Optimal Transfer Research Articles

Thermodynamic optimization of heat exchanger circuitry via genetic programming

In this study, an evolutionary thermodynamic technique was developed for the optimization of heat exchanger circuitry. The proposed technique is capable of handling the unrestrained implementation of genetic operators while ensuring circuitry feasibility and basic manufacturability. The optimization tool was used to clarify the optimal heat transfer features in relation to the characteristics of the refrigerant and to provide a thermodynamic interpretation of the optimization results to extract general design guidelines. Evaporator circuitry optimization was conducted under given cooling capacity, superheating degree, and boundary conditions representative of air-conditioning applications. The consistency between the minimum entropy generation and the maximum coefficient of performance (COP) was demonstrated under these settings. Accordingly, heat exchanger configurations that take maximum advantage of the thermodynamic benefits of each refrigerant are proposed by optimizing the distribution of friction and heat transfer irreversibility. Consequently, the evaporator outlet pressure increases, thus lowering the compression ratio and maximizing the COP. The developed optimization method maximizes the benefits of low-GWP alternative refrigerants and shows that zeotropic mixtures may exhibit performance analogous to that of R32 and higher than that of R410A by approaching a Lorenz cycle operation.

Operation strategy optimization and heat transfer characteristic analysis of photovoltaic/thermal module series connected with flat plate solar collector: System experimental study

Flat plate solar collector (FPSC) produces only thermal energy without electricity, whereas the photovoltaic thermal (PV/T) module produces electricity and low-temperature thermal energy. This paper presents a low-cost method to strengthen the functional uniqueness of individual PV/T and FPSC components through connecting a PV/T module in series with the other component. Under various water volume conditions, an experimental test on high mass flow rate was carried out. Results showed that the FPSC produced a better heating contribution and that reverse heat transfer of the PV/T module might be reduced by changing the operation strategy. The water volume is a crucial factor that influences the system's available heating time, a system that operates in the optimal water volume range will produce greater energy savings. Furthermore, the maximum values of the thermal, electrical, exergy, and primary energy-saving efficiency were 51.91 %, 13.52 %, 19.13 %, and 87.20 %, respectively. The optimal water volume distribution range of the system is 160–180 L. With an average annual decrease of 2.96 t in CO2 emissions, the system provides a 4.28-year payback period and saves 5285.71 USD in electricity costs throughout its life cycle. The novel system performs extremely well in terms of energy and cost efficiency.

Regulation Mechanism and Optimization Strategy of Microbial Metabolism in Bioreactor

In this study, the metabolic regulation mechanism of microorganisms in bioreactor was discussed, and a series of optimization strategies were proposed based on this. The key effects of metabolic regulation on the performance of bioreactors were revealed through the overview of microbial metabolic pathways and the analysis of regulatory mechanisms. In view of this, the optimization strategy based on metabolic regulation was proposed from the aspects of metabolic engineering transformation, genetic engineering technology application, metabolic pathway reconstruction and optimization. At the same time, the operating conditions of the reactor, such as temperature, pH value, dissolved oxygen, substrate concentration and mixing effect were optimized in detail. In terms of reactor design and scale-up strategy, the scale effect, reactor configuration and flow field optimization, and heat and mass transfer enhancement technology were mainly considered. This study provides important theoretical and practical guidance for the improvement of bioreactor performance and the progress of biotechnology industry.

The impact of knowledge characteristics on process performance: experimenting with the conversion perspective on knowledge transfer velocity

PurposeWith shorter product cycles and a growing number of knowledge-intensive business processes, time consumption is a highly relevant target factor in measuring the performance of contemporary business processes. This research aims to extend prior research on the effects of knowledge transfer velocity at the individual level by considering the effect of complexity, stickiness, competencies, and further demographic factors on knowledge-intensive business processes at the conversion-specific levels.Design/methodology/approachWe empirically assess the impact of situation-dependent knowledge transfer velocities on time consumption in teams and individuals. Further, we issue the demographic effect on this relationship. We study a sample of 178 experiments of project teams and individuals applying ordinary least squares (OLS) for regression analysis-based modeling.FindingsThe authors find that time consumed at knowledge transfers is negatively associated with the complexity of tasks. Moreover, competence among team members has a complementary effect on this relationship and stickiness retards knowledge transfers. Thus, while demographic factors urgently need to be considered for effective and speedy knowledge transfers, these influencing factors should be addressed on a conversion-specific basis so that some tasks are realized in teams best while others are not. Guidelines and interventions are derived to identify best task realization variants, so that process performance is improved by a new kind of process improvement method.Research limitations/implicationsThis study establishes empirically the importance of conversion-specific influence factors and demographic factors as drivers of high knowledge transfer velocities in teams and among individuals. The contribution connects the field of knowledge management to important streams in the wider business literature: process improvement, management of knowledge resources, design of information systems, etc. Whereas the model is highly bound to the experiment tasks, it has high explanatory power and high generalizability to other contexts.Practical implicationsTeam managers should take care to allow the optimal knowledge transfer situation within the team. This is particularly important when knowledge sharing is central, e.g. in product development and consulting processes. If this is not possible, interventions should be applied to the individual knowledge transfer situation to improve knowledge transfers among team members.Social implicationsFaster and more effective knowledge transfers improve the performance of both commercial and non-commercial organizations. As nowadays, the individual is faced with time pressure to finalize tasks, the deliberated increase of knowledge transfer velocity is a core capability to realize this goal. Quantitative knowledge transfer models result in more reliable predictions about the duration of knowledge transfers. These allow the target-oriented modification of knowledge transfer situations so that processes speed up, private firms are more competitive and public services are faster to citizens.Originality/valueTime consumption is an increasingly relevant factor in contemporary business but so far not been explored in experiments at all. This study extends current knowledge by considering quantitative effects on knowledge velocity and improved knowledge transfers.

Optimizing the photocatalytic properties of macroporous geopolymer foam: Influence of SILAR-technique synthesis conditions

Macroporous cross-linked materials such as 3D honeycomb foams are used as substrates for heterogeneous photocatalysis. They offer a number of interesting properties. They are highly open-porosity substrates, guaranteeing optimum mass and radiation transfer, making them ideal for photo-conversion applications such as photo-oxidation or photo-reduction, which take place in photo-reactors for pollutant degradation or solar fuel production. Many cross-linked supports such as polymeric and metallic foams studied in the literature have revealed photocatalytic capacities similar to those obtained for the catalyst nanoparticle suspensions used as a reference. To reduce the production costs of this type of material, geopolymers, widely used in civil engineering, offer a wide range of properties suitable for shaping cellular foams. In addition to their low cost and mechanical properties, it is also possible to impart porous properties and modulate their characteristics according to the synthesis operating conditions so as to elaborate macroporous cellular foams. In this study, we propose to investigate the photocatalytic properties of honeycomb geopolymer foams coated with a catalyst: ZnO. To achieve ZnO deposition, the SILAR technique was applied by modifying the key synthesis operating conditions, i.e. precursor concentration and the number of quenching cycles applied. The results obtained make it possible to define the optimum operating conditions (pH, temperature) and, above all, the number of cycles and precursor concentration required to obtain the best photocatalytic efficiency. These innovative and promising materials, little studied in the literature, are prime candidates for solar photo-conversion applications.

Optimal Income Taxation

This article explores subjects in optimal income taxation characterized by recent research interest, practical importance in light of concerns about inequality, potential for misunderstanding, and prospects for advancement. Throughout the analysis, paths for further investigation are highlighted. Areas of focus include multidimensional abilities and endogenous wages; asymmetric information and the income of founders; production and consumption externalities from labor effort; market power and rents; behavioral phenomena relating to perceptions of the income tax schedule, myopic labor supply, and the interactions of savings, savings policies, and labor supply; optimal income transfers; the relationship between optimal income taxation and the use of other instruments; and issues relating to the social welfare function and utility functions, including non-welfarist objectives, welfare weights, heterogeneous preferences, and taxation of the family. (JEL D63, D82, D91, H21, H24, H53, J22)

Immobilization of zirconium-modified activated carbon in an alginate matrix for the removal of atrazine: Preparation, performances and mechanisms

As an organic herbicide widely used in agriculture, atrazine has the characteristics of environmental persistence, high mobility and long half-life period, posing potential risks to the ecological environment. The materials commonly used to remove atrazine are powdered activated carbon and its modified materials, which have problems such as difficulty in recycling and secondary contamination. In order to solve the above problems, in this study, a new functional material EI-Zr@AC was prepared by immobilizing zirconium-modified activated carbon powder (Zr@AC) in an alginate matrix via the embedding immobilization (EI) technique, and was employed for removing atrazine in water. At the optimal preparation conditions of 2.5 % sodium alginate, 4.0 % CaCl2, 1.0 % Zr@AC and 2.0 % bentonite, the prepared EI-Zr@AC beads had the characteristics of high porosity, dense reticulation, and a large number of functional groups with optimal mechanical strength and mass transfer properties. When solution pH 3.0, temperature 25°C, and EI-Zr@AC dosage of 16 g/L, the removal efficiency of atrazine by EI-Zr@AC was 91.9 %. It showed that the atrazine removal by EI-Zr@AC was mainly the chemisorption and multimolecular layer adsorption. In addition, the EI-Zr@AC could be recycled after simple recycling method, and the removal of atrazine at 5.0 mg/L by the beads was still 55.5 % after five cycles, and the structure of the beads remained intact and Zr ion leaching rate was very low. The results showed that EI-Zr@AC was a kind of environmental remediation material with high application value.

Heat transfer performance and optimal design of shallow coaxial ground heat exchangers

The heat transfer performance of coaxial ground heat exchangers (GHEs) can be strongly influenced by their structure parameters and improved by the optimal design. To improve the heat transfer efficiency, this study proposed a coaxial GHE with large pipe diameters and thick inner pipe insulation for shallow ground source heat pump systems, which had heat transfer rates of more than 120 W/m in 12 h during both heat injection and extraction experiments. The validated three-dimensional CFD model was used to numerically investigate the influence of various structural parameters on the heat transfer efficiency considering the thermal short-circuiting effect. The thermal short-circuiting effect could be alleviated with thicker inner pipe insulation, while the decreasing annular space occupied by the insulation would reduce the borehole heat transfer rates, thus, an inner pipe with a 35 mm-thick insulation obtained the optimal heat transfer rate. The inner pipe diameter increase contributed to a more severe thermal short-circuiting and poor heat transfer performance. Increasing the outer pipe diameter improved the heat transfer efficiency and an optimal outer pipe diameter of 155 mm existed when considering the heat transfer performance and its efficiency. Therefore, increasing the inner pipe insulation thickness and outer pipe diameters can be regarded as an efficient method to improve the thermal performance of coaxial GHEs.

Numerical Investigation of Heat Transfer Characteristics of Trapezoidal Fin Phase Change Thermal Energy Storage Unit

Abstract: In order to enhance the heat transfer performance of a phase change thermal energy storage unit, the effects of trapezoidal fins of different sizes and arrangement modes were studied by numerical simulation in the heat storage and release processes. The optimal enhancement solution was obtained by comparing the temperature distribution, instantaneous liquid-phase ratio, solid–liquid phase diagram and comprehensive heat storage and release performance of the thermal energy storage unit under different fin sizes. During the heat storage process, the results show that when the ratio of the length of the upper and lower base of the trapezoid h1/h2 is 1:9, the heat storage time is shortened by 9.03% and 18.21% compared with h1/h2 = 3:7 and 5:5, respectively. During the heat release process, the optimal heat transfer effect is achieved when h1/h2 = 5:5. To further improve the heat transfer effects, the energy storage unit is placed upside down; then, the least time is achieved when h1/h2 = 2:8. When heat storage and release are considered together, the energy storage unit with h1/h2 = 2:8 takes the shortest time to melt in upright placement and then to solidify in upside-down placement.

A stacking machine‐learning based method for accelerating magnetic coupler design with ferrite cores in inductive power transfer applications

AbstractThis paper presents a magnetic coupler design method for WPT systems based on stacking machine‐learning algorithms. A synthetic dataset generated by ANSYS Maxwell is used for training and evaluating machine‐learning models. Stacking technology effectively combines the results from multiple models and make best predictions. The designed model allows us to obtain the optimal values of the coil inner radius and number of turns , when other coil design parameters such as the coil outer radius , the wire diameter , and the coil inductance , are given based on the application environment. The proposed method provides practical solutions meeting design requirements quickly, easily accommodating magnetic couplers with ferrite cores, and showing advantages in designing magnetic couplers with optimal power transfer efficiency.

Raising America’s future: Search for optimal child-related transfers

The US differs from other OECD countries in terms of family policy size and composition. This study examines the welfare and macroeconomic effects of family policy reforms. I explore three policy instruments: child-related tax credits, childcare subsidies, and child allowances. The children are merit good due to pay-as-you-go social security structure. I show that expanding family policy, like the American Rescue Plan, improves welfare. I also define the optimal family policy for the United States. It accounts for about 3% of GDP, three times larger than the existing policy, and primarily focused on childcare subsidies. Family policy structure is critical for welfare evaluation because similar expenditure levels can result in contrasting welfare outcomes depending on policy composition. This study emphasizes the importance of carefully designed family policies, as well as the need for ongoing research and policy innovation to maximize societal benefits and promote equitable economic growth.

Heat transfer enhancement of a Stirling engine heating tube with three-pronged slant rods under oscillatory flow

Heaters are crucial components in Stirling engines, where the working medium adsorbed heat from an external heat source. Enhancing heat transfer within the heater is essential for boosting the operational efficiency of the Stirling engine. In this study, a tube equipped with three-pronged slant rods was employed to improve the heat transfer within the heater under conditions of oscillatory flow. Three pairs of dynamic longitudinal vortices were generated and exhibited regular movement patterns with distinct phase angles. In comparison to the smooth tube configuration, the enhanced tube outlet exhibited a notable increase in the average working-medium temperature by 62 K and 46 K during the entry and return stages, respectively. The degree of heat transfer enhancement was found to be contingent upon the pitch, height, and inclination angle of the slant rod. Optimal heat transfer enhancement was achieved with slant rods featuring a pitch of 26 mm, a height of 3.5 mm, and an inclination angle of 45°. The performance evaluation criterion ranged from 1.29 to 1.81 of enhanced tube compared to smooth tube. These findings underscore the effective enhancement of heat transfer facilitated by the three-pronged slant rods within the Stirling engine's heater.

Effect of care transfer model led by the hospital clinical pharmacist on reduction of hospital readmissions in the elderly.

Transfer of care is a critical point for patient safety and requires an optimal care transfer model in order to ensure safe pharmacotherapy transfer. Polypharmacy among elderly is associated with adverse health consequences such as hospital readmissions. Hospital readmissions represent priorities in health care research and are one of the measures for assessing patient safety. Medication-related problems among elderly are associated with polypharmacy. The aim of the study was to show the impact of a developed model of care transfer led by a hospital clinical pharmacist on the number of hospital readmissions in the 12-months period in the elderly. A randomized controlled study of patients aged 65 or more was conducted at Dubrava University Hospital, Community Health Centre Zagreb - East and community pharmacies in the City of Zagreb and Zagreb County, Croatia. An intervention group received specially designed care transfer led by the hospital clinical pharmacist. Model included high-intensity pharmacotherapy interventions delivered at admission, during hospital stay and discharge, transition to primary care and post-discharge and cooperation between all healthcare professionals. In all, 182 patients in the intervention and 171 in the control group were analysed. The total number of hospital readmissions and emergency readmissions, within one year from the hospital discharge, was lower in the intervention group than in the control group (41.7% vs. 58.3%, p=0.005; 40.8% vs. 59.2%, p=0.008). The model of the health care transfer applied in this research thus significantly reduced hospital readmissions in the 1-year period in elderly patients. Therefore, the hospital clinical pharmacists should design and coordinate the transfer between hospital and primary care.

Experimental investigation of the heat transfer characteristics, operating limits, and temperature distribution of a prototypically 3 m long two-phase closed thermosyphon for spent fuel pool passive cooling

The current study investigated the heat transfer performance, operation limits, and temperature distribution of a 3 m prototype model for a large-scale straight two-phase closed thermosyphon with deionized water designed for passive cooling of nuclear spent fuel pools with a filling ratio ranging from 20% to 100% and a heat source temperature ranging from 45 to 80 °C. After the accident at the Fukushima Daiichi nuclear power plant, the need for a reliable cooling system for these pools increased, with thermosyphons emerging as a promising solution for passive cooling. The experimental procedure implemented in this study yielded a comprehensive understanding of the operation and phenomena inside a thermosyphon, providing crucial data for the validation and enhancement of numerical models that simulate relevant phenomena within nuclear power plants, including passive residual heat removal with thermosyphons. The results indicated that the optimal heat transfer performance was achieved at a filling ratio of 30%, where the thermosyphon begins operation at a heat source temperature of 45 °C. Additionally, the temperature distribution along the thermosyphon confirmed the operation limits, including partial dryout at a 20% filling ratio and geyser boiling and flooding (entrainment) limits at 75% and 100% filling ratios, respectively.

Optimal orbit transfer of single-tether E-sail with inertially fixed spin axis

This study analyzes the optimal transfer trajectory of a spacecraft propelled by a spin-stabilized electric solar wind sail (E-sail) with a single conducting tether and a spin axis with a fixed direction in an inertial (heliocentric) reference frame. The approach proposed in this study is useful for rapidly analyzing the optimal transfer trajectories of the current generation of small spacecraft designed to obtain in-situ evidence of the E-sail propulsion concept. In this context, starting with the recently proposed thrust model for a single-tether E-sail, this study discusses the optimal control law and performance in a typical two-dimensional interplanetary transfer by considering the (binary) state of the onboard electron emitter as the single control parameter. The resulting spacecraft heliocentric trajectory is a succession of Keplerian arcs alternated with propelled arcs, that is, the phases in which the electron emitter is switched on. In particular, numerical simulations demonstrated that a single-tether E-sail with an inertially fixed spin axis can perform a classical mission scenario as a circle-to-circle two-dimensional transfer by suitably varying a single control parameter.

Introducing a Novel Concept for an Integrated Demolition Waste Recycling Center and the Establishment of a Stakeholder Network: A Case Study from Germany

Using recycled aggregates has many positive environmental impacts because of the conservation of natural resources and minimization of waste. The use of recycled aggregates in downcycling processes is already common in Germany, whereas utilizing them to produce high-quality recycled concrete is rarely applied in practice. The reasons behind this lag have been investigated based on surveys and interviews with stakeholders. Miscommunication and missing information were identified in all stakeholder groups. Therefore, establishing a robust network and facilitating knowledge transfer by specifying the demand for recycled aggregates in the case study region have been considered as prerequisites. Therefore, the paper presents a novel concept of a stakeholder network for an integrated construction and demolition waste center. The conceptualization integrates the recycling companies and construction product manufacturers in one venue with research, service, and educational divisions. The design of the facilities is based on calculations regarding future construction activities and the demand for concrete production. The proposed concept aims to supply the region in the west of Germany with high-quality recycled products while also establishing a robust network that offers benefits in terms of logistical optimization and knowledge transfer.

Investigation of swirler effect on combustion and exergy efficiency of hydrogen/chlorine combustor based on entropy generation analysis

Inefficient reagent reaction limits the development of compact combustion-based HCl synthesis production. To address this issue, a non-premixed HCl synthesis combustor that combines a swirler at the hydrogen channel with a porous nozzle at the chlorine channel is proposed. A three-dimensional non-premixed combustion model is used to investigate the effects of this combustor structure on the combustion efficiency, exergy efficiency, and pressure loss coefficient. The entropy generation analysis is employed to evaluate multiple irreversible losses for different structures and flow states. Through experimental validation and numerical simulation analysis, the effects of the swirler installation, inlet flow rate, and H2/Cl2 equivalence ratio on the combustion and heat transfer characteristics are investigated. The results demonstrate that the combustor with the swirler and porous nozzle improves exergy efficiency, leading to higher HCl purity and a reduced flame height for faster reactions under low-flow states. Chemical reactions contribute to over 96 % of entropy generation during combustion, with the swirler reducing total entropy by approximately 5 %. Optimal heat transfer effects and minimized entropy generation are achieved when the swirler is installed below the combustor spray hole. The installation of the swirler can increase the exergy efficiency of the H2/Cl2 combustor to approximately 43.73 %.

Universal Murray’s law for optimised fluid transport in synthetic structures

Materials following Murray’s law are of significant interest due to their unique porous structure and optimal mass transfer ability. However, it is challenging to construct such biomimetic hierarchical channels with perfectly cylindrical pores in synthetic systems following the existing theory. Achieving superior mass transport capacity revealed by Murray’s law in nanostructured materials has thus far remained out of reach. We propose a Universal Murray’s law applicable to a wide range of hierarchical structures, shapes and generalised transfer processes. We experimentally demonstrate optimal flow of various fluids in hierarchically planar and tubular graphene aerogel structures to validate the proposed law. By adjusting the macroscopic pores in such aerogel-based gas sensors, we also show a significantly improved sensor response dynamics. In this work, we provide a solid framework for designing synthetic Murray materials with arbitrarily shaped channels for superior mass transfer capabilities, with future implications in catalysis, sensing and energy applications.

Impact of distance on heat transfer at the leading edge of blades in a rotating state

To enhance the high-temperature capability of turbine blades and meet the requirements of advanced design, this research examines the intricate flow characteristics and the heat transfer occurring on the internal walls effects of leading-edge impingement cooling structures under different impingement distances. In this study, copper block method is employed for heat transfer testing, extending the testing range of rotating impingement cooling channels from Redj = 1 × 104, Ro = 0.2 to Redj = 5 × 104, Ro = 2.0. The findings reveal that the Nusselt number along the channel is significantly influenced by flow distribution and turbulence intensity. At lower Re (Re ≤ 2 × 104), the flow velocity increases along the channel due to the decrease in pressure drop, resulting in enhanced heat transfer. However, at higher Re (Re ＞ 2 × 104), increased flow rate leads to intensified turbulence and thickening of the boundary layer, consuming fluid energy and reducing the temperature difference, thereby adversely affecting heat exchange around the impingement holes. Moreover, Nu decreases with increasing rotation speed, with the highest average decrease of 15.3 % when Ro reaches 0.25. For cases where Redj ＜ 4.3 × 104, an impingement distance-to-diameter ratio (Z/D) = 2 exhibits optimal heat transfer performance. Conversely, when Redj＞4.3 × 104, the influence of impingement distance will diminish. Larger impingement distances increase the HTC but are accompanied by increased non-uniformity. Therefore, selecting an appropriate impingement distance can reduce boundary layer formation and flow separation, thereby forming an optimal flow structure, which contributes to promoting heat exchange and improving heat transfer uniformity. A correlation based on geometrical parameters has been proposed to predict the average Nusselt number for jet impingement arrays with varying geometrical configurations.

Fabricating a Structured Single‐Atom Catalyst via High‐Resolution Photopolymerization 3D Printing

AbstractThis study introduces a novel solution to the design of structured catalysts, integrating single‐piece 3D printing with single‐atom catalysis. Structured catalysts are widely employed in industrial processes, as they provide optimal mass and heat transfer, leading to a more efficient use of catalytic materials. They are conventionally prepared using ceramic or metallic bodies, which are then washcoated and impregnated with catalytically active layers. However, this approach may lead to adhesion issues of the latter. By employing photopolymerization printing, a stable and active single‐atom catalyst is directly shaped into a stand‐alone, single‐piece structured material. The battery of characterization methods employed in the present study confirms the uniform distribution of catalytically active species and the structural integrity of the material. Computational fluid dynamics simulations are applied to demonstrate enhanced momentum transfer and light distribution within the structured body. The materials are finally evaluated in the continuous‐flow photocatalytic oxidation of benzyl alcohol to benzaldehyde, a relevant reaction to prepare biomass‐derived building blocks. The innovative approach reported herein to manufacture a structured single‐atom catalyst circumvents the complexities of traditional synthetic methods, offering scalability and efficiency improvements, and highlights the transformative role of 3D printing in catalysis engineering to revolutionize catalysts’ design.