Copper Tube Research Articles

Experimental investigation of axial finned tube evaporator thermal distillation system using for diesel engine waste heat recovery process

The study aims to improve the waste thermal energy retrieval from flue gas of an internal combustion engine (ICE). The recovered waste heat energy was used for distillation by using a thermal distillation system. The performance of the thermal distillation unit was investigated by varying the evaporator (boiler) type and engine load (25, 50, 75 %). Four different types of boilers were used including one smooth copper tube and other three were two, three and four axial finned copper tube evaporators. The impact of boiler type and engine load on the net retrieved energy and exergy, net energy and exergy efficiency, and distillate yield rate of thermal distillation unit was also examined. The results showed that the net extracted heat energy and exergy for axial finned tube evaporator was approximately 26.823 – 45.513 % and 7.614 – 25.203 W higher than that of smooth tubes evaporator at 25 and 75 % engine load, respectively. The distillation yield was found to be ~ 2.35 liter/ hour in the case of four axial finned tube boiler at 75 % engine load.

On the performance of a latent heat thermal storage unit integrated with a helically coiled copper tube and organic phase change materials: A lab-scale experimental study

In this study, the performance of a latent heat thermal storage (LHTS) unit integrated with a helically coiled copper tube and organic phase change materials is investigated using a lab-scale experimental setup. The effects of various operating conditions such as the coil thickness, testing fluid temperature/flow rate, PCM type, turbulator, and stirrer rotational speed on phase change behavior are investigated. The evaluation is based on PCM temperature variations, total heat transfer coefficient, and thermal effectiveness. The effects of testing fluid temperature, PCM type, turbulator, and stirring speed on phase change behavior are found to be more pronounced compared to those of the coil thickness and the fluid volume flow rate. Considering the melting process, it is found that the average temperature of the PCM in the LHTS unit with a turbulator is higher than that of the case without turbulator by nearly 10 °C which indicates an improvement in the heat transfer between water-PCM. The average PCM temperature is found to increase by 2 °C and 3.5 °C when a stirrer with a rotational speed of 200 and 400 rpm is employed, respectively. The total heat transfer coefficient for the LHTS unit at a stirring speed of 400 rpm (200 rpm) shows a significant increase of 39.6% (27%) compared to the scenario without a stirrer.

ANALISA PERFORMA HEAT EXCHANGER DENGAN PENAMBAHAN VORTEX GENERATOR TIPE WIRECOIL GUNA MENCEGAH ICING PADA KARBURATOR

This study aims to evaluate the influence of vortex wirecoil generators with different pitch variations on heat transfer coefficients, pressure drop, and heat exchanger effectiveness. The method involves experiments with a prototype heat exchanger simulation utilizing exhaust gas from a genset engine to address carburetor freezing issues in aircraft with piston engines, with a parallel flow configuration. The solution proposed involves using vortex generators and shell-and-tube heat exchangers. Shell and tube heat exchangers aim to improve heat exchange efficiency because the fluid flow in the pipes bends, creating significant secondary flow and enhancing heat transfer. This study involves various tools and components, including steel wire as the vortex wirecoil generator with size variations of 1.5, 2.5, and 3.5 cm. Other components consist of galvanized iron cells and copper tubes, as per the research plan. The research results indicate that pitch variations of wirecoil inserts in concentric pipes create turbulent flow that maximizes heat transfer to the air inside the cell. The 3.5 cm wirecoil yields the highest heat transfer coefficient U0 with an average value of 10.4. Additionally, adding variations of vortex wirecoil generators in concentric pipes increases the heat release from the hot fluid in the exhaust gas, enhancing heat exchanger effectiveness. The best effectiveness performance is achieved with a 2.5 cm wirecoil with an average value of 70.09.However, adding pitch variations of wirecoil inserts also disrupts the flow, changing it from laminar to turbulent, with the highest pressure drop occurring with the 3.5 cm wirecoil, with an average value of 17.89 Pa. These findings provide insights into improving efficiency and altering flow in heat exchangers through vortex wirecoil generator variations.

Assessing passive thermosyphon solar water heater as low-cost, sustainable water disinfection technology: Leveraging the Germicidal effect of copper and thermal convection loops

This study investigated the passive thermosyphon solar water heater (TSWH) as a domestic size point-of-use water disinfection treatment system for inactivating bacteria by utilizing both the germicidal properties of copper in heat exchanger and the heat generated in thermal convection loops. Additionally, life cycle analysis and manufacturing cost analysis were conducted to reveal its environmental and economic benefits. Initially, the germicidal capacity of copper tube against E. coli and total coliform in rapidly flowing polluted water was tested in laboratory settings with contact times ranging from 1.5 to 94 min. Without any additional heat, the copper tubes achieved 99.9% (log 3.01) removal of E. coli, and 99.24% (log 2.12) removal of total coliform after 94 min of contact. In the presence of heat (50–80 ºC), complete removal of the bacteria was achieved after only 1.5 mins of contact time at 50ºC. A domestic-sized passive TSWH with a copper tube heat exchanger was evaluated for disinfecting 20 L/day of microbiologically polluted tap water and synthetic groundwater in a field study. The average contact time of polluted water in copper tube heat exchanger was 5.58±1.2 min in the morning (with an outlet water temperature of 87.3 ºC), and 11.83±1.41 min in the afternoon (with an outlet water temperature of 78±5.1 ºC). These contact times and temperatures, achieved throughout the year, were sufficient to meet the required minimum for complete bacterial removal in the synthetic groundwater. Importantly, the system achieved complete inactivation of pathogens at pasteurization temperatures below 75 ºC, relying solely on the combined effect of copper and thermal convection loops, without pumps or electricity. Compared to an active TSWH using circulating pumps and controls, the passive system generated 62.2% less green house gas, had 55.5% lower cumulative energy demand and cost 323.3 $ compared to 544.64 $. Highlighting significant economic and environmental benefits, the passive TSWH offers a promising solution for disinfecting water in low-income areas with limited access to safe water.

Considering a Utility-Centric Framework Based on "Minimum Orthophosphate" Criteria for Mitigation of Elevated Cuprosolvency in Drinking Water.

Gaps in the United States Environmental Protection Agency (US EPA) Lead and Copper Rule (LCR) leave some consumers and their pets vulnerable to high cuprosolvency in drinking water. This study seeks to help proactive utilities who wish to mitigate cuprosolvency problems through the addition of orthophosphate corrosion inhibitors. The minimum doses of orthophosphate necessary to achieve acceptable cuprosolvency in relatively new copper pipe were estimated as a function of alkalinity via linear regressions for the 90th, 95th, and 100th percentile copper tube segments (R2 > 0.98, n = 4). Orthophosphate was very effective at reducing cuprosolvency in the short term but, in some cases, resulted in higher long-term copper concentrations than the corresponding condition without orthophosphate. Alternatives to predicting "long-term" results for copper tubes using simpler bench tests starting with fresh Cu(OH)2 solids showed promise but would require further vetting to overcome limitations such as maintaining water chemistry and orthophosphate residuals and to ensure comparability to results using copper tube.

Analysis of wall thickness variation of copper tube electrode processed by ultrasonic vibration

Analysis of wall thickness variation of copper tube electrode processed by ultrasonic vibration

Experimental study of R600a boiling in microfin tube

This paper presents experiments to investigate flow boiling and pressure gradients of R600a. The study employed microfin and smooth copper tubes simulating conditions in a domestic refrigerator, using low mass fluxes (MFs) and saturation temperatures (Tsat). The test sections featured a tube length of (400 mm), an inner diameter of (4.3 mm), and an outer diameter of (5 mm). Test conditions varied, including MFs of (25, 35, and 45 kg m−2 s−1), vapor quality from (0.18–1), Tsat of (−15, −9, and −5 °C), and HFs of (10, 14, and 18 kW m−2). Both tubes shared identical dimensions, clearly comparing microfin impact on flow boiling characteristics. The study evaluated enhancement factor (EF), penalty factor (PF), and overall efficiency (η) by comparing heat transfer coefficients (HTC) and pressure gradients in the microfin tube versus the smooth tube. Results indicate a significantly boosted HTC in the microfin tube compared to the smooth tube, with a reasonable increase in pressure drop. Under specific conditions (HF of 10 kW m−2, Tsat of −9 °C, and MFs of 25 kg m−2 s−1), the average HTC is enhanced by 325%, while the pressure drop is increased by 150%. Experimental HTC and frictional pressure gradient comparisons aligned well with values predicted by existing literature correlations.

Characterization of Water-Based Anti-Corrosion and Anti-Fouling Coating in the Heat Exchanger Tube of Gas Water Heater

Due to the fouling and corrosion issues with gas water heater heat exchangers during use, a water-based coating is created using the sol-gel method and applied to the inner surface of the copper tube of the heat exchangers. The water-based coating can reduce the surface energy of copper that is oxygen-free by 82.40 % and has outstanding hydrophobicity. The coating's adhesion strength was 8.46 MPa, and its wet adhesion reduction rate was only 0.0375 MPa·d-1 when submerged in a bath of water at a constant temperature. Its water contact angle remained above 110° even after being abraded by sandpaper, demonstrating its excellent wear resistance. At a constant temperature of 45 °C, the corrosion experiment was carried out in salt, acid, and alkali solutions. The maximum corrosion rate of the coating was 3.24 × 10-2mg∙(cm2∙h)-1, which was only 20.85 % of that of the oxygen-free copper substrate. The dynamic fouling experiment shows that the coating can effectively inhibit fouling growth, prolong the fouling induction period and reduce the average fouling rate. By factoring in the fouling thermal resistance and the coating thermal resistance, the overall heat transfer coefficient of the copper tube was computed. The results demonstrate that after applying this water-based coating, the copper tube can continue to have a high heat transfer coefficient for an extended period, ensuring the continuous and effective operation of the heat exchanger and having practical application value.

A laboratory study of the failure analysis of copper tube used in the air conditioning heat exchanger

AbstractThe 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.

In tube condensation of low global warming potential refrigerants in an axial micro-fin aluminum tube

Environmental regulations have driven the development of refrigerants with low global warming potential (GWP). To design heat exchangers using these new refrigerants, data are needed concerning the heat transfer coefficient and pressure drop in two-phase flow. Another change is the increasing use of aluminum tubes rather than copper tubes to reduce heat exchanger cost. Hence, this study presents an experimental investigation of flow condensation using an expanded axial micro-fin aluminum tube with a fin-tip diameter of 5.96 mm. The experiments included single compounds R-32, R-1234yf, and R-1234ze(E), zeotropic mixtures with low glide (R-454B), and zeotropic mixtures with high-glide (R-454C and R-455A). Experiments were conducted at condensation temperatures ranging from 40 °C to 50 °C, reduced pressures ranging from 0.21 to 0.55, and mass fluxes ranging from 150 to 350 kg/(m2 s). Data obtained for these refrigerants constitute one of the first reports for high-glide refrigerants using axial micro-fin aluminum tubes. An evaluation of heat transfer degradation of zeotropic mixtures due to mass transfer resistance at the liquid/vapor interface is presented. This information can be used to design heat exchangers for next generation air conditioning and refrigeration systems.

Analysis and prevention of copper pipe corrosion

The failure of the locomotive heat exchanger due to pitting and corrosion of the T2 heat exchange copper tube is used as the engineering application background. The pitting corrosion and influencing factors of T2 copper tu were studied by weight loss method, SEM, and EDS. The optimal ratio of compound corrosion inhibitors (borax, sodium nitrite, sodium silicate, and benzotriazol) of T2 copper tube was obtained. The results show that the main reason for the pitting corrosion of T2 copper pipe is the local rupture of cuprous oxide protective film on the copper surface, resulting in the copper at the bottom of the pit as the anode and the Cu2O oxide film on the surface as the cathode to form a corrosion cell so that copper dissolves and pitting in the pit. The rupture of the Cu2O oxide film is related to excessive carbon-containing residue and the deposition of dirt (foreign matter) on the surface, mechanical attack, and defects of the material itself. The optimal ratio of compound corrosion inhibitor in 2 L pure aqueous solution is as follows: Borax content is 4.4 g, sodium silicate content is 4.23 g, sodium nitrite content is 4 g, and benzotriazole content is 0.2 g.

A comparative study on optical and thermal performance of parabolic trough concentrator using a bundle of absorber tubes

Reorganizing the larger diameter receiver tube into a bundle of smaller diameter receiver tubes in regions of high solar flux density can enhance the thermal performance of the solar parabolic trough collector. The data that really is presently available in the literatures are studied. The parabolic trough concentrator's optical performance and the solar parabolic trough receiver thermal performance is 66.4% and 74.8% respectively. It is concluded from the comparative study that the use of the original receiver bundle (copper tube selective coating), has been ascertained, improving convective heat transfer coefficient, bringing down receiver tube surface temperature and increasing thermal performance, but the expense of raising friction coefficient and pumping power.

Bending characteristics of a round strand made by stacked HTS tapes

Although the development of REBCO coated conductor has proved its superiority of critical current in high-field background, mechanical issues caused by electromagnetic forces are still big challenges. Large-scale magnets call for robust and high-Je cables for simplicity of the system. To meet the requirements, here we report a round cable comprised of a stack of 2 mm wide high-temperature superconducting (HTS) tapes inserted into a copper tube and all soldered with Sn63Pb37. The two prepared samples include five HTS tapes and four copper strips in untwisted manner. Self-field critical current at 77 K was analyzed both numerically and experimentally. The characteristics of in-plane (hard) and out-of-plane (easy) bending were analyzed by finite element method (FEM) and compared to experimental measurements. Good agreement was found between the analysis and experimental results on critical bending radius, which is about 200–215 mm. Our results indicate the robustness of the round strand and its potential for use in large-scale magnets.

Influence of surface structure and tube material on the condensation heat transfer coefficient of propane on horizontal single tubes and in tube bundles

The condensation heat transfer of propane on the outside of single horizontal tubes and in tube bundles was investigated by determining the condensation heat transfer coefficient αcond in a newly designed experimental setup. To study the influence of different surface structures and tube materials, experiments were conducted with a smooth tube, finned tubes with various fin densities and heights, and a high-performance condensation tube at vapor temperatures of 30 and 40 °C and varying heat flux densities. In addition, the influence of inundation on αcond was systematically investigated by varying the mass flow of liquid condensate at heat flux densities of 20 and 60 kW·m−2. The experimental setup was successfully validated using smooth tubes by a comparison of the resulting αcond with literature data and Nußelt's film theory. For the single copper tubes with fin densities from 19 to 48 fins per inch, αcond increased and was by factors of 9 to 21 larger than for the smooth tube at the same heat flux density. Investigations of the inundation effect have shown that the additional condensate can lead to an increasing condensate film thickness, which decreases αcond due to its increased thermal resistance, and/or can lead to turbulences in the condensate film, which increases αcond. The interplay of the two effects depends highly on the surface geometry. An increasing fin height always enhanced αcond, whereas a lower thermal conductivity of the tube material leads to a smaller αcond.

Experimental and analytical investigations on heat transfer performance of naphthalene heat pipe heat exchanger

The heat transfer performance of a naphthalene heat pipe (HP) heat exchanger (HE) was theoretically analyzed and experimentally confirmed. The tested HE comprised a staggered 9 × 17 array of copper tubes with 144 U-bends, forming a closed loop. The working fluid was naphthalene with a filling ratio of 45 %. The operating temperature range was 80–300 °C, and the airflow rate was 100, 150, 200, or 400 m3/h. The maximum heat transfer rate was discovered to be 3.86 kW, and the HP thermal resistance was approximately 0.00553 K/W for an air flow rate of 100 m3/h and at an operating temperature of 300 °C; the maximum thermal conductivity was 7155.43 W/m·K. The experimental data were compared with the predictions of empirically derived equations; the best predictions were obtained when the Jouhara and Robinson correlation for condensation was combined with the Kutateladze correlation for evaporation. The mean deviations of the predictions were 36.05 % for the overall thermal resistance and 17.34 % for the average temperature difference between the evaporation and the air side. Although the thermal conductivity of the naphthalene HP was much lower than that of a water HP, it improved as the temperature increased; hence, naphthalene HPs are effective for high-temperature heat recovery.

Experimental, numerical and deep learning modeling study of heat transfer in turbulent pulsating pipe flow

Pulsating heat transfer is important in many engineering applications but is not fully understood or easily modeled. This work helps understand the phenomenon and demonstrates the efficacy and utility of deep learning modeling for pulsating heat transfer. The convective heat transfer coefficient (HTC) of pulsating flow through a copper tube was experimentally investigated at seventy-seven different operating conditions (500,000 time-series data points were collected at each operating condition) corresponding to different pulsating waveforms, frequencies, mass flow rates and pressures. The intensity of pulsation ranged from mild to strong enough to cause reverse flow. The literature on pulsating HTC is mixed, with several researchers reporting increased heat transfer and several other reporting decreased heat transfer relative to steady flow. The experimental data showed that both could be true depending on the ratio of the amplitude to mean flow velocity (amplitude ratio AR). The enhancement ratio (ER) of pulsating HTC relative to steady-flow HTC was measured to vary between 0.48 and 2.18 for AR ranging from 0.64 to14.42. A numerical study showed that this was only a (positive) correlation; fundamentally the overall pulsating HTC could be approximately explained by the variation of instantaneous Reynold’s number (Re) during the pulsating cycle. The distribution of instantaneous Re and hence the ER is primarily determined by the pulsating waveform, and this explains the disparate observations by different researchers. Long Short-Term Memory (LSTM) networks have been used to model pulsating HTC as a function of pulsating waveforms occuring across a measurement orifice. The ‘Toy Model’ concept where physics-based variables are used to increase generalization was implemented with the LSTMs for increased model robustness. These models could be used to maximize pulsating heat transfer by optimizing the waveform.

Thermodynamic Modeling and Performance Evaluation of Absorption Refrigeration System with Graphene Nanofluid

The study presents a comprehensive computational analysis of an absorption refrigeration system that employs graphene nanofluids as the secondary fluid. The system's tube-type evaporator, utilizing copper tubes, was optimized and analyzed under varying nanofluid concentrations through thermodynamic modeling. Key thermal and design parameters were thoroughly examined, including evaporation area, heat flux, conductive and convective coefficients, and overall heat transfer coefficient. The findings demonstrate notable enhancements in the analyzed parameters when employing nanofluids in the system, with improvements of 5.2% in the pumping power of the secondary system and 0.8% in the evaporation area. These outcomes highlight the potential benefits of incorporating graphene nanofluids in absorption refrigeration systems, paving the way for more efficient and sustainable cooling solutions.

Determination of Joint Defects in Copper Tube Induction Heating Brazing Area Using Infrared Thermal Image Based on CNN Algorithm

Determination of Joint Defects in Copper Tube Induction Heating Brazing Area Using Infrared Thermal Image Based on CNN Algorithm

Optimization Design of Closed-Loop Thermosyphons: Experimentation and Computational Fluid Dynamics Modeling

The well-established practice of integrating heat pipes into thermosyphons is recognized for its efficacy in achieving energy savings. This integration facilitates heat transfer and fluid circulation without requiring additional pumps or energy input, resulting in reduced consumption, lowered operational costs, and an overall improvement in system efficiency. This research explores the energy-saving potential of closed-loop thermosyphons, with a specific focus on their integration in latent heat-based heat pipe technologies in industrial settings. The study systematically investigates the influence of thermosyphon orientation on energy efficiency through a combination of experiments and computational fluid dynamics (CFD) simulations. Thereby, it results in superior heat transfer rates in forced convection scenarios. A closed-loop thermosyphon heat exchanger undergoes evaluation in three panel installation configurations relative to the ground, taking into consideration factors including copper diameters, coolants (with or without R410a), and temperature conditions. CFD validation identifies an efficient thermosyphon design—a panel oriented perpendicularly to the ground and filled with R410a refrigerant at 90 °C. It utilizes a 19.05 mm copper tube for forced convection. This optimized design demonstrates a commendable heat transfer rate of 1485 W and a heat transfer coefficient of 1252 W/(m2·K), significantly enhancing thermal process efficiency and resulting in notable energy savings.

Saturated water flow boiling heat transfer and pressure drop in scalably microstructured plain and finned copper tubes

Well established understanding of flow boiling heat transfer and its hydrodynamic driving mechanisms have led to the inception of surface geometry augmentation techniques that can enhance thermal-hydraulic performance. Enhancing the flow boiling heat transfer at a reasonable pressure drop enables the deployment of more compact and efficient heat exchangers and thermal systems. To enable ease of manufacturing, simplicity, and reliability, passive augmentation techniques that do not require external stimuli are preferred. In this study, a scalable copper microstructuring technique was developed on both smooth and internally finned 0.25” tubes to investigate how it affects the thermofluidic behavior of relatively higher surface tension water during saturated flow boiling. The internally finned tubes used in this study comprised of 50 fins with a helical angle of 13°. To apply the conformal microstructures on the internal tube surfaces, chemical oxidation via an alkaline mixture was used, resulting in structures having characteristic length scales approaching 200 nm −1 µm. Our results show that microstructuring of plain copper tubes provides a water flow boiling heat transfer coefficient enhancement ranging from 10 % to 90 % compared to untreated specimens for vapor qualities ranging from 0 to 0.1 and mass flow rates ranging from 255 to 485 kg/(m2·s). Augmentation is attributed to the increased roughness of the plain copper tubes that creates additional nucleation sites for enhanced liquid entrapment and increases wettability. Associated with this heat transfer augmentation is an increased pressure drop ranging from 0.5 % to 38 % relative to untreated tubes due to the increased skin friction as well as add fluid flow disruption. Overall, the performance factor ranged between 0.86 to 1.81 demonstrating that the augmentation in heat transfer overshadowed the increase in pressure drop. Interestingly, applying the conformal microstructures on internally finned copper tubes decreased the heat transfer coefficient and pressure drop by as much as 75 % and 45 %, respectively, when compared to the un-structured finned copper tubes counterparts. The decrease in heat transfer performance and pressure drop was attributed to partial wetting of the fin roots due to the presence of a vapor layer near the inner tube walls. Our work develops a mechanistic understanding of the role that microstructures play during flow boiling of water on industrially applicable smooth and finned tube geometries and designs.