Sufficient Heat Research Articles

Fast Design and Numerical Simulation of a Metal Hydride Reactor Embedded in a Conventional Shell-and-Tube Heat Exchanger

The purpose of this work is to present a convenient design approach for metal hydride reactors that meet the specific requirements for hydrogen storage. Three methods from the literature, the time scale, the acceptable envelope, and the reaction front, are used to estimate the maximum thickness of the bed allowing for sufficient heat transfer. Further heat transfer calculations are performed within the framework of standardized heat exchanger via the homemade design software, to generate the complete geometry and dimensions of the reactor. LaNi5 material packed in tubular units based on conventional shell-and-tube heat exchanger is selected for analysis for an expected charging time of 500 s, 1000 s, and 1500 s. Apparently, the smaller the expected charging time, the smaller the bed thickness and hence the diameter of the tubular units. After comparison, the method of reaction front was adopted to output standard tube diameters and calculate the weight of the reactor. Significant weight differences were found to result from the varying wall thickness and number of tubes. In general, the shorter the expected charging time, the more tubular units with a small diameter will be built and the heavier the reactor. Fluent 2022 R2 was used to solve the reactor model with a tube diameter of 50 mm supposed to fulfill a charging time of 1500 s. The simulation results revealed that the reaction fraction reaches its maximum and the hydrogen storage process is completed at 500 s. However, because the calculation is conducted on meeting the heat exchange requirements, the average temperature of the bed layer is close to the initial temperature of 290 K and stops changing at 1500 s. The applicability of the method to the design of metal hydride reactors is thus confirmed by the temperature and reaction fraction judgment criteria.

Localizing weather forecasts for enhanced heat load forecast accuracy in urban district heating systems

ABSTRACT Weather forecasts are essential for district heating (DH) utility operations as they prepare the utility for future consumption, thus ensuring optimal operation by supplying sufficient heat while keeping costs low. Weather forecasts are usually converted into heat demand forecasts, which are used for production planning and control of the temperatures in the network. Hence, increasing the accuracy of weather forecasts will lead to improvements in the system's operational performance. However, numerical weather predictions (NWPs) are computed over the earth as grid values, and NWPs are designed for rural areas, not urban areas. Therefore, we propose to localise the weather forecasts to the urban environment by calibrating them using Model Output Statistics. We show that localising weather forecasts (removing the bias) leads to enhanced accuracy in the heat demand forecasts. In our case study, localised weather forecasts lead to an error reduction between 1.5% and 2.5% when compared to forecasts using uncalibrated NWPs.

Optimizing daylighting in lecture halls within hot-arid climates through modification of glazing systems with light-shelves: A parametric design approach

This study focused on enhancing the balance between sufficient daylighting and heat mitigation in lecture halls, set within the challenging hot-arid climate of Saudi Arabia, through the optimization of window designs and the incorporation of light-shelves. To achieve this, a combination of in-detail Parametric Sensitivity Analyses (PSA) was performed in the first stage to find the best configuration of windows, while a multi-objective optimization (MOO) strategy was applied in the second stage considering multiple objectives in each stage. Before running both analyses, the simulation model was validated by field measurement. The optimization results show that the optimal window configurations obtained through PSA and MOO offer significant potential for improving daylighting performance, energy efficiency and comfort. In terms of the overall best solutions from PSA and MOO, the PSA demonstrated substantial improvements, with Useful Daylight Illuminance (UDI) rising by 46.31% to 55.36%, glare decreasing by 52.17% to 82.61% and Energy Use Intensity (EUI) improving by 0.89% to 2.63%. Additionally, MOO solutions yielded even more significant enhancements, increasing UDI by 43.58% to 58.37%, reducing glare by 95% to 100% and enhancing EUI by 1.81% to 3.88%. This has resulted in a more evenly distributed and efficient daylighting throughout the space.

Response of Matching Degree between Precipitation and Maize Water Requirement to Climate Change in China

The synchronicity of rain and heat in the summer of China’s monsoon region provides sufficient water and heat resources for maize growth. However, the intra-annual distribution of precipitation and the probability of extreme precipitation have been inevitably altered by the ongoing climate change, thus affecting the matching degree between precipitation and crop water requirements (MDPCWR). Evaluating the extent to which the MDPCWR will change in the future is of great importance for food security and the sustainable management of water resources. In this study, considering that different growth stages of crops have different sensitivities to water stress, the AquaCrop model was used to calculate the MDPCWR more accurately. In addition, a cumulative distribution function-transform (CDF-t) method was used to remove the bias of 11 global climate models (GCMs) under two typical emission scenarios (SSP2-4.5 and SSP5-8.5) from phase six of the Coupled Model Intercomparison Project (CMIP6). A comprehensive investigation was conducted on how maize growth, water consumption, and the MDPCWR will respond to future climate change with CO2 concentration enrichment in the Huang–Huai–Hai (3H) region in China by driving a well-tested AquaCrop model with the bias-corrected GCMs outputs. The results indicate the following: (1) The CDF-t method can effectively remove seasonal bias, and it also performs well in eliminating the bias of extreme climate events. (2) Under the SSP2-4.5 scenario, the average maximum temperature will increase by 1.31 °C and 2.44 °C in 2021–2050 and 2051–2080, respectively. The average annual precipitation will increase up to 96.8 mm/year, but it will mainly occur in the form of heavy rain. (3) The increased maize evapotranspiration rate does not compensate for the decreased crop water requirement (up to −32 mm/year), due to a shorter growth cycle. (4) The farmland cultivation layer is not able to hold a significant amount of precipitation, due to the increased frequency of heavy rains, resulting in increased irrigation water requirements for maize over the next two periods, with the maximum value of 12 mm/year. (5) Under different scenarios, the projected future MDPCWR will decrease by 9.3–11.6% due to changes in precipitation patterns and crop water requirements, indicating that it will be more difficult for precipitation to meet the water demand of maize growing in the 3H region. The results can provide comprehensive information to understand the impact of climate change on the agricultural water balance and improve the regional strategy for water resource utilization in the 3H region.

Detailed kinetic modeling of catalytic oxidative coupling of methane

The oxidative coupling of methane (OCM) at high temperature over monolithic Pt-based catalysts operated at short contact times is investigated as an attractive method for methane upgrading to higher value products like ethylene and acetylene. An experimental measurement campaign aiming at elucidating the effect of operation parameters on the catalyst performance revealed that lower N2 dilution, lower CH4/O2 ratio, and higher space velocities promote high C2 yields. A maximum C2 yield of 10 % with 94 % CH4 conversion was obtained at a CH4/O2 ratio of 1.1, 50 % N2 dilution, and a space velocity of 4.5 × 105 h−1. Since both heterogenous and homogenous gas-phase chemistry together are required for determining C2 formation pathways, a detailed OCM surface reaction mechanism over Pt is presented consisting of 26 species and 86 reactions that are consistent from the view of thermodynamics and micro-kinetic reversibility. The combination of this OCM surface mechanism with a detailed gas-phase mechanism allows a numerical micro-kinetic description of the experimental measurements. The simulations presented in this study suggest that C2 formation takes place in the gas-phase at temperature above 1200 K with both oxidative and pyrolytic pathways for methane dehydrogenation to form CH3 radicals, whose coupling results in C2H6, C2H4 and C2H2 formation. Furthermore, the simultaneous presence of sufficient oxygen content and heat are vital for high C2 species yields.

An assessment of model capability on rapid intensification prediction of tropical cyclones in the South China Sea

The absence of robust quantitative evaluation methods has led to insufficient knowledge of models capability on the rapid intensification (RI) prediction of tropical cyclones (TCs). In this study, we propose a method and define some indicators aiming to evaluate model capability on predicting RI in a more accurate manner. An assessment of model predictive capability on RI of TCs based on 10 years of operational forecasts has been conducted using different RI criteria. The Tropical Regional Atmosphere Model for the South China Sea of China Meteorological Administration (CMA-TRAMS) and the European Centre for Medium-Range Weather Forecasts (ECMWF) high resolution (HRES) operational forecasts were used. Analysis results revealed that the criterion of 6-hour sea level pressure (SLP) change is more appropriate to be used in RI operational forecast. The maximum lead time (MLT) of CMA-TRAMS and HRES was 72 and 78 h, and the maximum deviation of RI occurrence time of CMA-TRAMS and HRES was 48 h delay and 24 h ahead, respectively. Overall results suggest that the model predictive capability of RI is currently limited, and both models have inadequate capability in providing sufficient heat and energy to support RI in the long run. A tendency of CMA-TRAMS to have a lag in RI occurrence time was also demonstrated due to an air-sea interaction lag resulting from the fixed skin sea surface temperature used. Results of the present study provide insights and could be the basis for future efforts on improving parametrization schemes for properly describing RI process of TCs.

Review of NIR-responsive ''Smart'' carriers for photothermal chemotherapy.

This review focuses on the versatile applications of near-infrared (NIR)-responsive smart carriers in biomedical applications, particularly drug delivery and photothermal chemotherapy. These carriers demonstrate multi-responsive theranostics capabilities, including pH-dependent drug release, targeted delivery of chemotherapeutics, heat-mediated drug release, and photothermal tumor damage. Biological samples are transparent to NIR light with a suitable wavelength, and therefore, NIR light is advantageous for deep-tissue penetration. It also generates sufficient heat in tissue samples, which is beneficial for on-demand NIR-responsive drug delivery in vivo systems. The development of biocompatible materials with sufficient NIR light absorption properties and drug-carrying functionality has shown tremendous growth in the last five years. Thus, this review offers insights into the current research development of NIR-responsive materials with therapeutic potential and prospects aimed at overcoming challenges to improve the therapeutic efficacy and safety in the dynamic field of NIR-responsive drug delivery.

Improved tumour delivery of iron oxide nanoparticles for magnetic hyperthermia therapy of melanoma via ultrasound guidance and 111In SPECT quantification.

Magnetic field hyperthermia relies on the intra-tumoural delivery of magnetic nanoparticles by interstitial injection, followed by their heating on exposure to a remotely-applied alternating magnetic field (AMF). This offers a potential sole or adjuvant route to treating drug-resistant tumours for which no alternatives are currently available. However, two challenges in nanoparticle delivery currently hinder the effective clinical translation of this technology: obtaining enough magnetic material within the tumour to enable sufficient heating; and doing this accurately to limit or avoid damage to surrounding healthy tissue. A further complication is the lack of established methods to non-invasively quantify nanoparticle biodistribution, which is necessary to evaluate the performance of improved delivery strategies. Here we employ 111In radiolabelling and single-photon emission computed tomography (SPECT) to non-invasively quantify distribution of a clinical grade iron-oxide-based nanoparticle in a mouse model of melanoma. We show that compared to manual injection, ultrasound guided delivery together with syringe-pump-controlled infusion improves both the nanoparticle concentration within the tumour, and the accuracy of delivery - reducing off-target peri-tumoural delivery. Following AMF heating, injected melanomas shrank significantly compared to non-injected controls, validating therapeutic efficacy. Systemic off-target delivery was quantified and extrapolated to predict off-target energy absorbance within safe limits for the main sites of background accumulation. With many nanoparticle-based therapies currently in development for cancer, this image-guided delivery strategy has wide potential impact beyond the field of magnetic hyperthermia. Future use in representative patient cohorts would also be enabled by the high clinical availability of both SPECT and ultrasound imaging.

Anti-icing system based on multi-level micro-nano and electric heating dual structure

The potential application value of superhydrophobic surfaces with anti-icing and de-icing properties in aerospace, telecommunications cables, energy and other fields has always been an important research topic. In this paper, a kind of superhydrophobic surface with stable structure, sufficient heat, excellent heat transfer performance and mass production was prepared based on elastic material. In this study, the multi-stage micro-nano rough structure is synthesized by ingenious pressing and mold closing control, and the surface contact angle of the prepared sample can reach 159°. The multi-stage micro-nano rough structure on the surface of the experimental sample can make the water droplets form a large number of cavitation, which can delay the icing of static water droplets. The height difference on both sides of (Un)pressed mesh surface makes the water droplets freeze asymmetrically, so (Un)pressed mesh surface has excellent anti-icing ability. The experimental sample is connected with 24 V direct current, and the average resistivity is 1.403 Ω·cm. The temperature can be raised to about 60 °C in one minute. The prepared sample has stable temperature, good electrical conductivity, sufficient heat generation, excellent heat transfer performance and high anti-icing efficiency. This study expands the design idea of anti-icing of aircraft rotor.

Torrefaction of Willow in Batch Reactor and Co-Firing of Torrefied Willow with Coal

The torrefaction process represents a thermal conversion technique conducted at relatively low temperatures ranging between 200 to 300 °C. Its objective is to produce fuel with a higher energy density by decomposing the reactive portion of hemicellulose. In this study, the kinetics of mass loss during torrefaction were investigated for willow. The experiments were carried out under isothermal conditions using thermogravimetric analysis. Batch torrefaction reactor designs were conducted and explained in detail. Co-combustion of willow with hard coal (origin: Katowice mine) in different mass ratios (25% biomass + 75% coal, 50% biomass + 50% coal, and 75% biomass + 25% coal) was conducted in addition to raw biomass torrefaction. TG/MS analysis (a combination of thermogravimetric analysis with mass spectrometry analysis) was performed in the research. The optimal torrefaction conditions for willow were identified as an average temperature of 245 °C and a residence time of 14 min, resulting in the lowest mass loss (30.15%). However, it was noted that the composition of torgas, a by-product of torrefaction, presents challenges in providing a combustible gas with sufficient heat flux to meet the energy needs of the process. Prolonged residence times over 15 min and higher average temperatures above 250 °C lead to excessive energy losses from volatile torrefaction products, making them suboptimal for willow. On the other hand, the co-combustion of torrefied biomass with hard coal offers advantages in reduced sulfur emissions but can lead to increased NOx emissions when biomass with a higher nitrogen content is co-combusted in proportions exceeding 50% biomass. This paper summarizes findings related to optimizing torrefaction conditions, challenges in torgas composition, and the emissions implications of co-combustion.

Hygienic indicator bacteria in the 2 species of wild-caught Japanese cicadas, large brown cicadas and robust cicadas

Abstract Entomophagy is considered a potent dietary practice to replace animal protein due to its highly nutritious and environmentally sustainable features. While entomophagy has many advantages, safety and security concerns still remain, especially for wild-caught insects, not farm-reared insects. This study aimed to clarify the potential microbiological hazards of eating wild-caught cicadas. Large brown cicadas and robust cicadas, which were commonly inhabited in Japan, were caught and examined the hygienic indicator bacteria, standard plate counts (SPC) and Enterobacteriaceae. Then, representative colonies of Enterobacteriaceae were identified. Also, the distribution of bacteria, i.e. the surface or inside the body of the cicadas, and the changes in the bacterial number during the storage of the dead cicadas were examined. SPC was in the range of 3.0 to 9.0 log CFU/g and Enterobacteriaceae was detected in the most of cicadas. Most of the Enterobacteriaceae species identified were biosafety level 2 pathogens or opportunistic pathogens. SPC and Enterobacteriaceae were distributed both on the surface and in the body of the cicadas. SPC and Enterobacteriaceae rapidly increased in the dead cicadas during the storage (at 25 °C). In this study, it is concluded that sufficient heat cooking and proper cold storage should be necessary for the safe consumption of cicadas as food.

USE OF AQUEOUS EMULSIONS OF WASTE MOTOR OILS AS HIGH-EFFICIENCY FUEL

This work presents the methodology of using wasted lubricants as a highly efficient fuel as water-fuel emulsions, which containing up to 70% water. They burning in burners under conditions of action high-frequency electrical discharges. It has been shown that the viscosity of a water-oil emulsion with a high water part (more than 50%) outweighs the viscosity of pure oil. With a low water part (10-20%), the emulsion is the most stable. With more water, the semi-delamination time decreases. Therefore, it is necessary to spray the emulsion near the site of the making. The results of natural experiments and prospects of the proposed methodology are given. Combustion of a water-in-oil emulsion with a volume content of 50-70% water is possible in the presence of a discharge of high-frequency signals. Independent combustion of the emulsion without the support of a small diesel fuel torch is possible with sufficient heating of the combustion chamber. To implement combustion, the burner for liquid fuels was modernized by adding a pre-chamber between the burner and the nozzle or boiler. To organize effective spraying of water-oil emulsion with a large amount of water (up to 70%), it is necessary to ensure sufficient heating of the emulsion in the pipelines. First, this reduces its viscosity, making it easier to pump the emulsion through the supply systems of the spraying device. Otherwise, it is necessary to serve under a pressure, so that the water at a high temperature (above 100 ° C) is remained liquid. When leaving the nozzle under pressure, the water “boils” (“micro-bump” drops of emulsion), which further disperses the burning liquid. The peculiarity of this burner is the action of a high-frequency streamer in the area of spraying emulsion droplets inside the forechamber. The use of water-fuel emulsions allows to reduce emissions of nitrogen oxides and carbon monoxide, reduce its fire and explosion hazard during transportation and storage. Effectiveness assessment of this complex showed that energy expenditures can reach percents of levels compared to full heat release.Thus, the possibility of using such water-oil emulsions as alternative fuels is shown. Keywords: water-oil emulsion, high-frequency electric discharge, combustion, torch.

Intercropping Forage Sorghum with Sunnhemp at Different Seeding Rates to Improve Forage Production

Forage sorghum (Sorghum bicolor (L.) Moench) is well established in the Texas High Plains as a drought-tolerant forage that often requires additional feed to provide adequate protein for livestock. Intercropping sunnhemp (Crotalaria juncea L.), a legume, with forage sorghum, may increase crude protein. However, the optimal intercrop seeding ratio of sunnhemp to sorghum to improve crude protein content and maintain sufficient biomass is unknown. A two-year field experiment was conducted near Canyon, TX, USA, in 2020 and 2021 using sunnhemp intercropped at three seeding rates (16.8, 33.6, and 50.4 kg ha−1) with forage sorghum at four seeding rates (0, 2.8, 5.6, and 11.2 kg ha−1) under drip irrigation. This study was conducted to (1) evaluate growth potential for sunnhemp in a semiarid environment, (2) find a seeding ratio that can maintain forage sorghum dry matter production and improve forage quality, and (3) determine if a midseason harvest can be supported and further improve quality of the forage produced. Midseason, full-season, regrowth biomass, and forage quality were evaluated. Results indicated that a sunnhemp–forage-sorghum intercrop produced dry matter comparable to forage sorghum when sufficient heat units were obtained in the growing season. Forage with higher nutritive value was produced when the intercrop was harvested twice.

Coaxial one-side resistance spot welding for cross-lap joints of Al5052 and CFRP: Thermal process and strength evaluation

Coaxial one-side resistance welding (COS-RSW) is an advanced joining technology for the metal-plastic hybrid structure, which has great application potential in the lightweight design of body-in-white. In the present research, the Al5052-CFRP cross-lap joints were fabricated by COS-RSW with different welding conditions. The author-developed finite element (FE) code JWRIAN-RSW was employed to reproduce the multi-physics coupled phenomena of COS-RSW and predict thermal history. The influence of welding current and welding time on molten zone generation and joining strength was discussed in detail. The results showed that the developed FE model can predict temperature distribution and variation effectively, which were verified by the bonding zone observation and infrared thermal image measurement. Both welding current and welding time had a significant contribution to the Joule heat generation. While their influence on the molten zone growth during heating and cooling stage was distinct. The maximum joining strength of COS-RSW cross-lap joints can reach about 1380 N. The static tensile strength was improved significantly when the maximum interface temperature exceeded 340 °C and the failure mode altered into staged fracture. The strength degradation induced by significant CFRP decomposition was appeared when the predicted interface temperature reached 410 °C. For the COS-RSW joint of Al5052 and CFRP, it was better to improve the joining strength using longer welding time rather than higher welding current, which led to sufficient heat generation, persistent thermal conduction and elongated melting duration for sound joining.

Load study and structural analysis for CFETR divertor OVT

China Fusion Engineering Test Reactor (CFETR) is an important device for studying fusion reactor engineering in China. The Outer Vertical Target (OVT) are high heat load components of the divertors and work in a strong electromagnetic field, so they need sufficient heat removal capability and structural strength. In addition, due to activation of neutrons on materials, the OVT also needs to meet the requirements of Remote Handling (RH) maintenance. CFETR puts forward the concept of hybrid divertor-blanket, which cancels the cassette and adopts a separate structure. The lower part of the divertor is occupied by the breeding blanket, and the divertor target is fixed on the breeding blanket, to improve the RH maintenance efficiency and Tritium Breeding Ratio (TBR). In previous work, the structural design and thermal-hydraulic analysis of the OVT were completed. In this paper, load study and structural analysis was carried out to verify the structural strength of the OVT under experimental test conditions (including liquid pressure, nitrogen baking), normal operation conditions (including the impact of thermal stress under thermal load, gravity, working pressure, etc.) and extreme event conditions (Vertical Displacement Event (VDE) or Major Disruption (MD) event, including the impact of thermal stress under thermal load, gravity, working pressure, electromagnetic load, etc.). The results show that the OVT meets the requirements of heat removal and strength, and effectively promote the processing and manufacturing of the prototype of the OVT.

The Influence of the Deposition Speed during Friction Screw Extrusion Additive Manufacturing of AA6060

Solid-state additive manufacturing may solve critical issues typically arising during fusion-based additive manufacturing of high-strength aluminium alloys. In this work, the recently introduced Friction Screw Extrusion Additive Manufacturing (FSEAM) process was employed to manufacture wall-like rectangular builds of AA6060 T6 deposited with deposition speeds from 300 mm/min to 500 mm/min. All builds were manufactured at a tool rotation rate of 400 rpm with 1 mm layer thickness. The volumetric supply rates were adjusted to maintain constant build width. Solid builds were formed without major defects over the full range of deposition speeds. The process generated sufficient normal force and heat at all deposition speeds which resulted in manufacturing of defect free builds. The resulting average grain size was consistently below 5 micrometer throughout all builds independent of deposition speed or location through the height. Microhardness measurements revealed a decrease in hardness from a feedstock value of 80 HV to around 50 HV in all manufactured builds. Tensile tests in the building direction showed consistent results for all the samples as a result of defect-free parts, demonstrating a tensile strength of approximately 150 MPa, yield strength of 100 MPa, and uniform elongation of 12-15%. The fracture surfaces revealed large amounts of dimples at all deposition speeds in line with the high degree of plastic deformation preceding fracture observed from the tensile tests. The obtained results indicated that FSEAM is a promising process for solid-state additive manufacturing of aluminium alloys.

Genetic characterization of a multidrug-resistant Salmonella enterica serovar Agona isolated from a dietary supplement in Germany.

Salmonella enterica subsp. enterica serovar Agona has a history of causing food-borne outbreaks and any emergence of multidrug-resistant (MDR) isolates in novel food products is of concern. Particularly, in food products frequently consumed without sufficient heating prior to consumption. Here, we report about the MDR isolate, 18-SA00377, which had been isolated from a dietary supplement in Germany in 2018 and submitted to the German National Reference Laboratory for Salmonella. WGS-based comparative genetic analyses were conducted to find a potential reservoir of the isolate itself or mobile genetic elements associated with MDR. As a phylogenetic analysis did not yield any closely related S. Agona isolates, either globally or from Germany, a detailed analysis of the largest plasmid (295,499 bp) was performed as it is the main carrier of resistances. A combined approach of long-read and short-read sequencing enabled the assembly of the isolate's chromosome and its four plasmids. Their characterization revealed the presence of 23 different antibiotic resistance genes (ARGs), conferring resistance to 12 different antibiotic drug classes, as well as genes conferring resistance to six different heavy metals. The largest plasmid, pSE18-SA00377-1, belongs to the IncHI2 plasmid family and carries 16 ARGs, that are organized as two distinct clusters, with each ARG associated with putative composite transposons. Through a two-pronged approach, highly similar plasmids to pSE18-SA00377-1 were identified in the NCBI database and a search for Salmonella isolates with a highly similar ARG resistance profile was conducted. Mapping and structural comparisons between pSE18-SA00377-1 and these plasmids and Salmonella isolates showed that both the plasmid backbone and identical or similar ARG clusters can be found not only in Salmonella isolates, originating mostly from a wide variety of livestock, but also in a diverse range of bacterial genera of varying geographical origins and isolation sources. Thus, it can be speculated that the host range of pSE18-SA00377-1 is not restricted to Salmonella and its spread already occurred in different bacterial populations. Overall, this hints at a complex history for pSE18-SA00377-1 and highlights the importance of surveilling multidrug-resistant S. enterica isolates, especially in novel food items that are not yet heavily regulated.

Integration of heat sources for heat pumps of larger capacities

Heat pumps are seen as the predominant future heating system in many scenarios. However, with increasing integration of heat pumps sufficient heat sources can be a major obstacle, in particular at higher heating capacities and in existing buildings. The paper investigates two strategies to overcome limitations of the most common individual heat sources outdoor air and ground by the integration of two or more heat sources in order to enable a monovalent heat pump operation. By an integration of the ground for peak load coverage and air as base load the borehole heat exchanger field can be notably downsized, overcoming space limitations for the drilling and noise limitations due to a downsized air source. Compared to the individual air source the performance can be increased, while the system costs can be kept. Also the second strategy of the regeneration of the ground source allows for much smaller borehole fields, and the regeneration source can be refunded by cost savings due to a reduced total borehole length. Thus, performed simulations confirm that heat source integration has the potential to overcome limitations of individual heat sources while exploiting performance and cost benefits due to synergies between the sources.

Phase Mixing of Propagating Alfvén Waves in a Single-fluid Partially Ionized Solar Plasma

The phase mixing of Alfvén waves is one of the most promising mechanisms for the heating of the solar atmosphere. The damping of waves in this case requires small transversal scales, relative to the magnetic field direction; this requirement is achieved by considering a transversal inhomogeneity in the equilibrium plasma density profile. Using a single-fluid approximation of a partially ionized chromospheric plasma, we study the effectiveness of the damping of phase-mixed shear Alfvén waves and investigate the effect of varying the ionization degree on the dissipation of waves. Our results show that the dissipation length of shear Alfvén waves strongly depends on the ionization degree of the plasma, but more importantly, in a partially ionized plasma, the damping length of shear Alfvén waves is several orders of magnitude shorter than in the case of a fully ionized plasma, providing evidence that phase mixing could be a large contributor to heating the solar chromosphere. The effectiveness of phase mixing is investigated for various ionization degrees, ranging from very weakly to very strongly ionized plasmas. Our results show that phase-mixed propagating Alfvén waves in a partially ionized plasma with ionization degrees in the range μ = 0.518–0.657, corresponding to heights of 1916–2150 km above the solar surface, can provide sufficient heating to balance chromospheric radiative losses in the quiet Sun.

Experimental investigation on tool pin profile for defect-free multi-layered laminates using friction stir additive manufacturing

Friction stir additive manufacturing (FSAM) is a sub-set of solid-state additive manufacturing technique that falls under sheet lamination additive manufacturing. This technique employs friction stir welding (FSW) to produce large, multi-layered parts via the plate addition method. Sufficient heat generation and material mixing are the basic requirements of FSAM, which are primarily dependent on the tool pin profile and the optimal selection of process parameters. Therefore, three tools with distinct pin profiles were selected (plain cylindrical, cylindrical threaded, and taper threaded) at variable tool transverse speeds (20, 40, 60 mm/min). The current study investigates the influence of pin profile and welding speed on material mixing and heat generation, specifically in terms of defects produced between the bonded layers of aerospace aluminum alloy Al-7075. A tool rotational speed of 500 rpm and 1200 rpm with a tool tilt angle of 2.5° were employed for all three tools to develop a 4-layered laminate. It was observed that among all, taper threaded tool pins produced defect-free laminates at 500 and 1200 rpm for all three welding speeds. This was attributed to the higher microhardness with grain size ranging from 0.96 μm to 1.47 μm. Overall, a 95.61 % reduction in grain size was achieved using the taper threaded tool pin profile compared to the as-received base material. Microhardness was enhanced with the increase in transverse speed and building height, furtherer highlighted with statistical analysis.