Split Flow Research Articles

Design and experimental characterization of a propane-based reversible dual source/sink heat pump

The current paper presents the design and energy performance analysis of a propane-based reversible Dual Source/Sink Heat Pump (DSHP). DSHPs offer an alternative to conventional water to water and air to water heat pumps, leveraging the strengths of both technologies in an efficient manner. The developed prototype incorporates an innovative Dual Source/Sink Heat eXchanger (DSHX), enabling the unit operating in various modes, including space heating, space cooling, and domestic hot water production using brine, air or both simultaneously as a source/sink. The DSHX serves as as both a condenser or an evaporator, directly rejecting or absorbing heat from air and/or brine. By eliminating secondary loops and defrost cycles, the DSHX minimizes energy losses. The main novelty of this work lies in the DSHX that integrates external units typically duplicated in DSHPs into a single component, eliminating the need for split refrigerant flow rates, thus avoiding maldistribution, refrigerant charge increase and draining valves. A steady state experimental campaign was conducted in a climatic chamber to characterize the DSHP prototype and validate the DSHX performance models. Heating capacity up to 11.2 kW and COP values up to 4.7 were achieved at nominal compressor speed by supplying hot water at 35 °C with an ambient temperature of 7 °C. Similarly, when producing cold water at 7 °C, cooling capacity and EER reached 9.8 kW and 3.6, respectively, at nominal compressor speed using air as heat sink at 35 °C. The effects of various operating parameters on the overall coefficient of performance and heat duty in both heating and cooling modes, considering air or brine as heat source/sink are analyzed in detail. Results demonstrate enhancements of approximately 15 % in capacity and efficiency compared to earlier work. Moreover, four deterministic models were created in order to predict the behaviour of the DSHX and validated against experimental results, reaching deviation values below 15 %.

Thermal equalization design for the battery energy storage system (BESS) of a fully electric ship

The adoption of fully electric ships represents a significant step forward in addressing the environmental challenges of climate change and pollution in the shipping industry. This research details the optimized design of a battery energy storage system (BESS) and its air-cooling thermal management system for a 2000-ton bulk cargo ship. In comparison to the conventional flow splitter (FS-I), which divides airflow into 8 transverse branches, two novel designs—FS-II (dividing airflow into 2, 4, and 8 branches) and FS-III (dividing into 2, 4, 8, and 16 longitudinal and transverse branches)—were introduced. FS-II improves flow uniformity from 0.42 (FS-I) to 0.86 but results in an increased pressure drop up to 881.47 Pa. FS-III further enhances flow uniformity to 0.97 while reducing pressure drop to 191.99 Pa. The thermal performance of battery boxes with FS-I, FS-II, and FS-III was evaluated under extreme conditions and a complete voyage cycle. FS-III exhibited superior thermal regulation, maintaining Tmax consistently below 33.9°C during the entire voyage. These findings provide valuable insights for designing thermal management systems in electric ships.

Multi-Split Configuration Design for Fluid-Based Thermal Management Systems

Abstract High power density systems require efficient cooling to maintain their thermal performance. Despite this, as systems get larger and more complex, human expertise and insight may not suffice to determine the desired thermal management system designs. To this end, a framework for automatic architecture exploration is presented in this article for a class of single-phase, multi-split cooling systems. For this class of systems, heat generation devices are clustered based on their spatial information, and flow splits are added only when required and at the location of heat devices. To generate different architectures, candidate architectures are represented as graphs. From these graphs, dynamic physics models are created automatically using a graph-based thermal modeling framework. Then, an optimal fluid flow distribution problem is solved by addressing temperature constraints in the presence of exogenous heat loads to achieve optimal performance. The focus in this work is on the design of general multi-split heat management systems. The methods presented here can be used for diverse applications in the domain of configuration design. The multi-split algorithm can produce configurations where splitting can occur at any of the vertices. The results presented include three categories of problems and are discussed in detail.

Performance analysis and prediction of a modified precompression transcritical CO2 power generation cycle

The efficient utilization of biomass energy and the optimal operation of integrated renewable energy sources in virtual power plants have become critical issues to achieve carbon neutrality targets in rural areas. In the rural areas of Northeast China, a large amount of electricity can be generated from biomass. It is very important to develop biomass power generation equipment for this rural area. Due to the high thermal efficiency and its compact system without freezing process like water, CO2 thermal cycle is an appropriate option for this kind of power generation equipment. According to whether the flow is separated, CO2 cycles can be divided into the single flow layouts and split flow layouts. Compared to the single flow layouts, split flow layouts have higher efficiency, but more complex structures and lower heat transfer power per unit area. Considering the climatic characteristics of Heilongjiang Province and the seasonality of straw biomass utilization, this study proposes a modified scheme for the precompression transcritical CO2 cycle in the single flow layout to meet the simple structure requirement of the small power plants in cold areas like Northeast China. Through energy analysis, the study calculates the thermal efficiencies of the two cycles when the inlet pressure of the main compressor is 5 MPa, the turbine inlet temperature is 550 °C and the pressure ratios of the main compressor are in the range of 4.5–5.5. The optimal efficiency of the traditional precompression cycle is 43.55 % when the main compressor pressure ratio is 5.5, while the modified precompression cycle is 44.86 % when the pressure ratio is 5.0266. The modified precompression cycle has a higher efficiency than the traditional precompression cycle at a lower pressure ratio of the main compressor.

Experimental investigation of flow splitters' impact on the hydraulics of Piano Key Weirs

Piano Key Weirs (PKWs) have gained significant attention due to due to challenges associated with nappe oscillation in their flow dynamics. This experimental study explores the effectiveness of flow splitters—specifically circular, square, and rectangular designs—in enhancing the hydraulic performance of various PKW shapes: triangular, rectangular, and trapezoidal, under a range of hydraulic conditions, including both free and submerged flow. Experiments were conducted in a dedicated channel, 10 m long, 0.75 m wide, and 0.80 m high. The results indicate that under submerged flow conditions, discharge coefficients decreased by 61 % for rectangular, 59 % for triangular, and 55 % for trapezoidal PKWs compared to free flow, reflecting a reduction in efficiency. Notably, the trapezoidal PKWs maintained the highest discharge coefficient, improving efficiency by 2 % over triangular PKWs and by 12 % over rectangular PKWs. Flow splitters facilitate flow separation by linking entrapped air beneath the flow to the free surface, thereby mitigating nappe oscillation. In free flow conditions, rectangular and square splitters are more effective than circular ones for flow separation and energy dissipation, although geometric variations did not significantly influence the upstream water head in submerged flow scenarios. While flow splitters did not affect the discharge coefficient or efficiency of the various weir shapes under submerged conditions, they were found to decrease discharge by 10 % for triangular PKWs in free flow conditions. Overall, flow splitters demonstrated greater efficiency in submerged flow scenarios. In free flow, triangular PKWs were observed to dissipate approximately 4.4 % more energy than rectangular PKWs and 6 % more than trapezoidal shapes, with minimal differences in energy dissipation during submerged flow. This research also introduces a new equation for estimating the discharge coefficient in free flow, incorporating a correction factor yielding R2 = 0.967, RMSE = 0.217, and MRPE = 5.94 %, expanding upon the work of Zarei et al. [19] for submerged flows. The study enhances understanding of hydraulic behaviors and discharge coefficients of PKWs equipped with flow splitters, contributing to improved aeration performance.

Mechanistic study and structural optimization for the improvement of flow field in cyclone annular space with bypass flow

The inefficiency of cyclone separation for fine particulate matter is attributed to the presence of longitudinal circulating flow and short-circuit flow in the annular space. To enhance cyclone performance, a novel cyclone design called enhanced cyclone with split flow (ECSF) has been developed, which effectively suppresses circulating flow, short-circuit flow, and eccentric circulation through bypass flow and underflow. The mechanism of bypass flow on improving the annular space’s flow field is investigated using the Reynolds stress model and discrete phase model, along with an examination of the impact of annular space height. Simulation results demonstrate that bypass flow can directly counteract vertical circulation in the annular space by creating a gas partition near the vortex finder inlet to block short-circuiting. This suppression effect on both vertical circulation and short-circuiting increases with higher bypass flow ratios. Furthermore, while the presence of an annular space limits ECSF performance optimization, its elimination simplifies structure by removing the vortex finder while maximizing separation efficiency. When no annular space exists (height = 0 mm), ECSF achieves highest separation efficiencies for 10 μm and 2.5 μm particles at approximately 96 % and 83 %, respectively; energy consumption is also minimized at only 0.94 kPa. These findings lay a foundation for future application research on ECSF.

Modulation optimization when using a splitter pump after the first dimension in comprehensive two- dimensional liquid chromatography

The rapid growth in the use of two dimensional liquid chromatography (2D-LC) applied to the analysis of moderately to highly complex mixtures, has been fueled by continuous improvements in performance and robustness of the instrument components, as well as the ease-of-use of software necessary for controlling the 2D-LC instrument hardware, and analysis of the large data files that result from this type of work.This work has focused on the evaluation of the performance of an online full comprehensive mode (LC×LC), when an active modulation is implemented using a flow splitter pump placed after the 1D effluent. Two different types of splitting pumps were evaluated: a binary ultra-high pressure liquid chromatography (UHPLC) pump and a high precision syringe pump. We analyzed the performance (reproducibility in peak area and retention times and the 2D peak dispersion) as a function of the location of the active pump Before or After the modulation valve, and the influence of connecting tubes (based on internal diameter and length) necessary between the interface, waste, and the splitting pump. The effect on the flow direction on the filling and flushing of the injection loops at the modulation valve was also analyzed for each pump.In this study, we demonstrate that flow-splitting LCxLC assembly can be performed using either a UHPLC binary pump or a simple syringe pump. Flow splitting after the first dimension is a straightforward strategy to: (i) independently select the 1D column and flow rates with respect to the second dimension; (ii) consciously dilute the eluate according to the solvent characteristics of the second dimension, thereby avoiding 2D peak distortions; and (iii) adapt the injected amount to the second column according to the relative concentration of the components in a complex sample. However, careful consideration of the system setup is necessary. It is demonstrated how experimental results can be significantly affected in terms of peak broadening and reproducibility if optimization of the interface is not taken into account.In addition, under the optimized conditions, the reproducibility in peak area and dispersion in the 2D dimension were evaluated as a function of the amount of sample transferred in terms of percentage of filled loop.

Does Practice Match Protocol? A Comparison of Triage-to-Provider Time Among More vs. Less Acute Emergency Department Patients.

Introduction The Emergency Severity Index (ESI) stratifies emergency department (ED) patients for triage, from "most acute" (level 1) to "least acute" (level 5). Many EDs have a split flow model where less acute (ESI 4 and 5) are seen in a fast track, while more acute (ESI 1, 2, and 3) are seen in the acute care area. A core principle of emergency medicine (EM) is to attend to more acute patients first. Deliberately designating an area for less acute patients to be initially assessed quickly by a first provider might result in them being seen before more acute patients. This study aims to determine the percentage of less acute patients seen by a provider sooner after triage than more acute patients who arrived within 10 minutes of one another. Additionally, this study compares the fast track and acute care areas to see if location affects triage-to-provider time. Methods A random convenience sample of 252 ED patients aged ≥18 was taken. Patients were included if their ESI was available for the provider during sign-up. Patients were excluded if they were directly sent to the ED psychiatric area or attended to by the author. We collected data on the ESI level, time stamps for triage and first provider sign-up, and the location to which the patient was triaged (fast track vs. acute care). Paired patients' ESI levels, locations, and triage and first provider sign-up times were compared. Results The study included 126 pairs of patients. There was a statistically significant difference in triage-to-provider times for paired ESI 2 vs. 3 patients (60.5 vs. 35.5 minutes, p = 0.0007) and overall paired high- vs. low-acuity patients (55 vs. 39.5 minutes, p = 0.004). However, in 34.8% of paired ESI 2 vs. 3 patients, the ESI 3 patient was seen prior to the paired ESI 2 patient, and in 39.4% of overall paired high vs. low acuity patients, the less acute patient was seen before the more acute patient. Additionally, patients in the acute care area had significantly shorter median triage-to-provider times (~40 minutes) compared to those in the fast track area for ESI 2 (acute care) vs. ESI 3 (fast track) and overall high acuity (acute care) vs. low acuity (fast track). Nonetheless, approximately one-third of ESI 3 patients triaged to fast track were seen before ESI 2 patients triaged to the acute care area. Conclusion The split flow model reduces overall ED length of stay, improving flow volume, revenue, and patient satisfaction. However, it comes at the expense of the fundamental ethos of EM and potentially subverts the intended triage process. Although most more acute patients are seen by a provider sooner after triage than less acute patients, a substantial number are seen later, which could delay urgent medical needs and negatively impact patients' outcomes. Furthermore, patients triaged to acute care are, in general, seen sooner post-triage than identical-ESI-level fast track patients, suggesting fast track might not function as intended (for low-acuity patients to be quickly assessed and initiate diagnostic and treatment plans). We intend to follow this exploratory study with a more comprehensive, multivariate analysis that will consider confounding variables such as initial vital signs, how busy a provider was that day, etc. The future study will also examine patient outcomes to determine the impact on more acute patients of the split flow model and, in particular, on less acute patients being seen sooner by a first provider.

Performance and economic study of a novel high-efficiency PEMFC vehicle thermal management system applied for cold conditions

This paper proposes three different heating management systems, sysse (self priming thermal management system), syslow (low temperature thermal management system), and syssp (split flow thermal management system), which are mainly composed of PEMFC and heat pump subsystems. Simulations were conducted to compare the comprehensive performance of these systems under cold startup and cold operating conditions, and analyzed the effect of different factors on these three system. The results show that under the influence of cell stack parameters, compared to sysse and syslow, the syssp has an average power consumption reduction of 29.95 % and 20.94 %, with a maximum power reduction of 31.46 % and 27.61 %, the average range power increases by 35.09 % and 23.58 %, with a maximum range power increase of 107.53 % and 75.57 %, the average COPPEMFC (Coefficient of Performance of heating Proton Exchange Membrane Fuel Cell) increases by 0.56 and 0.37. Under the influence of heat pump parameters, the evaporating temperature has a larger impact on the performance gains of the syssp, while condensing temperature has a greater effect on power consumption, range power, and COP variations. Compared to sysse and syslow, the syssp can recover costs as quickly as 3.12 and 3.68 years.

Optimizing lean and rich Vapor compression with solar Assistance for post-combustion carbon capture in natural gas-fired power plant

The integration of post-combustion capture (PCC) CO2 technologies with power plants and high-emission industrial processes has become imperative for reducing carbon emissions and mitigating environmental impacts. This study focuses on addressing the significant energy consumption associated with PCC and explores the potential of using solar thermal energy to optimize configurations, thereby enhancing sustainability and reducing dependency on conventional power sources. Simulate various configurations under steady-state conditions using Aspen HYSYS V11 and Aspen Economic Evaluation software. The results indicate a substantial reduction in energy consumption to 2.1 GJ/ton CO2 after the initial optimization steps. The key innovations involve the integration of Lean Vapor Compression (LVC), Solvent Split Flow (SSF), Rich Solvent Recycle (RSR), and Rich Vapor Compression (RVC). Further optimization was conducted by integrating a reboiler with parabolic trough collectors (PTC), to reduce energy penalties. The LVC + RVC + RSR + SSF + PTC configuration results reveal a notable improvement in exergoeconomic factors, ranging from 3.13% to 7.8%, highlighting the economic feasibility of the optimized configurations. Simultaneously, the energy penalty decreased by 11.1%, signifying enhanced sustainability in the proposed PCC system. This study contributes to the gap in research by demonstrating the efficacy of solar thermal energy in optimizing PCC configurations, providing a pathway towards more sustainable and energy-efficient solutions for carbon capture in high-emission industrial sectors. The findings offer insights for researchers, engineers, and policymakers aiming to address the pressing issue of carbon emissions from industrial processes.

Exploring a reversible adaptation of conventional HPLC for capillary-scale operation

This study introduces a feasible approach for utilizing a conventional High-Performance Liquid Chromatography (HPLC) instrument at the capillary scale (1 - 10 µL/min). The development of an active flow splitter and an adapted UV-visible (UV–vis) detection cell are described. The system employs an Arduino Uno board to monitor a flow sensor and control a stepper motor that automates a split valve to achieve capillary-scale flow rates from a conventional pump. A capillary UV–vis cell compatible with conventional detectors, featuring an optical path length with a volume of 14 nL, was developed to address the detection challenges at this scale and minimize extra column band broadening. The system performance was assessed by a lab-packed LC capillary column with 0.25 mm x 15 cm dimensions packed with 3.0 µm C18 particles. Model compounds, particularly polycyclic aromatic hydrocarbons (PAHs), were employed to assess the functionality of all developed components in terms of theoretical plates, resolution, and band broadening. The proposed system is a profitable, reliable, and cost-effective tool for miniaturized liquid chromatography.

Split flow principle implementation for advanced subcritical double stage organic rankine cycle configuration for geothermal power production

The main goal of research is to find the most suitable combination of working fluids, for double stage Organic Rankine Cycle configurations which ensure maximum net power output for low to medium enthalpy geothermal sources with temperatures from 120 °C to 180 °C. All obtained results are compared with the values obtained in simple Organic Rankine Cycle configuration. In general, it can be concluded that the highest net power output is produced by the double stage Organic Rankine Cycle configuration in the geothermal temperature interval from 120 °C to 132 °C. In the geothermal fluid inlet temperature interval from 143 °C to 180 °C double stage Organic Rankine Cycle configuration achieves the highest net power output values at 150 °C, 160 °C, 170 °C and 180 °C and that 40,93 (kW) with a combination of working fluids R236fa/R1234yf (high temperature stage/low temperature stage), 49,85 (kW) with R236ea/R227ea, 59,03 (kW) with R236ea/R227ea and 69,40 (kW) with n-Butane/R1234ze(E). In the temperature interval from 132 °C to 142 °C all considered configurations achieve similar values of net power output.

Comprehensive Two-Dimensional Liquid Chromatography-High-Resolution Mass Spectrometry for Complex Protein Digest Analysis Using Parallel Gradients.

Despite the high gain in peak capacity, online comprehensive two-dimensional liquid chromatography coupled with high-resolution mass spectrometry (LC × LC-HRMS) has not yet been widely applied to the analysis of complex protein digests. One reason is the method's reduced sensitivity which can be linked to the high flow rates of the second separation dimension (2D). This results in higher dilution factors and the need for flow splitters to couple to ESI-MS. This study reports proof-of-principle results of the development of an RPLC × RPLC-HRMS method using parallel gradients (2D flow rate of 0.7 mL min-1) and its comparison to shifted gradient methods (2D of 1.4 mL min-1) for the analysis of complex digests using HRMS (QExactive-Plus MS). Shifted and parallel gradients resulted in high surface coverage (SC) and effective peak capacity (SC of 0.6226 and 0.7439 and effective peak capacity of 779 and 757 in 60 min). When applied to a cell line digest sample, parallel gradients allowed higher sensitivity (e.g., average MS intensity increased by a factor of 3), allowing for a higher number of identifications (e.g., about 2600 vs 3900 peptides). In addition, reducing the modulation time to 10 s significantly increased the number of MS/MS events that could be performed. When compared to a 1D-RPLC method, parallel RPLC × RPLC-HRMS methods offered a higher separation performance (FHWH from 0.12 to 0.018 min) with limited sensitivity losses resulting in an increase of analyte identifications (e.g., about 6000 vs 7000 peptides and 1500 vs 1990 proteins).

Quartz Crystal Microbalance as a Holistic Detector for Quantifying Complex Organic Matrices during Liquid Chromatography: 1. Coupling, Characterization, and Validation.

A matrix in highly complex samples can cause adverse effects on the trace analysis of targeted organic compounds. A suitable separation of the target analyte(s) and matrix before the instrumental analysis is often a vital step for which chromatographic cleanup methods remain one of the most frequently used strategies, particularly high-performance liquid chromatography (HPLC). The lack of a simple real-time detection technique that can quantify the entirety of the matrix during this step, especially with gradient solvents, renders optimization of the cleanup challenging. This paper, along with a companion one, explores the possibilities and limitations of quartz crystal microbalance (QCM) dry-mass sensing for quantifying complex organic matrices during gradient HPLC. To this end, this work coupled a QCM and a microfluidic spray dryer with a commercial HPLC system using a flow splitter and developed a calibration and data processing strategy. The system was characterized in terms of detection and quantification limits, with LOD = 4.3-15 mg/L and LOQ = 16-52 mg/L, respectively, for different eluent compositions. Validation of natural organic matter in an environmental sample against offline total organic carbon analysis confirmed the approach's feasibility, with an absolute recovery of 103 ± 10%. Our findings suggest that QCM dry-mass sensing could serve as a valuable tool for analysts routinely employing HPLC cleanup methods, offering potential benefits across various analytical fields.

Multi-Objective Topology Optimization of Conjugate Heat Transfer Using Level Sets and Anisotropic Mesh Adaptation

This study proposes a new computational framework for the multi-objective topology optimization of conjugate heat transfer systems using a continuous adjoint approach. It relies on a monolithic solver for the coupled steady-state Navier–Stokes and heat equations, which combines finite elements stabilized by the variational multi-scale method, level set representations of the fluid–solid interfaces and immersed modeling of heterogeneous materials (fluid–solid) to ensure that the proper amount of heat is exchanged to the ambient fluid by solid objects in arbitrary geometry. At each optimization iteration, anisotropic mesh adaptation is applied in near-wall regions automatically captured by the level set. This considerably cuts the computational effort associated with calling the finite element solver, in comparison to traditional topology optimization algorithms operating on isotropic grids with a comparable refinement level. Given that we operate within the constraint of a specified number of nodes in the mesh, this allows not only to improve the accuracy of interface representation and motion but also to retain the high fidelity of the numerical solutions at the grid points just adjacent to the interface. Finally, the remeshing and resolution steps both run within a highly parallel environment, which makes it possible for the proposed algorithm to tackle large-scale problems in three dimensions with several tens of millions of state degrees of freedom. The developed solver is validated first by minimizing dissipation in a flow splitter device, for which the method delivers relevant optimal designs over a wide range of volume constraints and flow rate distributions over the multiple outlet orifices but yields better accuracy compared to reference data from literature obtained using uniform meshes (in the sense that the layouts are more smooth, and the solutions are better resolved). The scheme is then applied to a two-dimensional heat transfer problem, using bi-objective cost functionals combining flow resistance and thermal recoverable power. A comprehensive parametric study reveals a complex arrangement of optimal solutions on the Pareto front, with multiple branches of symmetric and asymmetric designs, some of them previously unreported. Finally, the algorithmic developments are substantiated with several three-dimensional numerical examples tackled under fixed weights for heat transfer and flow resistance, for which we show that the optimal layouts computed at low Reynolds number, that are intrinsically relevant to a broad range of microfluidic application, can also serve as smooth solutions to high-Reynolds-number engineering problems of practical interest.

Numerical investigation on the effect of feed operating parameters and inlet structure on a cyclone utilizing flow splitting for performance enhancement

The shunting technique is regarded as one of the most crucial approaches for suppressing localized secondary flow within a cyclone. This study employs the Reynolds stress model and discrete phase model to investigate the impact of inlet structure and feed operating parameters on the performance of enhanced cyclone with split flow (ECSF), aiming to further enhance its efficiency. The findings demonstrate that the optimum feed velocity of ECSF is 29 m/s, which surpasses that of Lapple cyclone at 23 m/s. In addition, both a contracting inlet and multiple inlets contribute to enhancing the separation efficiency of ECSF. Specifically, ECSF with a contracting inlet exhibits a total separation efficiency of 86.8% for 2.5 μm particles, representing an improvement of 12.3% compared to ECSF with a straight inlet configuration. The enhancement in separation efficiency achieved through the implementation of the four-inlet design is even more pronounced. The segregated particles are directed into the discharge pipe via either underflow or bypass flow, and the trajectory of particle entry into the discharge pipe is closely associated with their cross-sectional positioning prior to entering the cylinder.

Mass evacuation planning for disasters management: A household evacuation route choice behavior analysis

This paper presents a multi-methodological approach to analyzing household evacuation route choice behaviors and the related decision-making for mass evacuation planning in disaster management. Specifically, the proposed multi-methodological approach integrates a syncretic risk perception conceptual model with a household-based group utility evolution model. The dynamics of household evacuation route choice are explored in two stages, namely the individual utility initiation and accommodation. The unique feature of the proposed approach is that it links individual risk perception, survival psychology, and group behavioral dynamics together to characterize household decision-making about choosing the evacuation routes. An empirical study coupled with experiments is conducted to help validate the proposed household evacuation route choice behavior model. Through various designed disaster scenarios, the applicability and strengths of the proposed model for mass evacuation planning and management are demonstrated. Particularly, the mean relative prediction errors of the proposed model with respect to household-based evacuation route switching probability and path flow splits are 3.79% and 6.88%, respectively, all within an acceptable range of ±10 %. This demonstrates that the proposed model and analytical results align closely with household choice behavior.

A novel data-driven reduced order modelling methodology for simulation of humid blowout in wet combustion applications

Computationally inexpensive reduced order models such as Chemical Reactor Networks (CRN) are encouraging tools to obtain fast numerical solutions. However, the accuracy of such models is usually compromised compared to experiments or high-fidelity numerical simulations. Therefore, continued improvement of such models is necessary to ensure reasonable accuracy and fill the need for computationally inexpensive tools. To that end, inputs from computational fluid dynamics simulations have been used to build CRNs in the last 25 years. This can be further improved by the application of data-driven techniques. The present work uses a novel data-driven analysis based on high-fidelity simulation results where the high-dimensional data is first reduced to a low-dimensional manifold and is then clustered into chemically coherent regions. These results along with the high-fidelity simulation results are used to construct a CRN for wet combustion simulations. Wet combustion is a novel clean combustion technique, where an increase in the level of steam dilution distributes the flame, with a risk for flame extinction. This phenomenon, i.e., humid blowout (HBO), was modelled using the above-mentioned CRN. The HBO predicted by the CRN was also tested for thermal power, equivalence ratio, and fuel conditions different from its design point. The error in HBO prediction was quantified by comparing the steam-dilution level at HBO obtained using CRN and that obtained experimentally. The CRN predicted the HBO with an error magnitude less than 5% when the thermal power was unchanged. The maximum error in all tested conditions was 16.65%. Furthermore, a sensitivity analysis revealed that the inclusion of hot gas recirculation through the central recirculation zone, quantified by the mass flow split between the post-flame region and the CRZ, is important in the prediction of HBO, although its accuracy is inconsequential.

Pilot-scale CO2 capture demonstration of heat integration through split flow configuration using 30 wt[formula omitted] MEA at a Waste-to-Energy facility

Post-combustion carbon capture is a well-established technology to limit CO2 from industrial emissions. However, challenges such as high energy requirements for solvent regeneration persist. Research is still being conducted to improve the energy efficiency of the process. This study aims to present the results of process intensification in a pilot-scale CO2 capture plant. The pilot-scale investigations were carried out at Amager Bakke, a Waste-to-Energy facility in Copenhagen, Denmark. The tests were conducted by implementing the split flow configuration as a method of process intensification. The CO2 rich stream was split before flowing through the rich/lean heat exchanger. One of the split streams was fed to the stripper top, and the other was sent through the heat exchanger and then fed to the stripper. The cold split stream at the stripper top is heated by the overhead vapours which would otherwise escape the stripper. The current work discusses the split flow configuration results of the pilot plant by employing 30wt% MEA as the solvent and compares it to the base-case performance of the pilot. Experiments were conducted by splitting 22% of the rich solvent and feeding it to the stripper top. The performance of the split flow configuration was analysed at different reboiler duties. A minimum specific reboiler duty of 3.45 GJ/tonne CO2 is obtained for the split flow configuration, which is less than the base case by 7.8%. Additionally, a reduction in the condenser duty by at least 68% was achieved by the implementation of the split flow configuration.

Numerical simulation investigating the impact of regulated underflow rate on the performance of a cyclone with split flow

A novel cyclone design called enhanced cyclone with split flow (ECSF) incorporates bypass flow and underflow to eliminate or suppress localized secondary flow observed in conventional cyclones. The present study aims to investigate the mechanism of ECSF in suppressing localized secondary flow and explore methods for regulating the bottom flow rate. The turbulent characteristics within the ECSF are obtained using Reynolds stress model, while the trajectory of particles is predicted using discrete phase model to derive the separation performance. The accuracy of the simulation model has been validated through experimental verification. The results demonstrated that the full separation efficiency of ECSF for PM10 and PM2.5 remained above 90 % and 70 %, respectively. Moreover, it exhibited an increasing trend with the rise in the full split ratio, eventually stabilizing at approximately 95 % and 77 %, correspondingly, when the full split ratio reached 20 %. The bypass flow and underflow effectively eliminated or suppressed the upper ash ring and processing vortex core (PVC) phenomenon, respectively. However, the exacerbation of the short-circuit flow phenomenon hindered further improvement in separation efficiency beyond a full diversion ratio of 20 %. When the full split ratio is relatively small, particles may accumulate in the discharge pipe, which can be resolved by introducing auxiliary airflow; however, it is crucial to ensure that the flow rate of auxiliary flow does not exceed 14.29 % of that of feed flow to avoid compromising the separation efficiency. Furthermore, the split flow induces an additional reversed vortex within the ECSF, which extends from the overflow pipe to conical section. Its structural characteristics are influenced by both back pressure of discharge outlet and diameter of underflow pipe. To ensure optimal performance of the ECSF, it is recommended that the underflow pipe diameter should not be smaller than that of the outlet in conical section.