Heat Transfer Coefficient Research Articles

Comparison of subcooled flow boiling in concentric annuli with bare and finned surfaces

In this study, the hydrodynamic and thermal characteristics of subcooled flow boiling in concentric annuli with inner heating wires, featuring bare and finned surfaces designed for heat transfer enhancement, were experimentally investigate, with a focus on cooling technology for EV charging cables. The bare wire test module consisted of a 300 mm long wire, with a 290 mm long inner heating surface and a diameter of 10 mm. The outer tube was constructed from transparent polycarbonate with a 22 mm diameter, allowing optical access to observe the flow. The finned wire test module has an identical construction, except for the addition of six longitudinally extruded fins with cross-sectional dimensions of 2 × 5 mm2. Experiments and flow visualizations, aided by high speed imaging, were conducted using HFE-7100 as the working fluid at mass velocities, G, 463.7 to 1,309.6 kg/m2s and heat fluxes from 0.90 to 9.93 W/cm2, under inlet pressures between 120 and 240 kPa. The study investigated thermal non-equilibrium phenomena, driven by asymmetric bubble accumulation, and their effects on circumferential temperature distribution, which showed opposing trends between the bare and finned surfaces. An evaluation of previous empirical correlations for predicting subcooled flow boiling heat transfer coefficients was performed, followed by an assessment of fin performance in enhancing heat transfer. A comparative analysis with the bare surface module of the same dimensions confirmed that the longitudinal fins provided superior thermal management, maintaining the surface temperature below the safety threshold, Ts,safe. The longitudinal fins demonstrated a 54.5 % reduction in charging time and a 183.7 % increase in charging current for charging up to 80 % state of charge (SOC) of a 77.4 kWh battery, compared to the bare wire.

Mathematical theory and CFD solutions for internal convective cooling of gas turbine blades highlighting the effects of rotation

A quasi-one-dimensional mathematical theory is developed for determining the effects of rotation on the fluid flow and heat transfer in a cooling channel within a rotating gas turbine blade. The three-dimensional intricacies in the solutions of the same problem are captured through accurate computational fluid dynamic simulations. The derived analytical closed-form solutions predict the amount by which the relative total temperature of the coolant changes as a result of rotation. It is shown that such changes due to rotation are significant proportion of the change of coolant temperature due to heat transfer. The computed spatial evolutions of the primary velocity field, secondary velocity field and the force fields are presented as the coolant progresses from the inlet to the outlet so that the complexities and subtleties are exposed to a high degree of visualizability. Detailed considerations to various components of the centrifugal, Coriolis and pressure forces are given. The flow field is shown to depend strongly on whether the coolant moves in the spanwise outward or inward direction. The three-dimensionality of the flow field is reflected in complex circumferential variations of the blade temperature and the internal heat transfer coefficient. When the effects of the x–component of the Coriolis force interacts non-linearly with the effects of the z–component of the centrifugal force and a drastic x-gradient in fluid density due to a thin thermal boundary layer, then the primary velocity profile may exhibit great complexity, including flow separation. The present paper thus captures the strong, non-linear, two-way coupling between the fluid dynamics and heat transfer in the internal convective cooling occurring in a channel within a rotating gas turbine blade. Based on about 100 three-dimensional computational fluid dynamics simulations, new heat transfer correlations are developed for average Nusselt number for a rotating channel that will be of practical use.

Research on temperature rise performance of DC universal disconnect switch at high altitude

Abstract Low Voltage appliances are used more and more widely in high altitude areas, but the research on their temperature rise performance is still insufficient. Aiming at this problem, a high altitude temperature rise simulation model is established and verified by experiment, and the temperature rise performance is studied. Firstly, a DC universal isolation switch with a rated current of 1600A was used as the carrier to build an electro-thermal coupling calculation model of high-altitude temperature rise. Secondly, the temperature rise experiment of the isolation switch in high altitude environment was carried out to verify the effectiveness of the simulation model. Finally, the temperature fields of the DC universal isolation switch at different altitudes are simulated, and the change of convective heat transfer coefficient is calculated, and the temperature rise performance of the isolation switch at high altitudes is analyzed. With the increase of altitude, the temperature rise of the conductor is significantly higher than that of the insulation shell, and the heat dissipation capacity of the aluminum radiator decreases significantly at high altitude. The model and conclusion can provide reference for the use of low voltage electrical apparatus in high altitude environment.

The effect of heterogeneous geometry on steady-state heat transfer in extrusion-based 3D printed structures

The 3D printed buildings constructed using rapid manufacturing techniques provide opportunities for structural optimization and performance design, which are beneficial in meeting the vision of digital and sustainable development of the construction industry. However, there are still many research gaps in the heat transfer of 3D printed buildings, impacting the accurate design of their thermal performance. This study quantifies the effect of heterogeneous geometry on heat transfer in extrusion-based 3D printed structures. The experiment reveals that the non-uniform surface temperature distribution primarily originates from geometrical factors, with heterogeneous physical properties caused by cold joints having little influence. Numerical simulations using equivalent geometric models indicate that the local temperature and the convective heat transfer coefficient of raised surfaces vary periodically, corresponding to surface shape. As surface bulges increase, the overall average heat transfer efficiency of the 3D printed structure decreases, while total surface heat transfer increases. These findings help to understand the effect of heterogeneous geometric properties on the heat transfer process of 3D printed structures, thus providing a reference for the accurate design of 3D printed structures with thermal functions.

Ultra-stable counter flow diverging minichannel heat sink with integrated microstructures for superior cooling performance

Efficient thermal management of miniaturized electronic devices is quite challenging nowadays. It requires dissipation of very high heat flux without considerable elevation of surface temperature. To address this issue, this study proposes the counter flow diverging minichannel heat sink in a compact size of 3 cm2. Additionally, two innovative microstructures have been developed and integrated into the bottom surface of the proposed minichannel heat sink: one with gradient micro pin-fins and another combining gradient microcavities with micro pin-fins. Comprehensive flow boiling experiments are conducted under various operating conditions to identify the best configuration with the most appropriate operating condition to dissipate the highest heat flux with minimal pressure drop and stable two-phase flow patterns. The current study reveals that the synergistic effects of gradient micro pin-fins and optimized gradient microcavities achieve a very high heat flux of 746.14 W/cm2 and a two-phase heat transfer coefficient of 28.18 W/cm2K under the limitation of wall temperature lower than 132 °C. Additionally, it maintains an exceptionally low pressure drop of 2.35 kPa with stable two-phase flow patterns under a mass flux of 600 kg/m2s and a degree of subcooling of 40 °C. Compared to the bare surface, counter flow diverging minichannels with gradient micro pin-fins and optimized gradient microcavities show excellent enhancements of 201.12 % in the effective heat flux and 124 % in the two-phase heat transfer coefficient, suggesting it is the best design in the present study for advanced cooling applications.

On the prediction and optimization of the flow boiling heat transfer in mini and micro channel heat sinks

The most common methods for predicting flow boiling heat transfer in mini/micro channels-based heat sinks rely on semi-empirical correlations derived from experimental data. However, these correlations are often limited to specific testing conditions. This study proposes a novel approach using deep learning and genetic algorithms (GA) to predict and optimize refrigerants' flow boiling heat transfer coefficients (FBHTC) in mini/microchannels-based heat sinks. The dataset used in this study includes FBHTC observations from the literature for seven refrigerants (R1234yf, R1234ze, R134A, R513A, R410A, R22, and R32). The optimal input parameters identified include hydraulic diameters ranging from 1 to 7 mm, saturation temperature from 0 to 20 °C, flow qualities from 0.006 to 0.972, heat flux from 3 to 78.8 kW/m2, and mass fluxes between 100 and 1200 kg/m2s. Gradient-boost regression trees were employed to develop the deep learning and GA models for accurate estimation and optimization. Correlation analysis and feature engineering selected the most influential parameters to construct a precise and simple model. The results demonstrate that the models could estimate refrigerants' FBHTC with high accuracy, achieving an R2 of 0.988 and a mean squared error (MSE) of 0.05%. The GA-based method effectively optimized the FBHTC for each refrigerant by determining the appropriate input parameters, including the saturation temperature, heat and mass fluxes, quality, and hydraulic diameter. Additionally, a parametric analysis using explainable artificial intelligence was conducted to interpret the impact of each input parameter on the FBHTC.

Influence of Rectangular Micro Inserts and Micro Chambers Heat Transfer Characteristics of Microchannel Heat Exchanger

This decade's smaller gadgets have made heat removal in electronics and microprocessors increasingly crucial necessitating the use of micro channel heat exchangers (MCHEs). The current study investigates the MCHE performance improvement through micro chambers and rectangular inserts with varying orientations (angle of insert: 0˚, 45˚, and 90˚). Experimental and numerical studies are conducted in a laminar environment, with Reynolds number varying from 74 to 446. Simulation of fluid flow and heat transfer is accomplished through Finite Volume Method. Thermal performance indicators, fluid flow parameters, pressure drop, friction factor, are used to evaluate and quantify the efficiency of MCHEs. It is shown that inserting two rectangles at 90° angle can achieve the ideal heat transfer coefficient. As a result, compared to the MCHE-MCDCI with various orientations of 0°, 45°, and 90°, respectively, the increase in Nu is 12.21%, 23.42%, and 37.10%, respectively. The rectangular insert at an angle of 90 in an MCHE caused the highest pressure loss. In contrast with MCHE-MCDCI. The pressure drop at 0˚, 45˚, and 90˚ increases by 13.26%, 37.94%, and 52.70%, respectively. When compared with double cylindrical inserts, MCHEs with rectangular inserts that are orientated at an angle of 90 degrees produced the greatest PEC.

Unsteady numerical calculation of flow boiling heat transfer in microchannels with Kagome structures

A three-dimensional microchannel flow boiling model was developed based on the VOF model and the Lee model, and the flow and heat transfer in microchannels with Kagome structures were numerically simulated. The characteristics of bubble flow patterns, gas phase distribution, and heat transfer were analyzed under the heat fluxes of 5–8 MW/m2 and flow velocities of 0.2–0.5 m/s. The results show that at a flow velocity of 0.5 m/s, the disturbances caused by fluid impact on the Kagome structure result in bubble break-up, effectively suppressing the formation of large bubbles. However, at a flow velocity of 0.2 m/s, bubbles tend to be adhered on the surface of the Kagome structure, causing local blockage and deteriorating heat transfer. Compared to the flow velocity of 0.5 m/s, the average heat transfer coefficient in the microchannel decreases by up to 75.4 % and the pressure loss decreases by 45.38 % at the flow velocity of 0.2 m/s.

The use of pulsating jet impingement to minimize temperature oscillations caused by fluctuating heat-flux boundary conditions

Thermal cycling poses a significant challenge in modern applications employing semiconductor devices such as power electronics, owing to the dynamic heat dissipation encountered across diverse operational conditions. The oscillatory variation between peak and low temperatures can induce thermal fatigue, thereby compromising long-term reliability. To address this issue, an innovative approach involving intermittent pulsation of jets has emerged as a promising solution to mitigate peak temperatures and attenuate temperature fluctuations within acceptable limits. This paper presents a comprehensive numerical investigation into the efficacy of intermittent jet impingement in minimizing temperature fluctuations arising from transient heat-flux boundary conditions across a frequency spectrum ranging from 1 to 25 Hz. Comparative analysis against steady jets reveals that intermittent jet pulsation enables superior control over maximum temperature thresholds. An enhancement factor is introduced to quantitatively assess the effectiveness of intermittent jet pulsation, elucidating that up to 8.2 Hz, the reduction in temperature oscillation is notably enhanced compared to higher frequencies. A reduced model is developed to facilitate estimation of transient heat-transfer coefficients during the off period of the jet, shedding light on the underlying mechanisms driving enhanced heat transfer under intermittent jet conditions due to vorticity rings.

The Impact of 3D Printing Technology on the Improvement of External Wall Thermal Efficiency—An Experimental Study

Three-dimensional printing technology continues to evolve, enabling new applications in manufacturing. Extensive research in the field of biomimetics underscores the significant impact of the internal geometry of building envelopes on their thermal performance. Although 3D printing holds great promise for improving thermal efficiency in construction, its full potential has yet to be realized, and the thermal performance of printed building components remains unexplored. The aim of this paper is to experimentally examine the thermal insulation characteristics of prototype cellular materials created using 3D additive manufacturing technologies (SLS and DLP). This study concentrates on exploring advanced thermal insulation solutions that could enhance the energy efficiency of buildings, cooling systems, appliances, or equipment. To this end, virtual models of sandwich composites with an open-cell foam core modeled after a Kelvin cell were created. They were characterized by a constant porosity of 0.95 and a pore diameter of the inner core of the composites of 6 mm. The independent variables included the different material from which the composites were made, the non-uniform number of layers in the composite (one, two, three, and five layers) and the total thickness of the composite (20, 40, 60, 80, and 100 mm). The impact of three independent parameters defining the prototype composite on its thermal insulation properties was assessed, including the heat flux (q) and the heat transfer coefficient (U). According to the experimental tests, a five-layer composite with a thickness of 100 mm made of soybean oil-based resin obtained the lowest coefficient with a value of U = 0.147 W/m2·K.

SIMULATION HEATING PROCESS FOR WEAKLY REACTIVE COAL IN THE HORIZONTAL REACTOR

In this study results of the active medium parameters influence formed by hot air on the thermal heating process of weakly reactive coal from the formation «Maikubensk 3B» for the extraction of additional heat are represented. In the course of the research the regularities of the hygroscopic moisture and volatile combustible substances release for the obtaining additional heat have been determined. Optimal temperature ranges of the stage heating taking into account thermal destruction of coal in the temperature range from 20 C to 600 C, the main steps of the insulated heating process, the moisture content gradient propagation lines and dependence of the heat transfer and mass transfer coefficients on the temperature and the humidity during the thermal heating process in the horizontal coal heating reactor. The results show that it is possible to release volatile combustible gases with a gradual increase of temperatures in the obtained mode. The heating mode comprises a pre-heating stage with hydroscopic moisture release, in the temperature range from 20 C to 105 C, the stage of isothermal heating in the temperature range from 105 C to 400 C and the phase of flame-free combustion in the temperature range from 400 C to 600 C with the temperature rise above the set value. Process simulation was carried out in the Comsol Multiphisics software environment for the weakly reactive coal real-world heating conditions. Keywords: coal heating, weakly reactive coal, isothermal heating, step-by-step heating, Lagrange method, non-liner equation, non-stationary process.

Numerical Investigation of Thermal Performance Enhancement in a Newly Designed Shell and Tube Heat Exchanger using 〖"TiO" 〗_"2" Nanofluids

This study investigates the use of titanium dioxide (TiO2) nanofluids to enhance the thermal performance of shell and tube heat exchangers. A comparative computational fluid dynamics (CFD) analysis is conducted using water and a 0.5% TiO2 nanofluid. The heat exchanger is modelled using computer-aided design (CAD), with dimensions closely resembling commercial units. The CFD model is validated through a grid-independence study, with a mesh of 4,112,679 elements yielding grid-independent results. The key findings show that the 0.5% TiO2 nanofluid increases the cold fluid outlet temperature by 11.44% compared to water (36.04°C vs. 33.63°C). The average heat transfer coefficient is enhanced by 12.3% when using the nanofluid. The CFD results are consistent with experimental data, with a maximum deviation of 4.2% in the outlet temperatures. This study demonstrates the successful integration of TiO2 nanofluids with an optimized shell and tube heat exchanger design. The novelty lies in the application of nanofluids to improve the thermal performance of industrial heat exchangers. The presented methodology, combining CAD modelling and CFD analysis, provides a foundation for further optimization and experimental validation of nanofluid-enhanced heat transfer systems.

Impacts of slip and activation energy on MHD hybrid nanofluid flow past a stretching radiated surface with heat generation/absorption

The influences of slip and activation energy on the magnetohydrodynamic (MHD) flow of hybrid nanofluid over a permeable stretching radiated surface in attendance of heat source/sink have been studied. Al2O3 and Cu nanoparticles are mixed up in water to produce a hybrid nanofluid which is very important in various industrial sectors as hybrid nanofluid has wider applications in enhancing thermal efficiency to provide efficient and reliable cooling. As no one has yet searched for the collective impacts of radiative heat flux, ‘heat generation/absorption’ and ‘Arrhenius activation energy’ on MHD flow of ‘hybrid nanofluid’ in presence of slip that we are exploring in this article, this identifies the novelty of our work. Using ‘similarity transformations’, the main equations which are partial in nature are transformed to ODEs (ordinary differential equations) which are numerically solved with the assistance of ‘shooting technique and Runge–Kutta method’ using MATHEMATICA software. The outcomes of this investigation have a noteworthy impact on the physical outlook for flow field, transfer of heat and mass. Fluid velocity diminishes due to the rise of magnetic parameter but increasing nature of concentration and temperature are observed. For the rising volume fraction of Al2O3 nanoparticles as well as for rising volume fraction of Cu nanoparticles, the heat transfer coefficient rises. Momentum ‘boundary layer thickness’ diminishes for rising velocity slip. 19.694% decrease in rate of surface heat transfer is observed when volume fraction of Al2O3 nanoparticles changes from 0.01 to 0.12 whereas 24.394% decrease is noted when volume fraction of Cu nanoparticles changes from 0.2 to 0.14. The consequences of this study can be applied to many thermal systems used in engineering and industrial developments that utilize hybrid nanofluid for heating and cooling purposes.

Improvement of the Thermal Performance of PCM-Based Heat Sink Used in Electronic Cooling by Adding Nano-Particles

Recently, thanks to the technological advances, electronic devices are getting smaller in size. This causes an increase in the heat generation per unit area. This heat has to be removed from electronic devices for them to be longer-lasting, more efficient and more reliable. There are many active and passive methods designed for this objective. One of them is embedding phase change material (PCM) in the heat sink. PCM, during the phase change stage, absorbs the heat generated in the system and thus aids in keeping the temperature at a certain value. The biggest downside of PCM is its rapid conduction of heat. PCM properties can be improved by using nanoparticles. In this study, nanoparticles such as TiO2 and CuO were added to PCM and such a modified PCM is used in a finned heat sink. The thermal behavior of the PCM with addition of 1%, 2% and 5% TiO2 and CuO was investigated numerically in three dimensions. RT-28HC was used as the PCM in the study. It was shown that as the nanoparticle ratio increases, heat transfer coefficient of the PCM rises and the melting time of Nanoparticle PCM (NPPCM) is less than that of pure PCM. However, it was observed that, the melting time of PCM with CuO added is longer than that of the PCM with TiO2 added.

Configuration optimization of a biomass chemical looping gasification (CLG) system combined with CO2 absorption

Biomass chemical looping gasification (CLG) combined with CO2 absorption in a dual circulating fluidized bed (DCFB) has emerged as an advanced technology for clean and efficient biomass utilization, yet the reactor design for achieving higher gasification performance and the in-depth understanding of physical-thermal-chemical characteristics is still lacking. This study presents an optimized design aimed at enhancing hydrogen production and carbon reduction in the biomass CLG process with a DCFB reactor by employing the multiphase particle-in-cell (MP-PIC) method integrated with thermochemical sub-models. The proposed reactor is comprehensively compared with the original reactor from the experimental setup in terms of particle mixing, heat transfer, and gasification behaviors. The results indicate that compared to the original setups, the proposed CLG system demonstrates: (i) an improved gas-solid mixing, as evidenced by the particle mixing index rising from 0.23 to 0.34; (ii) an enhanced particle heat transfer coefficient, which boosts heat and mass transfer process; (iii) a 10.11 % increase in H2 concentration alongside a 23.71 % decrease in CO2 concentration; (iv) a particle distribution characterized by higher concentration at the bottom and lower concentration at the top, along with intensified particle back-mixing. The pressure drop inside the combustor is higher than that in the gasifier. A smaller absorbent mean particle diameter and lower-positioned biomass feeding port contribute to the improvement of the CLG performance.

Addressing multi-step inverse heat transfer problems via reduced order models in a cooling process for polymer pipes with sparse measurements

In modern polymer pipe extrusion processes with connected post-processing steps, the intermediate cooling and conditioning process is essential for the resulting product quality. In such cases, computationally efficient models are required for real-time process control and optimization. Unfortunately, heat transfer coefficients are rarely known for actual production processes, leading to an inverse heat transfer problem. Existing methods mainly rely on computationally intensive numerical models or on data intensive neural networks. Both are not suitable, if only sparse measurements are available and a fast execution time is required. In contrast to that, we propose to use a proper orthogonal decomposition and project the governing heat equation onto extracted basis functions via the Galerkin method. This leads to an efficient and accurate reduced order model, which can be used for parameter identification and subsequent process control. Regarding the identification, we address the ill-posed problem with well-known relative constraints, l2 regularization and decomposition of coefficients based on the Nusselt number. Simulation and experimental results show that the heat transfer coefficients are consistently identified and robust against initial parameter guesses despite sparse and noisy temperature measurements. Consequently, the proposed method can be efficiently applied in cooling and conditioning processes in polymer extrusion and related applications such as identifying the heat transfer coefficients and thermal resistance in pressurized surge lines of nuclear power plants and brick walls in melting furnaces respectively.

Quality control of functioning of the structure “object-thermoelectric cooler-heat sink” of the system of providing thermal modes

The analysis of the mathematical model of the system of providing thermal modes with the use of thermoelectric cooling to assess the influence of the conditions of heat exchange of the heat sink with the medium on the main parameters, reliability indicators and dynamic characteristics of a single-cascade thermoelectric cooler at a given temperature level of cooling, medium temperature, geometry of branches of thermoelements for different current operating modes is considered. The results of calculations of the main significant parameters, reliability indicators, dynamic and energy characteristics of a single-cascade cooler and heat sink of the selected design at a given temperature level of cooling, medium temperature, thermal load, geometry of branches of thermoelements for various characteristic current operating modes are given, when the conditions of heat exchange on the heat sink of the given design under variation of the heat transfer coefficient. It is shown that with the increase of air flow velocity on the heat sink the heat transfer coefficient increases and thus the temperature drop on the heat sink of the thermoelectric cooler with the medium decreases, which allows to significantly reduce the relative failure rate of the cooler and thus increase the probability of failure-free operation of the whole device. When operating a system for providing thermal modes comprising a cooling device, a heat sink, and an electric fan used for dissipating heat output to the environment, different modes of operation of the electric fan (air flow rate) can be used. With the increase in air flow rate of the electric fan increases the velocity of air flow in the live section of the heat sink of a given design, which leads to an increase in the heat transfer coefficient. This, in turn, makes it possible to reduce the temperature drop at a given design of the system for ensuring thermal modes. The possibility of control of reliability indicators, namely, relative intensity of failures and probability of failure-free operation of thermal mode systems of different designs (current modes, number of thermocouples, surface area of the heat sink) at a given cooling level (medium temperature, thermal load, geometry of thermocouples) under changing conditions of heat exchange of the heat sink with the medium is considered.

Effect of profiled endwall on nozzle guide vane with coolant purge flow

The aerothermal performance of a gas turbine could be improved by applying endwall profiling to the nozzle guide vane. In this study, various thermal performance factors of flat and profiled endwalls with purge coolant flow were investigated using adequate experimental methods. Each experiment was conducted under same exit Reynolds number (300,000) for the flat and profiled endwalls. Because secondary vortices in the nozzle passage were weakened by the endwall profiling, the upstream purge coolant covered the endwall surface wider and further with the profiled endwall. Moreover, the heat transfer coefficient in upstream region could be reduced with the weakened secondary vortex. The experimental results indicated that the area-averaged film cooling effectiveness on the profiled endwall was 67.7 % higher and the area-averaged Sherwood number was 18.3 % lower than those on the flat endwall. Although the downstream region of the profiled endwall exhibited a negative cooling performance, the overall area-averaged net heat flux reduction was 169 % higher than that on the flat endwall. Thus, if an additional cooling system was applied to the downstream region of the passage, the profiled endwall could effectively improve not only the aerodynamic performance but also the cooling performance of the nozzle guide vane.

Parameter optimization of thermal network model for aerial cameras utilizing Monte-Carlo and genetic algorithm

It is crucial to precisely calculate temperature utilizing thermal models, which require the determination of thermal parameters that optimally align model outcomes with experimental data. In many instances, the refinement of these models is undertaken within space instruments. This paper introduces an optimization methodology for thermal network models, with the objective of enhancing the accuracy of temperature predictions for aerial cameras. The investigation of internal convective heat transfer coefficients for both cylindrical and planar structures provides an estimation of convective thermal parameters. Based on the identification of thermally sensitive parameters and the reliability evaluation of transient temperature data through the Monte-Carlo simulation, the genetic algorithm is employed to search for global optimal parameter values that minimize the root mean square error (RMSE) between calculated and measured node temperatures. As a result, the optimized model shows significantly improved accuracy in temperature prediction, attaining an RMSE of 1.07 ℃ and reducing the maximum relative error between predicted and experimental results from 33.8 to 3.1%. Furthermore, the flight simulation and thermal control experiments validate the robustness of the optimized model, demonstrating that discrepancies between the observed and predicted temperatures are within 2 °C after re-correcting the external convection heat transfer coefficient value.

Modeling of Supercooled Large Droplet Physics in Aircraft Icing

This paper aims to investigate phenomena that are related to SLD conditions in aircraft icing including gravity, non-spherical droplets, droplet breakup and droplet splash using an in-house computational tool. The in-house computational tool involves four modules for the computation of the flow field, droplet trajectories, convective heat transfer coefficients and ice growth rates. Droplet trajectories are computed using the Lagrangian approach, while ice growth rates are calculated using the Extended Messinger Model. In order to extend the capabilities of the computational tool to include SLD-related phenomena, empirical models that represent SLD physics are implemented. An extensive study has been performed using MS317 and NACA0012 airfoils, that aims to bring out the relative importance of the SLD-related phenomena, particularly on water catch rates and ice formation. The results of the study pointed to some important new conclusions that may shed further light on SLD physics. For example, multiple droplet breakup has been observed under certain conditions and droplet breakup emerged as a more important effect than previously reported. It was also seen that droplet splash influences both the energy balance and the mass balance in the icing process, which has been shown to have an important effect on the final ice shape, especially for very large droplets.