Bypass Tube Research Articles

Efficiency enhancement in a heat-driven single-unit thermoacoustic refrigeration system

Heat-driven thermoacoustic cooling technology provides promising alternatives for eco-friendly refrigeration systems due to its high reliability and minimal environmental impact, meanwhile facing limited efficiency compared to current prevailing cooling technologies. The present work introduces an innovative bypass configuration in heat-driven thermoacoustic refrigeration systems aimed at enhancing the energy coupling between the engine and refrigerator, thereby enhancing system efficiency, particularly when the sources temperature is high. The acoustic power diversion mechanism of the bypass tube is firstly explored in an ideal thermoacoustic core unit through theoretical analysis. This core unit is subsequently studied in Sage platform and integrated into an actual single-stage looped traveling-wave thermoacoustic refrigeration system, respectively, and the effects of the bypass tube dimensions and operating conditions on the system are investigated. Furthermore, a comparative analysis is conducted between the proposed bypass tube-based system and the conventional bypass tube-free system, considering aspects such as system performance, key parameter distribution, and exergy loss analysis. The results demonstrate a significant efficiency enhancement, with a 68.8% increase in Coefficient of Performance (COP) and a 6.2 percentage point boost in relative Carnot efficiency compared to the system without a bypass tube. Additionally, the impact of the bypass dimensions and the DC flow introduced by the bypass tube on the system performance is further discussed at a numerical level. These findings offer valuable insights and serve as a reference for the future development of more efficient thermoacoustic refrigeration systems.

Real-Time Detection of Circulating Thrombi in an Extracorporeal Circuit Using Doppler Ultrasound: In-Vitro Proof of Concept Study.

Thromboembolic stroke continues to be by far the most common severe adverse event in patients supported with mechanical circulatory assist devices. Feasibility of using Doppler ultrasound to detect circulating thrombi in an extracorporeal circuit was investigated. A mock extracorporeal circulatory loop of uncoated cardiopulmonary bypass tubing and a roller pump was setup. A Doppler bubble counter was used to monitor the mean ultrasound backscatter signal (MUBS). The study involved two sets of experiments. In Scenario 1, the circuit was sequentially primed with human blood components, and the MUBS was measured. In Scenario 2, the circuit was primed with heparinized fresh porcine blood, and the MUBS was measured. Fresh blood clots (diameter <1,000 microns, 1,000-5,000 microns, >5,000 microns) were injected into the circuit followed by protamine administration. In Scenario 1 (n = 3), human platelets produced a baseline MUBS of 1.5 to 3.5 volts/s. Addition of packed human red blood cells increased the baseline backscatter to 17 to 21 volts/s. Addition of fresh frozen plasma did not change the baseline backscatter. In Scenario 2 (n = 5), the blood-primed circuit produced a steady baseline MUBS. Injection of the clots resulted in abrupt and transient increase (range: 3-30 volts/s) of the baseline MUBS. Protamine administration resulted in a sustained increase of MUBS followed by circuit thrombosis. Doppler ultrasound may be used for real-time detection of circulating solid microemboli in the extracorporeal circuit. This technology could potentially be used to design safety systems that can reduce the risk of thromboembolic stroke associated with mechanical circulatory support therapy.

The use of Montgomery salivary bypass tubes and pharyngocutaneous fistula following salvage laryngectomy.

Pharyngocutaneous fistula (PCF) is the most common complication to follow total laryngectomy (TL) and is associated with increases in length of hospital stay and with a need for revision surgery or readmission, as well as with delays in return to oral diet. Patients who require salvage TL (STL) or primary (chemo)radiation therapy are at higher risk for developing PCF. Due to the quality-of-life burden of PCF on patients, limiting this occurrence is crucial. We conducted a retrospective cohort study of patients undergoing STL with placement of Montgomery salivary bypass tube (MSBT)™ for at least 2 weeks duration between 2013 and 2017 at a single institution. Our patients all underwent free flap reconstruction. Our primary outcome of interest was development of PCF. Secondary outcomes included demographics, previous treatment, base of tongue (BOT) involvement, extent of defect, concurrent neck dissection (ND), and margin status. Univariate χ 2 analysis was used to evaluate factors associated with PCF. Forty-four patients underwent STL with Montgomery tube placement and free flap reconstruction. Eight developed PCF (18.2%). The average age was 61.6 years; 36 patients were male (81.8%), whereas eight patients were female (18.2%). There was no association between PCF and previous chemoradiation versus radiation (15.8% vs. 33.3%, P < 0.30), BOT involvement versus not (11.1 vs. 22.2%, P < 0.38), circumferential versus partial defect (18.8% vs. 17.9%, P < 0.94), ND versus none (10% vs. 25%, P < 0.20), or margin status. PCF complicated 18.2% of STL cases at our institution and was not associated with differences in primary treatment modality, presence of concomitant ND, extent of pharyngeal defect, BOT involvement, or positive frozen or permanent surgical margin.

Institutional experience with total pharyngectomy reconstruction: Exploring the role of the salivary bypass tube.

There is a lack of consensus regarding the effectiveness of salivary bypass tubes during total pharyngectomy reconstruction to prevent pharyngocutaneous fistula or pharyngoesophageal stricture. Our study examined tubed free flap reconstruction outcomes for total pharyngectomy defects over 11 years at a single tertiary referral center. We compared postoperative fistula and stricture rates between two groups: those with salivary bypass tubes inserted during reconstruction and those without. Among 36 patients, 26 had radial forearm, and 10 had anterolateral thigh free flap reconstruction. 53% received salivary bypass tubes. However, the tubes did not significantly reduce the relative risks of fistula or stricture. Notably, neck dissection during total pharyngectomy was associated with increased fistula incidence. Minor salivary bypass tube-related complications affected 21% of subjects. The role of salivary bypass tubes in total pharyngectomy reconstruction remains uncertain.

Retrospective radiological analysis to establish anatomical variation in angulation between medial canthus and the middle turbinate, for optimal positioning of Lester Jones Lacrimal bypass tubes in treatment of Epiphora.

To determine the optimum angle for placement of Lester Jones lacrimal bypass tube using fixed radiological markers on CT scan head with axial and coronal cuts, as well as analysing the anatomical variation and range of angulation between individuals within our local population. A retrospective radiological study conducted on a randomly selected sample of 384 adult patients in a UK Teaching Hospital. The angle between the medial canthus and the middle turbinate was measured on CT scans of the head using fixed radiological anatomical landmarks and analysed using the IMPAX software. Patients with orbital or nasal fractures, as well as those with history of surgical procedures involving the facial bones, were excluded. The accuracy of our measurements was validated using three dimensional (3D) CT head reconstruction technology. Analysis of the results showed a range of angulation between 28-45 degrees, with a mean angle of 36.99 ± 4.78 SD. There was no significant correlation found when comparing the different age groups using the One Way ANOVA test. Furthermore, a non-significant correlation was found between males and females when their mean angles were compared using the independent t-test. Our study showed that the ideal angle for insertion of Lester Jones tube would be between 30-45 degrees, with a mean of 37 degrees. No significant correlation was found between the age of the patient and the ideal angle of insertion of Lester Jones tube. Moreover, no significant difference was found in the angle measurements between males and females.

An Unusual Case: Nasolacrimal Stent Penetrating the Oral Cavity.

Lacrimal bypass tubes create a fistula from the conjunctiva to the lacrimal sac or the nasal cavity. Fluoroscopic nonoperative placement of a plastic stent has shown successful results in the treatment of epiphora. Polyurethane lacrimal stents have been reported as a safe, easy, non-surgical treatment in the treatment of distal lacrimal obstruction. Recurrence due to stent occlusion of the granulation tissue is common. Stent displacement is very rare. We presented the first case of the stent protruded into the mouth in the literature.

Experimental study on reducing water hammer effects in uPVC pipes using rubber bypass tubes

Applying bypass (parallel) flexible tubes made of rubber was studied for the first time, affixed on an uPVC pipeline upstream of a regulation valve, to mitigate water hammer effects by employing simple and readily available tools. Ninety-two experiments were conducted to analyze the influence of the flexible tubes' elasticity Modulus, lengths, and inner volumes. The results demonstrate that implementing bypass rubber tubes substantially reduces the head rise (ΔH), even for shorter tube lengths. The reduction rate of ΔH shows an initial rapid decline followed by a gradual decrease as the tube length increases. Besides, the bypass rubber tube utilization significantly reduced the hammer celerity and increased both the water hammer's characteristic time and the damping rate of the hammer. The elasticity Modulus of the rubber tube exhibits a significant effect on ΔH, displaying a reverse relationship. Finally, ΔH decreases as the inner volume of the rubber tubes increases.

Pharyngocutaneous Fistula after Laryngectomy: An Umbrella Systematic Review to Uncover Lacunae in Meta-Analyses

Objective—The objective of this study was to systematically assess meta-analyses to determine the lacunae in the literature for PCF following laryngectomy. Methods—Bibliometric analysis were carried out on meta-analyses on PCF after total laryngectomy for laryngeal cancer in the PubMed database. Results—Twenty-four meta-analyses were considered eligible and chosen for analysis. Six meta-analyses (25%) focused on the risk factors for PCF in TL. Four meta-analyses (16.6%) focused on the role of the onlay flap. Four meta-analyses (16.6%) focused on the timing of feed initiation. Three meta-analyses (12.5%) focused on using a stapler for pharyngeal closure. Two meta-analyses focused on types of pharyngeal reconstruction. Other meta-analyses analyzed the use of salivary bypass tubes, the method of pharyngeal closure, organ preservation protocols on PCF, primary and secondary TEP, and the effect of non-surgical treatment on PCF. Conclusion—Despite plenty of published meta-analyses, there is a lack of scrutiny on certain critical aspects of PCF.

An experimental investigation on the influence of condenser bypass area for the transient and steady-state heat-transfer performance of heat pipes

Fundamentally, an effective method for improving the performance of transient and steady-state heat transfer is reducing the flow resistance at the phase-change interface based on the counter flow of vapor and liquid within a typical heat pipe. The flow resistance at such an interface is proportional to the volume flow rates of liquid and vapor. Therefore, the flow resistance at the interface can be reduced by limiting the mass flow rate of vapor or liquid. In this study, experiments were performed on a liquid bypass to improve the steady-state thermal performance of heat pipes. A separate bypass tube allowed some liquid to be subcooled in the condenser to bypass the evaporator without passing through the heat pipe. Three liquid-bypass ports were designed and fabricated in a condenser to experimentally investigate the influence of the bypass port area on the thermal performance of the heat pipe under steady-state operation. An on/off valve was attached to each bypass tube port in the condenser to control the bypass flow rate. The results showed that the thermal resistance, an evaluation index of the performance of steady-state heat transfer, generally decreased with an increase in the bypass port area of the condenser. The thermal resistance of a heat pipe with a horizontal tilt angle and one at an inclination angle of 50° decreased by up to 25.5% and 51.6%, respectively.

Influence of condenser bypass port area on maximum thermal load of heat pipe

Experimental works have been conducted to enhance the performance of heat pipes by focusing on the maximum thermal load, which is a very important performance indicator. Ordinal operation on the heat pipe occurs when the capillary force is sufficient to overcome the flow resistance of the working fluid. Therefore, one method of increasing the maximum thermal load is to reduce the flow resistance of the liquid and vapor with counter flow in the system. Moreover, the flow resistance of the working fluid is immediately dependent on the mass flow rate, and reducing the flow rate can effectively increase the maximum thermal load. The liquid bypass technique is one method of alleviating the flow resistance of the working fluid inner side a heat pipe container. In this work, a modified heat pipe system with one liquid bypass tube was manufactured and investigated, with the bypass tube being constructed so that some of the working fluid inside the condenser could be bypassed to an evaporator not going through a heat pipe interspace with vapor and liquid counterflow. Three bypass ports were located in the condenser; hence, the influence of bypass port area on thermal of heat pipe performance was investigated experimentally. Mass flow rate control valves were attached to these three bypass ports, and the maximum thermal loads according to the activation of each port were experimentally measured. The maximum thermal load in a horizontal position increased by up to 45.8% with an increase in the area of the bypass port. With the increase of the activated bypass port area, the condenser wall temperature increased by up to 15.9 °C.

Superhydrophobic blood-repellent tubes for clinical cardiac surgery

Superhydrophobic coatings are gaining importance not only in military technology, industrial engineering, power systems and transportation, but also in food science and biomedicine, where they have enormous potential for real-time applications. Many research institutes have recently been working on the development of superhydrophobic blood-repellent tubes to replace clinical heparin-coated tubes during ECMO therapy, but biological toxicity and high blood adhesion have significantly hampered their practical applications. In this study, we created a cardiopulmonary bypass tube with good superhydrophobicity and blood repellency. In terms of biotoxicity, coagulation time, protein and platelet adsorption, the results show that the superhydrophobic-treated tube clotted in 36 min, compared to 21 min for a clinical Bioline heparin-coated tube and 14 min for bare PVC tube. When compared to the bare PVC tube, the clotting time of the superhydrophobic-treated tube was increased by 157% due to the Cassie-Baxter wetting state of the resulting superhydrophobic blood-repellent coating. Meanwhile, the protein and platelet adsorption on the superhydrophobic-treated tube were decreased by 32% and 74%, respectively. It should be noted that we were the first to explain the superhydrophobic anti-platelet adsorption mechanism from the perspective of inhibiting thromboxane-A2 secretion during blood coagulation. Clarification of platelet activation process and activating substances is vital for understanding the anticoagulant properties of superhydrophobic coatings. On the other hand, non-inflammatory response of the organism was confirmed in the vivo experiments and the cell viability after a 48-hour cytotoxicity assay was about 101%, indicating that the superhydrophobic-treated tubes are non-toxic.

Salivary bypass tube in managing persistent and large pharyngocutaneous and tracheoesophageal fistulas: a series of seven cases

BackgroundA salivary bypass tube (SBT) is a silicone tube that directs oral content from the mouth to the esophagus. We studied a series of seven cases of persistent and large neck fistulas of different aetiologies to assess the beneficial use of SBTs in each case.Case presentationA total of seven patients underwent SBT insertion, six cases were post-total laryngectomy with underlying laryngeal malignancy, and one case was poor wound healing of a neck abscess after extensive drainage. Five cases have pharyngocutaneous fistula (PCF) and two cases have tracheoesophageal fistula (TEF), and all of the cases have failed conservative and multiple surgical management for fistula closure, with some concurrently having neopharynx stenosis. Post-insertion, all patients were able to eat orally after day 2 to 1-week. The duration of tube usage was one month in the three cases of persistent PCF post-operatively, and in two cases, the fistula was healed and the tube was removed without fistula recurrence. The other four cases (three post-radiotherapy fistulas and one stoma recurrence) were planned for lifelong use, with the duration of usage ranging from 4 months to 3 years. The outcome is their fistula is dry, and they tolerate the tube well. There were no intraoperative or immediate postoperative complications, and no complications were observed in the temporary usage cases. Among the patients who had to use the tube for a longer term, one had localised pressure necrosis of regional soft tissue that resolved after tube adjustment, and another had a loose-fitting tube that displaced distally into the oesophagus and resolved with a larger tube.ConclusionsSBT is safe, easy-to-apply, reduces morbidity, improves mental health, reduces inpatient stay, and overall improves the patient's quality of life in the management of persistent and large TEF and PCF for temporary or long-term usage.

Multi-coupled biomimetics for tire noise reduction

To explore ways of reducing tire noise, a 205/55R16 KR10 semi-steel radial tire was used as the research object. Vibration noise and aerodynamic noise were analyzed using the modal transfer vector method and the computational fluid dynamics method respectively. The cat’s paw pads can swivel left to right when walking, which dampens vibrations. The left-right pivoting characteristics of the cat’s paw pads are successfully transplanted into the tire by opening asymmetric bypass tube grooves in the tread to form a bionic tire. The results showed that the bionic tire can effectively decrease vibration noise. However, without considering the bypass tube’s resonant muffler acoustic noise reduction, the bionic tire increased aerodynamic noise. According to the multi-coupling bionic concept, the shark scale shield structure is coupled based on the bionic tire, and the shark-like structure is targeted at the sound source to form a multi-coupled bionic tire. Characterized by the left and right pendulum positive damping motion of the cat’s paw pad as well as the non-smooth damping structure of the shark scale shield, the multi-coupled bionic tire jointly reduced the tire vibration noise and aerodynamic noise.

Management of Locally Advanced Laryngeal Cancer—From Risk Factors to Treatment, the Experience of a Tertiary Hospital from Eastern Europe

Laryngeal cancer is an important oncological entity in which prognosis depends on the establishment of appropriate preventive and diagnostic measures, especially in high-risk populations. We present a retrospective two-year study (January 2021 to December 2022) with 152 patients diagnosed with laryngeal cancer from a tertiary hospital in Romania. The average age of the patients was 62 years old for both sexes, with a range from 44 to 83 years. The most frequent symptom was dysphonia with or without dyspnea in 142 cases (93.42%), followed by dyspnea alone in nine patients (5.92%) and dysphagia in one case (0.66%). Surgical treatment in this study consisted of partial laryngectomy (CO2 laser transoral tumor ablation, supraglottic horizontal laryngectomy or hemilaryngectomy), or total laryngectomy. The main treatment was total laryngectomy (63%). For the eight patients with initial organ preservation treatment, the average time of recurrence was about two-and-a-half years. For the four patients who underwent a total circular pharyngo-laryngectomy, the upper digestive tract needed to be rebuilt with a salivary bypass tube or with a tubed myocutaneous flap from the major pectoralis muscle. One strong point is characteristic of the study group in gathering patients with advanced stages of laryngeal carcinoma candidates for salvage surgery and extended reconstruction methods. The development of new prevention protocols is mandatory in Eastern European countries.

A Novel Endoscopic Technique for Positioning Salivary Bypass Tubes.

A Novel Endoscopic Technique for Positioning Salivary Bypass Tubes.

Experimental investigation of a novel gas bypass in two-pass microchannel evaporator for performance enhancement

The maldistribution of refrigerant flow in two-pass microchannel evaporator will deteriorate heat transfer performance and result in dry evaporating phenomenon. In this article, the experimental method was used to mainly explore the performance of heat transfer and the flow characteristics in the two-pass microchannel evaporator with superheated gas bypass tube installed in the top of middle header, which performance was compared with that of the evaporator without gas bypass. The results showed that the refrigerant gas bypass caused little change on heat transfer and heat transfer coefficient in various testing conditions, but the refrigerant distribution uniformity in the second pass can be significantly enhanced. The two-phase length occurred in the flab tubs increased and the superheat degree obviously decreased when the superheated gas was released through capillary tube. Compared with the microchannel evaporator without gas bypass tube, the maximum increase of the two-phase length in each flat tube can reach 2.2–4 times in different air velocity and refrigerant flow rate. And the maximum decrease of the superheat degree was up to 33 % in the case of 2 m/s air velocity. The results showed that the gas bypass can make the refrigerant distribution more uniform between the flat tubes which will contribute to the reduced superheat degree, use rate of heat exchange area improvement and the relieved dry evaporating in two-pass microchannel evaporator.

Volatility of aircraft exhaust ultrafine particles inferred from field measurements at Narita International Airport

We conducted field measurements of aerosols near a runway at Narita International Airport (NRT) in February 2018 to characterize the physical and chemical properties of aircraft exhaust ultrafine particles (UFPs; diameter <100 nm). An ultrafine condensation particle counter (UCPC; d50 = 2.5 nm), a condensation particle counter (CPC; d50 = 10 nm), and an engine exhaust particle sizer (EEPS; 6.0–523 nm) were used to measure the particle number concentrations and size distributions in ambient air. The sample flow for the UCPC and CPC was passed through an evaporation tube for heated measurements (150 °C, 250 °C, or 350 °C) or through a bypass tube for unheated measurements. The evaporation tube temperature (Ttube) of 350 °C was used as a threshold point for the separation of volatile and non-volatile particles. The removal efficiency of the volatile particles at intermediate temperatures (<350 °C) was evaluated in the laboratory using triacontane (C30) and tetracontane (C40) as test compounds. The critical temperature at which the laboratory-generated 30-nm C30 and C40 particles were almost entirely removed was ∼130 °C and ∼250 °C, respectively. The particle number concentrations measured by the UCPC, CPC, and EEPS at NRT were used to investigate the volatility of aircraft exhaust UFPs under real-world operating conditions. The number fraction of the non-volatile particles strongly depended on the geometric mean diameter (GMD) of the unheated particle number size distributions, whereas the vaporization temperature of the volatile particles did not exhibit significant dependency on GMD. The particle number fraction remaining, calculated for the selected evaporation tube temperature (Ttube), indicates that ∼50% and ≳ 90% of the volatile particles were removed at Ttube = 150 °C and 250 °C, respectively, on a number basis. These results suggest that a large fraction (more than half by number) of the volatile UFPs emitted from aircraft was equally or less volatile than the 30 nm pure C30 particles and only a small fraction of the volatile UFPs was equally or less volatile than the 30 nm pure C40 particles.

Salivary bypass tube in total laryngectomy: Systematic review and meta-analysis.

The aim of this study is to determine whether the preventive positioning of a salivary bypass tube (SBT) after total laryngectomy (TL) reduces the incidence of postoperative pharyngocutaneous fistula (PCF) and pharyngeal stenosis (PS). This study was conducted in conformity with the PRISMA statement. 1960 patients with a median age of 62.0 years were included. A SBT was placed in 980 (50%) patients (SBT group). The cumulative PCF incidence in the SBT group was 15.8% (95% CI: 9.3-23.6). The measured pooled OR comparing PCF incidence in patients with SBT compared to those without was 0.40 (95% CI: 0.24-0.65). The pooled PS incidence in the SBT group was 12.3% (95% CI: 5.4-21.6). The measured pooled OR comparing PS incidence in patients with SBT compared to those without was 0.43 (95% CI: 0.24-0.65). PCF and PS could be prevented by the intra-operative placement of a SBT.

Heat transfer performance of loop heat pipe for space vehicle thermal control under bypass line operation

This study analyzed the experimental results regarding the heat transfer performance of a loop heat pipe (LHP) with a vapor bypass line and a polypropylene fiber capillary wick. The LHP with the bypass tube between the vapor channel and liquid chamber was fabricated, tested, and analyzed. A control valve was attached to the inlet of the bypass line to manually switch between the bypass line operating mode and the normal operating mode. The polypropylene capillary wick generated the capillary pressure to operate the LHP. The container and tubing system of the LHP were of stainless steel, and methanol was used as the working fluid. The planar dimensions of the LHP with a flat evaporator were 40 mm × 50 mm. The study investigated the effect of the auxiliary loop on the LHP. The effects of the bypass line were investigated in terms of the minimum start-up thermal load, start-up thermal performance, and steady-state performance. The minimum start-up thermal load of the LHP was reduced by up to 63% under the bypass line operation compared with the normal operation. The temperature overshoot in the evaporator outer wall was eliminated during the start-up under the bypass line operation. Furthermore, the steady-state heat transfer performance was favorably enhanced at high thermal loads under the bypass line operation.

The use of salivary bypass tube reduces the risk of pharyngo-cutaneous fistulas after salvage total laryngectomy.

Background: The aim of this retrospective study was to assess the efficacy of Salivary Bypass Tube (SBT) for preventing pharyngo-cutaneous fistula (PCF) in a recent cohort of patients who underwent primary and salvage total laryngectomy (TL).