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The heat transfer tube is one of the key components affecting the heat transfer performance of automobile radiators. Proposes a new kind of heat transfer tube with ellipsoidal dimples based on the elliptical heat transfer tube. The effects of the arrangement and pitch ellipsoidal dimples on the turbulent heat transfer and flow resistance of the heat transfer tube are further studied by numerical simulation in the range of Reynolds number in 4080-24480. The results show that the ellipsoid dimple arrangement makes the near-wall fluid produce different flow forms, which enhances the turbulence degree of the tube fluid and thus improves the convective heat transfer capacity of the tube. Among them: vertical parallel arrangement (Case 1) causes convergent flow, oblique parallel arrangement (Case 2) causes helical flow, and diagonal symmetrical arrangement (Case 3) causes cross-helical flow. The cross-helical flow causes the most significant degree of turbulence, followed by the helical flow. Furthermore, the arrangement and pitch of the ellipsoidal dimples also have an essential influence on the heat transfer performance and flow resistance of the heat transfer tube. The Nusselt number and friction factor of Cases 1-3 increase successively. But the Nusselt number and friction factor gradually decrease with the rise of the pitch of ellipsoidal dimples. However, under different ellipsoidal dimples pitch, the comprehensive performance of Cases 1-3 is better than that of smooth elliptical tubes. Among them, Case 3 has the best performance when P = 15 mm, and the performance evaluation criteria value is up to 1.39. [ABSTRACT FROM AUTHOR]

Alloy 690 is a material commonly used in heat transfer tubes of steam generators (SGTs). The electrochemical corrosion behavior in different volumes (V) of NaCl–Na2S2O3 solution for different surface roughness (Ra) of alloy 690 was studied, and a BPNN model for predicting electrochemical corrosion parameters of alloy 690 was established (CP and CCD). The results show that Ra on the surface of alloy 690 destroys the passivation film and changes the oxygen vacancies in the passivation film, so that Cl− is more easily attached to the passivation film. Finally, accelerated electrochemical reactions on the surface of SGTs. When the solution is Na2S2O3, with the increase of Ra on the metal surface (0.0977≤ Ra ≤ 1.1661), the corrosion potential gradually decreases. BPNN can accurately predict the electrochemical corrosion rate of alloy 690 under different conditions, and the relative error is less than 10%. In this paper, an artificial intelligence model is established for the first time to predict the relationship between Ra and electrochemical corrosion, and the conclusion can be used to schedule the maintenance process of the SG, thereby reducing the risk of structural failure and maintenance costs.

Corrugation parameter design seeks to maximize the thermal-hydraulic comprehensive performance (THCP) of corrugated tubes as much as possible. Among them, composite corrugations composed of simple corrugations are proposed to strengthen the THCP of corrugated pipes. However, the rule and mechanism regarding the impact of composite corrugations on the THCP of corrugated tubes, particularly when those composite corrugations are composed of simple asymmetric corrugations, are not well understood. Therefore, in this work, the effect of composite corrugations consisting of two simple droplet-shaped corrugations on THCP is assessed numerically, where the first composite corrugation is concave-convex (CTCC1) and the second composite corrugation is concave-concave (CTCC2). In addition, the effect of traditional corrugation (CTSC) on THCP is also examined to further highlight the advantages of composite corrugation in enhancing the THCP of corrugated tubes. The results of the study indicated a 49 %, 55 %, and 61 % increase in THCP at a Reynolds number (Re) of 5000 for CTSC , CTCC1 , and CTCC2 , respectively, compared to a smooth tube, indicating that the combination of composite corrugations in CTCC2 is superior to that in CTCC1. In addition, a smaller corrugation width on the upstream side of CTCC2 is more conducive to enhancing THCP. Furthermore, it should be ensured that the corrugation depth on the upstream side of CTCC2 is not greater than the depth on the downstream side to achieve better THCP. The work confirms the advantages of composite corrugations over traditional corrugations in enhancing THCP and guides the selection of composite corrugation combination forms and the design of composite corrugation width and depth distribution. [ABSTRACT FROM AUTHOR]

The study aims to improve the performance of the thermal power generation system in power plants by analyzing its working principle. The thermal power generation system of large power plants is taken as the research object. The Fluent software is used for simulation experiments. A new optimization method of the rotor structure in the electronic heat absorption equipment and heat exchange pipeline is proposed. By improving the rotor, the heat transfer efficiency of the heat exchange pipeline is greatly improved. Through the relevant research on the thermal power generation system, the rotor's heat transfer performance of the exchange tube is analyzed based on the strong heat transfer convection mechanism. Then the simulation experiment is carried out. Based on the heat transfer mechanism of the combined rotor in the tube path unit, the heat transfer pipe is optimized. The numerical simulation results of rotor heat transfer and fluid flow show that the average resource utilization rate increases with time. The average resource utilization efficiency of the system reaches more than 70% in 45 ms. When the pipe size is 100 mm, the performance of the resistance coefficient is 3.6 before improvement and 2.8 after improvement. When iteration times are 200, the rotor heat transfer of four kinds of pipes reaches the maximum, and the rotor heat transfer of No. 1 pipe with the size of 22 mm can reach 10000W. The research demonstrates the superiority of the proposed heat exchange tube, which provides a theoretical reference for optimizing the heat transfer tube and the efficiency of the thermal power generation system. [ABSTRACT FROM AUTHOR]

[Display omitted] • A Tube-to-Tube sliding wear test rig is developed. • Sliding wear volume of Inconel 690 tube increases with increasing cycle number. • Sliding wear volume of Inconel 690 tube is larger under larger contact force. • Wear volume is smaller under lubrication of water, especially at beginning. • Water reduces oxidative wear due to lower oxygen concentration. A Tube-to-Tube sliding wear test rig was developed in the current work. The reciprocating sliding wear behaviors on Inconel 690 heat transfer tubes were experimentally studied under various conditions. The sliding amplitude and frequency have little influence on wear, and the wear volume is in general positively proportional to the sliding cycle number and the contact force. Therefore, the Archard wear equation can be adopted to calculate the macroscale wear volume of the heat transfer tubes. Based on the results obtained by optical microscopy and scanning electron microscopy, the main wear mechanisms of the tube are the adhesive wear, abrasive wear and oxidative wear. Under the water environment, the wear rate is evidently lower than that of the dry condition and the wear mechanisms were not altered. [ABSTRACT FROM AUTHOR]

• SiO 2 particles extended the induction period of the combined fouling. • SiO 2 particles increased the asymptotic fouling resistance of combined fouling. • For combined fouling, plain tube had a longer induction period than enhanced tubes. • The variation profile of the accelerated combined fouling after scaling down is similar to that in a real system. This study investigated the interaction between particulate fouling and precipitation fouling on two different enhanced tubes and a plain tube in a shell-and-tube condenser. Three kinds of fouling, including particulate fouling, precipitation fouling, and combined fouling, were measured continuously for more than 720 h in three individual tests, respectively. For the particulate fouling, three tubes suffered a similar fouling process. The asymptotic fouling resistance of the precipitation fouling on enhanced tubes was lower than on the plain tube. However, for the combined fouling, the enhanced tube with a larger start number experienced the greatest fouling. On the same tube, the asymptotic fouling resistances ranked from least to greatest in the following order: particulate fouling, precipitation fouling, combined fouling; and the durations of the induction period ranked as: particulate fouling, precipitation fouling, combined fouling. As for the combined fouling existent in real cooling water systems, the fouling induction period on the plain tube was longer than that of enhanced tubes. Compared with the particulate fouling (SiO 2) and precipitation fouling (CaCO 3), which had a high bond strength on the tube surface, the combined fouling was soft and easily removed by flow erosion or collision with big particles during the induction period. This indicated that particles mixed in the water could extend the induction period of combined fouling. However, once the combined fouling started to grow, these particles sticking on the heat transfer surface provided nucleation sites for the crystallization process and, thus, increased the fouling thermal resistance significantly. In addition, the results indicated that the variation profile of the accelerated combined fouling after scaling down is similar to the fouling process in a real system. [ABSTRACT FROM AUTHOR]

• An energy balance-based distributed parameter model for SCV was proposed. • Thermal performance of SCV at supercritical pressure is estimated. • Effects of operating parameters on thermal performance are discussed. • Effects of wire coil or twisted tape inserts on thermal performance are studied. In this paper, an energy balance-based model considering icing effects was established for estimating the heat transfer of submerged combustion vaporizer (SCV) under supercritical LNG pressure, where introduces some empirical correlations to evaluate the convection heat transfer of water bath-side and LNG-side. Based on this model, the thermal performance of a typical SCV was predicted numerically, and good agreement between the predicted and actual water bath temperatures indicates that the model is reliable. The results indicated that the operation parameters, such as LNG pressure, operating load, inlet LNG temperature, have significantly different influences on the thermal performance of SCV, including required minimum water bath temperature and flue gas flow rate, and the length and average thickness of ice layer outside the LNG tube bundle. The heat transfer enhancement techniques can improve the heat transfer efficiency markedly, although they also cause an increase in flow resistance. The wire coil insert with a helix angle of 75° is a better choice than the twisted tape insert with a helix angle of 45° and the wire coil insert with a helix angle of 45° considering its effects on both heat transfer and flow resistance. [ABSTRACT FROM AUTHOR]

In this paper, a new method and manufacture apparatus for producing enhanced tube with dimples and protrusions (ETDP) have been proposed for the first time. The main objective of the present work is to investigate the mechanical responses of the smooth tube in extruding process. Additionally, the effects of extrusion depth, extrusion spacing, teeth radius, and tube wall thickness on deformation, stress, plastic strain, and extrusion force of ETDP were also investigated. From this investigation, it found that the dimples formed due to the smooth tube protruded, and protrusions formed due to the smooth tube dented. The maximum deformation, stress, and plastic strain at protrusion regions are larger than dimples. Among the investigated different extruding parameters, it found that the stress, deformation, and plastic strain increase with the increasing of D and δ. However, it increases with the decreases of extrusion P. In addition, R has no obvious effect on mechanical behavior of ETDP at current arrangement. The results can help to understand the forming process parameters and improve the forming quality. [ABSTRACT FROM AUTHOR]

In the heat exchangers of sodium-cooled fast reactors, sodium flow can cause the tubes to vibrate, resulting in fretting wear damage due to the contact between the tubes (2.25Cr-1Mo steel) and their support plate (Gr5C12 alloy). In this work, the effects of temperature on the fretting wear behavior of a 2.25Cr-1Mo heat transfer tube on a Gr5C12 alloy rod were studied. The results showed that the coefficient of friction (COF) and wear volume increased first and then decreased with the increase in temperature. Moreover, 2.25Cr-1Mo showed great wear performance at high temperatures than at room temperature and 80 °C, because of the antifriction nature of the oxidative layer and the high hardness of the tribological transformed structure layer. As the temperature increased, material transfer and plastic deformation became increasingly obvious, but average wear depth decreased. This provides data support for the practical engineering application of 2.25Cr-1Mo steel at elevated temperatures. Wear mechanisms were found to depend modestly on temperature and largely on normal load. As temperature increases, the wear mechanism gradually changes from abrasive wear to adhesive wear.

Fouling deposit is a common issue on the heat transfer surface caused by the impurity of working water. Many researchers conducted experimental test to study the relationship between the fouling thermal resistance and operating parameters, such as water quality, tube geometry, and liquid velocity, targeting at developing the accurate correlation of fouling thermal resistance on heat transfer tubes. The accurate test of fouling thermal resistance is critical for investigators. In fouling test, with the fouling deposit on the internal surface, both the liquid (water) velocity through the tube and the heat flux of the test tube deviated automatically. Although testers usually tried to adjust the water velocity and heat flux back to the original point, it is hard to be realized, thus the water velocity and heat flux deviated somehow inevitably. In fact, the variations of water velocity and heat flux would cause the change of overall thermal resistance of test tubes, which should be separated from the change caused by fouling deposit. This process could be named as “decoupling”. This paper analyzed the effect of deviations of water velocity and heat flux on the test results of fouling resistance quantitatively based on experimental test, and a decoupling method and formulas were developed. One set of accelerated fouling test was conducted and result shows the fouling resistance with decoupling and non-decoupling had a maximum difference of 0.000002124 m 2  K/W for tube 1, and 0.000002363 m 2  K/W for Tube 2, 0.000001316 m 2  K/W for tube 3. [ABSTRACT FROM AUTHOR]

As fourth-generation nuclear power equipment, high-temperature gas-cooled reactor (HTGR) is attracting more and more attention both in industry and academia. The core outlet temperature of the steam generator (SG) in HTGR is much higher than that of pressurized water reactor steam generators, which is more likely to cause damage. Till now, welding plugging is still one of the important means to prevent the leakage of damaged heat transfer tubes. However, how to improve the automation of welding plugging to reduce the short-range operation time in a radioactive environment is still difficult. This work proposes the design of a laser welding plugging system for the HTGR. Firstly, the design requirements are analyzed and the overall design scheme is given. The whole system consists of a laser generator, a multi-axis robot, and supporting devices. Secondly, the key supporting devices including a laser welding head, a pneumatic clamping jaw, and a single-axis motion platform are explained in detail. The structure simulation based on SolidWorks is adopted, which provides the basis for the design of the single-axis motion platform. Thirdly, the control system which takes the PLC control system as the main control unit and the industrial computer as the monitoring data processing unit is described. Finally, an experimental system is built and the laser welding experiment is carried out to test the feasibility of the designed laser welding plugging system. • A novel laser welding plugging system is designed to improve the automation level of welding plugging. • The plugging system is applicable to the narrow and long manhole structure in the steam generator. • The width and depth of the weld proves the feasibility of the laser welding system. [ABSTRACT FROM AUTHOR]

Super open rack vaporizer (SuperORV) is a new-type of liquefied natural gas (LNG) vaporizer whose lower half of heat transfer tubes has double tube structure. A distributed parameter model based on energy balance is developed in the present paper with the aim to simulate the thermal performance of SuperORV heat transfer tube at supercritical pressure. Corresponding empirical correlations are used to evaluate the convection heat transfer of LNG and seawater, and the heat transfer enhancement effects of inner fin and twisted tape insert are considered in computation. Good agreement between calculated and experimental data implies the calculation model is reliable. On this basis, the temperature and ice thickness profiles along the heat transfer tube are obtained by numerical solution with or without ice layer presence, the thermal performance of heat transfer tube is analyzed, and the effects of operating parameters and heat transfer enhancement techniques on the thermal performance are discussed. The results indicate that both the operating parameters and the heat transfer enhancement techniques have great influence on the thermal performance, including required minimum tube length, ice thickness and length of formed ice layer. The heat transfer enhancement techniques can improve the heat transfer performance markedly, and the required tube length is reduced by 47.7% while both inner fin and twisted tape insert are applied. [ABSTRACT FROM AUTHOR]

This research related to the development of ultra-small inner spiral ribbed copper tubes (ISRCTs) which have high quality and efficiency in transferring heat. The deformation behaviour of the ISRCT was studied. Three-dimensional finite element models were constructed for the various process parameters: the change of the cross-section profiles of the ribbed contours and the spiral angle of the ribbed area of the ISRCT, for twelve multi-pass drawings through the die using the tube sinking method. The effect of the ribbed spiral angle and the ribbed cross-sectional profile was also studied. Modelling and simulation techniques were performed using commercial Abaqus software to learn whether the surface profiles of the ISRCT increased or reduced with tube sinking using the finite element method (FEM). Results of the multi-pass drawing analysis were summarised and compared to the experimental findings. The FEM simulation approach was used to analyse the changes of ten parameters: von Mises stress, wall thickness, ribbed base width, ribbed tip width, ribbed base gap, ribbed tip gap, ribbed height, ribbed pitch, axial displacement and ribbed spiral angle. This procedure can be used to improve product quality and to study the effect of the various parameters. The results will be very valuable for researchers and well engineers for future design of ultra-small ISRCT to improve the quality and efficiency of heat transfer. [ABSTRACT FROM AUTHOR]

This research was about the development of ultra-small inner spiral ribbed copper tube (ISRCT) with high-quality heat transfer. The production of ISRCT involved various features, such as small size and high functionality which lowered manufacturing cost. Experimental results revealed the significant parameters and the cross-sectional profile of the ISRCT after tube sinking. These were used to indicate and predict the total reduction of area as a percentage (Rt%) and determine the success of the manufacturing process. This analysis determined the optimal process parameters for the ISRCT using the tube sinking method and the effects of the ribbed dimension to attain the maximum Rt% such as the ratio of drawing stress to yield stress ( σ/ σ), the ratio of the wall thickness and the ribbed height to the diameter [( t + h)/ D], the ratio of the ribbed base width and the ratio of the ribbed base circumference to the total number of ribs inside the tube [ w/( πd/ n)], the ratio of the ribbed tip width and the ratio of ribbed tip circumference to the total number of tube ribs [ w/( πd/ n)] and the ribbed spiral angle ( ψ). The optimal Rt% of these five parameters was compared. From the results, the optimum Rt% on the method of the tube sinking process with ISRCT must not exceed 57 %, and the size of the ISRCT has to be precise with a gap between the ribbed base and the ribbed tip; the angle of the ribbed spiral must not be zero. The conclusions are that the optimal Rt% used in the manufacture of ISRCT is suggested to be lower than 57 %. [ABSTRACT FROM AUTHOR]

This paper is concerned with the development of ultra-small inner spiral ribbed copper tubes with high-quality heat transfer. Since the demand for the ultra-small tubes in electrical appliances is currently high and will be greater in the future, the technology employed must enable the production of inner spiral ribbed fine tubes with various features, such as small size, high quality, high functionality, and low processing cost so as to meet the increasing demand. The conventional production method is suitable for large tubes with high drawability but is unsuitable for fabrication of long ultra-small tubes because of the difficulty to manufacture both an ultra-small spiral ribbed mandrel and a floating plug. This research paper has proposed four drawing methods as follows: tube sinking, water, oil, and wax as mandrels and presented the comparison of seven parameters, i.e., drawing stress ratio, wall thickness ratio, ribbed base width ratio, ribbed tip width ratio, ribbed height ratio, ribbed pitch ratio, and ribbed spiral angle ratio. It was found that tube sinking was unfit for making the ultra-small inner spiral ribbed copper tubes due to the resulting high ratio of wall thickness. The results of all the parameters were similar in the cases of oil and wax. Despite less impressive outcomes, water was easily removed from the inner spiral ribbed copper tube compared to oil and wax. Thus, the tube drawing using water as mandrel was most suitable for the production of the inner spiral ribbed copper tube. [ABSTRACT FROM AUTHOR]

Steam generator is one of enormous heat exchangers that use heat energy derived from a reactor of nuclear power plant for generating steam. The steam obtained is drained into a turbine, and plays an important role for power generation. The heat transfer tubes of each steam generator used in a pressurized water reactor (PWR) are composed of about 8,000 ∼ 13,000 U-shaped tubes. These tubes act as the structural material and the thermal boundary. Furthermore, these tubes account for about 70% of the cooling surface area, transmitting thermal energy between the high-temperature (about 320°C), high-pressure (about 157 Kg/cm) primary coolant derived from the reactor and the secondary coolant, which is at about 220°C and 60 Kg/cm, from the secondary system. These heat transfer tubes used in the steam generator within the PWR were fabricated from seamless tubes of stainless steel (SUS304L), Alloy 600 and Alloy690. In this study, numerical and experimental investigations are carried out on the U-bending process for fabricating heat transfer tubes from long straight SUS304L tubes. In the numerical simulation, 3-dimensional finite element analysis is performed using ABAQUS Explicit/Implicit. In detail, process parameters such as the angular speed, U-bending period, and bending angle taking into account elastic recovery after cold U-bending are considered. Additionally, experimental investigations are conducted to verify the suitability of the predicted U-shaped geometries in terms of the ovality and wall thickness of the U-shaped heat transfer tubes. [ABSTRACT FROM AUTHOR]

In order to improve the thermal shock resistance of solar thermal heat transfer tube material, the mullite-cordierite composite ceramic as solar thermal heat transfer tube material were fabricated by pressureless sintering using α-AlO, Suzhou kaolin, talc, and feldspar as starting materials. The important parameter for solar thermal transfer tube such as water absorption ( W), bulk density ( D), and the mechanical properties were investigated. The phase composition and microstructure of the composite ceramics were analyzed by XRD and SEM. The experimental results show that the B3 sintered at 1 300 °C and holding for 3 h has an optimum thermal shock resistance. The bending strength loss rate of B3 is only 2% at 1 100°C by air quenching-strength test and the sample can endure 30 times thermal shock cycling, and the water absorption the bulk density and bending strength are 0.32%, 2.58 g·cm, and 125.59 MPa respectively. The XRD analysis indicated that the phase compositions of the sample were mullite, cordierite, corundum, and spinel. The SEM images illustrate that the cordierite is prismatic grain and the mullite is nano rod, showing a good thermal shock resistance for composite ceramics as potential solar thermal power material. [ABSTRACT FROM AUTHOR]

The impact wear test of 2.25Cr–1Mo steel against Gr5C12 alloy was performed at a controlled kinetic energy impact wear rig. The effect of temperatures (from 25 °C to 450 °C) on the impact wear damage mechanism was investigated. The contact force, energy absorption, and interface deformation during the impact process were recorded and analyzed in real time. Wear volume, morphology, and elemental distribution of the wear scars were used to characterize wear and tribo-chemistry behavior. Results demonstrate that at varied temperatures, the interface behavior of 2.25Cr–1Mo steel is different. With the rise in temperature, both the contact force, absorption energy, and wear volume first increase and then decrease. The explanation is that higher temperatures can modify the material's surface properties. Delamination, plastic deformation, and oxidative wear are the major mechanisms of impact wear, but the proportions of the three wear mechanisms differ at varied temperature. • The impact wear behavior of 2.25Cr–1Mo steel at elevated temperature was investigated. • The interface behavior of impact wear was analyzed. • The impact wear mechanism of 2.25Cr–1Mo steel at elevated temperature was discussed. [ABSTRACT FROM AUTHOR]

In the heat exchangers of sodium-cooled fast reactors, sodium flow can cause the tubes to vibrate, resulting in fretting wear damage due to the contact between the tubes (2.25Cr-1Mo steel) and their support plate (Gr5C12 alloy). In this work, the effects of temperature on the fretting wear behavior of a 2.25Cr-1Mo heat transfer tube on a Gr5C12 alloy rod were studied. The results showed that the coefficient of friction (COF) and wear volume increased first and then decreased with the increase in temperature. Moreover, 2.25Cr-1Mo showed great wear performance at high temperatures than at room temperature and 80 °C, because of the antifriction nature of the oxidative layer and the high hardness of the tribological transformed structure layer. As the temperature increased, material transfer and plastic deformation became increasingly obvious, but average wear depth decreased. This provides data support for the practical engineering application of 2.25Cr-1Mo steel at elevated temperatures. Wear mechanisms were found to depend modestly on temperature and largely on normal load. As temperature increases, the wear mechanism gradually changes from abrasive wear to adhesive wear. [ABSTRACT FROM AUTHOR]

• A simulation model for water-to-water falling film evaporator was conducted. • The distribution of heat transfer coefficient along the tube is investigated. • There is an optimal liquid level existed for the best heat transfer capacity. • Design suggestions of the falling film evaporator in such conditions are proposed. • The boundary line between falling film and full liquid areas is obtained firstly. With the advantages of excellent heat transfer performance and less refrigerant charge, falling film evaporator has been widely used in seawater desalination and other industries. However, due to the practical problems of liquid level control and dry patches interactions, the structure design of falling film evaporator should be optimized for refrigeration applications. To resolve those problems, a simulation model for water-to-water falling film evaporator used in a water vapor heat pump system was conducted in this paper. Through the finite element method, the temperature distribution along the working tubes and the heat exchanger has been obtained. The distribution of heat transfer coefficient along the tube is also investigated to find out the best liquid level control solutions. For an available falling film evaporator with 4 pass working tubes under boiling temperature of 80 °C and spraying mass of 0.4 kg⋅s−1, it is suggested that 2 pass working tubes should be in falling film region in order to achieve the largest heating capacity. Most important of all, it is proposed that there is an optimal boundary line between full liquid and falling film region. It may provide some suggestions for future design of falling film evaporators. [ABSTRACT FROM AUTHOR]