Low-temperature Cycle Research Articles

Designing on solvent composition of dual-salt low concentration electrolyte for inhibiting lithium dendrite growth at −20 ℃

Lithium metal batteries (LMBs) are expected to become a new generation of energy storage technology based on the high theoretical specific capacity and low potential of lithium metal anode. In order to promote the commercial application of LMBs, lithium dendrite has become an urgent issue to be resolved to improve the battery safety. Since temperature is a key factor on dendrite growth kinetics, it is of great significance to design novel electrolytes for LMBs to inhibit lithium dendrite growth at low temperature conditions. In this work, γ-butyrolactone (GBL) with low melting point, ethyl propanoate (EP) with high wettability and low viscosity, and fluoroethylene carbonate (FEC) with excellent film-forming performance are chosen as the electrolyte components (GBL/EP/FEC, 7:3:1 w/w/w). Lithium tetrafluoroborate (LiBF4) and lithium difluorophosphate (LiDFP) are used as dual salts to reformulate a low-concentration electrolyte (LCE) of 0.5 mol L−1 (M), i.e., 0.4 M LiBF4 + 0.1 M LiDFP. The solvent compositions of the LCE electrolyte are optimally designed for Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) cells, resulting in good low-temperature cycling performance without affecting the room-temperature performance. The electrolyte enables the Li||NCM811 cells to maintain both 97% capacity after 100 cycles at room temperature and obviously suppress lithium dendrite growth at −20 °C.

An application of conventional and advanced exergy approaches on a R41/R1233ZD(E) cascade refrigeration system under optimum conditions

Painstaking adjustment of an optimum low-temperature cycle (LTC) condenser temperature allows cascade refrigeration system (CRS) to operate at maximum performance. This study exhibits an original approach because, for the first time, advanced exergy analysis is implemented under an optimum LTC condenser temperature of CRS operating with R41/R1233zd(E) as an environmentally-friendly refrigerant pair. Under the auspices of advanced exergy analysis, there is endogenous exergy destruction of 50.43% and exogenous exergy destruction of 49.57% within total exergy destruction. It is pointed out that the interactions between the CRS components (external irreversibilities) are partly less than exergy destruction that occurs within components (internal irreversibilities). The avoidable part within total exergy destruction, which is greater than the unavoidable part, indicates that components have a high improvement potential with a value of 56.31%. Furthermore, LTC compressor depends significantly on other components, as it has the largest exogenous part of exergy destruction with 75.82%. The results indicate that the CRS’s exergy efficiency, which can be determined based on conventional exergy analysis, is only 36%. However, this increases to 68% with the improvements needed for the components.

Novel Design and Thermodynamic Analyses of Cascade Refrigeration System at Ultra-Low Temperature

In this study, a cascade refrigeration system comprising gas and vapor compression cycles operating at ultra-low temperature was designed. In the thermodynamic analyses, R744, R404A, and R410A refrigerants in the high temperature cycle (HTC), and R1150, R170, and R23 in the low temperature cycle (LTC) were used. Thermodynamic analyses were carried out using the Engineering Equation Solver package program. Outputs considered were: system performance(COP), compression ratio, mass flow ratio and HTC cascade outlet temperature. Results show that, at different LTC condenser temperature values, R404A/R23 has the highest COP value, in the LTC, R23 has the highest compression ratio, while R1150 has the lowest one, in the HTC, R404A has the highest compression ratio, while R744 has the lowest one, the performance of the system increased with the decrease of the mass flow ratio.

Experimental Analysis of the R744/R404A Cascade Refrigeration System with Internal Heat Exchanger. Part 2: Exergy Characteristics

This paper examines the exergy efficiency and exergy destruction rate of the R744/R404A cascade refrigeration system (CRS) using an internal heat exchanger in supermarkets according to various conditions affecting the system. A refrigerant of a low-temperature cycle uses R744 and a refrigerant of a high-temperature cycle in the CRS uses R404A. Experiments were conducted by changing various conditions on the high- and low-temperature side, and exergy analysis was performed accordingly. The main results are summarized as follows: (1) the lower the total exergy destruction rate of the CRS, the higher the exergy efficiency of the system, and accordingly the coefficient of performance (COP) of the system is also improved. (2) In the CRS, since the optimum cascade evaporation temperature exists (about −16 °C), it can be said that the limit point, that is, the cascade evaporation temperature with the maximum COP of the system, is the optimum point at about −16 °C. Therefore, at this optimum point, the exergy destruction rate of the cascade heat exchanger becomes the minimum. In other words, it should be noted that when the cascade evaporation temperature is the optimum point, the exergy destruction rate of the R744 compressor and the cascade heat exchanger is minimal. The purpose of this study is to provide basic design data by analyzing the exergy characteristics according to various conditions on the high- and low-temperature side for optimal design of a CRS to which R744 is applied.

EXPERIMENTAL EVALUATION OF A CASCADE REFRIGERATION SYSTEM USING R-134a AND R-404a

Cascade refrigeration system is an attractive technology for low-temperature requirement, allowing operation under these conditions with positive suction pressures and a moderate condensation pressure at ambient temperature. This work describes a performance analysis of a cascade refrigeration prototype equipped with hermetic compressors working with R-134a and R-404a as refrigerants, thermally connected by a tube-in-tube-type cascade-condenser. Energy flows and performance parameters were evaluated under different evaporating temperature conditions of the low temperature cycle (LTC). The results showed an increase in energy efficiency ratio (EER) and coefficients of performance (COP) of cascade system as well as of each cycle with the increase of LTC evaporating temperature, even with a simultaneous increase of temperature difference in cascade-condenser.

A Review on Recent Progress in the Integrated Green Hydrogen Production Processes

The thermochemical water-splitting method is a promising technology for efficiently converting renewable thermal energy sources into green hydrogen. This technique is primarily based on recirculating an active material, capable of experiencing multiple reduction-oxidation (redox) steps through an integrated cycle to convert water into separate streams of hydrogen and oxygen. The thermochemical cycles are divided into two main categories according to their operating temperatures, namely low-temperature cycles (<1100 °C) and high-temperature cycles (<1100 °C). The copper chlorine cycle offers relatively higher efficiency and lower costs for hydrogen production among the low-temperature processes. In contrast, the zinc oxide and ferrite cycles show great potential for developing large-scale high-temperature cycles. Although, several challenges, such as energy storage capacity, durability, cost-effectiveness, etc., should be addressed before scaling up these technologies into commercial plants for hydrogen production. This review critically examines various aspects of the most promising thermochemical water-splitting cycles, with a particular focus on their capabilities to produce green hydrogen with high performance, redox pairs stability, and the technology maturity and readiness for commercial use.

Effects of high–low temperature cycles on the performance of coral aggregate concrete based on field specimens and laboratory accelerated tests

In the high-temperature marine environment, breakwaters frequently suffer from high–low temperature cycles, which inevitably damages the performance of coral aggregate concrete (CAC). Based on field specimens and laboratory tests, in this research, the evolution of macroscopic and microscopic properties, as well as the crack density of CAC under high–low temperatures action were investigated, then the damage mechanism of CAC was revealed. The experimental results showed that the compressive strength of the specimens derived from the outside and top surface of on-site breakwater ranged from 24.07 to 55.48 MPa and from 26.26 to 43.41 MPa, respectively, and their splitting compressive strengths ranged from 1.29 to 4.65 MPa and from 1.68 to 4.49 MPa, respectively. In addition, fine cracks and swelling products can be found in the CAC. Under the indoor accelerated test of seawater cooling, the compressive strength of the indoor CAC developed in an increasing and then decreasing trend with the increase of the cycle period, whereas the splitting tensile strength kept developing in a decreasing trend, this was caused by the dual action of high–low temperatures cycles and sulfate erosion. Additionally, the interior of CAC also exhibited more calcium alumina, gypsum, and sodium sulfate crystal. Moreover, the addition of fly ash (FA), silica fume (SF), and polypropylene fiber (PF) can reduce the strength loss of CAC under high–low temperature cycles to some extent. The mathematical relationship between the relative dynamic elastic modulus of the CAC and the cycle period could be fitted by a quadratic polynomial (Erd = a + bt + 0.5ct2, R2 greater than 0.99).

Performance Analysis of a Novel Cascade Vapor Compression System for Small-Scale Desalination and Cooling

Abstract The demand for improving living standards has led to increasing freshwater consumption and comfort cooling, requiring significant performance improvements. In this regard, a novel and efficient cascade refrigeration system (CRS) for simultaneous generation of considerable freshwater and cooling effect is proposed. The system does not require dedicated components for desalinating seawater because it is a by-product of the proposed CRS. Utilizing the cascade configuration enhances energy efficiency by lowering the compression work while improving energy recovery by utilizing the heat rejected from the condenser of low-temperature cycle to vaporize seawater for desalination in the evaporator of the high-temperature cycle of the proposed cascade system. A mathematical model of the innovative system based on thermodynamic and economic principles has been developed and utilized to predict the proposed system's thermal performance and cost-savings. A comprehensive analysis has been conducted to study the effect of multiple parameters such as the evaporator, condenser, and brine boiling temperatures. The main studied parameters were coefficient of performance (COP), gain output ratio (GOR), freshwater production, and total cost-savings. For a 10 tons of refrigeration (TR) unit, the freshwater production was between 56.11 and 73.36 kg/h, with cost-savings reaching 2226 US$/year. It was found that the freshwater production increased with condenser and brine boiling temperature but decreased with evaporator temperature. The COP improvement can be as much as 26% over the reference cooling system without desalination.

Electrochemical and thermal characteristics of aging lithium-ion cells after long-term cycling at abusive-temperature environments

This work prepares five kinds of cell samples, i.e. the fresh cell, the cell degrades to 90% SOH (state of health) after high-temperature cycling, the cell degrades to 80% SOH after high-temperature cycling, the cell degrades to 90% SOH after low-temperature cycling and the cell degrades to 80% SOH after low-temperature cycling to reveal the electrochemical and thermal characteristics of the aging cells induced by abusive-temperature cycling. The cells under abusive-temperature environments show severe degradation behaviors over cycling, which may be mainly attributed to lithium inventory loss, anode material loss and electrode interface deterioration. Besides that, abusive-temperature cycling affects the thermal stability of positive electrode materials and single cells, and this is related with environmental temperatures. By comparison to the fresh cell, the thermal stability of the positive electrode materials and single cells after high-temperature cycling is improved, which is different from that of the low-temperature cycled ones who illustrate deteriorated thermal safety at elevated temperatures. Therefore, the thermal risk of aging cells after long-term low-temperature cycling is worthy of more concern, the according monitor and/or management of these cells during operation, transportation, storage and recycle, etc. should be valued.

Energy and exergy analysis of NH3/CO2 cascade refrigeration system with subcooling in the low-temperature cycle based on an auxiliary loop of NH3 refrigerants

This paper proposes a NH3/CO2 cascade refrigeration system that sets an auxiliary refrigeration loop in the high-temperature cycle to increase the subcooling degree in the low-temperature cycle (CRSS). Based on the basic principles of thermodynamics, a mathematical model is established and theoretical simulation is carried out to obtain the influence of key parameters on the cycle performance. Compared with the conventional cascade refrigeration system (CCRS), the conclusions find that there exists an optimal condensation temperature of low-temperature cycle (TMC.opt) to maximize COP. The maximum COP of CRSS is 4.58% higher than that of CCRS when the subcooling degree is 10 °C. The maximum exergy efficiency is 0.391, increasing by 4.40%. With the increase of the subcooling degree, both the COP and the TMC.opt of CRSS increase. When the subcooling degree increases from 5 °C to 15 °C, the performance increment increases from 2.73% to 6.00%. When the evaporation temperature of the system changes, both the COP and exergy efficiency decreases slightly and it is found that the performance is better when the evaporation temperature is lower when condensation temperature is kept constant. Besides, the discharge temperature of the NH3 compressor in CRSS can be reduced by 9.9 °C when the evaporation temperature is −30 °C.

Performance evaluation of NH3/CO2 cascade refrigeration system with ejector subcooling for low-temperature cycle

An NH3/CO2 cascade refrigeration system with ejector subcooling (ESCRS) is proposed in this paper. Based on the basic principle of thermodynamics, the mathematical model of the refrigeration system is established and thermodynamic analysis is carried out to obtain the influence of main working parameters on system performance. Compared with the conventional cascade refrigeration system (CCRS), it is concluded that the performance of ESCRS is better than that of the CCRS. Within a certain range, the greater the subcooling degree, the more obvious the decrease of power consumption of low-temperature compressor, the greater the discharge temperature of NH3 compressor decreases, and the more obvious the increase of system COP and exergy efficiency. Under typical operating conditions, the COP and exergy efficiency of the system proposed in this paper is about 5.4% and 4.8% higher than that of the CCRS.

A Simulation Research on NH3/CO2 Cascade Refrigeration System Based on Theoretical Model

The rapid development of the refrigeration industry has benefited production and life, and has also brought irreversible negative impacts on the current environment. Finding environment friendly, energy-saving, stable, and new-type alternative refrigerants has become a common concern and research hot spot of researchers and the refrigeration industry around the world. In this article, a NH₃/CO₂ cascade refrigeration system model is established. CO₂ is used as the refrigerant in the low temperature cycle, NH₃ is used as the refrigerant in the high temperature cycle, and the condensing evaporator is used to couple the heat exchange between the high and low temperature circuits. Based on the first law of thermodynamics and the second law of thermodynamics, the author carries out the energy analysis and exergy analysis of the cascade system. Applying MATLAB software to establish the simulation calculation of NH₃/CO₂ cascade cycle. Through simulation, the author explores the effects of low temperature cycle CO₂ evaporation temperature and high temperature cycle NH₃ condensation temperature cycle parameters on the system cycle performance and system exergy efficiency. This paper provides a certain theoretical basis for improving the design of system structure and the system performance coefficient through simulation calculation.

Study on low-temperature cycle failure mechanism of a ternary lithium ion battery.

This study is focused on the changes in parameters such as discharge capacity, and the possible failure mechanism of a 25 Ah ternary lithium ion battery during cycling at −10 °C. A new battery and a battery after 500 cycles were disassembled. The morphology and structure of the cathode and anode electrodes were characterized. Transmission electron microscopy (TEM) and X-ray photoelectron absorption spectroscopy (XPS) were used to analyze the changes in the microstructure and chemical environment of the anode electrode interface. The results show that after 500 cycles at −10 °C, the capacity of the battery is only 18.3 Ah, and there is a large irreversible capacity loss. The battery samples after low-temperature cycling produced gas during storage at 25 °C. It is found that a large amount of lithium plating on the anode surface is an important factor for the reduction in battery capacity. The dissolution of transition metal elements in the cathode electrode and deposition on the anode electrode, and the catalytic decomposition of electrolyte at the anode interface are the main reasons for the gassing of the battery.

Bi-Functional Paraffin@Polyaniline/TiO2/PCN-222(Fe) Microcapsules for Solar Thermal Energy Storage and CO2 Photoreduction.

A novel type of bi-functional microencapsulated phase change material (MEPCM) microcapsules with thermal energy storage (TES) and carbon dioxide (CO2) photoreduction was designed and fabricated. The polyaniline (PANI)/titanium dioxide (TiO2)/PCN-222(Fe) hybrid shell encloses phase change material (PCM) paraffin by the facile and environment-friendly Pickering emulsion polymerization, in which TiO2 and PCN-222(Fe) nanoparticles (NPs) were used as Pickering stabilizer. Furthermore, a ternary heterojunction of PANI/(TiO2)/PCN-222(Fe) was constructed due to the tight contact of the three components on the hybrid shell. The results indicate that the maximum enthalpy of MEPCMs is 174.7 J·g−1 with encapsulation efficiency of 77.2%, and the thermal properties, chemical composition, and morphological structure were well maintained after 500 high–low temperature cycles test. Besides, the MEPCM was employed to reduce CO2 into carbon monoxide (CO) and methane (CH4) under natural light irradiation. The CO evolution rate reached up to 45.16 μmol g−1 h−1 because of the suitable band gap and efficient charge migration efficiency, which is 5.4, 11, and 62 times higher than pure PCN-222(Fe), PANI, and TiO2, respectively. Moreover, the CO evolution rate decayed inapparently after five CO2 photoreduction cycles. The as-prepared bi-functional MEPCM as the temperature regulating building materials and air purification medium will stimulate a potential application.

Design and Optimization of a Radial Inflow Turbine for Use with a Low Temperature ORC

This study aims to design and optimize an organic Rankine cycle (ORC) and radial inflow turbine to recover waste heat from a polymer exchange membrane (PEM) fuel cell. ORCs can take advantage of low-quality waste heat sources. Developments in this area have seen previously unusable, small waste heat sources become available for exploitation. Hydrogen PEM fuel cells operate at low temperatures (70 °C) and are in used in a range of applications, for example, as a balancing or backup power source in renewable hydrogen plants. The efficiency of an ORC is significantly affected by the source temperature and the efficiency of the expander. In this case, a radial inflow turbine was selected due to the high efficiency in ORCs with high density fluids. Small scale radial inflow turbines are of particular interest for improving the efficiency of small-scale low temperature cycles. Turbines generally have higher efficiency than positive displacement expanders, which are typically used. In this study, the turbine design from the mean-line analysis is also validated against the computational fluid dynamic (CFD) simulations conducted on the optimized machine. For the fuel cell investigated in this study, with a 5 kW electrical output, a potential additional 0.7 kW could be generated through the use of the ORC. The ORC’s output represents a possible 14% increase in performance over the fuel cell without waste heat recovery (WHR).

Design and Fabrication of Leadless Package Structure for Pressure Sensors

Abstract Silicon piezoresistive pressure sensors can only operate below 125 °C due to the leakage current of the PN junction. However, silicon-on-insulator (SOI) high-temperature pressure sensors use SiO2 for total dielectric isolation to solve this problem. At present, SOI high-temperature pressure sensors mostly use lead bonding package structure, with gold wire to lead the electrical signal and silicone oil as the protection medium, but the working temperature of silicone oil is limited to about 150 °C. In this paper, the leadless package structure is designed using pressure conduction on the backside of the chip and replacing the gold wire with sintered silver paste. The materials and dimensions of the leadless package structure are determined and then obtained a complete package structure through manufacturing. The reliability of the leadless package structure after silver paste sintering was verified by finite element analysis, and the results showed that the thermal stress caused by high and low-temperature cycles in the leadless package is minimal and does not affect the sensitivity of the pressure-sensitive chip. The size of the leadless package structure was optimized by Taguchi orthogonal method, and the maximum thermal stress was effectively reduced. Also, the key factors affecting the thermal stress of the leadless package in the package structure were identified by the variance number analysis method. The optimized leadless package structure size was remanufactured, and the sintered package structure was tested. The data show that the sensitivity of the pressure sensor is 30.82 mV/MPa with a nonlinearity of less than 0.4% full-scale (FS).

Analyzing the dual-loop organic rankine cycle for waste heat recovery of container vessel

Increasing the efficiency of ships via waste heat recovery systems is one of the most effective methods to minimize emissions from ships, especially carbon dioxide emissions. The organic rankine cycle is a promising system. The purpose of this study is to analyze the dual-loop organic rankine cycle system using jacket cooling water, exhaust gas and scavenge air. Two model is designed to analyze the waste heat recovery system for the different main engine load. In the first model, while the exhaust gas is used as the heat source in the high temperature cycle, jacket cooling water and high temperature loop waste heat are used as heat sources in low temperature cycle. Scavenge air and exhaust gas and jacket cooling water are used as heat sources in the second model. Different working fluid combinations that have been familiar from literature and their alternatives are analyzed in two models and the net power output by using thermodynamics, reduction in carbon dioxide and fuel consumption are calculated. In low engine load, since the temperature range of scavenge air is low the second model is suitable for high main engine load. Results show that with the second model when benzene-R245fa(1,1,1,3,3-pentafluoropropane) combination is used as working fluid, 3373 kW net power can be produced, 13588,3 tonnes/year Carbon dioxide emissions can be reduced. However, since benzene is a flammable fluid, it is not recommended for use in the ship. Instead of benzene, R1233zd(E) (trans-1-chloro-3,3,3-trifluoro-1-propene) is more suitable for high temperature source.

Energy, exergoeconomic and environmental optimization of a cascade refrigeration system using different low GWP refrigerants

Due to the environmental concerns, refrigerants with low global warming potential (GWP) are good alternatives to use in the most refrigeration system. In this paper, an energy-exergoeconomic-environmental model is presented for a cascade refrigeration system (CRS) at high and low temperature cycles operating with six pairs of refrigerants with low GWP including R41-R161, R41-R1234yf, R41-R1234ze, R744-R161, R744-R1234yf, R744-R1234ze. The optimal performance of the system is studied under the effects of temperature variations in condenser, evaporator and cascade heat exchanger. To do this, the coefficient of performance (COP), exergy efficiency and total cost rate are optimized for each pair of refrigerants to evaluate the optimal operational conditions of CRS using Pareto front curve. Results show that the maximum COP of 2.09 and maximum exergy efficiency of 35.32% are obtained at condenser temperature of 40 °C and evaporator temperature of − 30 °C. In addition, the minimum total rate cost is equal to 13587 $/year when the condenser temperature is 40 °C and evaporator temperature is 32.5 °C. Finally, it is concluded that R41-R161 and R41-R1234ze are optimal refrigerant pairs with the highest COP/exergy efficiency and lowest total cost rate.

Optimization of supercritical carbon dioxide based combined cycles for solid oxide fuel cell-gas turbine system: Energy, exergy, environmental and economic analyses

Among various supercritical carbon dioxide cycles, the supercritical recompression carbon dioxide cycle can well adapt to the high temperature of the exhaust gas of the solid oxide fuel cell-gas turbine system to augment power generation. Nevertheless, even after the recovery by the supercritical recompression carbon dioxide cycle, the exhaust gas still contains a large amount of unutilized waste energy. Few studies introduce low-temperature cycles to build cascade cycle systems, which are very likely to address this issue effectively. From the perspectives of energy, exergy, environmental and economic indexes, this article analyzes and compares the improvement potential of integrating four common low-temperature cycles, including organic Rankine cycle, transcritical carbon dioxide cycle, Kalina cycle, and organic flash cycle. Different key operating parameters are considered in-depth and optimized by a genetic algorithm. The results illustrate that in terms of efficiency, the introduction of the organic Rankine cycle is the most outstanding since it can reach the highest energy efficiency of 72.74–73.55% (exergy efficiency of 70.22–71.01%) across wide operation conditions. In terms of cost, the coupling of Kalina cycle is suggested due to the lowest capital cost of 19.94 $/h. The environmental penalty of the four systems all accounts for 14.73% of the total cost. As a consequence, the pros and cons of four common low-temperature cycles are fully demonstrated, which can provide references for the power plant planning.

Experimental Analysis of the R744/R404A Cascade Refrigeration System with Internal Heat Exchanger. Part 1: Coefficient of Performance Characteristics

This study evaluates the performance of an R744/R404A cascade refrigeration system (CRS) with internal heat exchangers (IHE) in supermarkets. R744 is used as the refrigerant in a low-temperature cycle, and R404A is used as the refrigerant in a high-temperature cycle. In previous studies, there are many studies including theoretical performance analysis of the CRS. However, experimental studies on the CRS are lacking, and experimental research on the R744/R404A system with an IHE is scarce. Therefore, this study provides basic data for optimal refrigeration system design by experimentally evaluating the results of modifying various parameters. The operating parameters considered in this study include subcooling and superheating, condensing and evaporating temperature, cascade evaporation temperature, and IHE efficiency in the R744 low- and R404A high-temperature cycle. The main results are summarized as follows: (1) By applying the results of this study, energy efficiency is achieved by optimizing the overall coefficient of performance (COP) of the CRS, and the refrigerant charge of the R404A cycle is minimized and economic efficiency is also obtained, enabling operation and maintenance as an environment-friendly system. (2) When designing the CRS, finding the cascade evaporation temperature that has the optimum and maximum COP according to the refrigerant combination should be considered with the highest priority.