Increase In Wall Temperature Research Articles

The Influence of Thrust Chamber Structure Parameters on Regenerative Cooling Effect with Hydrogen Peroxide as Coolant in Liquid Rocket Engines

Liquid rocket engines with hydrogen peroxide and kerosene have the advantages of high density specific impulse, high reliability, and no ignition system. At present, the cooling problem of hydrogen peroxide engines, especially with regenerative cooling, has been little explored. In this study, a realizable k-epsilon turbulence model, discrete phase model, eddy dissipation concept model, and 10-step 10-component reaction mechanism of kerosene with oxygen are used. The increased rib height of the regenerative cooling channel causes the inner wall temperature of the engine increases, the average temperature of the coolant outlet decreases slightly, and the coolant pressure decreases. The overall wall temperature decreases as the rib width of the regenerative cooling channel increases. However, in the nozzle throat area, the wall temperature increases, the average coolant outlet temperature decreases, and the coolant pressure drop increases. A decrease in the inner wall thickness of the regenerative cooling channel results in a significant decrease in the wall temperature and a small increase in the average coolant outlet temperature. These findings contribute to the further development of the engine with hydrogen peroxide and can guide the design of its regenerative cooling process.

Modelling the Thermal Treatment and Expansion of Mineral Microspheres (Perlite) in Electric Furnace Through Computational Fluid Dynamics (CFD): Effect of Process Conditions and Feed Characteristics

ABSTRACT A model-based investigation of the interplay between furnace setup and spatio-temporal evolution of particles’ state variables is also presented. The effect of feed size distribution and processing of ultrafine ore are discussed. The process is controlled primarily by the wall temperature and secondarily the air feeding rate; an increase of furnace wall temperature from 900 to 1200°C reduced the final density to 484, 979, and 1262 kg/m3 for feed size of 150 μm, 250 μm, and 350 μm. Model predictions are in good agreement with the experimental measurements possessing differences below 10% in most cases.

An experimental study on the effects of wall heating on coherent structures in a turbulent boundary layer

An experimental investigation was conducted for a better understanding of the turbulence behavior and the coherent structure in a turbulent boundary layer over a heated plate, which is horizontal facing upwards. To explore the effects of wall temperature on the turbulent boundary layer behavior, the boundary layer flow was observed at four different temperatures between the plate and inlet flow (δT=0, 15, 30, and 50 K), with the momentum Reynolds number of the inlet flow set to Reθ=1196. We show that based on the comparison of turbulent kinetic energy (TKE) distribution between unheated- and heated-wall cases, the wall-heated turbulent boundary layer can be divided into three regions, namely, the near-wall region, the intermediate region, and the outer region. The relationship between the TKE distribution and the coherent structures in each region is explored by comparing the detailed flow-field measurement results for the unheated- and heated-wall cases. In the near-wall region, the decrease in fluid viscosity caused by wall heating has stabilization effects on the turbulent fluctuation. With the increase in wall temperature, the streaky structures display a continuous decrease in their spanwise meandering and an increase in their streamwise coherency. The intermediate region ranges from the logarithmic region to the thermal boundary layer edge. The buoyant force caused by wall heating has a significant effect on the turbulence behavior in this region. Under the influence of buoyant force, the large-scale coherent structures for the wall-heating case were found to contain more kinetic energy and incline away from the wall with a larger angle, which leads to the increased TKE in the intermediate region for the wall-heating case. In the outer region, the occurrence of separated turbulent structures is measurably more common for the wall-heating case. Owing to the shedding of the turbulent structures from the turbulent production source (i.e., large-scale coherent structures originating from the near-wall region), the TKE in the outer region for the wall-heating case is less than that of the unheated case.

EXPERIMENTAL INVESTIGATION OF FLOW BOILING PARAMETERS IN A TRANSVERSE GROOVED HORIZONTAL TUBE: CRITICAL HEAT FLUX, PRESSURE DROP, AND HEAT TRANSFER COEFFICIENT

An experimental investigation was conducted to examine critical heat flux (CHF), boiling pressure drop, and local heat transfer coefficient in a horizontal channel with transverse grooves for flow boiling with R-123. Measurement of the wall temperature of the channel was done using a thermal camera. Five test sections were used for the study. A combination of groove pitch (<i>p</i>) of 18.6 and 11 mm and groove height (<i>e</i>) of 1 mm and 0.55 mm were used for the study. The groove pitch-to-height (<i>p/e</i>) ratios used were 11, 20, 18.6, and 33.8. Experiments were carried out for different heat fluxes in the range from 180 to 1259 kW/m<sup>2</sup>, six different mass fluxes from 180 to 1259 kg/m<sup>2</sup>s, and Reynolds numbers from 5834 to 51770. In the grooved channel compared with the smooth tube, an improvement in heat transfer and CHF with the higher pressure drop was found. The boiling heat transfer coefficient increases with a decrease in (<i>p/e</i>) ratio. The enhancement of heat transfer coefficient and CHF improves with a decrease in (<i>p/e</i>) ratio. The maximum enhancement of CHF for (<i>p/e</i>) ratios of 11, 18.6, 20, and 33.8 is found to be 134%, 87%, 57%, and 53%, respectively. An abrupt increase in test channel wall temperature is an indication of CHF occurring. CHF was observed at the top portion of the grooved channel and was found to be of departure from nucleate boiling type.

Improving the thermophotovoltaic performance of a hydrogen-fueled planar combustor with four-corner inlets via partially inserting porous medium

Micro thermophotovoltaic (TPV) generator is a potentially efficient approach to achieve microscale fuel-to-electricity conversion with high-energy–density, high-efficiency, and small-scale portability, where micro combustor provides the high-temperature continuous combustion process as well as a heat source of thermal radiation. In this study, a hydrogen-fueled planar combustor with four-corner inlets by partially inserting porous medium is proposed and investigated by a three-dimensional numerical model of porous medium combustion with detailed reaction mechanism and local thermal non-equilibrium. The combustor performance with and without partially inserting porous medium under various inlet velocities Vin and equivalence ratios ϕ are compared and analyzed to reveal the inherent strengthening mechanism. Moreover, the effects of various porous parameters on the energy conversion performance are examined: the porosity ɛ, thermal conductivity ks, and porous medium filled volume. The results demonstrate that the inserted porous medium can significantly enhance combustion efficiency, combustor wall temperature and its uniformity, and the largest increase in mean wall temperature reaches 79.7 K at Vin = 9 m/s, resulting in a 35.8 % increase in micro-TPV system efficiency. As ɛ and ks decrease, the combustor energy conversion performance increases while the temperature uniformity decreases. A moderate channel width L = 2.0 mm is good for further improving temperature uniformity and energy conversion efficiency. This study paves the way for the improvement of efficient, practical, and portable microscale generators.

Experimental investigation of heat transfer characteristics of water in a vertically–upward tube under ultra-supercritical pressure and ultrahigh-temperature conditions

Advanced ultra-supercritical (A-USC) steam power generation technology is characterized by main steam conditions of > 700 °C and > 35 MPa, enhanced cycle efficiency, and reduced environmental footprint, and is one of the important development goals of the thermal power plants today. However, scarce studies were conducted on the heat transfer characteristics of supercritical water (SCW) under A-USC operating conditions. An experimental platform to safely measure the heat transfer of SCW flowing in a vertical tube at temperature up to 760 °C and pressure up to 42 MPa was designed and built in this study. Experimental measurements of the heat transfer characteristics of SCW were performed on this platform in a wide range of temperature and pressure, up to a maximum bulk fluid temperature of 750 °C and a maximum pressure of 38 MPa. The effects of pressure, mass flux, and heat flux on the heat transfer characteristics of SCW in the ultrahigh enthalpy region (over 3200 kJ·kg−1) were then analyzed based on the experimental data. Results show that in the ultrahigh enthalpy region, the bulk fluid temperature and wall temperature increase approximately linearly with increasing bulk fluid enthalpy. The heat transfer coefficient decreases gently and then gradually stabilizes in the same range, with values in the range of 4–10 kW·m−2·K−1. In the ultrahigh enthalpy region, increasing the mass flux or decreasing the heat flux will improve the heat transfer performance. And at a pressure of > 35 MPa, increasing the pressure will improve the heat transfer performance moderately. By comparing with experimental data, the Gupta’s correlation has acceptable accuracy in predicting the heat transfer coefficient and inner wall temperature.

Bubble Dynamics and Heat Transfer Characteristics of Flow Boiling in a Single Pentagonal Rib Channel

Abstract Two-phase flow boiling is the preferred method for efficient heat dissipation in electronic equipment, so the bubble dynamics and heat transfer characteristics of flow boiling in a single pentagonal rib channel are numerically analyzed by the volume of fluid (VOF) model. Three typical rib structures are obtained, whose block ratios are 0.4, 0.75, and 0.25, and the corresponding length-diameter ratios are 1.72, 0.59, and 12.70, respectively. The Reynolds number is 14,000 and 28,000. The heat flux is set from 50 to 150 kW/m2. The results show that the starting position of the bubble is at the cone and sides of the rib, and its moving direction is related to the configuration of the rib, the heat flux, and fluid velocity. Additionally, the bubbles are shedding at the corner of the rib, and the short rib does not appear to be the vortex shedding phenomenon. The wall temperature and temperature fluctuation increase with the increase of heat flux and with the decrease of fluid velocity. The heat transfer coefficient decreases with the increase of heat flux and with the decrease of fluid velocity. The short rib channel has a higher heat transfer coefficient, approximately 14% and 50% higher than that of the median and long rib channels, respectively. Compared with the single-phase flow, the main frequency of the lift coefficient increases with the increase of the fluid velocity while decreasing with the increase of heat flux. The main frequency of the median rib without harmonic signal keeps constant, and that for long rib decreases by 38%. The study of the instantaneous characteristics of bubble growth in pentagonal rib channels is instructive to the efficient heat dissipation in electronic equipment.

Numerical analysis of heat transfer between a wall and diesel spray: Effect on ignition characteristics

The heat transfer between the wall and spray has an important effect on the in-cylinder ignition characteristics of the diesel engine, especially during cold start conditions. To better understand the effect of heat transfer between the wall and spray at different wall temperatures on the ignition characteristics, a numerical analysis was conducted with a large-eddy simulation (LES) based on optical experiments. The results show that the spray/wall interaction led to a smaller Sauter mean diameter (SMD) and more small and large droplets compared to the free spray. Furthermore, the total surface area of droplets increases, and heat transfer between droplets and the surrounding hot gas is promoted, which is conducive to the ignition process. On the other hand, when the wall temperature is low, the spray is cooled by the wall during impingement, thus inhibiting ignition. As a result of this competing effect, the air entrainment rate increases with the increase of wall temperature due to the cooling effect weakening and gradually changing to a heating effect. However, when the wall surface temperature increases to a high temperature, the heating effect is suppressed and the local heat transfer coefficient decreases due to the Leidenfrost effect. It is worth emphasizing that the Leidenfrost effect only occurs near the stagnation point in this study, and the heat transfer between the wall and the vapor-phase spray still impacts the ignition process, resulting in a shorter ignition delay time (IDT) as the wall temperature increases. Interestingly, the low-temperature reactions of both the free spray and spray/wall interaction cases started at the same moment, and the transition period from the low-temperature ignition delay time (τ1) to IDT shows a significant difference, indicating that the interaction between the wall and spray primarily affects the heat accumulation of the low-temperature reaction (LTR).

Numerical study of drop spread and rebound on heated surfaces with consideration of high pressure

The impact of a drop on a solid surface has been studied for many years. However, most of the previous numerical simulations were focused on the drop impact on a surface at room temperature and standard atmospheric pressure. This paper presents a numerical study of n-heptane and n-decane drops impacting solid surfaces with the consideration of high temperature and high pressure using smoothed particle hydrodynamics (SPH). The SPH method is validated against experiments from our work and literature. This work is focused on two typical drop-impact regimes, namely, spread and rebound. Different drop impact sequences were simulated at the wall temperature in the range of 27–400 °C and the ambient pressure between 1–20 bars. The difference between the inception of film boiling and liquid saturation temperature was found to decrease with elevating ambient pressure. The spread factor and apex height are investigated for the regime of spread. The results indicate that the lower viscosity fluid has a smaller spread factor as compared to the fluid with higher viscosity. The variation of Leidenfrost temperature with ambient pressure for both n-heptane and n-decane droplets is established numerically and compared with the trend observed in the experiment. The simulation outcomes of drop rebound for high boiling point liquid (n-decane) in the film boiling regime at atmospheric pressure show that with the increasing wall temperature, the drop rebound height and vapor layer height increase. Finally, the effect of ambient pressure on drop rebound height and velocity is investigated. The numerical results indicate that the increase in ambient pressure reduces the droplet rebound velocity and rebound height.

Numerical Investigation of the Thermal Behavior of Cracked RP-3 in Rectangular Cooling Channels under Different Inclinations.

The pyrolysis effect of aviation kerosene is common in the regenerative cooling process of hypersonic aircraft scramjets. To find out the effect of inclination variation on the characteristics of aviation kerosene RP-3 considering thermal cracking in a regenerative cooling rectangular channel, a detailed chemical mechanism of RP-3 pyrolysis is introduced to construct a numerical model. The results indicate that the pyrolytic reaction begins at the junction of the heating wall and the side walls, and the main products of pyrolysis are light olefins and alkanes. The thermal cracking reaction slows down the velocity of the main flow on account of the increased density and increased viscosity resulting from the decrease in RP-3 temperature. With the decrease in inclination, thermal cracking is enhanced and the average heat transfer coefficient is decreased, which leads to an increase in wall temperature.

Effects of wall temperature on separation structures in supersonic flow over a semi-circular cavity

The influence of wall temperature on the vortex structure and flow characteristics of flow in semi-circular cavities is numerically investigated in this paper. The results show that the separation and reattachment points move downstream, and the secondary vortex increases with increases in wall temperature. In the secondary vortex section, normalized wall shear stress in the polar map has good consistency at different wall temperatures, and the flow properties of the three extreme points on the map are similar to Couette flow. In addition, the secondary vortex region can be regarded as an isobaric high-pressure region, while the pressure gradients slowly vary as the wall temperature increases. We confirm the independence of separation pressure for the wall temperature using pressure distribution and find that the peak and inflection points are at the reattachment points and separation points, respectively. Moreover, using a series of numerical calculations of the positions of the vortex center at different wall temperatures, explicit empirical formulas for estimating the positions of the primary vortex center are put forward. Using a topological mapping method, cavity flow is converted into quasi-one-dimensional steady-state compressible viscous flow through a variable cross-section pipe, and the flow parameter distribution, including the Mach number and pressure, conforms to the rule of quasi-one-dimensional flow.

Molecular dynamics study of spontaneous capillary flow and heat transfer in nanochannels

Passive cooling technology has become increasingly used in microelectronic devices, with capillary force being the most commonly used driving method. In this study, the capillary flow and heat transfer mechanisms and characteristics in nanochannels are studied based on molecular dynamics (MD), which have rarely been explored in previous studies. The capillary speed increases as the solid-liquid interaction intensity (εwl) increased, but when the wall is completely wetted, the capillary speed slows slightly an increasing εwl. By introducing wall slip, the Lucas-Washburn (L-W) equation is modified and a better fit is obtained. Furthermore, the effects of εwl, the temperature difference of the solid-liquid and surface nanostructure on capillary flow and heat transfer are analyzed. The increase in εwl and wall temperature enhances the capillary speed and heat transfer, but a continuous increase in the wall temperature will accelerate liquid evaporation and cause climb stagnation. The introduction of nanostructures slows the capillary speed, but can enhance the solid-liquid heat transfer. Finally, the microscopic mechanism of the above findings is analyzed by potential energy and density analyses. The reduction of the liquid potential energy at the solid-liquid interface can accelerate the capillary speed to a certain extent, but when the potential energy is too low, the liquid atoms will gather near the wall surface, blocking the capillary climbing. The expansion of the low potential energy region and the high mass density region enhances the solid-liquid heat transfer.

Numerical study on flow and heat transfer of S−CO2 in inclined tubes under different flow conditions

In this paper, the numerical simulation of supercritical carbon dioxide ( S − CO 2 ) flowing in large diameter inclined circular tubes with different heat flux and inlet temperature is studied. According to the experimental results of S − CO 2 flow in a horizontal tube, the S S T k − ω model was found to be the most accurate predictor of heat transfer. Based on the phase transition temperature of the pseudo-boiling phenomenon under subcritical conditions, a gas-like film radius model was established. The results show that when heat flux is too large, the wall temperature rises quickly, which makes the density gradient in the cross-section, buoyancy and gas-like film radius increase constantly, resulting in the gathering of a large number of low-density and poor heat transfer performances at the top generatrix, causing a sudden increase in wall temperature and the heat transfer coefficient decrease significantly. As the inlet temperature increases, buoyancy and relative secondary flow energy decreases and the fluid temperature rises dramatically, eventually leading to a rapid decrease in thermal conductivity and heat transfer capacity.

Dynamic behaviors of fuel droplets impacting on the wall surfaces with different wettability and temperatures

To improve the controllability of combustion and reduce the emissions of HC and CO of the newly developed combustion modes, such as the HCCI, PCCI and RCCI, the evaporation processes and morphological developments of diesel droplets impacting on the aluminum alloy surfaces with different wettability and temperatures are experimentally investigated. The results show that the oleophilic surface is conducive to evaporation of diesel droplets, while the oleophobic surface promotes the formation of the vapor film between the fuel droplets and the test surface at a high surface temperature and reduces the Leidenfrost temperature of the fuel droplets. Also, stronger oleophobicity of the surface is beneficial to the rebound and secondary breakup of the droplets, thereby promoting the evaporation of the droplets in the gas-phase space of the cylinder and improving the air–fuel mixing. Moreover, the stronger the surface oleophobicity, the smaller the spreading factor and the larger the rebound factor of the droplets. At a higher wall temperature, the ability for enhancing the surface oleophobicity of the convex domes, grooves and protrusions structures on the laser-etched surface is better than that of the boss/pits and needle-like structures on the chemically etched surface. Under the conditions of lower surface temperatures, the evaporation rate of the droplet after hitting the wall is closely related to the spreading area of the droplet. As the wall temperature increases, when the droplet is in transition boiling regime, the large heat transfer rate makes the diffusion width, height and diffusion area of ​​the vapor phase region are obviously large.

A general prediction model of minimum film boiling temperature during quenching propagation in narrow rectangular channel

During quenching, the Leidenfrost effect deteriorates the heat transfer at high temperatures before the arrival of the minimum film boiling point. Accurate prediction of the minimum film boiling temperature (Tmin) is significant in assessing cooling efficiency and providing a reference for optimization design. The experimental investigation on the Tmin is carried out in multi-narrow rectangular channels containing internal and external coolant channels. The effects of initial surface temperature and wall heat flux on Tmin are discussed in detail. The experimental results indicate that Tmin increases with the increase of initial wall temperature and wall heat flux, by an average of 6.5% and 7.7%, respectively. Under high wall temperature and heat flux conditions, the ratio of Tmin to the initial wall temperature at the inlet is much larger and then remains nearly constant with the propagation of the quench. Furthermore, an improved dimensionless prediction model of Tmin is proposed considering the effects of high initial wall temperature and wall heat flux. The comparison results illustrate good agreement with relative errors within ± 15%. Meanwhile, the current model predicts most of the published experimental data with an uncertainty of ± 15%.

Numerical investigations on flashback dynamics of premixed methane-hydrogen-air laminar flames

Injecting hydrogen into the natural gas network to reduce CO2 emissions in the EU residential sector is considered a critical element of the zero CO2 emissions target for 2050. Burning natural gas and hydrogen mixtures has potential risks, the main one being the flame flashback phenomenon that could occur in home appliances using premixed laminar burners. In the present study, two-dimensional transient computations of laminar CH4 + air and CH4 + H2 + air flames are performed with the open-source CFD code OpenFOAM. A finite rate chemistry based solver is used to compute reaction rates and the laminar reacting flow. Starting from a flame stabilized at the rim of a cylindrical tube burner, the inlet bulk velocity of the premixture is gradually reduced to observe flashback. The results of the present work concern the effects of wall temperature and hydrogen addition on the flashback propensity of laminar premixed methane-hydrogen-air flames. Complete sequences of flame dynamics with gradual increases of premixture velocity are investigated. At the flame flashback velocities, strong oscillations at the flame leading edge emerge, causing broken flame symmetry and finally flame flashback. The numerical results reveal that flashback tendency increase with increasing wall temperature and hydrogen addition rate.

Experimental investigation on the thrust regulation of a Mg–CO2 Martian ramjet

Experimental research was conducted to evaluate the thrust regulation feasibility and investigate thrust regulation characteristics of Mg–CO2 Martian ramjet. Before the combustion experiment, a mass flow calibration experiment was carried out to assess the performance of fuel mass flow rate regulation. Moreover, a constant chamber pressure combustion experiment verified the feasibility of the Mg–CO2 ramjet. Then, the tests of thrust regulation performance were carried out in a mainstream temperature of 800 K and a mass flow rate of 100 g/s to obtain the performance of ramjet on different conditions. It was observed that the ramjet achieved stably self-sustaining combustion under different chamber pressure phases, which preliminarily proved that the ramjet has thrust regulation performance. The detailed thrust estimating results showed that the maximum thrust is 76.4 N and the minimum is 50.5 N with a 1.51 thrust regulation ratio. Furthermore, the pressure regulation response is quick, and the thrust regulation ratio is adjustable. A parameter (the regulation sensitivity) for better evaluation of regulation performance was proposed, and the regulation sensitivity is 0.08 MPa/s in this experiment. What's more, the combustion efficiency of magnesium powder in the combustor improved with the progress of adjustable thrust experiment sequence due to the increase in the internal wall temperature of the ramjet, maximum combustion efficiency achieved is 71.6%.

Particle-scale modelling of the pyrolysis of end-of-life solar panel particles in fluidized bed reactors

The end-of-life solar panels can be disassembled through pyrolysis by removing the binder - ethylene vinyl acetate (EVA) for panel recycling, yet its research is still in its early stages. In this study, a reactive discrete element method - computational fluid dynamics (rDEM-CFD) model is developed to study the physical-thermal characteristics of dense gas-solid reacting flow related to the solar panel particles’ pyrolysis in two typical chemical reactors - fixed bed (FB) and bubbling fluidized bed (BFB) reactors. The simulation results show that the overall EVA removal degree in the BFB is higher than that in the FB. Then the two key parameters are studied including wall temperature and superficial gas velocity in the BFB. The results show that the EVA removal degrees are improved considerably, from 91.03%, 94.89%, to 99.99%, as the wall temperature increases from 723 K, 773 K, to 823 K. In contrast, the EVA removal degrees at the superficial gas velocity of 1.25 m/s, 1.5 m/s, and 1.75 m/s are similar, i.e., 94.67%, 94.89%, and 95.45%, respectively. The underlying mechanism is explored: the BFB shows better heat and mass transfer performance than the FB, such as more uniform temperature distribution, higher Re and Nu numbers, and larger heat transfer fluxes; on the other hand, increasing wall temperature decreases the Re and Nu numbers while elevating superficial gas velocity enlarges the Re and Nu numbers in the BFB. The study is useful for pyrolyzer design and optimization for efficient solar panel recycling.

Skin-friction and heat-transfer decompositions in hypersonic transitional and turbulent boundary layers

The decompositions of the skin-friction and heat-transfer coefficients based on the twofold repeated integration in hypersonic transitional and turbulent boundary layers are analysed to give some major reasons of the overshoot phenomena of the wall skin friction and heat transfer. It is shown that the overshoot of the skin-friction coefficient is mainly caused by the drastic change of the mean velocity profiles, especially the strong negative streamwise gradient of the mean streamwise velocity far from the wall; and the overshoot of the heat-transfer coefficient is primarily due to the viscous dissipation, especially the strong positive vertical gradient of the mean streamwise velocity near the wall. These observations are different from the previous observations that the Reynolds shear stress and Reynolds heat flux are the reasons, respectively. Further investigations show that the above observations are independent of the set-up of the wall blowing and suction parameters, which indicates the universality of the major reasons of the overshoot phenomena in our numerical simulations. In the hypersonic turbulent boundary layers, it is observed that the strongly cooled wall temperature and the high Mach number can slightly enhance the contribution of the Reynolds shear stress, and weaken the contribution of the mean convection, mainly due to the strong compressibility effect. Moreover, the magnitudes of the relative contributions of the mean convection, pressure dilatation, viscous dissipation and the Reynolds heat flux increase as the wall temperature increases.

A numerical study of flow boiling in a microchannel using the local front reconstruction method

AbstractThe rapid advances in performance and miniaturization of electronic devices require a cooling technology that can remove the produced heat at a high rate with small temperature variations, as is obtained in flow boiling. To obtain insight in flow boiling, we performed numerical simulations in a 200 μm square microchannel using the local front reconstruction method. Besides validation with literature results, a parametric study shows an increasing heat removal rate and bubble growth rate with increasing wall temperature, liquid mass density, and liquid heat capacity and decreasing inlet velocity indicating the importance of phase change compared to convective transport. Finally, the heat transfer in the liquid film is studied using a Nusselt number defined with the film thickness, which is comparable to Nusselt number for falling films on hot surfaces. It is observed that convective effects are more pronounced at the bubble rear compared to the bubble front.