Constant Discharge Rate Research Articles

Fluid upwelling and alluvial controls on spring localization: An example from Sri Lanka

In water-scarce regions, perennial springs can be a valuable source of drinking water. However, to identify unreported springs and shallow water upwelling zones, it is essential to understand the factors that control spring localization. In a crystalline basement, as in Sri Lanka, without a sedimentary cover, faults and fractures provide the only far-reaching fluid pathways and springs commonly emerge at fault/fracture intersections. While surveying cold and hot water springs in Sri Lanka, it was observed that all springs probed were located at the edge of alluvium. In order to gain insight into this relationship, we performed a topographic and geomorphological analysis was conducted utilizing remote sensing, geological and soil maps, and geological mapping in the field. The results of our analysis of 27 springs indicate that their localization is controlled by fault intersections, non-permeable clay in the alluvium and laterite, and the chemically weathered surface of the bedrock. Furthermore, the constant discharge rates observed over the years and isotope analysis suggest that the springs are part of a tens-of-kilometer-wide regional groundwater system. Based on these results, we propose a conceptual model in which water rises at fault intersections from depth until it reaches the base of the alluvium where up to several meters thick clay with low to zero permeability further inhibits vertical flow forcing the water to spread laterally. Along the alluvium clay boundary with the more permeable weathered bedrock, the water continues its path to the surface. The localization of springs differs from that of fault intersection by tens of meters, with the potential for mixing between shallow and deep groundwater. This observed effect of alluvium and their contact boundaries on spring localization has not been reported for Sri Lanka. Consequently, discharge rates may be significantly increased if the fault intersections are specifically targeted by shallow drilling.

Life cycle testing and reliability analysis of prismatic lithium-iron-phosphate cells

ABSTRACT A cell’s ability to store energy, and produce power is limited by its capacity fading with age. This paper presents the findings on the performance characteristics of prismatic Lithium-iron phosphate (LiFePO4) cells under different ambient temperature conditions, discharge rates, and depth of discharge. The accelerated life cycle testing results depicted a linear degradation pattern of up to 300 cycles. Linear extrapolation reveals that at 25°C temperature, an increase in the discharge rate from 0.5 C to 0.8 C reduces the cycle life significantly by 52.9%. On the other hand, at a constant discharge rate, an increase in temperature reduced predicted cycle life in the range of 23.2–41.36%. Lithium-ion cells’ reliability modeling and analysis was carried out using an exponential distribution showing the increasing failure rate with age, with the temperature significantly reducing the expected life of the cells.

Decoding range variability in electric vehicles: Unravelling the influence of cell-to-cell parameter variation and pack configuration

This study addresses the common occurrence of cell-to-cell variations arising from manufacturing tolerances and their implications during battery production. The focus is on assessing the impact of these inherent differences in cells and exploring diverse cell and module connection methods on battery pack performance and their subsequent influence on the driving range of electric vehicles (EVs). The analysis spans three battery pack sizes, encompassing various constant discharge rates and nine distinct drive cycles representative of driving behaviours across different regions of India. Two interconnection topologies, categorised as “string” and “cross”, are examined. The findings reveal that cross-connected packs exhibit reduced energy output compared to string-connected configurations, which is reflected in the driving range outcomes observed during drive cycle simulations. Additionally, the study investigates the effects of standard deviation in cell parameters, concluding that an increased standard deviation (SD) leads to decreased energy output from the packs. Notably, string-connected packs demonstrate superior performance in terms of extractable energy under such conditions.

Performance optimization and scheme evaluation of liquid cooling battery thermal management systems based on the entropy weight method

Liquid cooling battery thermal management system (BTMS) is widely used in electric vehicles (EVs). A suitable liquid cooling BTMS scheme needs to be selected based on the magnitude of the weights for system performance. In this paper, thirty-six liquid cooling BTMS schemes involving the variables of cooling plate material types, flow channel layouts and inlet flow velocities are evaluated by using the entropy weight method (EWM) based on information theory. The weights and information entropies of the cooling performance, energy consumption performance and material cost of the system have been calculated and analyzed. The optimal scheme is selected considering global optimization based on the evaluation indicators. In addition, the cooling performance of the optimal scheme is examined under cyclic testing conditions (WLTC and US06). It is found that the flow channel layouts of the liquid cooling plate have a greater influence on the temperature control capability and temperature uniformity capability of the system. The liquid cooling system with a serpentine flow channel at an inlet flow velocity of 0.5 m·s−1, and aluminum as the cooling plate material exhibits the best cooling performance, energy consumption performance, and lowest material cost. The weights of material cost are 0.44, 0.32, and 0.34 under 1C discharge rate and cycle tests (WLTC and US06), respectively, which are the largest weight among the evaluation indicators. Material cost has the greatest degree of information dispersion because of the minimum information entropy, which plays a significant role in multi-attribute decision-making process. The temperature rise variation of the maximum temperature of the battery module under cyclic testing conditions is more reliable and dynamic compared with constant discharge rate conditions.

THERMAL PERFORMANCE ANALYSIS OF LITHIUM-ION BATTERY PACK BY INTEGRATING PHASE CHANGE MATERIAL WITH CONVECTIVE SURFACE COOLING TECHNIQUE

The thermal behavior of the lithium-ion battery (LIB) pack has a substantial impact on its cycle life, charge-discharge characteristics, and safety. This research presents a comparative experimental analysis of the thermal performance of a lithium-ion battery pack designed for an electric bike, both with and without using phase change material (PCM). In both cases, a novel approach of passing air over the battery pack casing is employed to induce forced convection conditions, ensuring compliance with IP67 standards. The study examines the temporal variation of battery pack temperature at various constant discharge rates. The study demonstrated that the forced convection cooling method was more effective in maintaining the battery pack maximum temperature (<i>T</i><sub>max</sub>) below the optimal and safe temperature limits as compared to the natural convection cooling method in the absence of phase change materials. With the incorporation of PCM, the <i>T</i><sub>max</sub> value is found to be 12.4°C lower than that of the baseline case. Furthermore, the temperature homogeneity within the battery pack was significantly enhanced, as the maximum temperature difference [(Δ<i>T</i>)<sub>max</sub>] was reduced by 3.3°C compared to the baseline case. The combination of natural convection cooling and PCM is the most effective in controlling the battery temperature at 0.75 C discharge rate. The experimental data presented in this work could provide a good practical insight into the battery thermal management for electric bikes application.

Development of Electro-Thermal Model for Air Cooling Study of Electric Vehicle Lithium-Ion Battery Module Operating in Indian Conditions and Drive Cycle

Lithium-ion cells have higher energy density at a specific power, making them a primary choice for battery packs in energy storage of modern technology, powering from smartphones to Electric vehicle (EV) and grid-scale energy storage systems. However, their performance, safety and lifespan are temperature sensitive and developing a fail-safe mechanism is considered as a pressing priority. In the present study, a 2D electro-thermal model is developed in MATLAB to characterize the thermal behaviour of cylindrical cells (individual and inline) during discharge. The thermal model solves the transient heat conduction equation with internal heat generation. The model is validated with the available experimental data for a single cell at a constant discharge rate and found to be in good agreement within 0.5°C. The analysis is extended to a battery module with 6 cell-inline configuration and validated. This validated model is used to study the impact of multiple cells (1-10) in inline configuration. For Indian drive cycle analysis, the current profile is estimated based on the drive cycle and its impacts on cell temperature rise in battery module is studied when subjected to variation in monthly average ambient temperature. Battery module maximum temperature rises to 60 °C and Δ T (Tmax - Tmin) across cells is 8.8 °C during summer conditions under natural convection due to multiple drive cycle loading. The battery module temperature can be kept under safe operating limits (Tmax≤ 45 °C, Δ T ≤ 4 °C) with forced convection of 2 m/s and 25 °C. The study aims to provide insights into the thermal behaviour of Lithium-ion cells that can be used to design safe and cost-effective air-cooled thermal management system for battery module.

EXPERIMENTAL STUDY OF BATTERY TEMPERATURE UNDER CONSTANT DISCHARGE RATE

This research is about an experimental study of battery temperature under constant discharge rate. This study consider constant discharge rates, constant air velocities, gap between battery cells in the battery module and placement of Resistance Temperature Detector (RTD) sensors to achieve the objective of this experiment studies. The relationship of temperature and discharge rates for different point on battery cell surface is compared. The Lithium-ion battery cells are discharged with a constant discharge current in this experiment. The heat generation on the battery surface as a function of discharge time are linked to the LabVIEW software. An axial fan creates constant air velocities that help in removing heat away from battery module during discharge process. The factors that are considered in this experiment are the discharging rate, air velocities and the thermal behaviour of the Lithium-ion battery cell on various point across the battery surface.

The role of the particle aspect ratio in the discharge of a narrow silo

The time evolution of silo discharge is investigated for different granular materials made of spherical or elongated grains in laboratory experiments and with discrete element model (DEM) calculations. For spherical grains, we confirm the widely known typical behavior with constant discharge rate (except for initial and final transients). For elongated particles with aspect ratios between 2 ⩽ L/d ⩽ 6.1, we find a peculiar flow rate increase for larger orifices before the end of the discharge process. While the flow field is practically homogeneous for spherical grains, it has strong gradients for elongated particles with a fast-flowing region in the middle of the silo surrounded by a stagnant zone. For large enough orifice sizes, the flow rate increase is connected with a suppression of the stagnant zone, resulting in an increase in both the packing fraction and flow velocity near the silo outlet within a certain parameter range.

Overcoming the influence of a 2 metre long pipe offset on water flow capacity of drainage with secondary ventilation in a high-rise building

A potential consequence of installing a 2 m long pipe offset on a ventilated drainage system in a high-rise buildings is that the water seal could be damaged when the flowrate exceeds the maximum discharge capacity of a drainage system, thereby threatening the indoor health safety. Some high-rise buildings are designed for commercial and residential use to achieve economic and social benefits, so the whole building use and layout changes in the vertical direction. The drainage stack may be designed with an offset between floors to avoid structural obstacles inside the building. The flow direction change could destroy the water seal of sanitary appliances and threaten the health of residents. To better understand the influence of the form of a pipe offset on the drainage capacity, a full-scale experiment was conducted to study the secondary ventilated system with an antireflux H-tube pipe, which was equipped with two guide plates inside to improve the air-water flow pattern and prevent backflow, installed between floor. This study also considered a kind of offset where the offset distance was 2.0 m rather than the S-shaped offset joint, which is more common in commercial and residential complexes. The influence on the discharge capacity of installing an extra antireflux H-tube pipe was compared with normal 90-degree elbow and only one antireflux H-tube pipe above the offset point. The pressure fluctuation and water seal losses under constant discharge rates were adopted as experimental parameters to determine the maximum discharge capacity according to Standard for Capacity Test of Vertical Pipe of the Domestic Residential Drainage System. Results show that the installation of an extra antireflux H-tube pipe can release the air accumulation caused by pipe offset, and the combined installation of a large curvature elbow and an extra antireflux H-tube pipe can effectively improve the discharge capacity.Practical Application: 2 metre long offsets are not unusual in ventilated drainage systems in high-rise buildings, however, designers and builders do not pay sufficient attention to the adverse consequences of the pipe offset. An extra antireflux H-tube pipe can be installed above the offset joint to optimise the drainage system to perform as it would without the offset. In a system with 2 m long pipe offset, installing a large curvature elbow together with an extra antireflux H-tube pipe together provides a better effect.

Transient analysis of a green hydrogen production and storage system using Alkaline electrolyzer

Solar energy as a renewable energy resource has many applications in industry. Among them, green hydrogen production is one of the issues that has recently attracted a lot of attention. In this study, the time-dependent behavior of a solar-based hydrogen production system has been investigated by employing TRNSYS program. Results show that the hydrogen production of the system is significantly related to the seasonal climate changes during a year. The output power of photovoltaic panels is outmost in summer and spring. Due to restrictions on the volume of the storage tank, hydrogen production is limited, especially in summer. Investigations for a 5 m3 tank with a constant hydrogen discharge rate indicate that April and May are the most productive month of the year with 1137 m3 and 1110 m3, respectively. Total annual 46.67 MW of electrical power generated in panels produced over 9600 m3 of hydrogen. Increasing the tank volume to 20 m3 increases annual hydrogen production by 9%. Utilizing an increased discharge plan in summer for the 5 m3 storage tank also increased the productivity of the system by 12% for the same annual solar panel-generated power.

Real-time state of charge estimation for electric vehicle power batteries using optimized filter

The main focus of the battery management system is the estimation of the battery's State of Charge (SOC), which is an indicator to determine the driving range of an electric vehicle. The Extended Kalman Filter (EKF) algorithm is the most promising for SOC estimation when the system is running. The EKF state estimation algorithm is sensitive to the process noise covariance matrix Q and measurement noise covariance matrix R. Inappropriate noise covariance matrices reduce the accuracy and cause divergence in state estimation. This paper uses the Sunflower Optimization algorithm (SFO) to find the optimal values of the noise covariance matrices before applying EKF for online SOC estimation. It is clearly stated that the iterative SFO does not affect the instantaneous response of EKF in the online estimate because the SFO is only performed once to determine the optimal values. The effectiveness of the proposed identification is examined through the constant discharge rate test and dynamic driving profile. The proposed algorithm's performance indices, such as maximum error, Mean Absolute Error, Mean Square Error, and Root Mean Square Error of SOC estimation, are low compared to the trial-error method, genetic algorithm, and adaptive extended Kalman filter. Besides accuracy, the proposed method quickly converges even when the initial SOC is inaccurate. The feasibility and benefits of the proposed SFO-EKF algorithm are demonstrated by qualitative and quantitative findings on five challenging datasets. To assess the performance of the SFO-EKF for SOC estimation in constant-current discharge and extreme drive cycle situations, three public datasets and two datasheets are employed. The simulation results show that the proposed method has high accuracy and a better convergence rate in estimating SOC under static and dynamic operating conditions.

How do discharge rate and pipeline length influence the rheological properties of self-consolidating concrete after pumping?

Pumping changes the rheological properties, workability and construction performance of fresh concrete. However, there were limited knowledges on influences of discharge rates and pumping distances on the fresh properties of concrete. In this paper, effects of various discharge rates and pipeline lengths on rheological properties of self-consolidating concrete (SCC) after pumping were studied. A total of 12 SCC mixtures with the slump flow of 650–745 mm were pumped in pipelines with measured lengths of 342 m, 545 m, and 1044 m by constant discharge rates ranging between 5.1 and 11.4 L/s. Rheological properties were measured before and after pumping. Physical conditions of SCC during pumping, including pressure, shear, and temperature were estimated theoretically and experimentally. Moreover, the total organic carbon in the pore solution of SCC mixtures was measured to evaluate the change of superplasticizer adsorptions after pumping. Test results indicated that, due to pumping, the yield stress increased; the initial tangential viscosity decreased and the shear-thickening phenomenon was eliminated. The changes of yield stresses and viscosity were encouraged by discharge rates. Besides, lower initial slump flow of SCC exhibited a larger slump flow loss after pumping due to a higher shear rate experienced during pumping. The yield stress and viscosity after pumping increased with the increase of pipeline length at similar discharge rates, but decreased with the pipeline length under similar pumping pressures. The adsorption of superplasticizer increased after pumped at relative low discharge rates (5.2–5.7 L/s), but decreased at discharge rates of 7.7–10.8 L/s.

Effect of geometry and thermal mass of Direct-Metal-Laser-Sintered aluminium Heat Exchangers filled with phase change materials on Lithium-Ion cells’ passive cooling

• Direct-Metal-Laser-Sintered (DMLS) aluminium Heat Exchangers (HEX) • DMLS HEX filled with Phase Change Materials (PCM) for Li-Ion cells isothermalisation. • Effect of PCM mass and HEX geometry on Li-Ion cells isothermalisation. • Single discharge and consecutive charge/discharge cycles tests conducted. This study investigates the effect of mass and geometry as design parameters of a Lithium-Ion (Li-Ion) cell Thermal Management System (TMS) based on a Direct-Metal-Laser-Sintered (DMLS) structure filled on Phase Change Material (PCM). As part of a TMS, complex heat exchanger geometries are produced using DMLS technique, filled with a PCM, and experimentally tested using an established methodology. The design parameters investigated are PCM mass and DMLS heat exchanger geometry to assess the effects of increased thermal energy storage capacity and enhanced equivalent thermal conductivity respectively on the overall performance of a Li-Ion pouch cell. Constant discharge rate tests and stress sequences are used to reproduce realistic Li-Ion cell operating conditions. It has been shown that all PCM TMS effectively improve the isothermalisation of the cell under a single discharge at rate 3C compared to natural convection and decreased the cell maximum temperature by at least 5 °C. The enhanced heat transfer performance of finned designs further improves the temperature uniformity and decreases the cell maximum temperature. When tested under stress sequences, the TMS characterised by a higher thermal mass maintained functional isothermalisation for 5 cycles; this is an increase of two cycles than for the TMS with a lower thermal mass. By using a Pareto front analysis based on thermal and geometrical variables, specific designs are indicated as the best combination of thermal performance and additional weight for single discharge tests (i.e., intermittent load) and stress sequences (i.e., constant load).

A novel numerical implementation of electrochemical-thermal battery model for electrified powertrains with conserved spherical diffusion and high efficiency

The performance of batteries in electrified powertrain systems is highly influenced by mass diffusion and electrochemistry which are often ignored in the simulation of these systems due to the lack of a conserved, efficient, and integrable battery model. Therefore, this work numerically implements an electrochemical-thermal battery model with conserved numerical schemes and efficient numerical methods which include Jacobian-based and Jacobian-Free Newton Krylov (JFNK) solvers. The performance of the developed model is evaluated by simulating measurements of a LiFePO4 battery under constant discharge rates and Urban Dynamometer Driving Schedule (UDDS), as well as by a detailed comparison with existing battery models. The comparison highlights two features of our model: (a) negligible mass imbalances in the spherical diffusion modelling, which are five orders of magnitude smaller than those from a recent battery model in the literature; (b) efficient modelling of real-world driving cycles with the computational time two orders of magnitude shorter than that of the literature model. These advanced features indicate that our model can be applied in both fundamental electrochemical-thermal studies of lithium-ion battery and detailed simulations of electrified powertrains as an accurate and efficient sub-model.

Passive thermal management of battery module using paraffin-filled tubes: An experimental investigation

The use of carbon tubes filled with paraffin as Phase Change Materials (PCM) in a battery module designed for Electric Vehicles (EV) is experimentally studied in this manuscript. Three different placements of such tubes in between twenty 18650 battery cells are proposed and evaluated based on the measured temperature profiles inside the module under discharge rates of 1, 2, and 4 C (50, 100, and 200 A, respectively). In general, all three configurations could have an average temperature of no more than 40 °C and 55 °C for 1 and 2 C, respectively. In contrast, the 4 C discharge test shows only two out of these three configurations could still maintain an acceptable temperature profile below 70 °C. The first configuration, which offers the most straightforward design among the three, would not withstand any constant discharge rates higher than 1 C. In such as case, it could be recommended to have a spread-out placement of the PCM tubes in the battery module as in the third configuration to prevent the accumulation of dissipated heat around the battery cells, despite a possibly more complex wiring system and installations. In terms of the degree of temperature uniformity, the minimum values of all three configurations lie within the range of 0.60–0.79.

A novel data-driven method for predicting the circulating capacity of lithium-ion battery under random variable current

Accurate health status estimation and capacity prediction of lithium-ion batteries are important means to prevent a series of problems such as capacity loss, driving range and safety accidents caused by the aging of batteries. Research on battery capacity prediction based on constant discharge rate has become increasingly mature. However, as the main power source for electric vehicles, discharge current of lithium-ion battery is constantly changed by the influence of time-varying vehicle speed. Considering the effect of random variable current (RVC) discharge on battery capacity degradation, a novel predicting method for circulating capacity of lithium-ion battery is proposed. Firstly, features are extracted from the battery charging and discharging process. Secondly, the correlation between features and battery capacity is analyzed by using the grey relational analysis, and features with the higher correlation coefficient are selected as final health features. Thirdly, the online sequential extreme learning machine optimized by beetle antenna search is proposed and used to predict capacity of lithium-ion battery. Experimental results show that the minimum battery capacity RMSE predicted is 1.0294, and the cycle capacity error is mostly within the range of -3mAh∼3mAh, which proves that the method can more accurately estimate the capacity of lithium-ion batteries under RVC conditions.

Estimating Mean Bedload Transport Rates and Their Uncertainty

Measuring bedload transport rates usually involves measuring the flux of sediment or collecting sediment during a certain interval of time Δt. Because bedload transport rates exhibit significant non‐Gaussian fluctuations, their time‐averaged rates depend a great deal on Δt. We begin by exploring this issue theoretically within the framework of Markov processes. We define the bedload transport rate either as the particle flux through a control surface or as a quantity related to the number of moving particles and their velocities in a control volume. These quantities are double averaged; that is, we calculate their ensemble and time averages. Both definitions lead to the same expression for the double‐averaged mean rate and to the same scaling for the variance's dependence on the length of the sampling duration Δt. These findings lead us to propose a protocol for measuring double‐averaged transport rates. We apply this protocol to an experiment we ran in a narrow flume using steady‐state conditions (constant water discharge and sediment feed rates), in which the time variations in the particle flux, the number of moving particles, and their velocities were measured using high‐speed cameras. The data agree well with the previously defined theoretical relationships. Lastly, we apply our experimental protocol to other flow conditions (a long laboratory flume and a gravel‐bed river) to show its potential across various contexts.

Simulation of the Electrochemical and Thermal Properties of Electric Vehicle Power Batteries

The optimal energy and power performance of lithium ion batteries can be attained if a suitable thermal battery management system is used. Furthermore, to ensure the safe operation, a well functioning temperature control method, is needed. To achieve these goals, the simulation software COMSOL Multiphysics used to construct a three-dimensional electrochemical/thermal model of a monomer lithium ion battery. The simulation makes it possible to study the thermal characteristics at different ambient temperatures and different discharge rates. The obtained main outcomes are 1) The temperature of the lithium ion battery increases with increasing discharge ratio, and a sudden temperature increase is observed for higher discharge ratios, 2) For constant discharge rates, the temperature increase of the battery occurs mainly in the positive and negative electrode region, while lower temperatures are observed in the center and lower-edge region. A comparison between simulation and obtained date, indicates that the three-dimensional electrochemical/thermal model of the monomer lithium ion battery described the lithium ion battery well in terms of both heat generation and heat transfer.

Experimental study on the effect of substrate slope on continuously released heptane spill fires

The slope of ground has a significant impact on the spread and burning process for spill fires on land. In this paper, a series of continuous spill fire experiments were conducted on a fireproof glass sheet with different slope angles (0.5°, 1°, 3°) to study the effects of slope on fuel spread and burning behaviors. The results show that the spread process can be divided into four phases based on time-dependent spread area. The maximum spread area and spread rate both increased greatly with increasing slope angle for a constant discharge rate, while the effect of slope on the steady burning area was only slight. The burning rate in the quasi-steady burning phase tends to be a little lower with increasing slope. It is proved that the burning rate at the quasi-steady burning phase is lower than that of pool fires under the same burning size and the corresponding ratio is close to 0.32, independent on the discharge rate and the slope angle. Then, a simple modification coefficient was introduced and a burning rate model of spill fires was developed, which provide a basis for liquid layer simulation under the burning conditions.

Characterization of microcrystalline cellulose spheres and prediction of hopper flow based on a μ(I)-rheology model

The objective of this study was to characterize the rheology of a pharmaceutical material in the context of the µ(I)-rheology model and to use this model to predict powder flow in a manufacturing operation that is relevant to pharmaceutical manufacturing. The rheology of microcrystalline cellulose spheres was therefore characterized in terms of the μ(I)-rheology model using a modified Malvern Kinexus rheometer. As an example of an important problem in pharmaceutical manufacturing, the flow of these particles from a hopper was studied experimentally and numerically using a continuum Navier-Stokes solver based on the Volume-Of-Fluid (VOF) interface-capturing numerical method. The work shows that the rheology of this typical pharmaceutical material can be measured using a modified annular shear rheometer and that the results can be interpreted in terms of the μ(I)-rheology model. It is demonstrated that both the simulation results and the experimental data show a constant hopper discharge rate. It is noted that the model can suffer from ill-posedness and it is shown how an increasingly fine grid resolution can result in predictions that are not entirely physically realistic. This shortcoming of the numerical framework implies that caution is required when making a one-to-one comparison with experimental data.