Electromagnetic simulation and experimental analysis of microwave heaters for asphalt pavements

In order to study the thermoelectric efficiency of microwave heating and reproduction of asphalt pavements and the uniformity of reproduction temperature distribution, a waveguide excitation cavity is designed and applied to the structural design of a microwave heater. The structural sizes of the incentive cavities are determined based on the waveguide transmission line theory. Using IE3D software, electromagnetic simulations are respectively carried out in four different situations, including the distances between the magnetron probes （antennas） and a short-circuit board, different horn electric lengths and aperture sizes, different dielectric properties of the asphalt mixture, and the distances between the asphalt surface and the mouth cavity. The results show that, when the distance between the magnetron probe and the short-circuit board is 32.5 ram, it is the best installation site; reduction of aerial length is the main factor in improving the heating uniformity. When the aggregate is limestone, the best heating effect can be produced. Maximum radiation efficiency can be realized by adjusting the space between the heater radiation port and the asphalt pavement. The experimental results of asphalt mixture heating in four different situations have a substantial agreement with the simulation results, which confirms that the developed microwave heater can achieve better impedance matching, thus improving the quality and efficiency of heating regeneration.

Effect of obstruction on thermal performance of solar water heaters

Solar water heaters(SWH) are widely used in urban areas because of their advantages in reducing energy consumption and mitigating greenhouse gas emissions. However, the performance of SWH subjected to obstructions is unclear yet. In this study, we present a numerical evaluation on thermal performance of fa?ade-installed SWH under three typical obstructed scenarios, based on various levels of sunshine duration. This study is carried out for four locations with various latitudes across China. Thermal performance is measured by solar fraction for annual and monthly evaluation. The results show that the obstruction can seriously degrade annual solar fraction of SWH, even in the 4-hour sunshine duration scenario, for all the studied locations. Interestingly, only lengthening sunshine duration in the standard day(e.g., from 2 h to 4 h) may not result in increasing annual solar fraction markedly. In terms of the monthly performance, solar fraction in January and December decreases significantly, while from May to August it just declines slightly, except for Guangzhou having a swift reduction. This study can provide insights into the behavior and promote the appropriate application of SWH in urban areas.

A CMOS Compatible MEMS Pirani Vacuum Gauge with Monocrystal Silicon Heaters and Heat Sinks

We present a micro-Pirani vacuum gauge using the low-resistivity monocrystal silicon as the heaters and heat sinks fabricated by the post complementary metal oxide semiconductor （CMOS） microelectromechanical system （MEMS） process. The metal interconnection of the device is fabricated by a 0.5 μm standard CMOS process on 8-inch silicon wafer. Then, a SiO2-Si low-temperature fusion bonding is developed to bond the CMOS wafer and the MEMS wafer, with the electrical connection realized by the tungsten through silicon via process. Wafer- level A1Ge euteetic bonding is adopted to package the Pirani gauge in a non-hermetic cavity to protect the gauge from being damaged or contaminated in the dicing and assembling process, and to make it suitable for actual applications. To increase the accuracy of the test and restrain negative influence of temperature drift, the Wheatstone bridge structure is introduced. The test results show that before capping, the gauge has an average sensitivity of 1.04 × 104 K.W-1Torr-1 in dynamic range of 0.01 20 Torr. After capping, the sensitivity of the gauge does not decrease but increases to 1.12 × 104 K.W-1 Torr-1.

On the Thermo Economical Optimization of Feed Water Heaters in Thermal Power Plants

A thermoeconomic optimization analysis is presented yielding simple algebraic formulae for estimating the optimum number of feed water heater and optimal area distribution among the feed water heaters for thermal power plants. The P1-P2 method is used in the present study, together with the thermoeconomic analyses of feed water heaters.

A MATHEMATICAL MODEL FOR POWER PLANT HEATERS

This paper studies the modelling and simulation for all forms of hcaters.The assumption of former days that the temperature of condensation is the saturationtemperature corresponding to heater pressure in steam side is no longer used.On the basisof the laws of conservation of mass,energy and momentum,the mathematical model ofheaters is established and the simulation calculation of a 125MW unit is made.The rcsultshows that the model is applicable for various kinds of steam-water heater in power plant.

An analytic model for transient heat conduction in bi-layered structures with flexible serpentine heaters

Uniform heating of complex surfaces,especially non-developable surfaces,is a crucial problem that traditional rigid heaters cannot solve.Inspired by flexible electronic devices,a novel design for the stretchable heating film is proposed with the flexible serpentine wire embedded in the soft polymer film,which can be attached to non-developable surfaces conformally.It provides a new way for the stretchable heaters to realize uniform heating of complex surfaces.However,the thermal field of flexible serpentine heaters(FSHs)depends on the configurations of the embedded serpentine heating wire,which requires accurate theoretical prediction of real-time temperature distribution.Therefore,the analytical model for the transient heat conduction in FSHs is solved by the separation of variables method and validated by the finite element analysis(FEA)in this paper.Based on this model,the effects of the geometric parameters,such as the radius and the length of the serpentine heaters,on the thermal uniformity are systematically investigated.This study can help to design and fabricate flexible heaters with uniform heating in the future.

Animal-Fats Biodiesel as a Heating Fuel for Agricultural Hot Air Heaters

Biodiesel （BD） was made from animal-fats reacting with methanol and potassium hydroxide in the laboratory. The biodiesel made in the laboratory was sent to K-petro, the government agency to inspect the quality of animal-fats biodiesel, of which generally the quality was acceptable for heating oil for agricultural hot air heater. Kinematic viscosity and calorific values of the biodiesels were measured. BD20（K）, kerosene based biodiesel, showed 18 cSt at -20 ~C. It seems that BD100 can not be suitable for heating fuel under some temperature. As BD content increased calorific value decreased up to 40,000 J/g for 100% BD （BD100） while, light oil calorific value was 45,567 J/g, showing difference of 5,567 J/g （about 12% difference）, Several different fuels including BD20 （biodiesel 20% ＋ light oil 80%）, BD50 （biodiesel 50% ＋ light oil 50%）, BD100 （biodiesel 100%） and light oil were prepared and tested for fuel combustion qualities for agricultural hot air heater and their combustion performances were compared and analyzed. Flame dimensions of biodiesels and light oil were almost same shape at the same combustion condition in the burner of the hot air heater. Generally, CO2 amounts of BDs were greater than light oil, but the differences were so small that it is hard to tell there was significant difference between the BDs combustion and light oil.

Low molybdenum ultra-pure ferritic stainless steel for solar water heaters

In order to meet the demands of service life and the synthetical performance/price ratio of stainless steel in the solar water heater industry, the low molybdenum ultra-pure ferritic stainless steel （FSS） B445J1M was developed at Baosteel. In this study, comparative studies were carried out on the mechanical properties, the formability and the corrosion resistance of B445J1M ,304 and 444 ,and the advantages and application fields of B445J1M were summarized.

Full-Scale Measurement and Numerical Analysis of Liquefied Petroleum Gas Water Heaters with Ventilation Factors in Balcony

This study carried out full-scale gas water heater combustion experiments and adopted FDS （fire dynamics simulator） to simulate three scenarios--different balcony environments when using water heater, such as airtight balcony, indoor door with openings and force ventilation to compare with full-scale combustion experiments. According to FDS simulation results, 02, CO and CO2 simulation concentration value correspond with full-scale experimental results. When the indoor O2 concentration was lower than 15%, which causes incomplete combustion, the CO concentration would rise rapidly and even reached above 1,500 ppm, causing death in short time. In addition, when the force ventilation model supplied the water heater with enough air to bum, the indoor CO concentration will keep low and harmless to humans. The study also adopted diverse variables, such as the opening area of window, outdoor wind speed and water heater types, to analyze deeply user＇s safety regarding gas water heater. In a result, while balcony area is larger than 14 mE, the volume of water heater is below 16 L （33.1 kW）, and the indoor window, connecting balcony with room, is closed, if the opening on the outdoor window of the balcony is larger than 0.2 mE, this can ensure the personal security of the indoor space.

Energetic Analysis of Two Thermal Power Plants with Six and Seven Heaters

An energetic analysis of two power plants with six and seven heaters was realized in this work and also a feedwater heater was taking into consideration. This analysis considered the temperature and pressure ranges under which power generating plants work. The unit thermal consumption (UTC), the specific fuel consumption (SFC) and the specific steam consumption (SSC) were obtained for power generation. The energetic analysis to the cycles of steam with regeneration with six and seven heaters was realized. There was a difference of 0.5% in the values of UTC, SFC and SSC when the pressures of condensation changed. Also an analysis of the behavior of the thermal efficiency in relation to the rise of numbers of heater from two to seven is presented.

Performance of U-tube Solar Water Heaters Facing Different Directions

System performance of solar water heaters depends upon collector and storage tank designs, solar radiation intensity and ambient temperature, amongst others. Evacuated glass tube collectors with U-tubes inside are less prone to leakages than the all-glass or the heat pipe types. U-tube solar water heaters suspended on walls and balconies could help overcome present day roof space restriction and increasing apartment-style housing. As such, their performance would depend upon its orientation when mounted in a vertical position. This paper reports the results of outdoor tests conducted on natural convection U-tube solar water heaters oriented towards different directions. Long and short term test procedures were employed to allow us to compare their performances as if they were tested simultaneously side-by-side.

NIR-II Organic Photothermal Cocrystals with Strong Charge Transfer Interaction for Flexible Wearable Heaters

The organic cocrystal strategy has provided a convenient and efficient platform for preparing organic photothermal materials.However,the rapidly directional preparation of cocrystals with desirable photothermal properties remains challenging due to a lack of suitable design ideas.Here,two new photothermal cocrystals,MTC and MFC,based on acceptor molecules(TCNQ and F4TCNQ)with different electron-withdrawing capacities were quickly prepared by the coprecipitation method,aiming to explore the effect of charge transfer(CT)interaction on photothermal properties.Compared with MTC,the stronger intermolecular CT interaction in MFC facilitates extending the absorption range(from the NIR-I to the NIR-II region)and enhancing the non-radiative transition process.Under the 808 nm laser irradiation,the photothermal conversion efficiency(PCE)of MFC is 54.6%,whereas MTC displays a mere 36.8%.The MFC cocrystal was further combined with a flexible polymer substrate(HPDMS)to prepare a flexible wearable heater(HPDMS@MFC),which exhibits excellent NIR-II photothermal performance.This work points out a research direction for the rapid assembly of efficient photothermal cocrystals and additionally provides an extensive application prospect for organic photothermal cocrystals in the field of wearable devices.

Optimization Method for Electrical Water Heaters Considering Shifting Potentials of Electricity Consumption and Water-use Activities

Electrical water heaters(EWHs)are important can-didates to provide demand-response services.The traditional optimization method for EWHs focuses on the optimization of the electricity consumption,without considering the shifting potential of the wateruse activities.This paper proposes an optimization method for EWHs considering the shifting potentials of both the electricity consumption and wateruse activities.Con-sidering that the wateruse activities could be monolithically shifted,the shifting model of the water-use activities was developed.In addition to the thermodynamic model of the EWH,the optimal scheduling model of the EWH was developed and solved using mixed-integer linear programming.Case studies were performed on a single EWH and aggregate EWHs,demon-strating that the proposed method can shift the water-use activities and therefore increase the load-shifting potential of the EWHs.

A comprehensive review of rectangular duct solar air heaters featuring artificial roughness

Solar air heaters(SAHs)are widely used solar thermal systems with applications in diverse sectors.However,its effectiveness is re-strained by low convective heat transfer(HT)coefficients at the absorber plate,leading to inefficient HT,and the elevated temperature of the absorber plate causes significant heat losses,reducing thermal efficiency.This study addresses these challenges by introducing ribs or roughness on the absorber plate creating turbulence in the airflow,resulting in significant improvements.The research inves-tigates various rib configurations,the influence of rib parameters,performance methods,and arrangements to evaluate their HT and friction characteristics.Among these rib configurations,a comparative analysis is done on various factors such as the Nusselt number ratio,thermal enhancement factor,friction factor ratio,and thermal efficiency to optimize distinct roughness parameters and rib ar-rangement patterns.This study also provides valuable recommendations from existing literature,offering insights into the effective design,prospects,and implementation of SAH systems.

Enhancing the efficiency of cabin heaters in emergency shelters after earthquakes through an optimized fuzzy controller

In just one and half minutes,more than fifty thousand died due to the 7.7 and 7.6 magnitude earthquakes that struck Turkey’s southeast on February 6,2023;thousands of families who barely escaped struggled to survive in the freezing weather.A warm shelter was the most basic requirement of these families.Container buildings are a rapid and easy solution to this issue.However,there is a need for a more effective and safe heating option than a wood fire for these buildings.In this study,cabin heaters,which allow truck drivers to warm up when they park their vehicles to sleep,are specially optimized for emergency shelters after an earthquake.An optimized fuzzy controller was developed to use in such buildings,which allows an air–fuel ratio in the combustion chamber of the cabin heater to be controlled adaptively based on system dynamics to get lower carbon emissions and fuel consumption.The TRNSYS software was used to establish the transient simulation model of a cabin heater with a capacity of 4 kW for a typical 21 m^(2) shelter building in Turkey’s cold regions.The developed fuzzy controller carried out the heating process of this shelter from the 15th of November to the 15th of March.Instead of using expert knowledge,the Gray Wolf Optimization(GWO)method was applied to optimize the fuzzy controller parameters developed for the cabin heater.With the optimized fuzzy controller,the fuel consumption at the end of the heating season was reduced by an average of 0.2 L/h,and the cabin heater’s efficiency increased by more than 13%.Our simulation results show that the intelligent controller we developed could improve diesel fuel combustion efficiency by up to 85%.

Wideband tunable REC-DFB laser array using thin-film heaters on the submount

A wideband wavelength-tunable 4×5 distributed feedback(DFB)semiconductor laser array based on the reconstructionequivalent-chirp(REC)technique using a simple tuning scheme is demonstrated.It consists of 20 DFB lasers with 4×5matrix interleaving distributions,two-level cascaded Y-branch optical combiners,and one active semiconductor opticalamplifier(SOA),all in-series integrated on one chip.Unlike the traditional thermal-electric cooler(TEC)-based wavelength-tuning scheme,the tunable 4×5 REC-DFB laser array achieves a faster and broader continuous wavelength-tuningrange using TaN thin-film heaters integrated on the AlN submount.By changing the injection current of the TaN resistorfrom 0 to 190 mA,the proposed tunable laser achieves a wavelength-tuning range of∼2.5 nm per channel and a total tuningof over 50 nm.This study opens up new avenues for realizing cost-effective and wide-tuning-range semiconductor lasers.

Flexible, Transparent and Conductive Metal Mesh Films with Ultra‑High FoM for Stretchable Heating and Electromagnetic Interference Shielding

Despite the growing demand for transparent conductive films in smart and wearable electronics for electromagnetic interference(EMI)shielding,achieving a flexible EMI shielding film,while maintaining a high transmittance remains a significant challenge.Herein,a flexible,transparent,and conductive copper(Cu)metal mesh film for EMI shielding is fabricated by self-forming crackle template method and electroplating technique.The Cu mesh film shows an ultra-low sheet resistance(0.18Ω□^(-1)),high transmittance(85.8%@550 nm),and ultra-high figure of merit(>13,000).It also has satisfactory stretchability and mechanical stability,with a resistance increases of only 1.3%after 1,000 bending cycles.As a stretchable heater(ε>30%),the saturation temperature of the film can reach over 110°C within 60 s at 1.00 V applied voltage.Moreover,the metal mesh film exhibits outstanding average EMI shielding effectiveness of 40.4 dB in the X-band at the thickness of 2.5μm.As a demonstration,it is used as a transparent window for shielding the wireless communication electromagnetic waves.Therefore,the flexible and transparent conductive Cu mesh film proposed in this work provides a promising candidate for the next-generation EMI shielding applications.

Accommodation of curtailed wind power by electric water heaters based on a new hybrid prediction approach

Wind power curtailment is of great importance with the increase of large-scale wind power connected to the grid. A new concept of redundant wind power accommodated by dispatching electric water heaters(EWHs) is developed in the paper. Precise predictions of wind power and EWHs load power are the basis for this work. A hybrid multi-kernel prediction approach integrating an adaptive fruit fly optimization algorithm(AFOA)and multi-kernel relevance vector machine(MKRVM) is proposed to deal with the sample distribution of multisource heterogeneous features uncovered by an energy entropy method, where AFOA is used to determine the kernel parameters in MKRVM adaptively and avoid the arbitrariness. For the large computation of the prediction approach, parallel computation based on the Hadoop cluster is used to accelerate the calculation. Then, an economic dispatching model for accommodating wind power is built taking into account the penalty of curtailed wind power and the operation cost of EWHs. The proposedscheme is implemented in an intelligent residential district.The results show that the optimization performance of the hybrid prediction approach is superior to those of four usual optimization algorithms in this case. Regular or orderly scheduling of EWHs enables accommodation of superfluous wind power and reduces dispatch cost.

Alternating current heating techniques for lithium-ion batteries in electric vehicles:Recent advances and perspectives

The significant decrease in battery performance at low temperatures is one of the critical challenges that electric vehicles(EVs)face,thereby affecting the penetration rate in cold regions.Alternating current(AC)heating has attracted widespread attention due to its low energy consumption and uniform heating advantages.This paper introduces the recent advances in AC heating from the perspective of practical EV applications.First,the performance degradation of EVs in low-temperature environments is introduced briefly.The concept of AC heating and its research methods are provided.Then,the effects of various AC heating methods on battery heating performance are reviewed.Based on existing studies,the main factors that affect AC heating performance are analyzed.Moreover,various heating circuits based on EVs are categorized,and their cost,size,complexity,efficiency,reliability,and heating rate are elaborated and compared.The evolution of AC heaters is presented,and the heaters used in brand vehicles are sorted out.Finally,the perspectives and challenges of AC heating are discussed.This paper can guide the selection of heater implementation methods and the optimization of heating effects for future EV applications.

Design and Development of a Parabolic Trough Solar Air Heater for a Greenhouse Dryer

Design and Development of a Parabolic Trough Solar Air Heater (PTSAH) for a Greenhouse Dryer (GD) was done to improve the dryer’s performance. The materials used for the fabrication of the PTSAH included galvanized sheets covered with aluminium foil, an absorber tube made of GI pipe painted matt black to increase heat absorbance at the focal line, mild steel square tubes, shutter plywood, and an axial fan to push air through the absorber tube. Key geometrical parameters used for the design of the PTSAH were a rim angle of 98 degrees, focal length of 0.2608 m, height of 0.3451 m, length of 2 m, and an aperture width of 1.2 m. The PTSAH’s total aperture surface area was 2.4 m2, while its absorber tube surface area was 0.1587 m2. The PTSAH was experimentally tested to establish its thermal performance. It was found that the ambient air recorded an average value of 31.1˚C and that the air heater could increase the air temperature by 45.6˚C above ambient with a thermal efficiency of 5.3%. It can, therefore, be concluded that the PTSAH can significantly improve the performance of a GD by supplying the GD with air at a higher temperature than ambient.