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New biodegradable paper-based films are a hot research topic in the development of green agriculture. In this study, a black paper-based film coated with cooked tung oil with excellent mechanical properties, a hydrophobic surface, high heat transfer and strong weather resistance was prepared by spraying high-pigment carbon black solution on the surface of base paper. The results showed that the surface-solidified oil film had a rough structure produced via the brush coating process using cooked tung oil. The base film of the black paper had a given hydrophobic structure, and the contact angle reached 98.9°. Cooked tung oil permeates into the inside of the paper base, and after curing, it forms a multi-dimensional network film structure. The maximum tensile stress of the black paper base film is about 123% higher than that of the original paper base film. The coloring of carbon black gives the black paper base film a heat conduction effect, and the average heat transfer rate reaches 15.12 °C/s. Cooked tung oil is combined with the paper-based fiber high-toughness layer to form a stable system. The existence of a cured film improves the basic mechanics and hydrophobicity, and the resistance to ultraviolet radiation and hot air is greatly improved. This study provides a feasible scheme for the application of a black paper base film coated with cooked tung oil. [ABSTRACT FROM AUTHOR]

In this work heat transfer papers were loaded with a new core–shell pigment based on precipitating thin shell of titanium dioxide on a core of rice husk silica ash TiO2/RHSA to be applied in dye sublimation printing of textile fabrics. Besides, 0.1% (w/w) cationic polyacrylamide (CPAM) and 1% (w/w) bentonite (Bt) were also added sequentially to improve drainage and filler retention of the paper hand-sheets made from bleached kraft bagasse pulps. The effect of the new core–shell pigment on the mechanical and barrier properties, thermal stability and surface morphology of modified paper sheets were investigated. In addition, the study of transfer printability and ease of dye release from paper to fabric in this heat transfer printing of polyester fabrics using silk-screen printing under different transfer parameters were studied. Also, fastness measurements including washing, light and perspiration of printing polyester fabric were also estimated. [ABSTRACT FROM AUTHOR]

To apply functional honeycomb panels (FHPs) in actual engineering projects, the heat transfer performance and intrinsic heat transfer mechanism of laminated honeycomb panels (LHPs, total thickness of 60 mm) with different structural parameters were investigated in this study by a heat flow meter. The results showed that (1) the equivalent thermal conductivity λequ of the LHP was almost independent of the cell size, when it consisted of a small single-layer thickness. Thus, LHP panels with a single-layer thickness of 15–20 mm are recommended. (2) A heat transfer model of LHPs was developed, and it was concluded that the heat transfer performance of LHPs depends greatly on the performance of their honeycomb core. Then, an equation was derived for the steady state temperature distribution of the honeycomb core. (3) The contribution of each heat transfer method to the total heat flux of the LHP was calculated using the theoretical equation. According to the theoretical results, the intrinsic heat transfer mechanism affecting the heat transfer performance of LHPs was revealed. The results of this study laid the foundation for the application of LHPs in building envelopes. [ABSTRACT FROM AUTHOR]

Insulation paper is the primary inter-turn insulation material for transformer windings. However, insulation paper is a poor conductor of heat and seriously impacts the natural convective heat dissipation in the winding oil channels. In order to study the convective heat transfer performance of the transformer vertical oil channel, the heat transfer characteristics of the two-dimensional boundary layer of the insulation paper–oil contact surface were analysed, and a characteristic number equation with a roughness correction factor was established. Based on the similarity principle and modelling theory, an experimental apparatus was designed to determine the convective heat transfer coefficient of the insulation paper–oil contact surface. Coefficients were obtained for different qualitative temperatures and characteristic lengths. Parametric fitting of the experimental data was carried out to obtain the correction factors. The results show that the natural convective heat transfer coefficient h of the insulation paper–oil contact surface is positively and linearly related to qualitative temperature and inversely related to characteristic length. For temperatures of 312.9 K to 328.1 K and characteristic lengths of 3 cm, h ranges from 116.15 to 144.38 W/(m2 · K). For temperatures of 319.0 K to 337.9 K and lengths of 6 cm, h ranges from 103.79 to 131.14 W/(m2 · K). The correction factor of the characteristic equation coefficient is 1.067. The maximum deviation of h calculated with a coefficient of 0.63 and an exponent of 0.25 is 5.93%. The results are essential for modelling the transformer space thermal circuit and solving the hot-spot temperature problem. [ABSTRACT FROM AUTHOR]

Worldwide, the need for thermal insulation materials used to increase the energy performance of buildings and ensure indoor thermal comfort is constantly growing. There are several traditional, well-known and frequently used thermal insulation materials on the building materials market, but there is a growing trend towards innovative materials based on agro-industrial waste. This paper analyses the performance of 10 such innovative thermal insulation materials obtained by recycling cellulosic and/or animal waste, using standardised testing methods. More precisely, thermal insulation materials based on the following raw materials were analysed: cellulose acetate, cigarette filter manufacturing waste; cellulose acetate, cigarette filter manufacturing waste and cigarette paper waste; cellulose acetate, waste from cigarette filter manufacturing, waste cigarette paper and waste aluminised paper; cellulose from waste paper (two types made by two independent manufacturers); wood fibres; cellulose from cardboard waste; cellulose from waste cardboard, poor processing, inhomogeneous product; rice husk waste and composite based on sheep wool, recycled PET fibres and cellulosic fibres for the textile industry. The analysis followed the performance in terms of thermal insulating quality, evidenced by the thermal conductivity coefficient (used as a measurable indicator) determined for both dry and conditioned material at 50% RH, in several density variants, simulating the subsidence under its own weight or under various possible stresses arising in use. The results showed in most cases that an increase in material density has beneficial effects by reducing the coefficient of thermal conductivity, but exceptions were also reported. In conjunction with this parameter, the analysis of the 10 types of materials also looked at their moisture sorption/desorption capacity (using as a measurable indicator the amount of water stored by the material), concluding that, although they have a capacity to regulate the humidity of the indoor air, under low RH conditions the water loss is not complete, leaving a residual quantity of material that could favour the development of mould. Therefore, the impact on indoor air quality was also analysed by assessing the risk of mould growth (using as a measurable indicator the class and performance category of the material in terms of nutrient content conducive to the growth of microorganisms) under high humidity conditions but also the resistance to the action of two commonly encountered moulds, Aspergillus niger and Penicillium notatum. The results showed a relative resistance to the action of microbiological factors, indicating however the need for intensified biocidal treatment. [ABSTRACT FROM AUTHOR]

The fabrication of most current thermal insulation materials from polymeric foams has created an unfavorable impact on the environment. With the aim of reducing the use of foam plastic, this paper focuses on honeycomb paperboard, an alternative thermal insulation material which is recyclable and cost-effective, and evaluates its heat transfer performance under different conditions. The experimental results show the effective thermal conductivity of honeycomb paperboard increases as the honeycomb height or the side length increases. This paper also establishes a novel theoretical model based on a newly developed convective heat transfer correlation to predict the effective thermal conductivity under different conditions. The model's results conform well to the experimental results, and the effect of convective heat transfer is investigated quantitatively using this model. As the vertical adiabatic boundary surfaces are replaced by honeycomb walls, the convection heat transfer strictly depends on the thermal boundary condition of the honeycomb walls and highly depends on honeycomb height and side length. • The novel theoretical models involving convective heat transfer are established under different conditions. • The different heat transfer paths are quantitatively investigated based on the proposed models. • Under the condition of hot-above and cold-below, convective heat transfer in honeycomb paperboard increases as the honeycomb height increases, but decreases as the side lengths increases. • Under the condition of cold-above and hot-below, convection heat transfer in honeycomb paperboard increases as the honeycomb height or the side length increases. [ABSTRACT FROM AUTHOR]

This paper considers a temperature-dependent thermal conductivity with memory property in a fractal space. The two-scale fractal derivative is adopted to model the temperature field in the spatial dimensions, and Caputo fractional derivative is used to describe its memory property. The variational iteration method is employed to solve the mixed model with great success. This paper offers a new window for studying intractable problems arising in porous media or unsmooth boundaries. [ABSTRACT FROM AUTHOR]

This paper presents the results of a severe accident parametric sensitivity study performed on a model of a generic integral pressurized water reactor (iPWR). The analyzed sequence is a loss of coolant accident (LOCA)-type scenario, postulating that safety systems are not available. In this work, a MELCOR 2.2 input deck of a generic iPWR was developed based on publicly available data. The iPWR used in this work is a generic iPWR with a thermal power of about 160 MWth, characterized by a compact steam generator and a submerged containment configuration. A hypothetical scenario considered in this work was an unmitigated small break LOCA leading to a severe accident with partial core degradation, due to the postulated assumptions. In the presented paper, 16 sensitivity cases were calculated and analyzed, focusing mainly on heat transfer, decay heat, and core degradation parameters. The selected parameters and their combination caused partial core degradation and showed significant differences in investigated variables such as core degradation and hydrogen generation, as well as examined CPU time consumption. This a preparatory work performed in the framework of the Horizon Euratom SASPAM-SA project, which aims to investigate the applicability and transfer of the operating large light-water reactor knowledge and know-how to the iPWR, taking into account European licensing analysis needs for the severe accident and emergency planning zone. [ABSTRACT FROM AUTHOR]

The performance of the Plate Indirect Evaporative Cooler (PIEC) can be effectively improved by incorporating baffles in the dry channel. However, in the dimensional influence of the baffles on PIEC performance there remains a research gap. In order to investigate the impact of baffle dimensions on the wet bulb efficiency, namely the average heat transfer coefficient and the cooling capacity of the PIEC, this paper proposed and verified a three-dimensional numerical model and method based on the species transport model and the Euler wall film model. At the same time, in order to obtain the equilibrium point between the enhanced heat transfer performance and the additional resistance induced by baffles, a comprehensive performance evaluation index is introduced. The results indicate that, under the same conditions, (1) the baffle effect on PIEC performance is significant at a lower inlet air velocity, and the wet bulb efficiency of the PIEC with baffles can be improved by 22.8%; (2) the baffle effect on PIEC performance is negative if its relative length exceeds 60% or the primary air inlet velocity surpasses 4 m/s under the conditions specified in this paper; and (3) the baffle effect on PIEC performance is significant when its channel height is lower and its channel width is larger, and the wet bulb efficiency of the PIEC with baffles can be improved by 29.3%. [ABSTRACT FROM AUTHOR]

This paper proposes a heat demand prediction model that analyzes the heat behavior of heat users, and analyzes the heat behavior data of heat users through a clustering algorithm to predict their heat demand. This paper is based on the supply-demand balance strategy to reduce the heat loss during the transmission of heat medium, and then improve the energy-saving efficiency of the boiler. The traditional boiler energy-saving and consumption reduction method is to optimize the boiler combustion parameters, improve the fuel combustion efficiency and waste heat recovery technology through the Internet of Things and big data technology. The method of balancing the heat-using end with the load of the boiler at low usage frequency is seldom considered. Therefore, this paper predicts the heat demand of the heat-using end by analyzing its thermal behavior, and balances the heat demand and boiler heat supply under the condition of meeting the heat demand. Finally, through simulation experiments, the validity of the model is verified, and the trend and data can be well predicted in the short-term heat demand prediction. [ABSTRACT FROM AUTHOR]

This paper introduces a novel design for a solar photovoltaic/thermal (PV/T) air collector that utilizes staggered fins. The collector features double-layer flow channels in the same direction, with the upper channel equipped with transparent wave plates, and the lower channel fitted with staggered fins. The paper includes a calculation scheme for wave plate heat balance. The numerical model of the collector is established and verified by experimental results. A numerical model is used to analyze the height combination of the upper and lower runner and the fin arrangement of the lower runner. The results indicate that, under the given environmental parameters, as the PV panel moves down, the overall air heat transfer capacity decreases. When the height combination of the upper/lower runner is 23 mm/105 mm, the maximum value is 53.741%. With the increase of fin spacing, the heat transfer capacity of the lower runner decreases. With the increase of the number of fin rows, the heat transfer capacity of the lower runner increases. When the equivalent diameter of the rectangular channel and the number of fin rows were 70 mm and 3 rows, respectively, the maximum solar energy comprehensive utilization efficiency was 56.261%. [ABSTRACT FROM AUTHOR]

This paper presents the continuation of experimental investigations conducted by the present authors to measure and compare the thermal and fluid dynamic performance of a residential hydronic air coil using nanofluids. The prior experiments were limited to testing only one volumetric concentration (1%) of aluminum oxide (Al2O3) nanofluid. They compared it with the base fluid, a 60% ethylene glycol/40% water mixture by mass (60% EG). The original tests revealed some deficiencies in the experimental setup, which was subsequently revised and improved. This paper summarizes the results of experiments from the improved test bed using three concentrations of Al2O3 nanofluids: 1, 2, and 3% volumetric concentrations prepared with an average particle size of 45 nm in a 60% EG dispersion. The test bed in these experiments simulates a small air handling system typical of heating, ventilation, and air conditioning (HVAC) applications in cold regions. Entering conditions for the air and liquid were selected to emulate typical commercial air handling systems operating in cold climates. Contrary to previous findings, our test results revealed that nanofluids did not perform as well as expected. Prior predictions from many analytical and numerical studies had promised significant performance gain. The performance of the 1% nanofluid was generally equal to that of the base fluid under identical inlet conditions. However, the performance of the 2% and 3% nanofluids was considerably lower than that of the base fluid. The higher concentration nanofluids exhibited heat rates up to 14.6% lower than the 60% EG and up to 44.3% lower heat transfer coefficient. The 1% Al2O3/60% EG exhibited a 100% higher pressure drop across the coil than the base fluid, considering equal heat output. This performance degradation was attributed to the inability to maintain nanofluid dispersion stability, agglomeration, and subsequent decline in the thermophysical properties. [ABSTRACT FROM AUTHOR]

Boiling heat transfer can be enhanced when the heater's surface morphology is altered. The paper discusses the use of the laser beam to produce efficient heat exchangers. Two types of samples were investigated with distilled water and ethyl alcohol as boiling agents. The specimens differed with the height of the microfins: 0.19 mm and 0.89 mm. It was observed that both of them enhanced boiling heat transfer in comparison to the smooth reference surface. However, the sample with higher microfins performed better, especially in the region of low temperature differences, where the heat flux was about three times higher than in the case of the smaller microfins. The comparison of the experimental data with selected models of boiling heat transfer revealed significant differences with regard to the heat flux. The laser-made samples dissipated larger heat fluxes than it could be anticipated according to the models. It might be linked with high surface roughness of the area between the microfins, generated as a result of the laser beam interaction with the surface. [ABSTRACT FROM AUTHOR]

This paper takes an old office building in Hefei as the research object to explore the influence of the thermal buffering performance of the case building buffer space on the air speed and thermal environment of the office space based on the field measurement and simulation. As the thermal buffer layer of the main space, the buffer space is the layout mode that follows the thermal transfer law. Building buffer space variables were evaluated and compared by orthogonal tests to determine the better combination of buffer space sizes. The results show that when the air speed is taken as the evaluation index, the influence of each buffer space on the indoor environment is ordered: courtyard > corridor > foyer; when the temperature is taken as the evaluation index, the influence of each buffer space on the indoor environment is ordered: courtyard > foyer > corridor. From the perspective of green transformation, this paper selects two better schemes. Through comparison, it is found that when the buffer space size is: corridor (16 m × 2 m × 3.3 m), courtyard (16 m × 12 m) and foyer (7.2 m × 6 m × 3.3 m) is the optimal scheme, the indoor air speed is increased by 0.1 m/s, and the temperature is reduced to 27.0 °C, which is within the thermal comfort range of the human body. It is found that optimizing the buffer space size of the case building can effectively improve its indoor air speed and thermal environment, and provide theoretical basis and reference for the green transformation of existing buildings of the same type in this area. [ABSTRACT FROM AUTHOR]

The building envelope is the interface between the external atmospheric conditions and the indoor environment. It contributes to approximately 60%-70% of the heating and cooling load. The building envelope constitutes walls, fenestrations, and roofs from which thermal transfer from the roof is significantly very high compared to walls in low-rise buildings. This research paper aims to provide recommendations for energy-efficient roof design considering roof form, material, and external coating suitable for various climate conditions of India. The paper's methodology consists of a literature review of related research papers, learnings from the roofing system of energy-efficient building case studies, and all possible energy-efficient roofing systems that would be simulated for energy efficiency and thermal comfort in five climate types of India. The expected outcome of this paper would be in the form of recommendations for roofing systems in different climate type and their potential for energy saving from the highest to the lowest. This research would be done in three stages viz, Step-1: Literature Review and case study of best practices: A review of the related literature and best practices examples would be done to formulate the maximum possible cases for the simulation. Step-2: The roofing systems, including building form, material (Thermal and insulation), and finishes (reflectance), would be simulated one by one for various climate types of India (composite, hot & dry, warm and humid, moderate and cold) to optimize energy efficiency and payback period. Step-3: Special roof types like Green roofs, cool roofs, Photovoltaic roofs, roof ponds, and the like are simulated and compared for their effectiveness in selected climate types. Based on the literature review, simulation results, and analysis, the recommendations are framed for energy-efficient roofing systems in the selected climate type with respect to heat transfer through the roof and thermal comfort. [ABSTRACT FROM AUTHOR]

The use of free convection in various industries grows, which is due to the increase in heat loads, and also to the closer attention to energy efficiency. Thus, for air-cooled apparatuses at certain parameters of the outside air, there is a possibility to decouple fan drives and to operate the apparatuses in an energy-saving free-convection regime. Here, a distinctive feature of the free-convection regime are high values of heat-transfer coefficients to compensate for which the heat-transfer surface on the source side of the air is increased by finning the tubes. With the aim of raising the efficiency of heat-transfer processes, it is expedient to optimize the geometric parameters and arrangement of a bundle, the number of rows, and the location of the bundle in space. The paper presents a review of experimental and numerical investigations into the heat transfer of multirow horizontal and inclined bundles of finned tubes in a free-convection regime. This paper is a continuation of [1] in which a review has been presented of experimental and numerical investigations into the free-convection heat transfer on air-cooled annular-finned tubes and single-row bundles thereof. Importantly, the character of the dependences of the heat transfer of single-row bundles on the transverse pitch of the tubes differs fundamentally from similar dependences for multirow staggered bundles because of the influence of upper rows. [ABSTRACT FROM AUTHOR]

The humidifier plays a key role in a humidification–dehumidification (HDH) desalination system; it directly affects both the freshwater production efficiency and energy consumption ratio of the system. In this study, for a humidifier in an HDH system, a heat–mass coupled differential equation model of spray water and air on the surface of the packing material was established, and the effects of parameters such as the spray water temperature (tw), mass flow rate of spray water (mw), air temperature (ta), and air mass flow rate (ma) on the humidification performance of humidifiers composed of eight different types of packing materials were investigated. The results show the following: (1) Under the same inlet spray water and air conditions, the humidification performance of different packing materials from good to bad is as follows: cellulose paper, polypropylene, hackettes, saddles, snowflakes, wooden slats, polyvinyl chloride, gunny bag cloth. (2) Increasing the tw can significantly improve the humidification performance. To achieve higher humidification energy efficiency, it is recommended to increase the tw to above 80 °C. (3) With the increase in the mw, although the humidification efficiency (εhum) decreases slightly, the humidification rate (mhum) increases, and the specific humidification energy ratio (ηhum) decreases accordingly. To maintain a high mhum and a low ηhum, it is advisable to control the mw at not less than 0.5 kg/s. (4) Increasing the humidifier inlet ta can improve the mhum, εhum, and ηhum, although not as effectively as increasing tw. (5) Increasing the ma can improve mhum and εhum. However, it simultaneously increases the ηhum. The results of this study can provide theoretical guidance for the selection of efficient packing materials and the optimization of humidifier operating conditions in HDH desalination systems. [ABSTRACT FROM AUTHOR]

In this paper the 2-D steady-state heat transfer geometric inverse problem is solved using the finite element method, conjugate gradient method, and firefly algorithm. Based on the finite element method for solving the forward heat transfer model, and based on continuous iterative optimisation of the conjugate gradient method, the accuracy of the error function of the measured and estimated values is kept within a certain range, so that the geometry of the object under test can be calculated in an inverse way. In the study of the forward problem, the temperature field distribution is solved using circular pipes as the research objects, and the feasibility of applying the finite element method to heat transfer problems is verified. The inverse problem takes the circular tube as the object and considers two different corrosion defects on the inner wall of the circular tube. Simultaneously, the firefly algorithm is introduced based on the conjugate gradient method to stochastically optimize the temperature data and suppress the fluctuation of the inversion result. Numerical experiment results indicate that the method in this paper can perform more accurate geometric shape recognition when there is a certain temperature measurement error or the temperature measurement information is relatively complete. [ABSTRACT FROM AUTHOR]

This Special Issue presents papers related to various aspects of hydrodynamics and heat mass transfer in two-phase gas-liquid and gas-dispersed flows in pipes or ducts. Two-phase gas-liquid and gas-dispersed flows are frequently encountered in energy, nuclear, chemical, geothermal, oil and gas and refrigeration industries. In the experimental and numerical studies of swirling flows in an aerial vortex reactor [[7]], it was found that, similar to the case of two rotating liquids, a strongly swirling jet is formed at the reactor axis and the entire flow takes on the structure of a miniature gas-liquid tornado. All of the abovementioned reviews and research papers have demonstrated the importance and usefulness of two-phase gas-liquid and gas-dispersed flow studies, using both measurements and numerical simulations for science and a range of applications. [Extracted from the article]

In this paper, a new split iterative compact difference scheme for a class of system is constructed. Then, the conservation properties of the scheme are discussed, and the convergence of the split iterative difference scheme is analyzed by using the discrete energy method on the basis of the prior estimation. Finally, numerical experiments verify these properties of the new scheme. In addition, the numerical results also show the influence of fractional derivative on the variation of the transport equation. [ABSTRACT FROM AUTHOR]

Line loss refers to the electrical energy that is dissipated as heat during the transmission and distribution of electricity through power lines. However, unusual causes, such as grid topology mismatch and communication failure, can cause abnormal line loss. Efficient abnormal line loss detection contributes not only to minimizing energy wastage and reducing carbon emissions but also to maintaining the stability and reliability of the entire distribution network. In actual situations, the cause of abnormal line loss is not labeled due to the expensive labor cost. This paper proposes a hierarchical abnormal line loss identification and category classification model, considering the unlabeled and unbalanced sample problem. First, an abnormal line loss identification model-based random forest is established to detect whether the line loss is abnormal. Then, an abnormal line loss category classification model is developed with semi-supervised learning for line loss abnormal category classification, considering the unlabeled samples. The real dataset in China is utilized to validate the performance of the proposed model. Its reliability implies the potential to be applied to real-world scenarios to improve the management level and safety of the power grid. [ABSTRACT FROM AUTHOR]

This document is a special issue of the journal Nonlinear Studies, featuring interdisciplinary perspectives in applied mathematics. It includes articles on consumer behavior, diffusion of innovation, numerical methods, game theory, and optimization, covering domains such as engineering, management, and physics. The papers have undergone peer review and offer original and high-quality research. The document compiles research contributions on reliability analysis, mathematical modeling, differential equations, and optimization problems, with references for further exploration. The authors express gratitude to the contributors and reviewers for their valuable contributions. [Extracted from the article]

The tangential jet-induced swirling flow is a highly efficient technology for enhancing heat transfer. This paper explores the application of swirling flow of an airfoil/aero-engine in a hot air anti-icing chamber, aiming to improve the anti-icing performance and achieve a more uniform temperature on the surface. A series of numerical computations adopting the SST k − ω turbulent model was carried out to obtain the internal flow and heat transfer characteristics, as well as the surface temperature distributions, considering water evaporation and solid heat conduction. Three jet arrangements, including impingement jets, offset jets, and swirl jets, were studied and compared, which evidently showed that the swirling effect was helpful to elevate the internal heat transfer. Compared to the impingement jets at the Reynolds number of 40,000, the Nusselt number with the offset jets is increased by 19.5%, while the corresponding Nusselt number of the swirl jets is augmented by 44.3%. The swirling flow significantly elevates the swirl number within the internal chamber, intensifying the vortex strength near the wall and increasing the circumferential velocity, which also results in an augmentation of internal pressure loss. By adopting the swirling internal flow, the temperature distribution on the anti-icing surface is more uniform and is increased by up to about 4.1 K in the leading edge when the internal-to-external temperature difference is 80 K. Simultaneously, the heat absorption of water evaporation and the matches between the internal heat transfer and external icing load are of particular importance to determine the anti-icing performance, and this has been discussed in this paper. [ABSTRACT FROM AUTHOR]

The heating of a thin metal film subjected to the ultra-short laser pulse is presented. Mathematical description of this process is based on the system of equations describing the electron and lattice temperatures and dependences between intensity of heat fluxes and temperature gradients supplemented by appropriate boundary and initial conditions. In this approach, a system of four equations needs to be solved. In this paper, another method of solution of the above formulated problem is proposed. Using appropriate mathematical manipulations, instead of four equations, two equations describing the lattice and electron temperature distributions are obtained. This system of two equations is solved using an implicit scheme of the finite difference method. The results obtained using both approaches were compared. They were almost identical, which confirms the correctness of the proposed method. [ABSTRACT FROM AUTHOR]

At present, most numerical methods consider the tube walls as the same constant temperature in the simulations of the heat exchanger, and only the external fluid outside the tubes is considered. To investigate the heat transfer performance of the heat exchanger in the real running state, a conjugate heat transfer simulation is performed for a heat exchanger equipped with cross-combined ellipsoidal dimple tubes in this paper. The k-e standard turbulence model is selected to simulate the heating process of tube bank. The distributions of the temperature field and flow field are analyzed carefully. The results indicate that the temperature distribution and the heat flux on the tube wall are uneven, which is different from the case regarding the wall boundaries as a constant temperature. The heat transfer performance of the dimpled tube is higher than that of the smooth tube in the heat exchanger, and the heat transfer performance for aligned arrangement is better than that for staggered arrangement. In addition, the influences of geometric and flowing parameters on heat transfer are discussed. [ABSTRACT FROM AUTHOR]

Gathering and transportation pipelines often appear shutdown condition due to damage, leakage, and other reasons. The reasonable maintenance time should be controlled by closely combined with the change law of the oil-water temperature in the pipeline. This paper established a multi-field coupling 3-D heat transfer mathematical model of the oil-water pipeline environment based on the two-phase shutdown pipeline as the research object. According to the changing law of the oilwater temperature field and flow field under a typical pipe diameter, the evolution behavior of the gelation layer in the pipe and the transformation process of heat transfer mode were analyzed, and the heat transfer characteristics between oilwater phase and its interface in the pipe were defined. With the liquid phase ratio of the oil phase changing the rule, reasonable maintenance time suggestions were given for gathering and transporting pipelines with different water content. [ABSTRACT FROM AUTHOR]

It is a new practical method to apply external magnetic field in magnetic working fluid to enhance heat transfer. In this paper, the swirl flow and heat transfer characteristics of ferrofluid in elliptical tubes under thermal-magnetic-flow fields coupling have been studied by using the finite volume method. The flow structure and secondary vortices evolution process of magnetic nanofluid in elliptical ducts under the action of the magnetic fields have been obtained. The effects of magnetic induction intensity and the ratio of major axis to minor axis of elliptical pipe on the flow and heat transfer performances have been main investigated. The results show that there is obvious secondary flow (with four vortices or eight vortices) on the cross-section and the swirling flow is gradually formed due to the coupling of thermal-magnetic-velocity fields. With the increase of the ratio of major axis to minor axis, the heat transfer enhancement effect with the application of external magnetic field is weakened. The comprehensive performance of flow and heat transfer are better at lower Reynolds number and higher magnetic induction intensity. [ABSTRACT FROM AUTHOR]

The combustion of fuel under intense volumetric forces has the potential to enhance the velocity of flame propagation. To investigate the influence of volumetric forces on the combustion process and the characteristics of flame propagation within fuel, this research paper conducted a numerical analysis of a 2-D rotating pipe subjected to varying volumetric forces. The findings reveal that, within a specific range, an augmentation in volumetric forces progressively elevates both the global and localized speeds of flame propagation. The primary rationale behind the heightened flame propagation speed under intense volumetric forces lies in the fact that the increase in such forces facilitates an enlargement of the interface area between the burned and unburned gases. This, in turn, fortifies the transfer of heat and the chemical reaction rate between the two, effectively shortening the duration of combustion and augmenting the speed of flame propagation. At exceedingly low volumetric forces, the pressure wave generated by combustion in the pipe exerts a certain influence on the speed of flame propagation and the progression of the flame. [ABSTRACT FROM AUTHOR]

The heat kernel associated with a discrete graph Laplacian is the basic solution to the heat diffusion equation of a strict graph or network. In addition, this kernel represents the heat transfer that occurs over time across the network edges. Its computation involves exponentiating the Laplacian eigensystem with respect to time. In this paper, we expand upon this concept by considering a novel network-theoretic approach developed in recent years, which involves defining the k-path Laplacian operator for networks. Prior studies have adopted the notion of integrating long-range interactions (LRI) in the transmission of "information" across the nodes and edges of the network. Various methods have been employed to consider long-range interactions. We explore here the incorporation of long-range interactions in network analysis through the use of Mellin and Laplace transforms applied to the k-path Laplacian matrix. The contribution of this paper is the computation of the heat kernel associated with the k -path Laplacian, called the generalized heat kernel (GHK), and its employment as the basis for extracting stable and useful novel versions of invariants for graph characterization. The results presented in this paper demonstrate that the use of LRI improves the results obtained with classical diffusion methods for networks characterization. [ABSTRACT FROM AUTHOR]

Due to environmental concerns, natural refrigerants and their use in refrigeration and air conditioning systems are receiving more attention from manufacturers, end users and the scientific community. The study of heat transfer and pressure drop is essential for accurate design and more energy efficient cycles using natural refrigerants. The aim of this work is to provide an overview of the latest outcomes related to heat transfer and pressure drop correlations for ammonia, propane, isobutane and propylene and to investigate the current state of the art in terms of operating conditions. Available data on the existing correlations between heat transfer coefficients and pressure drops for natural refrigerants have been collected through a systematic search. Whenever possible, validity intervals are given for each correlation, and the error is quantified. It is the intention of the authors that this paper be a valuable support for researchers and an aid to design, with particular reference to heat pumps. A procedure based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement was adopted, and the Scopus database was used to query the relevant literature. A total of 135 publications qualified for inclusion in the survey; 34 articles report experimental investigations for unusual geometric conditions. Of the 101 selected papers related to usual geometric conditions, N = 50 deal only with HTC, N = 16 deal only with pressure drop and the remainder (N = 35) analyse both HTC and pressure drop. Among the 85 HTC papers, N = 53 deal with the evaporating condition, N = 30 with condensation and only N = 2 with the heat transfer correlations under both conditions. Most of the 101 articles concern propane and isobutane. The high temperatures are less widely investigated. [ABSTRACT FROM AUTHOR]

Plate heat exchangers are realized by means of a heat transfer mechanism, in which heat is naturally transferred from the hot substance to the object with a lower temperature according to the laws of thermodynamics. Two liquids of different temperatures flow on the wall, heat transfer on the wall and convection of the liquid on the wall, thus promoting heat transfer between the two liquids. Under the same flow rate and power consumption conditions, its heat transfer coefficient is three times that of shell and tube heat exchangers, which is a key and efficient new equipment for effectively using effective resources and saving and developing new energy. However the heat supply plate heat exchanger has a tiny circulation surface and is easily obstructed. Regular maintenance and cleaning, troubleshooting, and plate replacement all necessitate frequent heat exchanger disassembly and installation. The requirements and challenges in dismantling and assembling the heat exchanger are very high, and manual disassembly is wasteful, making consistent force difficult to achieve. The current methods of disassembly and assembly are inefficient and incorrect. The intelligent mechanization of disassembly and assembly equipment is realized in this paper by driving, clamping, automatic control, distance measurement, sensing, and other systems. The problems of uneven force, low efficiency, and precision in plate heat exchanger disassembly and assembly are solved. Our power disassembly equipment for high efficiency heat transfer plate heat exchangers not only enhances disassembly efficiency and precision, but it also ensures the safe operation of the plate heat exchanger heating system, and the heat transfer efficiency and heat exchange efficiency are improved. Furthermore, it has a wide range of applications in the petroleum, chemical, and other industries. [ABSTRACT FROM AUTHOR]

An efficient and accurate method for optimizing capsule-type plate heat exchangers is proposed in this paper. This method combines computational fluid dynamics simulation, a backpropagation algorithm and multi-objective optimization to obtain better heat transfer performance of heat exchanger structures. For plate heat exchangers, the heat transfer coefficient j and friction coefficient f are a pair of contradictory objectives. The optimization of capsule-type plate heat exchangers is a multi-objective optimization problem. In this paper, a backpropagation neural network was used to construct an approximate model. The plate shape was optimized by a multi-objective genetic algorithm. The optimized capsule-type plate heat exchanger has lower flow resistance and higher heat exchange efficiency. After optimization, the heat transfer coefficient is increased by 8.3% and the friction coefficient is decreased by 14.3%, and the heat transfer effect is obviously improved. Further, analysis of flow field characteristics through field co-ordination theory provides guidance for the further optimization of plates. [ABSTRACT FROM AUTHOR]

Underground Thermal Energy Storage (UTES) store unstable and non-continuous energy underground, releasing stable heat energy on demand. This effectively improve energy utilization and optimize energy allocation. As UTES technology advances, accommodating greater depth, higher temperature and multi-energy complementarity, new research challenges emerge. This paper comprehensively provides a systematic summary of the current research status of UTES. It categorized different types of UTES systems, analyzes the applicability of key technologies of UTES, and evaluate their economic and environmental benefits. Moreover, this paper identifies existing issues with UTES, such as injection blockage, wellbore scaling and corrosion, seepage and heat transfer in cracks, etc. It suggests deepening the research on blockage formation mechanism and plugging prevention technology, improving the study of anticorrosive materials and water treatment technology, and enhancing the investigation of reservoir fracture network characterization technology and seepage heat transfer. These recommendations serve as valuable references for promoting the high-quality development of UTES. [ABSTRACT FROM AUTHOR]

This paper presents the results of numerical simulations of heat transfer in a tube with a protective chromium layer on the inner surface made of steel, with different shrinkage temperatures. Shrinkage in the steel is an unfavorable phenomenon because it causes cracks in the chrome coating. The cracks contribute to the peeling of the protective material on the inner surface of the tube. Wear and damage to the chrome layer significantly shortens the tube's service life. The influence of the type of steel with medium carbon content on heat transfer for a sequence of ten, thirty, and sixty heat impulses was examined. Simulations were carried out for two selected steels with clearly different shrinkage temperatures, i.e., 30HN2MFA and X37CrMoV5-1 (1.2343). In 30HN2MFA steel, the shrinkage effect occurred at a temperature of approx. 750 °C, while in X37CrMoV5-1 steel it occurred at a temperature of approx. 870 °C. In the computational model, 30 cross-sections of the three-meter-long tube were analyzed. A time-dependent heat transfer coefficient was calculated in each zone. Heat transfer simulations were carried out using COMSOL version 6.1 software. This paper shows that for X37CrMoV5-1 steel, the shrinkage temperature on the inner surface of the tube was reached after approx. 60 heat impulses, while for 30HN2MFA steel, it was reached after approx. 30. The greatest differences in the number of impulses occurred for a pipe with a 200 µm thick chrome layer. [ABSTRACT FROM AUTHOR]

This paper presents a simulation model for a system equipped with thermoelectric elements, considering the impact of independent thermal contact resistances on each side of the module. An analytical model was constructed, taking into account the asymmetry of thermal resistances between the generator/cooler and the respective heat source/heat sink. A comparative analysis of thermoelectric device operating indicators such as conducted heat, efficiency, and the electricity/cooling power produced was performed. The selection of electrical current in the circuit was analysed based on the maximization of power or efficiency. This paper discusses deviations from ideal conditions, specifically the absence of thermal resistance between the heat source/sink and the thermoelectric junction. The model accurately simulates the operating conditions of the thermoelectric system with a low computational cost. The results indicate that the total thermal resistance, rather than its location, predominantly affects the operation of the thermoelectric generator. However, in cooling operations, the influence of thermal resistance significantly depends on the cooling power demand and temperature. [ABSTRACT FROM AUTHOR]

This paper presents the results of an analysis of heat transfer in a cross-flow mini heat exchanger (CFMHE). The purpose of the paper was to analyze the results of the experimental measurements presented in the previous work in order to determine dimensionless correlations that allow for the calculation of heat transfer coefficients for the CFMHE. Analyzed CFMHE consisted of a brass cylindrical core, in which 2 mm circular holes were drilled. A method based on an optimization procedure was used to determine the correlations describing the heat transfer coefficients, allowing the correlations to be determined without the need of measuring the mini channel wall temperature. Overall heat transfer coefficients calculated using the proposed correlations typically did not deviate by more than ±10% from the corresponding experimental results, which was a significant improvement in the quality of the fit compared to the results presented in previous work. [ABSTRACT FROM AUTHOR]

Radiant floor heating systems have become a reference technology, but their use for cooling purposes has proven inconvenient in many applications due to their reduced cooling capacity and condensation issues. Nonetheless, potentialities and drawbacks of radiant floor cooling systems have been frequently addressed and simulated, given the large potential advantages of employing a single emissive system for all seasons. This paper aims to provide a comprehensive review of the modeling methods for radiant floor cooling systems proposed in scientific papers and also used in simulation software and technical standards. Models are classified according to their characterizing features, and the distinctive contributions of each method are discussed. Additionally, the modeling of the most relevant phenomena affecting floor performance is further discussed. The review revealed the presence of two main modeling classes, one only focusing on the floor's conductive heat transfer and the other integrating active floor analysis within the building's energy model of the thermal zone. Despite the presence of many modeling methods that are able to consider the most important effects in the radiant cooling system operation, not all the phenomena present in a practical application are fully described. Therefore, there is an ongoing need for more comprehensive, possibly easily characterizable, modeling approaches. [ABSTRACT FROM AUTHOR]

In order to study the influence of the louver angle on the heat transfer and flow resistance characteristics of a parallel flow heat exchanger, this paper establishes five calculation models including a uniform angle model and four variable angle models for comparing and analyzing the temperature, velocity, and pressure fields, and evaluates their comprehensive performance. The results show that the suitable choice of the v louver angle can lead to an optimal heat transfer effect and a best comprehensive performance. [ABSTRACT FROM AUTHOR]

This paper studies a self-designed high temperature fireball quasi-static simulation device to understand the temperature distribution of each substance inside the fireball under the multi-pipe injection technology. The changes in the physical field of the high temperature fireball are obtained through numerical simulation. The simulation model in this paper adopts the turbulent k-ε model, and simulates the material transfer process according to Fick's law. The commercial software COMSOL multiphysics is used to give and analyze the local characteristics of fluid-flow and heat transfer. The simulation device formed a high temperature fireball under the interaction of the three-way jet fire. The experimental data verified the accuracy of the simulation results, and the experimental results were in good agreement with the simulation results. This method of analyzing the actual temperature field through simulation can be used to provide a powerful verification scheme for the detection of complex multi-temperature fields in the future. [ABSTRACT FROM AUTHOR]

To eliminate the negative effect of traditional metal-working fluids and achieve sustainable manufacturing, the usage of nano-enhanced biolubricant (NEBL) is widely researched in minimum quantify lubrication (MQL) machining. It's improved tool wear and surface integrity have been preliminarily verified by experimental studies. The previous review papers also concluded the major influencing factors of processability including nano-enhancer and lubricant types, NEBL concentration, micro droplet size, and so on. Nevertheless, the complex action of NEBL, from preparation, atomization, infiltration to heat transfer and anti-friction, is indistinct which limits preparation of process specifications and popularity in factories. Especially in the complex machining process, in-depth understanding is difficult and meaningful. To fill this gap, this paper concentrates on the comprehensive quantitative assessment of processability based on tribological, thermal, and machined surface quality aspects for NEBL application in turning, milling, and grinding. Then it attempts to answer mechanisms systematically considering multi-factor influence of molecular structure, physicochemical properties, concentration, and dispersion. Firstly, this paper reveals advanced lubrication and heat transfer mechanisms of NEBL by quantitative comparison with biolubricant-based MQL machining. Secondly, the distinctive filmformation, atomization, and infiltration mechanisms of NEBL, as distinguished from metal-working fluid, are clarified combining with its unique molecular structure and physical properties. Furtherly, the process optimization strategy is concluded based on the synergistic relationship analysis among process variables, physicochemical properties, machining mechanisms, and performance of NEBL. Finally, the future development directions are put forward aiming at current performance limitations of NEBL, which requires improvement on preparation and jet methods respects. This paper will help scientists deeply understand effective mechanism, formulate process specifications, and find future development trend of this technology. [ABSTRACT FROM AUTHOR]

The paper contains a response to the comment by Popovich and Mincheva, focusing on the different meanings of the analysis according to the First and the Second law of thermodynamics and their complementary and never alternative nature. [ABSTRACT FROM AUTHOR]

In recent years, more and more attention has been paid to research on variable geometry turbine engines with the increasing requirement of engine performance. Variable geometry turbine technology can significantly improve the operating performance of aero engines. Adjusting the working angle of the turbine guide vane can change the thermodynamic cycle of the engine operation, so that the turbine can respond to different engine operating conditions. Variable geometry turbines work in harsh environments. Therefore, the design of the variable geometry turbine needs to consider the effect of thermal deformations of the mechanism on operational stability. There are few research studies on variable geometry turbine adjusting mechanisms. This paper established the numerical calculation models of two adjusting mechanisms by integrating fluid mechanics, heat transfer, and dynamic theories, which are paddle and push–pull rod mechanisms. The models were applied to study the effects of components' thermal deformations and flexible bodies on the motion characteristics of the adjusting mechanism. Furthermore, the performance of the two adjusting mechanisms was compared. The calculation results show that the paddle rod adjusting mechanism can accurately adjust the angles of guide vanes. The paddle rod adjusting mechanism has a larger driving stroke and smaller driving force than the push–pull rod adjusting mechanism. The paddle adjustment mechanism was better suited to the operational requirements of the variable geometry turbine. The research results of this paper are relevant to the design of variable geometry turbine regulation structures. [ABSTRACT FROM AUTHOR]

The thermal comfort and air-conditioning energy consumption of vehicles or trains are dependent on the thermal resistance of its envelopes, which could be enhanced by improving the radiation characteristics of the narrow cavities scattered in their envelopes. However, the study for a feasible method and its effectiveness has been given little attention. This paper introduces a method that involves pasting aluminum foil on the inner wall to change the radiation characteristics of the narrow cavity and analyzed its effects on narrow-cavity heat transfer by experimental and numerical methods. The results indicate that the radiation effect on heat transfer in a narrow cavity made of conventional material is dominant, with a rate larger than 75%, and that pasting aluminum foil is an effective and feasible method of weakening the radiation rate in narrow-cavity heat transfer, decreasing it to less than 10%. This paper will provide a reference to improve the insulation characteristics of vehicle enclosure. [ABSTRACT FROM AUTHOR]

Many polymers are processed and compounded in co‐rotating, fully intermeshing twin screw (TS) extruders. The typical compounding process consists of multiple unit operations including feed introduction, conveying solids away from the feed zone, transitioning from the conveying zone to the kneading block (KB) melting zone, melting, a downstream feed zone, a downstream mixing zone, a devolatilization region, and a pressure generating discharge section. This paper will focus on the first of these unit operations, the conveying of pellets in a partially filled screw leading to compaction and pressure generation in the full screw channel prior to the KB melting zone. Mechanisms for pellet conveying, for heating the polymer pellets, and for developing pressure at the end of the solids conveying screw elements are first presented for low‐density polyethylene (LDPE). The predictions of the model are also compared with a classical set of experiments on high‐density polyethylene (HDPE). The model is then tested using published characteristics of a polyamide‐type polymer. This paper focuses on the physics and engineering concepts that are inherent in the feed section of the TS extruder where the pressure is calculated using the friction of the polymer pellets. The effects of throughput, Q, at a constant rotation speed, N, are examined. Low and high Q/N ratios have significantly different axial pressure profiles. [ABSTRACT FROM AUTHOR]

Droplet positive collision is a complex process involving heat transfer in gas-liquid-solid three-phase flow and droplet collide dynamics. In order to study the kinetic behavior of droplets under positive collision in low velocity (v < 2 m/s), this paper focuses on the spreading, vibration, and fracture characteristics of double droplets by numerical simulation. First, the accuracy of the model is verified by experimental comparison. The effects of droplet diameters, collision velocities and wall contact angles on the spreading process are analyzed, and the spreading factor curves are plotted. Then, the droplet rebound vibration after collision fusion is equated to a single-degree-of-freedom damped vibration system, and the peak vibration height variation curve of the fused droplet is obtained by non-linear fitting. Considering the droplet phase change, the influence law of different conditions on the vibration damping factor and vibration time of the fused droplet is studied. Finally, it is found that rebound fracture and spreading fracture occur after the fusion of double droplets under positive collision, and the critical values of collide velocity required for the occurrence of the aforementioned phenomenon are found. To provide a reliable theoretical basis for the study of heat and mass transfer processes after multiple droplets collide the wall. [ABSTRACT FROM AUTHOR]