High Heat Exchanger Research Articles

Fabrication and enhanced thermal performance of a self-rewetting wick of silicon-based loop heat pipe

The improvement of chip integration has led to increased heat flux, making heat dissipation in confined spaces increasingly challenging. Silicon-based loop heat pipes (sLHPs) offer a simple, reliable, and easily integrated thermal management solution. Still, problems like dry-out, limited heat exchange area, and flow instability hinder further heat transfer improvements of sLHP. Therefore, a novel composite MCC wick (Microchannel-micropillar Composite Cell arrays wick) incorporating microchannels into the micropillar arrays has been designed and experimentally studied in this work. The results indicate that micropillar arrays provide fluid flow freedom and a high heat exchange area, benefiting the efficient evaporation of the working fluid. The microchannels enhance fluid flow stability by providing continuous adhesion, promoting the directional supplement of working fluid. Moreover, liquid-replenishment microchannels have been introduced to the proposed MCC wick, enabling self-rewetting of the wick and enhance liquid film evaporation. The highest effective thermal conductivity of the sLHP reaches 856 W/(m·K) after structural optimization, which is significantly higher than that of other sLHPs. This work is expected to provide valuable insights for the optimal design of LHPs and chip heat dissipation.

U-Turn Shape Effect on Effective Thermal Conductivity of Double Pass Photovoltaic Thermal (PVT) Systems Configuration

This study explores the thermal performance of double-pass photovoltaic thermal (PVT) systems by investigating the influence of turn shape on heat transfer characteristics using computational fluid dynamics (CFD) simulations. The aim is to evaluate various turn shapes, including half-circle, triangle, half-hexagon, half-octagon, and box, to determine their impact on turbulent intensity, effective thermal conductivity, and outlet temperature in PVT systems. The investigation reveals significant variations in heat transfer efficiency among the different turn shapes, with the triangle-shaped turn demonstrating superior performance across multiple parameters. The findings highlight that the triangle-shaped turn exhibits enhanced turbulence generation and heat exchange efficiency compared to other shapes. Specifically, the triangle-shaped turn achieves a maximum turbulent intensity of approximately 70%, surpassing other shapes which achieve around 60%. Moreover, the triangle-shaped turn displays a longer and more substantial area of high heat exchange, resulting in an effective thermal conductivity improvement of up to 20% compared to alternative shapes. Furthermore, the analysis indicates that the triangle-shaped turn exhibits a faster increase in outlet temperature, reaching steady-state conditions within 15 seconds, while other shapes require up to 19 seconds. These results underscore the significance of turn shape in optimizing the thermal efficiency of PVT systems.

Mathematical modeling of gas-phase mass transfer in hydrous materials for a total heat exchange ventilator

Total heat exchange ventilation systems are effective in achieving energy savings by reducing the ventilation load in buildings, while maintaining a certain amount of fresh outdoor air intake. As the system's elemental materials exchange both latent and sensible heat, hydrophilic chemical compounds may be exchanged simultaneously. Proper control of the exchange of hazardous chemicals and pollutants via these heat exchange elements is an important issue in the development of total heat exchange ventilation systems. In this respect, the development of a numerical model that facilitates repeated sensitivity analysis is important in the development of a new total heat exchanger that has high heat exchange efficiency and suppresses the exchange of polluting chemicals. This study proposes new hygrothermal and chemical compound transfer models for paper-based hydrous materials, which are the main components of total heat exchangers in indoor ventilation systems. Through a series of numerical analyses and experimental measurements, the prediction accuracy of the mathematical model was compared with experimental results for the gas transfer rate in hydrous materials and a building-sized total heat exchanger. The results demonstrated that an increase in water content in hydrous material has a significant impact on the permeability of water-soluble gases, with NH3 and HCHO permeability coefficients increasing by factors of 250 and 20 respectively. Conversely, for low-solubility gases such as CO2, the permeability coefficient only slightly increased at low humidity and remained largely unaffected thereafter. These findings contribute to the advancement of more efficient and safer total heat exchange ventilation systems.

A novel balanced teaching-learning-based optimization algorithm for optimal design of high efficiency plate-fin heat exchanger

Plate-fin heat exchangers (PFHE) are crucial for engineering applications. Pursuing high performance in PFHE design through optimal methods is common, yet challenging for traditional optimization approaches. Meta-heuristic algorithms (MAs) continuously achieve significant breakthroughs in this problem. This paper proposes a novel balanced teaching-learning-based optimization (NBTLBO) algorithm for PFHE optimal design, which optimizes entropy generation units and heat transfer area using objective functions derived from thermal modeling. NBTLBO introduces two phases, as straightforward as that of TLBO, that collaborate to balance exploitation and exploration, offering substantial superiority over TLBO. This addresses the limitations of existing TLBO studies that involve complex multiple phases and neglect phase interactions. The experiments reveal that NBTLBO achieves the best ranking in CEC 2014 and 2020 benchmarks compared with many popular MAs and even their enhanced variants. It also yields the best results across all four PFHE design examples, showing significant improvement over TLBO and other existing methods. A non-dominated sorting NBTLBO algorithm is developed for multi-objective PFHE design, achieving improved Pareto results compared to existing methods. It verifies that NBTLBO, despite its simplicity akin to TLBO, effectively balances exploitation and exploration, thereby achieving notably enhanced performance, rendering it a preferred option for tackling global optimization challenges.

Liquid-solid interface polymerization: A simple approach for efficient polyamide/polyethylene thin film composite total heat exchange membranes construction

A simple liquid-solid interface polymerization (LSIP) strategy was developed to prepare high performance polyamide (PA) based thin film composite (TFC) total heat exchange membranes (THEMs) to avoid the use of organic solvents and surfactant during the inverse phase interface polymerization processes between piperazine (PIP) and 1,3,5-benzenetricarbonyl trichloride (TMC) on porous polyethylene (PE) substrates. The non-polar organic solvent in the TMC organic phase coated on the surface of the PE surfaces was completely removed beforehand by evaporation to form polar TMC solid coating on the PE surfaces and facilitate the quick spreading of lately added aqueous PIP solutions, forming dense and highly cross-linked PA separation layers with superior total heat recovery efficiency and CO2 barrier property. The effects of TMC loading level, PIP concentration, and LSIP reaction time on the structure and performance of PA/PE-TFC THEMs were systematically investigated, leading to the formation of THEMs 0.20P-0.10T-6 with ultra-low CO2 permeance of 0.9 GPU, and high sensible heat exchange efficiency of 94.3 %, water vapor flux of 2128 g m−2·24 h−1, and enthalpy exchange efficiency of 76.8 %.

Configuration method for medium-deep ground source heat pump system considering renewable energy consumption and smart grid interaction

Medium-deep ground source heat pump (GSHP) systems have the advantages of low carbon, high heat exchange intensity, good thermal storage capacity, and intermittent operation characteristics, which are conducive to renewable energy consumption and grid demand response. The source-side parameters affect the configuration of underground borehole engineering, heat pump units, and other equipment. However, current research mainly focuses on the underground heat exchanger modeling, underground heat exchange, and system operation control, while there are few studies on multi-factor ground source-side parameter design and optimal configuration. In this study, the indicator analyzing the unsteady features and thermal balance state of medium-deep geothermal resources was introduced, and the source-side water temperatures were optimized based on the dynamic characteristics of the geothermal and building sides. A simulation configuration methodology for the source-side flow rate and storage capacity was developed considering the electricity prices, life-cycle cost (LCC), and grid interaction. The optimization of the ground source-side design temperature, flow rate, and capacity parameters of residential and office building heating scenarios were analyzed in northern China, respectively. The results showed that the borehole inlet and outlet temperature can be designed to 5.5 °C/17.5 °C under the annual sustainable state, and the optimal flowrate can be set to 65.77 m3/h, to achieve the lowest cost and highest heating season guarantee rate for the residential scenario. For the office building with optimal system and storage capacity, the average annual LCC is 192,000 yuan/year, with the cumulative peak shaving of 55.8 %, and an increase of 103.3MWh renewable electricity consumption.

Experimental study on dynamic deformation and breaking mechanism of high-temperature hard rock cutting by abrasive water jet

The development of deep geothermal resources encounters challenges related to high temperatures and hard reservoir rocks. Abrasive water jets (AWJ) offer a potential solution to enhance the efficiency of breaking high-temperature hard rocks in deep ground. This mainly originated from their combined characteristics of jet cooling impact and high-speed abrasive grinding. In order to investigate the dynamic deformation process and rock-breaking mechanism of high-temperature hard rocks cut by AWJ, laboratory tests were conducted on high-pressure abrasive water jets cutting granite, sandstone, and marble. Rock strains were monitored using dynamic strain gauges and the digital image correlation (DIC) technique. The results indicate that in the process of abrasive jet cutting high-temperature hard rock, the rock strain is divided into three stages: compression deformation, deformation release, and stable deformation. The strain response zone can be divided into strain concentration zone, strain transition zone, and strain weak response zone. The high strain region and heat exchange region of high-temperature hard rock during AWJ cutting process are almost consistent. Jet vaporization weakens the water cushion effect during the water hammer stage, leading to high strain concentration at the stagnation point of the jet. During the stagnation stage, the fluid weakens the binding of particles, the abrasive becomes more divergent, and the range of high strain response region expands. Unlike the dynamic strain generated by jet erosion of hard rock, when jet cutting rocks, the strain in the vertical jet direction is generally greater than that along the jet direction. The cutting effect increases with the increase of rock temperature. When the rock temperature is 300 °C, the cutting depth of sandstone, granite, and marble increases by 50 %, 120 %, and 180 %, respectively. Under the combined effects of high-frequency jet impact, high-speed abrasive grinding, and thermal stress, hard rock undergoes varying degrees of damage and failure.

Study on electric vehicle thermal management system using phase change materials and CO2 heat pump waste heat recovery under cold conditions

The thermal management system plays a pivotal role in electric vehicle. The CO2 heat pump technology, which performs well at low temperatures and environmentally friendly, has emerged as one of the most promising solutions for optimizing the thermal management system of electric vehicles. However, at −30 ℃ to −15 ℃, the CO2 heat pump faces issues with excessively high discharge temperatures and limited Gas Cooler heat exchange area, thereby there is potential of waste heat recovery and utilization. This paper proposes a thermal management system that utilizes PCM heat storage to recover waste heat from the CO2 heat pump. The system aims to insulate the battery during winter parking, reducing the battery’s preheating energy consumption and enhancing the vehicle’s overall energy utilization efficiency. This paper explored the waste heat characteristics of CO2 heat pump under various conditions. Subsequently, Numerical structural optimization analysis of the PCM heat storage was conducted. Finally, an economic analysis of the PCM heat storage is performed, considering the boundary condition of the urban climate. The result showed that Under the heat production control strategy, the PCM heat storage has a high heat storage rate at −30 ∼ -20 ℃ ambient temperature, reaching 1470 W ∼ 2709 W, and the heat storage time is less than 1 h. At −15 ℃, where the energy saving is maximized, the system battery coupled with the PCM heat heat storage consumes only 0.88 kWh for preheating, saving 44 % compared to the 1.58 kWh consumed by the baseline. The PCM heat storage demonstrates a better energy-saving effect in colder areas.

Thermal-hydraulic performance of modified Schwartz-Diamond solid-networks triply periodic minimal surface structures

The triply periodic minimal surface (TPMS) structures are widely used as disturbance core structure in high performance heat exchangers. In this paper, four modified Schwartz-Diamond solid-networks (SD-solid) TPMS structures, one structure compressed along the flow direction (β = 2), and three structures compressed along the spanwise direction (α = 2, α = 3, and α = 4) are designed. Flow and heat transfer processes in the structures are studied with computational fluid dynamics (CFD) and experimental method. The performance enhancement criterion (PEC) is employed to evaluate the overall heat transfer performance. As the results of simulation, the overall heat transfer coefficient (hoverall) of α = 2, α = 3, and α = 4 is 10.04 %, 34.34 %, and 62.03 % higher than that of SD-solid respectively. The PEC of α = 2, α = 3, and α = 4 structures is 27.35 %, 34.17 %, and 34.95 % higher than that of the original SD-solid structure, respectively. Two samples of them (β = 2 and α = 2) are fabricated using additive manufacturing and their thermal–hydraulic performance is experimented on a flow and heat transfer experimental platform. Comparing the experimental results of the hoverall, the β = 2 structure is 68.5 % higher and the α = 2 structure is 23.06 % higher than the original SD-solid structure. However, for the average pressure drop, the β = 2 structure is 448.5 % higher and the α = 2 structure is 66.77 % lower than the original SD-solid structure. It is proved that the modified SD-solid structure compressed along the spanwise direction has the performance of enhancing heat transfer and reducing the pressure drop.

A novel type of additively manufactured high pressure mini-channel heat exchanger for precooling in hydrogen refueling stations

During refueling supercritical hydrogen into high pressure storage tanks, the fluid has to be cooled down to temperatures between -33°C and -40°C before entering the vehicle fuel tank. This cooling takes place while the hydrogen is at a pressure of up to 87.5 MPa. The requirements for the heat exchanger performing this task are very high. It has to be pressure resistant, compact enough to fit in the dispenser column and provide a high thermal performance to ensure a fast refueling with high mass flow rates. Only few conventional manufactured heat exchangers are able to fulfil these requirements. With the rise of additive manufacturing technology, especially laser powder bed fusion, new heat exchangers produced without use of conventional joining technologies can be realized. This manuscript presents a new type additively manufactured of mini-channel heat exchanger. It is developed in a joint research project involving the Leibniz University Hanover and an industrial heat exchanger manufacturer. The apparatus has a design pressure of 105 MPa and will be suited to be used in hydrogen refueling stations. The thermal requirements and the design of the apparatus are described. Thermal power and pressure drop for the full-size heat exchanger are calculated via a cell model. Scaled smaller heat exchangers made of 1.4404 stainless steel are additively manufactured via laser powder bed fusion (LPBF). The thermofluiddynamical performance of the scaled apparatus is measured in a testbench to verify the applicability of the used correlations. Deviations in hydraulic diameter and surface roughness are taken into account. Existing correlations are fitted to the new geometry.

Vibration-Free 40-80K Turbo-Brayton Cryocooler and its Very High Efficiency Recuperator for Earth Observation Instruments

Several studies have demonstrated that Reverse Turbo-Brayton cryocoolers could be the next space cryogenic revolution, thanks to their capability to provide vibration-free remote cooling in the temperature range of 4 to 150K and for medium to high cooling powers. With this motivation, Absolut System developed a very low vibration 40-80K Reversed Turbo-Brayton cooler, work performed under the ESA Technical Program Technical Research Program - 4000113495/15/NL/KML. The cooler is based on two turbo-compressor stages, a high efficiency recuperator and a cryogenic turbo-expander, for operation between 300 and 40K. Following the fabrication of the cooler, we performed tests on both individual components, compressors, expander and recuperator as well as on the complete cooler. The turbomachines use aerodynamic bearings, i.e. contactless bearings, generate very little vibrations and exhibit no wear over time. The characterizations performed during the project concern exported micro-vibration behaviors of the compressors and the expander, operating respectively up to 250,000RPM and 150,000RPM, and thermodynamic performance of the different elements. The cooler was tested down to its minimum temperature and required the development of specific operating procedures for the conditioning of the circuit. We report here in a first part the main results and observations stemming from the test campaigns carried out during the project. This work showed the necessity of putting additional effort into the recuperator, one of the most critical components of the cooler. Absolut System is thus also working in parallel on developing a very high efficiency and compact heat exchanger, which we report in a second part, for the specific needs of Turbo-Brayton Coolers in response to the ESA Proposal ESA-TDE-TECMTT-SOW-023649. The technology selected for this is based on the common tube and shell but using very thin tubes of small diameters (<1mm). The challenge of this exchanger is not only the manufacturing, but also the very stringent requirements. Obtaining an efficiency higher than 97.5% in a very small mass while maintaining very low pressure drops, makes for a very challenging project. We have performed the design phase, tested, and validated different aspects of the assembly. The design for the first breadboard model has been validated numerically and is in the fabrication process. Testing the exchanger will then take place to characterize the performances of the recuperator and allow for a comparison between experimental results and analytical and CFD models. This effort participates in placing the Turbo-Brayton cryocoolers at the forefront of space coolers and pushing Europe even further in State of Art advancements for space to bring us closer to fulfill future Space Explorations and Earth Observation missions.

Enhancing thermal efficiency in MHD kerosene oil-based ternary hybrid nanofluid flow over a stretching sheet with convective boundary conditions

The increasing demand for thermal management due to the high heat density heat exchangers for different technological and industrial processes draw the attention of researchers in heat transfer analysis to investigate the simultaneous solution to this problem. Keeping this in mind, the current work addressed the utilization of ternary hybrid nanofluid, a mixture of graphene oxide with silver and copper, to examine the heat and mass transfer enhancement of MHD Maxwell fluid. In the current model, the author discussed heat and mass transfer analysis of Maxwell MHD ternary hybrid nanofluid flow across a porous medium over an extending sheet. The energy and concentration equations are expressed to include the effects of Brownian motion and thermophoretic diffusion. Additionally, the effects of thermal radiation, activation energy, chemical reactions, and convective boundary conditions are considered. The similarity transformations are used to convert the nonlinear PDEs into ODEs. The impact of embedded factors on velocity, temperature, and concentration profiles is perceived graphically and mathematically by using the HAM technique. The convergence of computed solutions is ensured by h-curves. The significant outcomes from the analysis expressed that the flow distribution increases with slip and suction/injection factors. The concentration of the ternary hybrid nanofluid increases with an increase in thermophoretic diffusion (0.1–0.5), thermal biot number, and solutal biot number (0.1–0.5), however, a declining behavior is perceived with rising quantity of Schmidt number (0.6–0.8) and Brownian motion (0.1–0.5) parameters. Nusselt number shows a dominant behaviour with a higher magnetic factor. Similarly, the skin friction increases with an increase in thermal biot number and thermophoresis factor. It is revealed that the skin friction along x− direction increases from (0.78138, 0.833702, 0.897022, and 0.972526) for ternary hybrid nanofluid. Nusselt number increases from 2 to 5% (0.208936, 0.214288, 0.219799, 0.22555) when the volume fraction varies from 0.01 to 0.04 respectively.

Investigating the coupling effect of ventilation and GHEs on temperature distribution and heat transfer characteristics

Tunnel lining geothermal heat exchangers (GHEs) offer numerous advantages, including small area, cost-effectiveness and high heat exchange efficiency. It is a good equipment to utilize geothermal energy in tunnels. However, few research has been conducted on the combined impact of tunnel lining GHEs and ventilation on the temperature field of the surrounding rock. In this study, laboratory test model of combined impact of heat transfer between ventilation and GHEs was established, the effects of different flow rates and wind speeds on temperature field and heat exchange characteristics of the rock were investigated, and the changes in heat transfer under different operational conditions were analyzed. The findings reveal that tunnel ventilation initially enhances the heat transfer efficiency of GHEs, but subsequently decreases the overall heat transfer. Moreover, higher wind speeds exacerbate this negative impact. The radius of the heating ring decreases with increased heat transfer, and the temperature of the surrounding rock rises with heightened heat exchange at same locations within the heating ring. There are reasonable ranges of wind speed and GHEs flow rate, which are 1.5 m/s–2 m/s for wind speed and 0.4 m/s–0.6 m/s for flow rate, respectively. These results are important for the evaluation of thermal effect of tunnel lining GHEs and ventilation design.

Analysis of flow characteristics and heat transfer regulations for gas turbine blade middle double swirl cooling under different nozzle numbers

In this paper, the gas turbine blades middle double swirl cooling structure under diverse number of nozzles N are constructed to explore the heat transfer and flow behavior. The k-ω turbulence model are applied and the inlet coolant Reynolds number is 12500. The N vary by 4 to 11 and two cases are investigated. For case 1, the cross-sectional area of each nozzle is 6 mm2 for all structures. For case 2, the cross-sectional area of total nozzles stays the constant at 42mm2 when the N is varied. Results show that, in case 1, when the N increases, the area of the high heat exchange zone decreases but the distribution is more uniform. Moreover, the thermal performance factor ξ gets larger, but the average Nusselt number Nua decreases significantly. In case 2, when the N increases, the ratio of inclination to nozzle length increases for the jet near the outlet, Nua is almost constant but the heat transfer uniformity is improved. The best ξ is obtained when the N is 8. For case 1, as the N is increased, the Nua decreases significantly. Therefore, heat transfer and ξ should be considered by case 2 to select the optimum N.

A comprehensive analysis of heat transfer in a heat exchanger with simple and perforated twisted tapes based on numerical simulations

One of the most important methods to promote heat transfer (HT) in a heat exchanger (HE) is to use a twisted tape (TT) inside tubes. Therefore, in this paper, the result of the effect of TTs on the Nusselt number (Nu), and the performance coefficient of HEs in a laminar flow are investigated. plain tube (PT), simple TTs and perforated twisted tapes (PTTs) at 3 torsion ratio, blade numbers (N) 2, 4, 6 and 8 in the Reynolds numbers (Re) from 200 to 1000 are investigated. Ansys-Fluent computing software is used for this simulation. The findings indicate a positive correlation between the number of blades and both the Nu and the friction factor. It is important to acknowledge that the objective is to enhance the efficiency of the higher HE. Additionally, since there is an undesirable ratio between the rise of the Nu and the boost of the friction factor, so the HE coefficient decreases as the number of blades in TTs increases, from 6 to 8. The PTT with 6 blades provides the best performance coefficient. Compared to the simple TT, in the PTT, the Nu increases to 15.24%, the friction factor decreases to 22.26%, and the coefficient of thermal performance grows to 18.07%.

Experimental and numerical investigations into the fabrication of alumina ceramic surface microchannel by electrochemical discharge machining

The electrochemical discharge machining (ECDM) is an advanced and promising technology for fabricating micro structures. This method is effectively applicable for non-conductive hard and brittle materials micromachining, such as glass and ceramics. However, the ceramics high melting point and intense heat exchange effects during microchannel fabrication lead to the easy dissipation of thermal energy and the difficulty in processing. To address this issue and expanded the ECDM processing range. This paper dedicated to the investigation of the material removal mechanism and process characteristics for the alumina ceramic surfaces microchannels preparation. Firstly, this study explained the difference of the ECDM critical applied voltage and gas film generation mechanism by analyzing the volt-ampere characteristic curve of 20 wt% NaOH electrolyte with a tool immersed depth of 2 mm and 10 mm respectively. Then, a thermal removal finite element model (FEM) for ECDM was developed. The heat cumulative and intermittent cooling effects applied on the alumina ceramic surface dominated the materiel removal. Additionally, it can be found that the microchannel machining accuracy and bottom surface quality depended on the Gaussian heat source characteristics, gas film formation mechanism, heat accumulation effect, and temperatures spatial and temporal distribution. And a series of single factor experiments for evaluating the parametric studies such as the effect of discharge frequency, applied voltage, duty ratio and tool feed rate on the fabricated microchannel performance are executed. Finally, the complex three-dimensional structures of cross microchannel grid and zigzag microchannel array with variable depth were successfully fabricated on aluminum oxide ceramic surface. Notably, the results highlighted and enriched the ECDM stability, consistency and applicability for alumina ceramic surface microchannel fabrication.

Multi-objective optimization of heat charging performance of phase change materials in tree-shaped perforated fin heat exchangers

To enhance the convective heat transfer and overall thermal performance of horizontal latent heat storage (LHS) units, an innovative tree-shaped fin structure with perforations was introduced. A numerical simulation study examined the impact of perforation layers on the unit's overall performance. For a comprehensive analysis of the perforations' cumulative effect on the LHS unit, the Response Surface Methodology (RSM) was utilized to assess the influence of variations in perforation diameter and number on material consumption and heat exchange targets, deriving predictive correlations. The results indicated that compared to a non-perforated structure, the maximum improvement was observed with three layers of perforations, reducing material usage by 0.93%, while increasing the Nusselt number (Nu) and heat exchange by 10.19% and 36.51%, respectively. Moreover, the average temperature of the phase change material (PCM) in one and three perforated layers was higher than in the non-perforated tree-shaped fins, with complete melting times reduced by 5.37% and 2.51%, respectively. RSM results showed a negative linear correlation between increased perforation diameter and number with reduced material consumption, with the number of perforations having a more significant impact on heat exchange than their diameter. The Pareto optimal points obtained using the Non-dominated Sorting Genetic Algorithm II (NSGA-II) demonstrated lower material usage and higher heat exchange. Compared to the non-perforated tree-shaped fins, the Pareto-optimized solutions reduced material consumption by 2%–2.68% and increased heat exchange by 79.42%–94.45%. Analysis of the flow field, temperature field, and phase change process revealed that perforations significantly enhanced the mixing of PCM in different areas of the tree-like fins and secondary flow, with temperatures near the perforations increasing by 5–7K and flow velocity by 3–4 times, significantly promoting convective heat transfer.

Transformation behavior and inverse magnetocaloric effect in Ni45Co5Mn36.7In13.3-xGex melt-spun ribbons

In the present work the influence of Ge doping on crystal structure, microstructure, martensitic transformation (MT) and magnetocaloric effect (MCE) of Heusler-type Ni45Co5Mn36.7In13.3-xGex (x = 0, 2, and 3 at. %) metamagnetic shape memory alloys (MetaMSMAs) have been studied. Melt-spinning was used to prepare ribbons of these alloys since the ribbon shape ensures a high surface-to-volume ratio favoring a high heat exchange rate in a solid-state refrigeration. Furthermore, melt-spinning can induce a specific microstructure and stabilize metastable phases at room temperature. The ribbons were examined by X-ray diffraction at different temperatures, scanning electron microscopy, calorimetry, thermomagnetization, and magnetic field induced adiabatic temperature change measurements carried out across MT. It was found that Ge doping gave rise to enhanced antiferromagnetic interactions, stabilized martensitic phase, increased the MT temperature, causing larger magnetization jumps at MT and making narrower MT hysteresis. The x = 3 ribbon exhibited an inverse MCE at 303 K characterized by the isothermal magnetic entropy change value of |26.9|J/kgK at μ0H = 5 T and an adiabatic temperature change of ǀ1.5ǀ K at μ0H = 1.96 T. These values are comparable with the previously reported data on the Ni–Mn-based metamagnetic shape memory alloys in a bulk form.

Power disassembly equipment for high efficiency heat transfer plate heat exchangers

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.

Identifying regularities of fluid throttling of an inertial hydrodynamic installation

The article presents the results of experimental research conducted on a specially designed setup for pressurizing various types of fluids through throttle orifices. To determine the optimal operating mode of the thermal system, throttle nozzles of different diameters, specifically 1.5 mm, 2 mm, and 3 mm, were utilized. One of the primary advantages of vortex heaters is their high heat exchange efficiency. This is attributed to the vortical motions and turbulence generated within the device, which promote more vigorous fluid mixing, thus enhancing heat transfer efficiency. However, vortex heaters do have certain drawbacks. Vortical components may experience wear and require regular maintenance and replacement. Subsequently, during the course of experimental work, an alternative inertia-based hydrodynamic system for heating heat carriers was developed and installed in a laboratory experimental facility. The research focus was on technical water. The results indicated that the static pre-pressure generated by the supply of water from the water main into the system decreases as the rotor's angular velocity increases. Experimental investigations demonstrated that rotor rotation leads to a redistribution of flow characteristics in throttle orifices for both static and dynamic inertial fluid discharge. Given that any static column of liquid results in level flow through throttle orifices, their flow static parameters were established. Furthermore, the research revealed that with the increase in rotor angular velocity, the fluid pressure at the throttle orifices rises, while the share of fluid discharge from the initial static pressure decreases in the overall fluid flow