Intermediate Heat Research Articles

An experimental study of friction stir welding parameters effect on joint properties of aluminium alloy and copper plate

Joining dissimilar metals like copper and aluminium is a complex area of research for the manufacturing industry. To effectively join the AA7075 with copper plates, an experimental investigation on friction stir welding was carried out. A straight cylindrical pin profile tool of H13 tool steel was chosen for this study. On the advancing direction, the AA7075 plates were fixed under the condition of zero tool offset. The tool was positioned at a 2° tilt angle for the entire experiment. Tensile test, microhardness test, SEM and EDS analysis were completed to investigate the effectiveness of the process parameters (tool traverse and rotational speed) in combination with a modified set-up on the microstructure, tensile strength and microhardness of the joint. Fractography was conducted on fractured specimens to identify the mode of failure. Complex microstructures of swirl and vortex-type material flow patterns were created in the stir zone. As a result of SEM analysis, one of the samples (S5) had finer grains at intermediate heat input, which produced excellent microhardness and tensile strength. Fractography identified ductile failure as the predominant mode of failure in the joints. The results of this study include an ultimate tensile strength value of 221.091 MPa with a joint efficiency of 95.05%, yield strength of 159.035 MPa, maximum elongation of 9.335% and a microhardness value of 271 HV for specimen welded at a traverse speed of 60 mm min−1 and a rotational speed of 1400 rpm.

Ensuring maximum work and increasing effective efficiency when introducing intermediate heating in the cycle of a gas turbine plant

Ensuring maximum work and increasing effective efficiency when introducing intermediate heating in the cycle of a gas turbine plant

Assessment of the possibility of using heat-insulating and energy-saving equipment

The article deals with the problem of energy saving in the context of comparing contact heat exchangers. The advantages and disadvantages of various schemes are analyzed. It is proposed to use economizers of contact heat exchangers with active packing (HEAP) in boiler units of boiler houses. An analysis of the operation of one of the types of HEAP is given. The advantages of using HEAP with a two-circuit apparatus with a nozzle are considered. The main utilization plants and their parameters are described. Examples of the creation of designs for double-shell contact heat exchangers for the utilization of low-potential internal (side) energy resources (IER) are given. For branches of the chemical industry, a scheme of a scrubber-salt system using an intermediate heat carrier is proposed. The effective use of these devices for heating and humidifying air in ventilation and air conditioning systems is noted. The pros and cons of contact heat exchangers are considered in the framework of increasing the efficiency and environmental friendliness of the schemes. The ways of further increasing the efficiency of HEAP are consid

A New Proposal Generalized Predictive Control Algorithm With Polynomial Reference Tracking Applied for Sodium Fast Reactors

This paper proposes a generalized predictive control (GPC) with constraints and orthonormal Laguerre functions using the simplified model of the primary system (reactor core and intermediate heat exchanger (IHX)) of a prototypical sodium fast reactor (SFR). This paper develops a multiple-input multiple-output (MIMO) GPC with input constraints able to track polynomial references of any degree applied in coolant temperature difference across the core and fractional power. The manipulated variables of the GPC-SFR are the reactivity and the sodium flow rate of the primary and secondary pipes. Moreover, orthonormal Laguerre functions and step down condition number techniques were also applied to avoid the numerical ill-conditioning issue in quadratic programming of large systems. Thus, a GPC type-2 was designed to control fractional power, coolant temperature difference across the core and sodium tank temperature of the SFR primary system when temperature references change according to a linear ramp after reaching their steady-state operation, sustaining 100% power operation on the reactor. In order to analyze the load tracking capability of the GPC-SFR type-2, the load following from 100% fractional power (FP) to 60% FP at 0.8% FP/min rate is simulated. Constraints on the rate of coolant temperature difference across the core and reactivity were applied for the design safety. For comparison criteria, this paper compares the GPC-SFR type-2 with the GPC-SFR type-1, i.e, standard model predictive control (MPC), to verify the viability and superior performance of the proposal regarding: (a) ramp-tracking capability of temperature and load; (b) the rejections of a reactivity disturbance of -1 cent and a secondary sodium inlet temperature disturbance of +10°F; and (c) a simulation with uncertainty in reactor design. The simulations show that the GPC-SFR type-2 overcome the GPC-SFR type-1 robustness and performance.

Ионно-лучевое формирование серебросодержащей поверхности пористого кремния

The results of a study of the formation of a silver-containing porous layer on the surface of single-crystal silicon KEF-4,5 by ion-beam alloying are presented. A computer simulation of the process of ion doping of silicon with KEF-4,5, high-energy helium and silver ions was carried out using the TRIM/SRIM software package in order to determine the dose and energy neighborhoods of helium and silver ions necessary and sufficient in the experiment. The relief of the porous surface, the density of quasi-pores on the surface of implanted silicon, the elemental composition of the obtained porous composite silver-containing layers, taking into account the effect of intermediate heat treatment on it, are studied. The ion-beam formation of a silver-containing coating ensures the creation of a developed surface relief at the nanoscale with high reproducibility and controllability inherent in the ion doping method, which contributes to an increase in the yield of usable solar cell products. The technological modes of high reproducibility and controllability inherent in the ion doping method are determined based on the experimental data obtained for studying the relief of a porous surface and the density of quasi-pores on the surface of implanted silicon from the energy and dose of helium ions. Based on the study of the elemental composition of the quasi-porous composite silver-containing layer obtained by implantation of silver ions, the recommended parameters of implantation of silver ions have been established.

Inelastic behavior and creep-fatigue damage evaluation of intermediate heat exchanger for HTGR

Inelastic behavior and creep-fatigue damage evaluation of intermediate heat exchanger for HTGR

EFFECT OF WAVY TUBE STRUCTURE ON THE COMPREHENSIVE PERFORMANCE OF SUPERCRITICAL CARBON DIOXIDE AND LEAD BISMUTH EUTECTIC COMPACT HEAT EXCHANGER

In the combined system of lead-cooled fast reactor and supercritical carbon dioxide (S-CO<sub>2</sub>) Brayton cycle, the intermediate heat exchanger plays a key role in the whole power system. However, the existing heat exchanger cannot meet the trend of miniaturization of lead-cooled fast reactors. Considering the thermo-physical properties and heat transfer behaviors in both S-CO<sub>2</sub> and liquid lead bismuth eutectic are significantly different, an asymmetric compact coupled heat exchanger learning from the Honeycomb structure is proposed. Then the effect of the Reynolds number on the coupling heat transfer is discussed. When the Reynolds number of the cold side was changed from 57600 to 145000, the heat transfer coefficient of the heat exchanger increases by 79%, but when the Reynolds number on the hot side is changed from 29600 to 118000, the heat transfer coefficient only increases by 4.6%. To enhance the heat transfer and reduced thermal resistance on the S-CO<sub>2</sub> side, a wavy channel was used. The results showed that the wavy channels could significantly improve the field-synergy angle. In the smooth pipe, the averaged field-synergy angle is 88.7°, while in the wavy channel, the averaged field-synergy angle becomes 84.1° at α = 1.5. With the increase of wavy amplitude in S-CO<sub>2</sub> channel, the heat transfer coefficient and the friction factor increased, but the comprehensive heat transfer coefficient is in non-monotonic variation. The overall heat transfer coefficient of the wavy channel is 1.56-1.81 times than that of the straight channel in the range of Re<sub>SCO2</sub> = 86700 ~ 145000.

Experimental investigation and analysis on the cross flow characteristics over inline tube bundles with S/D=1.875

Helical tube bundles are usually used for steam generators (SGs) and intermediate heat exchangers (IHXs) of High Temperature Gas-cooled Reactors (HTGRs). The thermal hydraulic performance of SGs/IHXs is dominated by the cross flow convection over tube bundles in the primary side. Though cross flow over tube bundles were widely investigated as a basic flow pattern, few of them focused on tube bundles with 1.4-1.6<S/D<2-2.2 (S, tube pitch, D, tube diameter). However, the designs of HTGR SGs or IHXs prefer smaller tube pitches due to the relatively low heat transfer coefficient. In present investigation, velocity distribution, surface pressure distribution and drag/lift force of cross flow over tube bundle with S/D=1.875 are measured and investigated thoroughly in a wind tunnel. The velocity fields are measured using time resolved PIV and split hot film methods. The surface pressure distribution is measured using dynamic pressure transducers. The drag and lift forces are measured using high frequency wind tunnel balance. Due to the friction drag introduced by the bounded wall, the time averaged velocity in the flow passage next to the bounded wall is smaller than those in the middle flow passages. The surface pressure distributions between the impinging point and the separation point on tubes are characterized by the acceleration effects when fluid flowing into the region between neighboring tubes in the same row. The increasingly significant pressure recovery after separation results in the decreasing tendency of flow resistance coefficient with Reynolds number (Re) increment. A main frequency corresponding to Sr=0.114 (Sr, Strouhal number) is observed in both surface pressure and velocity spectrums, indicating that the vortex shedding induces the turbulent wake swinging. The turbulent wakes after tubes in the same row swing with no phase lag, while turbulent wakes of tubes in neighboring rows swing with a phase lag around 0.33 periods. By using an improved phase average method, phase averaged turbulent statistics and instantaneous coherent structures are obtained. The main flow region swings with vortex shedding. The region with larger 〈u′u′〉 (u′, fluctuating component of stream wise velocity) mainly locates at the shear layer, swinging with the vortex shedding. The region with larger 〈v′v′〉, (v′, fluctuating component of transverse velocity) mainly locates in front of the tubes, where transverse flow sweeps the upwind side of the tubes.

Design high-performance AZ31 ultrathin strip through multi-pass electroplastic rolling without off-line annealing

The influence of the electropulsing parameters including the current density and the frequency, on the rolling force, the microstructure and the mechanical properties of AZ31 strips processed by electroplastic rolling (EPR) were investigated in this study. On the basis, the double grain refinement mechanism, combing the rapid completed static recrystallization refinement (SRX) of AZ31 strip before the roll with the subsequent dynamic recrystallization refinement (DRX) of AZ31 strips at the deformed zone, was put forward in the whole process of EPR. According to the mechanism of double grain refinement, an innovative method of the production of AZ31 ultrathin strip with excellent comprehensive properties is established and verified. The AZ31 ultrathin strip with the thickness of 0.35 mm was obtained at the optimal electropulsing parameters, and the total reduction of 69% can be obtained though only 2 continuous passes without any off-line intermediate heat treatment in the process of EPR; besides, the maximum rolling temperature does not exceed 483 K. It is indicated that the technology of EPR with the high current density of the electropulsing is one of the most potential method to improve the plastic formability of hardly-deformed metals.

Effects of Heat Treatment on the Microstructure and Properties of a Cast Nickel-Based High-Cr Superalloy

The effect of solution treatment and intermediate heat treatment on the microstructure and properties of a new cast nickel-based high-Cr superalloy was investigated in this paper. The results indicate that the tensile strength and elongation at 900 °C increase when the solution temperature increases from 1160 °C to 1180 °C and then decrease when the solution temperature changes from 1180 °C to 1200 °C and 1220 °C. The stress rupture test results of the high-Cr superalloy under conditions of 900 °C/275 MPa shows that the rupture time, elongation, and reduction of area initially increased and then decreased with the increase in solution treatment temperatures. The results of stress rupture tests for the alloy after intermediate heat treatment followed by furnace-cooling, air-cooling, and water-cooling show that the morphology and distribution of γ’ phase have a great influence on the tensile test results at 900 °C of the alloy but no obvious influence on the test at 900 °C/275 MPa. The microstructure analysis of the superalloy after heat treatment shows that: when the solution treatment temperatures are at 1200 °C and 1220 °C, the incipient melting appears in the interdendritic region, which can severely deteriorate mechanical properties; the morphology of γ′ phase changes gradually from cube to spherical; and a large number of fine γ’ phase precipitates in the γ channel are found with increasing cooling rate after intermediate heat treatment.

Design Features and Simulation of the New-Build HELOKA-US Facility for the Validation of the DEMO Helium-Cooled Pebble Bed Intermediate Heat Transport and Storage System

For the EU-DEMO Helium-Cooled Pebble Bed (HCPB) concept, an indirect coupled design (ICD) with a molten salt (MS) loop as an intermediate heat transport and storage system (IHTS) is considered for the conceptual design phase. The IHTS with an energy storage decouples the primary heat transport system (PHTS) that undergoes pulse and dwell power cycles from the power conversion system (PCS), and thus can provide stable power to the turbine and grid. However, the maintenance of stable He and MS parameters during transitions from dwell to pulse and vice versa is challenging for the design of the MS loop, and the real performance of the helium–MS heat exchanger (He/MS HX) shall be verified. To investigate such components and conditions, a new R&amp;D infrastructure HELOKA-US (Helium Loop Karlsruhe—Upgrade Storage) is under construction for the validation of prototypical components and the MS loop operation under stationary and transitional conditions. This paper provides the design features of Phase 1a of the project and the simulation results with EBSILON on the power generation phase.

Study on corrosion behavior of two superalloys under two extreme atmospheres

Inconel 617 and Hastelloy X alloys are two candidate materials for very high temperature gas-cooled reactor (VHTR) intermediate heat exchanger and steam generator equipment. This work explored the corrosion behavior of two alloys in the atmosphere of extreme air ingress accidents and vacuum environment. After the experiment, the corrosion behaviors of the two alloys were characterized and analyzed by electronic balance, scanning electron microscope(SEM), energy dispersive spectroscopy(EDS) and X-ray diffraction(XRD) and carbon sulfur analyzer. The results showed that the mass change and oxide film thickness of Hastelloy X alloy and Inconel 617 alloy after corrosion in air met the oxidation parabola law, and the kp of Hastelloy is lower. The chromium migration of the two alloys was obvious after corrosion in air. The longer the corrosion time was, the more obvious the phenomenon was. The carbon content of the alloy did not change significantly with the corrosion time. Mass loss and decarburization occurred in both alloys after corrosion in vacuum, and volatile elements volatilized and migrated. The weight loss, decarburization and element volatilization of Hastelloy X were more obvious.

Corner coil heating mode improves the matrix uniformity of cooked rice in an induction heating cooker.

Nowadays, an increasing number of people worldwide use induction heating cookers to cook rice for consumption. This work reveals the influence of induction heating cooker heating modes on the quality attributes of cooked rice. Three heating modes, including bottom coil heating mode (mode 1), corner coil heating mode (mode 2), and side coil heating (mode 3), were used. Among the three modes, mode 2 allowed for an intermediate heating rate during rice cooking. For mode 2, the minimized temperature difference between the upper layer (including the central upper layer and peripheral upper layer) and the lower layer (including the central lower layer and peripheral lower layer) can reduce the effect of water absorption time difference on rice quality. Consequently, the rice cooked using mode 2 exhibited improved matrix uniformity, as indicated by the similar moisture content (59.92-61.89%), hardness (15.87-18.24 N), and water mobility (the relaxation time and peak area of the third relaxation peak) of rice samples at four different positions in the pot. The rice cooked by mode 2 showed better texture appearance and a more uniform porous microstructure. Consistently, the cooked rice samples by mode 2 at different positions did not show substantial differences in their starch digestion features.

Numerical study on the heat transfer characteristics of a liquid lead–bismuth eutectic in a D-type channel

A printed circuit heat exchanger (PCHE) can offer superior performance in area concentration and heat transfer efficiency. A PCHE with a liquid lead–bismuth eutectic (LBE) and supercritical carbon dioxide as working media can use these materials as intermediate heat exchangers in lead–bismuth eutectic-cooled reactors to reduce facility size and improve economy. To ensure the reliability of a numerical simulation for a liquid LBE in PCHE channels, the flow and heat transfer characteristics of a liquid LBE were investigated in a single D-type channel. The existing turbulent Prandtl number (Prt) models and the shear‒stress transport (SST) k−ω model were evaluated first by using experimental liquid metal data. Then, a suitable Prt model was proposed for the numerical simulation of the liquid LBE. Finally, the flow and heat transfer characteristics of the liquid LBE were studied in D-type straight channels and D-type zigzag channels. The study presented the effects of flow velocity, wall heat flux, equivalent diameter and zigzag channel angle on the flow resistance and heat transfer characteristics. Meanwhile, a heat transfer correlation suitable for a D-type straight channel was also proposed. The research results in this paper lay a good foundation for the development of PCHEs with an LBE as the working fluid.

Influence of Hot Band Annealing on Cold-Rolled Microstructure and Recrystallization in AA 6016

The influence of an intermediate heat treatment at the end of hot rolling and before cold rolling on Cube texture formation during the final solution annealing of AA 6016 is investigated. Three hot bands with different initial grain sizes and textures are considered: the first one without annealing before cold rolling, while the other two hot bands are heat treated at 540 °C for 1 hour in air before being cold rolled. One of the heat-treated hot bands was left to cool down in air and the other inside the furnace. Electron-backscatter diffraction (EBSD) maps of the cold-rolled specimens and crystal plasticity simulations show no difference in the amount of Cube remaining in the microstructure at the end of cold rolling for all three specimens. The initial grain size of the hot band has no influence on the Cube texture fraction left in the microstructure at the end of cold rolling for thickness reductions higher than 65 pct. Nevertheless, the grain size of the hot band affects the shape and distribution of the Cube grains left in the microstructure and the kernel average misorientation in the cold-rolled specimens. Moreover, the heat treatment decreases the intensity of the beta fiber components (Brass, Copper, and S) in the hot band and promotes the formation of a cold-rolled microstructure with a low kernel average misorientation. Both these factors lower the probability of preferential Cube nucleation during solution annealing and keep the Cube volume fraction after recrystallization below 10 pct, while it reaches 25 pct without intermediate annealing.

Advanced exergy analysis of NH3/CO2 cascade refrigeration system with ejector

Aiming at the NH3/CO2 Cascade Refrigeration System with ejector (CRSE), this paper establishes the mathematical model of the refrigeration cycle and compares it with the literature based on thermodynamic analysis. Advanced exergy analysis on the CRSE is carried out and the exergy destruction of components in the system are divided into two ways: avoidable/unavoidable exergy destruction and endogenous/exogenous exergy destruction, and combine the two ways to clarify the types and values of exergy destruction in components, which provides a direction for the improvement of the system. The analysis shows that the avoidable exergy destruction of the system accounts for 38.674% of the total exergy destruction, and the proportion of endogenous exergy destruction and exogenous exergy destruction in the total exergy destruction of the system is 77.772% and 22.228% respectively. The improvement potential of the system is very high, and the low-temperature compressor, condenser, and intermediate heat exchanger should be paid special attention to in the improvement.

A nuclear driven hybrid sCO2 power cycle/ membrane distillation system for water-electricity cogeneration

By integrating a membrane distillation (MD) block with a nuclear driven supercritical CO2 (sCO2) power block, a novel water and electricity cogeneration system is proposed, aiming at the water and energy supply for remote islands and coastal households. MD uses the waste heat from the sCO2 power block through an intermediate heat exchanger (IHX), while the exhaust low-pressure sCO2 flow leaving from the low temperature recuperator (LTR) is cooled by the seawater introduced into MD, without influencing the efficiency of power block. Steady state thermodynamic and economic analysis for the subsystems and the hybrid system are carried out by considering the effects of operation conditions and membrane properties. As the optimal performance of each single subsystem does not always correspond to the optimal performance of the cogeneration system, optimization genetic algorithm is employed to obtain the solutions to optimal block performance and optimal cogeneration system performance, respectively. The results predict that the maximum energy efficiency of the power block and the desalination block is 48.18% and 37.10%, respectively. The minimum levelized cost of electricity (LCOE) and levelized cost of water (LCOW) are 0.0527 $/kWh and 0.445 $/m3, respectively. The maximum exergy efficiency of the hybrid system is 67.82%. The nuclear driven sCO2-MD system is proved to be an effective layout to enhance the nuclear energy conversion efficiency and reduce water and electricity generation costs.

Electrode Layout Optimization and Numerical Simulation of Cast Conductive Asphalt Concrete Steel Bridge Deck Pavement.

In order to obtain the optimal electrode layout and ice melting effect of cast conductive asphalt concrete steel bridge deck pavement, firstly, pouring conductive asphalt concrete was prepared; secondly, different electrode materials and layout methods were selected to test the heating rate of the specimen from start to 120 min, and the electrode materials and layout methods were optimized. Then, the finite element analysis software ANSYS was used to build the model for heating and ice melting simulation, and the indoor test was used to further verify the ice melting effect of the cast conductive asphalt coagulation with or without the insulation layer. Finally, the thermal-structural coupling analysis of cast conductive asphalt concrete steel bridge deck pavement was carried out using ANSYS finite element software. The results showed that the stainless steel electrode material had the best heating effect, and the electrode thickness in the range of 0.1~3mm had no effect on the heating effect. The intermediate heating rate of the upper surface of the stainless steel sheet electrode cast conductive asphalt concrete in the left and right external electrodes was 8 °C/h, while the intermediate heating rate of the upper surface of the stainless steel mesh electrode cast conductive asphalt concrete was 12.9 °C/h. The layout of the left and right buried stainless steel metal mesh was able to effectively improve the snow melting efficiency; ANSYS finite element ice melting simulation was used to obtain the variation law of ice melting efficiency and a temperature field of cast conductive asphalt concrete. The indoor ice melting test showed that when melting the same thickness ice layer at 50 V voltage, it took 240 min with an insulation layer and 720 min without an insulation layer, which was three times that of the ice with an insulation layer, which further verifies the superiority of its ice melting effect. The most unfavorable load position of pavement under load and temperature field was determined. The maximum tensile stress and compressive stress of the pavement surface were transverse, and the maximum shear stress of the pavement bottom was transverse.

Impact of an internal heat exchanger on a transcritical CO2 heat pump under optimal pressure conditions

Transcritical R744 (CO2) heat pumps are a low-GWP high-efficiency alternative for domestic hot water generation and space heating. For high set-point temperatures, however, the COP drops and the optimum operating pressure increases. For this reason, the effect on system performance achieved by the inclusion of an Intermediate Heat Exchanger (IHX) is analyzed in depth. This is carried out by means of a numerical-experimental approach in which the effectiveness of the IHX and other characteristic parameters of the heat pump cycle are studied as a function of the IHX heat transfer area. The numerical modeling of the heat pump components is implemented for transient simulations of system heating-up process. Experimental tests with and without IHX are carried out with a water-to-water heat pump that feeds an accumulator tank, to assess its influence on the system’s COP and the electrical consumption. Simulations reveal that improving the efficiency of the IHX, by increasing the exchange area, improves the system’s performance. For the cases with higher IHX exchange area, the optimum pressure in the system is lower. For the heating experiments, the resulting thermodynamic COP is 7.55 % higher in the case with IHX, while the effective COP increases by 4.26 %. In consequence, the use of the IHX is recommended for the conditions analyzed.

Study on thermal deformation of hybrid printed circuit heat exchanger for advanced nuclear reactor

The intermediate heat exchanger (IHX) is one of the key components in advanced nuclear reactor power generation system. Printed circuit heat exchanger (PCHE) with mini-channels is a good candidate for the IHX. But the whole PCHE with tens of thousands of mini-channels is hard to be modeled and calculated at high temperature. Thus, the homogenization method, which can calculate the thermal deformation of the whole hybrid mini-channel PCHE, is conducted in this study and both the elastic and elastic-plastic finite element analysis methods are used. Here, the performance of the PCHE is assumed to be isotropic in the simulation. The results show that the macroscopic thermal deformation of the whole PCHE follows a gradually downward trend from hot side to cold side, while obvious thermal stress concentration is observed around the junctions between the PCHE core and cover plate. The stress and strain calculated by elastic and elastic-plastic methods under different constraints show quite different patterns. For the thermal deformation analysis of PCHE under weak constraint or small temperature difference conditions, the stress and strain results by elastic analysis and elastic-plastic analysis are similar so that the elastic analysis can be used. Under the strong condition, the stress of PCHE calculated by elastic analysis is much higher than that of elastic-plastic analysis, while the strain is lower than that of elastic-plastic analysis. The relative deviations of stress are 100.883% and 120.786% along path 1 and path 2 respectively. And the relative deviations of strain are 6.987% and 10.139% along path 1 and path 2 respectively. The elastic-plastic analysis should be used instead of the elastic analysis.