Heat Characteristics Research Articles

Characteristics of heat, power generation, and energy efficiency study on a novel air-cooled PEMFC stack based on micro heat pipe arrays

This study introduces a novel kilowatt-scale air-cooled proton exchange membrane fuel cell stack utilizing micro heat pipe arrays (MHPA-PEMFC stack). This innovative stack design addresses issues commonly associated with conventional air-cooled fuel cell stacks, such as low heat transfer efficiency, suboptimal performance, and safety concerns, especially during high-load operations. In addition to the output performance of the stack, this study investigates the heat and power generation performance limits, operational security, and energy utilization efficiency of the MHPA-PEMFC stack under high power output and varying flow rates. The study introduces two novel evaluation indexes, namely, relative load gain (RLG) and relative safety gain (RSG), to provide a comprehensive evaluation. These indexes are utilized to link energy efficiency and exergy efficiency to the performance of the MHPA-PEMFC stack. The results show that the MHPA-PEMFC stack exhibits superior heat dissipation performance, uniform temperature distribution, and enhanced load capacity and safety compared with conventional PEMFC stacks. The maximum RLG and RSG achieved by the MHPA-PEMFC stack are 100% and 7.53, respectively. The energy efficiency of the MHPA-PEMFC stack surpasses 29% while maintaining a guaranteed maximum RLG. Notably, a higher RSG leads to a sacrifice in both energy and exergy efficiency.

Mathematical Modeling of Collisional Heat Generation and Convective Heat Transfer Problem for Single Spherical Body in Oscillating Boundaries

The application of high-energy ball milling in the field of advanced materials processing, such as mechanochemical alloying and ammonia synthesis, has been gaining increasing attention beyond its traditional use in material crushing. It is important to recognize the role of thermodynamics in high-energy processes, including heat generation from collisions, as well as ongoing investigations into grinding ball behavior. This study aims to develop a mathematical model for the numerical analysis of a spherical ball in a shaker mill, taking into account its dynamics, contact mechanics, thermodynamics, and heat transfer. The complexity of the problem for mathematical modeling is reduced by limiting the motion to one-dimensional translation and representing the vibration of the vial wall in a shaker mill as rigid boundaries that move in a linear fashion. A nonlinear viscoelastic contact model is employed to construct a heat generation model. An equation of internal energy evolution is derived that incorporates a velocity-dependent heat convection model. In coupled field modeling, equations of motion for high-energy impact phenomena are derived from energy-based Hamiltonian mechanics rather than vector-based Newtonian mechanics. The numerical integration of the governing equations is performed at the system level to analyze the general heating characteristics during collisions and the effect of various operational parameters, such as the oscillation frequency and amplitude of the vial. The results of the numerical analysis provide essential performance metrics, including steady-state temperature and time constant for the characteristics of temperature evolution for a high-energy shaker milling process with a computation accuracy of 0.1%. The novelty of this modeling study is that it is the first to obtain such a high accuracy numerical solution for the temperature evolution associated with a shaker mill process.

Heat and Mass Transfer Processes and Evaporation of a Liquid Droplet on a Structured Surface

The characteristics of water droplet heating and evaporation on structured hydrophobic and hydrophilic surfaces in the range of static contact angles from 73° to 155° were studied experimentally using high-speed video recording. Two fundamentally different technologies for applying coatings on a metal surface were used in comparison with the results on a polished surface. Microscopic studies were conducted to identify the features of the formed coatings. The wetting properties were characterized by means of the static contact angle and the contact angle hysteresis: on polished surface No. 1 (contact angle—73°, hysteresis—11°), on structured surface No. 2 (contact angle—125°, hysteresis—9°), and on structured surface No 3 (contact angle—155°, hysteresis—7°). The experimental dependences of the droplet evaporation rate on the different surfaces under normal conditions (ambient air temperature—293 K, atmospheric pressure, humidity—35%) were obtained. The evaporation regimes of droplets on the surfaces under study were identified. Water droplets evaporated in the pinning mode on surfaces No. 1 and No. 2. When a water droplet evaporated on surface No 3, the droplet was in the constant contact angle regime for ≈90% of its lifetime. Based on the experimental data obtained, a two-dimensional model of conjugate heat and mass transfer was developed, which describes the heating and evaporation of a liquid droplet on structured hydrophobic and hydrophilic surfaces at a wide range of contact angles. Satisfactory agreement was obtained between the numerical simulation results and experimental data. Using the model, the fields of temperature, concentration and other key characteristics were established at different points in time. Recommendations for its application in the development of gas–vapor–droplet applications were formulated.

Different characteristics of independent and compound extreme heat and ozone pollution events in the Greater Bay Area of China

Different characteristics of independent and compound extreme heat and ozone pollution events in the Greater Bay Area of China

Comparative analysis of heating characteristics of convective-radiant systems using various terminal air source heat pumps

The escalating demand for efficient heating solutions in hot summer and cold winter area has directed substantial attention towards convective-radiant combined systems. These systems offer enhanced comfort while conserving energy. In the context of office buildings, it becomes imperative to consider structural attributes. Under identical operational strategies, disparities in energy consumption and thermal comfort arise from variations in water supply temperature and terminal configurations. Here, we have established a dedicated laboratory to examine convective-radiant heating systems utilizing air source heat pumps. The primary objective is to analyze the impact of distinct heating terminal types and water supply temperatures on indoor thermal comfort, energy consumption, and energy efficiency. By analyzing the dynamics of indoor parameter, and interrelations among air temperature, average radiant temperature, operative temperature, and comfort levels, optimal strategies are determined. Empirical findings demonstrate that independently opening the Fan coil convection system (FC) leads to significant fluctuations in air temperature and creates an unstable heat environment. However, the Radiant floor system (RF) and Convective-radiant combined heating systems (FC + RF) exhibit superior stability in maintaining indoor air temperature. Compared among the three systems, while FC displays the lowest energy consumption upon activation, it compromises comfort levels. Remarkably, there is a strong relationship between operative temperature and Predicted Mean Vote (PMV) for the three systems, with high correlation coefficients of 0.998, 0.999, and 0.997, respectively. Conversely, the association between air temperature and PMV proves weak, with correlation coefficients of only 0.415, 0.469, and 0.841. Consequently, it is advised to prioritize operative temperature as the benchmark for winter air temperature control. For sustained adherence to Level II comfort zone criteria during indoor occupancy, it is recommended to employ (FC + RF) or RF for winter heating. Notably, energy savings of 26.87 %, 30.07 %, and 32.86 % are respectively achieved for (FC + RF), FC, and RF configurations when utilizing a water supply temperature of 35℃ as opposed to 45℃. Hence, the adoption of low-temperature water heating during winter is strongly advocated.

Study on the Performance of Phase-Change Self-Regulating Permeable Asphalt Pavement

Under low-temperature conditions in winter, asphalt pavement is prone to cracking, icing and other distresses, which affect its safety and comfort. Therefore, by incorporating phase-change materials into asphalt and conducting relevant performance studies, the aim is to alleviate low-temperature distress and regulate road surface temperature and expand the application of phase-change materials in asphalt pavement. We mixed the selected phase-change materials with different dosages into the matrix asphalt to prepare phase-change temperature-regulating asphalt and tested the four basic indicators: road performance, latent heat characteristics, temperature-regulating performance, and rheological properties of phase-change asphalt and its mixture. The research results indicate that with the increase in phase-change material content, the penetration, softening point, ductility, and dynamic viscosity of phase-change high-viscosity asphalt gradually increase. Under the constant temperature test conditions of −2.5 °C and −5 °C, the surface icing speed of asphalt binder specimens mixed with phase-change materials is slower than that of specimens without phase-change materials. Adding phase-change materials can improve the high-temperature and low-temperature PG grading of high-viscosity asphalt, effectively improving its high-temperature rutting resistance and low-temperature cracking performance. According to the temperature regulation test results, phase-change temperature-regulating asphalt has a certain regulating effect on temperature under low-temperature conditions, which can slow down the cooling rate of asphalt, reduce the thermal conductivity of permeable asphalt mixture by more than 50%, increase the temperature regulation rate by more than 30%, and improve the ice-melting and snow-melting ability by more than 20%. Phase-change materials have almost no effect on the porosity of permeable asphalt mixtures and can effectively improve the water stability, low-temperature crack resistance, and antiflying performance of permeable asphalt mixtures. Their Marshall stability and rutting stability decrease, but still meet the requirements of the specifications. Applying phase-change materials to permeable asphalt pavement can automatically adjust the temperature of the pavement, reduce the cooling rate of the asphalt pavement during cooling, alleviate the problem of snow and ice accumulation on the asphalt pavement in winter, and thereby improve the performance of permeable asphalt pavement against freeze–thaw cycles.

Thermal behavior and laser-induced heating characteristics of boron agglomerates in various atmospheric conditions

Thermal behavior and laser-induced heating characteristics of boron agglomerates in various atmospheric conditions

Conversion of polyethylene terephthalate (PET) plastic particles in a microwave-assisted heating reactor

Abstract With the rapid economic development, PET (polyethylene terephthalate) plastic is widely used in various fields, i.e., clothing, food, housing and transportation. However, PET has a very strong chemical inertia, which makes it difficult to be degraded by microorganisms, thereby occupying a lot of space. Therefore, the recycling of waste PET has become one of the most important topics of environmental protection. Glycolysis requires the most mild and safe reaction environment among chemical recycling methods, and the ethylene glycol used in the reaction can be reused. Using glycolysis to recycle PET undoubtedly conforms to the green and sustainable concept, and glycolysis recycling is undoubtedly a low-cost, low-consumption and low-harm path for PET recycling. The heating and glycolysis characteristics of microwave-assisted PET glycolysis, and the energy analysis of glycolysis were studied. The aim was to produce BHET (bis(2-hydroxyethyl) terephthalate) as the target product from PET waste. In this study, the effects of reaction temperature, reaction time, and PET particle size on the performances of PET conversion rate, oligomeric BHET yield, and BHET yield were examined, and the energy efficiency and recovery efficiency also were presented. The results showed that the optimal conditions for microwave-assisted PET glycolysis were reaction temperature of 180 °C, reaction time of 30 min, and PET particle size of 75 μm, and the maximum PET conversion rate was 66.71 ± 9.71 wt%, the maximum yield of BHET was 48.08 ± 0.68 wt% and the maximum BHET yield was 19.83 ± 5.40 wt%. The energy efficiency and recovery efficiency were 11.88 % and 17.89 %, respectively.

Numerical analysis of radiative hybrid nanomaterials flow across a permeable curved surface with inertial and Joule heating characteristics

The water-based Cu and CoFe2O4 hybrid nano liquid flow across a permeable curved sheet under the consequences of inertial and Lorentz forces has been reported in this analysis. The Joule heating and Darcy Forchheimer effects on fluid flow have been also examined. In the presence of copper (Cu) and cobalt iron oxide (CoFe2O4) nanoparticles, the hybrid nano liquid is synthesized. Radiation and heat source features are additionally incorporated to perform thermodynamics analysis in detail. The second law of thermodynamics is employed in order to estimate the overall generation of entropy. The nonlinear system of PDEs (partial differential equations) is transformed into a dimensionally-free set of ODEs (ordinary differential equations) by employing a similarity framework. The Mathematica built in package ND Solve method is applied to compute the resulting set of nonlinear differential equations numerically. Along with the velocity, and temperature profiles, skin friction and Nusselt number are also computed. Figures and tables illustrate the effects of flow factors on important profiles. Evidently, the outcomes reveal that hybrid nanofluid (Cu + CoFe2O4+H2O) is more progressive than nanofluid (Cu + H2O) and base fluid (H2O) in thermal phenomena. Furthermore, the velocity profile is improved with the greater values of curvature parameter, while the inverse trend is observed against the magnetic parameters. Also, the velocity and energy distribution of hybrid nano-liquid flow boosts with the inclusion of Cu and CoFe2O4 nanoparticles into the base fluid. Velocity distribution diminishes with the increment of volume friction. For high values of inertial factor, skin friction improve while velocity and Nusselt number declines.

Numerical Study on the Aerodynamic Heating Characteristics of the Cantilevered Injection System for Oblique Detonation Engine Inlets

This paper investigates the flowfield patterns and distributions of surface heat flux of the cantilevered injection system for oblique detonation engine inlets. Three-dimensional complex shock wave/boundary layer interaction and shock wave/shock wave interaction between injectors are studied by solving Navier–Stokes equations under laminar flow conditions. The results indicate that there are three possible positions of localized peak heat flux, i.e., the leading edge of the injector near the bottom, the inlet wall surface below the injector, and the downstream of the injector sidewall. All the regions of high heat flux are related to flow reattachment or stagnation. Three types of flow patterns are observed along the inlet surface, i.e., partial separation, completely regular separation, and completely nonregular separation, resulting in increasingly complex distributions of heat flux. The localized peak heat flux which appears at the leading edge and the sidewalls of the injectors can reach values dozens of times higher than the undisturbed region within the interaction region.

Forced convection heat transfer inside graphene aerogel

Ultralight heat-dissipating materials are essential for the effective thermal management of mobile devices. Graphene aerogel is a highly porous material made of thermally conductive carbon nanomaterial. Owing to aerogel's highly porous structure and graphene's high intrinsic thermal conductivity, graphene aerogel has a very low density and could be a promising ultralight thermal management material. In this study, forced convective heat transfer inside graphene aerogel is experimentally examined, and the effect of the aerogel microstructure on the heat and fluid flow characteristics of the graphene aerogel is discussed. It is established that graphene aerogel has a better convective heat transfer coefficient compared to conventional porous media. Furthermore, methods to improve the heat and fluid flow inside the aerogel are discussed. This work sheds light on the effective thermal management of various devices where lightness is critical.

Разработка математической модели анализа невозмущенного состояния теплоэнергетической гидравлической системы

The sequence of development of a model for analyzing the undisturbed state of a thermal power hydraulic system - a heat supply system, which is an important stage in the design and optimization of the system, is considered. The main parameters of the system are analyzed, such as thermal loads, heat flows, heat transfer through pipes and heat exchangers, location and characteristics of equipment (boilers, pumps, etc.). A mathematical model of the system has been developed, which should take into account all the main factors affecting heat transfer and the efficiency of the system. The model is presented in the form of a system of equations and includes parameters such as temperature, pressure, coolant flow, etc. Based on this model, it is possible to analyze various operating modes of the system, optimize parameters and make decisions to improve it. When developing the model, the possibility of various disturbances was taken into account. To analyze the unperturbed state of the system, the influence of such disturbances is excluded and its basic operation is considered. When developing a flow distribution analysis model for a heat and power system, energy equivalence was used. The developed model for analyzing the undisturbed state of a thermal power system will make it possible to more accurately design and control such a hydraulic system, improve its efficiency and reliability.

Study on CNT/TPU cube under the 3D printing conditions of infill patterns and density

In this study, to develop soft pressure sensor applicable to wearable robots using stretchable polymers and conductive fillers, 3.25 wt% carbon nanotubes/thermoplastic polyurethane filament with shore 94 A were manufactured. Three infill densities (20%, 50%, and 80%) and patterns (zigzag (ZG), triangle (TR), honeycomb (HN)) were applied to print cubes via fused filament fabrication 3D printing. Most suitable infill conditions were confirmed based on the slicing images, morphologies, compressive properties, electrical properties, and electrical heating properties. For each infill pattern, ZG and TR divided the layers into lines and figures, and the layers were stacked by rotation. For HN, the same layers were stacked in a hexagonal pattern. Consequently, TR divided layer in various directions, showed the strongest compressive properties with toughness 1.99 J for of infill density 80%. Especially, the HN became tougher with increased infill density. Also, the HN laminated with the same layer showed excellent electrical properties, with results greater than 14.7 mA. The electrical heating properties confirmed that ZG and HN had the high layer density, which exhibited excellent heating characteristics. Therefore, it was confirmed that performance varies depending on the 3D printing direction, and it was confirmed that HN is suitable for manufacturing soft sensors.

Significance of a permeable semi-circular body and magnetic field on the double-diffusive traits

This study delves into the occurrence of double-diffusive natural convection while being affected by a magnetic field within a cold square enclosure, containing a heated and concentrated semi-circular body made permeable. The fusion of both flat and curved boundaries, combined with the permeable attributes, stands as the central impetus driving this inquiry. The main aim is to scrutinize the impact of buoyancy force, permeability, magnetic field strength, and angle on the double-diffusive convection taking place inside and around the permeable structure. To achieve this, a comprehensive parametric investigation is undertaken, emphasizing the importance of Darcy number (Da), buoyancy ratio (BR), Hartmann number (Ha), and magnetic field angle (γM) in relation to the flow, heat, and concentration transfer. We utilize the Lattice Boltzmann method, incorporating the Darcy-Brinkmann-Forchheimer equation as a source term, to precisely address the complex flow within the porous medium. The results will provide insights into the importance of a semi-circular body with porous characteristics in the context of thermo-solutal convection influenced by magnetic effects. These findings hold practical significance in various applications, including electronic cooling, pollutant removal, and food processing industries. The inquiry discloses that elevating the buoyancy force, permeability, and the angle of the magnetic field leads to advantageous heat and concentration characteristics. Furthermore, positioning the magnetic force in opposition to gravity reduces the restraining impact of the magnetic force on the mean Nusselt number (NuM) and the mean Sherwood number (ShM). Remarkably, instances of unsteady behaviour are predominantly noted when the BR takes on a negative value, and these phenomena’s intensity and frequency are heightened by the Da and the γM. Remarkably, there are a few irregular spikes detected in the NuM and ShM, which can be attributed to the emergence of a strong singular vortex in the upper part of the enclosure.

Application of graded phase change materials for solar energy inter-seasonal storage heating and thermal storage characteristics

Abstract In this paper, firstly, the heat transfer characteristics of the stepped phase change accumulator are studied, and the location of the solid-liquid phase interface is determined by the phase fraction in a fixed grid scheme, while the phase change heat transfer process is simulated using Fluent. Secondly, for the phase change heat transfer problem, the enthalpy-porosity method in the Solidification/Melting model is used to treat the solid-liquid mixed paste region of the phase interface as a porous media region, and the evaluation system is constructed in terms of heat storage and discharge efficiency, heat storage, and heat recovery efficiency. Then the mathematical model, boundary conditions and solution parameters of the stepped phase change heat accumulator are set, and the data analysis of the effect of the pool height-to-diameter ratio on the heat storage in the solar inter-seasonal storage heating system is carried out by using ANSYSCFD software. The results show that the heat storage of the system also shows an overall increasing trend with the increase of the pool height-to-diameter ratio, and the heat storage of the system increases faster when the height-to-diameter ratio increases from 0.2 to 1.0 in sequence, and the heat storage of the system increases less when the height-to-diameter ratio changes between 0.9 and 1.8, and basically tends to be stable. This study realizes the graded heat storage and graded heat use of solar energy, which is useful for the research of solar heat supply and heat storage.

Light-induced pure spin current in carbon hexagonal-connected zigzag graphene nanoribbons via magnetic field modulation.

Pure spin current, exhibiting no Joule heat and self-powered characteristics, has recently attracted intensive attention. Here, through first-principles calculations and symmetry analysis, we propose a new method to generate photoelectric pure spin current in carbon hexagonal connected three zigzag graphene nanoribbons (ZGNRs) via magnetic field modulation. Specifically, a device with centro-symmetry is designed, which consists of three ZGNRs using two carbon hexagons as connectors ('2-C6'). When the edge spin states of the three ZGNRs from left to right are modulated to AFM-AFM-AFM or FM-AFM-FM by magnetic fields, excellent pure spin currents are obtained which are independent of the photon energy and the angle of the linearly polarized light. However, when the edge spin states are FM-FM-FM orderly, the photocurrent is nearly zero and can be neglected. Analysis show that the first two spin magnetic structures own the spatial inversion antisymmetric spin density which is the origin of stable pure spin currents, while the FM-FM-FM structure owns Cs symmetric spin density, leading to the nearly zero photocurrent. Our findings provide a scheme for obtaining pure spin currents by changing the spin states of the graphene nanoribbons via magnetic field modulation, which is of great importance for the design of spintronic devices.

Magnetohydrodynamic Analyses of a Miniature, Dual-Stage Electromagnetic Pump for Lead and Sodium In-Pile Test Loops

To support the development of Generation IV nuclear reactors, in-pile and out-of-pile test loops with miniature, submersible Direct-Current Electromagnetic Pumps (DC-EMPs) are used to investigate compatibility and corrosion issues of nuclear fuel and structure materials with flowing molten lead and alkali liquid metals. Owing to the absence of detailed experimental measurements and because of its simplicity and low computational cost, the Equivalent Circuit Model (ECM) is widely used to predict the pump characteristics. The simplifying assumptions in the ECM contribute to overpredicting the pump characteristics by >10%. To gain insight into the pump operation and assess the effect of various assumptions in ECM, not possible even experimentally, this work performed three-dimensional (3-D), Magneto-Hydro-Dynamic (MHD) analyses of a 66.8-mm-diameter, submersible, dual-stage DC-EMP, recently developed by the authors, for circulating molten Pb and liquid Na at up to 500°C. The solution of the coupled electromagnetism equations and the momentum and energy balance equations calculates the pump characteristics and provides 3-D images of the flow, electric current, and magnetic field strength distributions in the flow duct. The Grid Convergence Index (GCI) criterion confirmed the adequacy of the employed numerical mesh refinement and the results conversion. Results demonstrate strong dependence of the magnetic field strength distribution in the flow duct on the value and the distribution of the electric current but negligible effects of the fluid temperature on joule heating and pump characteristics. The Lorentz force highest densities occur at the entrance of the two pumping stages, and approximately 10.0% of the total force occurs in the fringe regions upstream and downstream of pumping stages. The MHD pump characteristics are in general agreement with, but consistently lower than, the ECM predictions. For molten lead and liquid sodium, the difference between the calculated characteristics increases with increased flow rate and input current, up to 12% and 14%, respectively.

Investigation of the thermal response characteristics of the loop thermosyphon under convective boundary conditions

The two-phase loop thermosyphon (TPLT) is a highly efficient passive heat transfer device that is widely applied in various fields. This paper experimentally and numerically investigates the thermal response performance of a large-scale TPLT under various convective boundary conditions. Experimental studies have been carried out to explore the effects of different working fluids, filling ratios, cold and heat source temperatures, and mass flow rates on the thermosyphon’s performance. Meanwhile, a two-dimensional Computational Fluid Dynamics (CFD) simulation model of the TPLT is established and validated. The results indicate that the start-up procedure of the TPLT is highly dependent on the heat source temperature and the working fluid. Normally, the TPLT can start when the heat source reaches a certain temperature. In general, using methanol as the working fluid is more favorable to start-up compared to the water and ethanol TPLTs. The experimental results also show that the heat transfer capacity of the TPLT increases with increasing heat source temperature while increasing cooling temperature decreases heat transfer capacity. The best heat transfer performance of a TPLT charging methanol is observed at a filling ratio of 70 % with a heating mass flow rate of 1 L/min. At that point, the convective heat transfer coefficient of outside the evaporator is 1036.7 W/(m2·K). Moreover, the simulation results reveal that the average wall heat flux of the TPLT’s evaporator initially decreases and then gradually stabilizes with time. During stable operation, the wall heat flux density of the evaporator exhibits an initial increase in the pool section followed by a subsequent decrease with increasing wall height. This work provides insight into the heat and fluid flow characteristics of the TPLT under convective boundary conditions.

Some problems related to thermophysical properties of selected barrel steels

The paper discusses selected issues related to the thermophysical properties of selected barrel steels, which the authors have been dealing with over the last few years, i.e. 38HMJ (1.8509), 30HN2MFA, X37CrMoV5-l hot-work tool steel (1.2343), DUPLEX (1.4462) and MARAGING 350 (1.6355). In some of them, i.e. in the X37CrMoV5-1 hot work tool steel, 38HMJ, 30HN2MFA, a ferrite-austenite phase transition occurs, which causes shrinkage of the material. During a series of shots, multiple shrinkage of material degrades the barrel channel and deteriorates the ballistic parameters of the cannon barrel. Another problem concerns the apparent specific heat that we get from the DSC measurement and the dependence of the specific heat on temperature in the form that we use for the numerical simulations. The point is that the phase transition effect should not be taken into account twice, i.e. in the thermal diffusivity characteristics and in the specific heat characteristics. For all selected steels the thermophysical properties, i.e. thermal diffusivity, thermal conductivity, specific heat and thermal expansion, were obtained in a wide range of temperature, so they can be used as input data for numerical simulations.

Uniform/Selective Heating Microwave Oven Using High Efficiency GaN-on-GaN HEMT Power Amplifier

A high-efficiency uniform/selective heating microwave oven was developed. Because the power amplifier requires high-efficiency characteristics to function as a microwave source, a free-standing Gallium Nitride (GaN) substrate was applied in this study. By applying a harmonic tuning circuit, an output power of 71 W and PAE of 73% were achieved in pulsed operation, and an output power of 63 W and PAE of 69% were achieved in CW operation. Moreover, we fabricated a prototype PA module that consists of an oscillator, a driver amplifier, PA, and other RF circuits. The output power was controlled by pulse width modulation to maintain high efficiency regardless of output power. We evaluated the arrangement of antenna polarizations to isolate each antenna. By suppressing the interference of output from adjacent antennas, it is possible to irradiate the object on the top surface of the antenna, thereby demonstrating heating characteristics with small temperature unevenness. The prototype microwave oven successfully demonstrated uniform/selective heating.