Performance Simulation of a Double Tube Heat Exchanger Based on Different Nanofluids by Aspen Plus

A heat exchanger’s performance depends heavily on the operating fluid’s transfer of heat capacity and thermal conductivity.Adding nanoparticles of high thermal conductivity materials is a significant way to enhance the heat transfer fluid’s thermal conductivity.This research used engine oil containing alumina(Al_(2)O_(3))nanoparticles and copper oxide(CuO)to test whether or not the heat exchanger’s efficiency could be improved.To establish the most effective elements for heat transfer enhancement,the heat exchangers thermal performance was tested at 0.05%and 0.1%concentrations for Al_(2)O_(3)and CuO nanoparticles.The simulation results showed that the percentage increase in Nusselt number(Nu)for nanofluid at 0.05%particle concentration compared to pure oil was 9.71%for CuO nanofluids and 6.7%for Al_(2)O_(3)nanofluids.At 0.1%concentration,the enhancement percentage in Nu was approximately 23%for CuO and 18.67%for Al_(2)O_(3)nanofluids,respectively.At a concentration of 0.1%,CuO nanofluid increased the LMTD and overall heat transfer coefficient(U)by 7.24 and 5.91%respectively.Both the overall heat transfer coefficient(U)and the heat transfer coefficient(hn)for CuO nanofluid at a concentration of 0.1%increased by 5.91%and 10.68%,respectively.The effectiveness(εn)of a heat exchanger was increased by roughly 4.09%with the use of CuO nanofluid in comparison to Al_(2)O_(3)at a concentration of 0.1%.The amount of exergy destruction in DTHX goes down as Re and volume fractions go up.Moreover,at 0.05%and 0.1%nanoparticle concentrations,the percentage increase in dimensionless exergy is 10.55%and 13.08%,respectively.Finally,adding the CuO and Al_(2)O_(3)nanoparticles improved the thermal conductivity of the main fluid(oil),resulting in a considerable increase in the thermal performance and rate of heat transfer of a heat exchanger.

Endoscopic dacryocystorhinostomy with bicanalicular silicone tube intubation for treating chronic dacryocystitis secondary to nasolacrimal duct stent incarceration

AIM:To investigate the feasibility of endoscopic dacryocystorhinostomy(En-DCR)with bicanalicular silicone tube intubation for treating chronic dacryocystitis secondary to nasolacrimal duct stent(NDS)incarceration.METHODS:En-DCRs were performed on 44 chronic dacryocystitis patients(46 eyes)secondary to NDS incarceration from April 2016 to October 2022.The granuloma and scar tissues were separated,and the removal of NDS incarceration was achieved during the surgery;the flap of the lacrimal sac was trimmed and anastomosed with nasal mucosal,a bicanalicular silicone tube was implanted,and lacrimal size and condition were assessed.The tube was removed 3mo after surgery.During the final follow-up of 12mo when the surgery was completed,the complications and the rates of surgical success were assessed.RESULTS:This study covered 40 patients(42 eyes).Intraoperatively,it was found that the lacrimal sac became small,and the sac wall had granulation and scar tissue attached to the incarcerated NDS in all eyes.At 12mo after surgery completed,the rates of the functional and anatomical success reached 80.95%(34/42)and 83.33%(35/42),respectively.Under the effect of intranasal ostial closure,seven eyes failed to achieve anatomical success.No serious complications(e.g.,visual impairment,sinusitis,and orbital fat prolapse)was observed.CONCLUSION:With the success rate over 80%and no serious complications,En-DCR with bicanalicular silicone tube implantation is effective in treating chronic dacryocystitis secondary to NDS incarceration.

Experimental study on the seismic behavior of high strength concrete fi lled double-tube columns

To study the seismic behavior of high strength concrete fi lled double-tube(CFDT) columns,each consisting of an external square steel tube and an internal circular steel tube,quasi-static tests on eight CFDT column specimens were conducted.The test variables included the width-to-thickness ratio(β1) and the area ratio(β2) of the square steel tube,the wall thickness of the circular steel tube,and the axial force(or the axial force ratio) applied to the CFDT columns.The test results indicate that for CFDT columns with a square steel tube with β1 of 50.1 and 24.5,local buckling of the specimen was found at a drift ratio of 1/150 and 1/50,respectively.The lateral force-displacement hysteretic loops of all specimens were plump and stable.Reducing the width-to-thickness ratio of the square steel tube,increasing its area ratio,or increasing the wall thickness of the internal circular steel tube,led to an increased fl exural strength and deformation capacity of the specimens.Increasing the design value of the axial force ratio from 0.8 to 1.0 may increase the fl exural strength of the specimens,while it may also decrease the ultimate deformation capacity of the specimen with β1 of 50.1.

A staggered double vane circuit for a W-band traveling-wave tube amplifier

Based on the combination of a staggered double vane slow wave structure （SWS） and round electron beam, a 200-W W-band traveling-wave tube （TWT） amplifier is studied in this paper. The main advantages of round beam operation over the sheet beam is that the round beam can be formed more easily and the focus requirement can be dramatically reduced. It operates in the fundamental mode at the first spatial harmonic. The geometric parameters are optimized and a transition structure for the slow wave circuit is designed which can well match the signal that enters into and goes out from the tube. Then a TWT model is established and the particle-in-cell （PIC） simulation results show that the tube can provide over 200-W output power in a frequency range of 88 GHz-103 GHz with a maximum power of 289 W at 95 GHz, on the assumption that the input power is 0.1 W and the beam power is 5.155 kW. The corresponding conversion efficiency and gain at 95 GHz are expected to be 5.6% and 34.6 dB, respectively. Such amplifiers can potentially be used in high power microwave-power-modules （MPM） and for other portable applications.

An advanced turbulator with blades and semi-conical section for heat transfer improvement in a helical double tube heat exchanger

In present work,a helical double tube heat exchanger is proposed in which an advanced turbulator with blades,semi-conical part,and two holes is inserted in inner section.Two geometrical parameters,including angle of turbulator’s blades(θ) and number of turbulator’s blades(N),are considered.Results indicated that firstly,the best thermal stratification is achieved at θ=180°.Furthermore,at the lowest studied mass flow rate(m = 8 × 10^(-3) kg/s),heat transfer coefficient of turbulator with blade angle of 180° is 130.77%,25%,and 36.36% higher than cases including without turbulator,with turbulator with blade angle of θ =240°,and θ =360°,respectively.Moreover,case with N=12 showed the highest overall performance.At the highest studied mass flow rate(m = 5.842 × 10^(-2) kg/s),heat transfer coefficient for case with N=12 is up to 54.76%,27.45%,and 6.56% higher than cases including without turbulator,with turbulator with N=6,and with turbulator with N=9,respectively.

Design of a re-entrant double-staggered ladder circuit for V-band coupled-cavity traveling-wave tubes

The re-entrant double-staggered ladder slow-wave structure is employed in a high-power V-band coupled-cavity traveling-wave tube. This structure has a wide bandwidth, a moderate interaction impedance, and excellent thermal dissipation properties, as well as easy fabrication. A well-matched waveguide coupler is proposed for the structure. Combining the design of attenuators, a full-scale three-dimensional circuit model for the V-band coupled-cavity traveling- wave tube is constructed. The electromagnetic characteristics and the beam wave interaction of this structure are investigated. The beam current is set to be 100 mA, and the cathode voltage is tuned from 16.8 kV to 15.8 kV. The calculation results show that this tube can produce a saturated average output power over 100 W with an instantaneous bandwidth greater than 1.25 GHz in the frequency ranging from 58 GHz to 62 GHz. The corresponding gain and electronic efficiency can reach over 32 dB and 6.5%, respectively.

Surgical outcomes in acute dacryocystitis patients undergoing endonasal endoscopic dacryocystorhinostomy with or without silicone tube intubation

AIM:To establish the necessity of silicone tube intubation in acute dacryocystitis(AD)patients undergoing endonasal endoscopic dacryocystorhinostomy(En-DCR).METHODS:Patients presenting with unilateral AD were randomly assigned to two treatment groups.En-DCR procedures were performed following lacrimal abscess formation,with the operation being performed with silicone intubation for patients in group B but not group A.Functional success was defined by an absence of additional AD episodes,no epiphora,and ostium patency as established via endoscopic evaluation or fluorescein irrigation.Operative success rates and demographic variables were compared between treatment groups.RESULTS:In total,66 patients were analyzed in the present study(33 per group),with complete postoperative data having been successfully collected from 27 and 22 patients in group A and group B,respectively.All patients exhibited complete resolution of acute inflammation.Upon follow-up,granulation tissue was detected around the ostium at higher rates in group B(9/22,40.9%)relative to group A(4/27,14.8%).At the 12-month follow-up time point,patients in group A exhibited higher success rates(25/27,92.6%)relative to patients in group B(20/22,90.9%),but this difference was not significant.Cases of lacrimal passage reconstruction failure in both groups were attributed to excessive fibrous and/or granulation tissue formation proximal to the intranasal ostium.CONCLUSION:Given that these two operative approaches are associated with similar rates of operative success and in light of differences in granulation tissue formation,cost,and operative duration,these data do not support the routine silicone intubation of AD patients following En-DCR surgery.

Effect of cyclotron resonance on ‘hot’ dispersion in a staggered double metallic grating sheet beam travelling wave tube

Based on the beam wave synchronous interaction in transverse and longitudinal directions at the same time and starting from Maxwell’s equation and linear Vlasov equation, the beam–wave interaction ‘hot’ dispersion equation considering both cyclotron resonance and Cherenkov resonance in a staggered double metallic grating traveling wave tube is deduced.Through the reasonable selection for geometric and electrical parameters, the numerical calculation and analysis of the ‘hot’ dispersion equation shows that the beam–wave interaction gain and frequency band with the cyclotron resonance enhancement effect are higher than those with only Cherenkov resonance radiation.

Effect of Empowering Education on Refined Nursing of Patients with Internal Double J Tubes after Surgery for Ureteral Stricture

Objective: To investigate the effect of the theory of enabling education on the fine management of patients with internal double J tubes after ureteral stricture. Methods: Eighty patients with built-in double J tubes after ureteral stricture were selected from the urology department of a grade a hospital in Guangzhou. The patients were divided into control group and observation group by random number method, with 40 patients in each group. The control group received refined nursing after surgery, while the observation group received refined nursing including the theory of empowerment education after surgery on the basis of the control group. Results: After the intervention, the observation group had a higher standard rate of quality indicators, higher self-efficacy score than the control group (P ≤ 0.05), lower scores of ureteral stent-related symptoms, urinary system symptoms, pain symptoms, total health status, job performance, additional problems and total scores than the control group (P ≤ 0.05), and statistically significant differences were found in the total health status dimension and total scores (P ≤ 0.01). The nursing satisfaction survey, the scores of clinical nursing, health education, psychological counseling and nurse-patient communication were all higher than those in the control group (P ≤ 0.05), and the differences in health education and nurse-patient communication were statistically significant (P ≤ 0.01). Conclusion: The theory of enabling education can improve patients’ self-nursing level, promote the implementation of refined nursing quantitative indicators and nursing measures, relieve the poor symptoms of ureteral stricture patients, and improve patients’ satisfaction with nursing work.

Remote Control System of 37 mm Double Tube Antiaircraft Gun for Hunan Weather Modification

Hunan Weather Modification Center and Suizhou Dafang Precision Electromechanical Engineering Co.,Ltd. of Hubei commonly transformed and installed 83 double tube antiaircraft guns( 37 mm) of Hunan Province in order to realize remote control of computer. After transformation,loading capacity of ammunition feeding machine became large,which could shorten the time of filling shells in the case of short airspace time;one shell launch volume was more,which could improve hail suppression effect; the degree of automation was greatly improved,which could save manpower by more than 50%. It fully embodied the modernization level of Hunan weather modification operation.

Techno-economic analysis of single U-tube and double U-tube heat exchangers in Chongqing area

On the basis of practical projects in Chongqing,the thermal performance of heat exchangers (single U-tube type and double U-tube type) of the ground-source heat pump (GSHP) system in the hot summer was obtained and analyzed. The data obtained from test could match with the result deduced from theoretical calculation. From the test results,the cooling capacity of double U-tube is 1.6 times that of single U-tube. Taking cost per depth per watt Clq as the evaluation standard,Clq of single U-tube is 4.69 RMB$/W,and Clq of double U-tube is 3.14 RMB$/W. The double U-tube heat exchangers usage should be prioritized.

Fascial pedicle artificial nerve tissue compared with silicone tube bridging to repair sciatic nerve defects in rats

BACKGROUND： Silicone tube bridging for peripheral nerve defects has been shown to be successful in guiding neural regeneration. However, this method is accompanied by complications. Because materials for bridging nerve fibers should exhibit biocompatibility, the development of novel artificial tissues to bridge nerve grafts has become important in the field of nerve tissue engineering for the repair of peripheral nerve defects. OBJECTIVE： To investigate effectiveness and feasibility of fascial pedicle artificial nerve tissue to repair peripheral nerve defects, and to compare to autologous nerve grafts and silicone tube bridging methods. DESIGN, TIME AND SETTING： Randomized, controlled, neural tissue engineering-based, animal experiments were performed at the Laboratory of Human Anatomy in Qingdao University Medical College from March 2006 to March 2007. MATERIALS： Medical absorbable collagen sponge was purchased from Henan Province Tiangong BJo-Material, China. Cantata 2-track 4-trace EMG-evoked potential instrument was purchased from Dantec, Denmark. Medical silicone tube was purchased from Shenzhen Legend Technology, China. METHODS： Forty healthy, adult, male, Sprague Dawley rats were randomly assigned to four groups fascial pedicle nerve, autologous nerve, silicone tube, and normal, with 10 rats in each group. A 10-mm defective sciatic nerve section was produced in rats following the removal of the fascial pedicle. The fascial flap surrounding the defect was harvested; one side of the nerve pedicle was maintained and then sutured into a tube with the fascia surface as the pipe inner wail. The tube was filled with a medical absorbable collagen （Bodyin） to construct a bridge between the artificial tissue nerve graft and the damaged sciatic nerve. The sciatic nerve defects in the autologous nerve and silicone tube groups were bridged using autologous nerve grafts and a medical silicone tube with matched specifications. MAIN OUTCOME MEASURES： At 4 months after transplantation, electromyogram was used to detect sciatic nerve conduction velocity and action potential amplitude. Hematoxylin-eosin and Nissl staining were used to determine the number of spinal cord anterior horn motor neurons and neurites Osmium tetroxide staining of the sciatic nerve bridge section was performed to detect the number and diameter of nerve fibers. RESULTS： There were no differences in sciatic nerve conduction velocity, action potential amplitude, the number of spinal cord anterior horn motor neurons and neurites, sciatic nerve fiber number, and diameter between the autologous nerve graft and normal groups （P 〉 0.05）. However, these values were significantly greater than in the silicone tube group （P 〈 0.05）. CONCLUSION： Quantitative results suggested that artificial nerve tissue, with an autologous tissue fascia flap as a nerve conduit, could be used to repair peripheral nerve defects. The regenerated fascial pedicle artificial nerve tissue was similar to an autologous nerve graft in terms of morphology and functional recovery and was superior to results from silicone tube bridging transplants.

Numerical simulation on thixo-co-extrusion of double-layer tube with A356/AZ91D

Based on analysis of the main forming methods for double-layer tube,a new short-term forming process called thixo-co-extrusion was put forward in producing double-layer tube by combining the semi-solid forming technology and multi-billet extrusion technology.By means of forward extrusion with shaft,a finite element model of thixo-co-extrusion with A356/AZ91 was constructed by ABAQUS FEM software.The distributions of temperature field and velocity field as well as the contact force during thixo-co-extrusion were studied.The diffusion on the interfaces between inner and outer metals was analyzed.The simulation results show that,in the beginning of thixo-co-extrusion,the uneven wall thickness can appear.To thickness ratio of 5:5,a double layer tube with good inner and outer wall combination can be realized if VA356 is 0.12 m/s and VAZ91 is 0.20 m/s.

Virtues of Using a Double Lumen Tube for Anesthesia in Patients with Endobronchial Tumours Requiring Open Lung Resection or Bronchoplastic Procedures

Objective The benefits and risks of using double lumen tube (DLT) in open thoracotomy are not well studied and the relative contraindication for using it in cases of endobronchial tumours is not proven. In this study, we compared our experience with using DLT versus single lumen tube (SLT) for anesthesia in patients requiring an open thoracotomy for resection of endobronchial tumours. Methods A prospective observational study was performed in a single tertiary care university hospital in patients with endobronchial tumours anesthetized with single and double lumen tubes for open thoracotomy procedures over a period from 2010 till 2018. Results One hundred and six patients with endobronchial tumours were studied. There were 76 males. Median age was 32 years (14 - 62). In 96 cases, endobronchial pathology was a typical carcinoid. 58 patients were anesthetized using a DLT and 48 using a SLT. Four cases of near miss from potentially fatal intraoperative tumour migration occurred in the SLT group (p = 0.025). There was only one case of mild tumour bleeding from the DLT group and time of insertion was longer (16.2 vs. 4.5 min p Conclusions We conclude that it is safe to place a double lumen endo tracheal tube for patients with endobronchial tumours requiring open lobectomies or bronchoplastic procedures. An additional benefit of DLT use is increasing surgical satisfaction by reducing spillage and tidal volume loss during surgical anastomosis of the open airway.

Simulation Analysis of Flow Characteristics in the Vortex Diode with Double Tangential Tube

The paper analyzed flow characteristics in vortex diode with double tangential tube by numerical simulation. Compared to traditional vortex diode with one tangential tube, the structure of double tangential tube can reduce the forward resistance and improve overall performance. The symmetrical design adopted in vortex diode with double tangential tube;the internal flow field in chamber showed symmetrical distribution in the reverse flow, which can improve the flow stability and accelerate the convergence speed in simulation.

Wind Tunnel Validation of Double Multiple Streamtube Model for Vertical Axis Wind Turbine

The performance and annual energy output have to be predicted to maximize the economic benefits from a wind turbine. Mathematically predicting the performance of Darrieus type lift based turbines are challenging due to the inconsistent angle of attack, blade wake interaction and local induced velocities giving rise to complex flow physics. A reliable and validated mathematical model is therefore essential to optimize the various design parameters prior to manufacture. The objective of the current study is to evaluate widely employed aerodynamic models based on their prediction accuracy, limitations, and computational requirements. Double multiple stream tube models have been discussed in detail and the predictions are experimentally validated through the wind tunnel test of three-bladed H-Darrieus rotor in terms of torque and power coefficient. The possible sources for the deviation between the predicted and measured values have been discussed and concluded with potential solutions.

Use of Silicone Tubes to Repair Canalicular Lacerations via a Novel Method

Purpose:To develop a novel method to repair canalicular lacerations using silicone tubes.Methods:A total of 47 adult patients(47 eyes)with canalicular lacerations were collected from the outpatient department from November 2010 to December 2012.The age ranged from16 to 53 years.Among the 47 eyes,37 had lower canalicular lacerations,6 had upper canalicular lacerations,and 4 had bicanalicular lacerations..A soft probe was made using a stainless steel acupuncture needle,which was inserted into the lumen of the proximal part of the catheter to increase its rigidity.The probe was then inserted into the lacrimal sac and nasolacrimal duct.After retrieval of the catheters,the two ends of the silicone tube were securely tied.(end to end).to the catheters..The silicon tube outside the nostril formed a Ushape.The catheters were then pulled upward until the silicone tube was completely located in the canalicular system.The catheters were cut off of the silicone tube near the site of the connection.The two ends of the silicone tube were cut short,~2mm out of the lacrimal punctum,and tied securely,end to end.The length of the tube between the upper and lower punctum was adjusted to ensure that no tension was present in the medial cathus,and the suture was removed through the nostril.The silicone tube was removed 3-10 months after this novel canalicular intubation procedure (NCI).Results:.All cases were anatomically rehabilitated after surgery..The silicone tube was removed after implanted in 3-10months (mean 4.5±1.3 months),the average follow-up time was 11.8 months after removal.In total,45 eyes in all 47eyes (95.74%)were free from obstruction.Among them,41eyes (91.11%) achieved complete success(completely disap-pearance of epiphora after tube removal),.4 eyes.(8.89%)achieved partial success.(irritation occurs under stimulation conditions,such as wind or cold conditions),4 eyes showed postoperative tearing,with three eyes having inferior lacrimal duct laceration,and one eye with superior canalicular laceration.Apart from two cases (4.26%) suffering inferior punctum splitting,no other associated issues occurred with the silicone tube or iatrogenic injury and lacrimal complications.Conclusion:For adult patients with canalicular laceration,the NCI was an effective,atraumatic surgery,which has fewer complications than traditional canalicular suture.

Repositioning of the complete prolapsed silicone tube with modified suture-probe and silk thread traction method

The whole lacrimal passage intubation is widely used in lacrimal surgery.However,one of the most typical complications is the prolapse of the silicone tube from the medial canthus.In case,the bicanalicular silicone tube after whole lacrimal duct intubation has completely prolapsed from the medial canthus before extubation,then cannot be found in the opening of the nasolacrimal duct,and it would be a challenge to reposition or removal.A novel approach to employ a modified suture-probe and silk thread traction technique has been developed,and it is not only safe and effective,but also cost-effective.

Double aortic arch and nasogastric tubes: A fatal combination

Double aortic arch is a common form of complete vascular ring that encircles both the trachea and the esophagus, and presents with various respiratory and esophageal symptoms, usually in the pediatric population. We present a case of double aortic arch in an adult patient that manifested as massive upper gastrointestinal bleeding after prolonged nasogastric intubation.

Structure and Electrochemical Performance of Hollow Tube Activated Carbon Prepared from Cotton as Electrode Material for Electric Double Layer Capacitor

Hollow tube-like activated carbon（HTAC） was fabricated by a simple and efficient carbonization method with cotton as carbon precursor activated by KOH without any template. The activation time from 0 to 90 min showed no significant effect on the micro-morphology, but greatly influenced the specific surface area and electro- chemical performance. In the end, it was found that the sample activated for 60 min（HTAC-60） has a higher specific surface area of 2600 m2/g, a larger pore volume of 1.52 cm3/g and a greater specific capacitance of 483 F/g at a current density of 0.2 A/g in 1 mol/L H2SO4. Moreover, the sample HTAC-60 shows excellent cycle stability（only 12.2% loss after 5000 cycles） and a high energy density of 67.1 or 37.2 W-h.kg-1 at a power density of 200 or 1000 W/kg, respectively, operated in a voltage range of 0--1.0 V in 1 mol/L H2SO4. The results indicate that cotton can potentially be used as a raw material for producing low cost and high performance activated carbon electrode materials for electric double layer capacitor.