Maximum Flow Rate Research Articles

Piezoelectric micropump cooler for high-power electronic cooling

Micro-liquid cooling is highly effective for the thermal management of electronic chips. However, it is challenging to apply to high heat flux and compact electronic devices because of the limited cooling power and large pump volume. To address this issue, a compact piezoelectric micropump cooler (PMC) integrating a parallel piezoelectric micropump (PPMP) and a heat sink with a fluid guidance structure is designed. The flow and heat transfer performance of the PMC is theoretically optimized through a numerical coupling model considering mechanics, flow-solid heat transfer, and piezoelectric effect. Simulation results suggest that a copper electrode-PZT ratio of 1.4 increases the output flow rate of the PMC, and the design of five fluid guidance structures enhances its heat dissipation effectiveness. Based on the optimized results, the PMC prototype is manufactured employing 3D printing technology. Experimental results show that the flow rate maximum is 62 mL/min with a precision of 0.07 mL/V·min. When the flow rate of PMC increases to 50 mL/min, the temperature of a heat source with 50 W/cm2 can be reduced to 57 °C, which is comparable with the simulation value. The developed model accurately characterizes the heat transfer properties of the PMC thermal management approach, providing a valuable reference for future research. The proposed PMC is characterized by its compact size, high level of integration, and exceptional cooling performance, making it suitable for electronic cooling applications with high heat flux.

The 'Prostate Embolisation AS first-line therapY compAred to meDication in treatment naïVe men with prostAte eNlargement, a randomised ControllEd trial' (P-EASY ADVANCE): a randomised controlled trial of prostate embolisation vs medication for BPH.

To compare prostate artery embolisation (PAE) to the combination of tamsulosin and dutasteride therapy as a potential first-line therapy for obstructive benign prostatic hyperplasia (BPH) in treatment-naïve patients in the 'Prostate Embolisation AS first-line therapY compAred to meDication in treatment naïVe men with prostAte eNlargement, a randomised ControllEd trial' (P-EASY ADVANCE). A total of 39 men with enlarged prostates, moderate-severe lower urinary tract symptoms (LUTS) and obstructed/equivocal urodynamic studies (UDS), and who had no prior treatment for BPH, were randomised to receive either combined medical therapy with tamsulosin and dutasteride (medication) or PAE. Follow-up UDS, International Prostate Symptom Score (IPSS), uroflowmetry and ultrasound were performed at short- to medium-term intervals following interventions and compared to baseline. The medication and PAE treatment groups had similar baseline characteristics, including prostate volumes (87.8 and 85.4 mL respectively), maximum urinary flow rate (Qmax; 6.5 and 6.6 mL/s, respectively), IPSS (19.5 and 21, respectively) and obstructed UDS (79% and 74%, respectively). Both interventions improved voiding and bladder outflow obstruction from baseline, with more patients unobstructed after PAE (63%) compared to medication (28%) (P = 0.03). PAE patients had significantly greater reductions in prostate size (P < 0.001), incomplete emptying (P = 0.002), total IPSS (P = 0.032), Qmax (P = 0.006) and quality of life (P = 0.001). Altered ejaculation, erectile dysfunction and nausea were more common in the medication group. Prostate artery embolisation was more effective than combined medical therapy at reducing urinary obstruction, decreasing prostate volume and improving LUTS in patients with BPH who had not previously been treated. This is the first randomised control study to compare PAE and combined medical therapy in exclusively treatment-naïve patients and raises the potential of PAE as an alternative early treatment option for BPH. Further randomised comparative trials are planned to further validate the role of PAE in mitigating obstructive BPH.

Process optimization and scale-up of toluene nitration in a microchannel reactor using HNO3-AC2O as nitrating agent

Aromatic nitro compounds are an important class of basic chemical raw materials, while traditional nitration methods may cause safety accidents and environmental pollution due to strong exothermicity and presence of sulfuric acid. In this work, aiming to alleviate these issues, the nitration of toluene was conducted in a microchannel reactor with nitric acid and acetic anhydride. The effect of temperature, molar ratio of nitric acid to toluene, mass fraction of acetic anhydride, and residence time on the conversion and selectivity of reaction were systematically investigated, and response surface methodology was used to optimize the process. A mononitrotoluene yield of 99.21 % can be achieved under optimum condition. Meanwhile, in order to better understand the exothermic behavior, toluene nitration by HNO3-AC2O was investigated in the semi-batch calorimeter. Finally, the optimized process was scaled up and effect of volumetric flow rate was investigated. At the selected maximum volumetric flow rate, the overtemperature of the system was 10.9 °C with a 98.3 % yield of mononitrotoluene. Continuous flow mode had a space-time yield nearly two orders of magnitude greater than semi-batch mode. This work can provide guidance for safe, efficient and green synthesis of mononitrotoluene.

Parameter study of waste shiitake substrate/waste polyethylene Co-gasification using Aspen Plus kinetic modeling

Waste Shiitake Substrate, a major agricultural waste in Taiwan, is typically packaged in plastic bags (Waste Polyethylene, PE) during mushroom cultivation process. Consequently, these plastic bags become additional waste that requires proper disposal. In recent years, Taiwan has produced over 150,000 tons of waste shiitake substrate annually, with approximately 1580 tons of plastic bags used for mushroom cultivation. Up to now, there has not been an effective method for handling this waste. This study aims to develop a co-gasification process using the complementary characteristics of WSS and PE. Unlike traditional direct combustion, the co-gasification approach can convert these wastes into cleaner bioenergy. This study aims to develop an Aspen Plus model for a laboratory-scale 1 kWth bubbling fluidized bed gasifier. This model incorporates kinetic reactions and tar formation during co-gasification. The model accurately predicted the experimental results. Different variables were investigated, including gasifier temperature, blending ratio (BR) of the two fuels, mixing ratio (MR) of the gasifying agent, and equivalence ratio (ER). The results showed that hydrogen production correlated positively with the steam-to-carbon ratio in the gasification medium, whereas carbon monoxide (CO) was more affected by the feedstock type and equivalence ratio, with CO reaching its peak at an equivalence ratio of 0.2. When gasifying using only waste shiitake substrate (BR = 0%), at an ER of 0.2, a gasification furnace temperature of 950 °C, and an MR of 100% (pure CO2), the maximum CO mass flow rate in the syngas is obtained. Waste plastics contain significant amounts of volatile matter and no oxygen, leading to increased production of CH4, CO, and H2 during co-gasification with the addition of waste plastic. For plastics, high temperature and low ER conditions promote the production of CO, H2, and CH4 because of the significant tar content, thereby enhancing the Cold gas efficiency (CGE). When the gasification temperature is 950 °C, with 80% polyethylene (BR = 80%) and an ER of 0.1, the highest HHV is achieved. These results can serve as a reference for determining the operational conditions for the scale-up of gasification systems.

A Double-Rotating Ferrofluid Vane Micropump with an Embedded Fixed Magnet

This paper introduces the prototype design, magnetic field analysis and experimental test of a double-rotating ferrofluid vane micropump with an embedded fixed magnet. The micropump is based on the working principle of a positive-displacement pump, as well as the magnetic characteristics and flow properties of magnetic fluid. Through the numerical analysis of the pump cavity magnetic field and the experimental test, the structural parameters of the micropump are optimized reasonably. The pumping flow and pumping height of the micropump were characterized at different driving speeds. The maximum pumping flow rate is approximately 410 μL/min, and the maximum pumping height is approximately 111.4 mm water column. The micropump retains the advantages of simple structure, easy manufacture, flexible control, self-sealing, self-lubrication, low heat production, etc., and can block the pumped liquid backflow. The resulting double-rotating ferrofluid blades can improve pumping efficiency and pumping capacity, and can improve pumping reliability and stability to a certain extent.

A study on the pressure‐driven flow of magnetized non‐Newtonian Casson fluid between two corrugated curved walls of an arbitrary phase difference

AbstractPressure‐driven movement is a fundamental concept with numerous applications in various industries, scientific disciplines, and fields of engineering. Its proper execution is vital for promoting revolutionary innovations and providing solutions in numerous sectors. Therefore, this article scrutinizes the pressure‐driven flow of magnetized Casson fluid between two curved corrugated walls. The geometry of the channel is represented mathematically in an orthogonal curvilinear coordinate system. The corrugation grooves are described by sinusoidal functions with phase differences between the corrugated curved walls. The boundary perturbation method is used to find the analytical solution for the velocity field and volumetric flow rate, taking the corrugation amplitude as the perturbation parameter. The results show that the peak of the velocity increases with the radius of curvature and the width of the channel for a constant pressure gradient. The velocity exhibited a declining trend due to an increase in the Casson fluid parameter. For a sufficiently large corrugation wavenumber, the flow rate decreases, and the phase difference becomes irrelevant. However, the reduction in flow can be minimized by decreasing the channel radius of curvature. In general, a smooth curved channel will give the maximum flow rate for a large corrugation wavenumber. The model can be used to simulate blood flow in arteries with varying geometries and magnetic fields, aiding in the study of cardiovascular diseases and the design of medical devices like stents.

Enhancing the autologous fascial sling procedure: A novel fixation method for treating stress urinary incontinence in female patients.

Synthetic mid-urethral sling surgery has long been the standard surgical treatment for stress urinary incontinence (SUI) worldwide. Using an autologous fascial sling is an alternative to reduce adverse events. We evaluated the treatment outcomes of a novel fixation method applied to the autologous transobturator fascial (TOF) sling procedure for female patients with SUI. A retrospective study was conducted between 2017 and 2020, including 33 patients with SUI who underwent mid-urethral TOF sling surgery with the novel fixation method. We used a self-locking feature (V-LOC™) that was fixed to each side of skin layer above the obturator foramen, and the tension of the fascia sling was adjusted by manipulating the V-LOC™ suture. We analyzed all data collected through questionnaires, including Urinary Distress Inventory-Short Form (UDI-6), Incontinence Impact Questionnaire-Short Form (IIQ-7), Overactive Bladder Symptom Score (OABSS), and Clinical Global Impressions of Improvement (CGI-I). Adverse events were also recorded. This study included 33 female patients aged 39-79 (mean 59.76 years). Following the procedure, there was a significant reduction in the total scores of UDI-6, IIQ-7, and OABSS (preoperative 9.73±4.35, 10.21±5.79, 6.06±4.03 and postoperative 3.52±3.41, 0.85±3.67, 3.06±2.90, respectively) (p < 0.001). Further analysis of each sub-score of the questionnaires revealed significant improvement in certain symptoms. The mean total score of CGI-I was 2.00 ± 0.80. The maximum flow rate was documented for 18 patients, and no significant reduction was observed after the procedure (p = 0.804). Complications reported included voiding dysfunction in two patients (6.1 %), inguinal pain in one patient (3.0 %), and mild delayed wound healing in one patient (3.0 %). This modified TOF sling surgery with a novel fixation method by V-LOC™ suture offers feasibility and adjustability as its main advantages. Our study demonstrated significant improvements in patient outcomes.

Prospective randomized multicenter study to evaluate holmium vs. new thulium fiber laser for prostate enucleation.

Benign prostatic hyperplasia (BPH) commonly causes lower urinary tract symptoms (LUTS) in men. Holmium (HoLEP) and thulium (ThuLEP) laser enucleation are established techniques for BPH treatment. Thulium fiber laser (TFL) for prostate enucleation (ThuFLEP) shows promising outcomes. A prospective randomized multicenter study was conducted. Patients with BPH and LUTS unresponsive to medical therapy were enrolled. Preoperative, surgical, perioperative and postoperative data were recorded with follow-up at 3 and 6 months. The primary outcome was functional improvement, and the secondary outcome was safety in terms of complications. Two hundred patients were included (HoLEP 100, ThuFLEP 100). No significant baseline difference was found between groups. At 3 and 6 months we found statistically significant improvements from baseline for both HoLEP and ThuFLEP in efficacy: International Prostatic Symptoms Score (IPSS), IPSS-Quality of Life (QoL), maximum urinary flow rate (Q<inf>max</inf>), and post-void residual volume (PVR; P<0.05). At 6 months, mean±SD IPSS, IPSS-QoL, Q<inf>max</inf>, and PVR for HoLEP vs. ThuFLEP were 5.8±4.9 vs. 4.8±5.0 points (P=0.57), 1.6±1.4 vs. 0.7±1.1 points (P=0.09), 29.9±12.5 vs. 29.6±8.0 mL/s (P=0.8), and 16.3±17.7 vs. 15.5±13.4 mL (P=0.92), respectively. No intraoperative complication was recorded. No Clavien-Dindo ≥III complications occurred during hospitalization. After 6 months, 8 (8%) and 6 (6%) patients reported mild stress urinary incontinence in HoLEP and ThuFLEP groups, respectively (P=0.24). Urethral stenosis was observed in 3 men (3%) in the HoLEP group and 1 subject (1%) in the ThuFLEP group (P=0.72). HoLEP and ThuFLEP are effective and safe for BPH treatment, with comparable functional outcomes and complication rates at 6 months. Further research is needed to confirm these findings.

Trans-rectovesical pouch urethral-sparing robotic-assisted simple prostatectomy: A case series.

To detail a novel technique of robotic-assisted simple prostatectomy that makes handling the gland protruding into the bladder neck easier and can preserve the urethra and retain ejaculation function as much as possible. This is a prospective case series. Clinical data of 17 male patients who had large volume (>80 mL) benign prostatic hyperplasia (BPH) were enrolled to undergo trans-rectovesical pouch urethral-sparing robotic-assisted simple prostatectomy (usRASP). We adopted the approach through the space between the bladder neck and seminal vesicle to perform a usRASP that can avoid the detrusor skirt and fibrous matrix area of the retropubic prostate. Between the transitional zone and the peripheral zone of the large prostate, the hyperplastic prostatic gland tissue can be enucleated under direct vision while preserving the prostatic urethra and retaining the ejaculatory duct and bladder neck intact. All preoperative, perioperative and postoperative clinical data were collected, and descriptive analysis was performed. The median intravesical prostatic protrusion was 19.3 mm (8.5-32.2). The median operative time was 100 min (75-140), and the median estimated blood loss was 100 mL (10-500). The median time to catheter removal was 7 days (5-7), with a median postoperative hospital stay of 2 days (2-4). After at least 6-month follow-up, the median maximum urine flow rate and postvoid residual volume were 40.1 mL/s (12.7-52.4) and 15 mL (5-23), respectively; the median International Prostate Symptom Score and Quality of Life score were 0 (0-6.3) and 1 (0-3), respectively; and the median total prostate-specific antigen was 0.84 ng/mL (0.15-1.01). All patients successfully underwent usRASP. Fifty-eight percent of patients with normal ejaculation function before surgery can still retain normal ejaculation function. We described a new approach to performing usRASP. This new method remarkably improved the voiding function, maintained antegrade ejaculation and did not increase the post-operative complications.

“Component flow” conditions and its effects on enhancing production of continental medium-to-high maturity shale oil

Based on the production curves, changes in hydrocarbon composition and quantities over time, and production systems from key trial production wells in lacustrine shale oil areas in China, fine fraction cutting experiments and molecular dynamics numerical simulations were conducted to investigate the effects of changes in shale oil composition on macroscopic fluidity. The concept of “component flow” for shale oil was proposed, and the formation mechanism and conditions of component flow were discussed. The research reveals findings in four aspects. First, a miscible state of light, medium and heavy hydrocarbons form within micropores/nanopores of underground shale according to similarity and intermiscibility principles, which make components with poor fluidity suspended as molecular aggregates in light and medium hydrocarbon solvents, such as heavy hydrocarbons, thereby decreasing shale oil viscosity and enhancing fluidity and outflows. Second, small-molecule aromatic hydrocarbons act as carriers for component flow, and the higher the content of gaseous and light hydrocarbons, the more conducive it is to inhibit the formation of larger aggregates of heavy components such as resin and asphalt, thus increasing their plastic deformation ability and bringing about better component flow efficiency. Third, higher formation temperatures reduce the viscosity of heavy hydrocarbon components, such as wax, thereby improving their fluidity. Fourth, preservation conditions, formation energy, and production system play important roles in controlling the content of light hydrocarbon components, outflow rate, and forming stable “component flow”, which are crucial factors for the optimal compatibility and maximum flow rate of multi-component hydrocarbons in shale oil. The component flow of underground shale oil is significant for improving single-well production and the cumulative ultimate recovery of shale oil.

Clinical Outcomes in Patients With Hypocontractile Bladders Undergoing Holmium Laser Enucleation of the Prostate

To compare post-operative outcomes in patients who underwent holmium laser enucleation of the prostate (HoLEP) for benign prostatic hyperplasia (BPH) and had urodynamic evidence of bladder hypocontractility versus those with normocontractile bladders. We retrospectively reviewed HoLEP patients with pre-operative urodynamic studies at a single institution, categorizing them into normocontractile and hypocontractile groups based on the bladder contractility index (BCI) (hypocontractile defined as BCI < 100). Post-void residual (PVR) volume was measured at 6 weeks and 6 months. Secondary outcomes included maximum flow rate (Qmax) and catheterization status. Among 114 HoLEP patients with pre-operative urodynamic data, 49 had hypocontractile bladders. The median pre-operative PVR was 305 (202-446) ml in the hypocontractile group, higher than the median PVR of 190 (60-361) ml in the normocontractile group (p=.013). At 6 weeks post-op, the median PVR was higher in the hypocontractile compared to normocontractile group [38 (3-61) vs. 5 (0-44) ml, p=.016], but at 6 months post-op there was no significant difference [18 (0-39) vs. 12 (0-70) ml, p=.97]. Among men who were catheter-dependent pre-operatively, 98% of hypocontractile and 100% of normocontractile patients were catheter-free postoperatively. Qmax and symptom scores were similar at both follow-up time points. HoLEP can be an effective surgical option for BPH patients with hypocontractile bladders, including those who are catheter-dependent, with minimal differences in post-operative voiding parameters compared to those with normal bladder function.

Evaluation of learning curves for contact laser vaporization of the prostate using the 980 nm diode laser for benign prostatic hyperplasia.

We investigated the background of patients who underwent contact laser vaporization of the prostate (CVP) surgery and the learning curve of the operators. A total of 207 patients who underwent CVP surgery for benign prostatic hyperplasia between August 2018 and March 2023 were included in this study. Patient background, perioperative results, pre- and postoperative urinary flow tests, and complications were collected retrospectively. We enrolled 12 doctors who were divided into expert (five doctors) and novice (seven doctors) groups based on the number of TURP experiences before CVP. The median patient age was 73 years (51-92 years) and prostate volume was 56 cc (15-190 cc) with no difference between the expert and novice groups. Complications included urinary retention (eight cases), hematuria (four), urinary tract infection (four), intraoperative perforation (two), and postoperative stricture (one). Both cases of intraoperative perforation occurred in the novice group. The expert group had a significantly shorter operative time (38 vs. 66 min) and a higher operative efficacy of prostate volume divided by operative time (1.43 vs. 0.88 cc/min). Postoperatively, IPSS, quality of life scores, and postvoid residual urine volume decreased, and maximal flow rate increased; however, there was no significant difference between the groups. The expert group showed stable operative time and operative efficacy after about five to eight cases, while the novice group showed stable after about 15 cases. Our findings suggest that CVP was safely performed at our hospital, and operators with limited experience in TURP can achieve stable perioperative results.

Experimental investigation on the influence of gasoline injection pressure on the hydrogen knock limit and performance of a hydrogen–gasoline dual fuel engine

This study experimentally investigated the influence of gasoline injection pressure (GIP) on the performance and hydrogen knock limit of a gasoline direct-injection hydrogen–gasoline dual-fuel engine. The GIP was varied from 50 to 140 bar, and hydrogen was introduced at a step size of 2 LPM until knock onset at spark timings of 4° and 12° CA before top dead center (BTDC). The hydrogen knock limit was extended at a higher GIP, with maximum hydrogen flow rates of 10 and 16 LPM at 12° CA and 4° CA BTDC, respectively. Increasing the GIP and retarding the spark timing negatively affected brake thermal efficiency, brake mean effective pressure, and in-cylinder pressure. The CO2 and NOx emissions decreased, and the CO emissions increased with an increase in the GIP. The cyclic variation increased considerably with GIP. However, hydrogen blending exhibited a completely opposite trend to that of GIP.

MagnetoStalsis: Generating Peristalsis in an Artificial Bowel for Treatment of Short Bowel Syndrome

Efforts to develop an artificial intestine for treatment of short bowel syndrome have thus far failed to achieve coordinated peristalsis. To address this, we introduce an implantable, biomimetic, magnetically-actuated peristaltic pumping apparatus. The system consists of a magnetic pump surrounding an intestinal graft and a rotating external magnetic field generator that produces peristaltic motion in the graft as the field direction alternates. We performed computational finite element modeling to simulate deformation and stress concentration on the pump. We then tested the ability of the system to produce fluid flow through porcine subintestinal submucosa at actuation frequencies from 0 Hz to 4 Hz. The system achieved a maximal flow rate of 6.03 mL/min at 3 Hz actuation frequency, which is in the physiological range of human intestinal flow rates. This device represents a novel proof-of-concept for achieving untethered peristalsis in an implantable intestinal graft that is primed for preclinical testing in animal models of short bowel syndrome.

Congestion Transition on Random Walks on Graphs.

The formation of congestion on an urban road network is a key issue for the development of sustainable mobility in future smart cities. In this work, we propose a reductionist approach by studying the stationary states of a simple transport model using a random process on a graph, where each node represents a location and the link weights give the transition rates to move from one node to another, representing the mobility demand. Each node has a maximum flow rate and a maximum load capacity, and we assume that the average incoming flow equals the outgoing flow. In the approximation of the single-step process, we are able to analytically characterize the traffic load distribution on the single nodes using a local maximum entropy principle. Our results explain how congested nodes emerge as the total traffic load increases, analogous to a percolation transition where the appearance of a congested node is an independent random event. However, using numerical simulations, we show that in the more realistic case of synchronous dynamics for the nodes, entropic forces introduce correlations among the node states and favor the clustering of empty and congested nodes. Our aim is to highlight the universal properties of congestion formation and, in particular, to understand the role of traffic load fluctuations as a possible precursor of congestion in a transport network.

Evaluation of the learning curve for Thulium fiber laser enucleation of prostate (ThuFLEP): retrospective study of a single-surgeon experience in real-world settings.

To assess the learning curve of Thulium Fiber Laser Enucleation of prostate (ThuFLEP) of a single surgeon inexperienced in laser endoscopic enucleation of prostate (EEP). We retrospectively analyzed all patients with benign prostate hyperplasia undergoing ThuFLEP at our center between January 2022 and August 2023 by one surgeon. Inclusion criteria were International Prostate Symptom Score > 7, prostate volume < 200g, and maximal urinary flow rate < 15 mL/s. The surgeon was inexperienced in laser EEP and trained by watching educational videos of ThuFLEP before starting to perform the procedure under mentoring during the first 4 cases. Procedural data (enucleation and morcellation efficiency, complications) and functional results up to 3 months were evaluated. Patients were divided into 4 cohorts of 20 consecutive cases to evaluate outcomes evolution throughout time. The mean age of the patients was 69.9 years (SD 7.8) and mean prostate volume was 89.9g (SD 25.8). Preoperative functional parameters were comparable between the groups. Mean enucleation efficiency (EE) ratio and morcellation efficiency (ME) ratio reached respectively 0.78g/min (SD 0.55) and 2.49g/min (SD 1.03) and both variables significantly increased from group 1 to group 3 (p < 0,001). Perioperative complications remained low throughout the caseload with similar significant 3-month functional improvements between all groups. This is the first study to evaluate ThuFLEP learning curve for a single surgeon inexperienced in laser EEP with limited mentoring. Under these real-world conditions, nearly 60 cases were needed to complete the learning curve with a complications rate remaining low throughout the training process.

Safety Design Criteria for the Emergency Discharge of Hazardous Substances in Small and Medium-Sized Polystyrene Polymerization Batch Reactor Processes: Case Study of the South Korean Chemical Industry

In small and medium-sized chemical plants, explosions constantly occur owing to runaway reactions because of equipment defects or human errors and so on. Accordingly, in this study, based on a case study of an explosion accident in a polystyrene reactor in South Korea, the dis-charge capacity of hazardous substances during a runaway reaction is reviewed and a method for safely disposing of hazardous substances is proposed. Using an acceleration rate calorimeter, the maximum temperature rise rate during the polystyrene reaction was determined, and it was determined that 355,643 kg/h can flow during a runaway reaction. A 30-inch header size was then selected to consider maximum flow rate, and two 81.4 m2 heat exchangers were selected to completely condense the hazardous substances. As a result, the facilities at the workplace were configured to condense all hazardous substances and discharge them into the atmosphere. If this method is used, it is believed that the lives of workers can be protected by preventing fires and explosions in small and medium-sized chemical plants in which runaway reactions may occur.

Design, development, and testing of active valve piezo-hydraulic pump

Valves play a major role in rectifying the fluid flow through piezo-hydraulic pumps, which may be active or passive. Passive valves operate due to changes in the fluid pressure whereas active valves are operated through control signals. This paper presents a novel design of an active valve chamber assembly for a piezo-hydraulic pump. It is a novel design since none of the research publications has addressed the application of a Flexurally amplified piezoelectric actuator (FAPA) for valve actuation in active valve chamber assembly. The piezo-hydraulic pump design is done using solid edge design software. FAPA’s are used for pumping and valve actuation. Structural analysis with experimental verification for the valve chamber component is presented. The valve opening and the pumping displacement are mathematically modeled in MATLAB Simulink software. Also, mathematical simulations for pump flow rates at different actuation frequencies and voltage are discussed. The piezo-hydraulic pump components are fabricated and assembled with the actuators. Experimental investigations on the flow rate performance of the active valve piezo-hydraulic pump are carried out with changing frequency and voltage amplitude of actuators. The interpretation of results is done by comparing the experimental and simulation results. During experiments, the pump delivered a maximum flow rate of 4.5 ml min−1 at 140 V when actuated at 0.25 Hz actuation frequency.

A single-coil-driven tristable electromagnetic mini valve with multiple working states

Electromagnetic mini valves have attracted great interest in medical devices for their excellent performance and high integration. In state-of-the-art research, most mini valves have only two working states, while certain ones featuring three to four working states necessitate multiple driving sources. To solve these problems, a novel tristable electromagnetic mini valve with three stable working states achieved by a single coil was proposed. The actuation mechanism of this mini valve mainly comprises a cylindrical magnet (CM) and a ring magnet (RM) coaxially arranged. In the absence of current through the coil, the stability of the magnets is upheld by their mutual repulsion and the attraction of the iron core. Upon modifying both the magnitude and orientation of the current, one of the magnets traverses from one terminus to another each time. The two magnets are either stationary at the start point or the endpoint. Thereby, four position relationships are formed, three of which are stable. The minimum response time and energy consumption are 3.75 ms and 0.013 J, respectively. The working pressure of the valve ranges from 0 to 200 kPa. The maximum flow rate and back pressure reach 10.5 L/min and 180 kPa, respectively. A tristable design contributes to lower energy consumption, and the three-working-state function actuated by a single coil facilitates a diminution in the size of the mini valve. Consequently, a diminished quantity of valves is realized for multiple degree-of-freedom pneumatic actuator control, which promotes the miniaturization of the whole system. The dimensions and performance of the proposed mini valve substantiate its potential in pneumatic medical devices.

Theoretical and experimental analysis of evaporative cooling with hydrophilic screen mesh on condenser surface

In this study, we theoretically and experimentally analyzed the effect of evaporative cooling on the external thermal resistance of a condenser with a water-filled hydrophilic screen mesh. To calculate the external thermal resistance of the condenser theoretically, the external thermal resistance model was developed, considering evaporative cooling in the screen mesh. The evaporative mass flow rate in the screen mesh was calculated using the Lewis number, which can convert heat transfer to mass transfer. Especially, the maximum flow rate absorbed by the screen mesh was theoretically determined by the capillary limit. In experimental approach, hydrophilic screen meshes with mesh numbers M100, M150, and M200 were manufactured and attached to an aluminum plate simulating the condenser surface. The external thermal resistance of the condenser was measured. Based on the results, the theoretical model was well matched with experimental results. The effects of the air velocity, mesh number, and heat flux on the external thermal resistance of the condenser with evaporative cooling in the water-filled hydrophilic screen mesh were investigated. Finally, it is shown that the external thermal resistance of the condenser with evaporative cooling using the water-filled hydrophilic screen mesh can be reduced up to an average of 92 %.