Copper Tube Research Articles

An experimental study on heat power stored by thermal dissipation in electronic components using thermosyphon integrated hybrid nanocomposite phase change material

This study investigates the heat power stored by the thermal dissipation of electronic components using a thermosyphon integrated hybrid nanocomposite phase change material storage system. The study examines various thermal performances including the percentage of thermal dissipation, thermal resistance and heat transfer coefficient using benzene, deionized water, methanol and methyl acetate as heat transfer fluids, with an intended heat input of 50 – 120 W. The 0.5 wt% copper-titania hybrid nanocomposite particles are dispersed with phase change material (methyl cinnamate) and chosen as hybrid nanocomposite phase change material. The assessment of charging and retrieving characteristics of stored hybrid nanocomposite phase change material has been done by the impact of heat transfer fluids flowing through the copper tube at the different heat inputs. The result findings show that methyl acetate has the maximum percentage of thermal dissipation, low thermal resistance and high heat transfer coefficient of about 99.2 %, 0.311 K/W and 242.36 W/(m2.K) respectively at 120 W. The obtained results are attributed to the low boiling point and enthalpy of vapourization of methyl acetate. The highest heat power stored by hybrid nanocomposite phase change material is discovered as 6.5 W during melting by the impact of vapourized methyl acetate at maximum heat input owing to the higher mass flow rate and lesser time to attain steady state temperature of hybrid nanocomposite phase change material. Also, the developed system promotes thermal management in electronic components along with a minimum power saving of about 5–6 %.

Dynamic 3D Measurement without Motion Artifacts Based on Feature Compensation.

Phase-shift profilometry (PSP) holds great promise for high-precision 3D shape measurements. However, in the case of measuring moving objects, as PSP requires multiple images to calculate the phase, the movement of the object causes artifacts in the measurement, which in turn has a significant impact on the accuracy of the 3D surface measurement. Therefore, we propose a method to reduce motion artifacts using feature information in the image and simulate it using the six-step term shift method as a case study. The simulation results show that the phase of the object is greatly affected when the object is in motion and that the phase shift due to motion can be effectively reduced using this method. Finally, artifact optimization was carried out by way of specific copper tube vibration experiments at a measurement frequency of 320 Hz. The experimental results prove that the method is well implemented.

Analysing the design, fabrication, and performance of a compact parabolic trough collector equipped with a shell-type receiver made from a variety of metals and introduced with single slope solar still

In this study, a unique receiver design is given for consideration. The interior of the receiver is constructed out of aluminium, while the exterior is built of copper. The water that is held within the inner copper tube is heated by a system that circulates through it, and the hollow area that is found between the two tubes is filled with vegetable oil to decrease the amount of heat that is lost. As a direct consequence of this, low-pressure steam is generated. The efficiency of the system was evaluated in comparison to the performance of another receiver made up of the same number of tubes (aluminium). The receiver that was built with tubes made of different metals had an initial efficiency of 58.61%, whereas the receiver that was built with the same type of metal had an efficiency of just 36.5%. In conjunction with this study, integrated solar still found that due to Al-Al's introduction of this still interaction, the receiver of the parabolic trough collector has a lower efficiency. The still with the parabolic trough collector has a daily average efficiency of 52.25%, whereas the still without the collector has a daily average efficiency of 36.36%.

Compact Aluminium Foam Heat Exchangers

The aim of this study was to investigate the potential application of metal foams in shell-tube recuperators. A356 aluminium foam was cast around the internal and external surfaces of a thin-walled copper tube to enhance heat transfer between separated water streams at different temperatures. The results demonstrated that the aluminium foam drastically increased heat transfer efficiency due to its large volumetric surface area and high thermal conductivity. In the shell-tube foam recuperators, a maximum heat transfer efficiency of 48.1% was observed, compared to only 12.2% for a single copper tube without metal foam. The pressure drop across the external foam increased with the flow rate, from an average value of 1.19 kPa at 1.0 L/min to 7.36 kPa at 3.0 L/min. These findings suggest that metal foams have great potential for use in shell-tube recuperators, which could significantly improve the efficiency of heat transfer in various industrial and engineering applications.

Estimating thermal performance of thermosyphons by artificial neural networks

The overheating of electronic devices has become very common with the advancement of technology, requiring the development of new alternatives for thermal control. Due to their excellent heat transfer ability, no external power is needed and they are adaptable to different geometries and applications. Thermosyphons are an excellent alternative for this thermal control. The thermal performance of thermosyphons is usually evaluated by their thermal resistance, and several variables were investigated to understand their influence on this parameter, such as working fluid, filling ratio, and slope. In that way, the fact that the thermal resistance depends on several variables makes its prediction complex and time-consuming. To overcome this issue, artificial intelligence-based methods, such as Artificial Neural Networks (ANNs), could be used. In this sense, an experimental investigation of the thermal performance of thermosyphon under different filling ratios (20 to 100%), slopes (45 and 90°), and heat loads (5 to 45 W) was made. The experimental data were then used as the database for different ANNs to predict the thermal resistance of a thermosyphon. For the experimental investigation, a thermosyphon of copper tube was built of 9.45 mm and 7.75 mm outer and inner diameter and a length of 500 mm. Its regions, evaporator, adiabatic section, and condenser, had 80, 20, and 100 mm, respectively. Distilled water was used as the working fluid. The evaporator was heated due to the Joule’s effect resulting from power dissipation in an electric ribbon wrapped in its length. The condenser was cooled with a 5 m/s air-forced convection. Regarding the use of ANNs, Unorganized Machines (UMs), composed of Extreme Learning Machines (ELM) and Echo State Networks (ESN), were proposed. As a means of comparison, the Radial Basis Function Network, and the Multilayer Perceptron (MLP), the most widely known neural architecture in the literature, were also applied. To estimate the thermal resistance of thermosyphon, the filling ratio, slope, and heat load were considered as inputs, and a total of 67 samples were used. Experimental results indicated that the best thermal performance occurs at a filling ratio of 40%, while the slope of 45° presented a better performance than 90°. The computational results revealed that the UMs could overcome the other methods, especially the ESN. The difference between the predicted and the experimental values was up to 25% for almost all cases. As a matter of reducing the experimental tests, applying ANN was essential.

Employing perforated copper foam to improve the thermal performance of latent thermal energy storage units

The performance of latent thermal energy storage units (LTESU) is limited by the low thermal conductivity of phase change materials (PCM). Copper foam can enhance PCM's heat conduction, but its structure inhibits the internal natural convection. Based on this, the perforated copper foam was proposed to enhance the natural convection of PCM. The contrast experiment built three LTESUs (Namely, the LTESU only with the copper tube (LTESU-CT), the LTESU with full copper foam (LTESU-FCF) and the LTESU with perforated copper foam (LTESU-PCF). The melting and solidifying state, temperature distribution, and thermal efficiency were compared in three LTESUs during thermal charging and discharging processes. Results showed using copper foam could enhance the thermal performance of LTESU obviously and the perforated copper foam could generate the convective heat exchange, which had a time-average Nusselt number 34.1 % higher in LTESU-PCF than that in LTESU-FCF. Due to the reduced heat transfer area, LTESU-PCF had the lower thermal efficiency than LTESU-FCF, but its thermal storage capacity and release capacity were 6.4 % and 1.4 % higher than that in LTESU-FCF, respectively. It was confirmed that employing perforated copper foam could s enhance the natural convection and heat transfer of PCM significantly, but the perforation parameter still needs to be further explored to achieve higher thermal performance.

Cooling of a PVT System Using an Underground Heat Exchanger: An Experimental Study.

In the recent decades, the researchers have been focused on the use of photovoltaic thermal (PVT) systems that provide the best performance and cooling for the photovoltaic panels. In this study, a PVT system consisting of a monocrystalline PV panel and a spiral heat exchanger was connected to an underground heat exchanger that is buried at a depth of 4 m below the surface of the earth. The procedure of the current study can be considered the first of its kind in the Middle East and North Africa region (based on the researchers' knowledge). The study was carried out on agricultural land in Baghdad-Iraq during months of July and August-2022, which are considered the harshest weather conditions for this city. The heat exchanger consists of a copper tube with a length of 21 m and formed in the shape of 3U, and it was buried in the earth and connected with a PVT system. The results of the study showed that the site chosen to bury the heat exchanger (4 m deep) has a stable soil temperature at 22.5 °C. From various volumetric flow rates, a flow rate of 0.18 l/s was selected which is considered the highest flow rate that can show vibration in the PVT system which may harm the system. The practical measurements showed that the largest difference in the surface temperatures of standalone PV and PVT was around 20 °C in favor of the latter. The electrical efficiency of the studied PVT system also increased to outperform the standalone PV system by 127.3%. By comparing the results of the current study with studies of water-cooled PVT systems from the literature, it is clear that the proposed system is feasible and has an acceptable efficiency in such harsh weather conditions tested during the experiment.

Influence of the initial charge on the triboelectrification of millimeter size set of particles in an inclined tube

In this paper, the triboelectric charge buildup on a set of initially charged particles is investigated. During the study, 30 g of charged polypropylene particles of 2–3 mm size were repeatedly passed through a 1 m inclined copper or polyvinylchloride (PVC) tube. At the tube output, the charge is measured after each passage, allowing the cumulative charge evolution over time to be measured. The obtained curves are fitted to an exponential model to extract the time constant of the process. For each experience, particles are first charged at different levels and polarities relatively to the presumed saturation charge using both corona discharge and triboelectricity. The obtained results show that the initial charge value and polarity strongly affect the subsequent triboelectricity variations as well as the process speed. The triboelectric charge evolution is mainly related to the ratio between initial charge (Q0) and saturation charge value (Qs). Therefore, the particle's charge will increase if Q0 < Qs, decrease if Q0 > Qs, or be maintained at the same level when Q0 ≈ Qs. The particles can change polarity and be recharged with the opposite sign according to the tube and the initial charge level. This triboelectric charge behavior is explained based on the surface energy state in the electron transfer model. Furthermore, increasing the particles quantity from 5 g to 60 g reduces the saturation charge from 11 nC/g to 2.5 nC/g, which is approximately 77% less. Surface potential distribution measurements show an uneven distribution with less charge in large amounts compared to lower amounts.

Influence of wire winding on the dynamic characteristics of a pulsatile fluid conveying copper tube

Fluid-conveying copper tubes find usage in many applications, including refrigeration, heat exchangers, fuel supply lines and air conditioning. This makes it essential to explore the dynamic properties of fluid conveying copper tubes for the dynamic control of such systems. In this study, the development of a modal testing set up for studying tubes conveying pulsatile fluids and the testing techniques are discussed. The natural frequencies are discovered by performing experimental modal analysis. The influence of internal excitation due to pulsatile fluid flow was extracted using operational modal analysis. By examining the deflection amplitudes, the influence of wire winding on the dynamic behaviour of the tube is analyzed. A stiffness addition phenomenon due to wire winding is identified. This study proposes a possible vibration amplitude control method by employing wire winding in specific configurations.

Numerical and Experimental Design of the Former for TORT Cables

TORT (Tapes on Round Tube) cables, which implement high-temperature superconducting (HTS) tapes, offer additional benefit over other HTS cables, which is the internal cooling in the former itself. Up to now, the superconducting tapes of existing TORT cables have been wound on a copper tube of various diameters. However, in the alternating current (AC) mode, the high conductivity of the former causes undesirable eddy currents. Therefore, it is necessary to replace the copper with a less electrically conductive material. We designed a former from polyethylene terephthalate glycol-modified and reinforced with carbon fibers (PETG CF), polycarbonate (PC) and polycarbonate reinforced with carbon fibers (PC CF) materials in order to reduce the AC losses in TORT cables, using 3D printing technology. Because of the low thermal conductivity of polymers, the former must be specially designed to improve the cooling of the HTS tapes inside the former. Moreover, thermal deformation of the former during cooling from room temperature to liquid nitrogen temperature and resilience against low-diameter bending is another important issue that was taken into account. Detailed structural finite-element (FE) analysis was carried out using the FE modeling software ANSYS, in prototyping of the former. Based on the numerical models, formers differing in the materials used were fabricated, and subsequently a short TORT cable with wound HTS tape was electromagnetically characterized.

Effects of a solar heating system on the microclimate of an agricultural greenhouse. Application on zucchini (Cucurbita pepo)

Agricultural production has made records thanks to new heating systems that are more economical and less costly, able to cope with the temperature drops of the microclimate of agricultural greenhouses while promoting the profitability of products in terms of quality, quantity and duration of growth. This work focuses on studying experimentally the effect of a solar heating system (SHS) on the microclimate of an agricultural greenhouse. This heating system is a combination of a copper tube placed between the double roof glazing and a sensible heat storage system. This installation is based on the daily thermal conversion of solar energy and its storage for night restitution. This experimentation also includes a second control greenhouse (GC) without any heating system that allows comparison at different stages of crops growth under the agricultural greenhouses. The results of this experiment during the cold season are reflected in a temperature gain on the experimental greenhouse (GE) by 4 °C compared to the GC and 6 °C compared to external ambient air. In addition, the relative humidity recorded for the GE was in the range [70%; 74%] against [78%; 96%] in the GC. However, the relative humidity of ambient air was between [90%; 99.9%]. For the efficiency of the SHS reached out 73%. As for the cultivation under the GE equipped with a SHS, the zucchini plants developed the fruit 16 days earlier than the zucchini plants grown under the GC.

Experimental investigation of a small-scale evacuated tube-based solar adsorption chiller with emphasis on improving the cycle time

Solar adsorption chillers are attractive for their use of environmentally friendly refrigerants and their ability to utilize low-grade energy sources. The goal of the present work was to build a low-maintenance, small–capacity chilling unit utilizing a solar adsorptive cycle, which can be set up in areas that do not have an electrical infrastructure to support standard refrigeration systems. The key objective was the preservation of medicine and vaccine in remote, off-grid locations at a temperature range of 2 to 8 ˚C. For this purpose, an evacuated tube-based solar adsorption water chiller using zeolite13X-water as adsorbent-adsorbate pair was designed, fabricated, and tested in this work. The novelty of the design involved removable evacuated tube glass covers over copper tube solar adsorber. For the system with 2 kg water for chilling, the size of the evaporator, adsorber, and air-cooled condenser was calculated to be 0.14, 0.78, and 0.03 m2, respectively. With 3 kg of total zeolite13X used, the average specific cooling power (SCP) of the system was 8.23 W/kg, and the coefficient of performance (COP) was 0.18. The chilled water temperature varied from 7.99 to 29.94 °C throughout the day. Grounded on the experiments of this prototype and to flatten the chilled water curve throughout the day, a second prototype was designed and tested; the experimental data demonstrated that the chiller performance was greatly improved by using two adsorbers in alternative cycles. 61 days of experiment on this dual-adsorber system yielded an average cycle coefficient of performance and specific cooling power of 0.46 and 16.41 W/kg, respectively. The water temperature could be maintained from 3.83 to 13.14 °C in the 24 h period. This type of small-scale solar adsorptive chiller will be highly advantageous in rural set-ups with high solar irradiance for preservation purposes.

Experimental investigation and performance evaluation of spiral and serpentine collectors based photovoltaic thermal system in Peninsular Malaysia

Photovoltaic thermal (PVT) systems have been developed for nearly five decades as a further development of PV technology. The PVT system was designed to overcome the limited space for PV and solar water heaters and improve PV cell performance. However, many studies on PVT are theoretical and modeling, so experimentation is needed to confirm it. This study investigated the performance of PVT systems with a spiral and serpentine thermal collector without metal sheets in two scenarios, without and with insulation. Commercial PV was modified with the addition of a copper tube thermal collector and tested with a comparison PV under the weather of the Malaysian peninsula. The experimental results show a maximum electrical efficiency enhancement of 0.53% and a decrease in module temperature up to 5.60 °C in scenario 1. Also, the addition of insulation in scenario 2 increases thermal efficiency up to 18.26%, even though it causes a decrease in electrical efficiency. This research shows that an uncomplicated thermal collector is adequate to increase the electrical efficiency of PV panels. In contrast, the addition of insulation in the rear side of the PVT panel increases the thermal performance of PVT systems.

Characteristics of Flow-Induced Vibration of Conveying Pipes for Water and Coolant Flow

One of the effects of vibrations resulting from the flow of fluids is the failure that occurs to the structure of the systems, which in turn affects the efficiency of the parts that make up those systems. for the purpose of studying the possibility of improving the performance of the systems, a liquid other than water and coolant (super antifriz\petrol ofisi) was chosen because of its advantages that can be taken advantage of, including the high viscosity of water and its tolerance to high temperatures resulting from combustion or air temperature, as well as low temperatures to ensure the operation of the system, that is, it maintains stability system temperature to obtain the best possible condition In addition to the purity of the liquid from salts and the presence of a percentage of oil in the composition of the coolant, an insulating layer is formed inside the pipes to prevent rust and corrosion in the pipes, thus ensuring the flow of fluids and prolonging the life of the pipes. The aim is to study and analyze the effect of induced vibrations and internal pressure on fluid transport pipes, and to compare them in the cases of using water and coolant under the same conditions. An empirical analysis considering the natural frequencies produced by the effect of fluid pressure under various stabilization conditions. It was observed from the results that the higher the pressure, the greater the percentage of the deflection of the copper tubes compared to the Aluminium tubes when using both liquids (water and coolant) at the same boundary condition noted the percentage of the deflection difference when using copper pipe (from 0% to 20.3%) was less than using Aluminium (from 2% to 59%) when the pressure was increased. That mean the Aluminium pipe better than copper pipe.

Investigation of entropy generation and thermohydraulic characteristics of Al2O3–CuO hybrid nanofluid flow in a pipe at different inlet fluid temperatures

This work investigates the thermohydraulic behavior and the rate of thermodynamic irreversibility of water-based Al2O3 and Al2O3 + CuO hybrid nanofluid (HNF) in a circular copper tube subjected to a constant heat flux (CHF) of 8625 W/m2. The fluids under discussion flow in a tube at inlet fluid temperatures of 30, 45, and 60 °C. The thermophysical characteristics of the Al2O3 and HNF were studied at various temperatures and concentrations. The Nusselt number (Nu), entropy generation number (EGN), and friction factor were determined for the HNF (0–1 vol%) at different ranges of Reynolds numbers (Re) from 7000 to 44,662. The outcome of the HNF for 1 vol% is compared with that of Al2O3 nanofluid (NF). The findings show that the maximum amplification of Nu is 51, 59, and 79.7% observed for 1 vol% of HNF compared to water at 30, 45, and 60 °C. The pressure drop (Δp) and exergy efficiency (ηexe) of HNF increases with concentration and Re. The friction factor of HNF rises with concentration; however, it reduces at higher Re. Total entropy generation (TEG) of HNF reduces at higher Re and concentration. The thermal performance factor (TPF) of HNF is determined at various inlet fluid temperatures. The highest and lowest TPF of 1.7 and 1.02 were found for 1 and 0.1 vol% of HNF at 60 and 30 °C, respectively. The novel regression equations were developed to estimate the Nu, TEG and friction factor of HNF. Overall, Al2O3 + CuO HNFs can be employed as an alternative fluids thermal system cooling.

Aspects of Thermal Protection of Machine-Building and Power Equipment: Application of Oxidation-Resistant Combined Nickel-Based Coatings

Introduction. In the areas of power engineering where the thermal energy of superheated steam is used, an important aspect of providing the reliability and safety of equipment is the heat resistance of the materials employed. In the manufacture of induction superheaters, the optimal material for the steam pipe (coil) is copper. However, its ultimate resistance to oxidation does not exceed 400 °C, which significantly limits the efficiency of steam generators. Therefore, the objective of the work was to study the kinetics of oxidation of the combined galvanic coating of the Mo-Ni-Cr system applied to copper tubular samples and intended for thermal protection of steam generator coils.Materials and Methods. A combined electroplating of the Mo-Ni-Cr system with a total thickness of 12–35 μm was formed on the experimental copper tubular samples. A Mo sublayer with a thickness of about 1.5 μm on the surface of the copper tube was formed to prevent the diffusion of Cu into the Ni coating. A 1.5 μm thick chromium layer on the coating surface acted as an indicator of the oxidation process. A comparative analysis of the oxidation processes of the copper surface and the combined coating of the Mo-Ni-Cr system on a copper substrate was carried out using the methods of optical and electron microscopy, energy dispersive analysis, and precision determination of the growth parameters of oxide films.Results. The intervals of thermal stability of the copper substrate and nickel coating were experimentally determined. The obtained experimental dependences characterized the parabolic law of copper oxidation with the formation of a single-phase diffusion zone of CuO at temperatures above 350 °C, and nickel at temperatures above 750 °C, when the transition of NiO monoxide into oxide Ni2O3 began. The growth of oxide films according to quadratic laws provided a rapid increase in the thickness of the films, the accumulation of stresses in them, cracking, and chipping.Discussion and Conclusion. It is shown that the Mo-Ni-Cr electroplating is resistant to heating during long-term operation up to temperatures of 750–800 °C. The functional roles of Mo and Cr in the coating architecture were described. The work focused on the applied aspect of using the coating under study to increase the thermal stability of the steam pipelines of industrial induction superheaters with low and medium power.

Can PVT bend?: The elaboration of flexible hybrid photovoltaic thermal solar collector structure and testing methodology

In this paper the elaboration of the first prototype of flexible photovoltaic thermal collector (FPVT) has been presented. The device consisted of cross-connected copper tubes merged with a silicone pipes attached to a semi-flexible silicon PV module. The FPVT was a subject of studies to develop the testing methodology of bendable solar devices. Basing on results, the new indicators to assess their performance under bending conditions were proposed, first of all Bending Angle Modifier (BAM). Furthermore, the testing procedure allowing to evaluate and compare individual solutions concerning the degree and method of their bending were introduced. Tests conducted according to the methodology confirmed that it provides reproducible results and the developed coefficients well reflect the changes in performance of the FPVT depending on deflection. Additionally, they revealed the performance of thermal and electrical part of FPVT is analogous considering their character and values.

The Effect of Condenser Type and Refrigerant Type on the Two-Stage Vapour Compression Refrigeration System: An Experimental Study

In this study, the effects of refrigerants and condenser type on the coefficient (COP) of performance value in a two-stage intercooled vapour compression refrigeration system have been investigated experimentally with the designed device. There is a total of eight configurations designed for experiments, and these are compared with each other. During the experiments, a copper tube condenser, a micro-channel condenser, and R404A and R449A refrigerants were used in the designed device. The main focus of this study is to investigate the effect of condenser type, refrigerants, and the number of compressors on the COP in a vapor compression refrigeration system. In this study, it was concluded that designs using a micro-channel condenser have a higher COP than designs using a copper tube condenser, and the most efficient design for the system is the one using the micro-channel condenser and working with R449A refrigerant.

Comparative study on conventional and phase change material (PCM) based solar desalination still using low-pressure water as a heat storage medium.

Over the years, solar desalination is a renewable energy-driven method to produce freshwater from saline/ brackish water. Since solar radiation is available only in the daytime, many studies have been undertaken to store solar energy using phase change material (PCM). The aim of this study is to compare the two solar stills (still I as a conventional solar still and still II as a PCM-integrated solar still). In still II, using low-pressure water as thermal energy storage, PCM in a copper tube with a 1 liter capacity has been additionally installed than still I. Five trials have been conducted to compare the performance and yield between stills I and II, with various factors during the experiment. Remarkably, three distinct vacuum pressures - 712mmHg (for trials 1, 2, and 3), - 690mmHg (for trial 4), and -660mmHg (for trial 5) were used for the investigation to compare the performance of PCM-based solar still with conventional solar still among five trials. Finally, at a vacuum of -712mmHg and 175ml of water poured inside the low-pressure system, the distillate yield obtained from still II is 9.375% higher than the yield of still I.

Thermal management of cylindrical battery pack based on a combination of silica gel composite phase change material and copper tube liquid cooling

The lithium-ion battery(LIB) generates severe heat when discharging. In this study, a silica gel(SG) composite phase change material(CPCM) that is easy to fill was prepared, and its performance was tested, so as to ensure the safe operation of the battery. Besides, a battery cooling system combining CPCM and liquid cooling was established. Finally, simulation and experiment were performed to demonstrate the effectiveness of the battery pack cooling module. As revealed by analyzing the characterization results of the CPCM, the decomposition temperature of CPCM is more than 150 °C, the leakage rate of CPCM is less than 4 %, and the latent heat of phase change is 63 J/g. The thermal field simulation and discharge experiment of the battery module suggest that when the battery spacing changes from 5 mm to 15 mm and the thermal conductivity changes from 0.05 W/m·K to 0.75 W/m·K, the maximum temperature of the battery pack decreases by 10 °C, and the temperature difference between the batteries also decreases. When the flow of the variable displacement pump was maximum, the liquid cooling scheme of 3 inlets/3 outlets can still control the maximum temperature of the battery below 45 °C and make the battery temperature difference not exceed 2 °C, though the battery pack is subject to 3C(Discharge current rate) discharge - 1C(Charging current rate) charging cycle.