Transient Performance Analysis Research Articles

Transient Pressure Performance Analysis of Hydraulically Fractured Horizontal Well in Tight Oil Reservoir

Transient Pressure Performance Analysis of Hydraulically Fractured Horizontal Well in Tight Oil Reservoir

Transient Performance Analysis of Centrifugal Left Ventricular Assist Devices Coupled With Windkessel Model: Large Eddy Simulations Study on Continuous and Pulsatile Flow Operation.

Computational fluid dynamics (CFD) simulations are widely used to develop and analyze blood-contacting medical devices such as left ventricular assist devices (LVADs). This work presents an analysis of the transient behavior of two centrifugal LVADs with different designs: HeartWare VAD and HeartMate3. A scale-resolving methodology is followed through Large Eddy Simulations, which allows for the visualization of turbulent structures. The three-dimensional (3D) LVAD models are coupled to a zero-dimensional (0D) 2-element Windkessel model, which accounts for the vascular resistance and compliance of the arterial system downstream of the device. Furthermore, both continuous- and pulsatile-flow operation modes are analyzed. For the pulsatile conditions, the artificial pulse of HeartMate3 is imposed, leading to a larger variation of performance variables in HeartWare VAD than in HeartMate3. Moreover, CFD results of pulsatile-flow simulations are compared to those obtained by accessing the quasi-steady maps of the pumps. The quasi-steady approach is a predictive tool used to provide a preliminary approximation of the pulsatile evolution of flow rate, pressure head, and power, by only imposing a speed pulse and vascular parameters. This preliminary quasi-steady solution can be useful for deciding the characteristics of the pulsatile speed law before running a transient CFD simulation, as the former entails a significant reduction in computational cost in comparison to the latter.

Analysis of Transient Thermoacoustic Characteristics and Performance in Carbon Nanotube Sponge Underwater Transducers.

Recent advancements in marine technology have highlighted the urgent need for enhanced underwater acoustic applications, from sonar detection to communication and noise cancellation, driving the pursuit of innovative transducer technologies. In this paper, a new underwater thermoacoustic (TA) transducer made from carbon nanotube (CNT) sponge is designed to achieve wide bandwidth, high energy conversion efficiency, simple structure, good transient response, and stable sound response, utilizing the TA effect through electro-thermal modulation. The transducer has potential application in underwater acoustic communication. An electro-thermal-acoustic coupled simulation for the open model, sandwich model, and encapsulated model is presented to analyze the transient behaviors of CNT sponge TA transducers in liquid environments. The effects of key design parameters on the acoustic performances of both systems are revealed. The results demonstrate that a short pulse excitation with a low duty cycle could greatly improve the heat dissipation of the encapsulated transducer, especially when the thermoacoustic response time becomes comparable to thermal relaxation time.

Transient analysis of an efficient solar assisted air-conditioning system for subtropical climate with various solar thermal collectors

The air conditioning demand of the world is largely fulfilled by vapor compression systems; however, these systems are also responsible for depleting ozone layer due to the nature of refrigerants. Desiccant cooling systems integrated with solar thermal energy technologies could be an attractive alternative with some performance enhancement techniques. In this study, transient seasonal performance investigation is performed for an innovative solar integrated desiccant cooling system that uses regenerative evaporative cooler known as solar assisted desiccant integrated Maisotsenko cycle cooler for better cooling performance. Furthermore, transient annual performance analysis of solar system for meeting thermal energy requirement for regenerating the desiccant wheel in summer season and handling heating load of the building in winter season is also carried out with three different solar thermal collector technologies for finding out more efficient technology. The key performance indicators in this study are useful energy gain, solar source efficiency, auxiliary energy sharing, coefficient of performance, and solar fraction. The results of the key performance parameters are reported as monthly average values. The proposed integrated system resulted to be very efficient with a maximum COP value of 1.13 in April when latent cooling loads are low and 0.78 in August when latent cooling loads are higher. The system’s maximum cooling capacity is 24 kW in April corresponding to a sensible heat factor of 0.720. Furthermore, the regeneration temperature requirements ranged from 50 °C to 78 °C, respectively that makes it favorable to use low grade thermal energy through non concentrating solar thermal collectors. The regeneration thermal energy requirement for desiccant wheel fluctuates throughout the year, maximizing in August due to higher dehumidification requirements. The study also revealed that the evacuated tube collector technology is most suitable with average annual efficiency of around 36 %.

Transient analysis of temperature field and fission gas about the arc plate fuel element

Obtaining the temperature field and fission gas release of fuel elements are crucial to the study on fuel behaviors and ensure the safety of elements. In order to enhance fuel efficiency, providing a design idea to make the fast reactor with high flux and multi-function, we have designed a core of the lead-based fast reactor with arc plate fuel elements. Based on above, a transient performance analysis program of arc plate fuel elements (TPAPAFE) was developed in this paper, for analyzing the thermal and fission gas module of arc plate fuel element by calculating transient variation in the maximum pellet temperature, internal and external coolant outlet temperature, and fission gas release share. The modular verification was done by comparing the results of TPAPAFE with others. Besides, the result of the arc plate fuel analyzed by TPAPAFE shows that the code is feasible and rational, and the single arc plate is so thin that coolant outlet temperatures on both sides of the plate are almost the same. Meanwhile, the error in temperature data between TPAPAFE and the steady-state program is only 5%. Furthermore, fission gas release fraction increased linearly with pellet temperature and bubble growth.

Numerical study of transient supercooling performance and thermal stress analysis of segmented annular thermoelectric cooler

A multiphysics-coupled numerical simulation of a segmental annular thermoelectric cooler (SATEC) was performed using a three-dimensional finite element method. A coupling model of the temperature, stress, and electric fields was established based on the three-dimensional transient states. Moreover, the effects of different pulse width (τ), pulse current amplitude (Pa), pulse current shape parameter (m), heat transfer coefficient (h), angle (θ), and length (H) of the thermoelectric leg on the SATEC transient properties and von Mises stress were studied. The results show that τ and Pa are the key influencing factors of SATEC. The larger the h, the more optimized the heat transfer effect of the SATEC hot end. However, when h increased to a certain value, the changes in the transient performance were insignificant. The optimal pulse can be achieved when the input pulse current Iop = 6.47 A and pulse width τ = 20 s. When the length of the thermoelectric leg H4 was 3 mm and the thermoelectric leg angle θ2 was 7°, the performance of SATEC was optimal, with Tc,min being 249.57 K, Tc,max being 279.50 K, thold being 5.5 s, and the maximum von Mises stress being 37.48 MPa. The results show that different supercooling indices and von Mises stresses could be obtained for different pulse current shapes. Geometric optimization of SATEC can improve the cooling performance and reduce the von Mises stress, thereby providing a theoretical reference for practical engineering applications and thermoelectric cooling research.

Semi-Analytical Reservoir Modeling of Non-Linear Gas Diffusion with Gas Desorption Applied to the Horn River Basin Shale Gas Play, British Columbia (Canada)

Adsorbed gas may account for a significant part of the gas resources in shale gas and coalbed methane plays. Understanding gas sorption behaviors and integrating gas desorption into analytical reservoir modeling and an associated transient performance analysis are important for evaluating a system’s gas desorption ability and further analyzing its CO2 injectability, utilization, and storage capacity. However, gas desorption, along with other pressure-dominated gas properties, increases a system’s non-linearity in theoretical studies. Few studies on analytical modeling have integrated the gas desorption feature into a non-linear system and validated the model’s accuracy. In this study, the desorbed gas due to pressure decay was treated as an additional source/sink term in the source-and-sink function methods. This method was combined with the integral image method in a semi-analytical manner to determine the amount of gas desorption. Fundamental reservoir and gas properties from the Horn River Basin shale gas play were chosen to evaluate the methodology and the performance of the associated production well. The results were compared with the commercial fine-gridding numerical simulation software, and good matches were achieved. The results showed that the desorbed gas released from rock will supply free-gas flow when the pressure significantly decreases due to gas production. The production wellbore pressure can be maintained at a higher level, and the production rate was higher than in cases where gas desorption was not considered, depending on the operating conditions.

Transient performance analysis of a solid oxide fuel cell during power regulations with different control strategies based on a 3D dynamic model

Transient performance analysis of a solid oxide fuel cell during power regulations with different control strategies based on a 3D dynamic model

Transient and altitude performance analysis of hydrogen fuelled internal combustion engines with different charging concepts

In the internal combustion engine industry, there is a significant shift towards alternative fuels to accomplish zero net carbon dioxide emissions as well as the legislation requirements. According to former studies, in addition to its advantages of being carbon-free and having appropriate combustion characteristics, low nitrogen oxide engine-out emission levels are achieved at lean burn combustion of hydrogen. Lean combustion leads to a turbocharging system requirement. Which is then utilized to generate the expected power output at high altitudes and during transient maneuvers.This study aims to determine the ideal air-charging vessel which can meet the objectives of high altitude. Which is 0 % torque derate and transient response time with respect to 0 %–90 % of maximum torque which is typically ∼3–4 s for diesel engines, while keeping the lean combustion to release ultra-low NOX emissions. Different charging concepts have been investigated by applying 1-D thermodynamic modeling on a H2ICE with a direct injection system which is for heavy-duty vehicles.

Performance analysis of a pulse detonation turbine engine based on unsteady finite-time model

Quasi-steady state and transient state performance analyses of a pulse detonation turbine engine (PDTE) are conducted based on an unsteady finite-time model. In quasi-steady state performance analysis, the transient compressor operation status over a detonation cycle time is studied. The thrust, specific fuel consumption, and the cycle thermal efficiency are compared under four different operation frequencies. The power extraction method is introduced to design a control strategy for the transient state performance analysis. Last, effect of flight conditions on the PDTE acceleration performance is investigated. The results show that the compressor will enter the surge condition during the pulse detonation combustor (PDC) exhaust period and strive back to the non-surge condition during the filling process due to the pressure changes in PDC. The increasing of the operation frequency will bring performance promotion, as the thrust and thermal efficiency will increase while the specific fuel consumption will go down. An optimal fuel supply law is obtained by utilizing the power extraction method, and it takes the PDTE 6.08s to accelerate from the corrected rotor speed of 0.6–1.0. The rising of flight altitude will dramatically prolong the acceleration process, while increasing of Ma will speed up the acceleration process.

Numerical analysis of a flat plate collector using different types of parallel tube geometry

To obtain improved thermal performance of flat plate solar collectors, the effect of square and rectangular riser tubes of a flat plate collector (FPC) were numerically investigated and compared with circular riser tube FPC in the present study. For this purpose, a three-dimensional numerical model for FPC collectors has been developed and simulated in CFD software ANSYS FLUENT. Transient thermal performance analysis is carried out to find out the optimum geometrical configuration of the FPC riser tube. The numerical results indicated that using the square-shaped riser tube in FPC improves the collector’s useful heat exchange rate as well as thermal efficiency as compared to the use of circular and rectangular riser tubes. There is a maximum 8.1% higher heat exchange rate of the collector with a square riser tube than a circular riser tube under the same operating conditions. The average efficiency of the collector with the circular tube is 65.95%, whereas the square tube has the highest efficiency of 70.44%. However, the pressure drops through the square and rectangular riser geometry are higher than the circular tube. By making a balance between enhanced heat exchange rate and increased pressure drop, the performance evaluation criterion was evaluated and the square-shaped riser tube having the highest value of 2.65 is better than the other configurations. The results clearly indicate that the collector’s performance is notably influenced by the shape of the riser tube, with a square shape yielding superior performance.

Aero-Engine Preliminary Design Optimization and Operability Studies Supported by a Compressor Mean-Line Design Module

An approach for preliminary aero-engine design, incorporating a mean-line code for the design of axial-flow, multi-stage compressors, is presented. The compressor mean-line code is developed and integrated within a framework for the preliminary design and assessment of aero-engine concepts. It is then combined with modules for compressor map generation, multi-point engine design, steady-state and transient engine off-design performance and aircraft mission analysis. Implementation examples are presented, demonstrating the determination of the optimal combination of compressor and engine design parameters for achieving minimum fuel burn over a specific aircraft mission, while obeying constraints that guarantee operability over the entire flight envelope. Constraints related to compressor stability during transient maneuvers between idle and static take-off conditions and engine temperature limits at maximum take-off are respected by the final design. The results demonstrate the potential for design trade-offs between engine performance at the aircraft mission level and compressor aerodynamic stability.

Design and transient temperature control performance analysis of a novel hybrid PCM-based heat sink

This paper reported a novel hybrid PCM-based heat sink that combines the active flow channel, passive natural convection, and PCM latent heat absorption to maintain the temperature control performance while electronic devices are subjected to the transient pulsed heat flux shock. Moreover, the effects of the channel's flow characteristics, flow channel height, and heat flux on the heat dissipation and temperature management features are analyzed numerically. In addition to the thermal characteristics, the energy consumption efficiency of the hybrid system is also discussed. The results demonstrate that the effective temperature control performance of the passive PCM-based heat sink increases with the rise of impact heat flux until it is <8 W·cm−2, and the temperature control efficiency can reach 47.6 % compared with the passive heat sink without PCM. Adopting the active flow channel performs excellently in temperature control management as ultra-high heat flux is applied; meanwhile, the pumping power should be considered. The novel hybrid PCM-based heat sink designed in this work with Hc = Hf/15 and Re = 150 excelled over the traditional pure channel heat sink with Hc = 5Hf/15 and Re = 2250. Moreover, the temperature control performance and energy-saving effect were both improved after optimization, and the energy-saving rate reached approximately 83.3 %.

Transient and steady performance analysis of a free-piston Stirling generator

Transient and steady performance analysis of a free-piston Stirling generator

Electromagnetic design and performance analysis of coreless superconducting machine

With the development of offshore wind power generation, there is an urgent demand for high-power wind turbines. Superconducting machines with high power density and efficiency are one of the solutions for wind turbines of 10 MW and above. This paper summarizes the existing superconducting synchronous generators in several structural forms and features, and considers that the coreless machine can avoid the impact of core oversaturation on the power density increase of the machine, which is the development direction of the superconducting machine. In this paper, the structural topology of a coreless superconducting machine is established and the similarities and differences between its structure and that of a conventional one are analyzed. Since the conventional magnetic circuit method is no longer applicable, a designing model based on the analytical method is established for the designing of coreless machines, which considers the effects of slotless armature, the superconducting excitation winding thickness and the nonlinearity of the ferromagnetic material. Based on this method, the magnetic field distribution is solved and verified with the finite element method. Further, the effect of the superconducting excitation winding opening angle on the magnetic field in the air gap of the machine is investigated, and the machine structure is optimized based on this. The steady-state and transient performance analysis of the machine is carried out to illustrate the operating characteristics of the coreless superconducting machine. The design method and analysis results of this paper can provide a reference for building higher power density coreless superconducting wind turbines.

Boundary condition coupling methods and its application to BOP-integrated transient simulation of SMART

The load-following operation of small modular reactors (SMRs) requires accurate prediction of transient behaviors that can occur in the balance of plants (BOP) and the nuclear steam supply system (NSSS). However, 1-D thermal-hydraulics analysis codes developed for safety and performance analysis have conventionally excluded the BOP from the simulation by assuming ideal boundary conditions for the main steam and feed water (MS/FW) systems, i.e., an open loop. In this study, we introduced a lumped model of BOP fluid system and coupled it with NSSS without any ideal boundary conditions, i.e., in a closed loop. Various methods for coupling boundary conditions at MS/FW were tested to validate their combination in terms of minimizing numerical instability, which mainly arises from the coupled boundaries. The method exhibiting the best performance was selected and applied to a transient simulation of an integrated NSSS and BOP system of a SMART. For a transient event with core power change of 100–20-100%, the simulation exhibited numerical stability throughout the system without any significant perturbation of thermal-hydraulic parameters. Thus, the introduced boundary-condition coupling method and BOP fluid system model can expectedly be employed for the transient simulation and performance analysis of SMRs requiring daily load-following operations.

Transient Modeling and Performance Analysis of Hydrogen-Fueled Aero Engines

With the combustor burning hydrogen, as well as the strongly coupled fuel and cooling system, the configuration of a hydrogen-fueled aero engine is more complex than that of a conventional aero engine. The performance, and especially the dynamic behavior of a hydrogen-fueled aero engine, need to be fully understood for engine system design and optimization. In this paper, both the transient modeling and performance analysis of hydrogen-fueled engines are presented. Firstly, the models specific to the hydrogen-fueled engine components and systems, including the hydrogen-fueled combustor, the steam injection system, a simplified model for a quick NOx emission assessment, and the heat exchangers, are developed and then integrated to a conventional engine models. The simulations with both Simulink and Speedgoat-based hardware in the loop system are carried out. Secondly, the performance analysis is performed for a typical turbofan engine configuration, CF6, and for the two hydrogen-fueled engine configurations, ENABLEH2 and HySIITE, which are currently under research and development by the European Union and Pratt &amp; Whitney, respectively. At last, the simulation results demonstrate that the developed transient models can effectively reflect the characteristics of hydrogen burning, heat exchanging, and NOx emission for hydrogen-fueled engines. In most cases, the hydrogen-fueled engines show lower specific fuel consumption, lower turbine entry temperature, and less NOx emissions compared with conventional engines. For example, at max thrust state, the advanced hydrogen-fueled engine can reduce the parameters mentioned above by about 68.5%, 3.7%, and 12.7%, respectively (a mean value of two configurations).

Transient thermal modeling and performance analysis of photovoltaic panels

AbstractPhotovoltaic technology enables the direct conversion of solar energy into electrical energy. Model studies have a very crucial place in the implementation of PV systems. Electrical efficiency decreases with increasing PV panel temperature. So, solar panel temperature is an important parameter that needs to be reduced to obtain a better energy efficiency from PV panels. In this study, the aim is to develop a simple method that can estimate the temperature of a solar panel. It can utilize different methods to obtain the thermal responses of a PV panel. In this study, a modeling study was carried out to find panel temperature, efficiency and power values under transient ambient conditions. As a simpler approach, “lumped system analysis” method was used. The model developed in this study can simulate the thermal performance of the PV panel under transient conditions. After the model is defined for a particular PV panel, the required inputs are; total incident solar radiation, wind speed and ambient temperature. The results obtained from this model were compared with existing modeling and experimental studies in the literature. With the simulation using the model developed in this study, panel efficiency, temperature and panel electricity power were calculated using instantaneous environmental data for the selected Konya and Sanliurfa (Turkey) regions. In this paper, it was obtained that the wind speed increased the PV panel efficiency, while the ambient temperature decreased it. Depending on the increase in wind speed (1–2 m/s), the increase in PV panel electric power is 3.7%, while the increase in high wind speeds (5–6 m/s) decreases to 0.77%. It was found that a 7°C increase in ambient temperature caused a 4°C increase in PV panel temperature and a 1.5% decrease in PV electrical power generation.The PV panel electrical power values calculated using the efficiency values calculated according to the daily average environmental temperatures were found to be 13% higher than the power values calculated using instantaneous environmental temperatures. If this difference is not taken into account in the calculation of economic payback periods, it will lead to significant erroneous results. The importance of transient simulations of the PV panel has been demonstrated by the calculations.

Mathematical modeling and designing an optimized fuzzy temperature controller for a vacuum box electric furnace: Numerical and experimental study

In this article, an experimentally validated new mathematical model is developed to show a vacuum box electric furnace’s thermal behavior and predict the temperature of the desired point inside it. The model is derived by extracting the equivalent electrical circuit of the system based on heat transfer principles. To show the accuracy of the model, its behavior has been evaluated by comparing it with experimental data. Then, an optimized fuzzy controller is designed using four metaheuristic algorithms, that is, genetic algorithm, harmony search, cuckoo optimization algorithm, and water cycle algorithm. The rule-base and the membership functions are optimized by these optimization algorithms with four criteria, that is, integral of absolute error, integral of square error, integral of time absolute error, and integral of time square error. The simulation results indicate that the fuzzy controllers tuned by the integral of time square error criterion get better performance, especially in genetic and water cycle algorithms. The designed controller based on the proposed model is implemented on an experimental setup. The experimental test shows a good agreement between experimental and simulation results. The obtained results show the ability of the fuzzy controller and approve that the developed model can be used for transient performance analysis of a vacuum box electric furnace and real-time controller design.

Mathematical modeling for transient thermal performance analysis of phase change material-based heat exchanger

Thermal energy storage (TES) provides a unique way for the thermal solutions to short-duration thermal load systems. TES system utilizes phase change material (PCM), wherein energy is stored in latent heat during the lean time and released during peak load. Conventionally, in a shell-and-tube PCM heat exchanger, PCM is stored in the shell and heat transfer fluid (HTF) flows in the tube. Numerical modeling based on computational fluid dynamics (CFD) tools like FLUENT and COMSOL are computationally intensive. Most numerical research is based on the enthalpy porosity model for solidification/melting problems. Enthalpy-porosity model requires a mushy zone parameter constant which significantly affects analysis results. The constant has no theoretical basis and is chosen based on experience. Analytical models in literature cannot give reasonably good results, which can be directly utilized for engineering purposes. This paper establishes a mathematical model based on the effectiveness-NTU (e-NTU) technique for transient analysis/rating of such PCM heat exchangers. Transient behavior of PCM heat exchanger due to phase transforming static PCM are modeled using an innovative concept of PCM zones, effective zonal length of heat exchange, and PCM zonal resistances. These functions are dependent on one dimension – total PCM liquid fraction ‘xf’ and a model is established for evaluating thermal performance analysis and optimization of PCM heat exchangers. The model is validated against published experimental results for cumulative energy stored in PCM of a PCM heat exchanger with air as HTF. The root-mean-square error for evaluated & predicted model results is less than 2.5%. The model proposed is uncomplicated and can be further utilized to optimize PCM heat exchangers. Transient analysis of inlet–outlet HTF temperature difference, PCM heat exchanger effectiveness, total PCM liquid fraction, PCM phase fractions, and zonal heat exchange length ratios of PCM heat exchanger for the respective experimental cases is further investigated.