Copper Tube Research Articles

A Study on Defect Detection of Dissimilar Joints in Cu-STS Tubes Using Infrared Thermal Imaging of Induction Heating Brazing

We proposed a novel detection method for identifying joint defects in the brazing process between copper tubes and stainless steel using a convolutional neural network (CNN) model. The brazing joints were created using high-frequency induction heating equipment, and infrared thermal imaging cameras were employed to capture the thermal data generated during the jointing process. The experiments involved 15.88 mm diameter copper tubes commonly used in plate heat exchangers, stainless-steel tubes, and filler metal containing 20% Ag. The thermal data were obtained with a resolution of 80 × 80 pixels per frame, resulting in 4796 normal joint data and 5437 defective joint data collected over 100 high-frequency induction-heating brazing experiments. A total of 10,233 thermal imaging data were categorized into 6548 training data, 1638 validation data, and 2047 test data for the development of the predictive model. We designed CNN models with varying hyperparameters, specifically the number of kernel filters and nodes, to evaluate their impact on detection performance. A comparative analysis revealed that a CNN model structure, exhibiting 98.53% accuracy and 99.82% recall on test data, was the most effective. The selected CNN-based defect prediction model demonstrated the potential of using CNN models to discern joint defects in tube configurations that are challenging to identify visually. This study opens avenues for applying CNN-based models for detecting imperfections in complex tube structures.

Effect of viscosity grade (POE) on the smooth-tube pool boiling performance with R-1234ze(E) refrigerant

In this study, the nucleate boiling heat transfer performance for R-1234ze(E) subject to lubricant oil is reported. The viscosity grade ranges from low viscosity (68 cSt) to high viscosity (220 cSt) and the tested POE oils include POEA-68, POEA-170, POEC-170, POEA-220, and POEC-220 on a horizontal smooth copper tube. The 30 different refrigerant-oil mixtures were prepared by varying the oil mass concentration ranging from 1 % to 10 % and the corresponding saturation temperatures are 10 °C, 0 °C, and − 6 °C with heat flux ranging from 10 to 90 kW/m2. The results showed that all grades of POE oils are compatible and completely miscible with low GWP refrigerant R-1234ze(E) in the given test range. The present study reveals that the heat transfer characteristics of each refrigerant-oil mixture very much depend on the saturated temperature, heat flux, oil mass concentration, and operating pressure. The highest mass concentration (10 %) consistently deteriorates the heat transfer coefficient (HTC). However, the degradation of HTC with R-1234ze(E) is comparatively less severe than that of R-134a/POE mixture. It is found that a 3 % oil concentration is regarded as the threshold concentration for the highest enhancement in the HTC when compared to the pure refrigerant. The performances of other oil concentrations such as 1 % and 5 % are subject to saturation temperature, heat flux, and evaporator pressure. In terms of the influence of saturation temperature on HTC of the mixture, it was observed that among all the grades of oil, POEC-170 oil shows peculiar behavior and its performance is independent of saturation temperature.

Enhancing Dimensional Geometry Casting using Computer Modeling

Sand casting method is used to produce many useful products for many applications. The aim of the study is to manufacture a product with excellent dimensional geometry is achieved in sand casting process at low cost. We would expect manuscripts to show how design and/or manufacturing problems have been solved using computer modeling, simulation and analysis. In this work, the important mechanical properties of hardness and surface roughness are investigated on Aluminum 6063 cast material with and without incorporating the copper tubes as a vent hole in sand casting process. Since copper has high thermal conductivity when compared to other metals, the heat transfer rate will be varying from existing system. The copper tubes have made different diameters of holes on outer surfaces with selective distance of intervals. The specific number of copper tubes with various diameters are designed by CATIA modeling software and analyzed with Taguchi Design of Experiment. Taguchi L9 orthogonal array is used proficiently in the optimal value of hardness and surface roughness. The results are revealed that the maximum hardness value of 104 BHN is attained for 10mm distance of holes made on copper tube with an angle of 90o degree. The minimum surface roughness of 2.11 micron is achieved for 20mm distance of holes made on copper tube with 45o of angle as a vent hole in sand casting process.

Analyzing The Influence of Diameter and Winding on Heat Transfer Efficiency in Spiral Tube Heat Exchangers: A CAD-Integrated CFD Study Using Solidworks Flow Simulation

Spiral tube heat exchangers (STHE) are coiled metal devices with two fluid channels around a central core, enabling counterflow or parallel flow of gases, liquids, or both. Compared to traditional straight-tube heat exchangers, STHEs offer a larger heat transfer surface area. This study used Computational Fluid Dynamics (CFD) simulation integrated with Computer Aided Design (CAD) to investigate STHE’s heat transfer performance. The STHE dimensions, a 12-mm copper tube, and a 10-inch PVC shell were adopted from a previous study. Cold and hot water at 20°C and 70°C flowed in parallel at specific flow rates. The objective was to explore the impact of STHE dimensions on heat transfer efficiency and performance. The parameters varied were the internal diameter of the copper tube and the number of spiral coil windings. Results revealed that changing the spiral heat exchanger’s diameter affected the heat transfer rate and coefficient. Larger diameters reduced efficiency due to lower flow velocities and convective heat transfer coefficients. The number of windings significantly affected heat transfer performance, with winding 5 demonstrating the highest rate and winding 7 showing the highest coefficient. CFD analysis reliability was validated by convergence with analytical solutions for heat transfer simulations with varying diameters and windings.

The TLBO algorithm-based optimal heat transfer parameters prediction of Al2O3 water nanofluids in variable pitch corrugated tube heat exchanger

This study investigated an Al2O3 nanofluid water-based tube heat exchanger fitted with a corrugated copper tube under laminar flow conditions. This study is carried out to observe the heat transfer rate within the heat exchanger. The effect of nanoparticle concentrations, the flow rate of the working fluid, and the corrugated tube pitch on the heat exchanger efficiency were analysed. The results show that when Al2O3 water nanofluids are sandwiched between corrugated copper tubes, the heat transfer rate is significantly enhanced compared to the smooth tubes. Nanofluids of Al2O3 were prepared with concentrations of 0.25%, 0.5%, and 1% in deionised water. Corrugated tubes with 25 mm, 20 mm, and 18 mm pitches were fabricated for this investigation. The deionised water and Al2O3 nanofluid-flow rates were maintained at 0.1 m3 per hours, 0.15 m3 per hours, and 0.2 m3 per hours, respectively. Results showed that Al2O3 nanofluids improved the heat transfer rate related to water-based fluids. The highest heat transfer occurred in the 18 mm pitch corrugated copper tube in which 1% nanofluid volume concentration was used as the heat transfer medium. It is observed that the heat exchanger containing corrugated copper tubes with pitch 17.88 mm having 0.98 vol.% of Al2O3 nanofluids, flowing at 0.198 m3 per hour, enhances the heat transfer rate between the working fluids.

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.