Low Heat Research Articles

High power cladding-pumped low quantum defect Raman fiber amplifier

Heat generated by the quantum defect (QD) in optically pumped lasers can result in detrimental effects such as mode instability, frequency noise, and even catastrophic damage. Previously, we demonstrated that boson-peak-based Raman fiber lasers have great potential in low QD laser generation. But their power scalability and heat load characteristics have yet to be investigated. Here, we demonstrate a boson-peak-based Raman fiber amplifier (RFA) with 815 W output power and a QD of 1.3%. The low heat generation characteristics of this low QD RFA are demonstrated. Both experimental and simulation results show that at this power level, the heat load of the low QD RFA is significantly lower than that of the conventional RFA with a QD of 4.8%. Thanks to its low heat generation characteristics, the proposed phosphosilicate-fiber-based low QD RFA provides an effective solution for the intractable thermal issue in optically pumped lasers, which is of significance in reducing the laser’s noise, improving the laser’s stability and safety, and solving the challenge of heat removing.

Optimization of Process Parameters of Cold Metal Transfer Arc Welding of AA 6061 Aluminium Alloy-AZ31B Magnesium Alloy Dissimilar Joints Using Response Surface Methodology

The fabrication of dissimilar metal joints, particularly between AA 6061 aluminum alloy (Al) and AZ31B magnesium alloy (Mg), poses significant technical challenges due to their distinct metallurgical characteristics and the inherent difficulties associated with welding such materials. These challenges include the propensity for intermetallic compound formation, thermal cracking, and differences in thermal and mechanical properties between the two alloys. Cold Metal Transfer (CMT) welding, known for its low heat input and controlled metal transfer, offers a potential solution to these issues. However, optimising the process parameters to ensure strong, defect-free joints requires a systematic approach. This study aims to optimize CMT welding parameters using parametric mathematical modeling (PMM) to produce high-strength Al and Mg dissimilar joints and to study the effects of CMT parameters on tensile strength (TS) and weld metal hardness (WMH), as well as the microstructural features of AA 6061 aluminum alloy/AZ31B magnesium alloy (Al/Mg) dissimilar joints. Al/Mg dissimilar butt joints were produced by the CMT process using ER4043 as filler wire. CMT, a low-heat input welding technique, was used to mitigate issues such as intermetallic compounds (IMCs), wider heat-affected zones (HAZ), and distortion. The CMT parameters, particularly wire feed speed (WFS), welding speed (WS), and arc length correction (ALC), were optimized using response surface methodology (RSM) to maximize the TS and WMH of the Al/Mg dissimilar joints. Polynomial regression was employed to create PMMs that integrated these CMT parameters to forecast the TS and WMH of the joints. An analysis of variance (ANOVA) was applied to assess the feasibility of the PMMs. The results indicated that the Al/Mg dissimilar joints, produced using a WFS of 4700 mm/min, a WS of 280 mm/min, and an ALC of 10%, exhibited higher TS and WMH values of 33 MPa and 95.8 HV, respectively. The PMMs provided precise forecasts for the TS and WMH of the Al/Mg joints with an error rate of less than 1% and a confidence level of 97%.

High-efficiency anaerobic digestion of soybean curb residue with simultaneous phosphorus recovery by Mg[sbnd]Fe layered double hydroxides addition

Anaerobic digestion of food waste faces several technical problems, such as process failure caused by over-acidification, low heating value of biogas, and high treatment cost of liquid digestate. Layered double hydroxides (LDH) are expected to simultaneously enhance biogas production and quality and immobilize soluble phosphorus in AD due to their excellent anion exchange capability. This study first verified the above hypothesis, indicated by a dramatically enhanced methane yield of 17 folds under a high substrate load and a high quality of generated biogas with 89 % methane content and 90 % lowered hydrogen sulfide. Meanwhile, the soluble phosphorus was efficiently reduced to 3 mg/L after AD. Moreover, the calcined product of LDH showed comparable performance, indicating the possibility of reusing LDH in the AD process. The above results implied the great potential of LDH as a multifunctional material for enhancing the efficiency of waste treatment and energy/resource conversion in the AD process.

Parameter optimization, microstructural and mechanical properties of fiber laser lap welds of DP1200 steel sheets

In this research, the effects of laser power, laser welding speed and laser incidence angle were evaluated in terms of weld geometry, microstructure, microhardness, fracture surfaces and tensile shear load in fiber laser welding joints of DP1200 steel sheets. Response Surface Methodology (RSM) was utilized to derive mathematical relationships between the process parameters and the tensile shear load after the tensile test. The optimum combination of process parameters was a laser power of 2800 W, a laser welding speed of 40 mm/s, and a laser incidence angle of 70°. A thermal camera was used to record the laser welding process, and the cooling rates were evaluated by analyzing this data. The influence of cooling rate upon microstructure phase formation for DP1200 steel is investigated, with continuous cooling transformation (CCT) diagrams. Also, post-welding stress and displacement were simulated by Simufact Welding software. At high heat input (55.79 J/mm) occurred coarse dendritic martensitic lath growth while at low heat input (37.6 J/mm) fine dendritic martensitic structure was observed in the weld zone was obtained owing to the high rate of cooling. The microstructure consists of full martensite at a higher than 10 °C/s cooling rate. The findings reveal that the phases in FZ and HAZ, the morphology and martensite/bainite constituents differed related to the heat input and laser incidence angle, which ultimately affects the joint’s microhardness, fracture dynamics and tensile shear load.

Effect of depositional strategy on surface roughness of Al-5%Mg wall fabricated via Cold Metal Transfer based Wire Arc Additive Manufacturing

Cold Metal Transfer (CMT) based Wire Arc Additive Manufacturing (WAAM) is the future-driven novel technology for fabricating complex metal components, having advantages like high deposition rates, increased material efficiency, lesser lead time, low heat input, and low cost. Despite of above advantages, the CMT-WAAM process possesses few limitations in terms of producing metal components with high geometrical accuracy. Al-Mg alloys are particularly appealing for their lightweight and exceptional mechanical properties, making them attractive for various industrial applications such as marine, automobile, aerospace, etc. In this study, an Al-5%Mg alloy single wall has been built through CMT-WAAM using Current at 110A, Travel Speed (TS) of 7 mm/sec, and Gas Flow Rate (GFR) of 15L /min. The effect of unidirectional and bidirectional deposition direction on the surface quality of the fabricated sample has been investigated. Surface roughness (Ra) tests were conducted at three different zones (upper, middle, and bottom) of the specimen wall before the machining operation using a taylor hobson surtronic tester. It is concluded from the results that the S2 wall (unidirectional) has more Ra value than the S1 wall (bidirectional) in all zones due to the presence of a humping defect which results in more waviness over the S2 wall’s surface. In the bidirectional strategy, the roughness value reduces by 8.567 % (upper zone), 9.95 % (middle zone), and 13.019 % (bottom zone) than the unidirectional strategy. Thereby establishing that the deposition direction tends to build WAAM wall with a better surface finish.

A surface quality optimization strategy based on a dedicated melt-pool control via the dashed-scan contouring technique in electron beam powder bed fusion

Electron beam powder bed fusion (EB-PBF) is a key metal additive manufacturing (AM) technology known for its high energy absorption and low heat stress. However, the high surface roughness of EB-PBF parts has limited its broader application. To address this issue, this paper proposes a dashed-scan contouring strategy to obtain lower surface roughness in EB-PBF. This strategy involves blending the melts the contour in the form of segmented staggered scans and employing high-frequency jumping of the electron beam (EB) to melt multiple positions synchronously. A comprehensive analysis, combining experimental investigations and multi-physical simulations, elucidates the intrinsic connection between control processes and melt pool stability. Results show that by controlling the length-to-width ratio of the melt pool, regulating overlap distances between melt pools, and fine-tuning cooling times, balling phenomena and Plateau-Rayleigh instabilities can be suppressed. Additionally, these measures effectively mitigate irregularities in track formation when compared to the traditional process. Experimental validation demonstrates the efficacy of the approach, achieving reduced surface roughness (Ra) of thin-walled Ti-6Al-4V parts from over 25 μm to below 12.6 μm, while enhancing dimensional accuracy and reducing melt anomalies at corners. The proposed dashed-scan contouring strategy opens new avenues for AM of highly reliable and intricate structures, such as lattice sandwich structures, thin walls, and internal flow passages.

Experiments on heat transfer and film cooling characteristics of double-wall cooling structure with novel slot holes and pin-fins

The influences of blowing ratio, mainstream velocity, density ratio and jet Reynolds number on the heat transfer and film cooling properties of double-wall cooling cell (DWCC) with slot holes, impingement and diamond-shaped pin-fins were studied by means of pressure sensitive paint and transient liquid crystal. The simulation obtained the flow characteristic at a jet Reynolds number of 20000. The results indicated that with the increase of blowing ratio, the film cooling performance of DWCC structure also increased, and there was no film lift-off phenomenon which occurred in the cylindrical hole. The presence of pin-fins created a spike-shaped film in the slot outlet. Therefore, when studying the DWCC structure, it was important to consider the couple effects of impingement, pin-fins, and slot hole. As the density ratio decreased and the mainstream velocity increased, the film cooling effectiveness (FCE) gradually decreased. When jet Reynolds number increased from 20,000 to 60,000 under a density ratio of 2.0, the area-averaged FCE increased from 0.308 to 0.435, with an increase of up to 41.2%. The convective heat transfer level of impingement stagnation point was much higher than that of pin-fins region. Due to the transition between the impinging jet and the wall jet, the heat transfer coefficient (HTC) had a multi-peak distribution. In addition, several low heat transfer zones similar to wing-shaped, eye-shaped, and crescent-shaped were observed on the target surface and bottom surface inside the cooling cell. The DWCC structure studied in this paper is more efficient in cooling performance compared to traditional cooling structures. This makes it suitable for use in various fields such as heat transfer of turbine blades and electrical equipment.

Upcycling of PVC waste to high-value sorbent with KOH-activation for efficient removal of organic dyes

Polyvinyl chloride (PVC), known for its chemical stability and flame-retardant qualities, has many uses in various fields, such as pipes, electric wires, and cable insulation. Research has established its potential recovery as a fluidic fuel through pyrolysis, but the use of PVC pyrolysis oil, which is tainted by chlorine, is constrained by its low heat value and harmful environmental effects. This study engineered a layered double hydroxide (LDH) to tackle these challenges. The LDH facilitated dechlorination during PVC pyrolysis and bolstered thermal stability via cross-linking. During pyrolysis with LDH, PVC was transformed into carbon-rich precursors to sorbents. Chemical activation of these residues using KOH created sorbents with a specific surface area of 1495.4 m2 g⁻1, rendering them hydrophilic. These resulting sorbents displayed impressive adsorption capabilities, removing up to 486.79 mg g⁻1 of methylene blue and exhibiting the simultaneous removal of cations and anions.

Superior ablation resistance of C/C-HfC-SiC composite sharp leading edges above 2500 °C prepared by precursor infiltration and pyrolysis

HfC-SiC-modified carbon/carbon composite (C/C-HfC-SiC) sharp leading edges (SLEs) were prepared via precursor infiltration and pyrolysis for potential hypersonic applications. The effect of SiC proportion on the ablation behavior of the SLEs under oxyacetylene flames with 2.38 MW/m2 and 4.18 MW/m2 was investigated. The preferred sample with a volume ratio of HfC to SiC of 0.74 possessed almost zero degradation (linear recession rate 0.6 μm/s) up to a temperature of 2371 °C. As the temperature increases to 2527 °C in the latter condition, the SLE with less SiC (the volume ratio of HfC to SiC is 1.10) exhibited a linear recession rate of 1.03 μm/s during cyclic ablation of 3 × 40 s. Relatively more SiC addition is favorable under lower heat flux due to the better oxygen barrier performance of the scale. However, superior ablation resistance is available under higher heat flux with less SiC addition due to the higher thermal stability of the resulting oxide scale.

An artificial intelligence study on energy, exergy, and environmental aspects of upcycling face mask waste to a hydrogen-rich syngas through a thermal conversion process

Studies in the field of gasification process for face mask wastes play a significant role in addressing the environmental issues associated with these wastes and harnessing their potential as an important energy source. On the other hand, machine learning techniques offer a promising approach to predict the environmental, energy, and exergy performances of the gasification process. This study addressed the utilization of machine learning techniques on the gasification process of face mask wastes. Various polynomial regression machine learning algorithms are developed for syngas lower heating value, exergy and cold gas efficiencies, and emission level and their performances are checked. Remarkable precision of machine learning algorithms in forecasting the response variables is evidenced by the impressive outcomes. In fact, the majority of cases yield R-sq values surpassing 98%, thus highlighting their effectiveness. Specifically, when it comes to exergy and cold gas efficiencies, and emission, the machine learning algorithms achieve exceptional R-sq values of 99.85%, 98.93%, and 99.33%, respectively. These exceptional results confirm the credibility and accuracy of these algorithms in providing precise predictions. Leveraging the power of artificial intelligence not only contributes to the development of more sustainable energy systems but also helps in making informed decisions regarding process design and operation.

Experimental study on preheating and salt circulation performance of a single receiver tube based on induction heating

The design of a light source for a molten salt receiver experimental system has become challenging owing to the complex heating characteristics of the half-circumference surface during operation. Electromagnetic induction heating is an innovative technology that can replicate a half-circle heating scenario. However, its feasibility must be verified. In this study, we constructed a single receiver tube experimental system using induction heaters and developed a 3D numerical model coupling electromagnetic field to analyze the tube temperature distribution and molten salt temperature rise during preheating and salt circulation, considering various parameters. The results indicated that the numerical simulation agreed well with the experimental results, and the induction heater successfully reproduced the half circumference heating scenario. During preheating, a lower heat flux and higher wind speed result in a more uniform temperature distribution along the circumference of the tube wall, facilitating comprehensive preheating. During salt circulation, the heat flux and inlet salt mass flow significantly affected the temperature of the tube wall but had a relatively small effect on the back-side wall. Wind speed had the opposite effect, which was related to the arrangement of the experimental site. A higher heat flux, lower wind speed, and higher inlet salt mass flow led to a higher temperature increase in the molten salt.

Ammonia-enriched biogas as an alternative fuel in diesel engines: Combustion, performance and emission analysis

This study investigates the potential of ammonia as a secondary fuel in diesel engines, amidst the rising interest in alternative fuels and the growth of electric vehicles. Unlike hydrogen, with its higher flammability and safety concerns, ammonia offers a viable, sustainable fuel source. A single-cylinder diesel engine was utilized to assess engine performance and combustion characteristics using ammonia gaseous blends. Ammonia was combined with biogas to mitigate its corrosive effects and compensate for its lower heating value. Th entire best conducted with constant ammonia flow rate of 30 LPM. Diesel was mixed with biogas in compositions of 10 LPM, 20 LPM and 30 LPM, and tested under engine loads of 25%, 50%, 75%, and 100%. The blend with the highest ammonia concentration (B30B3) exhibited the largest heat release rate, highlighting a strong correlation between ammonia content and heat release levels. This is attributed to the premixed combustion phase and the accelerated flame speed associated with ammonia. An increase in ammonia content resulted in higher brake thermal efficiency and reduced brake specific fuel consumption. All ammonia-inclusive blends showed a decrease in hydrocarbon and carbon monoxide emissions, with the lowest emissions observed in the B30B3 blend. However, the high flammability of biogas in the B30B3 blend, compared to diesel, and enhanced fuel atomization, led to increased nitrogen Oxides formation. The results clearly indicate that combination of ammonia along with the biogas enhances the combustion and reduces greenhouse gas emissions. Findings of this study provides valuable insights into the use of ammonia as a sustainable alternative in diesel engines, offering a improved balance between combustion efficiency and environmental impact.

Influencing factors and identifying precursors in phenolic compounds formation from tobacco extracts pyrolysis

Tobacco extracts is one of the important flavors used in tobacco products, however, some toxic phenolic compounds (phenol, o-Cresol, p-Cresol, catechol, and hydroquinone) are formed during pyrolysis. In this study, the effects of temperature, heating rate, carrier gas atmosphere, and potassium salts on the formation of phenolic compounds by the pyrolysis of tobacco extracts were investigated quantitatively. The characteristics of phenols formation by five phenol-producing precursors (chlorogenic acid, protein, rutin, glucose, and fructose) were further studied. The results showed that with increasing temperature (300~500 ℃), the phenols yields first increased and then decreased, reaching the maximum at about 450 ℃. The yields of phenol and catechol can be significantly decreased by air atmosphere, lower heating rate, and addition of potassium acetate. It was further proved that chlorogenic acid, protein, and rutin are important precursors of phenolic compounds, and chlorogenic acid had the highest phenol yield of 18178.52μg/g. Moreover, combined with the content of each precursor in the extracts, it was calculated that 83.6% of the phenol formed at 350 ℃ came from protein and chlorogenic acid, with chlorogenic acid contributing 41.52%. Potassium acetate decreased the formation of phenol and catechol mainly by acting on chlorogenic acid, inhibiting them by 54.17% and 57.26%, respectively; however, it promoted the cresols formation from these precursors to varying degrees during pyrolysis.

MXene/biochar composites for enhanced wastewater reclamation and bioenergy production: A kinetics and thermodynamics study

The study explores the synthesis and utilization of biochar (BC) and multi-layer MXene to MXene/biochar (MB) composites for wastewater treatment. Simultaneously, it also investigates their energy generation potential through biomass and soil property assessments. The integrated column and batch treatments have shown significant results, elevating total dissolved solids from 63.7 to 125.5 mg L-1 with column treatment, while reducing them to 6.37 % and 1.35 % with BC and MB treatment, respectively. BC with high carbon content, demonstrated increased hydrophobicity, which was amplified by the integration of MXene, thereby enhancing its potential for advanced wastewater treatment. Treated wastewater exhibited elevated nutrient concentrations (Ca, Cu, Fe, K, Na, and NH4+), promoting the growth of Pennisetum purpureum. WW_B shows promising energy potential, with a higher heating value of 25.03 MJ kg-1 and a lower heating value of 23.57 MJ kg-1. They demonstrated high volatile matter exceeding 70.9 wt. %, and a fixed carbon from 10.02-27.53 wt. %, signifying their potential for efficient conversion and bio-oil yield during pyrolysis. The ultimate analysis emphasized significant carbon, with oxygen content ranging from 43.42-47.78 wt. %., influencing combustion characteristics. MT_B exhibited its suitability for energy production through thermochemical conversion, underlined by its high flammability and low volatile ignition values. In the absence of BC, the Ea ranged from 24.77-77.88 kJ mol-1 in wastewater and from 21.67-69.6 kJ mol-1 in MB treated wastewater. Meanwhile, when soil contained BC and was irrigated with wastewater, the Ea varied from 24.66-80.91 kJ mol-1. In the case of MB treated wastewater, it ranged from 25.01-75.79 kJ mol-1. The research thereby affirms the potential of MB composites to advance water and energy sustainability setting us for broader nexus-based applications.

Thermal performance evaluation of hempcrete masonry walls for energy storage in cold weather

During winter, buildings tend to consume a lot of energy for heating due to insufficient insulation of their envelopes. To address this issue, this study explores the use of materials with low thermal conductivity and high specific heat capacity, such as hempcrete, to minimize energy losses through the building envelope. The study suggests optimizing hempcrete components to enhance their thermal properties and evaluates the stored and lost thermal energy to improve the overall thermal performance of building envelopes. Twenty-five hempcretes are experimentally produced and thermally characterized. The thermal assessment also includes some hemp concretes from the literature for comparison purposes. ANSYS Fluent software is used to model the hempcrete walls in a transient state in terms of thermal storage capacity and losses in cold weather (e.g., −20 °C). Results show that stored energy is mainly affected by the product of hempcrete ρ and Cp values, while lost energy depends on thermal conductivity and diffusivity. The highest stored energy over 24 h is observed at 1.91 and 5.54 MJ/m2 for HC3 (literature) and AAFA-NaOH (present study), respectively, with a difference of 190 %. Further, the lowest values for lost energy are 0.44 and 0.42 MJ/m2 for HC2 (literature) and S2-CA (present study), respectively. To combine both stored energy and lost energy together, HC2 shows the best performance for the literature walls with lost energy of 0.44 MJ/m2 and stored energy of 1.82 MJ/m2; however, the present S2-CA hempcrete has lower lost energy at 0.42 MJ/m2 and higher stored energy at 3.07 MJ/m2. Additionally, a present C + Li + 30 %SF hempcrete has a similar lost energy of 0.46 MJ/m2 but a higher stored energy of 3.36 MJ/m2. The increasing hemp content has been noticed to increase stored energy by up to 86 % and reduce lost energy by 14.8 %.

Energy, environmental and economic analysis of low GWP refrigerant heat pumps for simultaneous heating and cooling applications

Industries such as hotels, pharmaceuticals, dairy and food and beverage units require heating and cooling for their functional requirements. These industries mostly use fossil fuel-fired boilers for heating (hot water at 60 to 90 °C) and vapor compression refrigeration systems for cooling (−30 to 5 °C), which results in higher primary energy consumption and CO2 emissions. Heat pumps (HPs) are a sustainable option for meeting the simultaneous heating and cooling demands. However, HPs use synthetic refrigerants with high global warming potential (GWP). Therefore, this research aims to evaluate the potential of low and medium-temperature HPs using low GWP refrigerants such as R744, R290, R600a, R161, R1234yf, R1234ze(E) and R1233zd(E). The best refrigerant for the HPs is proposed based on energy efficiency, environmental impact and economic feasibility as critical factors, compared with the conventional high GWP refrigerant (R134a). The occurrence of pinch points across the gas cooler/condenser is evaluated in the analysis. Life cycle climate performance (LCCP) is assessed to study the environmental impact. Also, the operating costs of these HPs are estimated and compared with the conventional systems used in the industry. Results show that R744 HP is an energy-efficient and clean solution for simultaneous heating and cooling applications, primarily at higher temperature lift (lower Tw,i and higher Tw,o) conditions.

Numerical investigation of bubble dynamics and flow boiling heat transfer in cylindrical micro-pin-fin heat exchangers

Micro-pin-fin evaporators are a promising alternative to multi-microchannel heat sinks for two-phase cooling of high power-density devices. Within pin-fin evaporators, the refrigerant flows through arrays of obstacles in cross-flow and is not restricted by the walls of a channel. The dynamics of bubbles generated upon flow boiling and the associated heat transfer mechanisms are expected to be substantially different from those pertinent to microchannels; however, the fundamental aspects of two-phase flows evolving through micro-pin-fin arrays are still little understood. This article presents a systematic analysis of flow boiling within a micro-pin-fin evaporator, encompassing bubble, thin-film dynamics and heat transfer. The flow is studied by means of numerical simulations, performed using a customised boiling solver in OpenFOAM v2106, which adopts the built-in geometric Volume of Fluid method to capture the liquid–vapour interface dynamics. The numerical model of the evaporator includes in-line arrays of pin-fins of diameter of 50μm and height of 100μm, streamwise pitch of 91.7μm and cross-stream pitch of 150μm. The fluid utilised is refrigerant R236fa at a saturation temperature of 30 °C. The range of operating conditions simulated includes values of mass flux G=500–2000kg/(m2s), heat flux q=200kW/m2, and inlet subcooling ΔTsub=0–5K. This study shows that bubbles nucleated in a pin-fin evaporator tend to travel along the channels formed in between the pin-fin lines. Bubbles grow due to liquid evaporation and elongate in the direction of the flow, leaving thin liquid films that partially cover the pin-fins surface. The main contributions to heat transfer arise from the evaporation of this thin liquid film and from a cross-stream convective motion induced by the bubbles in the gap between the cylinders, which displace the hot fluid otherwise stagnant in the cylinders wakes. When the mass flow rate is increased, bubbles depart earlier from the nucleation sites and grow more slowly, which results in a reduction of the two-phase heat transfer. Higher inlet subcooling yields lower two-phase heat transfer coefficients because condensation becomes important when bubbles depart from the hot pin-fin surfaces and reach highly subcooled regions, thus reducing the two-phase heat transfer.

A New Method for the Techno-Economic Analysis and the Identification of Expansion Strategies of Neutral-Temperature District Heating and Cooling Systems

Neutral-temperature district heating and cooling (NT-DHC) is a recent concept in the district heating sector. The current literature does not directly address the ability to create comprehensive master plans for NT-DHC systems and reliably model their performance. This research presents a new approach for the evaluation and planning of NT-DHC systems. The methodology involves the use of a knapsack optimization algorithm to perform a comprehensive analysis of the conditions that make the NT-DHC solution competitive against individual heating and cooling technologies. The algorithm determines the optimal combination of potential extensions that maximizes overall economic value. The results of a case study, which was conducted in Italy, show that NT-DHC is more suitable in dense urban areas, while air-to-water heat pumps are better suited for low heat density zones. This methodology aims to reduce the risks associated with energy demand and provide more certainty about which areas a network can expand into to be competitive. It is targeted at energy planners, utilities experts, energy engineers, and district heating experts who require assistance and guidance in the planning and early stages of designing a NT-DHC system. This method might enable pre-feasibility studies and preliminary design to determine the opportunities and limitations of a system of this kind from an economic and technological perspective.

Investigation on heat transfer characteristics of multi-duct Trombe wall based on multi-mode heat exchange in winter

For the areas where solar energy resources are available and the demand is high, the low heat transfer efficiency of the traditional Trombe wall needs to be solved, so this study combines the traditional Trombe wall with tubular solar collectors and proposes a form of Trombe wall with multi-pipe and multi-heat transfer modes. Numerical simulation analysis is conducted based on the measured data near the wall surface of residential buildings in Zhengzhou City, China, in December. The thermal performance of different heat transfer modes is evaluated based on the simulation results, and the structural form of the multi-duct Trombe walls is optimized. The results show that the coupled heat transfer mode achieves the highest thermal efficiency. Compared with the traditional interlayer heat transfer mode, the coupled heat transfer mode has a faster start-up speed and more stable performance, with a 27.8 % increase in average daily thermal efficiency and a 36 % increase in heating capacity. Research has found that the 9-duct multi-duct Trombe wall performs better in terms of overall performance. Increasing the number of branch pipes further has limited effect on improving thermal performance. When the diameter of the heat collection branch pipe is 60 mm, the multi-duct Trombe wall achieves the highest average daily thermal efficiency of 70.3 %; adopting a non-uniform pipe distribution mode with the center distance of the middle 5 branch pipes being twice that of the other branch pipes, the Trombe wall achieves the highest average daily thermal efficiency and heating capacity.

Formulation & Evaluation of Poly-Herbal Ointment

Abstract: Wound healing is a complex process of recovering the forms & functions of injured tissues. The process is tightly regulated by multiple growth factors & cytokines released at the wound site. Any alternations that disrupt the healing process would worsen the tissue damage and prolong repair process. Various conditions may contribute to impaired wound healing including infections underlying diseases and medications. Salves, or ointments, are topical products in which the herbs are extracted into vegetable oils by maceration at either room temperature for a specified length of time, in a low heat infusion or in a higher heat decoction. Numerous studies on the potential of natural products with anti-inflammatory, anti-bacterial, anti-fungal properties as wound healing agents have been performed .Their medicinal properties can be contributed by the content of phytochemical constituents such as Azadirachta indica (Neem leaves),Triticum (wheats), Vitis vinifera(Grape seeds),Helianthus annus (sunflower seeds), Oryza sativa (brown rice)