Nusselt Number Data Research Articles

Jet array impingement heat transfer in a rectangular cavity with effusion holes

Various researchers have studied jet array impingement heat transfer in impingement/effusion cooling systems. However, there is a lack of research on impingement/effusion cooling systems installed within rectangular cavities that focus on the impact of the proximity of the jet hole to the cavity sidewalls on cooling performance. The main objective of this study is to investigate the flow and heat transfer characteristics of jet array impingement with effusion holes in a rectangular cavity, considering various spacings between the cavity sidewalls and the outermost jet hole. The design parameters in this study include the ratio of the jet hole pitch to jet hole diameter of 7.1, 10.0, and 16.7, and the ratio of the distance between the jet and impingement plates to jet hole diameter of 2, 6, and 10, with the Reynolds number based on the jet hole diameter ranging from 2500 to 15,000. Heat transfer characteristics in the stagnation region and wall jet region were examined using local Nusselt number distributions on the impingement surface, measured by liquid crystal thermography. The local Nusselt number was high in the stagnation region and decreased radially from the stagnation region as the wall jet region formed. The closer the outermost jet hole is to the sidewall, the higher the Nusselt number on the impingement surface near the sidewall. Moreover, the flow structure in the rectangular cavity was numerically investigated, and the velocity vectors and streamlines showed that primary and secondary vortices were generated in the middle of two neighboring jets and near the sidewall, respectively. This study also assessed previous average Nusselt number correlations. Based on experimentally determined average Nusselt number data with 54 center unit cells and 1296 side unit cells, new correlations to predict the average Nusselt number on the impingement surface in a rectangular cavity with effusion holes were developed.

Thermo-hydraulic and exergetic analysis of rectangular channel with integrated jet impingement and roughness

ABSTRACT This experimental study investigates an innovative approach to enhance surface heat transfer efficiency by employing V-pattern protrusions in conjunction with an impinging air jet. The synergy between surface roughness and the air jet induces heightened turbulence, resulting in significantly improved heat transfer performance. Various parameters on a jet plate, such as relative streamwise spacing (X/Dh), relative spanwise spacing (Y/Dh), and relative jet diameter (dJ/Dh), were systematically explored over a Reynolds number range of 4,000 to 18,000, representing the operational range. Optimal thermo-hydraulic efficiency was achieved at specific parameter values: relative streamwise spacing (X/Dh) of 1.7, relative spanwise spacing (Y/Dh) of 0.86, and relative jet diameter (dJ/Dh) of 0.086. Statistical correlations were established based on experimental data for both Nusselt number and friction factor. Furthermore, an exhaustive exergetic analysis was conducted to evaluate the thermal system’s sustainability, potential for waste heat recovery, and avenues for improvement. This study’s significance lies in its pioneering approach to augmenting heat transfer through the novel integration of V-pattern protrusions and impinging air jets. The results not only delineate optimal parameter configurations for enhancing heat transfer but also provide insights into system sustainability, waste heat recovery potential, and broader applications. By amalgamating distinct techniques, this research advances the existing literature by achieving superior thermal performance.

Experimental and ensemble machine learning analyses of heat transfer, friction factor and thermal performance factor of rGO/water nanofluids in a tube

This paper explains about the experimental evaluation of thermophysical properties, heat transfer coefficient, Nusselt number, friction factor, and thermal performance factor of water-based reduced graphene oxide (rGO) nanofluids passes through a tube under turbulent flow conditions. The rGO nanoparticles in this study was prepared based on the Hummer's procedure. The thermophysical properties were estimated at different volume loadings from 0.5 % to 2.0 % and at different temperatures from 20 °C to 60 °C, respectively, similarly, the heat transfer and friction factor experiments were conducted in the Reynolds number ranging from 1800 to 21,000. The obtained data of heat transfer coefficient, Nusselt number, friction factor and thermal performance factor was predicted based on the advanced machine learning algorithms of boosted regression tree (BRT), and extreme gradient boosting (XGB), respectively. Results indicated that, at 2.0 % vol. of rGO/water nanofluid the thermal conductivity is raised by 26.95 % at a temperature of 60 °C, viscosity is raised by 63.29 % at a temperature of 20 °C, over base fluid. Moreover, the results are further shown that, at 2.0 % vol. of nanofluid the Nusselt number, heat transfer coefficient, factor in friction, drop in pressure, and pumping power raise of 34.80 %, 44.19 %, 16.73 %, 10.48 %, and 4.55 % at a Reynolds number of 13,705, against water. The correlation coefficient (R2) results predicted from BRT and XGB models for Nusselt number data is 0.9831 and 0.994, respectively. It is understood that the XBG algorithm predicts very accurate values compared to BRT algorithm with a less mean square error. The overall performance of the system was raised by 1.28 -folds than water. Using the experimental data, new Nusselt number and friction factor correlations were proposed.

Relative Influences of Inertia and Polymeric Viscoelastic Effects on Nusselt Numbers within Rotating Couette Flows

In past investigations of elastic instabilities and elastic turbulence, almost no attention has been devoted to the effects and influences of inertial phenomena. Within the present investigation, Nusselt number data are provided to illustrate the relative influences of inertia and polymeric viscoelastic phenomena within a rotating Couette flow (RCF) environment. Data are provided from experimental measurements of local surface heat transfer characteristics for different flow passage heights, one radial position, and different values of disk rotational speed for polyacrylamide polymer concentrations ρ of 0 ppm, 100 ppm, 150 ppm, and 300 ppm. With this approach, data for a wide range of shear rate γ˙ values, Weissenberg numbers, and first normal stress difference values are provided. Nusselt number data are provided as dependent upon a newly developed P′ parameter, equal to ReEI/Re0.22, which collapse into a single distribution over the range of P′ values considered which range from 0 to about 182. Such characteristics indicate that the P′ parameter provides an appropriate means to simultaneously account for the relative influences of inertia and polymeric viscoelastic effects. The use of such a power law dependence for Re additionally gives P′ values which are dominated by ReEI values when the Weissenberg number Wi is greater than the elastic instability transition onset value. The experimental conditions associated with this value correspond to the change from inertia domination (with buoyance influences) to polymeric viscoelastic domination which occurs for shear rates in the vicinity of 11 to 12 s−1. For Weissenberg numbers greater than the onset value, Nusselt numbers associated with H = 5 mm are generally the highest values measured, with magnitudes that steadily increase with γ˙. Associated Nusselt numbers become as high as about 3.0, whereas zero-shear rate values (obtained with zero rotation) are in the vicinity of 1.0. At lower Weissenberg number magnitudes (below the transition onset value), Nusselt numbers cover a wide range of values as experimental conditions and configuration are varied, as a consequence of the complicated and simultaneous influences of inertia, buoyancy, and dilute polymer presence.

Thermal performance augmentation of solar air heater with curved path

Poor heat convection from absorber to airstream limits the benefits of solar air heater (SAH) utilization. This study aims to maximize the extracted heat from the absorber by increasing air flow mixing rate and boundary layers separation process. Thereby, SAHs with smooth curvilinear paths of radiuses of 5 cm (SAH5), 15 cm (SAH15), and 25 cm (SAH25) are introduced. Moreover, CFD is employed to conduct the present study, and model predictions are found to yield good agreement with respect to well-known correlations from literature. The findings reveal that thermal performance of curved SAH does not vary significantly after path's radius of 15 cm. Additionally, data of Nusselt number of SAH15 are found 3–7%, and 55–83% greater than those of SAH5 and conventional SAH, respectively. Nevertheless, data of friction factor of SAH15 are found 3.2–9.6% lower than those of SAH5. Overall, SAH15 contains smaller stagnant areas, yields better flow distribution, and owns higher overall thermal performance with respect to SAH5.

Heat transfer simulation of nanofluids heat transfer in a helical coil under isothermal boundary conditions using COMSOL multiphysics

In the current paper, a numerical model was designed using COMSOL Multiphysics software based on experimental results to predict Nusselt number of TiO2, ZnO and Ag water-based nanofluids in helical coil under isothermal boundary conditions. All Nusselt number data extracted from the model were compared with experimental data to validate the model and the results showed that the model gives good accuracy and the model could be used to predict non-experimental data. Root Mean Square Error (RMSE) was calculated to evaluate model accuracy and the results were 4.35, 2.40 and 2.53 for TiO2/water, Ag/water and ZnO/water respectively. The model was used to predict non-experimental data and the results were logically predicted compared with experimental data and the model was proven to be sufficient for predicting non-experimental data. Model results were compared with two types of artificial neural networks predicting Nusselt number Feed Forward Neural Network (FFNN) and Generalized Regression Neural Network (GRNN). The deviation between predicted data and experimental data was calculated and the results indicated that GRNN network has the highest accuracy with maximum deviations of +0.02% & −0.3% while the COMSOL model has a maximum deviation of +4.5% & −5.9% and finally FFNN network +8.9% & −5.7%.

Combined effects of surface sharpness and transverse curvature on thermal transport in separating flow region

Heat transfer analysis in a retarded laminar boundary layer over bodies of revolution with a variable radius subject to retarded surface temperature is presented. This study focuses to develop numerical data for local Nusselt number N ux under the influence of retarded free stream velocity and decreasing surface temperature along with body contour and surface transverse curvature. With the use of such retarded velocities and body contour the similarity of flow phenomenon does not sustain, and the problem becomes non-similar in nature which has been solved using an efficient numerical scheme, commonly known as Keller-Box. The effects of pertinent parameters such as exponent of free stream velocity m, exponent of surface temperature q, body contour n, and surface transverse curvature k on temperature profile, rate of heat transfer at the surface, and energy thickness of thermal boundary layer are presented through various graphs and tables. The rate of heat transfer and the energy thickness of the thermal boundary layer are observed to decrease with increasing levels of retardation. Furthermore, the rate of heat transfer decreases as the body contour parameter increases, whereas the surface transverse curvature parameter exhibits the opposite trend.

A Numerical Study on Swirling Hot Air Anti-Icing with Various Surface Structures on the Internal Wall

Swirling hot air is a promising heat transfer enhancement technology for anti-icing applications in aircrafts, where the swirling flow is accompanied by pretty high turbulence and a quite thin boundary layer. It is of interest to investigate the compound heat transfer characteristics of the swirling air configuration combined with surface structures on the internal wall. This paper carries out a series of numerical computations to obtain the Nusselt number and pressure loss data in such a swirling air heat transfer system with four kinds of surface structures (trenches, ribs, dimples and bulges) on the wall and with different tangential inlet jets placed along the tube. At a tube Reynolds number from 10,000 to 50,000, the results show that the surface dimples and bulges are conducive to improving the Nusselt number, but the surface trenches and ribs show a Nusselt number deterioration relative to the smooth swirl tube. Among the four investigated surface structures, the surface bulges perform best, which can enhance the Nusselt number by up to 15.0%, increase the total heat transfer quantity by up to 17.3% and reduce the hot air pressure loss by up to 15.6%. Furthermore, the circumferential velocity distribution and swirl number are introduced to describe the flow fields. The surface trenches and ribs lead to less of a reduction in the circumferential velocity and swirl intensity, while the surface dimples and bulges could significantly suppress the in-tube swirl intensity.

Prediction of nanofluid heat transfer characteristic and pressure drop in helical coil via artificial neural networks

In this paper, experimental data of Nusselt number and pressure drop utilizing TiO2/water, ZnO/water, and Ag/water nanofluids in helical coils under isothermal conditions were used to design an artificial neural network to predict Nusselt number and pressure drop for experimental and predict data. Feed Forward Neural Network (FFNN) and Generalized Regression Neural Network (GRNN) were designed. All predicted results were compared with the original experimental data and the results showed that both networks could be used to predict Nusselt number and pressure drop. Root Mean Square Error (RMSE) was used to measure the accuracy of each neural network. Predicted Nusselt number average RMSE for FFNN and GRNN were 4.84 and 0.004, while expected Nusselt numbers were 4.009 and 0.63. Predicted pressure drop average RMSE for FFNN and GRNN were 6.78 and 0.005 respectively while the average RMSE for expected pressure drop were 6.173 and 0.105 respectively. GRNN showed more accuracy than FFNN. The maximum deviation between trained data and experimental data for FFNN and GRNN were ±15.5% and ±0.02%, respectively. The maximum deviation between predicted data and experimental data for FFNN and GRNN were ±13.1% and ±1.6% respectively. The generated networks to predict non-experimental data showed good and logical behavior and proved that they are sufficient in Nusselt number and pressure drop prediction.

Experimental Investigation on Heat Transfer Enhancement of Artificially Roughened Solar Air Heater

In this article, an absorber plate of solar air heater attached with a combination of opposite apex triangular cross-sectioned rib roughness is experimentally analyzed. A series of experiments are carried out to investigate the turbulent airflow for various rib arrangements. This study aims to find effect of pitch of rib roughness element on the heat and friction properties in solar air heater. The studied parameters are relative roughness height of 0.045 and relative roughness pitch from 5 to 12.5 for Reynolds number range from 3000 to 18,000. Highest enhancement in Nusselt number and friction factor was found to be 3.05 and 4.14 times of smooth duct respectively. Highest thermohydraulic performance (2.02) was recorded at relative roughness pitch of 10. A new heat transfer correlation is also presented in this article for the rib roughened solar air heater. A linear stepwise regression algorithm is used to reduce the resulting data to correlation. The developed correlation accurately predicts all Nusselt number and friction factor data to within ± 6% relative absolute deviation.

Impact of electro-magneto-hydrodynamics in radiative flow of nanofluids between two rotating plates

Heat transfer improvement using electro-magneto hydrodynamics is a technique that can result in significant heat exchanger reduction as well as “on-demand” heat transfer. Electrohydrodynamic (EHD) is a multidisciplinary science that studies how fluids interact with electric fields or charges. It has been found applications in many areas such as EHD pump, EHD enhanced heat transfer, microelectromechanical systems (MEMS) and other industrial processes. MHD offers a broad array of applications for researchers in astrophysics, planetary magnetic fields, generators, flow meters, metallurgy, metal dispersion (granulation), ship propulsion, crystal development, magnetic filtration, and fusion reactors. Investigation of the mass and heat transfer properties of hybrid nanofluid Transformeroil+TiO2+Fe3O4 in three dimensions is considered. In this research, cumulative effects of magnetic and electric hydrodynamic are examined between two rotating plates in viscous hybrid nanofluid. To generate the hybrid nanofluid, transformer oil is utilized as a base fluid in the nanoparticles TiO2 andFe3O4. Using a similarity approach, the flow model in the form of PDEs is reduced to a system of dimensionless ODEs. The obtained equations are solved by using a shooting (bvp4c) method to attain a numeric solution. Reynolds number, rotational factors and effects of magnetic and electric properties in hydrodynamics have all been researched and argued about thermal efficiency, drag force, and mass flux. Numerical data of Nusselt number, Sherwood number, and drag forces are calculated. By minimizing the influence of physical constraints, the hybrid nanofluid enhances heat transfer rate and mass transport.

Calibration of a Computational Fluid Dynamics Methodology for the Simulation of Roughness Effects on Friction and Heat Transfer in Additive Manufactured Components

Abstract It is well known from the literature that surface roughness significantly affects friction and heat transfer. This is even more evident for additive manufactured (AM) components, which are taking an increasingly important role in the gas turbine field. However, the exploitation of numerical approaches to improve their design is hindered by the lack of dedicated correlations and computational fluid dynamics (CFD) models developed for such high roughness conditions. Usually, the AM components are simulated considering the surfaces as smooth or applying an equivalent sand-grain roughness (ks) that results in a velocity shift in the boundary layer. However, determining a priori the most appropriate value of ks is challenging, as dozens of correlations are available, returning scattered and uncertain results. A previous work proved how the CFD prediction of friction and heat transfer returns significant deviations, even exploiting the ks values obtained from experimental tests on the very same test case. That work also allowed identification of a promising CFD methodology based on friction and thermal corrections proposed by Aupoix from ONERA. The aim of this work is to further the assessment and calibration activity of the model, by analyzing additional experimental data of friction factor and Nusselt number from new test cases considering different geometries and flow conditions. The new coupons consisted of straight circular channels and wavy channels. This work represents a further step in the generation of a more validated and general methodology for the high-fidelity CFD analysis of AM components.

CFD based heat transfer correlation for ribbed solar air heater

To assess the influence of artificial roughness on heat transfer in solar air heater ducting, a variety of alternative approaches have been used to investigate the problem. In this article, an absorber plate of SAH attached with rib roughness is numerically analysed. Adding ribs to a solar air heater duct's surface is an excellent means of increasing the performance of the system. In this article a numerical analysis is carried out to investigate the turbulent air-flow for various rib arrangements. This study aims to find effect of pitch of rib roughness element on the heat transfer property of solar air heater. The studied parameters are rib height and pitch for moderate range of Reynolds number. Highest enhancement in Nusselt number was determined. A new heat transfer correlation is developed in this article for the rib roughened solar air heater. A linear stepwise regression algorithm is used to reduce the resulting data to correlation. The developed correlation accurately predicts all Nusselt number data to within ± 6% relative absolute deviation.

The Effects of Axisymmetric Convergent Contouring and Blowing Ratio on Endwall Film Cooling and Vane Pressure Side Surface Phantom Cooling Performance

Abstract To reduce the intensity of endwall secondary flow, the axisymmetric convergent contoured endwall is commonly designed in the first nozzle guide vane (NGV) passage of the real gas turbine engines. This endwall contouring can obviously alter flow field near endwall and affect the coolant flow through the upstream double-row discrete film holes. This leads to a significant influence on the endwall film cooling performance, vane surface phantom cooling, and vane passage aerodynamic performance. In this paper, a detailed numerical investigation on the endwall film cooling and vane pressure side surface phantom cooling was performed, at the simulated realistic gas turbine operating conditions (high inlet freestream turbulence level of 16%, exit Mach number of 0.85, and exit Reynolds number of 1.7 × 106). Based on a double coolant temperature model, a novel numerical method for the predictions of adiabatic wall film cooling effectiveness was proposed. This numerical method was validated by comparing the predicted results with experimental data of endwall Nusselt number, endwall film cooling effectiveness, and flow visualization near endwall. The results indicate that the present numerical method can accurately predict endwall thermal load distributions, endwall film cooling distributions, and vane surface phantom cooling distributions. The endwall heat transfer coefficient, endwall film cooling effectiveness, phantom cooling effectiveness of the vane pressure side surface, and total pressure loss coefficients (TPLC) were predicted and compared for two endwall contouring shapes (flat endwall and axisymmetric convergent contoured endwall) at three different blowing ratios (low blowing ratio of BR = 1.0, design blowing ratio of BR = 2.5, and high blowing ratio of BR = 3.5) with a constant density ratio of DR = 1.2, based on the present novel numerical method. Results show that the axisymmetric convergent endwall contouring leads to a slight enhancement (maximum enhancement level less than 20%) of endwall heat transfer in the entire vane passage (0 < x < 0.65Cx). The axisymmetric convergent endwall contouring has a significantly desired effect on endwall film cooling performance (maximum enhancement level of 67%), phantom cooling performance of the vane pressure side surface (maximum increase level approximately 100%), and aerodynamic loss (maximum reduction level of 1.45%) for all blowing ratio cases, but the benefit enhancement level is obviously affected by the blowing ratio values. This suggests that the optimum of endwall contouring shapes is an effective technical way to improve endwall film cooling performance and decrease the depletion of coolant; the coupled effects of the appropriate axisymmetric convergent endwall contouring and the optimum blowing ratio should be considered in the design process of advance endwall cooling schemes.

Modelling and Computational Experiment to Obtain Optimized Neural Network for Battery Thermal Management Data

The focus of this work is to computationally obtain an optimized neural network (NN) model to predict battery average Nusselt number (Nuavg) data using four activations functions. The battery Nuavg is highly nonlinear as reported in the literature, which depends mainly on flow velocity, coolant type, heat generation, thermal conductivity, battery length to width ratio, and space between the parallel battery packs. Nuavg is modeled at first using only one hidden layer in the network (NN1). The neurons in NN1 are experimented from 1 to 10 with activation functions: Sigmoidal, Gaussian, Tanh, and Linear functions to get the optimized NN1. Similarly, deep NN (NND) was also analyzed with neurons and activations functions to find an optimized number of hidden layers to predict the Nuavg. RSME (root mean square error) and R-Squared (R2) is accessed to conclude the optimized NN model. From this computational experiment, it is found that NN1 and NND both accurately predict the battery data. Six neurons in the hidden layer for NN1 give the best predictions. Sigmoidal and Gaussian functions have provided the best results for the NN1 model. In NND, the optimized model is obtained at different hidden layers and neurons for each activation function. The Sigmoidal and Gaussian functions outperformed the Tanh and Linear functions in an NN1 model. The linear function, on the other hand, was unable to forecast the battery data adequately. The Gaussian and Linear functions outperformed the other two NN-operated functions in the NND model. Overall, the deep NN (NND) model predicted better than the single-layered NN (NN1) model for each activation function.

Numerical approach for chemical reaction and suction/injection impacts on magnetic micropolar fluid flow through porous wedge with Hall and ion-slip using Keller Box method

In the present investigation, influence of the chemical reaction, magnetic field and slip on micropolar fluid flow via a porous wedge in the existence of Hall and ion-slip are examined. The pertinent highly non-linear PDEs are changed into an arrangement of non-linear coupled ODEs by utilizing similarity transformation. The equations were calculated using the ‘Keller Box Method’ (KBM). The numerical data for skin-friction coefficients, Nusselt number, Sherwood number, velocities, thermal and concentration fields are portrayed by graphs for various existing parameters and analyzed in detail. The heat transfer characteristics of working magnetic fluid escalated with acceleration in slip and power-law parameters. Moreover, the mass transfer function escalated with material and chemical reaction parameters.

Simulation of the impact of solar radiation intensity on the performance of economical solar water desalination still in Semnan province

Semnan province with a total area of 97000 km2 is the sixth biggest province in Iran. The evaporation rate in this province is high and can be. The index of the urban and rural water networks in this province is much higher than the global average, but according to the goals set for water supply to all people in all cities and villages, using new technologies is an effective way. High potential evaporation intensity in Semnan province, which reaches 1000-3000 (mm) per year, can be converted from a threat to an opportunity by using it as a new source of energy for a sustainable safe drinking water supply. In order to use of evaporation capacity, in this paper the impact of solar radiation intensity on the performance of single-slope solar still is investigated. The solar radiative flux depends on geographical location, season, and time. In this study, the dimension and temperature of the basin are constant and the effect of radiation intensity on water productivity of solar stills is investigated as a function of time, month (April) and location (Semnan province). The accuracy of the numerical method has been evaluated using different models and experimental data for the average Nusselt number on water surface and production rate of water. Results also indicate that the variation trends for radiation intensity are similar to the production rate. The maximum water production rate belongs to 12 o'clock with a 5.6% increase in comparison with 7:00 a.m., which has the lowest evaporation rate in the bell shaped curve.

Impact of Cooling Injection on Shock Wave Over a Flat Tip in High Pressure Turbine

AbstractCooling design of highly loaded turbine blade tips is challenged by the scarcity of experimental data and the lack of physical understanding in cooling and overtip leakage (OTL) interaction under transonic conditions. To address these issues, this paper carried out transient thermal measurements through infrared thermography on a transonic flat tip with and without cooling injection. Experimental data of Nusselt number and cooling effectiveness were obtained and compared with computational fluid dynamics (CFD) results for numerical validation. Both experimental data and simulation results show that cooling injection drastically augments tip Nusselt number near pressure side (PS) which is upstream of ejection, and in areas around coolant holes. Moreover, a strikingly low Nusselt number stripe is observed downstream of cooling injection from one of the holes in aft portion of blade. The strip is directed transverse to local OTL streamline flowing from pressure to suction side (SS) and sprawls to adjacent coolant wakes. Further numerical analyses concluded that cooling injection changes tip aerodynamics and overtip shock wave structure fundamentally. Oblique shock waves across the uncooled flat tip are replaced by a confined shock train downstream of cooling injection and between cooling holes, which is constituted by two shocks normal to local OTL flow coming from pressure side. Across the first shock, density and pressure increases abruptly, contributing to thickening of tip boundary layer and the plummet of skin friction on tip surface, which is responsible for the sharp decline of tip Nusselt number and therefore, formation of low heat transfer stripe downstream cooling injection.

Predicting Parameters of Heat Transfer in a Shell and Tube Heat Exchanger Using Aluminum Oxide Nanofluid with Artificial Neural Network (ANN) and Self-Organizing Map (SOM)

This study is a model of artificial perceptron neural network including three inputs to predict the Nusselt number and energy consumption in the processing of tomato paste in a shell-and-tube heat exchanger with aluminum oxide nanofluid. The Reynolds number in the range of 150–350, temperature in the range of 70–90 K, and nanoparticle concentration in the range of 2–4% were selected as network input variables, while the corresponding Nusselt number and energy consumption were considered as the network target. The network has 3 inputs, 1 hidden layer with 22 neurons and an output layer. The SOM neural network was also used to determine the number of winner neurons. The advanced optimal artificial neural network model shows a reasonable agreement in predicting experimental data with mean square errors of 0.0023357 and 0.00011465 and correlation coefficients of 0.9994 and 0.9993 for the Nusselt number and energy consumption data set. The obtained values of eMAX for the Nusselt number and energy consumption are 0.1114, and 0.02, respectively. Desirable results obtained for the two factors of correlation coefficient and mean square error indicate the successful prediction by artificial neural network with a topology of 3-22-2.

Transport Phenomenon of Simultaneously Developing Flow and Heat Transfer in Twisted Sinusoidal Wavy Microchannel under Pulsating Inlet Flow Condition

Heat transfer operations in microchannel are of special relevance in designing micro-devices involving accumulation of high heat flux. The current study explores simultaneously developing, unsteady laminar flow inside a twisted sinusoidal wavy microchannel and heat transfer involved. A square cross-sectioned channel is taken for the study. The channel is wavy in nature as well as twisted about the flow axis. The modified geometry helps in enhancing out of plane mixing of the fluid and formation of recirculation inside the flow. The evaluation is performed for a Reynolds number range of 1–100. A sinusoidal (varying with time) normal velocity component is employed at the inlet. The study was conducted over a range of pulsation amplitude and frequency. To solve the governing equations, a finite volume based method was employed. The Nusselt number data shows significant enhancement for the sinusoidal inlet velocity as compared to that of a steady case. In terms of pressure drop, the proposed design shows that at different frequencies and amplitudes, it can keep the pressure drop within admissible limits. Entropy generation is used as the measure of dissipated energy. Performance in terms of entropy generation is also reported.