Pump Applications Research Articles

Comparative experimental evaluation on condensation heat transfer characteristics of R466A and R410A in smooth and micro-fin tubes

As refrigerant regulations become increasingly stringent, R466A has garnered attention as a potential replacement for R410A. Despite its potential benefits, a lack of study on the condensation heat transfer coefficient (HTC) and frictional pressure drop (FPD) of R466A hinders its application in heat pumps. In this study, the condensation HTCs and FPDs of R466A and R410A in smooth and micro-fin tubes were measured at mass fluxes of 200–600 kg m−2 s−1, vapor qualities of 0.1–0.9, and saturation temperatures of 35 °C and 45 °C. R410A exhibited 8.8–14.1% higher average condensation HTC and 24.2–35.4% higher average FPD than R466A owing to its lower vapor density. Furthermore, the heat transfer enhancement factor and pressure drop penalty factor of R466A in the micro-fin tube were 1.34 and 1.37, respectively, at G = 300 kg m−2 s−1. New condensation HTC and FPD correlations for R466A and R410A in the micro-fin tube were formulated using the measured data. The newly developed correlations exhibited average deviations of −3.9% and 7.2% and average absolute deviations of 6.3% and 16.3%, respectively.

Optimization of conventional-zeolite-synthesis from waste pumice for water adsorption

This research reports conventionally-synthesized-zeolites with comparatively large surface area (SSA) and water-uptake prepared solely from waste-pumice. Notably, the synthesis process avoided using additional commercial raw materials, organic templates, and high temperatures, so that the process was less costly and ecofriendly. To optimize the process, the synthesis time was varied, and the mixture of the raw material and alkaline solution was stirred for 12 h. The zeolite mother liquor was also recycled. Water adsorption experiments were carried out using gravimetric measurements. The Na-P1-rich zeolite product with an optimal water uptake of 0.256 g/g was synthesized after 48 h of hydrothermal activation (H). On the other hand, the product’s optimal SSA of 186 m2/g was achieved after 36H under similar conditions (rich in faujasite). Adsorption isotherms showed that water uptake increased with activation time and with the inclusion of mother liquor recycling. Furthermore, recycling resulted in a product with enhanced SSA compared to its precursor. Un-recycled products exhibited relatively high-water uptake both at low and high relative-pressure, while the recycled product had a high uptake at high relative pressure. All products could be used in adsorption heat pump (AHP) applications (air conditioning) suited for high relative humidity (RH) environments. However, high-synthesis-time non-recycled products could also work for low RH AHP applications.

Controllable switching based on vortex–antivortex pairs in exciton–polariton condensates

Abstract Vortex–antivortex pairs hold significant prospect for applications in high-capacity optical communications, multiparticle manipulations, and data processing systems. In this work, based on vortex–antivortex pairs, we explore a straightforward method to produce a 1–4 optical switch in a polariton condensate with a C-shaped potential. The switch, seeded by a degenerate state containing two vortex–antivortex pairs, can selectively target four objective states: two orthogonal states with a single vortex–antivortex pair and two concentric vortices with opposite circulations. All these topological states are stable states with the application of a single incoherent pump, while the switch is activated by an additional coherent control pulse.

Optimal Solar‐Biomass‐Diesel‐Generator Hybrid Energy for Water Pumping System Considering Demand Response

ABSTRACTThe water pumping system is a vital daily operation for a sustainable society. The demand for this essential commodity is progressively growing around the world. Incorporating renewable energy sources (RES) into its operation mitigates adverse environmental effects stemming from greenhouse gas (GHG) emissions and reduces associated costs linked to fossil fuel energy sources. Hence, the optimal sizing of a hybrid mix of RES and non‐RES energy sources to power water pumping is essential. This study employs a generalized reduced gradient (GRG) optimization method to ascertain the most effective energy mix for water pumping system (WPS) application by integrating time of use demand response. This is achieved through four scenarios: Scenario 1 (S1) utilizes grid power and Diesel generator (DG) energy sources, Scenario 2 (S2) incorporates grid power, DG, and solar PV, Scenario 3 (S3) integrates grid power, DG, solar PV, and biomass energy sources, while Scenario 4 (S4) incorporates Time of Use (TOU) with the three aforementioned energy sources. The key findings reveal an ideal solution comprising of a mix of renewable PV and biomass along with non‐renewable grid energy source embedded with Time of Use demand response (S4) with optimal energy capacities of 4007 kW of PV, 4228 kW of grid, 234 kW of biomass, and 1085 of DG owing to the least cost energy and cost of water pumped of 0.75$/kW and 1.74$/kL, respectively, most volume of water pumped of 270.50 kL. These findings prove that the integration TOU demand response program with a hybrid mix of grid‐biomass‐DG‐solar PV is best suited for water pumping applications as it gives a cost‐competitive value.

High-power narrow-linewidth tunable blue laser diode array utilizing a blazed grating external cavity

High-power, narrow-linewidth blue laser sources have been in high demand for applications in laser pumping and spectral beam combining. In this paper, a blue laser source, consisting of 12 transistor-outline (TO) packaged laser diodes (LD), is established through space beam combining. An improved external cavity (EC) utilizing a blazed grating (BG), a beam splitter, and a beam expander is investigated. Through injection feedback and mode competition, a laser output, with 31.2 W power, 445.04 nm central wavelength, 0.18 nm full-width at half maximum (FWHM) linewidth, is achieved at a driving current of 3.0 A. A tunable range of 3.6 nm is observed at 2.0 A driving current. Additionally, the effect of the deformation of the aluminum-coated grating under a high-intensity blue laser is examined. The external cavity requires a moderately efficient blazed grating and prevents potential damage caused by high absorption and thermal stress concentration. The system exhibits excellent temporal stability in both output power and spectrum. Moreover, wavelength-locking experiments using both a volume Bragg grating (VBG) and a surface grating (SG) are conducted to serve as comparative tests for this study. Compared with volume Bragg gratings, blazed gratings offer spectral tunability and are insensitive to temperature perturbations and mechanical stress. Compared with surface gratings, blazed gratings offer a relatively high threshold and stable performance at high driving currents. Furthermore, blazed gratings are more cost-effective than VBGs, providing a competitive advantage. To the best of our knowledge, it’s the first blue laser source with over 30 W output and 0.18 nm FWHM linewidth utilizing a blazed grating external cavity.

Morphologic transformation of ferrofluid during micropump driving under field control.

The superiority of ferrofluid pumps in the fields of biomedical, life science, energy, and power research has been experimentally demonstrated. However, the mechanisms underlying the morphological transformations of ferrofluid fusion and separation during pump driving are not completely understood. To bridge the gap between the theory and practical applications of ferrofluid pumps, we employed optical methods to record the dynamic morphological transformation of rotating and fixed ferrofluids under different magnetic field polarities, magnetic field distributions, and ferrofluid mass fractions. The magnetic field polarity causes dynamic differences in the fusion-separation process of the ferrofluid but does not affect the volume segmentation of the ferrofluid, which depends on the ratio of the magnetic field intensities. When this ratio deviates from one, the morphology of ferrofluid changes, reducing the pumping efficiency. Compared to external environmental factors, the mass fraction does not change the morphology of the ferrofluid. However, high mass fractions lead to wall-clinging of the ferrofluid, and low mass fractions induce bubbles, both of which detrimentally affect the pumping performance. This study reveals the properties of ferrofluid and the effects of external environmental conditions on the morphological transformation of ferrofluid, providing references for optimizing ferrofluid pumps.

Micromotor based on single fiber optical vortex tweezer

Optical micromotors are powerful tools for trapping and rotating microparticles in various fields of bio-photonics. Conventionally, optical micromotors are built using bulk optics, such as microscope objectives and SLMs. However, optical fibers provide an attractive alternative, offering a flexible photon platform for optical micromotor applications. In this paper, we present an optical micromotor designed for 3D manipulation and rotation based on a single fiber optical vortex tweezer. A tightly focused vortex beam is excited by preparing a spiral zone plate with an ultrahigh numerical aperture of up to 0.9 at the end facet of a functionalized fiber. The focused vortex beam can optically manipulate and rotate a red blood cell in 3D space far from the fiber end facet. The trapping stiffness in parallel and perpendicular orientations to the fiber axis are measured by stably trapping a standard 3-µm silica bead. The rotational performance is analyzed by rotating a trimer composed of silica beads on a glass slide, demonstrating that the rotational frequency increases with rising optical power and the rotational direction is opposite to the topological charge of the spiral zone plate. The proposed fiber micromotor with its flexible manipulation of microparticle rotation circumvents the need for the precise relative position control of multiple fiber combinations and the use of specialized fibers. The innovations hold promising potential for applications in microfluidic pumping, biopsy, micromanipulation, and other fields.

Heat Pump-Assisted Extractive Pressure-Swing Distillation with Integrated Feed Preconcentration/Solvent Recovery for Isopropanol-Benzene-Water Separation

Recently, heat-integrated pressure-swing distillation (HIPSD) has been explored for recovering isopropanol and benzene from wastewater, but the process remains highly energy-intensive. Given the dilute nature of the feed, intensified extractive distillation with an integrated preconcentration column (IED) is more suitable. However, previous researches have often overlooked the critical role of pressure and lacked rigorous optimization of operating pressure in such systems. In this article, we developed novel extractive pressure-swing distillation with integrated feed preconcentration/solvent recovery column (IEPSD) by introducing a pressure-swing configuration and incorporate energy-saving technologies to achieve more sustainable and cost-effective separation processes. First, thermodynamic analysis is conducted to explore the effect of pressure on extractive pressure-swing distillation. Then, a parallel genetic algorithm is applied for rigorous optimization, followed by the application of heat integration and heat pump. The IEPSD is superior to IED in terms of total annual cost (TAC) and CO2 emission. With the inclusion of energy-saving technologies, IEDHI and IEPSDHI further reduced TAC by 5.29% and 7.40%, and cut CO2 emissions by 25.18% and 24.03%, respectively, compared to their base processes. The use of a heat pump is particularly advantageous for IEPSD due to its lower boiling temperatures under vacuum pressure, leading to the development of IEPSDHIHP, which offered an additional 22.36% CO2 reduction and marginally lower TAC than IEPSDHI. Ultimately, IEPSDHIHP proves to be the best option, offering a 51.15% TAC reduction and 68.42% CO2 emissions reduction compared to HIPSD. In summary, the developed IED and IEPSD processes, especially with heat integration and heat pump technologies, offer significant economic and environmental advantages over conventional HIPSD.

Application of osmotic pump coupled solid phase extraction samplers for the on-site sampling and enrichment of pharmaceuticals and personal care products in wastewater treatment plants

In assessing the occurrence and fate of pharmaceuticals and personal care products (PPCPs) in wastewater treatment plants (WWTPs), their time-weighted average concentrations are highly desirable. Therefore, the development of composite sampling techniques that are suitable for on-site wastewater deployment, cost-effective, and independent of external power sources is imperative. In this study, an osmotic pump coupled solid phase extraction (OP-SPE) sampler was employed to collect samples for monitoring 14 PPCPs in WWTPs. Results showed that the PPCP recoveries by using OP-SPE samplers ranged from 40.36 % (enrofloxacin) to 115.93 % (fenoprofen), while the method quantification limits ranged from 0.15 ng/L (trimethoprim) to 3.18 ng/L (enrofloxacin). Good reproducibility was observed with relative standard deviation values of all analytes less than 20 %. The OP-SPE method achieved comparable performance in terms of recovery, repeatability, reproducibility, method detection limits, and method quantification limits, when compared to the widely adopted mixed grab samples and offline SPE pretreatment method. Eleven and fourteen PPCPs were detected in the influent and effluent, respectively. Based on the time-weighted average concentrations, the total daily mass loads of the dissolved PPCPs were 135.69 g/d in the influent and 16.03 g/d in the effluent. The OP-SPE sampler integrates in-situ sampling, filtration, enrichment, and purification, thereby minimizing the degradation of PPCPs due to microbial activity. Overall, the OP-SPE sampler has the potential to serve as a robust tool for capturing the time-weighted average concentrations of PPCPs in WWTPs, enabling estimation of mass loads and their reduction through the wastewater treatment processes.

Computational multiphase mixture simulations of a two-phase R-744 ejector geometry in transcritical R-744 heat pump applications

Purpose Two-phase R-744 ejectors are critical components enabling energy recovery in R-744 heat pump and refrigeration systems, but despite their simple geometry, the flow physics involve complex multiphase mixing phenomena that need to be well-quantified for component and overall system improvement. This study aims to report on multiphase mixture simulations for a specific two-phase R-744 ejector with supercritical inlet conditions at the motive inlet side. Design/methodology/approach Four different operating conditions, which have motive inlet pressure range of 90.1 bar–101.1 bar, are selected from an existing experimental data set. A two-phase thermodynamic equilibrium (TPTE) model is used, where the fluid properties are described by a thermodynamic look-up table. Findings The results show that the TPTE model overpredicts mass flow rates at the motive inlet, resulting in a relative error ranging from 15.6% to 21.7%. For the mass flow rate at the suction inlet, the relative errors are found less than 1.5% for three cases, while the last case has an error of 12.4%. The maximum deviation of the mass entrainment ratio is found to be 8.0% between the TPTE model and the experimental data. Ejector efficiency ranges from 25.4% to 28.0%. A higher pressure difference between the ejector outlet and the diverging nozzle exit provides greater pressure lift. Research limitations/implications Based on the results, near future efforts will be to optimize estimation errors while enabling more detailed field analysis of pressure, density, temperature and enthalpy in the computational domain. Originality/value The authors have two main original contributions: 1) the presented thermodynamic look-up table is unique and provides unique computation for the real-scale ejector domain. It was created by the authors and has not been applied before as far as we know. 2) To the best of the authors’ knowledge, this study is the first study that applies the STAR-CCM+ multiphase mixture model for R-744 mixture phenomena in heat pumps and refrigeration systems.

Application of heat pump assisted solar evacuated tube water heater operated within passive solar house in severe cold region

Replace coal with solar energy to low-cost heating in severe cold regions can improve indoor air quality, but indoor thermal comfort is not fully guaranteed. Therefore, a dual-source heat pump (DSHP) assisted solar evacuated tube water heater heating system was used in a house with sunspace to meet the heating stable and cleaning. TRNSYS model verified by experiment was used to research performance and economy of system. Results found the higher ambient temperature and solar radiation, the more heat from sunspace, solar assisted heat pump (SAHP) and solar water heater, conversely, the longer heating time of air-source heat pump (ASHP). During heating season, solar fraction of heating was 51.6 %, solar heat collection efficiency was 46.0 %, EER was 3.35, COP were 2.81 (ASHP) and 3.65 (SAHP). Heating time proportion of ASHP, SAHP and solar water heating were 15.0 %, 40.3 %, 44.7 %, ASHP heating was accounting for 22 % and 50 % in November and January. The system, sunspace supplied 16707.1, 2307.6 kW h of heat for room, solar effective heat collection was 10107.0 kW h, power consumption was 5164.7 kW h, CO2 emission reduction was 14232.4 kg. The dynamic payback period of system was 6.78 years, as will be shortened with support of clean energy heating policy.

Effect of clearance volume on the internal flow characteristics and output performance of oil-gas multiphase reciprocating pump

In the production of oil and natural gas, excessive clearance volume is an important factor affecting the normal operation of oil-gas multiphase pump. Currently, little research has been conducted on the effect of clearance volume on the output characteristics of multiphase pump at home and abroad, leading to extremely low efficiency in the field application of multiphase pump. Therefore, this study conducted numerical calculations on the internal flow characteristics and output performance of multiphase pump under different clearance volumes using FLUENT software. Results show that pressure and fluid velocity gradually decrease as the clearance volume increases. Simultaneously, the number and intensity of vortex flow gradually increase, media pressurization speed becomes slower, and the lag angle of the discharge valve opening becomes larger. Moreover, under conditions with a higher gas volume fraction, multiphase pump with larger clearance volumes experiences gas locking. Furthermore, this study provides a theoretical basis for the reasonable design of clearance volume for multiphase pump by drawing a relationship curve between gas volume fraction and clearance volume. These research findings can provide theoretical support for the performance optimization and design improvement of multiphase pumps.

Digital twin dynamic-polymorphic uncertainty surrogate model generation using a sparse polynomial chaos expansion with application in aviation hydraulic pump

Full lifecycle high fidelity digital twin is a complex model set contains multiple functions with high dimensions and multiple variables. Quantifying uncertainty for such complex models often encounters time-consuming challenges, as the number of calculated terms increases exponentially with the dimensionality of the input. This paper based on the multi-stage model and high time consumption problem of digital twins, proposed a sparse polynomial chaos expansions method to generate the digital twin dynamic-polymorphic uncertainty surrogate model, striving to strike a balance between the accuracy and time consumption of models used for digital twin uncertainty quantification. Firstly, an analysis and clarification were conducted on the dynamic-polymorphic uncertainty of the full lifetime running digital twins. Secondly, a sparse polynomial chaos expansions model response was developed based on partial least squares technology with the effectively quantified and selected basis polynomials which sorted by significant influence. In the end, the accuracy of the proxy model is evaluated by leave-one-out cross-validation. The effectiveness of this method was verified through examples, and the results showed that it achieved a balance between maintaining model accuracy and complexity.

Experimental investigation and numerical modeling of an innovative horizontal coaxial ground heat exchanger (HCGHE) for geothermal heat pump applications

Geothermal is an ideal renewable energy source for building heating and cooling via a ground source heat pump (GSHP) system. However, the high initial cost of installing the ground heat exchanger limits its adoption, especially among owners of residential and smaller non-residential buildings. This study aims to develop a new methodology for installing an innovative horizontal coaxial ground heat exchanger (HCGHE) and to investigate its thermal performance in GSHP applications through field testing and numerical simulation. Horizontal directional drilling and a new manifold design were used to install the new HCGHE, significantly reducing costs by minimizing time, materials, labor, and landscape disruption. The transient numerical model, developed in Ansys Fluent using the finite volume method, was validated against experimental data and employed to predict temperature distributions in the supply pipe, return pipe, and surrounding soil. The study determined the heat transfer rate per unit borehole length and entire thermal resistance of the HCGHE to vary from 23.0 to 35.7 W/m and 0.28 to 0.74 K·m/W in winter, and from 24.3 to 37.4 W/m and 0.12 to 0.52 K·m/W in summer. The short-term soil temperature distributions in both the radial and longitudinal directions of the HCGHE are modeled using second-order polynomial equations, with R2 values ranging from 0.994 to near unity, while the long-term soil temperature distributions follow a power law. This research not only confirmed that the innovative HCGHE design and installation can achieve good thermal performance but also provided valuable insights into continual design improvement. The innovative HCGHE-based GSHP system provides an efficient and sustainable solution for heating and cooling buildings by harnessing the earth’s natural heat, offering the advantages of simplified installation and reduced initial investment.

Heating Performance and Energy Efficiency Analysis of Air-Source Heat Pumps in Public Buildings Across Different Climate Zonings

Article Heating Performance and Energy Efficiency Analysis of Air-Source Heat Pumps in Public Buildings Across Different Climate Zonings Junbao Fan 1, Yilin Liu 1,*, Jing Ma 2, Ying Cao 1,2, Zhibin Zhang 1, Xin Cui 1 and Liwen Jin 1,* 1 School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, No. 28 Xianning West Road, Xi’an 710049, China 2 China Architecture Design and Research Group, Beijing 100044, China * Correspondence: ylliu@xjtu.edu.cn (Y.L.); lwjin@xjtu.edu.cn (L.J.) Received: 11 July 2024; Revised: 3 September 2024; Accepted: 5 September 2024; Published: 20 September 2024 Abstract: Public buildings exhibit the highest operational energy consumption and contribute the most to carbon emissions compared to other types of building. The electrification of energy terminals in public buildings is crucial for the energy conservation and emission reduction, especially the energy-saving retrofitting of heating systems. Given the significant impact of climate on the performance of air-source heat pumps, this study explored the performance and energy efficiency of air-source heat pump systems in public buildings across different climate zonings. Using Design Builder software, the physical models of three types of public buildings (commercial, hotel, and office) were constructed, and the annual variations in the building load was analyzed. Considering the effects of defrosting and low-temperature conditions, an air-source heat pump heating system models were developed using TRNSYS software. The simulation results showed that the average COP of the heat pump system on the coldest day in Harbin, Beijing, and Shanghai were 1.7, 2.46 and 2.49, respectively. Moreover, the analysis factor correlation analysis reveals that the COP of the heat pump system is positively correlated with the dry-bulb temperature, negatively correlated with the building load. Surprisingly, the COP is not affected by the types of public buildings. The findings of this study are expected to provide valuable guidance for the application and regulation of air-source heat pumps in the public buildings.

Enhancing commercial check valves in downhole pump applications through laboratory testing system development

In this study, we aim to enhance the performance and longevity of downhole pumps employed in crude oil extraction in the oil industry. Downhole pumps play a pivotal role in the rod-pump system, comprising traveling and standing valves that function similarly to ball check valves. However, these valves often experience premature wear and tear. To address this concern, we embarked on experiments involving various check valve alternatives to conventional ball valves within downhole pumps. The testing conditions were controlled precisely. Furthermore, we evaluated four distinct check valve types, the original (representing the incumbent ball valves), spring-poppet (C), spring-ball (CB), and spring-poppet with soft-seated (S6C) check valves, within a controlled laboratory environment. We employed a TEXAPON N70 solution to replicate the properties and temperature conditions of crude oil. A portable ultrasonic flow meter was used to quantify the pump flow rate and assess its volumetric efficiency. In addition, we recorded data on the polished-rod load and plunger displacement to generate dynamometer cards, thereby enabling a comprehensive evaluation of the operational performance of the pump. Furthermore, we conducted a vacuum test to scrutinize valve leakage, which is a crucial indicator of the operational lifespan of a downhole pump. Our findings show that incorporating the CB check valve with the RHB pump in oil wells operated by the PTT Exploration and Production Public Company Limited (PTTEP) could result in a 15 % increase in volumetric efficiency and a remarkable 160 % improvement in durability compared to the original ball check valve.

A Methodology to Optimize PMSM Driven Solar Water Pumps Using a Hybrid MPPT Approach in Partially Shaded Conditions

Solar water pumps are crucial for farmers, significantly reducing energy costs and providing independence from conventional fuels. Their adoption is further incentivized by government subsidies, making them a practical choice that aligns with sustainable agricultural practices. However, the cost of the required solar panels for the chosen power makes it essential to optimize solar water pumping systems (SWPS) for economic viability. This study enhances the efficiency and reliability of permanent magnet synchronous motor (PMSM)-driven SWPS in rural areas using hybrid maximum power point tracking (MPPT) algorithms and voltage-to-frequency (V/f) control strategy. It investigates the sensorless scalar control method for PMSM-based water pumps and evaluates various MPPT algorithms, including grey wolf optimization (GWO), particle swarm optimization (PSO), perturb and observe (PO), and incremental conductance (INC), along with hybrid combinations. The study, conducted using MATLAB Simulink, assesses these algorithms on convergence time, MPPT accuracy, torque ripple, and system efficiency under different partial shading conditions. Findings reveal that INC-GWO excels, providing higher accuracy, faster convergence, and reduced steady-state oscillations, thus boosting system efficiency. The V/f control strategy simplifies control mechanisms and enhances performance. Considering system non-idealities and maximum duty cycle limitations, PMSM-based SWPS achieve superior efficiency and stability, making them viable for off-grid water pumping applications.

Application of a semi-empirical modelling approach to a Two-Stage Rotary CO2 compressor

2-stage Rotary CO2 compressors are currently in use in refrigeration and heat pump applications, including occasionally including vapour injection. The need of correctly assessing the compressor’s efficiency by means of a computationally fast model arises for cycle performance prediction and optimization. In response, an innovation on an existing semi-empirical modelling approach has been introduced in this paper to describe 2-stage Rotary compressors. The model has been validated with experimental data of a CO2 compressor available in open literature, giving maximum errors of around ±3% for mass flow and ±1.82% for power prediction. Calibration of a simplified 1-stage model is also performed to analyse to which extent it is necessary to complexify the model, and to identify key or neglectable modelling elements. It is found that doing this increases the error of the compressor performance prediction. Model analysis has been done to identify the inefficiencies introduced by each physical effect considered.

Investigation on ejector design for CO2 heat pump applications us-ing Dymola

In this paper, the Dymola modelling tool is used to study the influence of ejector design onto the whole heat pump cycle working with carbon dioxide. The cycle is built using the components provided by the TIL Modelica library. It is found that the ejector models in TIL are quite limited, namely by their inability to properly capture the on-design plateau and rapid decrease in performance in off-design operation. Therefore, an in-house state-of-the-art ejector model, originally developed in Python, is implemented as a Dymola object. This model is then calibrated onto CO2 experimental data. The operation of a simple CO2 heat pump system is investigated, with focus on the ejector sizing at fixed geometry. It is found that there exists an ejector size that maximises the COP of the cycle. Furthermore, critical ejector pressure is not reached at this optimum COP point; the ejector is operating well under the on-design regime.

Age- and sex-related differences in risk factors for perioperative intra-aortic balloon pump application in patients undergoing coronary artery bypass grafting.

An intra-aortic balloon pump (IABP) is a mechanical circulatory device frequently used in patients undergoing coronary artery bypass grafting (CABG). As a treatment for perioperative haemodynamic instability, IABP insertion often implicates an adverse outcome. This study aimed to investigate the age- and sex-related disparity in risk factors for perioperative IABP insertion in CABG patients. A total of 2,460 CABG patients were included and divided into subgroups by age (elderly subgroup, ≥65 years; young subgroup, <65 years) and sex. Basic characteristics were compared between IABP and non-IABP patients in the overall patient group and the subgroups. Multivariate logistic analysis was used to investigate the significant risk factors for perioperative IABP application, and interaction effects among the potential risk factors were analysed. Combined receiver operating characteristic analysis was used to evaluate the prediction value of combined risk factors. The overall patient group had a mean age of 61.5 years. The application rate of perioperative IABP was 8.0%. A left ventricular ejection fraction (LVEF) <50% significantly correlated with perioperative IABP application in the overall patient group and the subgroups. Traditional factors such as myocardial infarction history, atrial fibrillation history, and intraoperative estimated blood loss were significant risk factors in certain subgroups. Small dense low-density lipoprotein levels were significantly associated with IABP insertion in the male subgroup and young subgroup. The area under the curve of combined risk factors was significantly higher than that of LVEF <50% alone in the overall patient group and subgroups. Age- and sex-related differences were present in the risk factor distribution for perioperative IABP insertion in CABG patients.