Copper Tube Research Articles

Optimization of Copper Tube Configuration in Rectangular Billet Continuous Casting Mold

Optimization of Copper Tube Configuration in Rectangular Billet Continuous Casting Mold

Іmprovement of performance characteristics and increase of productivity in the production of rolled-welded steel pipes

Thin-sheet cold-rolled 08kp steel is widely used in the production of two-layer copper-plated rolled-soldered tubes by complex processes of cold deformation with metal extraction and subsequent soldering. Problem. For high-quality molding, steel must have high technological plasticity, which is ensured by recrystallization annealing of rolls of rolled steel in periodic garden hood furnaces. It is impossible to obtain a sheet with increased properties, to correct the lack of sheet blanks due to poor-quality deformation, to prevent the subsequent aging of steel over time by processing in hood furnaces. During the manufacture of tubes, annealing of blanks, forming and soldering are carried out in different workshops of the enterprise, which is definitely not economical. Goal. The aim of the work is to improve both the technological and service characteristics of 08kp steel, intended for the manufacture of rolled soldered tubes, and to ensure the possibility of combining all processes of their production in a single line. To achieve the goal, it is necessary to develop an optimal mode of high-speed weakening heat treatment of riveted rolled steel and to study the possibility of replacing soldering in a muffle furnace with high-speed induction soldering. Methodology. The cold-rolled strip was subjected to continuous annealing at 700 °C and subsequent aging at 400 °C for 2 minutes using contact heating (~100 °C/s) in an argon atmosphere. Inductive soldering rolled up copper tubes were made at 1150ºС and duration of heating up to 30 seconds. After soldering, the tube was cooled in a thermostat with argon to a temperature of 900 – 950ºС and subjected to tempering at 600 – 650ºС lasting up to 2 s to prevent deformation aging. Result. Two-stage high-speed heat treatment (recrystallization tempering and aging) guarantees 08kp steel a high level of properties for defect-free forming of small-diameter tubes. High-speed induction soldering allows you to combine all processes in one current line. Practical value. The unification of all tube manufacturing processes in one current line ensures the improvement of their quality, surface cleanliness, absence of aging, reduction of defects and increase of production productivity, reduction of transport costs of manual labor and the number of working personnel. Tubes manufactured using the developed technology passed 100% incoming inspection under production conditions.

Comprehensive Evaluation of the Performances of Heat Exchangers with Aluminum and Copper Finned Tubes

The finned-tube heat exchanger is the core part of an air conditioning system. Its heat exchange performance directly affects the energy consumption and efficiency of the air conditioner. The shortage and rising price of copper have led to increasing replacement of copper tubes with aluminum tubes in finned-tube heat exchangers. This paper studies two kinds of such heat exchangers, one consisting of copper tubes and aluminum fins and the other consisting of aluminum tubes and aluminum fins. The influences of the different base tube materials on heat transfer are compared and analyzed in terms of heat transfer strength and cost per unit heat transfer. The results show that the heat transfer and heat transfer coefficient increase with increasing inlet wind speed. Under different inlet wind speeds, the heat transfer and heat transfer coefficient of the finned-tube heat exchanger with aluminum tubes are 4%–12% and 7%%–9% lower than those of an identically structured heat exchanger with copper tubes, respectively. The aluminum-aluminum exchanger achieves 67% higher heat transfer than that of the copper-aluminum exchanger at only 8% of the cost. These results are significant for guiding the development and application of finned-tube heat exchangers.

Experimental and numerical analysis of an asphalt solar collector with a conductive asphalt mixture

Asphalt solar collectors (ASCs) have emerged as a promising renewable energy source. They offer a practical solution for generating renewable energy and thereby reduce the reliance on fossil fuels. In this study, a computational analysis and experimental validation of an ASC with a conductive asphalt mixture were conducted. The ASC that was investigated had 3000 mm long serpentine copper tubes positioned at the center of a 1000 mm ×60 mm ×8 mm sample of hot-mix asphalt. Ten 250 W infrared bulbs installed in two rows served as the simulated heat source of the ASC. The ASC had a water flow in the range of 14–97 L⁄h and solar intensities of 600, 800, and 1000W/m2. The thermal response of the ASC was modeled using the COMSOL Multiphysics 5.6.0.280 heat-transfer module. The experimental results indicted that the efficiency of the ASC was 53.56% or 64.1% with either reference or conductive mixtures, respectively. When a conductive mixture was used in the ASC, its surface temperature decreased by 11.37% when compared to that obtained using the reference mixture. The numerical simulation revealed that the average deviation between the numerical and experimental temperature data of the water that flowed within the ASC tubes was between 6% and 14%. The use of conductive asphalt mix would enhance the thermal performance of ASCs.

Freeze range of a condensing gas propagating in a liquid helium-cooled tube

Understanding air propagation and condensation following a catastrophic vacuum break in particle accelerator beamlines cooled by liquid helium is crucial for maintaining the operational safety of these facilities. Previous experimental investigations on nitrogen gas propagation in both normal liquid helium (He I) and superfluid helium (He II) cooled copper tubes unveiled a nearly exponential deceleration of the gas propagation. A comprehensive theoretical model incorporating gas dynamics, heat transfer, and condensation mechanisms has been developed, which effectively reproduces various key experimental observations. An intriguing phenomenon uncovered in our model simulation is that the gas propagation appears to nearly stop beyond a certain distance from the location where condensation starts. We refer to this distance as the freeze range. In this paper, we present our systematic study of the freeze range at various inlet mass fluxes and tube diameters. We show that the results can be well described by a simple correlation. The underlying physical mechanism that supports this useful correlation is explained. Knowing the freeze range may allow accelerator engineers to develop protocols for controlling frost-layer contamination in the beamline tubes, which is of great practical importance.

Enhanced pool boiling of refrigerants R-134a, R-1336mzz(Z) and R-1336mzz(E) on micro- and nanostructured tubes

Pool boiling of refrigerants is a primary heat transfer mode in flooded evaporators, as well as a promising solution in electronics cooling applications. In this work, the pool boiling performance of R-134a, R-1336mzz(E), and R-1336mzz(Z) on the external side of round tubes are reported and compared to Cooper's heat transfer coefficient (HTC) model. Modification of Cooper's correlation is found to be necessary for R-1336mzz(Z) at low reduced pressure. Micro- and nanostructured tubes are tested using the three different refrigerants and are shown to enhance the boiling HTC. Specifically, three various structures consisting of: boehmite (AlO(OH)) nanostructures, etched aluminum microstructures, and copper oxide (CuO) micro-nanostructures are fabricated on the external sides of aluminum and copper tubes. The surface structures have characteristic length scales of 100 nm, 1 µm, and 10 µm for boehmite, CuO, and etched aluminum, respectively. While the boiling HTC is enhanced up to 250% (compared to smooth tubes) using R-134a with etched aluminum, it shows a 15% decrease in HTC when boehmite structures are used. For CuO, higher heat fluxes showed a 25% HTC enhancement, while lower heat fluxes showed negligible effects when compared to smooth copper tubing. Different refrigerants showed various relations between structure and HTC enhancements. To take account of both structure length scale and refrigerant properties, we introduce a normalized structure size (Rn) and conclude that HTC enhancement ratio increases non-linearly with Rn. Our study not only provides valuable data on refrigerant pool boiling of recently developed low global warming potential and ozone depleting potential fluids, it also provides valuable design guidelines for the development and application of micro- and nanostructured surfaces in chiller and electronics cooling applications.

Experimental Analysis of Solar Parabolic Trough Collector for Novel Solar Cooking System in Gujarat, India

Indian villages use wood, cow-buffalo dung cakes, and agricultural waste for cooking, while urban areas use piped natural gas and LPG. Desertification and rising fuel prices require renewable energy sources like solar energy. Three types of solar cookers are used for cooking like: box, concentrator, and indirect. The box solar cooker, popular for over two centuries, uses solar radiation to generate heat energy for cooking food. It can be powered by reflector sheets and energy-storing materials, with a 35.3-21.7 % energy efficiency compared to a standard cooker with 27.6-16.9%. Direct solar cookers with parabolic reflectors concentrate reflected energy, suitable for direct or indirect cooking. In winter, a parabolic dish solar cooker cooks at a faster pace and higher temperatures. Moreover, the Parabolic Trough Collector offers a more practical cooking solution. This research work evaluates the efficiency of the Parabolic Trough Collector (PTC) in various real-world climatic conditions using locally available materials for reflector having 97 % of reflectivity and absorber tube made-up of copper tube covered with black colour sheet. Cooking system efficiency was tested, and the results ranged from 5 to 40%. Further, this study aims to identify an applied performance evaluation in Gujarat, India.

Optimized Design of Shell and Tube Heat Exchanger with Segmental Baffles

Heat exchangers are the apparatus which is widely used in various industries. They transmit heat among two or more fluid streams. Theoretical analysis done by Kern’s method has been done on Shell and tube heat exchanger with segmental baffle and then experimented in CFD to check Heat Transfer rate and pressure drop with varying number of baffles which is 6, 8 and 10, and by keeping all the rest of parameters constant. It is found that as the number of baffles increase heat transfer rate increases also pressure drop is increases significantly. To optimize model in next step, CFD analysis is has been done by varying baffle cut to 25%, 35% and 45% by keeping same number of baffles which found best in heat transfer rate in earlier Kern’s method. Other parameters like velocity, temperature, pressure and baffle numbers are kept constant. Results obtained from numerical solution are analysed extensively to get the effect of baffle cut on heat transfer rate and pressure drop on shell side. The pressing need of the heat exchanger industry, the tradeoff optimization between the pressure drop and the heat transfer coefficient has been studied to provide an idea to get effects of the change in two parameters, namely, baffle spacing and baffle cut simultaneously and observe how these two will affect the performance of an STHX. An attempt to find the optimum geometric configuration has been carried out with number of baffles. Increasing baffles for same length of shell and baffle cut increases from 25% to 35%, heat transfer rate increases. It is beneficial in elucidating that a higher heat transfer coefficient can be obtained for fewer baffles when coupled with the appropriate baffle cut. So selection of correct optimized shell and tube heat exchanger. The work is carried out for copper tube bundles and steel shell. So optimization of baffle cut with correct number of baffles and reduction in pressure drop studied with CFD tool.

The forward calorimeter of the ALICE experiment at CERN LHC

A new forward calorimeter (FoCal), covering the pseudorapidity range 3.4 ≤ η ≤ 5.8, is proposed in order to extend the physics reach of ALICE during the LHC Run 4. The FoCal comprises a high-granularity electromagnetic calorimeter with silicon pixel and pad readout as well as a hadronic calorimeter. FoCal gives access to the nuclear gluon densities down to Bjorken-x ∼ 10−6, where they are not constrained by other measurements and their evolution may be affected by non-linear effects of quantum chromodynamics. The hadronic subsystem of FoCal (FoCal-H) will be based on capillary copper tubes with scintillating fibers inside. A full-length prototype was assembled and it was exposed to a non-separated charged particle beam in the H2 SPS CERN beamline in November 2022. An energy scan from 60 to 350 GeV was performed and the reconstructed signals are processed in a custom developed ROOT based environment. The design of the 2022 prototype as well as the first results from the energy reconstruction are presented.

Hydraulic Expansion Joint Contact State of Heat Exchanger Based on New Contact Area Measurement Method

The contact state of a seamless internal threaded copper tube and an aluminium foil fin not only affects the heat transfer efficiency of a tube–fin heat exchanger but also seriously affects its service life. In this study, hydraulic expansion technology was used to connect the copper tube with an internal thread with a 7 mm diameter to the fin of the heat exchanger. The influence of the expansion pressure and pressure holding time on the contact state was analysed through experiments and finite element simulation, and the variation law of the two on the contact state was obtained. The contact state was characterised by the contact gap and contact area. In order to obtain the specific contact area value, a new method of measuring the contact area was developed to reveal the variation in contact area between the copper tube and the fin after expansion. The results show that the contact gap decreases with an increase in expansion pressure, while the pressure holding time remains the same. The contact area increases with an increase in expansion pressure, and the rate of increase slows. When the expansion pressure is 18 MPa, the average contact gap is approximately 0.018 mm. When the expansion pressure reaches 16 MPa, the contact area ratio is 91.0%. When the expansion pressure increases to 18 MPa, the contact area ratio only increases by approximately 0.6%. Compared with the influence of the expansion pressure on the increase in contact area, the influence of the pressure holding time on the contact area is lower.

A Comprehensive Study on the Effects of Surface Roughness on Power Consumption and Heat Transfer Performance in Novel In-Tube Condensation r123yf Refrigerant Systems

This study investigates the impact of surface roughness on the condensation Heat Transfer Coefficient (HTC) of R123yf refrigerant in a uniquely designed test rig with pre-condenser and post-condenser for quality regulation. In mining industries, the mining equipment consumes more amount to power for the Air Conditioning system. To reduce the power consumption of copper metal inside the surface morphology needs to be changed. Experiments were conducted in a 750 mm long, 8.4 mm internal diameter copper tube, with regard to mass flux varying from 150 kg.m-2.s-1 to 300 kg.m-2.s-1, refrigerant quality varying from 0.3 to 0.8, and saturated temperature from 35°C to 45°C. The impact of varying surface roughness (1.5 μm, 2.5μm, 3.4 μm, and 6.7 μm) on HTC was examined. The plane tube condensation experimental results agreed with M M Shah's heat transfer coefficient correlations, with a 20% absolute mean deviation. It was observed that increasing surface roughness enhanced the HTC. The optimal surface roughness was determined to be 3.4 μm, as it resulted in a significant increase in HTC (26.25%) with a moderate rise in power consumption (15.40%). Higher surface roughness led to a drastic increase in power consumption, making it less desirable for practical applications. Through a systematic analysis of the experimental data, this study identifies the critical trade-off between surface roughness and power consumption, providing guidance for the design of energy-efficient condensation heat transfer systems using R123yf refrigerant. By pinpointing an optimal surface roughness for copper tubes used in refrigeration, this study offers a pragmatic solution for enhancing the efficiency of air conditioning systems in mining equipment, a sector notorious for high energy expenditures. The findings indicate a direct application in mining operations where equipment cooling demands contribute significantly to energy consumption. Implementing the recommended surface modifications can lead to substantial energy savings, thereby reducing operational costs and improving the sustainability of mining activities. Furthermore, the adaptation of R123yf refrigerant systems with optimized surface roughness could serve as a model for energy conservation measures across various facets of the mining industry..

Effect of benzotriazole on the existing pits of copper tube in fire sprinkler system

In this paper, two leaking tubes were investigated among copper tubes injected with 200 and 400 ppm benzotriazole after 8 years of usage. The electrochemical tests were conducted in simulated pit-out and pit-in environments (i.e., regions outside and inside of the pit) to determine the effect of benzotriazole on the propagation of an existing pit. The electrochemical analysis results showed that 200 and 400 ppm benzotriazole exhibit relatively lower inhibition efficiency in an acidic simulated pit-in environment because of the difficulty of forming a protective film and the benzotriazole cationization.

Investigation of the Concentric Heat Pump with Improved Energy Performance

This paper investigates the energy characteristics of the concentric heat pump. The heat exchanger of the evaporator of the "pipe in pipe" type, through the inner copper tube of which the refrigerant circulates, and inside the outer pipe - the coolant, is placed in a spiral around the compressor, cooling it and at the same time absorbing the heat released by it. The new design improves technical and economic performance. Experimental results were carried out, which confirm the possibility of maintaining the compressor temperature (80-90°C), increasing the heat output and conversion coefficient (COP) by an average of 10-15%. The proposed technical solution makes it possible to improve the energy efficiency of the concentric heat pump due to the absorption of the excess heat from the evaporator in the general heat flow and to reduce the emissions of CO2.

Experimental study on the thermal performance of Type-C near dew point radiant cooling wall panel

The radiant cooling system is a highly promising cooling technology that offers significant development potential. This paper introduces an innovative aquifer-cooled radiant wall panel, comprising a box, an aluminium plate, copper tubes, and water. The inclusion of water in the box optimizes heat exchange between the copper tube and the aluminium plate, as well as promoting uniform surface temperatures throughout the radiant panel. Importantly, the installation of this radiant wall system does not compromise the height of the space, making it particularly advantageous for retrofitting buildings. Traditional radiant floor and ceiling systems often reduce the available height, potentially exceeding acceptable limits. Experimental tests have demonstrated remarkable results for the cooling capacity of the radiant cooling wall panel, with an increase of 19.5 % to 49.3 % per unit area compared to the graphite radiant cooling ceiling plate under identical test conditions. Furthermore, the maximum temperature difference observed on the panel surface during operation is less than 1.8 °C, highlighting the system's efficiency and reliability.

Investigation of Hybrid Wires Combining Superconductive MgB2 and Ultra-conductive Graphene/Cu sheath

In our study, hybrid wires with ultra-conductive Graphene/Copper(GCu) sheath and superconducting MgB2 core were produced and experimentally examined. Cu tubes with outer/inner diameters of 15/12 mm were first coated with multi-layered graphene by chemical vapour deposition (CVD) method. Then, the ultra-conductive G/Cu tubes were filled with Mg+2B powder and they were gradually drawn into wires with a diameter of 1.94 mm. According the analysis results, the graphene coating process was successfully completed and the hybrid wires were produced by achieving MgB2 superconducting phase formation after annealing at 650∘C for 1 h. In this study, a graphene-coated copper tube with a CVD process was used for the first time to manufacture a superconducting wire. The ampacity value of industrial G/Cu sample has been improved in hybrid wires about 75% despite Cu exposed to mechanical deformations throughout the wire production process after graphene coating.

МОДЕЛЮВАННЯ ЕЛЕКТРОТЕПЛОВИХ ПРОЦЕСІВ В УСТАНОВЦІ ІНДУКЦІЙНОЇ ТЕРМООБРОБКИ АЛЮМІНІЄВИХ ЗЛИВКІВ І ВИЗНАЧЕННЯ ШЛЯХІВ ПІДВИЩЕННЯ ЇЇ ЕФЕКТИВНОСТІ ПРИ ПРЕСУВАННІ КАТАНКИ ДЛЯ СИЛОВИХ КАБЕЛІВ

A computer mathematical model is presented for the study of electrothermal processes in the installation of induction heat treatment of cylindrical aluminum ingots during pressing of wire rod for the manufacture of aluminum wire for power cables. The model makes it possible to determine energetically and technologically appropriate electromagnetic and thermal modes of induction heat treatment of ingots at a given voltage on the inductor. The results of the study of a typical installation for heating aluminum blanks for the purpose of their subsequent gradient pressing using a single-phase single-layer cylindrical inductor made of a rectangular copper tube are presented. Temperature distributions along the length of the aluminum blanks, as well as in the cross-sections of the billets at the output of the inductor, were obtained. A slight difference in the calculated electromagnetic and thermal parameters from the similar parameters of the operating installation confirmed the adequacy of the developed model. Ways to increase the efficiency of the induction heating installation by optimizing the profile of the inductor turns are considered. The influence of the thickness of the wall of the copper tube of the inductor close to the workpiece on the efficiency of the installation was determined and it was shown that its optimal thickness is at the level of the depth of penetration of the electromagnetic field into the metal. The possibility of using a three-phase power supply of the inductor was also investigated and it was shown that in this case it is most appropriate to use a phase angle shift between voltages of 60 el. degree. References 10, tables 2, figures 7.

Quantifying heat losses from experimental setup and their effect on annular channel heat flux using CFD

An advanced experimental setup in the form of a double-pipe heat exchanger has been developed to investigate various flow and heat transfer regimes in an annular channel. The experimental setup is designed for heat transfer measurements and flow visualization in a transparent annular channel with temperature-controlled heating of the inner tube. It allows measurements in both, single-phase and two-phase (boiling) flow regimes. The transparent annular channel is connected at the front and rear end by specially designed inlet and outlet headers, which ensure a uniform velocity field of the coolant (primary fluid) in the annular channel. The heating water (secondary fluid) heats the inner tube made of copper, which contains unique turbulators positioned equidistantly. These are designed to enhance the heat transfer on the inner side of the copper tube and to accommodate the thermocouples measuring the surface temperature of the tube.The main purpose of this study is to assess as accurately as possible the influence of heat losses in the experimental setup on the heat fluxes in the transparent annular channel. Therefore, it is necessary to accurately estimate the heat losses at the inlet and outlet header, upstream and downstream of the annular section. To this end, a detailed three-dimensional conjugate heat transfer CFD model has been developed and validated with a series of single-phase measurements, including the measured temperatures in both headers and the temperature profile along the heated inner copper tube. The simulated velocity and temperature fields have been used to quantify the heat flux distribution in the experimental setup. This study clearly demonstrates that properly validated numerical simulations can provide missing experimental information and significantly improve the interpretation of complex experimental results.

Evaluation of strength and electrical conductivity of copper clad-AA6063 bimetallic composite wire after annealing treatment

This study investigates the manufacturing of copper-AA6063 aluminum alloy composite wire and the effect of microstructural changes and metal-metal interface after annealing at 300 °C at different times on the strength and electrical conductivity. For fabrication of the composite wire, first AA6063 aluminum alloy wire was inserted inside an OFHC copper tube with a diameter of 6 mm. Afterward, a composite wire was produced using a cold drawing process in thirteen steps to a diameter of 1.5 mm. The tensile and microhardness tests used for evaluation of the composite wire's mechanical properties. Also, the light and scanning electron microscopes (SEM) used for microstructural characterization. The results showed that forming a region with a strain gradient at interface has a determinative effect on the strength and ductility of composite wire. The composite wire without annealing showed the highest strength, 278 ± 7 MPa. The annealing treatment result in strength reduction and negligible change in the electrical conductivity. The composite wire after annealing treatment for 30 and 60 min showed the highest electrical conductivity, 83 ± 1%IACS, and the highest elongation, 45 ± 4%, respectively.

Condensation Heat Transfer Experiments of R410A and R32 in Horizontal Smooth and Enhanced Tubes

Abstract A horizontal smooth copper tube and two enhanced tubes (a dimpled tube and a diamond-shaped tube) with a length of 2 m and an outer diameter of 9.52 mm were studied in a two-phase condensation experiment using R410A and R32 as heat transfer working fluids. The condensation heat transfer performance of different heat transfer tubes at various mass fluxes ranging from 150 to 400 kg/(m2s) and different vapor qualities ranging from 0.8 to 0.2 was studied experimentally. For R410A, the heat transfer coefficients (HTCs) of the dimpled tube and the diamond-shaped tube were found to be 1.39–1.52 times and 1.30–1.35 times higher than those of the smooth tube, respectively. For R32, the HTCs were found to be 1.46–1.59 times higher for the dimpled tube and 1.26–1.35 times higher for the diamond-shaped tube than for the smooth tube. The diamond-shaped tube was found to be effective in directing the flow of the liquid phase and in thinning the liquid film thickness. The dimpled tube was found to promote droplet entrainment and disturbance. Both of those effects contributed to improving the HTCs in the two enhanced tubes investigated. The HTCs of R410A were found to be lower than those of R32 because of the smaller specific heat capacity, smaller latent heat of condensation, and relatively poorer thermal conductivity of R410A. Taking the combined effect of heat transfer and pressure drop into account, a performance enhancement factor (PEF) was computed and was found to range from 0.9 to 1.51. Based on the experimental data collected, a new empirical correlation equation has been proposed with a maximum error band of 10%. Flow pattern maps for the tested tubes have also been generated and are presented in the paper. Both of the two enhanced tubes were found to promote the development of annular flow. The HTCs were found to be highest when the flow pattern was of the annular flow type.

An Investigation into the Factors and Mechanisms Underlying Corrosion Failure of B10 Copper Tubes in Shipboard Pipelines

The present study investigated the corrosion behavior and mechanism of B10 copper tubes used for shipboard pipelines through various analytical techniques, including macroscopic inspection, chemical analysis, electrochemical impedance, corrosion product morphology, and physical phase and electron microscopic observation. The research findings revealed that the surface corrosion product film on the B10 copper tube in seawater mainly consists of Cu2O. Furthermore, the corrosion behavior under actual working conditions was attributed to crevice corrosion, non-electric coupling corrosion, and the corrosion mechanism was found to be the result of the combined effect of oxygen concentration difference cell and occlusion cell autocatalytic effect. These observations provide valuable insights into the corrosion performance of B10 copper tubes in seawater, which could potentially aid in improving their durability and reliability in marine applications.