Energy Conversion Cycle Research Articles

High Energy Conversion Efficiency and Cycle Durability of Solar-Powered Self-Sustaining Light-Assisted Rechargeable Zinc–Air Batteries System

The issue of energy supply in outdoor and remote areas has become a significant challenge. Solar-powered self-sustaining rechargeable zinc-air batteries (RZABs) offer a viable energy solution for off-grid regions. However, there has been no specific study on the technical compatibility and adaptability of the solar power generation system and RZABs system, as well as the efficiency of energy conversion and storage in such solar-powered RZABs systems. To address these challenges, this study developed a solar-powered self-sustaining photo-assisted RZABs system based on a photo-responsive polyterthiophene (pTTh) cathode. This system employs pTTh with photo-responsive properties as the cathode catalyst for RZABs, which not only significantly reduces the overpotential of the cathode but also enhances the performance of the RZABs and the overall energy conversion efficiency (reaching 16.2%). In practical applications, the system exhibits excellent stability, operating continuously within a wide temperature range of -15 to 40°C, and demonstrating a stable cycling operation capability of up to 33 days. It provides reliable, low-cost power support for electronic devices such as mobile phones, flashlights, GPS units, and small pollutant detection systems, greatly improving the practicality of these devices in off-grid areas.

Performance analysis and multi-objective optimization of the offshore renewable energy powered integrated energy supply system

Offshore renewable energy technologies offer a promising prospect for energy supply on offshore islands. However, traditional wind and solar energy sources exhibit strong variability and cannot fully meet the energy demands of users. At the same time, the energy demand of users also has great volatility, so the supply side and demand side of energy cannot match well. Existing renewable energy systems often utilize thermal power generation as a stabilizer for the system, however, this approach is difficult to apply in offshore conditions. This study introduces an innovative multi-energy complementary system that integrates seawater freezing desalination, refrigeration and power-hydrogen-ammonia co-generation, driven by ocean thermal energy, wind energy, and solar energy. The system incorporates the use of a new developed small temperature difference ejector refrigeration cycle to stabilize the entire system and produce low-temperature refrigeration. By utilizing the seawater freezing desalination process to minimize energy conversion losses and balancing fluctuations in multiple energy inputs and user demands through ammonia-hydrogen co-production, this approach effectively minimizes energy waste, enhances energy utilization efficiency, and reduces excess power handling. The purpose is to optimize the configuration of the energy conversion subsystem within the multi-energy complementary multi-effect co-generation system, thus improving the economic feasibility and reliability of the system in providing energy and freshwater supply, ultimately achieving the goals of reducing energy waste, achieving high conversion efficiency, and minimizing equipment investment. This study conducts an economic analysis and optimization of a multi-energy complementary system, utilizing a 2 MW-level OTEC subsystem as a stabilizer. Both equipment investment and operating costs are considered in the economy analysis. The carbon emission reduction performance of this system is evaluated. The performance optimization results show that the system achieves an energy storage efficiency of 65.96 %, and the curtailment rate of this system is only 3.99 %, significantly lower than the 10 % curtailment rate in traditional system. The proposed system can meet the annual electricity demand of 33.09 million kWh, as well as a cooling demand of 546.81 million kWh. Under typical conditions, the ocean thermal energy conversion cycle exhibits a power efficiency of 0.85 % and a refrigeration efficiency of 29.10 %. Meanwhile, it annually reduces CO2 emissions by 2.54 million tons, demonstrating significant environmental benefits. This proposed system is mainly applicable to tropical waters with high surface water temperatures and depths of no less than 600 m worldwide. This study offers a practical and economically beneficial solution for energy and freshwater supply on offshore islands.

Performance analysis of heat pump polygeneration system

A heat pump polygeneration system is a promising technology to meet daily needs such as drinking water, power, space cooling or heating, and hot water generation. This work is focused on integrating the solar heat pump and two-stage humidification–de-humidification with a minimum space requirement. In this integrated cycle, the desired outputs i.e. condenser heat and evaporator heat are used for maximizing hot water and desalinated water production with minimal thermal pollution. For warm or hot air generation, an air reheater device is used after the heat pump. By using the switching operation, the air reheater is used accordingly as per climatic conditions. So in this integrated cycle, a coconut coir-packed humidifier is used for the humidification process, and a water-cooled heat exchanger and heat pump evaporator are used for the dehumidification process to meet the desired outputs from the system. The MATLAB simulation tool is used to simulate the thermodynamic model of the integrated cycle, and it is focused on studying the effect of mass flow rate, atmospheric temperature, relative humidity, evaporator temperature, and hot/cold water temperature, on outputs, as well as the energy conversion factor of the plant and cycle. At 25°C ambient air temperature, the energy conversion factor of the plant and cycle are 0.866 and 2.2, respectively. Similarly, at 75% humid air and 35°C surrounding air temperature, the gained output ratio and coefficient of performance are 4.03 and 1.964, respectively. And also, the plant and cycle energy conversion factors are 0.903 and 2.4.

Performance prediction and loss evaluation of the carbon dioxide supersonic nozzle considering the non-equilibrium condensation

Carbon dioxide (CO2) is being considered as a promising working medium in energy conversion and refrigeration cycles due to its unique properties. When carbon dioxide flows with supersonic in turbo machinery (compressor), the non-equilibrium effect is enhanced due to the large change of fluid velocity, resulting in non-equilibrium condensation of the blade, which will seriously affect the performance of the compressor. Considering the similarities in flow characteristics between the nozzle and the compressor blade, the condensing flow of the blade can be predicted by simulating in a nozzle. The real gas model is used. The pressure and the nucleation rate are predicted based on the modified model, and the flow losses and thermal efficiency are analyzed in different states. The results show that the pressure variation in the nozzle aligns well with the experimental data. When the fluid transitions from subcritical to supercritical, the condensation interval decreases and the peak of the nucleation rate increases. The maximum supercooling decreases gradually. The flow losses are relatively large, and the thermal efficiency is low.

Effects of nonlinear thermal radiation on magnetized - nanofluid flow through an inclined microporous channel: An investigation of second law analysis.

This study aimed at studying the variational effect of nonlinear thermal radiation on the flow of Casson nanofluid ( ) through a porous microchannel with entropy generation. The novelty of this investigation includes the incorporation of porous media, nonlinear radiative heat flux, and convective heat transfer at the channel interface into the energy equation, which results in an enhanced analysis for the cooling design and heat transfer of microdevices that utilize nanofluid flow. Particularly, alumina ( ) is considered as the nanoparticles in this blood base fluid due to associated advanced pharmaceutical applications. With dimensionless variables being utilized, the governing equationsare minimized to their simplest form. The Chebysev-based collocation technique was employed to numerically solve the resultant ordinary differential equations with the associated boundary conditions and the impact of flow, thermal, and irreversibility distribution fields are determined through graphs. The findings identified that higher levels of Hartmann number produce the Lorentz force, which limits fluid flow and lowers velocity, the response of nonlinear thermal radiation diminishes the heat transfer rate, and a rise in the Casson parameter also reduces the Bejan number. The results of this research can be used to improve heat transfer performance in biomedical devices, design-efficient energy conversion cycles, optimize cooling systems, and cover a wide range of energy technologies from renewable energy to aerospacepropulsion.

Theoretical analysis on temperature-lifting cycle for ocean thermal energy conversion

A significant obstacle to the widespread large-scale utilization of ocean thermal energy is the low temperature of the heat source, which restricts the turbine inlet to saturated steam conditions and results in notably reduced turbine efficiency. In this paper, a novel temperature-lifting based Ocean Thermal Energy Conversion cycle (OTEC) is proposed. The cycle combines the second-type absorption heat pump and the Rankine power cycle to overheat the working fluid at the turbine inlet using both surface and deep seawater, thereby mitigating the adverse effects of low surface seawater temperatures on energy conversion. The thermodynamic model is developed for this proposed cycle, 22 wet working fluids are selected for the Rankine sub-cycle. A comparative analysis with the traditional Rankine cycles is conducted to evaluate the cycle performance. The results show that the overheated temperature at the turbine inlet reaches up to 44.7 °C relying on the ocean thermal energy. In contrast to the traditional Rankine cycle, the proposed cycle achieved an average thermal efficiency improvement of 40 % and a substantial increase in exergy efficiency, ranging from 17.99–57.58 % to 32.83–68.88 %. The economic analysis reveals that the optimal cost is reduced by 38 % compared to the Rankine cycle, leading to a lower levelized cost of energy, down from 0.18 $/kWh to 0.13 $/kWh. This novel cycle offers an economically efficient and easily implementable approach to enhance low-grade thermal energy conversion.

Conceptual design of megawatt-level mobile nuclear power system based on heat pipe cooled reactor

Mobile nuclear power system has the advantages such as the well adaptability, the strong sustainability, and the convenient transportation, which can satisfy the energy demand of special environments such as island, and polar region. In this paper, the conceptual design of Mobile Nuclear Power System named MNPS-1000 is proposed, which is consist of the modular heat pipe cooled reactor and combined cycle energy conversion system to achieve the 1MWe output. The design characteristics include the operation lifetime of 3000 days in full power mode, negative temperature reactivity feedback, redundancy in reactivity control, 33% energy conversion efficiency. Due to the efficient heat transfer capability of lithium heat pipes, total of 216 heat pipes can ensure the heat transfer of 3MWt. The modular design of reactor and heat pipe heat exchanger decreases the volume of the system to achieve the compact arrangement in the standard containers with 12.0m×2.5m×2.5m size. The reactor physics and thermal hydraulics analysis, heat pipe design, and energy conversion system analysis are taken out to show the feasibility and performances of this conceptual design.

Environmental benefits for a geothermal power plant with CO2 reinjection: case study of the Kizildere 3 U1 geothermal power plant

Geothermal power plants (GPP) with high non condensable gases (NCG) content geothermal fluid have shown to be environmental impacting relating to their energy production, which could be critical if no corrective actions are achieved. The GPP of Kizildere 3 U1, located in Türkiye (Denizli), in where the geothermal fluid contains high percentage of CO2, 99% of the NCG fraction, which represents the 3% of the geothermal fluid mass, is taken as a relevant case study to implement a new innovation consisting of NCG reinjection to reduce the amount of NCGs released to the atmosphere. In order to calculate the present environmental impacts which the plant is causing (baseline); and the potential reduction of environmental impacts which can be achieved with the innovation (reinjection), a life cycle assessment (LCA) calculation were developed. Primary data were collected for all the relevant stages of the energy conversion cycle and complemented where necessary with secondary data from other geothermal power plants studies. The main results of the baseline environmental assessment show that the construction phase is the most impacting phase due to the materials used in the power plant building construction, electrical generation equipment and distributed machinery and infrastructures; the effects in the operation phase are dominated by the geothermal fluid composition. In this sense, the application of CO2 reinjection at the Turkish site into the reservoir will prevent the emission of 1,700 tons·year−1 in the pilot site and 10% of the total emissions released along the life span of the GPP.

A symmetry analysis methodology for general energy conversion systems

Symmetry is a useful concept that has guided many scientific developments in fields such as structural engineering, data, and materials science. Here we apply a symmetry analysis method to explore the relationship between symmetry, output work and efficiency in macroscopic energy conversion systems. Brayton cycle is used as an example. A specific potential-displacement-energy (PDE) diagram was established for system symmetry analysis. Results prove that the symmetry of thermodynamic cycles could predict the output work and the efficiency. Stronger rotational symmetry generates more work while reflection symmetry leads to higher efficiency at constant specific heat capacity (cp). The condition for varied cp to keep intermediate maximum-work temperature constant is greatly broaden. A more symmetrical cycle with higher efficiency and larger output work is designed based on the symmetry analysis results. The results could also be applied to other thermodynamic cycles, such as Carnot cycle, which provides insights to design more efficient energy conversion cycles.

Review of Active Circuit and Passive Circuit Techniques to Improve the Performance of Highly Efficient Energy Harvesting Systems

In piezoelectric energy harvesting systems, energy harvesting circuits are the interface between piezoelectric devices and electrical loads. The conventional view of this interface is based on the concept of impedance matching. In fact, in the power supply circuit can also apply as an electrical boundary conditions, such as voltage and charge, to piezoelectric devices for each energy conversion cycle. The major drawback of piezoelectric power harvesting have low-power relationships in systems within (in the range of μW to mW), then system also have significantly reduced any potential losses in circuits that make up the EH system, whereas other condition into careful selection of circuits and components can enhanced the energy harvesting performance and electricity consumption. In the study of energy harvesting systems, it is an energy harvesting system approach that using active and passive electronic circuit to control voltage and or charge on piezoelectric devices as proposed and review to mechanical inputs for optimized energy conversion. Several factors in the practical limitation of active and passive energy consumption, due to device limitations and the power efficiency of electronic circuits, will be introduced and have played an important role into to enhance optimum and increase efficiency of energy harvesting system.

Robust optimal dispatching model and a benefit allocation strategy for rural novel virtual power plants incorporating biomass waste energy conversion and carbon cycle utilization

To optimize the utilization of rural biomass waste resources (e.g., straw and solid waste), biomass waste energy conversion (BWEC) and carbon cycle utilization (CCU) are integrated into a traditional virtual power plant, i.e., a rural BWEC-CCU-based virtual power plant. Furthermore, a fuzzy robust two-stage dispatching optimal model for the BWEC-CCU-based virtual power plant is established considering the non-determinacy from a wind power plant (WPP) and photovoltaic (PV) power. The scheduling model includes the day-ahead deterministic dispatching model and real-time uncertainty dispatching model. Among them, in the day-ahead dispatching phase, the dispatching plan is formulated with minimum operating cost and carbon emission targets. In the real-time dispatching phase, the optimal dispatching strategy is formulated aiming at minimum deviation adjustment cost by applying the Latin hypercube sampling method. The robust stochastic theory is used to describe the uncertainty. Third, in order to achieve optimal distribution of multi-agent cooperation benefits, a benefit distribution strategy based on Nash negotiation is designed considering the three-dimensional interfering factor of the marginal benefit contribution, carbon emission contribution, and deviation risk. Finally, a rural distribution network in Jiangsu province, China, is selected for case analysis, and the results show that 1) the synergistic optimal effect of BWEC and CCU is obvious, and the operation cost and deviation adjustment cost could decrease by 26.21% and 39.78%, respectively. While the capacity ratio of WPP + PV, BWEC, and CCU is 5:3:2, the dispatching scheme is optimum. 2) This scheduling model can be used to formulate the optimal scheduling scheme. Compared with the robust coefficient Γ = 0, when Γ = 1, the WPP and PV output decreased by 15.72% and 15.12%, and the output of BWEC and CCU increased by 30.7% and 188.19%, respectively. When Γ∈ (0.3, 0.9), the growth of Γ has the most direct impact on the dispatching scheme. 3) The proposed benefit equilibrium allocation strategy can formulate the most reasonable benefit allocation plan. Compared with the traditional benefit allocation strategy, when the proposed method is used, the benefit share of the WPP and PV reduces by 5.2%, and the benefit share of a small hydropower station, BWEC, and CCU increases by 1.7%, 9.7%, and 3.8%, respectively. Overall, the proposed optimal dispatching and benefit allocation strategy could improve the aggregated utilization of rural biomass waste resources and distributed energy resources while balancing the benefit appeal of different agents.

Broadband Vibration-Based Energy Harvesting for Wireless Sensor Applications Using Frequency Upconversion.

Silicon-based kinetic energy converters employing variable capacitors, also known as electrostatic vibration energy harvesters, hold promise as power sources for Internet of Things devices. However, for most wireless applications, such as wearable technology or environmental and structural monitoring, the ambient vibration is often at relatively low frequencies (1-100 Hz). Since the power output of electrostatic harvesters is positively correlated to the frequency of capacitance oscillation, typical electrostatic energy harvesters, designed to match the natural frequency of ambient vibrations, do not produce sufficient power output. Moreover, energy conversion is limited to a narrow range of input frequencies. To address these shortcomings, an impacted-based electrostatic energy harvester is explored experimentally. The impact refers to electrode collision and it triggers frequency upconversion, namely a secondary high-frequency free oscillation of the electrodes overlapping with primary device oscillation tuned to input vibration frequency. The main purpose of high-frequency oscillation is to enable additional energy conversion cycles since this will increase the energy output. The devices investigated were fabricated using a commercial microfabrication foundry process and were experimentally studied. These devices exhibit non-uniform cross-section electrodes and a springless mass. The non-uniform width electrodes were used to prevent pull-in following electrode collision. Springless masses from different materials and sizes, such as 0.5 mm diameter Tungsten carbide, 0.8 mm diameter Tungsten carbide, zirconium dioxide, and silicon nitride, were added in an attempt to force collisions over a range of applied frequencies that would not otherwise result in collisions. The results show that the system operates over a relatively wide frequency range (up to 700 Hz frequency range), with the lower limit far below the natural frequency of the device. The addition of the springless mass successfully increased the device bandwidth. For example, at a low peak-to-peak vibration acceleration of 0.5 g (peak-to-peak), the addition of a zirconium dioxide ball doubled the device's bandwidth. Testing with different balls indicates that the different sizes and material properties have different effects on the device's performance, altering its mechanical and electrical damping.

Self-powered electrocatalytic nitrate to ammonia driven by lightweight triboelectric nanogenerators for wind energy harvesting

Ammonia (NH3) is an essential feedstock for modern industry and agriculture, as well as a promising energy carrier owing to its high energy density (4.3 kWh kg–1) and storage security. The electrocatalytic nitrate reduction reaction to ammonia (NRA) is a promising alternative route for convenient and distributed NH3 synthesis coupled with clean energy, and is attracting widespread attention. Building a coupled system for NH3 production between NRA and clean energy capture is an exciting direction for future distributed energy utilization and conversion. Herein, a lightweight triboelectric nanogenerators (TENGs) with ultra-low start-up wind speed (3.0 m s–1) is coupled to NRA system loaded with polycrystalline copper, enabling energy harvesting in a wide wind speed band for the efficient NH3 production. An adaptation strategy for capacitor embedded in the energy conversion process is proposed to further enhance the efficiency of coupled system, achieving a high NH3 yield of 11.48 μg cm−2 h–1 with the high catalytic activity of polycrystalline copper on cathode. This work opens up a coupled electrocatalysis and natural energy capture system for the conversion of NO3– to NH3, and provides an idea for the renewable energy conversion and nitrogen cycle remediation.

A performance study of R717 and R22 as the working fluid for OTEC plant

The purpose of this paper is to compare the thermal efficiency of an ocean thermal energy conversion (OTEC) cycle using R717 and R22 working fluids. An OTEC system typically operates at the temperature difference between the average warm surface seawater of 30 °C and the cold deep seawater of 8 °C. The temperature difference will then power a turbine to produce electricity. R22 and R717 are two potential working fluids to be used in the OTEC cycle to absorb heat due to their saturation temperature. However, R22 is associated with higher global warming potential and the global warming potential (GWP) of 1,760, compared to R717 with zero GWP. The study shows that the thermal efficiency of R22 is 0.211% higher than R717. Moreover, the thermal power required by the water circuit to cool/heat the OTEC circuit for R717 is 13% higher than R22. However, the required working fluid flow rate of the R717 system is 81.5% lower than R22, making the former significantly smaller in size.

Influence of the Interdomain Interface on Structural and Redox Properties of Multiheme Proteins.

Multiheme proteins are important in energy conversion and biogeochemical cycles of nitrogen and sulfur. A diheme cytochrome c4 (c4) was used as a model to elucidate roles of the interdomain interface on properties of iron centers in its hemes A and B. Isolated monoheme domains c4-A and c4-B, together with the full-length diheme c4 and its Met-to-His ligand variants, were characterized by a variety of spectroscopic and stability measurements. In both isolated domains, the heme iron is Met/His-ligated at pH 5.0, as in the full-length c4, but becomes His/His-ligated in c4-B at higher pH. Intradomain contacts in c4-A are minimally affected by the separation of c4-A and c4-B domains, and isolated c4-A is folded. In contrast, the isolated c4-B is partially unfolded, and the interface with c4-A guides folding of this domain. The c4-A and c4-B domains have the propensity to interact even without the polypeptide linker. Thermodynamic cycles have revealed properties of monomeric folded isolated domains, suggesting that ferrous (FeII), but not ferric (FeIII) c4-A and c4-B, is stabilized by the interface. This study illustrates the effects of the interface on tuning structural and redox properties of multiheme proteins and enriches our understanding of redox-dependent complexation.

Experimental development and optimization of a standing wave thermoacoustic refrigerator using additive manufactured stacks

While many previous research publications focused on developing simple and inexpensive acoustic refrigerator prototypes, the current state of play in the field reveals the need to elaborate robust and replicable facilities for experimental and test purposes. In this context, the present article justifies the importance of an economical and technologically simple process demonstrator. The construction of an experimental Thermo-Acoustic Refrigerator (TAR), employing an acoustic-to-thermal energy conversion cycle, is further described. Setup's repeatability and replicability and results' robustness were primarily addressed, while innovative techniques for stack production and optimization were also proposed. The success of experiments in terms of optimization and reproducibility was validated via the temperature gradients obtained. The adequacy of experimental results was verified by comparing them with a numerical simulation using the DeltaEC software.

Application potential of a new kind of superconducting energy storage/convertor

Our previous studies had proved that a permanent magnet and a closed superconductor coil can construct an energy storage/convertor. This kind of device is able to convert mechanical energy to electromagnetic energy or to make an energy conversion cycle of mechanical → electromagnetic → mechanical. In this study, we focus on the investigations into the application potential of this kind of device. First, we confirmed our proposed optimized configuration with theoretical analysis and experiments on a scaled-up testing platform. Furthermore, a new prototype with a large permanent magnet and a grouped coil composed of three separated closed superconducting coils was built and tested. It was proved that both practical meaningful mechanical force and energy storing capacity could be achieved with this kind of device by using enlarged pair of magnet and superconductor coil. Finally, we investigated the attenuation characteristic of the current in the superconducting coil at a stable energy storing state for a duration of about two hours, which shown the attenuation being practically tolerable for an energy storage with a typical charging-discharging cycle less than a few hours. It is concluded that this kind of device is of some advantages and promising application potentials as a short-term energy storage, particularly to replace fly-wheels in the case of mechanical → electromagnetic → mechanical conversion.

Performance improvement of ocean thermal energy conversion organic Rankine cycle under temperature glide effect

The temperature glide effect of zeotropic mixtures on ocean thermal energy conversion (OTEC) cycle driven by a narrow temperature difference, which is significantly different from that in conventional low-grade energy technologies, is yet to be thoroughly studied. In this study, the binary zeotropic mixtures-based OTEC cycle is investigated. Comparative analysis of the classical zeotropic ORC and six types of zeotropic ORCs configured with or without series/parallel multi-pressure evaporators and single-/dual-outlet liquid-separated condensers were conducted. The results showed that zeotropic mixtures could be beneficial in ocean thermal energy conversion. Multi-pressure evaporation could significantly reduce the irreversible loss in the heat exchanger, and the series multi-pressure evaporator-based zeotropic ORC (SMZO) performed better than the parallel cycle (PMZO), with 0.09%–0.14% higher thermal efficiency, 2.27%–3.11% higher turbine power output, and 0.89%–1.46% higher exergy efficiency. Liquid-separated condensation could improve the condensation effect by increasing the heat transfer coefficient, and liquid-separated dryness dominant the performance. Dual-outlet liquid-separated condensation could also increase cycle-levelised energy cost. Comparingly, the single-outlet liquid-separated condensation based cycle could reduce the levelised energy cost by 7.93% and 4.81%, respectively.

Low-enthalpy geothermal energy resources in the Central Andes of Argentina: A case study of the Pismanta system

Geothermal energy resources are necessary to meet the increasing energy requirements worldwide and reduce the impact of climate change, particularly in developing countries. The aim of this study is the investigation of the low-enthalpy geothermal system of Pismanta, in the Central Andes of Argentina, to evaluate the possibility of power generation or direct use applications. Results indicate a circulation of meteoric water to the reservoir located in the Iglesia Basin, reaching a maximum depth of 2500 m. A background heat flow of 60 mW/m2 raises the temperature of the reservoir to approximately 95 °C resulting in a mean thermal gradient of 30 °C/km. The preliminary evaluation of four binary cycle energy conversion plants suggests a gross power generation range of 30–280 kW and the capacity of using the remaining heat for direct use applications such as drying of fruits, greenhouses, food processing and membrane distillation processes to solve arsenic problems in freshwater, among others.

Effects of working conditions on the performance of an ammonia ejector used in an ocean thermal energy conversion system

AbstractOcean thermal energy has attracted much attention for its huge potential resources. It's proved that an ocean thermal energy conversion (OTEC) cycle system using ammonia ejectors is beneficial to improve the cycle efficiency. Thus, the performance of an ammonia ejector is studied numerically in this paper. Effects of working conditions which occurred inside the ammonia ejector, like primary flow pressure (1.3‐2.1 MPa), secondary flow pressure (0.45‐0.65 MPa), and back pressure (0.5‐1.05 MPa), on the mixing process and flow phenomenon, are discussed in detail. The results demonstrate that the entrainment ratio of ammonia ejector ranging from 0.35‐0.65 increases with decreasing primary flow pressure at the critical working mode, while the reverse is true for the critical back pressure. Two small vortexes are formed near the ejector wall due to the boundary layer separation when the ejector works at the subcritical or critical mode. These vortexes reduce the effective area and flow rate of the secondary flow. The Ma contours are nearly the same in the nozzle and mixing zone for the critical and subcritical mode, but distributions of Ma vary dramatically in the diffuser corresponding to the variation of secondary series of oblique shock.