Exchange Efficiency Research Articles

Numerical Analysis of the Influence of Frost Layers on the Heat Transfer Characteristics of Cryogenic Valves for Polar LNG Ships

To investigate the impact of frost-layer formation on the heat transfer characteristics of cryogenic valves in LNG vessels, this study derived the temporal variation in the valve’s temperature field based on the thermodynamic characteristic parameters of the low-temperature valve. Additionally, a frost formation model was developed for the drip tray. This considered the physical model characteristics of the tray, and the frost thickness was calculated for different times. The morphology of the calculated frost layer was coupled with the low-temperature valve model for heat transfer calculations to explore the influence of the frost layer on valve heat transfer characteristics. The results show that, in the initial stage of frost formation, the frost layer acts similarly to a finned heat sink, enhancing the thermal exchange efficiency at the surface of the drip tray, which results in a temperature increase in the drip tray and stuffing box compared to the frost-free condition. However, as the frost layer grows on the surface of the drip tray, the surface heat transfer resistance increases, gradually diminishing the enhancing effect of the frost layer on the heat dissipation of the drip tray. The results validate the dual role of the frost layer in the heat transfer process of low-temperature valves, providing important insights for the design and optimization of such valves.

Three-Dimensional Stacked Stretchable Thermoelectric Device for Virtual Sensation.

Stretchable electronics have significant applications in wearable applications. However, the extremely low thermal conductivity of elastic encapsulation hinders heat dissipation, leading to performance degradation. For instance, stretchable thermoelectric devices (TEDs) can be used for skin temperature regulation, but poor thermal management limits their cooling performance. This article proposes advanced material and fabrication optimization for stretchable TED with a three-dimensional structure, achieving enhanced performance through the stacked integration of multilayer thermoelectric unit networks. Techniques such as laser ablation are employed to create thermal vias, significantly improving interlayer thermal exchange efficiency. The resulting device can achieve 30% stretching and provides a stable and long-term 10 °C skin cooling under normal arm movement. Additionally, by integrating temperature sensing and control circuits, the fabricated wearable closed-loop system can programmatically regulate skin temperature, suitable for virtual temperature and pain sensation. The 3D integration method and thermal via construction technique proposed in this article can also be applied to other high-power stretchable electronics.

Cloud-based adolescent physical health research incorporating cell molecular biomechanics insights into predictive modeling and biometric algorithms

The physical health of adolescents is critical to their future development and quality of life. However, there is still much room for improvement in monitoring and intervention of adolescent physical health in colleges and universities. Based on the National Standard for Student Physical Fitness and Health, this study proposes a physical health management framework for adolescents that combines a cloud platform and real-time data analysis. Through an innovative health monitoring and early warning system and feedback mechanism, the effectiveness of health intervention was significantly improved. Body mass index is related to the balance between energy intake and expenditure at the cellular level. Excessive calorie intake can lead to an increase in adipose cells, which secrete molecules that can affect overall metabolism and biomechanical stress on tissues. Lung capacity is linked to the elasticity and strength of the alveolar cells and the connective tissue in the lungs. he proper functioning of these cells, regulated by intracellular signaling pathways and molecular interactions, determines the efficiency of gas exchange. The 50-meter run, seated forward bending, standing long jump, pull-ups/sit-ups, and 800-meter/1000-meter run all involve muscle contractions. Muscle cells contain actin and myosin filaments, and the sliding of these filaments, regulated by calcium ions and other molecular signals, generates the force required for movement. The graded early warning parameters established by the system can thus be seen as indicators of potential disruptions in these cell molecular biomechanical processes. The innovative health monitoring and early warning system and feedback mechanism not only help students recognize the weaknesses in their physical functions from a macroscopic level but also potentially identify areas where cell molecular biomechanical imbalances may exist. This enables physical education teachers to formulate personalized training plans that can target and correct these imbalances, as experimentally validated by the system's ability to accurately identify health risks and enhance the overall health of students.

Enhancing heat transfer in heat exchanger tube using four-shape cutting cone (FSCC) inserts: A numerical analysis

ABSTRACT The study introduces a new design modification for regular smooth tubes, incorporating the four-shape cutting cone (FSCC) to enhance heat transfer without increasing friction charge. Numerical simulations are used for processes heat and flow characteristics in the turbulent flow regime using certain parameters, ranging from 4000 ≤ Re ≤32,000. FSCC inserts can improve heat transmission, which lowers energy consumption in heat exchanger tube and helps achieve sustainability goals. A FSCC vortex was placed inside a smooth tube that measured 1500 mm in length, 30 mm in inner diameter (Din), and 35 mm in outer diameter (Do) for testing purposes. The FSCC measured (Dtop) = 20 mm at the top and Dbase = 28 mm at the base, with a thin 0.8 mm thickness (t). In this study, the Nusselt number (Nu), friction factor (fr), and thermal performance evaluation criteria (TPEC) are examined in relation to FSCC perforations (N = 0, 2, and 3) and pitch-to-hydraulic ratios (PR = P/Din = 2.5, 3.5, 4.5, and 5.5). The effects of perforations, i.e. hole number N = 0, 2, 3 and P/Din = 2.5, 3.5, 4.5, and 5.5, are considered for the analysis. The integrated tube has higher TPEC and average Nusselt numbers as compared to the smooth tube. Additionally, it uses perforations and to look at fluctuations in the average entropy generation rate (Savg). The study found that FSCC-inserted tubes have a 9.3 and 17.9 times higher Savgf than smooth tube at Re = 32,000 and 4000, respectively, for N = 0 FSCC heat exchanger tube, but at Re = 32,000, the Savgh of FSCC is 0.4 times lower. Smooth tube improves average entropy generation (Savg), while friction flow creates irreversibility defects. Smooth tube performance in Savg is inferior, with Savgh declining with Re and N. According to the study, vortex/swirl flow, boundary layer disturbance, and fluid mixing are the main factors influencing fluid flow, which is improved by the FSCC integrated tube and improves heat exchanger performance. Nusselt number and the friction factor both decrease as perforations increase while TPEC also increases. The results suggest that the FSCC is a useful tool for improving the efficiency of tube heat exchangers. The maximum TPEC is observed around 2.44 for N = 0 at Re = 4000 and P/Din = 3.5.

Influence of process parameters in ion exchange on the properties of the obtained 5A zeolite powder

Zeolite 5A is highly regarded in adsorption processes among zeolites, making it valuable for various commercial applications. It is typically synthesized from 4A zeolite by replacing Na+ ions in the crystal lattice with Ca2+ or Mg2+ ions through an ion exchange process. This substitution increases the pore volume, enlarges pore openings, and enhances the zeolite's adsorption capacity. From an industrial and commercial production standpoint, defining the optimal process parameters for producing 5A zeolite is crucial. This study investigates the effects of ion exchange temperature, ion exchange duration, and the concentration of active components in the system on the characteristics of the resulting 5A zeolite powder. The ion exchange process was carried out using a MgCl₂•6H₂O solution to produce the Mg2+ form of 5A zeolite, known as Na,Mg-A zeolite. The powders obtained after ion exchange were analyzed for their chemical composition and water adsorption capacity. Furthermore, the samples were characterized using granulometry and particle size distribution analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FT-IR). The results revealed significant correlations between process parameters, ion exchange efficiency, crystallinity, and adsorption properties. These findings provide insights into the optimal conditions required for the effective production of 5A zeolite.

EVALUASI KINERJA HEAT EXCHANGER 260E-103 PADA KILANG LUBE OIL COMPLEX III UNIT 260 PT KILANG PERTAMINA INTERNASIONAL RU IV CILACAP

In the process of processing petroleum, PT Pertamina International RU IV Cilacap is equipped with a heat exchanger asa supporting tool for the production and processing. Heat exchanger functions as a heat exchange that works with theprinciple of heat exchange without mass transfer. The use of heat exchangers that are in extreme environments and areused for a long period of time to pass fluids, there is a high probability of deposit formation or impurities that can affectthe pressure drop and decrease the performance efficiency of the heat exchanger in terms of heat exchange. Planning forcleaning must be considered to maintain the performance of the heat exchanger performance so that it remains in optimalcondition. The heat exchanger that will be evaluated in this study is Heat Exchanger 260E-103 at PT PertaminaInternational RU IV Cilacap. The research was conducted using quantitative methods through the calculation of foulingfactor, pressure drop, and heat transfer efficiency. The results showed that the Rd value of Heat Exchanger 260E-103 ofLMO was 0.0317 hr ft2 oF/Btu; 0.0058 hr ft2 oF/Btu; 0.0048 hr ft2 oF/Btu, MMO was 0.0193 hr ft2 oF/Btu; 0.0157 hr ft2oF/Btu; 0.0070 hr ft2 oF/Btu, and DAO of 0.0153 hr ft2 oF/Btu; 0.0193 hr ft2 oF/Btu; 0.0029 hr ft2 oF/Btu. The pressuredrop value of Heat Exchanger 260E-103 of LMO is 12.021 Psi; 10.632 Psi; 10.416 Psi, MMO is 11.077 Psi; 11.108 Psi;10.435 Psi, and DAO is 14.149 Psi; 13.764 Psi; 13.625 Psi. The efficiency for Heat Exchanger 260E-103 of LMO is22.81%; 79.47%; 82.16%, MMO is 29.07%; 46.03%; 72.16%, and DAO is 17.43%; 60.06%; 45.04%. The results showthat Heat Exchanger 260E-103 is not suitable for use because it has Rd and pressure drop values exceeding normallimits, and efficiency is below standard.

Recent Advances and Future Directions in Extracorporeal Carbon Dioxide Removal.

Extracorporeal carbon dioxide removal (ECCO2R) is an emerging technique designed to reduce carbon dioxide (CO2) levels in venous blood while enabling lung-protective ventilation or alleviating the work of breathing. Unlike high-flow extracorporeal membrane oxygenation (ECMO), ECCO2R operates at lower blood flows (0.4-1.5 L/min), making it less invasive, with smaller cannulas and simpler devices. Despite encouraging results in controlling respiratory acidosis, its broader adoption is hindered by complications, including haemolysis, thrombosis, and bleeding. Technological advances, including enhanced membrane design, gas exchange efficiency, and anticoagulation strategies, are essential to improving safety and efficacy. Innovations such as wearable prototypes that adapt CO2 removal to patient activity and catheter-based systems for lower blood flow are expanding the potential applications of ECCO2R, including as a bridge-to-lung transplantation and in outpatient settings. Promising experimental approaches include respiratory dialysis, carbonic anhydrase-coated membranes, and electrodialysis to maximise CO2 removal. Further research is needed to optimise device performance, develop cost-effective systems, and establish standardised protocols for safe clinical implementation. As the technology matures, integration with artificial intelligence (AI) and machine learning may personalise therapy, improving outcomes. Ongoing clinical trials will be pivotal in addressing these challenges, ultimately enhancing the role of ECCO2R in critical care and its accessibility across healthcare settings.

Additive Manufacturing of a Frost-Detection Resistive Sensor for Optimizing Demand Defrost in Refrigeration Systems.

This article presents the development of a resistive frost-detection sensor fabricated using Fused Filament Fabrication (FFF) with a conductive filament. This sensor was designed to enhance demand-defrost control in industrial refrigeration systems. Frost accumulation on evaporator surfaces blocks airflow and creates a thermal insulating barrier that reduces heat exchange efficiency, increasing energy consumption and operational costs. Traditional timed defrosting control methods can mitigate these effects but often lead to inefficiencies due to their inability to align with actual frost accumulation, which can vary according to system and environmental conditions. Frost-detection sensors aim to solve this problem by acting as a tool to support defrosting control. A series of tests were conducted to evaluate the sensor's performance in detecting frost under controlled conditions on a heat exchanger (HX). The sensor reliably detected frost in all cases, demonstrating its effectiveness in real-time frost detection. The sensor measurements were validated by comparison with results obtained through a computer vision method, confirming its reliability. It was also found that the sensor can detect temperature changes. This advancement in sensor technology highlights the potential of additive manufacturing to provide cost-effective, customizable, replicable, and compact sensor designs, contributing to improved system performance and energy efficiency in refrigeration systems.

Heat and mass transfer process simulation and structure design of a water-cooled fin solid metal hydride storage system

The heat transfer efficiency of a metal hydride reactor significantly affects its hydrogen absorption and desorption performance. Incorporating additional heat transfer structures can effectively enhance the heat transfer efficiency of hydrogen storage tank. To explore the impact of internal heat transfer structure on the hydrogen absorption capability of the reactor, a novel designed hydrogen storage tank with multi-ring hollow heat transfer fins was proposed. Firstly, a mathematical model is developed to describe the heat and mass transfer process during the hydrogen absorption, and the model is verified by hydrogen absorption experiments. Secondly, the heat transfer structure of multi-ring hollow fin reactor with three-fin structure is determined by comparing the effects of the structure of heat exchanger pipe and the number of heat exchanger fins on the heat transfer efficiency and hydrogen absorption rate of the system. Finally, the effects of flow velocity, temperature of heat transfer fluid and hydrogen absorption pressure on the hydrogen absorption efficiency of the system were compared. The numerical results show that the proposed reactor has shown an improvement in average heat exchange efficiency and average hydrogen absorption rate by 75.49% and 55%, respectively, compared to the initial reactor. The flow velocity and temperature of the heat transfer fluid have an influence on the heat exchange performance of the system, with an impact ranging from 7.69% to 62%, but little effect on the average hydrogen absorption rate of the system, and the hydrogen absorption pressure significantly affects the hydrogen absorption rate. The higher hydrogen absorption pressure can effectively extract the hydrogen absorption rate of the system, but the higher hydrogen absorption pressure imposes greater requirements for the heat transfer conditions of the system.

Numerical Simulation for Air Distribution Optimization in a 750t/D Waste Incineration Furnace

ABSTRACT Simulation research on the combustion process of municipal solid waste in a 750-ton/day incinerator was conducted by using the FLUENT software. The effects of excess air coefficient, the ratio of secondary air to burnout air, and the injection angle of secondary air SA1 or SA2 on the waste combustion process, flow field distribution, heat exchange efficiency of the incinerator, and the emission rules of flue gas NOx were studied. The results show that the optimal combustion conditions are 1.74 and 1.8 of the excess air coefficient, and 3 to 1 of the ratio of secondary air to burnout air. Moreover, the flow field inside the furnace was significantly affected by the injection angle of the secondary air. Under the given experimental conditions, there is a 5.2% enhancement in the heat exchange efficiency of the incinerator by adjusting the injection angle of SA1 to 45 degrees. Correspondingly, when the incinerator’s efficiency is at 20%, it is equivalent to an overall efficiency increase of 1.4%. When the injection angle of SA2 is adjusted to 40 degrees, the heat exchange efficiency increases by 15.3% and the efficiency improvement is equivalent to 3.6%. In addition, compared to parallel injection of secondary air, this air distribution adjustment can maintain a higher flue gas velocity in the duct, reduce ash deposition on the boiler surface, and extend equipment life. These results provide the valuable insights for actual combustion scenarios.

Computational Fluid Dynamics Analysis of Self-Sustained Laminar Flow Oscillations in Singular Grooved Ducts

Research Background: Modeling oscillatory flow in singular grooved ducts within the laminar regime provides insight into fluid mechanics that could enhance applications such as heat transfer in nuclear reactors. Previous research has identified pulsations in grooved channels under turbulent conditions with high Reynolds numbers, contributing to enhanced heat exchange efficiency. These pulsations are influenced by the axial flow in and out of the main channel from a continuous groove. Contribution of This Study: This study extends the understanding of flow oscillations to simpler geometries and lower Reynolds numbers, specifically within a laminar flow regime capped at a Reynolds number of 2,000. By simplifying the duct geometry to a rectangular main channel with a singular continuous groove, the research employs computational fluid dynamics tools, primarily OpenFOAM, facilitated by Compute Canada's clusters. It investigates the fluid flow characteristics—strength, frequency, velocity gradient, and oscillation behaviours—associated with the geometry of the gaps and channels. This approach helps in pinpointing the dependency of flow characteristics on specific geometric configurations, potentially laying groundwork for optimizing designs in practical applications.

A novel mechanism and model of hydrogen isotope exchange in vacancy considering nuclear quantum effects

Abstract Tritium (T) retention in plasma-facing materials (PFMs) raises significant radiological safety concerns and adversely affects the self-sustained burning of T in fusion reactors. Therefore, the removal of retained T from PFMs has become an urgent task. Hydrogen isotope (HI) exchange has proven to be an effective method for T removal. However, the microscopic mechanisms, particularly the role of isotope effects, remain insufficiently understood. For the first time, this work employs path integral molecular dynamics to account for the nuclear quantum effects of HIs and explore the microscopic mechanisms of HI exchange in tungsten (W) vacancies. Atomic-scale simulations reveal that the fundamental principle of HI exchange is the reduction in binding energy between HIs and vacancies as the defect filling level increases, involving two key processes: de-trapping and trapping. These processes are influenced by isotope effects, with pronounced differences observed at low temperatures. Notably, T exhibits a higher probability of de-trapping from vacancies compared to hydrogen (H), while vacancies demonstrate a stronger affinity for trapping H. In contrast, the isotope effect is less pronounced between deuterium (D) and H, leading to different exchange efficiencies between H and T, as well as between D and T. Based on these isotope effects, we proposed a detailed microscopic mechanism for HI exchange in vacancies and developed a T evolution model that accounts for variations in HI concentrations. This work advances our understanding of HI exchange for T removal applications and offers a more accurate assessment of T retention in future D–T environments.

Design Optimization of a Shell-and-Tube Heat Exchanger Based on Variable Baffle Cuts and Sizing

Abstract This article investigates the optimization of a shell-and-tube heat exchanger design through the optimization of baffle spacing and cut. This study focuses on the impact of baffle spacing (20–35%) and baffle cut percentage (20–35%) on heat transfer performance while considering the effect of the presence or the absence of seals. This study aims to optimize the heat exchanger design by using computational fluid dynamics (CFD) to reduce the pressure drop and increase the heat transfer. Studying the flow in heat exchangers is challenging due to its complex physics, especially in nonstandard geometries or novel fluid systems, which makes traditional methods relatively less accurate compared to modern approaches. The following fluid is so far uninvestigated for CFD analysis of heat exchangers: a mixture of 80% ethanol and 20% water is used as the tube-side fluid and water is used as the shell-side fluid. The Bell–Delaware method is employed for initial thermal analysis, followed by CFD simulations using ansys fluent to assess the influence of design modifications on heat transfer efficiency and pressure drop. The presence of seals is shown to improve the heat transfer efficiency by about 10.9% compared to the case when seals are absent, while optimal baffle spacing and baffle cuts are able to increase the efficiency of the heat exchanger by about 110% not inclusive of the effect of seals. Our findings show that the performance of a shell-and-tube heat exchanger is improved dramatically by the addition of seals and optimal selection of baffle cut and spacing.

COVID-19 and market efficiency in ASEAN-5 countries: Stochastic Frontier Analysis

This research paper aims to explore the market efficiency of stock exchanges in of ASEAN-5 countries, Indonesia, Malaysia, Singapore, Thailand, and the Philippines, during the COVID-19 pandemic. Stock market efficiency is the degree to which stock prices reflect all available relevant information. In an efficient market, stock prices will immediately rise or fall to reflect new information released by a company. This study uses the Stochastic Frontier Analysis (SFA) method to determine the efficient value over time. Market efficiency generally refers to how well financial markets in these selected countries reflect all available information, particularly in the context of the COVID-19 pandemic. SFA is useful here as it can separate random errors from inefficiencies, allowing us to isolate the impact of COVID-19 on market efficiency levels across these countries. The results show that the stock markets of ASEAN-5 countries (Indonesia, Malaysia, Thailand, Singapore, and Philippines) are efficient during the COVID-19 pandemic. Based on the hypothesis test, for the overall period of 2021 and 2023, the average efficiency ranges from 0.68 to 0.72, and for the time period/per year the average efficiency ranges from 0.66 to 0.74. The efficiency of the Philippine stock market based on time period/per year shows the average maximum efficiency in 2021 (0.74) and 2023 (0.73). While the average efficiency of the Malaysian stock market shows the minimum level of efficiency in 2020 (0.66) and 2021 (0.68). AcknowledgmentThe authors would like to thank the Research and Innovation Institute (LRI), Universitas Muhammadiyah Surakarta, for the enormous financial support in writing this study.

Building a Digital Twin for a Ground Heat Exchanger

AbstractThis research investigates the development of a digital twin (DT) for ground heat exchangers (GHEs) and its potential to enhance the efficiency and sustainability of shallow geothermal energy systems. It introduces an innovative approach for building a GHE‐DT that connects the physical and digital systems to monitor key parameters, predict issues, and optimize energy efficiency. The process involves several phases including implicit knowledge codification, data‐driven analysis, model construction, and system design. The study emphasizes real‐time monitoring of the effective parameters: ground temperature and fluid conditions (flow rate, temperature, and pressure). The GHE‐DT's digital system mainly comprises three sections, namely, data storage, mathematical modeling, and data‐driven modeling. The role of the presented mathematical model is to simulate the GHE's behavior and assess its performance characteristics, such as the heat exchanger's effectiveness and efficiency. Additionally, the data‐driven model used in the proposed DT utilizes formal concept analysis and relation concept analysis to identify connections and associations among parameters for a better understanding of the GHE functioning. The GHE‐DT provides useful services including trend analysis, problem prediction, and correlation analysis. These services provide engineers and operators with the opportunity to increase dependability, save maintenance costs, and optimize GHE performance.

Improving energy efficiency of a heat exchanger using recovered metal chips during forced convection

Improving energy efficiency of a heat exchanger using recovered metal chips during forced convection

Characteristics of Three-Dimensional Pore-Fracture Network Development and Enhanced Seepage Heat Transfer in Hot Dry Rock Stimulated by Temperature Shock Effects.

Hot dry rock (HDR) geothermal is a sustainable and clean energy source. However, its development progress is hindered by creating seepage channels in deep reservoirs with low porosity and permeability. Traditional hydraulic fracturing techniques are ineffective for enhancing the permeability of these high-strength reservoirs. To address this, a cyclic nitrogen injection technique was proposed, which leverages the thermal gradients of the hot reservoir to stimulate a complex thermally induced fracture network. To study the three-dimensional pore-fracture structure and the flow characteristic of HDR under temperature shock effects, various high-temperature rock samples (200-500 °C) were treated with 5 cycles of liquid nitrogen cold shock. Using digital core technology, a visual pore-fracture network was reconstructed and the simulation of flow and heat exchange within this network was further performed. The main conclusions are as follows: Following the liquid nitrogen cold shock treatment with rock cores of 200-300 °C, only a few isolated micropores were formed, marked by low porosity and poor connectivity, yielding effective porosities of 0.79 and 1.52%, respectively. In contrast, the cold shock at 400-500 °C induced the formation of a reticulated pore-fracture network. This development was attributed to the combined effects of thermal stress and grain expansion, with an effective porosity reaching 12.58%. Further, a pore network model revealed a substantial increase in both the pore number and size, especially under the cold shock of 500 °C cores, where the largest pore radius reached 2133 μm. The permeability of the representative elementary volume increased significantly with the rising cold shock temperature difference, escalating from 13.79 μm2 at 200 °C to 1101.39 μm2 at 500 °C. This shift signifies a transition from localized to more extensive flow paths. Based on the actual pore-fracture network, a simulation of heat extraction from HDR was conducted, showing that the exchanged heat increased from 4.51 × 10-8 to 8.34 × 10-8 W with the rise in the temperature difference. Within the temperature range of 300-400 °C, a singular flow path was observed, characterized by minimal fluid transport but elevated exit temperatures. Meanwhile, at 500 °C, a superior heat exchange network was established, featuring improved fluid transport and heat exchange efficiency.

Impact of karst groundwater seepage on heat transfer efficiency of geothermal heat exchangers

In karst regions, groundwater flows through complex conduits and fractures, resulting in substantial variations in flow velocity and temperature, which impact the efficiency of ground heat exchangers (GHEs). In this study, numerous model experiments were carried out to examine the temperature distribution of the stratum surrounding GHEs under karst groundwater seepage conditions. A 3D numerical model and experimental platform were developed to simulate the interaction between seepage and GHE thermal dynamics under varying seepage velocity, seepage temperature and operating modes. Model experiment results show that increasing seepage velocity significantly enhances heat transfer efficiency and mitigates thermal accumulation. The influence of karst groundwater seepage results in significantly less temperature fluctuation upstream compared to downstream. As seepage velocity increases from 3.59 × 10−6 m/s to 1.08 × 10−5 m/s, the temperature differential between upstream and downstream regions rises by 73 %, while the heat transfer efficiency of U-shaped pipes improves by 36.7 %. Variations in seepage temperature also play a pivotal role, with heat exchange efficiency increasing by 51.3 % as seepage temperature rises from 58.2 °C to 94.3 °C. The heat exchange capacity of GHEs and the temperature difference between downstream and upstream increase with the rising temperature of karst subsurface water seepage. The core impact of seepage temperature lies in how groundwater seepage initially alters the temperature field of the strata around the GHE, ultimately influencing the efficiency of heat exchange between the soil and the buried pipe. This research provides new insights for optimizing GHE systems and ensuring their long-term stability and energy efficiency in karst region.

Experimental studies on heat transfer performance of a heat exchanger with drilled twisted tape inserts

Abstract Heat exchangers are vital components in various systems where the crucial process of heat exchange takes place. This process typically occurs across the copper wall of a tube, facilitating the transfer of thermal energy between fluids. However, the efficiency of this heat exchange is fundamentally limited by the geometry of the components of the heat exchanger. To enhance the performance and efficiency it is necessary to increase the rate of heat transfer. By optimizing this process, industries can achieve better energy efficiency, reduced operational costs, and improved system reliability. In the present study experimental study of the heat exchanger was accomplished using the drilled twisted tapes. A simple copper tube was equipped with inserts of twist ratios 2.5, 3.33, and 5.0. Additionally, both a classic type insert and a perforated type insert with perforation diameters of 5 mm and 8 mm were fitted inside the copper tube for experimental testing, analysis, and comparison with the heat exchanger without inserts. Overall, the study confirmed that both the classic twisted and perforated inserts can substantially improve heat exchanger performance, with larger perforations being especially effective in optimizing heat transfer. No single combination of the twist ratio and perforation diameter for an insert demonstrated the highest thermal performance factor across all the Reynolds number values. The heat exchanger with an insert featuring a twist ratio of 2.5 and a perforation diameter of 8 mm exhibited a high thermal performance factor in the lower Reynolds number range. In contrast, an insert with a twist ratio of 3.3 and a perforation diameter of 5 mm showed a high thermal performance factor in the higher Reynolds number range. The highest thermal performance factor recorded was 2.37 for the insert with a twist ratio of 2.5 and a perforation diameter of 8 mm.

Controllable non-Hermitian qubit–qubit coupling in superconducting quantum circuit

We propose a theoretical scheme to realize the controllable non-Hermitian qubit–qubit coupling by adding a high-loss resonator in a tunable coupling superconducting quantum circuit. By changing the effective qubit–qubit coupling, the phase and amplitude of resonator–qubit interaction, and the qubits’ quantum states, we can continually tune the energy level attraction, the position of EP (exceptional point), and the non-reciprocity in the non-Hermitian superconducting circuit. The EPs and non-reciprocity can affect the quantum states’ evolutions and exchange efficiencies for two qubits in the non-Hermitian superconducting circuit. The controllable non-Hermitian and non-reciprocal interactions between two qubits provide new insights and methods for exploring the unconventional quantum effects in superconducting quantum circuits.