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The present article is focused on the condensation process of exhaust gases to reduce the air pollution to a possible extent. It is accomplished by circulating liquid N2 through copper tubes inside a chamber that is designed to condense the oncoming exhaust gases from the muffler of automobiles, thereby condensing a significant portion of exhaust gases. The condensed gases can be stored and processed at any industrial premises for recycling in a cost-effective manner. The work reported herein compares the design and analysis of two different mechanisms to achieve the effective condensation of automobile exhausts (i.e.)., one involves the employment of copper tubes with Liquid N2, and other involves porous bed kept inside copper tubes with Liquid N2. It is observed that a significant improvement in the heat transfer characteristics of the later version with porous bed over the other counterpart. The modelling and meshing of copper tubes with porous material is a tedious process, because it requires a huge number of nodes to capture the geometry. Hence, the non-equilibrium porous bed module available in the ANSYS Fluent tool is used to carry out the numerical analysis of the entire model. Further, the performance characteristics of the porous bed model are validated with a small sectional model of copper tube with porous bed and by a novel experimental technique involving distilled water in copper tubes. The outcomes of the studies are presented with different colour band metrics and trial experimental results. [ABSTRACT FROM AUTHOR]

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The failure behavior and the failure mechanisms of the copper tube used in the air conditioning heat exchanger were analyzed using macrostructure and microstructure examination and the chemical composition analysis of the corrosion products. Results showed that the corrosion of the exterior surface of the copper tube should be responsible for the failure of the air conditioning heat exchanger. The chemical compositions of the corrosion products mainly included Cu, O, C, P, S, Cl, and so forth. The corrosion mechanisms were electrochemical corrosion under the circumstances of a humid environment, oxygen, and some corrosive medium. The corrosive media were organic carboxylic acids, Cl−, H2S, and SO2, which came from air pollutants, the combustion of fuels, the automobile exhaust, and the industrial waste gas. One or more electrochemical corrosion destroyed the integrity of the copper tube and led to the failure of the air conditioning heat exchanger in advance. [ABSTRACT FROM AUTHOR]

The objective of this research is to investigate the performance increase of evacuated solar collector with nano fluid. Solar collector includes absorber unit to transfer the heat energy to a working fluid. In this research it was intended to evaluate performance considering with nano fluid. Improving the heat collection efficiency, efficient extraction of the heat from the solar collector, controlling the operating temperature, long maintenance free life of the device are some of the major challenges in collecting and extracting heat from the evacuated solar collectors. Using nano fluids as working fluids are interesting and challenging. Improvement in the performance of the evacuated heat pipe was obtained using heat transporting nano fluid consisting of aqueous dispersion (3 weight %) of Copper Oxide (CuO) nanoparticles; in comparison with the device without utilizing the nano fluid. From the past research, authors have analysed the performance with numerous trials. The result shows that evacuated tube heat pipe collector with nano fluid give the better result than heat pipe collector without nano fluid. [ABSTRACT FROM AUTHOR]

Sequential knurling and cutting-bending method is proposed to manufacture leaf-like integral outside finned tubes (LIOFT). The numerical analysis method was used to explore the material fracture and plastic forming processes. Single-factor experiments were used to establish quantitative relationships between process parameters and forming quality to guide the design of experimental parameters. The results of the numerical analysis revealed that the teeth of the knurled tube were cut by the tool's main cutting edge and then slide-bent along the rake face and minor cutting edge during the forming process. The knurling direction significantly affects the fin height and shift, a reasonable knurling direction increases the fin height by 40.1% while reducing the fin shift by 94.0%. Increasing the friction coefficient and tool feeding speed slightly increases the fin height but reduces the fin strength and finning ratio. The combination of experimental parameters was optimized based on the numerical analysis results, and a LIOFT with a maximum fin height of 3.46 mm was manufactured accordingly. [ABSTRACT FROM AUTHOR]

Due to its excellent processability, thermal conductivity and high corrosion resistance, the copper tube applied to the heat exchanger is joined by the brazing process. In order to improve the performance of heat exchangers, it is essential to inspect the joint quality of copper tubes, but it is difficult to identify defects in tube-shaped joints without cutting. To solve this problem, this study proposes a new detection method based on the Convolutional Neural Network (CNN) model to detect joint defects that occur in brazing joints of copper tubes. In the experiment, a brazing joint using high-frequency induction heating was performed on a 12.71 mm diameter copper tube, which is mainly used in heat exchangers, and the joint failure was judged based on the penetration depth of the filler material measured by vertically cutting the joined copper tube. In addition, thermal image data having a data structure of 80 × 80 pixels per frame was collected to be used as data to determine whether the brazing joint is defective in real time. Finally, using the collected thermal image data, we developed a CNN model with a structure that applies different hyperparameters to determine whether or not the joint of copper tube is defective. The selected CNN model produced an f1 score of 0.991 and a recall of 99.73%, and formed the basis for developing a system that identifies defects in brazing joints of copper tubes through thermal image data obtained in real time. [ABSTRACT FROM AUTHOR]

The utilization of Solar Water Heating Systems (SWHS) is a potential solution to use as an alternative to fuel and electricity in areas where these resources are scarce, costly, and not easily accessible. Research was conducted in Duhok City, Kurdistan of Iraq to evaluate the efficiency of a traditional type of SWHS, namely the serpentine collector variant. An active system collector that employed a moving water pump to facilitate the circulation of water inside the systems was used in the experiment. An analysis was conducted to assess the performance of the collector concerning solar irradiation, wind speed, and mass flow rate. This study utilized a Flat Plate Collector (FPC) with a tubular serpentine shape absorber made of steel sheet and copper tube. The serpentine collector had a maximum total heat loss coefficient of 5.53 . The serpentine collector demonstrated its highest level of practical heat gains at 561W. Its performance was observed to improve with increasing solar irradiation and water mass flow rate, but declined when wind speed exceeded the rated values. The serpentine collector achieved maximum efficiency with a flowrate of 0.042 kg/s, resulting in a productivity of 66.6%. While the maximum increase in water tank temperature in the serpentine collector was 25.8 ℃ at the mass flowrate 0.05 kg/s.

The effects of joining methods on the microstructure and corresponding stress corrosion cracking (SCC) behavior of copper tubes used in heat exchangers are evaluated by microstructure characterization and the slow strain rate testing (SSRT). The results show that the brazed joint (BJ) had worse SCC behavior and poorer fracture toughness than the mechanical joint (MJ). The fracture surfaces of the BJ and MJ samples after SSRT demonstrated the different fracture behaviors of the samples, especially intergranular brittle fracture in the BJ. Copper oxide layer on BJ is found to be extremely detrimental to the SCC behavior. Furthermore, a numerical model is established to predict and analyze the onset of the SCC along the surface of BJ. [ABSTRACT FROM AUTHOR]

The Parallel Tubular Channel Angular Pressing Process (PTCAP) has emerged as a promising method for refining the grain structure and enhancing the mechanical properties of metallic materials through severe plastic deformation. This study focuses on a comprehensive investigation of the PTCAP process, combining experimental and numerical analysis to gain insights into its underlying mechanisms. Experimental investigations involve processing a commercially pure copper tube using PTCAP under controlled conditions. In parallel, an explicit numerical analysis is developed using ABAQUS software to simulate the deformation behavior during PTCAP. The model incorporates material constitutive equations and accounts to describe the material response under high strain rates and large deformations. The research aims to investigate how multi-pass PTCAP affects hardness, strain homogeneity, and stress distribution. A comparison between the load punch from the experimental and FEM is conducted to validate the FEM results, and there is a good correlation between both. Hardness measurements are conducted at various stages to quantify the changes in material hardness resulting from the successive PTCAP passes. The hardness of the Cu tube increased by 63.45, 94.51, 103.98, and 105.64% after 1 to 4 passes, respectively.

Copper tubes used in air‐conditioners and refrigerators often fail due to ant nest corrosion (ANC) in formic acid environment. In this paper, corrosion behavior and corrosion mechanisms of copper tubes in formic acid (HCOOH) were analyzed by vapor corrosion tests, optical microscopy (OM), scanning electron microscope (SEM), energy‐dispersive X‐ray spectrometry (EDS). The effects of the surface condition on ANC of copper tube were also investigated. Results showed that ANC of copper tube was a spontaneous process. The surface integrity of copper tube surface oxide layer is not the decisive factor of ANC. ANC originated from the dissolution of the surface oxide layer in HCOOH, which exposed fresh copper matrix. ANC is a special electrochemical corrosion, where the copper matrix acts as an anode and the undissolved surface oxide layer acts as a cathode due to the potential difference. The accumulation of corrosion products consisting of Cu(HCOO)2 and Cu2O can produce a wedge effect and generate many microcracks until to penetrate the copper tube wall. These findings would provide a deep understanding of the corrosion behavior of copper and copper alloys. [ABSTRACT FROM AUTHOR]

The welding process is one of the fabrication processes in which tubes can be performed for structural purposes and transport liquids or gases. This study is focused on the manufacturing, characterization, and evaluation of mechanical properties of welded tubes made from oxygen-free copper (C1020) sheets using friction crush welding. The welded tubes were produced using different tool rotation speeds (1500, 1600, and 1700 rpm) and feed rates (130, 140, and 150 mm/min). The flanged edge height of 2.5 mm and 0.5 mm gap between the ends of the copper sheet was used. All examinations on welded tubes were achieved using different instruments such as optical microscopy, SEM, hardness, and tensile testers. The microstructure study showed good weld quality and good material flow between the two ends of the copper sheet in the weld zone. Moreover, the weld zone was not defective. The lowest hardness was identified in the crush zone due to the coarseness of the copper grains. The highest tensile strength of 105 MPa was obtained at the tool rotation speed of 1500 rpm and 130 mm/min feed rate. The results also showed that ductile fracture is the main source of failure.

Forensic engineers investigating water loss incidents, caused by water leaking from damaged copper tube piping systems inside buildings, are tasked with determining if that damage is from the piping being exposed to subfreezing temperatures or some other cause. This paper provides guidance for such investigations and factual basis for such opinions, including presenting the results of experimental testing of water-filled copper tube piping systems exposed to subfreezing conditions. It also discusses piping standards and building codes. When ice forms a solid plug inside a pipe, the portion of the piping downstream of that plug becomes isolated. As the ice plug grows, the pressure in the isolated portion of the piping system increases dramatically from hydraulic pressure until the strength of the "weak link" is exceeded, which causes a rupture that relieves the pressure. Oftentimes, no significant water flows through the rupture at that time because the ice plug prevents water flow through the pipe. However, significant water flow occurs once the plug melts. This paper demonstrates why it is critically important for forensic engineers to understand this sequence of events. [ABSTRACT FROM AUTHOR]

Deposition of well-adherent diamond-like‑carbon (DLC) films on copper is relatively difficult due to weak bonds between copper and carbon. The Cu-O-Si-C nanostructure was proposed to improve the adhesion and the corrosion-resistance of multilayer Si-DLC/DLC film on an inner surface of copper tube prepared by PECVD. First, the copper alloy was pretreated by oxygen. Then mixture gas of tetramethylhexylsilane (TMS) and oxygen was used to deposit interlayer, and finally multilayer Si-DLC/DLC film was deposited using the gas C 2 H 2 and argon. Transmission Electron Microscope (TEM) demonstrated that there existed CuSiO 3 , CuO, SiC, SiO 2 nanostructures in the interlayer. And X-ray Photoelectron Spectroscopy (XPS) proved that there were actually Cu O, Si C and Si O bonds at the interface. These bonds and compounds enhanced the adhesion between multilayer Si-DLC/DLC film and copper substrate. The polarization potential was significantly improved to −0.07 V, achieved through the process of oxygen pre-implantation and the combined deposition of oxygen and TMS. Furthermore, the adhesion of the film was estimated by the Rockwell test and reached HF1-HF2. The Cu-O-Si-C microstructure plays a crucial role in enhancing the adhesion and corrosion resistance of multilayer Si-DLC/DLC film. • The Cu-O-Si-C nanostructure was proposed to improve the adhesion of DLC coatings on copper substrate. • Oxygen was used to pretreat the surface of copper alloy before depositing. • The Cu-O-Si-C nanostructure enhanced the corrosion resistance of DLC films on copper substrate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hollow copper microtubes were synthesized by electrochemical template synthesis. • The two-stage process "annealing-electroreduction" increased the ECSA of microtubes by 10 times. • The overpotential of HER on hollow copper microtubes are improved to 215 mV. This study is devoted to the electrochemical template synthesis of Cu-based electrode materials for the efficient hydrogen evolution reaction (HER). Hollow copper tubes with an inner diameter of 23 μm and a wall thickness of 2.5 μm were synthesized by the three-step method: electrodeposition of copper on the carbon felt (template), annealing of the composite in the air toward copper oxides with hollow tube (HT) morphology, and their electrochemical post-reduction to copper HT with the dendritic surface. The electrocatalytic test of the resulting material showed that the overpotential of HER is 215 mV, and the Tafel slope is 177 mV/dec. The electrochemical active surface area of the copper HT increased almost 10 times – from 300 cm2 to 2850 cm2 – relative to the electrodeposited sample. The stability test of the electrode material confirmed its high activity within 24 h at a current density of 10 mA∙cm−2 and an overpotential of −280 mV. [ABSTRACT FROM AUTHOR]