Values Of Heat Transfer Coefficient Research Articles

Assessment of heat transfer capabilities of some known nanofluids under turbulent flow conditions in a five-turn spiral pipe flow

Abstract In this study, the thermo-flow behaviours of the spiral tube were examined using water and some nanofluids such as TiO2, Al2O3, Fe2O3, CuO, ZnO, and CeO2. The computational flow dynamic modelling of the spiral coiled tube was performed with ANSYS 20 software program. The k–ε model with a standard wall function was used to simulate the thermo-flow characteristics. The solution of the governing equations was performed using the discretization method of finite volume. The study was carried out considering the case of fluid-to-fluid heat transfer in turbulent conditions. The influence of different key design parameters such as Reynolds number, different nanofluids, and flow arrangements was of main interest. The volume concentration of the nanofluids is 1%. The experiments were performed at different Reynolds ranges (9,000, 14,000, 20,000, and 25,000). The outlet temperature values, heat transfer coefficient, coefficient of friction, Nusselt number values of water, and nanofluids were found and compared. It was found that the outlet temperature, heat transfer coefficient, and Nusselt number values of water were the lowest, while the coefficient of friction value was the highest compared to the nanofluids. Among the nanofluids, CeO was found to have the highest outlet temperature, heat transfer coefficient, and Nusselt number value, as well as the lowest coefficient of friction value. TiO2 was found to have the lowest outlet temperature (T out), the heat transfer coefficient value, and the highest coefficient of friction value. Al2O3 was found to have the lowest Nusselt number. In addition, Nusselt number values were obtained at different Dean numbers of water (2,200, 3,400, 4,900, 6,100, 7,350, and 8,600) and found to be compatible with previous studies. In addition, the coefficients of friction values of water at different velocities (0.18, 0.24, 0.41, 0.71, 0.95, 1.07, and 1.18) were obtained and found to be compatible with previous studies.

Temperature distribution analysis and mechanical property prediction of wire loops in the Stelmor air-cooling system

During the Stelmor air-cooling process, the temperature distribution has a significant impact on the wire loops' final mechanical properties. The temperature distribution during air-cooling process is accurately solved by establishing three-dimensional model and Computational Fluid Dynamics (CFD) simulation. It is also found that the heat transfer coefficient on the cross section of the wire loop is very different, with a difference of 70–100 Wm−2K−1. The average value of the surface heat transfer coefficient of the wire loops section is used to replace the surface heat transfer coefficient of the wire loops, which improves the temperature distribution calculation accuracy, which is not considered by previous scholars. The finite difference method is used to calculate the mathematical model of the temperature distribution during the Stelmor air-cooling process. It is found that the maximum temperature difference of the wire during the cooling process is 90–110 K. The prediction model of mechanical property of wire after air-cooling was established, and distribution of mechanical property of the wire loops was obtained, and the reason for the uneven distribution of mechanical property of the wire loops was found.

The thermo-mechanical coupling method of brake disc based on dynamic convective heat transfer

With the increase of train speed, the brake disk receives more heat input, causing its own temperature to reach a higher level. Due to the complex structure of the brake disk, its convective heat transfer coefficient is difficult to calculate, which makes the analysis of the convective heat dissipation between the brake disk and the air complicated. In this article, based on the software FLUENT and ABAQUS, by combining the fluid-solid coupling method and the thermo-mechanical coupling method, the dynamic convective heat transfer and the transient temperature field of brake disk are simulated. The maximum value of dynamic convective heat transfer coefficient is 483 W/m2 ∙ K at the running speed of 350 km/h. As for the transient temperature field, not only the contact relationship between the brake disk and the brake pad is considered, but also the dynamic convective heat transfer between the brake disk and the surrounding air domain is applied. The simulation results are more in line with the actual situation and the engineering application.

Thermal-hydraulics performance evaluation of bubble swarms sweeping tube bundles in a direct contact gas-liquid-solid reactor

Direct contact gas-liquid-solid reactor pertains to an extremely high efficiency heat-exchange facility in industrial application. Nevertheless, the scarcity of quantitative analysis data hinders the optimal design of this type of reactor. In the present study, a novel variable bubbles size modeling approach which considers the bubble swarms breakup and coalescence rates, is proposed to evaluate the complex thermal-hydraulics performance of bubble swarms sweeping tube bundles. On the basis of verifying the responsibility of the numerical modelling with published experimental data, the intrinsic link of hydrodynamics and thermodynamics parameters on reactor features, including field characteristics, gas holdup, bubble swarms diameter distribution, gas–liquid interfacial area, temperature difference and heat flux inside different tube bundles regions, are deeply revealed. Results demonstrate that the temperature difference between bubble swarms and tube bundles walls is approximately equal to 2K. Interestingly, different positions of heat exchanging tubes affect the peak value of circumferential heat transfer coefficient. For typical Tube 1–2, the maximum value of 3146.28 W/m2·K appears around 162°. The presence of tube bundles gives rise to the well-distributed iso-surfaces of bubble swarms which contributes to enhance heat transfer. When superficial gas velocities are respectively 0.09 m/s, 0.12 m/s and 0.14 m/s, the average bubble warms diameters are 13.47 mm, 16.22 mm and 17.24 mm. When initial liquid phase height increases from 342 mm to 378 mm, the corresponding gas–liquid interfacial area decreases by 16.2 % in total. Finally, two new modified dimensionless correlations were developed for the prediction of gas holdup and Nusselt number. The prediction errors are respectively 10 % and 6 %. The findings can improve the awareness for promising applications in design and scale-up processes of direct contact gas-liquid-solid reactor.

Fourier series-based modelling of the effects of thermal coupling on the transient dynamics of component loops in a coupled natural circulation loop

Energy efficiency in process industry and passive safety systems in nuclear power plants necessitate the use of buoyancy driven heat exchangers. The current study presents a 1-D numerical model of the buoyancy driven fluid system in a Coupled Natural Circulation Loop (CNCL) comprising water as the working fluid. In this study water at different temperatures is considered as the operating fluid in each of the loops. The study employs a 1-D model derived using a semi-analytical Fourier series. A validation study was carried out using the relevant literature to verify the mathematical model. A detailed parametric study on individual NCLs and their coupled system was conducted by varying the cross-sectional area keeping the other parameters constant to gain insights into the effect of thermal coupling on the long-term transient dynamics of each of the individual loops of the CNCL system, for stable, unstable – periodic, and unstable – chaotic conditions. The dynamics were analysed using the difference between transient buoyancy and viscous forces, and it was found that the overall heat transfer coefficient influences the coupling behaviour and the dynamics of the component loops in a CNCL. At lower values of the overall heat transfer coefficient, the component loops in the CNCL nearly retain their independent behaviour, i.e., the component loops hardly influence each other. It was also found that the temperature dependent fluid properties influence the stability of the CNCL system in some cases.

Enhanced flow boiling heat transfer in narrow gap with different widths using different-mode-interacting boiling

The concept of different-mode-interacting boiling (DMIB) utilizes the areas of two different thermal conductance materials by expanding the wetted area over the regions of their dry areas. This enhances the critical heat flux (CHF) and heat transfer coefficient (HTC) in a wide channel (e.g., Wch = 80 mm) to provide adequate cooling in previous study. In this study, the effectiveness of DMIB in enhancing the CHF and HTC was investigated when using a channel width (Wch = 10 mm) equal to that of the heating surface, aiming to provide better efficiency for both uniform surface (US) and nonuniform surfaces (NUSs) with material widths (W = 0.5 and 1.0 mm) in narrow gaps. Experiments were performed with a heating surface of 10 mm2 using subcooled deionized water at different temperatures ΔTsub = 2.0, 10, 20, and 30 K, inlet velocities v = 0.1, 0.2, and 0.4 m/s (corresponding to mass fluxes: 100, 200, and 400 kg/m2s), and gap sizes h = 1.0, 2.0, and 5.0 mm. The results revealed that the heat transfer performance of the NUSs was significantly enhanced compared to the US for both Wch. However, both the CHF and HTC values were higher with Wch = 80 mm than with Wch = 10 mm owing to the expansion of coalesced bubbles in the flow direction, sustained nucleate boiling regime, and effective liquid rewetting during the intermittent nucleate boiling-partial dryout near the CHF owing to the DMIB. The maximum CHF and CHF enhancement ratios for Wch = 10 mm were 3.59 MW/m2 and 52.2 %, respectively, whereas for Wch = 80 mm, they were 3.66 MW/m2 and 89 %, respectively. In addition, the HTC and HTC enhancement ratio for Wch = 10 mm were 1261 kW/m2K and a factor of 7, respectively, whereas those for Wch = 80 mm were 2026.9 kW/m2K and a factor of 12, respectively. In contrast, only a minimal difference existed in the heat transfer performance of Wch = 10 mm compared to that at Wch = 80 mm; therefore, Wch = 10 mm can be considered as having a better cooling efficiency per channel width due to the minimal pumping power and significant CHF and HTC enhancement.

Metallurgical Method of Determining Heat Transfer Coefficient in Simulations of Twin-Roll Casting

We herein suggest a metallurgical method using pure aluminum with no freezing temperature range to derive appropriate roll/melt interfacial heat transfer coefficients in simulation of twin-roll casting process. This method is inspired by the concept that the position of the kiss points where two solidifying shells encounter and the roll nip coincides under the condition where the roll load becomes zero as the roll rotation speed decreases. The conditions where the roll load becomes zero under various melt supply temperature conditions in the actual TRC process are found experimentally. These conditions are then applied to simulation models to derive heat transfer coefficient values. When comparing these values with those derived previously from the empirical relation for roll rotation speed and heat transfer coefficient, the conclusion is drawn that the deviation was reasonably low, around 10%.

A novel numerical method to evaluate the heat transfer characteristics of complicated CICC structures

In this article, we propose a numerical model for calculating the external heat transfer coefficient between the bundle region and its wall for cables in conduit conductor (CICC). With the assumption of local thermal equilibrium, one macro equation describing the steady heat transfer on the cross section of the CICC can be obtained. A key parameter, the effective transverse thermal conductivity keff, which takes the contribution of both strands and flowing fluid into consideration, is introduced. To calculate the effective transverse thermal conductivity keff, we first obtain the true distribution of different phases (fluid, copper and superconducting material) on a cross section of CICC with the help of the image recognition technique. Based on this, the value of the effective transverse thermal conductivity keff can be calculated numerically. Due to the large difference among the component thermal conductivities (at 4.5 K, typical values of the thermal conductivity of liquid helium, superconducting material and copper are kHe=0.024Wm−1K−1, kNb3Sn=0.04Wm−1K−1 and kCu=708Wm−1K−1; and the maximal ratio of thermal conductivity can be as high as about 30,000), the high-performance finite analytical method (FAM) is recommended to calculate keff. After obtaining the effective transverse thermal conductivity keff of the bundle region, the heat transfer coefficient can be calculated directly by solving a simple Poisson equation under proper boundary conditions. Two case studies are performed, including the JT-60 Super Advanced (JT-60SA) CICC and the dual channel International Thermonuclear Experimental Reactor, Toroidal Field Performance Sample (ITER-TFPS). The calculated values of heat transfer coefficient are consistent with the experimental results, which verifies our proposed model.

Analysis of the effect of the number of injector nozzles on the pressure and heat transfer coefficient in a hydrogen-diesel mixture diesel engine

In reciprocating internal combustion engines, the calculation of the heat transfer coefficient (HTC) is essential to estimate the heat transfer during combustion in the combustion chamber. The HTC calculation takes into account fluid flow and combustion processes and varies as a function of crank angle and location within the chamber. The mean HTC value is commonly used to calculate the thermo-mechanical analysis of various combustion chamber components. In this study, dynamic grids for the intake port, exhaust port and chamber are created in the chamber modelling section of the AVL-Fire software. The intake and combustion processes are then simulated and the calculated pressure data are compared with experimental data at 2800 rpm with 1, 3 and 6 hole injectors. Finally, the distribution of HTC over the chamber walls was evaluated using a time step method. The research also included verification of the HTC results with theoretical data obtained by Woschni and Hohenberg. In addition, with the decreasing availability of fossil fuels and the need for lower exhaust emissions from diesel engines, the use of blends of diesel and hydrogen fuel has become widespread. In this engine, a mixture of 10 % hydrogen and 90 % diesel fuel is used. The final results show that the heat transfer coefficient increases by approximately 1.72 % when hydrogen is added to diesel fuel due to the number of collisions between hydrogen and other fuel components.

Towards an improved thermometric method: Convective and radiative heat transfer for heat flux measurement through an indirect approach

Actual thermal performance of building walls need to be assessed through on-site tests. Several measurement procedures have been proposed during the last decades. Nonetheless, among them the Thermometric (THM) method has been poorly explored in literature, hence opportunities for improvements can be highlighted. The THM technique is a quite a new and non-standardized procedure for wall thermal characterization, based on the well-known Newton’s law of cooling. This law needs the heat transfer coefficient knowledge and there is no agreement about the value to apply when the THM method is used. In this work, a low-cost experimental apparatus characterized by a heated wooden sample was realized. Sensors were installed to measure heat fluxes through a common heat flux plate. The obtained values were compared with the heat flows achieved via the THM method, where dimensionless groups analysis was performed for computing suitable heat transfer coefficients obtained from data processing. The aim of this work is to lay the groundwork for overcoming the disagreement related to the value of the total heat transfer coefficient in the THM method by proposing and consolidating an alternative approach. The results show that the proposed data processing for the THM method can provide satisfying results in terms of indirect heat flux measurements, showing extremely low percentage differences (ranging from + 1.16 % to + 3.56 %) if compared with the HFM method.

A hybrid approach towards evaluation of average heat transfer coefficient in twin-roll strip casting mold

Continuous casting stands out as one of the most efficient and productive methods for producing billets, slabs, or thin sheets while conserving energy. Understanding the solidification dynamics and achieving defect-free sheets in continuous casting necessitates the accurate prediction of heat transfer coefficient (HTC) at the mold metal interface. Accurate prediction of HTC helps in selecting process parameters such as superheat temperature and casting velocity, which directly affect the production rate and quality of the cast component. Determining the HTC is a complex process, as it is influenced by various process parameters such as casting size, casting speed, superheat temperature, surface roughness, type of water used as a coolant, nozzle design and wettability. Therefore, the present study proposed a hybrid approach for finding HTC in a twin roll strip casting mold through a solidified shell shape, which is influenced by the factors affecting the heat transfer at the mold-metal interface. This approach integrates the experimental and simulation investigations. The numerical investigation used a three-dimensional coupled fluid flow and heat transfer equations with an assumed range of HTC (100–2000 W/(m2K)). The solidified shell shape for different HTCs was compared with the experimental solidified shape form at the outer wall of the mold using the solidification criteria. Results indicate that the initial HTC range of 100–1000 W/(m2K) does not lead to blockage of the graphite mold outlet. However, as HTC values approach 1000 W/(m2K) to 1400 W/(m2K), the melt obstructs the mold exit based on solidification criteria. The HTC values (1350 ± 150 W/(m2K)) obtained from the proposed methodology for mold, align well with the HTC values (1183 ± 593 W/(m2K)) calculated using lamellar spacing of the Al-Mg2Si composite microstructure. This hybrid approach presents a novel and straightforward method for determining HTC, offering accurate predictions that can enhance the precision of continuous casting models and provide a more nuanced understanding of solidification behavior.

Thermal performance of three concentrating collectors with bifacial PV cells. Part II – parametrical study

One of the problems in using PV cells to extract energy from sunlight is the temperature effect on PV cells. As the solar panel is heated, the conversion efficiency of light to electrical energy is diminished. Moreover, successive temperature elevations can cause dilatations in the array of cells which may also contribute to the degradation of the receiver. Some of the operating temperature mitigation approaches may include air-flow ventilation. In this study, data obtained by experimental and numerical simulations of a collector with bifacial PV cells is compared to the expressions found in the literature for the estimation of the heat transfer coefficient. Forced ventilation was applied to the studied collector as it accounts for much better heat dissipation. A new correlation for the estimation of the heat transfer coefficient is developed for such a geometry, for inlet velocities ranging between 3 and 8 m/s. Values of heat transfer coefficient estimated in the present work have been compared with studies of other researchers.

OPTIMIZATION OF SHELL AND TUBE HEAT EXCHANGER DESIGN WITH INCLINED BAFFLES

Shell and tube heat exchanger (STHeX) design development continues to be carried out to increase the effectiveness of a system. One way is to investigate the optimal baffle design. The new structure of STHeX with Inclined-Segmental Baffles is further investigated. The experiment was carried out using the numerical method Computing Fluid Dynamics (CFD) software with three-dimensional modeling. The results show that the heat change coefficient value is lower than conventional STHeX, However, the pressure drop value is reduced quite significantly. Therefore, it is necessary to know the overall heat transfer coefficient value per pressure loss (U/DeltaP). Hence, we get U/DeltaP values of 0.9 and 0.68 for STHeX with Inclined-Segmental Baffle and conventional STHeX, respectively. Thus, there is a significant increase ranging from 37-34%. It is concluded that STHeX with Inclined-Segmental baffles increases the U/DeltaP value significantly compared to conventional STHeX.

An Experimental Investigation on the Pool Boiling Heat Transfer of R-134a on Microporous Cu-MWCNT Composite Surfaces

Multiwalled carbon nanotubes (MWCNTs) exhibit outstanding physical properties, including high thermal conductivity, excellent mechanical strength, and low electrical resistivity, which make them suitable candidates for a variety of applications. The work presented in this paper focuses on the pool boiling performance of refrigerant R-134a on microporous Cu-MWCNT composite surface layers. A two-stage electrodeposition technique was used to fabricate Cu-MWCNT composite coatings. In order to achieve variation in the surface properties of the Cu-MWCNT composite surface layer, electrodeposition was carried out at various bath temperatures (25 °C, 30 °C, 35 °C, and 40 °C). All surfaces coated with the Cu-MWCNT composite demonstrated superior boiling performance compared to the uncoated surface. Heat transfer coefficient (HTC) values for Cu-MWCNT composite surface layers, prepared at bath temperatures of 25 °C, 30 °C, 35 °C, and 40 °C, exhibited improvements of up to 1.75, 1.88, 2.06, and 2.22, respectively, in comparison to the plain Cu surface.

Multi-objective optimization of thermal and daylighting performance for sightseeing elevators without air conditioning system considering economic cost

In the study, the shape, size and structure of the sightseeing elevators were investigated, and a prototypical model was established by Grasshopper. Furthermore, the performance and prices of glass were used to construct the function of price, then the multi-objective optimization method was adopted to simultaneously optimize the predicted percentage of people dissatisfied, useful daylight illuminance and cost of the building envelope of the elevators. The results showed that the optimal values of the total heat transfer coefficient, solar energy heat gain coefficient and total transmission of the envelope are 0.799 W/(m2·K), 0.164 and 0.153, respectively. Compared with that of “6 mm ultralow light transmission thermal reflective glass +12 mm air +6 mm transparent glass”, the predicted percentage of people dissatisfied decreases about 5.412 %. Though useful daylight illuminance has a small decrease of 1.167 %, cost of building envelope decreases by 60.127 %. In addition, the suitable working hours for three positions, where the control cabinets can be set at, have been significantly improved among the using frequency. In addition, ventilation systems were considered to improve the internal environment of sightseeing elevators, and appropriate control methods were selected to ensure the maximum operation of sightseeing elevators.

Critical heat flux, heat transfer and pressure drop at high mass fluxes for R123 in a single microchannel

This paper presents new experimental data on pressure drop, heat transfer coefficient, and critical heat flux during flow boiling of low-pressure fluid R123 in microchannels. High mass velocities were used, above the values found in the literature in tests with this fluid. Experiments were conducted in a single smooth and horizontal microchannel, with an internal diameter of 1.1 mm and heating sections of 46 and 100 mm. The mass velocities used were between 1500 and 7500 kg/m2s. Saturation temperature ranged from 40.1 to 85.1 oC. The outlet vapor quality varied between -0.54 and 0.53 for the CHF results, between 0 and 0.5 for the pressure drop results, and between 0 and 0.35 for the HTC results, respectively. Record critical heat flux values for flow boiling of R123 in smooth microchannels were achieved, reaching 1.44 MW/m2. An analysis was made of the influence of an upstream pressure drop in avoiding instabilities during critical heat flux experiments. The highest heat transfer coefficient values during convective boiling of R123 in smooth microchannels were also obtained, with values close to 43.3 kW/m2K. The saturation temperatures used were among the highest for flow boiling of R123 in smooth microchannels found in the literature. Correlations for frictional pressure drop, heat transfer coefficient, and critical heat flux were evaluated in predicting the experimental data. An analysis was made on the influence of the void fraction correlation when estimating both the accelerational and frictional pressure drop.

Effect of Horizontal Tube Position on Wall-to-Bed Heat Transfer in Air-Solid Fluidized Bed of Large Particles

Fluidized beds are extensively used in a variety of industrial applications, such as heat recovery systems, coal combustion, and solid particle drying. The effect of the position of the heat transfer tube on heat transfer from a horizontal bare tube in a 150 mm square cross-section fluidized bed containing large particles, ragi, and mustard is investigated. The influence of varying fluidizing velocities on heat transport is also examined for a fixed bed height of the large particles. When the position of the tube from the distributor plate was increased in 0.028m increments from 0.52 m to 0.080 m and then to 0.108 m, the heat transfer coefficient was reduced. Due to enhanced fluidization, all bed heights yielded almost comparable heat transfer coefficient values at velocities exceeding 1 m/s, 170 and 160 W/m2K for ragi and mustard, respectively. The dependency of the heat transfer coefficient on fluidizing velocity is qualitatively like that of small particles. An error deviation of around 8.8% was found when comparing experimental heat transfer coefficient values to those predicted from empirical correlations in the published literature.

Numerical study on thermal hydraulics characteristics during steam submerged jet condensation from rectangular CD nozzle

The phenomenon of steam-water direct contact condensation (DCC) has significant importance in nuclear industry due to its rapid and efficient heat and mass transfer rates. In this numerical study, three dimensional simulations of steam submerged jet condensation from rectangular converging-diverging (CD) nozzle into subcooled water has been investigated. The steam condensation phenomenon has been captured from thermal phase change model as user defined function (UDF) in ANSYS Fluent software. The computational results were validated using experimental results as well as previously published numerical study. The effects of steam pressure and water temperature on distributions of various thermal hydraulics parameters including velocity, pressure, temperature, heat and mass transfer characteristics have been studied. The steam pressure and water temperature have been kept in the range of 200–500 kPa and 20–60 °C, respectively. The maximum value of jet velocity and heat transfer coefficient have been found as 803 m/s and 2.73 MW/m2K respectively. The peak velocity value increases with steam pressure. After maximum expansion point, the velocity profile curve is shifted downstream with steam pressure. The axial pressure distribution first decreases and then increases from expansion-compression waves. The axial temperature profile followed the similar trend as observed for axial steam pressure distribution. At constant steam pressure, the maximum rate of heat transfer coefficient decreases with the increase in water temperature. The maximum mass transfer rate under prescribed flow conditions has been found as 2789.8 kg/m3s. The peak mass transfer rate decreases with steam pressure and water temperature. The peak rates for heat and mass transfer have been observed in the nearby vicinity of nozzle exit location.

Neural Network Prediction of Cooling Heat Transfer Characteristics of Supercritical R1234ze (E) in Horizontal Tube

The prediction of heat transfer coefficients or wall temperatures of heat exchanger tubes is an important research topic in supercritical heat transfer, which is extremely significant for the application of supercritical fluids in industrial production and the design of the entire thermal system. At present, the empirical correlation method is the most widely adopted prediction method, but there is still a significant difference between its predicted value of heat transfer coefficient and the actual data near the pseudo-critical temperature. Therefore, some scholars have proposed using artificial neural networks to predict the heat transfer performance of supercritical fluids in tubes. On the basis of previous researches, this paper further explores the effectiveness of artificial neural network in predicting supercritical heat transfer, focusing on the influence of input parameters on neural network prediction results and the influence of genetic algorithm optimization on the prediction results.<br>In this research, a neural network prediction model for supercritical R1234ze(E) cooled in horizontal straight tubes is established and compared with the modified D-B heat transfer correlation. The result shows that the input parameter has great impact on the prediction accuracy of BPNN, and not all BPNN input parameter combinations can bring better prediction results than heat transfer correlation. The combination of $\operatorname{Re}_b 、 P r_b 、 \rho_b / \rho_w$、$\bar{C}_p / C_{p w} 、 \lambda_b / \lambda_w 、 \mu_b / \mu_w$ 的预测表现最好，对于试验集的预测结果的AAD和Error<sub>max</sub> features the best prediction performance. The AAD and Error<sub>max</sub> of the prediction result for the trial set are only 2.02 % and 9.34 %, which are far lower than the prediction deviation of the heat transfer correlation, and the predictions of the trend of <i>h</i> in the high temperature region, the maximum value of <i>h</i> and the position of the peak value of <i>h</i> are more precise than correlation. Moreover, this research compares GA-BP model with BP model under two different fitness value calculation methods to reveal the effectiveness of GA-BP in enhancing the prediction accuracy of supercritical heat transfer. It concludes that, when the same dataset is adopted for network training and fitness value calculation, over-fitting will occur and the GA-BP cannot further improve the prediction accuracy; when different datasets are adopted for network training and fitness value calculation, the generalization ability of the network will be strengthened, the root mean square deviation and the maximum deviation of the prediction result can be further reduced.

Numerical simulation of aerodynamics in the cabin of transport

One of the most important tasks of transport engineering is the task of providing optimal and comfortable conditions for drivers and passengers, in particular: temperature, pressure, dust content, humidity, air speed, noise, illumination, etc. Temperature, humidity and vibration influences are also of great importance for the functioning of electronic devices and transport equipment. In this paper, a numerical-mathematical model is presented for studying the fields of temperatures, velocities, pressures, densities and humidity of air in the cabin space with simultaneous blowing by an external flow and internal ventilation. As a mathematical model, the Navier-Stokes equations in the RANS formulation are used, together with the diffusion equation, which allows calculating the mass fractions of water vapor in the domain. As a numerical implementation, the finite volume method is used together with turbulence models in the Ansуs Fluent software product. A non-stationary setting is considered, the stabilization time of flows is found; the stabilized fields are compared with the results obtained for the stationary setting. A method for obtaining numerical values of heat transfer coefficients for walls consisting of several layers of materials is also given. As a numerical experiment, a cabin of a special technological transport with a large glass area and multi- layered walls, with one driver without passengers, is considered. The obtained results are compared with the results obtained earlier without taking into account the diffusion equation and relative air humidity modeling.