Valve Surgery Research Articles

Risks factors of adverse clinical outcomes in asymptomatic mitral regurgitation patients with preserved ejection fraction: a systematic review and meta-analysis.

Indication for mitral valve (MV) surgery in asymptomatic mitral regurgitation (MR) patients with preserved ejection fraction (EF) remains unclear. This study aims to identify risk factors of adverse clinical outcomes in asymptomatic MR patients with preserved EF for early indication of MV surgery. 3 databases were systematically searched to include studies with asymptomatic MR patients with preserved EF. Risk factors of adverse clinical outcomes (composite outcome of MACE and MV surgery indication), mortality, and left ventricular dysfunction (LVD) are pooled with a meta-analysis of random effect model. A total of 39 observational studies with 9135 asymptomatic moderate to severe MR patients are included. We identified 21 statistically significant risk factors for adverse outcomes. Increased natriuretic peptide, presence of atrial fibrillation, LV GLS > 20%, LVEDD > 35mm, LVESD > 22mm, and LAVI > 55ml/mm2, ERO > 55mm2, and regurgitation volume > 60ml (HR 2.21, 2.07, 4.23, 2.98, 4.05, 1.84, 4.02, 3.30, respectively; p-value < 0.05; I2 0-87%) are associated with greater risk of adverse clinical outcome. Risk factors associated with postoperative LVD are the increase of LVEDD, LVESD, and RVSP. Risk factors associated with mortality are increasing STS score and LV GLS. Several clinical parameters and risk factors can be used to stratify asymptomatic MR patients with preserved ejection fraction who could benefit from early indication for MV surgery.

Temporal changes in characteristics, incidence, and mortality in patients undergoing surgical intervention for mitral stenosis

To examine temporal changes in patient characteristics, the incidence rate of surgical intervention, and the three-year mortality rate for patients undergoing surgical intervention for mitral valve stenosis (MS) from 2001 to 2021 in Denmark. Utilizing Danish nationwide registries, we identified all adult patients undergoing first-time surgical intervention for MS (2001–2021). Temporal changes in the incidence rate of surgical intervention across calendar periods were investigated (2001–2005, 2006–2010, 2011–2015, and 2016–2021). Using Kaplan-Meier estimates, we computed temporal changes in three-year all-cause mortality across calendar periods. With multivariable Cox regression analysis, we assessed the adjusted rates of mortality. We included 256 patients (median age 60.3 years, 31.3% males). A stepwise decrease in the burden of chronic heart failure was identified (2001–2005: 54%, and 2016–2021: 20%, p-value < 0.001 for trend), while the burden of atrial fibrillation seemed stable (2001–2005: 51%, and 2016–2021: 46%, p-value = 0.27 for trend). The proportion of patients with rheumatic MS was 64% in 2001–2005 and 33% in 2016–2021, p-value < 0.001 for trend. 28 patients (10.9%) had mitral valve surgery prior to the first-time surgical intervention for MS. A stepwise decrease in the incidence rate of surgical intervention was observed: 3.3 cases per million person-years in 2001–2005 and 2.2 in 2016–2021. The incidence of patients diagnosed with first-time MS remained stable over calendar periods (2001–2005: 54.5 incidences per million person-years, and 2016–2021: 41.9, p-value = 0.46 for trend). The in-hospital mortality was 8.6% and the three-year mortality after surgical discharge was 9.0%, and we found no difference over calendar periods in either crude estimates or adjusted analysis. From nationwide data across three decades, we identified that the incidence of surgical interventiondecreased significantly within the past 20 years, while all-cause mortality remained stable. The burden of heart failure decreased, while the burden of atrial fibrillation remained stable over the study period.

Implementation of Evidence-Based International Recommendations Reduces Postoperative Delirium Rate in Patients Undergoing Cardiac Surgery or Interventions: A System-Based Quality Improvement Study.

Delirium is a frequent and serious complication of cardiac procedures that can lead to serious long-term health restrictions. As primary prevention is more effective in reducing rate of delirium than the therapy itself, this study aimed to investigate the effect of a multidisciplinary delirium prevention bundle on the postoperative delirium rate in patients undergoing cardiac procedures. In this system-based quality improvement study, a four-component delirium prevention bundle was implemented in patients undergoing cardiac procedures at a single high-volume center. The program included preoperative delirium risk stratification, multidisciplinary education of consensus guidelines, written memory aids, and post-anesthetic visits with delirium screening until postoperative day three. Overall, 234 patients were included and analyzed during the 6-month study period. The overall delirium incidence rate was 12.4%. After the first 3-month baseline implementation period, the delirium rate was 17.2%, compared with 7.6% (p = 0.026) after implementation of the delirium prevention bundle. Multivariate analysis revealed independent risk factors such as age [adjusted odds ratio (OR): 1.046; 95% confidence interval (CI): 1.002-1.092; p = 0.042], double valve surgery [adjusted OR: 13.1; 95% CI: 3.240-52.974; p < 0.0001], and peripheral artery disease [adjusted OR: 8.131; 95% CI: 2.336-28.306; p < 0.001]. Hospital stay was significantly longer in patients with delirium [median 13 (12-19.5) versus 12 (11-14) days, p = 0.009]. This multidisciplinary system-based quality improvement study demonstrated a beneficial effect on the delirium rate after the implementation of a four-component delirium prevention bundle in patients undergoing cardiac surgery or intervention. Furthermore, multivariate analysis revealed important independent risk factors for delirium development. This might improve early risk stratification and strategies for this high-risk patient collective.

Elevated Trans-mitral Pressure Gradient Predicts Surgery in Young People with Moderate-Severe Rheumatic Mitral Regurgitation.

Mitral regurgitation (MR) is the most common lesion in children with rheumatic heart disease (RHD). Progression of RHD results in the need for surgical intervention, the timing of which is dictated by left ventricular dilatation and the onset of heart failure symptoms. We sought to determine whether elevation in trans-mitral pressure gradient (TMPG) in those with moderate or severe rheumatic MR without significant mitral stenosis (MS) could predict the need for future surgical intervention. Echocardiographic studies were reviewed for 116 children and young people with moderate or severe rheumatic MR. Those with significant mitral stenosis or concurrent aortic valve disease were excluded. Trans-mitral pressure gradient was measured at baseline and details of mitral valve surgical intervention were retrieved from a registry database. Time to future surgery (up to six years) was compared between those with TMPG < 5mmHg and TMPG ≥ 5mmHg. Survival curves demonstrated an increased risk of surgery for those with TMPG ≥ 5mmHg with Cox proportional regression analysis providing a hazard ratio of 5.8. The proportion free from mitral valve surgery at one year for the TMPG < 5mmHg group was 0.94 (95% CI 0.86-0.97), compared to 0.62 (95% CI 0.42-0.77) in the ≥ 5mmHg group. Trans-mitral pressure gradient is a strong predictor of future mitral valve surgery in children and young people with significant rheumatic MR without MS. This non-invasive measure could be used to signal the need for more aggressive monitoring in order to optimize the timing of intervention.

Best treatment option for secondary mitral regurgitation surgery: a network meta-analysis of randomized and non-randomized controlled studies

The objective of this study is to ascertain whether subvalvular papillary muscle repair in conjunction with restrictive mitral valve annuloplasty represents the most efficacious treatment for patients presenting with secondary ischemic mitral regurgitation, as compared to restrictive mitral valve annuloplasty alone and to mitral valve replacement. A network meta-analysis was conducted to investigate outcomes of randomized controlled trials, propensity-matched studies, and observational studies, comparing various treatments for secondary ischemic mitral regurgitation. The average follow-up duration for late mortality was 4.4 years. Coronary artery bypass grafting (CABG) without mitral valve surgery had a late mortality incidence of 3.7%. Restrictive mitral annuloplasty demonstrated a rate of 6.5%, while restrictive mitral annuloplasty + CABG resulted in a rate of 4.1%. Subvalvular papillary muscle repair plus restrictive mitral annuloplasty ± CABG and mitral valve replacement + CABG had rates of 4.4% and 5.1%. SUCRA analysis showed that CABG was the most effective treatment for reducing late mortality (70.0%). This was followed by subvalvular papillary muscle repair plus restrictive mitral annuloplasty with or without CABG (62.4%). The top strategy for decreasing early death, reoperation, and readmission to the hospital for heart failure is subvalvular papillary muscle repair plus restrictive mitral annuloplasty with or without CABG, based on SUCRA probabilities (84.6%, 85.54%, and 86.3%, respectively). Subvalvular papillary muscle repair plus restrictive mitral annuloplasty ± CABG has potential to reduce the risks associated with early mortality, reoperation, and re-hospitalization for heart failure. However, further research is required to substantiate these findings.

Imminent risk of LVEF decline in asymptomatic patients with primary mitral regurgitation.

2020 American College of Cardiology/American Heart Association (ACC/AHA) Guidelines state that the ideal time for mitral valve surgery in primary mitral regurgitation (PMR) is when the LV approaches but has not yet reached echocardiographic LV ejection fraction (EF) < 60% or LV end-systolic dimension (ESD) > 40 mm. However, it is difficult to know the imminent risk of crossing this threshold when the surgical outcome is less optimal. Using machine learning and statistical models, we have shown that cardiac magnetic resonance (CMR) LV sphericity index (SI) and LV mid circumferential strain rate (SRcirc) added to LVEF and LVESD predict LVEF < 50% after mitral valve surgery. Here we test the hypothesis that these CMR features predict LVEF < 60% in asymptomatic PMR patients at 18 months. 33 asymptomatic PMR patients with moderate to severe mitral regurgitation had CMR with tissue tagging at baseline and every 6 months for 18 months. Two types of models were employed to predict LVEF < 60% at 18 months: a model using CMR features at a single time point (e.g., baseline) and a model utilizing repeated measurements over time. CMR LVEF decreased below 60% in 13 patients over 18 months. LVEF varied over time with an inverse relation to mean arterial pressure and mean end-systolic wall stress. Random Forest models utilizing LV SI, LV mid SRcirc, LVESD, and LVEF at a single time point (baseline) had a predictive accuracy of 64%. LV SI, LV mid SRcirc, LVESD and LVEF at baseline, 6, and 12 months achieved a higher predictive accuracy of 79%, improved sensitivity from 57% to 85% than baseline alone and identified a threshold of CMR LVEF 63%-64% signaling LVEF < 60%. The variability of LVEF due to blood pressure dependence may require a longitudinal study that incorporates LVEF, LVESD, SRcirc at multiple time points to identify the threshold at which LVEF is at risk for decline to less than 60%.

Inequalities in access to and outcomes of cardiac surgery in England: retrospective analysis of Hospital Episode Statistics (2010–2019)

BackgroundWe aimed to characterise the variation in access to and outcomes of cardiac surgery for people in England.MethodsWe included people >18 years of age with hospital admission for ischaemic heart...

Impact of Psoas Muscle Area Index on Short- and Mid-Term Mortality in Patients Undergoing Valve Surgery for Infective Endocarditis: A Retrospective Analysis.

Background: Sarcopenia, characterized by the loss of skeletal muscle mass, is an emerging comorbidity associated with poor outcomes in cardiovascular surgery. Its impact on mortality in patients undergoing valve surgery for infective endocarditis (IE) remains underexplored. This study investigates the relationship between sarcopenia, measured by the Psoas muscle area index (PMAi), and mortality in patients with IE undergoing valve surgery. Materials and Methods: We retrospectively analyzed 68 patients with IE who underwent valve surgery at a tertiary care center from 2013 to 2021. Sarcopenia was defined as being in the lowest quartile of PMAi, measured via preoperative computed tomography (CT). Baseline characteristics, survival outcomes, and factors influencing mortality were analyzed using Kaplan-Meier survival curves and Cox proportional hazards regression. The predictive value of PMAi for 1-year and 3-year mortality was assessed via receiver operating characteristic (ROC) curves. Results: Sarcopenia was strongly associated with increased mortality at both 1-year (HR: 0.378, p = 0.010) and 3-year follow-ups (HR: 0.457, p = 0.012). Female sex (OR: 275.748, p < 0.001) and older age (OR: 9.995, p = 0.003) were significant predictors of sarcopenia. Chronic kidney insufficiency (CKI) and the use of heart failure medication therapy also significantly impacted survival outcomes. Conclusions: Sarcopenia is a strong independent predictor of short- and mid-term mortality in patients undergoing valve surgery for IE. Routine radiological assessment of sarcopenia using PMAi could improve risk stratification and guide preoperative interventions. Tailored management strategies, especially in older women and patients with CKI, may enhance outcomes in this high-risk population.

Novel optimal high pressure determination method for CO2 air source heat pump water heater: Experimental study and methodology development

As an efficient and environment-friendly solution to replace traditional fuel-fired boiler, CO2 air source heat pump water heater (HPWH) is widely used in the commercial and residential water heating. In order to achieve the optimal performance of CO2 air source HPWH systems, the effects of electronic expansion valve (EEV) opening and inlet water flow rate on system performance are experimentally studied and the optimal matching of the two parameters are obtained in this study. Then, the relationship between the optimal high pressure and the optimal matching of EEV opening and water flow rate is discussed. Finally, a new parameter, the endpoint temperature difference (ΔTep), is defined and a novel control strategy of ΔTep = 0 is proposed to determine the optimal high pressure. The results indicate that the optimal matching of EEV opening and water flow rate corresponds to the optimal high pressure and the best COPheat of system. A smaller ΔTep corresponding to a better matching degree and a larger system COPheat. The maximum deviation between the high pressure determined by the proposed new control strategy and the optimal high pressure is less than 1.8 %, and the system COPheat under the proposed new control strategy can achieve more than 97.6 % of the maximum COPheat. Therefore, the proposed control strategy in the paper is better than that of the commonly used off-line optimal high pressure correlation and can provide guidance for the efficient operation of the CO2 air source HPWH system.

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.

Frequency-Controlled Fluidic Oscillators for Soft Robots.

Electronic-free controls have recently emerged as one of the main topics in soft robotics. However, electronic-free fluidic circuits still lack controllability and reconfigurability to achieve different functions. Here, reconfigurable pneumatic valves that widen the design space of fluidic circuits are presented. The significance of two parameters on the valve's operation: a pre-defined manufacturing parameter that sets the initial operational range of the valve, and a second, on-the-fly modifiable geometric parameter that shifts the behavior of the valve during operation is shown. It is demonstrated that equipping the valve with these reconfigurable features enables the tuning of fluidic oscillatory circuits as illustrated by two examples: a frequency-controlled relaxation oscillator and a reconfigurable ring oscillator. The relaxation oscillator is employed to control the actuation frequency of a soft hopper, which is able to achieve 80 to 125 hops min-1 and a hopping speed ranging from ≈1 to ≈1.185 BL s-1. Additionally, the reconfigurable ring oscillator is used to demonstrate how each output frequency can be controlled independently, via a soft robotic crawler that can navigate in three directions, and a volume-controlled fluidic pump able to achieve mixing of solutions in environments where electronic components cannotoperate.

Right thoracotomy with central cannulation for valve surgery: 10 years of experience.

The aim of this study is to report the early outcomes of valvular heart surgeries performed via the right thoracotomy approach. While thoracotomy with femoro-femoral bypass is an established method for minimally invasive open-heart surgeries, thoracotomy with conventional cannulation is still being explored. In our center, we conducted 958 valvular heart surgery cases using the right anterolateral thoracotomy approach with central cannulation and data were analyzed. This is a retrospective observational study based on prospectively collected data from patients who underwent valvular heart surgery at our center spanning from April 2013 to April 2023. The data encompass demographics, procedures, operative techniques, post-operative morbidity, mortality, and a 1-month follow-up. Our study revealed no procedure-related mortality. No patient required conversion to median sternotomy. Smooth cannulation and satisfactory exposure were achieved in all patients. The study encompassed a wide age range, from 14 to 68 years, with 618 female patients (64.5%) and 340 male patients (35.5%). The average cross-clamp time ranged from 38 to 90min, the duration of cardio-pulmonary bypass ranged from 45 to 105min, post-operative extubation ranged from 3 to 8h, the average drain volume ranged from 100 to 350ml, and the incision size ranged from 5 to 7cm. Our data demonstrate that conventional cannulation via the right antero-lateral thoracotomy approach for valvular heart disease is a viable alternative to reduce the side effects associated with sternotomy and femoral cannulation. This procedure is safe, reproducible, and provides the same level of treatment quality.

Sustainable optimization of balancing valve settings in urban heating systems with an enhanced Jaya algorithm

With the continuous growth of global energy demand, energy conservation in heating has become a research hotspot for urban sustainable development. However, the research on energy conservation by adjusting the balance valve in the secondary network of heating system is relatively few. To address this gap, this paper solves the balancing valve opening adjustment (BVOA) problem with the goal of minimizing heat consumption and the energy usage of circulation pumps. A mixed-integer linear programming model is designed for this problem, and an effective EJaya algorithm is proposed. Initially, a random initialization method with three scrambling strategies is employed to generate high-quality solutions. Moreover, a segmented operator is proposed to enhance the algorithm’s search efficiency. Subsequently, Q-learning is utilized to select from three neighborhood operators, enhancing the algorithm’s local search capabilities. Additionally, an adaptive search balance strategy is designed to balance the methods of updating solutions, aiding in finding better solutions. Finally, extensive experiments have validated the effectiveness and efficiency of the proposed algorithm in solving the BVOA problem, contributing to the promotion of urban energy sustainability and social welfare.

'Color Doppler stripes’ make it difficult to diagnose the severity of valvular heart diseases: a report of two cases

BackgroundEchocardiography remains the reference-standard imaging technique for assessing valvular heart disease (VHD), but artifacts like the ‘color Doppler stripe’ can complicate diagnosis. This artifact is not widely recognized and can mimic severe VHD, leading to potential misdiagnoses. We present two cases where color Doppler stripes mimicked severe VHD, highlighting the need for awareness and accurate interpretation in echocardiographic assessments.Case presentationsCase 1: An 85-year-old patient was referred for mitral valve surgery due to suspected severe mitral regurgitation (MR). Upon evaluation, transthoracic echocardiography (TTE) showed mitral valve prolapse (P3) and a high-echoic, vibrating structure attached to the mitral valve, indicative of chordal rupture. Color Doppler echocardiography revealed strong systolic signals in the left atrium, mimicking severe MR. Transesophageal echocardiography (TEE) also detected the vibrating structure and color Doppler stripes in the left atrium, left ventricle, and outside the cardiac chambers. The PISA method on TEE indicated moderate MR and left ventriculography showed Sellers grade II MR. The artifact was identified as color Doppler stripes caused by the vibrating high-echoic structure from the ruptured chorda. Case 2: A 64-year-old patient with severe aortic stenosis, end-stage kidney disease requiring hemodialysis, and a history of coronary bypass grafting presented for routine follow-up. B-mode echocardiography showed a severely calcified tricuspid aortic valve with a vibrating calcified nodule and restricted opening, corresponding to severe aortic stenosis. During systole, color Doppler signals were observed around the aortic, pulmonary, and tricuspid valves, mimicking significant pulmonary stenosis and tricuspid regurgitation. However, pulmonary stenosis was ruled out as the pulmonary valve opening was normal. Mild tricuspid regurgitation was confirmed in the apical view.ConclusionsThese cases highlight the diagnostic challenges posed by color Doppler stripes. Recognizing and understanding this artifact are crucial for the accurate diagnosis and management of VHD, ensuring appropriate treatment and patient outcomes.

Study on gas–liquid–solid multiphase flow and erosion in ball valves

In industrial processes involving ball valves, gas–liquid–solid multiphase flows with continuous carrier and discrete particle phases are characterised by erosion challenges. These challenges reduce sealing performance and can lead to leakage and valve failure. To explore the characteristics of gas–liquid–solid multiphase flow and flow-induced erosion in ball valves, we conducted a combination of computational fluid dynamics numerical simulations and experimental testing. Results indicate that an increase in the gas content increases the flow coefficient, accelerates both liquid flow and particle movement and exacerbates erosion. In addition, particles are less concentrated in regions with higher gas concentrations. Erosion is primarily observed on the upstream surface and rear wall of the valve core as well as the upper side of the downstream pipeline. Severe erosion occurs more at smaller valve openings, and affected regions expand as the valve opening increases.

A novel valve strategy for particulate matter reduction in a gasoline direct injection engine operated at cold conditions

In this study, we proposed a novel intake strategy to reduce Particulate matter (PM) emissions from gasoline direct-injection (GDI) engines during cold-start conditions emissions. This strategy is characterized by generating strong intake turbulence and low in-cylinder pressure during fuel injection through delayed intake valve opening, which theoretically promotes fuel atomization and fuel-air mixture, thereby suppressing PM formation during combustion. Experiments were conducted on a single-cylinder GDI research engine, operating at 1500 rpm, 3, 6, and 8 bar IMEP, and stoichiometric air-fuel ratio conditions with low coolant and lubricant temperatures to experimentally demonstrate the effectiveness of the proposed valve strategy in reducing PM emissions. Benchmark tests were performed using an intake camshaft with intake valve opening (IVO) at −13 °aTDC and intake valve closing (IVC) at 227 °aTDC. The novel strategy uses an intake camshaft with very late IVO at 66 °aTDC and IVC at 226 °aTDC. Two injection pressures (Pinj = 100/200 bar) were used to evaluate the pressure requirement for achieving low PM emissions with both strategies. Start of injection was swept and optimized to match the valve strategy. The results showed that the novel valve strategy leads to a 50%–90% reduction in particle number and mass emissions in cold-start conditions, and a lower injection pressure requirement to achieve comparable particle number and mass emissions compared with the normal one. For the novel valve strategy, the fuel impingement with early injection timings is largely mitigated, and thus an early injection timing shortly before the IVO is recommended.

Clinical impacts of concomitant left atrial appendage occlusion during mitral valve surgery in patients with mitral regurgitation

Surgical occlusion of the left atrial appendage (LAA) during cardiac surgery in patients with atrial fibrillation (AF) is known to reduce thromboembolism. However, data on the clinical significance of LAA occlusion (LAAO) in patients with mitral regurgitation (MR) are lacking. A total of 237 AF patients with chronic severe MR who underwent mitral valve (MV) surgery were retrospectively analyzed. Patients were divided into two groups according to concomitant LAAO or LAA preservation. The primary outcome was a composite of all-cause death and thromboembolic events (ischemic stroke or systemic embolism). The LAA was surgically occluded in 98 (41%) patients and preserved in 139 (59%) patients. During the follow-up period (median, 37 months), 29 primary outcomes occurred. In the Kaplan–Meyer analysis, the LAA preservation group showed a greater cumulative incidence of the primary outcome (P = 0.002) and thromboembolic events (P = 0.003) than the LAAO group. In the univariate Cox regression analysis, coronary artery disease, CHA2DS2-VASc score, a cauliflower-shaped LAA, Maze, and no LAAO were significantly associated with the primary outcome. In the multivariate Cox regression analysis, concomitant LAAO was significantly linked to the primary outcome (hazard ratio [HR]: 0.30, 95% confidence interval [CI]: 0.10–0.91, P = 0.033) and thromboembolic events (HR: 0.19, 95% CI: 0.04–0.87, P = 0.032). These benefits from LAAO were consistent, even after propensity score–matched analysis. For patients undergoing surgery for chronic MR who also have AF, concomitant surgical LAAO is associated with favorable clinical outcome.

Research on photovoltaic water pumping system based on valve opening model

Photovoltaic water pumping system (PVWPS) is an important way to use solar energy. In order to further improve the solar energy utilization rate of PVWPS, this study proposes a valve opening model, which solves the problem of more solar energy waste caused by fixed pipeline characteristics under different irradiation intensities. Firstly, the theoretical calculation formula of pipeline flow is deduced according to the balance relationship between photovoltaic energy supply and energy demand of water lifting pipeline in PVWPS, and its working principle is expounded. Finally, the function model of pipeline flow-valve opening-radiation intensity is derived from the cycle test of PVWPS, and the PVWPS with water lifting height of 10 m, 12 m and 14 m is verified by all-day test. Compared with the unregulated valve, the cumulative water extraction of the PVWPS with three water lifting heights after valve regulation is increased by 15.85 %, 18.06 % and 80.71 % respectively, indicating that the cumulative water extraction of the PVWPS can be effectively improved by adjusting the valve opening. This study provides a new idea for improving the utilization rate of solar energy in PVWPS.

Experimental study of the performance of a water-to-water heat pump equipped with a liquid receiver with different charge levels

This paper presents an experimental investigation of the effects of a decreasing refrigerant charge on the performance and operating conditions of an R513A water-to-water heat pump equipped with a large liquid receiver, an electronic expansion valve, and a vapor accumulator at the compressor inlet. The mass of the refrigerant inside the machine is progressively extracted to simulate refrigerant leakages occurring during the normal operation or in case of failures. The results show that the subcooling is the parameter mostly affected by a refrigerant charge variation since it rapidly collapses to 0 K with the charge reduction. Furthermore, it is possible to identify three different zones in which almost all the properties analyzed (COP, heating capacity, operating pressures and expansion valve opening) exhibit peculiar trends with the charge decrease: subcooling sensitivity zone, constant parameters zone, and compressor failure risk zone. The extension of these zones is determined by the size of the liquid receiver which is installed in the system and, for the heat pump under consideration, is between 100% and 95% of the initial charge for the first zone, between 95% and 40% for the second zone, and below 40% for the third zone.

Fault Diagnosis of Maritime Equipment Using an Intelligent Fuzzy Framework

The task of automatically and intelligently diagnosing faults in marine equipment is of great significance due to the numerous duties that shipboard professionals must handle. Incorporating automated and intelligent systems on ships allows for more efficient equipment monitoring and better decision-making. This approach has attracted considerable interest in both academia and industry because of its potential for economic savings and improved safety. Several fault diagnosis methods are documented in the literature, often involving mathematical and control theory models. However, due to the inherent complexity of some processes, not all characteristics are precisely known, making mathematical modeling highly challenging. As a result, fault diagnosis often depends on data or heuristic information. Fuzzy logic theory is particularly well suited for processing this type of information. Therefore, this paper employs fuzzy models to diagnose faults in a marine pneumatic servo-actuated valve. The fuzzy models used in fault diagnosis are obtained from the data. These fuzzy models are identified for the normal operation of the marine pneumatic servo-actuated valve, and for each fault, predicting the system’s outputs from the inputs and outputs of the process. The proposed fault diagnosis framework analyzes the discrepancy signals between the outputs of the fuzzy models and the actual process outputs. These discrepancies, known as residuals, help in detecting and isolating equipment faults. The fault isolation process uses an intelligent decision-making approach to determine the specific fault in the system. This method is applied to diagnose abrupt faults in a marine pneumatic servo-actuated valve. The approach presented was used to detect and diagnose three very important faults in the operation of a marine pneumatic servo-actuated valve. The three faults were correctly detected and isolated, and no errors were detected in this detection and isolation process.