Conventional Heating Research Articles

Radio frequency-only thermal processing of skimmed milk powder: Case study on the influence of RF heating profile on quality and Salmonella Typhimurium inactivation.

Radio frequency (RF) is a dielectric heating technology that allows rapid and volumetric heating of milk powder, outperforming the heating uniformity of conventional powder heating methods. Typically, RF milk powder processing consists of a fast RF heating phase, followed by an oven heating phase in temperatures around 90 °C. This methodology can result in milk powder quality deterioration due to non-uniform temperature distributions and local overheating. Radio frequency-only processes with a more gradual heating rate are alternative solutions to minimise the impact on milk powder quality. This study investigated the effect of the heating rate on the microbial inactivation of Salmonella Typhimurium inoculated in skimmed milk powder, as well as the effect of each process on two quality characteristics, colour and solubility. Overall, a slower heating profile resulted in sufficient inactivation rates of Salmonella in skimmed milk powder, while still providing a high-quality end product. A 4-log reduction was achieved by treating the skimmed milk powder up to 95 °C using a slower, longer heating rate. No statistically significant changes were observed in the solubility of skimmed milk powder and only the harshest treatment to 95 °C led to a slight increase in the yellowness of the skimmed milk powder colour.

Effect of aging on dimensional accuracy and color stability of CAD-CAM milled and 3D-printed denture base resins: a comparative in-vitro study

BackgroundThere is a lack of studies comparing the dimensional accuracy and color stability of denture base resins made using computer-aided design and computer-aided manufacturing (CAD-CAM) milling, 3-dimensional (3D) printing, and conventional denture processing techniques. This makes it challenging to determine the best method to fabricate complete dentures. The objective of this in vitro investigation was to assess and contrast the color stability and dimensional accuracy of denture base resins that were 3D printed and CAD-CAM milled, both before and after aging by thermocycling using digital surface matching technology and a benchtop laser scanner without using a spray, to optimize adaptation of the denture base and cast to minimize any imperfections and to evaluate the impact of the denture cleansing solution on the stability of color.MethodsEvaluation of the dimensional accuracy (n = 27) was completed on a sectional maxillary stone cast using a digital 3D-surface matching software before and after 5000 thermocycles. A spectrophotometer was used to measure the color change (△E00) of all disc specimens (N = 54) before and after 500 thermocycles and immersion in denture cleansing solution for 30 cycles (3 min each) daily for 6 days. The Kruskal Wallis test, Dunn’s post hoc test, Tukey’s test with Bonferroni adjustment, one sample t test and independent t test were used to statistically analyze the data (α < 0.05).ResultsThermocycling decreased the dimensional accuracy of the heat polymerized group at all 5 locations and the 3D-printed group at locations 1, 3 and 5 (P > .05), while it had no significant difference on the CAD-CAM milled group at all locations (P < .05). The color change (△E00) was lowest in the CAD-CAM milled group, moderate in the heat-polymerized group and highest in the 3D-printed group. After immersion in denture cleanser, the color change (△E00) was significantly higher in the 3 groups compared with after thermocycling (P > .001).ConclusionsCAD-CAM milled resins had the highest dimensional accuracy and the best color stability, conventional heat polymerized acrylic resins showed moderate change in dimensional accuracy and color stability, while the 3D- printed resin had the lowest dimensional accuracy and color stability after aging by thermocycling.

Hydrothermal coupling model between wellbore and permafrost for drilling in arctic cold regions

The abundant oil and natural gas resources in the Arctic cold regions have driven people to conduct drilling operations in these harsh environments. During drilling operations in Arctic permafrost regions, the linear heat source effect generated by the flow of drilling fluid in the wellbore continuously melts the surrounding permafrost, which can lead to wellhead settlement and instability of the wellbore wall, among other accidents. In order to provide guidance for drilling engineering in cold regions, there is an urgent need to study the coupled heat transfer between the wellbore and the permafrost in Arctic drilling. Due to the significant influence of hydrothermal coupling process in permafrost on temperature transfer, conventional wellbore heat transfer models are not suitable. Therefore, this paper proposes a hydrothermal coupling model between the wellbore and permafrost for drilling in Arctic cold regions and analyzes the heat transfer in the wellbore and the hydrothermal processes of the formation using numerical methods. By applying this model, the insulation effects of existing main wellbore temperature control and insulation technologies were studied. The main research findings indicate that drilling process can cause the permafrost around the wellbore to thaw, and the thawed permafrost around the wellbore presents a “horn” shape that expands from the wellhead to the bottom of permafrost layer; Without insulation measures, the volume of thawed permafrost around the wellbore can reach 315 m³ after 7 days of circulation; During the drilling process, moisture migration occurs. Under the effect of gravitational seepage, unfrozen water content in the thawed permafrsot around the wellbore increases from the wellhead to the bottom of the permafrsot layer; Vacuum insulated tubing has almost negligible impact on the temperature of the drilling fluid in the wellbore, while it can reduce the volume of thawed permafrost around the wellbore by 62.5 % to 88 % or even higher; Drilling fluid cooling systems can significantly lower the temperature of the drilling fluid in the wellbore but cannot effectively prevent the thawing of permafrost around the wellbore. Therefore, in practical drilling operations, priority should be given to using high-quality vacuum insulated tubing or combining both methods simultaneously.

Experimental study on steady-state performance of an axial grooved heat pipe under rotational condition

This study explores the performance optimization of grooved heat pipes under rotational conditions, focusing on both straight and curved designs. To address the challenges posed by centrifugal forces in rotating systems, we designed and tested a conventional straight grooved heat pipe and a novel curved grooved heat pipe with a variable curvature structure. Experiments were conducted across a range of rotational speeds (0–20 rpm), heat loads (30 W-300 W) and loading methods (heat load before rotation and heat load after rotation) to evaluate the operating performance of both grooved heat pipes. The results indicate that the straight grooved heat pipe struggled to maintain efficiency under rotational conditions, as centrifugal forces caused fluid to accumulate at both ends, leading to higher operating temperatures and reduced heat transfer efficiency. At the case of 20 rpm with a heat load of 110 W, the temperature difference exceeded 25 °C, highlighting the limitations of the straight design in such environments. In contrast, the curved grooved heat pipe effectively mitigated the impact of centrifugal forces. Its design reduced liquid accumulation in the condenser section, maintained beneficial acceleration effects in the evaporator section, and improved overall heat transfer performance. Specifically, at 20 rpm, the curved pipe successfully transferred over 300 W with a temperature difference not exceeding 5 °C, demonstrating its superior performance. However, at higher rotational speeds and lower power levels, the curved design also showed some limitations, as excessive fluid accumulation in the evaporator section led to a shift in the evaporation site, increased thermal resistance, and a certain degree of superheating. These findings highlight the potential of the variable curvature design in improving the efficiency of grooved heat pipes under rotational conditions. This work advances the understanding of fluid dynamics and heat transfer mechanisms in such systems, offering insights that could inform the design of more efficient heat pipes for rotating applications.

Enhanced post-combustion CO2 capture and direct air capture by plasma surface functionalization of graphene adsorbent

Graphene has enormous potential to capture CO2 due to its unique properties and cost-effectiveness. However, graphene-based adsorbents have drawbacks of lower CO2 adsorption capacity and poor selectivity. This work demonstrates a one-step rapid and sustainable N2/H2 plasma treatment process to prepare graphene-based sorbent material with enhanced CO2 adsorption performance. Plasma treatment directly enriches amine species, increases surface area, and improves textural properties. The CO2 adsorption capacity increases from 1.6 to 3.3 mmol/g for capturing flue gas, and from 0.14 to 1.3 mmol/g for direct air capture (DAC). Importantly, the electrothermal property of the plasma-modified aerogels has been significantly improved, resulting in faster heating rates and significantly reducing energy consumption compared to conventional external heating for regeneration of sorbents. Modified aerogels display improved selectivity of 42 and 87 after plasma modification for 5 and 10 min, respectively. The plasma-treated aerogels display minimal loss between 17% and 19% in capacity after 40 adsorption/desorption cycles, rendering excellent stability. The N2/H2 plasma treatment of adsorbent materials would lower energy expenses and prevent negative effects on the global economy caused by climate change.

Electrochemistry of Phase-Change Materials in Thermal Energy Storage Systems: A Critical Review of Green Transitions in Built Environments

This article reviews recent research on phase-change materials (PCMs) used in thermal energy storage systems with the aim of enhancing their performance. The study explores various methods to improve heat transfer in PCMs, such as microencapsulation, infill materials, fins and nanofluids. Additionally, it evaluates techniques to boost heat transfer in latent heat thermal energy storage (LHTES) systems and investigates ways to increase thermal conductivity using porous and low-density materials. PCMs store thermal energy, making them suitable for use in solar energy systems when solar energy is not available. The need for eco-friendly alternatives to conventional heating and cooling in global construction and the significant energy consumption of buildings has driven research on this topic. As such, this study additionally examines current advancements in free cooling systems with latent heat storage to identify the key factors affecting their effectiveness. The findings show that using PCMs for overnight cooling maintains the room temperature within the comfort zone and reduces the cooling loads in various climates. Using machine learning methods, this study also compares recent advancements in the use of PCMs in various solar energy systems, including solar thermal power plants, solar air purifiers, solar water heaters and solar appliances. Results derived feature key factors crucial for the optimal selection of PCMs and the challenges associated with sustainable green transitions in built environments. HIGHLIGHTS This review provides an in-depth examination of PCM thermal energy storage systems. This study investigates the use of fillers, nanofluids, and nanoparticles for enhanced heat transfer. Analytical methods for boosting the PCM thermal conductivity are briefly outlined. Geometric design and thermal conductivity enhancement affect the Latent Heat Thermal Energy Storage (LHTES). The assessment also evaluates advanced free-cooling systems using the LHTES. PCMs help to store heat energy in solar systems and bridge supply gaps. GRAPHICAL ABSTRACT

Parametric Analysis of the Compact and Long-Term-Operable Passive Residual Heat Removal System

Differing from land-based systems, conventional passive residual heat removal systems (PRHRSs) in nuclear-powered ships encounter challenges for use as safety systems due to limited space and difficulties in adopting safety aids. To resolve this problem, the authors have previously suggested a compact and long-term-operable PRHRS that uses air cooling and seawater cooling in tandem, and its feasibility was confirmed through a design study and transient analysis. Nevertheless, the system performance depends on various parameters, and their sensitivities have yet to be analyzed. The purpose of the current study is to conduct a parametric analysis of the system focusing on four parameters: filling ratio, thermal center difference between heat source and sink, heeling angle, and heat source temperature. The Multi-dimensional Analysis of Reactor Safety (MARS-KS) code was used for the parametric analysis. The results show that the parameters are highly interrelated with each other, and consequently, the system exhibits significantly different behavior depending on the parameter conditions. In particular, the filling ratio determines the overall trends of the system. It was also found that the presence of two heat sinks with a single heat source in the natural circulation loop of the system complicate the natural circulation behavior. Based on the results, we conclude that a thorough examination and careful control of the parameters are necessary to implement the proposed system. The highlights are as follows: 1. Parametric analysis of compact and long-term-operable PRHRS is conducted. 2. Analysis reveals that the filling ratio is the most dominant parameter for system performance. 3. The unique behavior of the natural circulation loop with two heat sinks and a single heat source is analyzed.

Bioactivity and application potential of O/W emulsions derived from carboxylic acid-based NADES-extracted total saponins from Polygonatum cyrtonema Hua

This study focuses on evaluating new methods for the green extraction of saponin compounds from Polygonatum cyrtonema Hua (PCH). This study utilized a combination of carboxylic acid-based natural deep eutectic solvents (NADES) and various extraction techniques including conventional heat reflux-, ultrasound-, and microwave-assisted extraction. The primary objectives were to assess total saponin yield, antioxidant capacity, and enzyme inhibition efficiency. Additionally, the solvents and extracts were evaluated for their antibacterial activity. Oil-in-water (O/W) emulsions of NADES extracts were also characterized and analyzed for stability. Results indicated that three NADES systems were effective in extracting saponins, with choline chloride and lactic acid (ChCl-LA) system being the most efficient. The ChCl:LA extract exhibited antimicrobial and antioxidant activities superior to conventional organic solvent extracts. Additionally, it demonstrated maximum inhibitory activity (IC50 values: 0.98 ± 0.03 and 1.46 ± 0.07 mg/mL, respectively) against α-glucosidase and α-amylase. The NADES extract as an aqueous phase significantly improved the stationarity of the O/W emulsion. Collectively, the study highlights the antimicrobial and technological advantages of NADES as a potential solvent for extracting saponin compounds from PCH.

APPLICATION OF OHMIC HEATING IN THE FOOD INDUSTRY, IMPACT ON FOOD COMPONENTS AND "HURDLE APPROACH"

The application of thermal processes in the food industry causes a decrease in the quality of the final product, such as nutritional value and organoleptic characteristics. Many alternative methods offer uniform and rapid heating and provide the desired microbial lethality without reducing overall product quality. Ohmic heating is an emerging technique for food processing that has been used in recent decades as an alternative to conventional heating. It is a rapid heating method with big potential in the food industry. More particularly, ohmic heating of food is used for microbial inactivation, blanching, fermentation, gelatinization, peeling, evaporation, drying, extraction, pasteurization, and sterilization. This review summarizes the application of ohmic heating to different types of food products, the impact on food components, as well as the synergistic effect of ohmic heating with other non-thermal preservation techniques as well as the case of its combination with packed food items. The optimization of the ohmic heating approach reduces the duration of the process, achieves microbial and enzyme stability, increases the yield, and preserves the organoleptic and bioactive components in food commodities. Applying ohmic heating in combination with other non-thermal food preservation techniques such as UV-C radiation, pulsed electric field, high pressure, ultrasound, vacuum and the addition of preservatives contributes to reducing the intensity of the applied electric field, the temperature, and the treatment. In addition, it contributes to the extension of the shelf life as well as preserving the nutritional and organoleptic quality of food.

Microwave‐Assisted Synthesis of Spiro Heterocyclic Scaffolds Using Graphite Oxide as a Heterogeneous Carbocatalyst and Study of their Anti‐Microbial Activities

AbstractEven though an astonishing variety of spirooxindole derivatives has been synthesized until now, the look for rapid, highly efficacious, environmental‐friendly and more skilful methods is yet an ongoing challenge. Here, we present a microwave‐assisted synthetic approach for the one‐pot synthesis of spirooxindole‐pyrimidine and spiro‐chromeno indoline‐trione derivatives in water using graphite oxide (GO) as a charismatic heterogeneous metal‐free carbocatalyst.Microwave‐assisted synthesis reduces the reaction times from hours (conventional heating) to minutes. The use of a heterogeneous catalyst allows for efficient recovery and reusability up to eight cycles without losing much of its effectiveness, thereby enhancing sustainability. This method offers high product yields of diverse substrates with low catalyst loading and simple work‐up and catalyst handling. In addition, the antimicrobial activities for some randomly taken compounds have also been studied against gram positive bacteria Staphylococcos aureus (MTCC96) and gram negative bacteria Escherichia coli(MTCC730).

A kinetic comparison between in situ hybrid microwave and conventional magnetising roasting of low-grade iron ore composite pellet

This article aims to comprehensively summarise the essential aspects of reduction kinetics in magnetising roasting of low-grade iron ore–coal composite pellets in the hybrid microwave and conventional furnace. The influence of crucial process parameters like temperature, time, and heating methods, including traditional and hybrid microwave heating, is explored. Investigating the impact of low-grade iron ore and coal quality on reduction kinetics is conducted to identify optimal heating methods for upgrading low-grade iron ore to blast furnace grade through magnetising roasting. The study uses diverse gas–solid reaction models to assess the reduction mechanism (Fe2O3 to Fe3O4). Results indicate the success of the contracting volume model for microwave heating, while conventional heating transitions from phase-boundary chemical control to diffusion control. XRD confirms magnetite dominance post-reduction, while scanning electron microscopy analysis establishes microwave crack-assisted efficiency over conventional heating for ease of reduction. A comparative study of apparent activation energy reveals the hybrid microwave method's four-fold lower (36.71 kJ/mol) than conventional resistance heating (156.19 kJ/mol). This underscores the potential of microwave heating for enhanced reduction kinetics and low-grade iron ore material processing applications.

Activation of NO with microwave irradiation for low temperature direct decomposition

Direct decomposition of nitric oxide (NO) on metal oxides under microwave (MW) irradiation was investigated and it was found that the most metal oxides show higher NO decomposition activity than that in the conventional electric furnace heating at low temperature. Among the examined oxides, it was found that TiO2, CeO2, ZrO2, and Y2O3 show about 95 % or higher NO conversion at 573 K, and both N2 and O2 are formed with almost equimolar amount. In particular, ZrO2 exhibited high and stable NO decomposition activity more than 25 h. In this study, the influence of coexisting gases on NO decomposition activity on ZrO2 under microwave heating was further investigated and the direct decomposition of NO can be proceeded even in the presence of 5 % O2, 5 % CO2, or humidified condition. Mechanism of high NO decomposition activity under MW irradiation was also studied and it was found that removal of oxygen from the catalyst was much increased under MW irradiation because of direct activation of oxygen and also direct activation of NO which is also suggested by pulse reaction.

Achieving superior mechanical and corrosion properties in medium-thickness Ti-6Al-4 V alloy joints by back heating assisted friction stir welding below β-phase transformation temperature

The equiaxed microstructure formed below the β-phase transition point of Ti alloys generally exhibits an excellent balance of mechanical properties and corrosion resistance. However, this desirable microstructure is impossible to be obtained in fusion welded joints but is prospective to be achieved by the solid-state friction stir welding (FSW) technique. Unfortunately, it generally generates bottom defects and severe tool wear in medium-thickness Ti alloy joints when conventional FSW was conducted below the β-phase transition point. In this study, 6 mm thick Ti-6Al-4 V plates were joined by both the conventional FSW and back heating assisted FSW (BHAFSW). Defects caused by significant tool wear and bottom phase transition differences occurred in the conventional FSW. It was found that the hardness difference between the base material (BM) and the tool increased to 35.6 % from 500 °C to 900 °C. The back heating (150 °C) was used to control welding temperatures remaining the 900 °C, thus largely reducing the tool wear by increasing the hardness difference. In addition, the back temperature compensation increased the bottom temperature and controlled the phase transition position from the bottom to the middle of the joint. The shoulder pressure contributed to the compression of the defects, and the defects were eliminated by increasing the pressure at the phase transition position. A significantly refined equiaxed microstructure with an average grain size of ∼0.9 μm was achieved below the β-phase transition temperature in the stir zone via back heating assisted FSW, while a bimodal structure with an average grain size of 3.5 μm was formed near the β-phase transition temperature. Inconspicuous reduction of the strength was detected for the joints (98 % of the BM) which possess equiaxed microstructures, and the corrosion resistance of the joints was enhanced compared to the BM. This superior synergy of mechanical and corrosion properties exceeded the majority of Ti alloy joints previously reported. This study provided an effective method for obtaining medium-thickness Ti alloy joints with ultrafine equiaxial structures with superior mechanical properties and corrosion resistance.

Energetic and economic analysis of a novel concentrating solar air heater using linear Fresnel collector for industrial process heat

Industrial processes share a relevant portion of global energy consumption. A large variety of high energy-demanding industrial processes need hot air in the medium temperature range, provided by natural gas combustion or by electricity. Hot air is used as a medium in a large variety of processes such as drying, curing, and thermal treatments of several products and materials. Heat can be provided by solar thermal technologies aimed at the sustainable industry. Non-concentrating flat plate type solar collectors can directly heat air up to 100 °C while higher temperatures can be achieved using linear concentrating technology. In this study an innovative system using linear Fresnel collectors directly provides hot air for the industry up to 350 °C, avoiding the need for liquid heat transfer fluids. Accordingly, the installation is simplified, and lower installation and maintenance requirements are expected compared to other solar technologies. The present studies provide an energetic and economic analysis of the concentrating solar air heater, considering a medium-scale benchmark as a reference case in representative European locations. The results indicate that the solar technology here presented can be economically competitive with conventional natural gas heating, having a huge potential for fossil fuel source replacement in hot air based industrial processes.

Multiscale study of dynamic mode-I fracture characteristics of thermally treated granite: Comparison of conventional and microwave heating

High-temperature-assisted rock breaking is a promising technique, with conventional and microwave heating being widely used methods. Understanding the mechanisms of conventional and microwave heating on the dynamic mode-I fracture characteristics of rock is crucial for engineering applications. Dynamic mode-I fracture experiments were conducted on Notched Semi-Circular Bending (NSCB) specimens at 25, 200, 300, 400, and 500 °C under both heating methods. Additionally, a finite element-discrete element coupled numerical method was developed to simulate the dynamic mode-I fracture process in high-temperature granite. The study investigated the effects of both heating methods on the fracture process and morphological features of the rocks, revealing differences in damage mechanisms across various scales. Results indicated that both heating methods similarly influence the fracture toughness of granite, with fracture toughness initially remaining nearly unchanged and then rapidly decreasing, with 200 °C identified as the threshold temperature. Moreover, the fractal dimension increased exponentially with temperature. The fracture mechanisms associated with conventional and microwave heating were also discussed.

Could residential air-source heat pumps exacerbate outdoor summer overheating and winter overcooling in UK 2050s climate scenarios?

The UK government promotes heat pumps to replace gas boilers in the residential sector as a vital part of its strategy to achieve Net Zero by 2050. As climate change intensifies, heat pumps, traditionally used for heating, will also play a role in cooling to address indoor heat risks that threaten public health and increase energy demands. However, air-source heat pumps (ASHPs) might unintentionally exacerbate summer overheating and winter overcooling in residential neighbourhoods. This study uses a multi-scale modelling approach, combining SUEWS and EnergyPlus, to assess the impact of ASHPs on outdoor temperature in two idealised UK low-rise residential neighbourhoods under 2050s climate scenarios. Results show that in summer, ASHPs increase median anthropogenic heat emission by up to 19.3 W m-2 and raise local median 2 m air temperature by up to 0.12 °C in an idealised London neighbourhood. In winter, replacing gas boilers with ASHPs for heating reduces anthropogenic heat emissions by up to 11.1 W m-2 and lowers local air temperatures by up to 0.16 °C in London. The research shows that conventional waste heat calculations from air-conditioning can overestimate anthropogenic heat emissions by up to 86 %, and cooling entire building rather than just occupied rooms can increase energy consumption by 68 %. Although temperature changes will vary across UK cities, the response of air temperature to anthropogenic heat change is generally consistent. The study enhances understanding of role of ASHPs in the UK's net zero target for 2050, highlighting the importance of balancing outdoor and indoor thermal comfort when considering the wide use of ASHPs.

One-Pot, Multi-Component Green Microwave-Assisted Synthesis of Bridgehead Bicyclo[4.4.0]boron Heterocycles and DNA Affinity Studies.

Anthranilic acids, salicylaldehydes and arylboronic acids reacted in EtOH/H2O (1/3) at 150 °C under microwave irradiation for 1 h to give, in excellent yields and purity, twenty-three bridgehead bicyclo[4.4.0]boron heterocycles via one-pot, three-component green synthesis. The scope and the limitations of the reactions are discussed in terms of the substitution of ten different anthranilic acids, three salicylaldehydes and three arylboronic acids. The replacement of salicylaldehyde with o-hydroxyacetophenone demanded a lipophilic solvent for the reaction to occur. Eight novel derivatives were isolated following crystallization in a toluene-containing mixture that included molecular sieves. The above one-pot, three-component reactions were completed under microwave irradiation at 180 °C within 1.5 h, thus avoiding the conventional prolonged heating reaction times and the use of a Dean-Stark apparatus. All derivatives were studied for their affinity to calf thymus DNA using proper techniques like viscosity and UV-vis spectroscopy, where DNA-binding constants were found in the range 2.83 × 104-8.41 × 106 M-1. Ethidium bromide replacement studies using fluorescence spectroscopy indicated Stern-Volmer constants between 1.49 × 104 and 5.36 × 104 M-1, whereas the corresponding quenching constants were calculated to be between 6.46 × 1011 and 2.33 × 1012 M-1 s-1. All the above initial experiments show that these compounds may have possible medical applications for DNA-related diseases.

Thermodynamic analysis of a new tandem dual-temperature air source heat pump with ejector

This paper presents a conventional air source heat pump cycle (CHPC) and two dual-temperature air source heat pump cycles (DTHPC1 and DTHPC2). DTHPC1 employs two condensers, while DTHPC2 adds an extra compressor and combines the ejectors on top of DTHPC1. Compared with the conventional heat pump cycle, the new dual-temperature heat pump DTHPC2 can provide hot water at one additional temperature and still have high performance. In this paper, the refrigerants R1234yf and R1234ze(E) were selected as suitable for the cycle conditions. The cycle performance under different conditions was simulated and compared based on energy analysis methods and exergy analysis methods. The main performance parameters included COPh, ηex, etc. The results demonstrate that the COPh and ηex of DTHPC2 and DTHPC1 are greater than those of CHPC under identical conditions. Specifically, at an ambient temperature of approximately -10 °C, high-temperature hot water of approximately 65 °C, and low-temperature hot water of approximately 35 °C, the COPh of DTHPC2 and DTHPC1 increased by 45% and 32.7%, respectively, in comparison to CHPC. Similarly, the ηex of DTHPC2 and DTHPC1 increased by 27.1% and 28.9%, respectively.

Thermal comfort driven space heating control via hierarchical state machine strategy interacting with multiphysics simulation

Improving energy efficiency of space heating systems is as important as adopting emerging clean energy technologies for decarbonising heating. While exploring strategies for reducing energy consumption, the space occupants’ expectations to thermal comfort should not be sacrificed. Conventional space heating control systems are often developed under the hypothesis of uniform temperature distribution in a bounded space and the heating system controller is primarily operated based on the information from the temperature sensor at a fixed position. That is, the measured temperature does not represent the temperature surrounding the occupant’s location. This paper explores a new control method; the heating system control is led by the occupant’s thermal experience, expressed by the temperature surrounding the occupant. A new hierarchical state machine control strategy interacting with a Multiphysics simulation model to dynamically estimate the temperature at the point of the occupant is developed. The accuracy of the Multiphysics simulation model is verified based on the corresponding experimental test room data. A co-simulation platform is built to allow COMSOL and SIMULINK to communicate in real-time for control strategy realisation. The experimental results show that the maximum and average mean square error between the measured and simulated temperature under different operating modes is less than 0.21℃ and 0.06℃, respectively. The simulation results indicate that energy consumption could be potentially reduced around 20% with an improved thermal comfort of the occupant by 30%, compared with the conventional fixed sensor control method.

Synthesis pathways of (HfZrTiCe/La/Y)O2-x nanoparticles via benzyl alcohol route at critical temperature

The controllable synthesis of high-entropy fluorite oxide (HEO) having large ionic radius mismatch remains a challenging due to poor understanding on nucleation. The (HfZrTiLn)-5HEO nanoparticles with 15 % ionic radius mismatch were synthesized via benzyl alcohol route at 220 °C-5 min in presence of PtCl4 and Fe(acac)3, exhibiting novel optical, electrical and magnetic properties. Nucleation pathways of the 5HEO at the critical temperature were elucidated by using a comparison study of conventional heating and microwave irradiation heating. Consistency of XRD patterns and STEM-EDX observation indicate that the resultant Hf-OBn monomers acted as the nucleation center of the 5HEO, determined by diffusion kinetics. The nucleation rate depended on the metal monomers assembly and esterification reaction, which was accelerated by water vapor pressure produced in-situ by 0.5×10−4mol/l PtCl4 catalyst. The Fe-metal organic cages derived from 1.5×10−4mol/l Fe(acac)3 additive served as the structure stabilizer of Zr/Ti monomers, and prevented early hydrothermal reaction route.