Surface Convective Heat Transfer Coefficient Research Articles

Performance analysis and optimization of the Gyroid-type triply periodic minimal surface heat sink incorporated with fin structures

The Triply Periodic Minimal Surface (TPMS) structures demonstrate substantial value and development potential in applications and research concerning heat sinks and heat exchangers. To further enhance the convective heat transfer performance of TPMS, this study proposes a novel method of incorporating fin structures into TPMS. This method is applicable to various types of TPMS, and the new structure constructed using this method is termed “TPMS with Fin Structures (TFS).” Subsequently, a TFS-Gyroid heat sink based on the Gyroid-type TPMS was constructed. This study presents a calculation method for the fin height in TFS-Gyroid (HTFS-Gyroid). Numerical simulation methods were employed to investigate the influence and mechanism of HTFS-Gyroid on the convective heat transfer performance and flow resistance of the TFS-Gyroid heat sink model, with air as the working fluid and under constant wall temperature (100 °C) conditions. The results indicate that within the flow range of 24–120 L/min, as HTFS-Gyroid increases from 0 to 1.6 mm, the average surface convective heat transfer coefficient (h̅) of the TFS-Gyroid heat sink model increases by 27.4 %-34.6 %, and the inlet–outlet pressure drop (ΔP) increases by 42.5–632.8 Pa. As HTFS-Gyroid increases, the PEC of the TFS-Gyroid heat sink model gradually decreases, whereas j/f gradually increases. The primary mechanisms by which the fin structures enhance the convective heat transfer performance of the TFS-Gyroid heat sink are: 1) increased heat exchange area, 2) the fin structures induce a large number of longitudinal vortices and secondary flows within the flow channels, and 3) the formation of “Fins Occupying the Perforated Structure (FOPS)” within the flow channels.

A similarity method to correct cooling effectiveness from a scaled turbine blade experiment

The cooling effectiveness of a turbine blade is conventionally validated through scaled model experiments which involve the challenge of thermal similarity. To ensure accurate prediction of cooling performance in a real engine, it is necessary to investigate the dimension scaling effect and establish a reliable correction method for the cooling effectiveness obtained from the experiment. This paper presents a novel method derived from a one-dimensional heat transfer model to correct the scaling effects on thermal similarity. A group of experiments with a dummy blade is conducted to verify the feasibility and accuracy of the correction method. Results show the dissimilarity between scaled articles due to geometry dimension, material thermal properties, and alignment of the thermal barrier coating. A down-scaled model has higher cooling effectiveness than its full-length counterpart because of the enhanced internal convective heat transfer and reduced external surface heat transfer. In addition, dissimilarity due to mismatched heat conductivity of blade material and surface convective heat transfer coefficient can be corrected using Biot number replacement. Misalignment of thermal barrier coating can be replaced by a pseudo-blade metal of equivalent heat resistance and wall thickness including the metal and coating layer. Experimental result from a scaled model is corrected to improve the prediction accuracy of its full-length performance. Corrected cooling effectiveness matches its prototype within an uncertainty of 10 %. The present method is applicable to evaluate gas turbine components by means of scaled model experiments.

Key Parameters and Experimental Study of High-Speed Rotating Meshing Gear Injection Lubrication Based on Moving Particle Semi-Implicit Method

With the rapid development of China’s manufacturing industry, products are changing toward better energy efficiency and precision. Reducing transmission energy waste, enhancing transmission lubrication, and increasing transmission efficiency have all become critical concerns. The moving particle semi-implicit particle approach is utilized in this study to create a high-speed rotating meshing gear lubrication model and conduct a simulation analysis of transmission gears by studying the influence law of sensitive parameter injection diameter on lubrication. The oil distribution state on the gear surface, the gear tooth surface heat dissipation effect, and the degree of gear operating stability are all calculated by computing the gear surface fluid coverage and convective heat transfer coefficient. According to the numerical simulation results, increasing the liquid injection diameter can greatly enhance fluid coverage and convective heat transfer coefficient on the gear surface, hence improving lubrication. However, when the injection diameter reaches a critical value, the contact area between the liquid and the gear is maximized, and additional increases in the injection diameter will not improve the lubricating effect. Experiments have revealed that the liquid injection diameter is the most critical factor influencing gears. The gear torque dramatically increases as the liquid injection diameter increases. According to a rigorous analysis, the gear lubrication effect is optimal when the liquid injection diameter is 2.0 mm. This provides a theoretical foundation for transmission system lubrication design.

Wall-resolved versus wall-modeled LES of the flow field and surface forced convective heat transfer for a low-rise building

Large eddy simulation (LES) is widely used to investigate the aerodynamics and convective heat transfer (CHT) at the surfaces of sharp-edged bluff bodies for a wide range of Reynolds (Re) numbers. Due to the heavy computational costs associated with implicit filtering in LES at high Reynolds number flows (Re ≥ 105), wall-modeled (WM) rather than wall-resolved (WR) LES is often adopted. However, the performance of LES-WM for such applications has not yet been systematically investigated. Therefore, this study evaluates the performance of LES-WM and LES-WR for the flow and thermal field at the facades of a low-rise building immersed in an atmospheric boundary layer. Four grids are constructed for LES-WM, each employing different resolution at the building surfaces reaching maximum non-dimensional wall distance y+ = 43, 57, 70, and 95. In addition, the performance of two wall functions, namely the Werner and Wengle and the enhanced wall function is investigated. The results show that the use of LES-WM can result in significant deviations in the predicted near-facade flow pattern and the surface convective heat transfer coefficient (CHTC). Grid resolution significantly impacts the CHTC results and deviations go up to 88% (at the base of the windward facade). Considerable deviations among the employed wall functions are apparent only on the finest grid. In this case, the implementation of the enhanced wall function indicates better performance compared to the non-blended law of the wall (combined with the Werner and Wengle) for CHTC in the regions of the leeward facade where the flow remains attached to the wall. The deviation of the enhanced wall function for surface-averaged CHTC is found to be 10.8% against the wall-resolved LES results, while for the non-blended law of the wall this is 19.2%.

Unified formulation of convective heat flux and mass flux vectors with thermodynamic coupling and related transfer coefficients

Based on the inherent thermodynamic relations of compressible species in binary mixtures at constant pressure, the general three-dimensional (3D) convective heat flux and mass flux vectors are formulated including the contributions of simultaneous advection, thermal diffusion and mass diffusion and their coupling effects between temperature and concentration gradients. The novel expressions for the diffusion-thermo and thermo-diffusion effects do not require the meager data of thermal diffusion ratio and are valid for both gas and liquid mixtures in laminar flows. The unified flux forms of the Maxwell's electromagnetic equation type are obtained in convective processes. It is further shown that the surface convective heat and mass transfer coefficients can be expressed in terms of the convective heat fluxes and mass fluxes away from surfaces in steady laminar flows, and that the expression of each transfer coefficient yields the identical form on both impermeable and permeable surfaces.

Characterization of the Nozzle Ablation Rate Based on 3D Laser Scanning System

The nozzle of solid rocket motor (SRM) is easily ablated by high temperature, high pressure, high speed, and corrosive particles, which affects the stability of rocket flight. Therefore, the measurement and characterization of the nozzle ablation rate are helpful in providing some guidance for the design of nozzle material and structure. However, due to the high surface roughness of the composite nozzle after ablation, it is difficult to obtain an accurate ablation rate by contact measurement methods. The 3D laser scanning system is a 3D non-contact measurement technology using structured light technology, phase measurement technology, and computer vision technology. It has the advantages of non-contact, large scanning size, flexibility, and portability. In this paper, a 3D reconstruction of the ablation nozzle is carried out based on the 3D laser scanning system. Additionally, the ablation rate of the nozzle is measured without cutting the actual specimen. Furthermore, the pressure, temperature, and surface convective heat transfer coefficient trends are numerically calculated and compared with the ablation rate. Additionally, the empirical formula between ablation rate and pressure, temperature, convective heat transfer coefficient is obtained empirically by the inversion analysis method. The empirical formula can provide theoretical guidance for nozzle size design and optimization. The results show that the non-contact 3D laser scanning system is a valuable method for reconstructing the model of the ablated nozzle, and the empirical formula of ablation rate can accurately predict the ablation rate of the nozzle.

Analysis on convective heat transfer coefficients of external surfaces for typical building arrays

Urban architecture has a great impact on the flow field among buildings, leading to the varying of building surface convective heat transfer coefficient (CHTC), which then influences heat exchange and heating/cooling energy consumption. This paper proposes a method to correct CHTC with a shelter factor by analyzing the effect of mutual shielding among buildings. The characteristic data of 51 green energy-saving residential buildings in China are collected, then classifies with the K-means method to get typical building arrays. CFD simulations are used to compare the CHTC ratios of buildings in a typical building array with those of individual buildings at different wind speeds. The shelter factor of CHTC in building arrays is obtained. The CHTC of buildings in different arrays is 24%–77% of a single building. Different types of building arrays show different CHTC characteristics. The energy consumption of a building among building arrays, calculated with corrected CHTC, is further compared with the value of a single building. The results show that the greater the building wall heat transfer coefficient is, the greater the influence of the shelter factor on building energy consumption.

Convection heat transfer coefficient of building glasses under salt deposition conditions

Glass buildings in coastal regions and islands exposed to the hydrothermal marine environment, in addition to salt deposition and erosion, lead to a change in the surface convective heat transfer coefficient (CHTC) and gradual degradation of the building energy and thermal performance. However, limited research has been conducted on the influence of salt deposition on the CHTC of building glasses. Hence, in this study, the salt deposition characteristics of the glasses were obtained by conducting an accelerated salt spray test. In addition, the influence of salt deposition on the CHTC and heat transmission coefficient (HTC) was investigated. The results indicate that the sizes of the salt spots on the glass surface increased significantly and unevenly. The salt deposition per unit area (p) exhibited a logarithmic growth trend between 14.4 and 40.0 mg/m2, considering the spray time. Under the 10% saline condition, p was larger than that under the 5% saline condition, ranging between 15.6 and 44.3 mg/m2, with an average increase rate of 11.6%. The CHTC exhibited a monotonic increase in terms of the deposition amount on the glass. Compared with the salt-free scenario, the maximum increase in CHTC was 178.7%, which exhibited a linear relationship with p. When p increased to 40.0 mg/m2, the HTC increase rate of the single clear glass and hollow Low-E glass reached 20.1% and 5.2%, respectively. The findings of this study provide insights into the influence of salt deposition on the CHTC of building glasses and can serve as a basis for energy consumption studies in coastal regions.

Overall Heat Transfer Coefficient Evaluation Method for Uncracked Hydrocarbon Fuel in a Regeneratively-Cooled Heat Exchanger of a Scramjet

Regenerative cooling is critical for the thermal protection of hypersonic propulsion systems, wherein the flow and heat transfer characteristics of the hydrocarbon fuel in the cooling channel are crucial. Restricted by measurement, the distribution of the fuel temperature inside the cooling channel cannot be directly detected. As a result, the measurement of the convective heat transfer coefficient is more an overall heat transfer coefficient. Furthermore, the existing overall heat transfer coefficient calculation method is derived without considering the flow state of the hydrocarbon fuel in the cooling channel, which should be taken into consideration. Therefore, a modified calculation method of the overall heat transfer coefficient is proposed in this study. The results of the characteristics of the turbulence-related parameters show that the overall heat transfer coefficient is mainly determined by the effective thermal conductivity and surface convective heat transfer coefficient, which are related to the fuel temperature and flow state. Furthermore, the existing method might overestimate the overall heat transfer coefficient. The modified method is suitable for the calculation of the overall heat transfer coefficient in the heat transfer enhancement process in a cooling channel.

Comparison and evaluation of supercritical CO 2 cooling performance in horizontal tubes with variable cross‐section by field synergy theory

The cooling/heating performance improvement of supercritical carbon dioxide (sCO2) in heat exchange tube with changing cross-section is significant and crucial for solar-driven advanced thermal systems' application and development. The study introduced and constructed straight, diverging, and converging horizontal tubes with the changing cross-section. The analyzation and evaluation of the sCO2 cooling performance used the combination of SST k-ω turbulence model-based numerical method and the field synergy theory, including the influence of tube cross-sectional shape, inlet pressure and temperature on the cooling performance. As these simulation results indicate, the converging tube can enhance the flow field's synergy and increase the heat transfer ability by 13.15% under cooling conditions. Nevertheless, the heat transfer ability of the sCO2 decreases in the diverging tube under cooling conditions. Besides, the total heat transfer rate rises and the surface heat transfer coefficient has the opposite trends when the inlet temperature increases. Meanwhile, when inlet pressure varies from 11 to 12 MPa, the total heat exchange and surface convective heat transfer coefficient are the maximum. In conclusion, a converging horizontal tube and a suitable inlet pressure can effectively improve the cooling performance of the sCO2. The converging cross-section design will provide an alternative for its application in advanced thermal systems.

Efficiency and sustainability assessment of evaporative cooling of photovoltaics

The cooling of PV has been shown to increase electricity production. Among passive techniques, evaporative cooling has one of the greatest potentials. In this work, the efficiency and sustainability of this technique have been investigated for various climatic conditions. In-situ experiments were conducted to develop parametric models for PV cell temperatures and back surface convective heat transfer coefficient. Experiments have revealed an up to 20.1 °C lower peak PV temperature and up to 9.6% increased electric power. Year-round analysis was made for eight cities to determine the required roof size to capture precipitation and the volume of rainwater storage for sustainable evaporative cooling. The study shows that sustainable PV evaporative cooling is possible in cities with temperate and continental climates, where 1–3 m2 of roof area and 50–150 l of rainwater storage are needed for 1 m2 of PV. The annual electricity production can increase by 5.9–9.4 kWh/m2a, which is a 3.6–4.6% increase. In the semi-arid climate of Lampedusa, a roof above 4 m2 and a storage of up to 500 l per m2 of PV are required. In the desert climate of Almeria and Athens, sustainable evaporative cooling is not feasible.

Study on Aerodynamic Performance and Lightweight Multiobjective Optimization Design of Wheel With Entropy Weighted Grey Relational Analysis Methods

In order to improve the aerodynamic performance and optimization efficiency while wheel lightweight designing, a multi-objective optimization design method of wheel lightweight based on entropy weighted grey relational analysis (EGRA) was proposed in this article. The aerodynamic analysis finite element model of the assembled wheel was established, and the simulation accuracy was verified by experiments. Study the distribution law of performance parameters such as pressure and turbulent kinetic energy in flow field of the car, analyze the variation law of flow field velocity and turbulent intensity in front and rear wheel cavities of the assembled wheel, and analyze the cloud diagram distribution of temperature and surface convective heat transfer coefficient of the brake disc ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h_c</i> ). Research on the influence of wheels with different disc structures on the aerodynamic drag coefficient of the car ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C_d</i> ) and the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h_c</i> . Combined with grey relational analysis (GRA) and EGRA, the objective evaluation of the comprehensive aerodynamic performance of wheels with different disc structures was given. With the design of experiments (DOEs), 12 important design variables were screened out by contribution analysis method. Using the approximate model method, combined with the RBF surrogate model, a hybrid method combining EGRA and Non-Dominated Sorting Genetic Algorithm-II (NSGA- II) was proposed to lightweight and multi-objective optimize the assembled wheel. Comparing and analyzing the optimization platform recommending scheme, the technique for ordering preferences by similarity to ideal solution (TOPSIS) method preferring scheme and the EGRA method optimum scheme, it was found that the optimal compromise scheme was obtained by the EGRA method, the reduction of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C_d</i> was more obvious, and the improvement rates of performance were also more balanced. After multi-objective optimization, the mass of the assembled wheel was reduced by 10.83%, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C_d</i> was reduced by 3.47%, and the average convective heat transfer coefficient of brake disc ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h_a</i> ) was reduced by 8.02%. The optimized assembled wheel has a weight reduction of 32.74% compared with the same type of cast aluminum alloy wheel, which has a remarkable lightweight effect and significant reduction on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C_d</i> .

USE OF CORRUGATED PIPE HEAT EXCHANGERS IN WASTE HEAT RECOVERY STEAM GENERATORS

Heat exchangers are used for a variety of purposes in various domestic, commercial& industrial applications. Some common examples are sensible heating & sensible cooling in chemical processes, condensation and steam generation in power plants, and recovery of waste heat etc. Heat exchangers performance enhancement can lead to more economical design of heat exchanger which increases energy, material & cost savings related to heat exchange process. Making corrugation on pipe surface is one such method. Numerous works has been carried out in this area, where parameters such as inside diameter of pipe, corrugation pitch, corrugation depth, temperature and phase of liquid has been studied. Corrugation of tubes can increase both the inner and outer surface convective heat transfer coefficient without any considerable rise in pressure drop. It also results in increase in mixing of fluid, flow turbulence, unsteadiness by limiting the fluid boundary layer growth adjacent to the tube surface.

Experimental investigation of convective heat transfer for night cooling with diffuse ceiling ventilation

The convective heat transfer coefficient (CHTC) is a crucial parameter for night ventilation performance estimation. This paper investigates the heat transfer of night ventilation with diffuse ceiling ventilation (DCV) concept in an office room. A series of dynamic full-scale experiments were conducted with different thermal mass distribution schemes, air change rates per hour (ACH), and supply temperatures. The CHTC at interior surfaces with the inlet and outlet temperatures as the reference and the temperature efficiency of DCV were then derived. In most cases, the experimental CHTCs differed significantly from the CHTCs predicted by existing correlations. The presence of furniture (tables), its location, and the thermal mass installed on the walls had little influence on the CHTC at the floor. However, increasing the thermal mass of one surface can significantly augment its own surface CHTC. New correlations based on experimental CHTCs were developed for potential application in building energy simulation tools. The temperature efficiency of DCV decreased with the increase of ACH, the initial temperature difference between the supply air and indoor air, and the thermal mass level. DCV had higher temperature efficiency than the mixing ventilation and displacement ventilation, except for the case with displacement ventilation at low ACH.

A field study on Ground Energy Balance calculation for typical communities in South China

Urban heat island (UHI) greatly influences human health, comfort and building energy. The ground temperature plays an important role in understanding UHI, and the method based on the ground energy balance (GEB) is fundamental in the predictions of urban ground temperature and UHI. South China is fast developed and highly urbanized, with special humid subtropical climate and particular urban design characteristics. Although amounts of methods or formulas have been previously proposed for urban GEB calculation, few of them has been testified in field in South China. In this study, two typical urban communities in South China in the aligned and enclosed layout were measured during the summer sunny days in Aug. 2017, with the focus on incident solar radiation, sensible heat, and latent heat of the ground. The measured data were compared with the calculated ones by various methods. The results show that the two calculation methods, i.e., with and without reflections, showed comparable performances (difference on RMSE 3-13 W/m2) in the prediction of solar radiation incident into the community ground. The previously proposed formulas performed poorly in the prediction of surface convective heat transfer coefficient for the community hard pavement, and the power function regressed by using the measuring data performed well, with the air speed at the reference height of 0.13 m as variable and R2 of 0.74. The Bowen ratio method performed better in the prediction of latent heat for the community permeable sidewalk, with RMSE of 156 W/m2 and the consistency index of 0.93. This study provides the field evidences and reliable methods for urban GEB calculation, and potentially contributes to the UHI prediction and mitigation in South China.

Influence of PCM thermal conductivity and HTF velocity during solidification of PCM through the free cooling concept – A parametric study

Abstract The thermal performance of a latent heat thermal energy storage (LHTES) system can be enhanced by incorporation of fins, metal matrices, lessing rings in the phase change material (PCM) encapsulation and by dispersion of high conductive nanomaterials in the PCM itself. Similarly, to increase the heat transfer to PCM, the surface convective heat transfer coefficient (‘h’) can be enhanced by increasing the heat transfer fluid (HTF) velocity (‘u’). However, it is important to know how much increase in PCM thermal conductivity (‘k’) and ‘h’ will be beneficial during the charging of PCM under real-time ambient conditions and when will we reach the margin of diminishing returns. Understanding these are the motivation of the present work which includes the parametric study of the impact of ‘k’ & ‘u’ on the charging of PCM (RT28HC) through free cooling concept under different operating conditions (two different HTF inlet temperature). The numerical results are validated using the experimental data and they both show good agreement with each other. The major inferences from the results are, i) increasing the PCM thermal conductivity reduces the charging duration of the LHTES system for both lower and higher HTF velocity (1 m/s and 8 m/s). However, reduction in charging duration while increasing ‘k’ is higher when the HTF inlet temperature is lower, ii) increasing the HTF velocity is beneficial only when the inlet HTF temperature is higher. For the case of lower HTF inlet temperature, the effect of increasing the HTF velocity is suppressed by the higher temperature driving potential between the HTF inlet temperature and the PCM phase change temperature. It is inferred from the parametric study that, among the three parameters considered (PCM thermal conductivity, HTF velocity, and HTF inlet temperature), HTF inlet temperature has the most influence on the charging of the PCM, followed by the PCM thermal conductivity and HTF velocity.

A novel initial temperature-based methodology to predict the optimal thickness in microwave thin layer drying process

Abstract Compared with traditional hot air drying method, the existence of optimal material layer thickness is a significant phenomenon in microwave thin layer drying process. In the current work, a new initial temperature-based methodology is proposed to predict the optimal thickness and to evaluate the effect of influential factors on optimal thickness. The evaluated optimal material layer thickness by the proposed methodology is consistent with experimentally measured value, and hence confirms that the optimal layer thickness can be predicted exactly through the average temperature of bulk material at the initial 1st min during pre-heating stage. With the help of the proposed methodology, it is discovered that attenuation factor, β, surface convective heat transfer coefficient, h, and environmental air temperature, T e are the main factors that affect the optimal thickness. And a larger β or T e tends to result in a smaller optimal thickness, while the situation for h is just the opposite. These results can play a crucial role in designing apt continuous microwave tunnel drying system or aid in guiding their operations.

Heat dissipation from a stationary brake disc, Part 1: Analytical modelling and experimental investigations

The main aim of the research is to support the development of the commercial vehicle electric parking brake. Though nowadays widely used on passenger cars, electric parking brake applications on commercial vehicles present completely different challenges. With the brake mass, thermal capacity and required clamp forces an order of magnitude higher, safe parking demands much more attention. In the first instance, the priority is placed upon predicting heat dissipation from the brake disc only. The research is presented in two parts; part one (presented here) focuses on analytical modelling and experimental verification of predicted disc temperatures over long cooling periods, with part two investigating the air flow, velocities and convective heat transfer coefficients using computational fluid dynamics modelling, also followed by experimental validations. To begin the analytical analysis, a study was conducted into the variance in mean local convective heat transfer coefficients over a simplified brake disc friction surface, by investigating typical dimensionless air properties. A nonlinear equation was derived for the average surface convective heat transfer coefficient ([Formula: see text]) variability with temperature drop for the entire cooling phase. Starting from fundamental principles, first-order differential equations were developed to predict the bulk disc temperature. By including variation of the convective and radiative heat dissipation throughout the cooling period, a good correlation was achieved with measured values, to within 10%. Experiments were conducted on a specifically designed thermal rig which uses 15 kW induction heater to heat the disc. Numerous experiments proved the results are very repeatable, throughout the cooling period. It was established, for the grey cast iron brake disc with a fully oxidised surface, the emissivity value are practically constant at ɛ = 0.92. Although the research is being conducted on a brake disc, the results have generic application to any disc geometry, whatever the application.

Empirical mapping of the convective heat transfer coefficients with local hot spots on highly conductive surfaces

An experimental method was proposed to assess the natural and forced convective heat transfer coefficients on highly conductive bodies. Experiments were performed at air velocities of 0m/s, 4.0m/s, and 5.4m/s, and comparisons were made between the current results and available literature. These experiments were extended to arbitrary-shape bodies. External flow conditions were maintained throughout. In the proposed method, in determination of the surface convective heat transfer coefficients, flow condition is immaterial, i.e., either laminar or turbulent. With the present method, it was aimed to acquire the local heat transfer coefficients on any arbitrary conductive shape. This method was intended to be implemented by the heat transfer engineer to identify the local heat transfer rates with local hot spots. Finally, after analyzing the proposed experimental results, appropriate decisions can be made to control the amount of the convective heat transfer off the surface. Limited mass transport was quantified on the cooled plate.

Modelling of heat and mass transfer during cooking in steam-assisted hybrid oven

Semitendinosus muscle in a cylindrical shape was cooked in a domestic steam-assisted hybrid oven, and the simultaneous heat and mass transfer during the cooking process was modelled using commercial software COMSOL Multiphysics (version 3.5a). The temperature and moisture profiles of the product were predicted as functions of both position and time, and the predicted results were compared with the experimental ones. The surface convective heat transfer coefficient was determined experimentally using the lumped capacity method, and the surface convective mass transfer coefficient was calculated by simulation of the developed model at different temperatures. Also, the thermal conductivity of muscles was determined as a function of the temperature and moisture content by the line heat source method. The convective heat transfer coefficients were found to be in the range of 17.31–18.35 W/m2K, and the calculated surface convective mass transfer coefficients were in the range of 1.7 × 10−7-2.2 × 10−7 m/s at 180, 210 and 240 °C cooking temperatures. The predicted results for the steam-assisted hybrid cooking process agreed well with the experimental temperature and moisture profiles, and the developed model is considered to be suitable for predicting cooking times in a steam-assisted hybrid oven.