Discharge Temperature Research Articles

Joint Estimation of State of Charge and State of Health of Lithium-Ion Batteries Based on Stacking Machine Learning Algorithm

Conducting online estimation studies of the SOH of lithium-ion batteries is indispensable for extending the cycle life of energy storage batteries. Data-driven methods are efficient, accurate, and do not depend on accurate battery models, which is an important direction for battery state estimation research. However, the relationships between variables in lithium-ion battery datasets are mostly nonlinear, and a single data-driven algorithm is susceptible to a weak generalization ability affected by the dataset itself. Meanwhile, most of the related studies on battery health estimation are offline estimation, and the inability for online estimation is also a problem to be solved. In this study, an integrated learning method based on a stacking algorithm is proposed. In this study, the end voltage and discharge temperature were selected as the characteristics based on the sample data of NASA batteries, and the B0005 battery was used as the training set. After training on the dataset and parameter optimization using a Bayesian algorithm, the trained model was used to predict the SOH of B0007 and B0018 models. After comparative analysis, it was found that the prediction results obtained based on the proposed model not only have high accuracy and a short running time, but also have a strong generalization ability, which has a great potential to achieve online estimation.

Transitional Strategies of Juvenile Green Sturgeon from a Riverine to a Brackish Water Environment

Information on habitat transitions is critical to understand whether efforts to manage the freshwater phase of juvenile green sturgeon (Acipenser medirostris) rearing habitats are feasible or beneficial. We implanted microacoustic transmitters in naturally produced age-0 juvenile green sturgeon in the Sacramento River to evaluate residency, general spatial distribution, movement rates, and downstream migration patterns over 300 river kilometers. Furthermore, we investigated whether changes in three environmental variables (discharge, turbidity, and water temperature) were associated with the beginning of movements resulting in the transition from riverine to brackish waters during their outmigration to the Sacramento-San Joaquin Delta Estuary. We captured 183 juvenile green sturgeon by trawl of which 88 were implanted with microacoustic tags. An additional 10 individuals were collected and tagged from the Red Bluff Diversion Dam rotary-screw traps. Linear mixed models showed that individuals caught by trawl had longer upper river residence times, post-tagging, than those caught by trap. Intergate velocity models showed that trap-caught individuals relocated at higher upper river reach velocities than trawl-caught fish, but there were no differences between trap- and trawl-caught fish within the middle or lower reach. Detections showed that juvenile green sturgeon began the downstream transition to brackish water habitat when discharge and turbidity increased. Temperature was not found to significantly influence the initiation of downstream migration. Both continuous and stepped downstream migration patterns were observed in each of the four cohorts, with smaller individuals being more likely to exhibit stepped migration. These data provide information that was previously unknown about the life history of the southern distinct population segment of the North American green sturgeon and can be utilized to assist with water resource management and recovery of this threatened fish species.

Experimental investigation of the external load effect on thermoelectric generator discharge time in a low power energy harvesting system

Thermoelectric generator systems are often evaluated and studied in open circuit and close circuit modes. In the open circuit case, minimum heat flux passes across the thermoelectric module and the module does not have any thermal losses. Moreover, in the close circuit system, the external consumer is connected to the module and higher heat is pumped from its hot side to cold side. Hence, investigating the effect of external load resistance as the consumer connected to the module on its response is a significant issue in thermoelectric systems. In this study, to evaluate the effect of various consumers (4, 8, 10, 15, 20 and 30 Ω) over the module on discharge time, output voltage and temperature on both sides of the module, thermoelectric systems lacking and containing phase change material as the useful means for energy storage and thermal management of thermoelectric system were designed and exposed to constant heat loads. Results of this study show that the power consumption of the internal resistance of the module (connected to the consumer) led to an increase in the temperature of both sides of the module compared to open circuit systems. Therefore, the thermal balance and temperature distribution over the module changes and more affected. The maximum output power and discharge time were obtained at the external resistance of 4 Ω (close to the average internal resistance of the module) in the studied systems. The phase change material prevented excessive temperature on the hot side during the charging process and provided proper thermal management to enhance voltage generation and discharge time. The thermoelectric generator is an effective technology in starting consumers with low resistance, such as light bulbs and remote controls.

Integration of deep learning and improved multi-objective algorithm to optimize reservoir operation for balancing human and downstream ecological needs

Dam (reservoir)-induced alterations of flow and water temperature regimes can threaten downstream fish habitats and native aquatic ecosystems. Alleviating the negative environmental impacts of dam-reservoir and balancing the multiple purposes of reservoir operation have attracted wide attention. While previous studies have incorporated ecological flow requirements in reservoir operation strategies, a comprehensive analysis of trade-offs among hydropower benefits, ecological flow, and ecological water temperature demands is lacking. Hence, this study develops a multi-objective ecological scheduling model, considering total power generation, ecological flow guarantee index, and ecological water temperature guarantee index simultaneously. The model is based on an integrated multi-objective simulation-optimization (MOSO) framework which is applied to Three Gorges Reservoir. To that end, first, a hybrid long short-term memory and one-dimensional convolutional neural network (LSTM_1DCNN) model is utilized to simulate the dam discharge temperature. Then, an improved epsilon multi-objective ant colony optimization for continuous domain algorithm (ε-MOACOR) is proposed to investigate the trade-offs among the competing objectives. Results show that LSTM _1DCNN outperforms other competing models in predicting dam discharge temperature. The conflicts among economic and ecological objectives are often prominent. The proposed ε-MOACOR has potential in resolving such conflicts and has high efficiency in solving multi-objective benchmark tests as well as reservoir optimization problem. More realistic and pragmatic Pareto-optimal solutions for typical dry, normal and wet years can be generated by the MOSO framework. The ecological water temperature guarantee index objective, which should be considered in reservoir operation, can be improved as inflow discharge increases or the temporal distribution of dam discharge volume becomes more uneven.

1T-VS2@V2O3 Synergistic Nanoarchitecture-Based Lamellar Clusters as the High Conductivity Cathodes of Thermal Batteries.

Thermal batteries are solid-state, thermally activated batteries with long storage times and high reliability. FeS2 is used as a cathode material commonly, but the high internal resistance and low voltage platform limit the improvement of battery performance. Herein, the 1T-phase vanadium disulfide (VS2) is prepared via the scalable hydrothermal method and applied to thermal battery cathode materials for the first time. 1T-VS2 lamellar flower clusters have high electronic conductivity (1.583 S cm-1) at room temperature, which is 75 times higher than FeS2 (0.021 S cm-1). Mechanism analysis shows that 1T-VS2@V2O3 can be formed based on the part of 1T-VS2 being oxidized to V2O3 at the discharge temperature. Benefiting from the synergistic effect of vanadium sulfide and vanadium oxide as a cathode for thermal batteries enhanced specific capacity (292.4 mA h g-1) and mass energy density (572.5 W h kg-1) when cutoff voltage is 1 V. Additionally, the discharge results indicate that the cells utilizing 1T-VS2 cathodes provided a higher voltage platform of 2.11 V than 1.84 V for FeS2. This impressive work can offer a good strategy for boosting cathode materials for a high-performance thermal battery.

Rainfall-Riverflow Trends of Enyong Creek in Akwa Ibom State, Nigeria

Rainfall-riverflow is crucial for effective hydrology and water resource management. Hence, the objective of this study was to evaluate the rainfall-riverflow trends of Enyong Creek in Akwa Ibom State, Nigeria, utilizing daily hydro-meteorological data of daily rainfall, river discharge, and temperature data collected from the period 2018 to 2023 and modeling the data by Vector Autoregressive (VAR) models. The results show that the VAR model successfully captured the dynamic relationships among water discharge (WD), rainfall (RF), and average temperature (AVE.TEMP). Equations revealed the influence of past values on the current state of each variable. Correlation matrix and graphical representations confirmed model adequacy. Validation results demonstrated the model's accuracy, with model R-squared value of 0.8781 indicating a strong correlation. The performance measurement of evaluation for the developed model showed a Mean Average Error (MAE), Root Mean Square error (RMSE), and Mean Absolute Percentage Error (MAPE) values of 5.5066, 6.7831, and 7.4203 respectively, revealing a satisfactory accuracy and precision. Information derived from this study offers valuable insights for government officials, policymakers, and planners in accurate flood forecasting, emergency management, land use planning, and infrastructure development.

Experimental investigation of air-conditioning electrical compressor using binary TiO2–SiO2 polyol-ester nanolubricants

As electric vehicles (EVs) continue to replace conventional gasoline vehicles, maintaining thermal comfort within the car requires additional energy to operate the automotive air-conditioning (AAC) system. This work aims to optimise the electrically driven compressor (EDC) system utilising polyol-ester (POE)-based binary nanolubricants to enhance performance and minimise the size of the EV battery and AAC components. A binary nanolubricant was formulated using a two-step method of formulation. The TiO2–SiO2/POE binary nanolubricant was prepared at different volume concentrations ranging from 0.01 to 0.1 %. The experiment was conducted for the 1200–3840 rpm compressor speed with different initial refrigerant charges between 120 and 160 g. The heat absorption rose by up to 44.2 % while utilising the binary nanolubricant at a volume concentration of 0.03 %. The coefficient of performance (COP) reached its maximum value of 2.43 at a refrigerant charge of 160 g and compressor speed of 1860 rpm. Furthermore, the binary nanolubricant significantly reduced the expansion valve discharge temperature, exhibiting a substantial decrease of up to 51.6 %. The highest COP increment, up to 23.4 %, was achieved at a volume concentration of 0.03 %. Hence, it is recommended to utilise 0.03 % TiO2–SiO2/POE binary nanolubricant to achieve optimal performance in the AAC-EDC system.

Innovative arrangement of circular angled fins for maximizing the discharge performance of triple-tube heat storage systems

Abstract This study introduces a novel triple-tube latent heat storage system enhanced with circular angled fins to improve solidification and heat recovery performance. The fins are arranged in staggered pattern with alternating upward and downward orientations on both sides of the PCM shell. A validated numerical model was developed using the enthalpy method to simulate the intricate heat transfer and phase change physics. Effects of circular fins geometry and operating conditions were systematically quantified on discharge rates and temperature uniformity. Four fin dimension cases (thickness × length): (2 × 5), (1 × 10), (0.66 × 15), and (0.57 × 17.5) mm2 were analyzed. The results demonstrate that fins with greater length and reduced thickness exhibit superior performance due to enhanced heat transfer capabilities, resulting in quicker solidification and faster heat retrieval. The longest 17.5-mm fins, achieving full solidification in 1973 s with 44%, 19%, and 1.9% quicker than cases with 5-mm, 10-mm, and 15-mm long fins, respectively. Incorporating an additional fin upward further reduces the solidification time by 4.5% while improving heat recovery by 3.6%. The 17.5-mm long fins increase heat discharge by 48% and outlet heat-transfer fluid temperatures by 39% versus straight fin baselines. Lower inlet heat-transfer fluid temperatures (10°C vs 20°C) reduce PCM solidification times by 31% (1755s vs 2554s) while increasing heat recovery rates by 57% (56.3 W vs 35.8 W). Overall, the integrated angled fins create a customizable latent heat storage system with greatly intensified heat transfer and thermal performance compared to conventional shell-and-tube arrangements.

Theoretical analysis of R1234yf and R1234yf/R125 mixture as replacement of R134a in vapor compression system

Abstract In this article, in order to reduce the climate hazards caused by global warming, a new environmentally friendly mixed refrigerant, R1234yf/R125 (with a mass ratio of 95:5), is introduced. Alongside R1234yf, the article conducts theoretical research to assess the feasibility of substituting R134a in vapor compression systems. The results show that coefficient of performance (COP) and compressor discharge temperatures of R1234yf and R1234yf/R125 are ~5.5% and 11°C lower than those of R134a, respectively. The volumetric cooling capacity of R1234yf is on average 8% smaller than that of R134a. The volumetric cooling capacity of R1234yf/R125 is similar to that of R134a, making it highly suitable for direct charging. R1234yf/R125 is basically nonflammable, with a minimal temperature glide, ozone depletion potential of 0 and a global warming potential of 144. It adheres to F-gas regulations and serves as an outstanding replacement for R134a.

Hybrid battery energy storage for light electric vehicle — From lab to real life operation tests

The aim of the research presented in the paper is to improve the lifetime of lead-acid battery systems which are widely used in low-speed electric vehicles or utility vehicles, since the cycle life of lead-acid batteries is nonlinearly dependent on the depth of discharge and electrolyte temperature. The solution proposed here is to connect lead-acid batteries with a small lithium‑iron-phosphate battery using only a diode. This connection is simple and does not require the use of an actively controlled converter. The concept was tested at various levels of an experiment, from the initial calculation of cycle life improvement and simulation, through a laboratory experiment, all the way to operational environment tests. The results obtained confirmed the main assumptions of the study: decrease in the depth of discharge of lead-acid battery for the distance traveled of around 17 %—which would translate into a 30 % better cycle life according to the characteristics indicated by the producers—and decrease in the root mean square and maximum current values of lead-acid battery by around 40–50 % and 26 %, respectively. Range extension was also achieved in vehicles. The solution has been successfully introduced to the market and is now used in few light electric vehicles.

Numerical simulation of integrating an air conditioner with an evaporative air cooler

During the summer, air conditioning is increasingly used in commercial and residential structures to provide thermal comfort. The elevated condenser pressure caused by high ambient temperatures has led to a significant increase in electricity consumption in dry, hot climates. Therefore, this article presents the results of a numerical simulation investigation into the feasibility of enhancing the performance of a conventional air conditioning unit by applying a direct evaporative cooling system. The objective is to increase the cooling capacity while decreasing power consumption. The program used a small window-type air conditioner configured to simulate various weather conditions. The numerical findings indicate that incorporating evaporative cooling aids improved the system's ability to overcome numerous obstacles, resulting in a 10–20% increase in refrigeration capacity. Additionally, power consumption was reduced by approximately 3%, and the discharge temperature fell by 6–10°C. The predicted mean vote standard (PMV) for thermal conditions for human occupants yielded favorable outcomes (normal-type). Despite the challenging climate conditions prevailing during the five sweltering summer months, water production demonstrated good results, particularly in September.

An equivalent circuit approach for remnant thickness evaluation and flaw sizing using pulsed thermography

Active thermography using pulsed heating is a fast and reliable method for detecting flaws in composite and metallic materials. This paper analyzes the temperature decay that occurs immediately after flash heating the front surface of stainless steel specimens as a function of time, based on a novel application of the equivalent circuit approach (ECA). The temperature decay from the front surface is equated to the discharge of a capacitor. The ECA is based on the charging (temperature rise due to flash heating) of a capacitor, followed by its discharge (temperature decay) through a series of resistors (which depends on the conductivity of the material) and capacitance (which depends on the thermal capacitance of the layers) through which the heat is dissipated. The proposed approach analyzes the sequences of temperature data obtained at each pixel location during cooling from a step wedge and a specimen with multiple flat-bottom holes. Time constant maps derived from the analysis are used to ascertain the thickness of the step wedge, detect the flaws, and evaluate the remnant thickness of the flaws. A correlation has been established between the thickness and the time constants. The above approach has been used to estimate the diameter of the flat-bottom holes.

Teorijska analiza niskozapaljivih i ekološki prihvatljivih smjesa ukapljenog naftnog plina i tetrafluoretana kao hladila

Liquefied petroleum gas (LPG), like other hydrocarbon gases, has good thermo-physical and ecological properties, but its high-flammability has limited its direct use in refrigeration applications. Therefore, this paper investigates the thermodynamic performance of low flammable and ecological-save mixtures of LPG and tetrafluoroethane refrigerant in a refrigeration system. The computational results of global warming potential (GWP) and low flammability limit shown that the blends with 50 – 90 % LPG contents have GWP below 750 and fall within the lower flammability safety class of which five were selected for further analysis. The results showed that the thermal conductivity and the refrigerating effects produced by the selected blends are greater than those of the reference refrigerant (R134a). Also, the selected blends exhibited appropriate lower pressure ratio, discharge temperature and specific power than R134a refrigerant. Four of the blends required low power input and exhibited higher coefficient of performance which are clear indication that they are more energy efficient than R134a in the refrigeration systems.

Experimental research on off-design characteristics of heat pump water heater using low GWP zeotropic blend

Based on the test setup of instant heat pump water heater (IHPWH), the performances of system operating with zeotropic natural mixture (ZNM) (R744/R290 (12/88)) and system operating with R22 refrigerant were compared under variable entry temperature of heat sink (ETHSK) and variable entry temperature of heat source (ETHSC) conditions, aiming to comprehensively evaluate the replacement potential of ZNM in the IHPWH. The results revealed that ZNM had an obvious alternative advantage, mainly attributed to that system operating with ZNM refrigerant achieved the comparable or markedly superior heating capacity and COP and markedly lower discharge temperature compared to those of system operating with R22 refrigerant under two conditions. The discharge temperature of system operating with ZNM refrigerant was reduced by 5.4~26.7? compared to that of system operating with R22 refrigerant, thus system operating with ZNM refrigerant can produce higher temperature domestic hot water. Compared with those of system operating with R22 refrigerant, both heating capacity and COP of system operating with ZNM refrigerant had markedly different trends with the change of ETHSK, while they had slightly different trends with the change of ETHSC. Compared to the ETHSK, the ETHSC has a more conspicuous impact on the heating capacity, COP and discharge temperature of system operating with ZNM refrigerant.

Анализ основных направлений снижения интенсивности массовых потоков рабочего тела через неплотности рабочей камеры поршневой длинноходовой тихоходной компрессорной ступени

The working processes and integral characteristics of piston long-stroke low-speed compressor stages are considered. Well-known technologies for increasing the feed rate are considered as objects of comparison: selection of the main dimensions and parameters of the stage; changing the size and design of valves, using elastomeric structural materials; change in the design of the cylinder-piston seal; changing the layout of the suction valve in the working chamber. Indicator efficiency, supply coefficient and tightness coefficient, as well as discharge temperature are considered as integral indicators. The following independent parameters are considered: parameters of the state of the working fluid at suction, discharge pressure, main dimensions and parameters of the stage, distance from the suction valve to the top dead center, seat diameters of the suction and discharge valves, as well as physical and mechanical properties of structural materials. A comparative analysis of the efficiency of the working process of the stage under consideration is carried out using various technologies for reducing the intensity of mass transfer through leaks in the working chamber of a low-speed, long-stroke piston stage. An assessment is made of the achievable value of the feed coefficient with the combined use of various technologies. The features of the working processes of the object under consideration and the relationship between the intensity of mass flows of working gas through leaks in the working chamber of the stage and the technologies used have been studied. The presented results of the theoretical analysis reflect the nature of the change in the integral characteristics of the stage depending on the technologies used to reduce the intensity of mass transfer through leaks in the working chamber of the stage under consideration.

Thermodynamic Analysis of Comprehensive Performance of Carbon Dioxide(R744) and Its Mixture With Ethane(R170) Used in Refrigeration and Heating System at Low Evaporation Temperature

Abstract In this paper, the system performance of R744 and R744/R170 mixed refrigerants used in a single-stage compression transcritical cycle at low evaporation temperature was studied by simulation method, and the effect of evaporation temperature, outlet temperature of gas cooler, R170 ratio on coefficient of performance (COP), discharge temperature, optimal pressure, and compression ratio were analyzed. The results show that Popt increases and decreases with the increase of outlet temperature and evaporation temperature of gas cooler and increases first and then decreases with the increase of R170 proportion. In the heating system, the maximum and minimum Popt of R744/R170 (25/75) were 1.35 MPa, 3.6 MPa, and 2.6 MPa and 1.23 MPa, 2.93 MPa, and 1.87 MPa lower than that of R170 (0%, 22.4%, and 50%); compared to pure R744, the system pressure of the mixed R744/R170 is lower. The COPe and COPh increase with the increase of evaporation temperature and decrease with the increase of outlet temperature of the gas cooler. With the increase of R170 proportion, they first decrease and then increase; the maximum COPe and COPh of R744 were 22.4%, 29.6%, and 21.2% and 10.3%, 13.8%, and 10.8% higher than those of R170 at 22.4%, 50% and 75%, respectively.

Experimental study on refrigeration system’s performance of the refrigerator truck using R404A refrigerant

A refrigerated system experimental bench using R404A as the refrigerant was built to address the current issues of high compressor discharge temperature and poor refrigeration performance of refrigerated systems for cold storage. The effects of compressor speed and temperature changes within the storage on the main refrigeration performance parameters of the system were studied and analyzed. The results show that when the rotational speed is increased from 2500-4500 rpm under the conditions of 32?C outside and 0?C inside, the highest system exhaust temperature is 84.3?C, which is lower than 90?C, and the maximum system COP is 3.86, and when the compressor speed is increased from 3500 rpm under the conditions of -5?C to 5?C, the system exhaust temperature is lower than 90?C. The COP can reach 2.74, especially at -5?C.

Influence of compressor speed on the performance of low pressure vapor-injected refrigeration systems

For the problems of high compressor discharge temperature and system performance decay during the operation of cold storage, a parallel flow heat exchanger based low pressure make-up gas refrigeration system experimental bench was designed and built, and the changes of refrigeration system performance were analyzed under different compressor speeds. The results show that when the compressor speed increases from 2500 rpm to 4500 rpm, the compressor discharge temperature increases, the refrigeration capacity increases by 39.53% and the compressor power increases by 38.89%, in addition, as the speed increases, the system COP shows a trend of first increasing and then decreasing, with the best value of 2.71 at 3500 rpm.

Теоретическая оценка эффективности применения одноступенчатых длинноходовых поршневых компрессоров в холодильной технике и системах сжижения углеводородов

The analysis of the main modern technologies for obtaining low temperatures and liquefying hydrocarbons using compressor equipment is presented and the most significant results of research in the field of low-flow compressors based on low-speed, long-stroke piston stages are presented. A method for calculating an ideal vapor-compression refrigeration cycle is presented, adapted to the object under consideration, taking into account the possibility of implementing quasi-isothermal compression. A comparative computational analysis of temperature conditions and thermodynamic efficiency of a two-stage refrigeration cycle and single-stage refrigeration cycles is carried out during adiabatic and quasi-isothermal compression processes in the boiling temperature range 278 K ... 198 K. It is shown that in terms of the discharge temperature and coefficient of performance, a single-stage vaporcompression ammonia refrigeration machine based on a low-speed quasi-isothermal stage is comparable to a similar two-stage machine based on adiabatic stages. This allows, in relation to actual objects — small refrigeration machines and installations, to predict both the energy and technical advantages of using a single-stage scheme based on low-speed, long-stroke piston compressors. In addition, it has been shown that the effective use of such a compressor is also possible in hydrocarbon liquefaction systems, while ensuring their safe temperature conditions in a wide range of atmospheric temperatures.

Geochemistry of lanthanides in thermal waters of Issyk-Kul Lake Basin

The distribution and abundance of lanthanides in thermal waters of the northern Tien Shan (Issyk-Kul lake basin) were studied. Waters are represented by three types: Na-Cl-SO4-HCO3, Na-Ca-Cl-SO4 and Na-Ca-Cl, demonstrates alkaline pH (7.3–9.7) and Eh from -260 to +98 mV. Discharge temperature varies from 15 to 50oC, and total dissolved solids from 0.2 to 13.0 g/l. It is established that lanthanides (or rare earth elements, REE) concentrations vary from 0.07 to 0.81 ppb, the maximal concentrations relate to a Na-Ca-Cl water type, which demonstrates the influence of reverse ion exchange. The total concentration of rare earth elements roughly increases as pH decreases, implying that the absolute abundance of REE is totally controlled by pH conditions. The ΣREE concentrations in groundwater exhibit a high positive correlation (R=0.8) with the total dissolved solids contents indicating that ΣREE are well related to the salinity of the thermal water samples. The major ions HCO3, SO4, Ca, K, and Mg have minor associations with REE. The geochemical and geological data suggest that the principal REE source of the thermal waters is bedrock mineralogy and lithology. The distribution and abundance of REE in thermal waters of Issyk-Kul basin were studied for the first time.