batteries by using PIV

Generation of oxygen and hydrogen bubbles at vicinity of the electrodes FLA battery at SOC 60%. In the flooded lead_acid batteries (FLAB), gas bubbles are initially formed on the surface of the electrodes, which are produced by electrochemical reactions, and then released into the electrolyte. In the present investigation, the effect of surface characterization of electrodes of FLAB on the gas bubble dynamic parameters in the electrolyte flow at different charging/discharging rates (C-rates) are studied utilizing particle image velocimetry (PIV) method. The results show that the capacity of FLAB have a linear behavior due to changes in each of the two parameters of the surface characterization of electrodes and the C-rate. At all State of charges (SOCs) of FLAB cells in different tests, increasing average roughness ( Ra ) and average wavelength of the roughness ( λa ) in the electrode surfaces, results in an increase in average bubble diameter and bubble rising velocity. Nevertheless, a sharp decrease in the void fraction of bubbles within the electrolyte was observed due to the increment in λa and Ra . Also, the effect of the rising movement of gas bubbles within the electrolyte on the average electrolyte velocity pattern in the gap between the electrodes by changing the surface characterization of electrodes are investigated in detail.

Whole Field Measurements to Understand the Role of Varying Depths of Nucleation Site on Vapor Bubble Dynamics and Heat Transfer Rates

Abstract This work studies the possible effects of varying depths of cavity on bubbling features and the associated heat transfer rates in nucleate pool boiling regime. A single vapor bubble has been generated on a substrate with a cylindrical cavity at its center that acts as the nucleation site. Experiments have been conducted for three cavity depths (250, 500, and 1000 μm), while keeping its throat diameter constant at 200 μm. With the bulk fluid maintained under saturated conditions, for each cavity depth, surface superheat level has been varied in the range of ΔTsuperheat = 8, 10 and 12 °C. A gradient-based visualization technique, coupled with a high speed camera, has been employed to simultaneously map the changes in thermal gradients during the formation of the vapor bubble as well as bubble dynamic parameters. The image sequence obtained has been qualitatively and quantitatively analyzed to elucidate the dependence of bubbling features and various heat transfer processes on cavity depth. With an increase in the depth of cavity, the net effect of reduction in the available thermal energy due to the increased convection effects and significant depletion of superheated layer are identified as the dominant heat transfer processes that influence the bubbling features. Furthermore, based on the statistics of bubble departure characteristics, the cavity with higher depth (1000 μm) showed a much stable bubble formation with minimal variation in the bubble departure frequency as compared to the bubbling features from a cavity with smaller depth (250 μm). Evaporative heat transfer process has been identified as the primary cause for increased inconsistency of bubbling features at high superheat conditions for experiments performed for low cavity depths.

On the Development of Correlations for Bubble Liftoff Parameters During Subcooled Nucleate Flow Boiling Using Nonintrusive Dynamic Measurements

Abstract Accurate prediction of bubble dynamic parameters is essential to improve boiling heat transfer models. Considering the complexities and challenges associated with performing a large number of boiling experiments, researchers have realized the importance of experimental correlations for predicting bubble dynamic parameters. In this direction, we report an experimental work concerned with the development of correlations for various bubble liftoff parameters during nucleate flow boiling regime. As a definite advancement, the experimental measurements have been performed in a purely nonintrusive manner, thereby minimizing the errors arising due to the interaction of any external probe with the process under study. The measurement approach makes use of a gradient-based imaging technique to simultaneously map the bubbling features and thermal field around a single vapor bubble generated under subcooled flow boiling conditions. Experiments have been performed in a rectangular channel for a wide range of heat fluxes (q" = 20–50 kW/m2), subcooling level (ΔTsub = 2–9 K), and Reynolds numbers (Re = 600–6000) with water as the working fluid. Results show a strong dependence of bubble liftoff parameters on Reynolds number, subcooling level, and applied heat flux. Based on the experimental measurements, empirical correlations have been developed for various bubble liftoff parameters as a function of Jacob number and Reynolds number. Predictions made through the developed correlations are found to be in good agreement with the measured values as well as with the values reported in the available literature. Of all the bubble parameters, maximum deviation between the predicted and measured values (≈23%) was found to be in bubble release frequency.

Development of non-dimensional two phase heat transfer correlation based on physics of boiling

The present paper discusses a new approach for predicting the nucleate boiling transfer coefficient based on the physics of nucleate boiling at atmospheric pressure under saturated conditions. Therefore, a non-dimensional correlation of the nucleate boiling heat transfer coefficient developed as a function of bubble departure diameter, active nucleation site density, and bubble departure frequency. A non-dimensional correlation using non-dimensional numbers such as Bond number (Bo), Prandtl number (Pr), Capillary number (Ca), and Jakob number (Ja) is proposed to predict nucleate boiling heat transfer coefficient. The Buckingham π-theorem is used to develop these non-dimensional numbers. The developed non-dimensional correlation of the bubble departure diameter (Bo) and frequency (Ca*) found to predict the present and experimental data of other investigator within an error of ±12% and ±15%, respectively. The non-dimensional nucleate boiling heat transfer coefficient (Nu) correlation based on the non-dimensional numbers found to predict own and other experimental data within an error of ±15%. The result shows the interdependency of bubble dynamic parameters to predict the nucleate boiling heat transfer coefficient.

Experiments on pool boiling regimes and bubble departure characteristics of single vapor bubble under subcooled bulk conditions

An experimental study for understanding the effects of subcooling of bulk fluid on the phenomenon of nucleate boiling heat transfer was carried out. The whole field experimental data was recorded in a purely non-intrusive manner using rainbow schlieren deflectometry as the optical diagnostic tool. Boiling experiments were conducted over a range of heat flux conditions (1⩽q′′⩽40 kW/m2) and for varying levels of subcooling (0 K ≤ ΔTsubcooling ≤ 10 K). The recorded images were first been interpreted to understand the effect of subcooling on various regimes of boiling phenomenon, which include convection, isolated nucleate boiling and vertical coalescence of the departing bubbles. Observations on convection regime showed an increasing influence of natural convection heat transfer. Based on the formation of vapor bubble and its departure characteristics, the isolated nucleate boiling regime of the classical boiling curve was further segmented into three sub-regimes namely, stable vapor bubbles, oscillating vapor bubbles and oscillating-departing vapor bubbles. A mechanism explaining the oscillations of vapor bubbles under subcooled condition was proposed that takes into account the relative dominance of condensing apex region and evaporating microlayer region. Various bubble dynamic parameters such as equivalent bubble diameter, departure frequency, aspect ratio and oscillation frequency were determined quantitatively to understand the effect of subcooling on the bubble departure characteristics. Based on the experimental results, an empirical correlation for predicting the bubble departure diameter and evaporative heat flux was developed and proposed.

Performance evaluation of alumina nanofluids and nanoparticles-deposited surface on nucleate pool boiling phenomena

Single bubble-based nucleate boiling phenomena of water and alumina-water nanofluids (0.005 and 0.01 vol% concentrations) have been studied under nucleate pool boiling regime for two different superheat levels. While nanofluids-based boiling experiments have been performed on plain substrate surface, experiments with water have been conducted on plain as well as nanoparticles-deposited surfaces. For developing an understanding of the influence of nanoparticles, simultaneous measurements of bubble dynamic parameters as well as associated thermal gradients field have been made using non-intrusive rainbow schlieren optical technique. A direct comparison of water and nanofluids experiments revealed significant changes in bubble dynamic parameters such as reduction in bubble departure diameter and growth time, increase in departure frequency and wait time for the case of nanofluids. Thermal gradients field showed more spreading out of the superheat layer adjacent to the heater substrate due to the addition of nanoparticles in the bulk liquid. In a subsequent study, surface modification of the heated substrate has been realized in the form of deposition of nanoparticles during nanofluid-based boiling experiments. The nanoparticles that get deposited on the surface during long time boiling experiments lead to surface modifications. The resultant nanoparticle-deposited surface is employed as the heater surface for conducting pool boiling experiments with water. Results of these experiments have been compared with those conducted using plain (smooth) heated substrate. Similar trends have been observed in the bubble dynamic parameters for the experiments with water on nano-deposited surface vis-a-vis nanofluids on plain surface. Heat transfer partitioning study revealed that natural convection component reduces and evaporative heat transfer increases significantly in the presence of nanoparticles. Plausible mechanisms for the observed trends have been investigated and discussed.