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Based on the theory of elastic fracture and using direct modeling method, a numerical model was developed for solving the composite stress intensity factor of semi-elliptical cracks on exchanger outer walls with inclined angles. The model exchanger had an outer diameter of φ50 mm, inner diameter of φ44 mm and length of 300 mm. The values of crack plane inclination β (0°, 10°, 20°, 30°, 40° and 45°), crack depth a (0.5 mm, 0.75 mm, 1 mm and 1.25 mm), and crack shape ratio a/b (0.4, 0.5, 0.55, 0.6, 0.7, 0.8, 0.9 and 1.0) were obtained and 3D surface crack model was established. The results were significance for the evaluation of the remaining life of exchanger components.

Standard flexible bronchoscopes may enter up to third- to fifth-generation bronchi and allow visualization of one to two further generations in adult patient airways, while the category of “ultrathin bronchoscope” can reach small peripheral airways up to 9th to 12th generation. Although no formal definition of “ultrathin bronchoscope” has been established, the term ultrathin has been widely used when referring to bronchoscopes with an outer diameter of 3 mm or less that are used for the exploration of peripheral airways in adult patients. In Fig. 3.1 you can compare the size of different bronchoscopes.

Purpose The use of self-tapping cortical screws is indicated in patients with metacarpal and phalangeal fractures requiring formal stabilization. The aim of this study was to systematically compare and evaluate the design parameters of 4 commercially available self-tapping screw systems. Methods We measured various design parameters of self-tapping cortical screws of different lengths from several manufactures using scanning electron microscopy. Screws were obtained in 8, 12, 16, and 20 mm lengths. The measured parameters included screw length, head height, pitch, outer diameter, inner diameter, terminal thread diameter, terminal thread-to-tip distance, thread-to-tip distance of 1 full revolution, and crest width. Data were assessed statistically using 1- and 2-way analysis of variance (ANOVA) tests, and the significance level was set at a P value Results There was variability in advertised screw lengths compared with measured screw lengths with 2 manufacturers. There was a statistically significant difference between the thread-to-tip distance and head height between screws while controlling for diameter. Conclusions Screw sizes and dimensions are critical in order to avoid complications such as prominent hardware and postoperative stiffness. Knowledge of the design parameters presented for each of the different manufacturers may prove useful to hand surgeons when selecting screws for fixation of metacarpal and phalangeal fractures. Clinical relevance Specific design characteristics of commonly used screws in hand surgery vary slightly by manufacturer and may have clinically relevant implications in fixation of metacarpal and phalangeal fractures.

This study reports on the effects of insertion velocity, needle tip geometry and needle diameter on tissue deformation and maximum insertion force. Moreover, the effect of multiple insertions with the same needle on the maximum insertion force is reported. The tissue deformation and maximum insertion force strongly depend on the insertion velocity and the tip geometry. No correlation was found between the outer diameter and the maximum insertion force for small needles (30G – 32G). The endurance experiments showed no remarkable difference in the maximum insertion force during 100 insertions.

In pediatric arteriography, vascular complications are more common than in adults; thus, the use of the smallest catheter to accomplish the objective of the procedure is recommended. We describe two pediatric cases in which abdominal arterial embolization and arteriography were performed with steerable microcatheters without conventional diagnostic catheters. Additionally, we used an introducer with an outer diameter of 4-F in a Mini Access Kit (Merit Medical, South Jordan, UT) as a vascular sheath to reduce sheath size. We believe that this technique may be feasible and safe for abdominal arterial interventions in children.

For cooling or heating coils of a building air conditioning system, large diameter tubes (over 12.7 mm) are frequently used. Furthermore, common enhanced geometries of the coils are wave fins. In this study, heat transfer and pressure data were obtained from samples having smooth wave or herringbone wave fins. The samples had a range of tube row (one to four) and three different fin pitches. Especially, the tube diameter of the samples was rather large (12.7 mm). Result showed that the highest j factor was obtained at a one row configuration. However, the thermal conductance (= ηohoAo) showed a different trend to that of the j factor. At a low velocity, the thermal conductance of the one row sample was the highest. At higher velocity, however, the trend was reversed. The reason was explained by introducing the fin efficiency. The j and f factors of the smooth wave fin samples were higher (0 % to 31 % for the j factor and 11 % to 25 % for the f factor) than those of the herringbone wave fin samples. The present data were compared existing correlations.

This work aims at understanding and eliminating thermo-mechanically induced circumferential cracks that form during cooling for a 400 °C annealed copper (Cu) through-glass via (TGV) with a mean outer diameter of $47.5~\mu \text{m}$ , made in Corning HPFS fused silica glass. An exponential dependence was found between Cu metallization thickness and the likelihood for the formation of circumferential cracks. For the conditions used in this study, no cracks were formed in the HPFS fused silica substrate for Cu metallization thicknesses $ \mathbf { , however, for thicknesses $ \mathbf {\mathrm {\ge }}~12~\mu \text{m}$ , circumferential crack formation exponentially increased. From finite element analysis (FEA) studies, the corresponding threshold stresses for the initiation of circumferential stresses at $12~\mu \text{m}$ was predicted to be 140 MPa. Therefore, for 400 °C annealed Cu TGV with a mean outer diameter of $47.5~\mu \text{m}$ , made in HPFS fused silica substrate, circumferential stresses can be eliminated when Cu metallization thickness of less than $12~\mu \text{m}$ is used.

Raker piles are used more often in combination with vertical piles in a group where the lateral load per pile overshoots the value suitable for vertical piles. Under lateral loads, the behaviour of such group is generally different from that of a vertical pile group due to interaction of raker piles, resulting in the increase of the pile group capacity. A series of laboratory experiments have been carried out with Aluminium pipe pile of outer diameter 25.4 mm and thickness 1 mm in which the soil medium is of clean river sand. The lateral load tests were conducted in driven vertical and vertical–raker pile group configurations (two, three and four) in which raker piles were inclined at angle of 15o from vertical in different soil conditions namely loose sand (relative density, Dr = 30%), medium dense sand (Dr = 45%), dense sand (Dr = 70%). Based on these tests, the group efficiency for different soil conditions and the maximum bending moment were arrived. Based on the experimental results, a non-dimensional design chart has been developed for single pile, vertical and raker pile groups. This study establishes that the effectiveness of lateral load capacity of pile groups increases rapidly up to 50% of relative density of sand beyond which the increase was very minimal. The front raker pile group was efficient to carry lateral load because it resists more lateral load and bending moment than vertical and rear raker pile group configurations. The results demonstrate that the maximum bending moment occurs at a depth of 8D–10D (D—diameter of the pile) for all vertical pile group configurations and 10D–11D for raker pile group configurations.

In this experimental study, permanent magnets with three different sizes (M-1: 32 mm inner diameter, 70 mm outer diameter and 15 mm thick, M-2: 25 mm inner diameter, 60 mm outer diameter and 10 mm thick, M-3: 22 mm inner diameter, 45 mm outer diameter and 9 mm thick) are fully submerged in the single-slope glass solar still. The performance of magnetic solar stills (MSS) with three different sizes at 2 cm depth water to ensure that magnets are fully submerged is compared with conventional solar still (CSS) at the location 17.3850°N, 78.4867°E. Tiwari model is adapted to calculate the heat transfer coefficients (HTC), internal and exergy efficiencies. MSS with M-1, M-2 and M-3 significantly enhanced the convective, radiative, and evaporative heat transfer rate for the 2 cm depth of water. This is due to the desired magnetic treatment of water, which reduces the surface tension and increases the hydrogen bonds. The MSS's total internal HTC, instantaneous efficiencies led CSS by 25.52%, 28.8%, respectively, with M-1. Having various magnetic fields due to different magnets sizes increases MSS's exergetic efficiency by 33.61% with M-1, 33.76% with M-2, and 42.25% with M-3. Cumulative yield output for MSS with M-1, M-2, and M-3 is 21.66%, 17.64%, 15.78% higher than CSS. The use of permanent magnets of different sizes in the MSS is a viable, economical and straight forward technique to enhance productivity.

Scaling-up of a 5 kg LaNi5 reactor i.e. Reference Design (RD) with 88.9 mm outer diameter (OD) and 10 conical copper fins embedded with 6 cooling tubes to a 25 kg one is studied through simulations. RD takes 585 s for 90% saturation during hydrogen absorption at Ps = 15 bar and 5 LPM water supply (20 °C). Decreasing tank OD and increasing the number of fins result in the best performance. A scaled-up design with tank OD = 114.3 mm and 60 fins exhibits 57–58% reduction in saturation time (695 s), versus a proportionally-scaled-up design (dimensions of RD increase proportionally) with tank OD = 141.3 mm and 10 fins. Five units of RD connected in series reduce saturation time by ~60% (670 s). Series/parallel configurations can match the RD performance, reduce shutdown risk, offer flexibility in operation, configuration and ease of maintenance.

Central airway obstruction (CAO) can be attributed to several benign or malignant conditions. Although surgery is the preferred therapeutic option for the management of CAO, bronchoscopic treatment can be performed in scenarios where the surgical procedure is not possible. Recent years have witnessed several improvements in the field of bronchoscopic treatment, especially with regard to airway stents. Current research involves new attempts to overcome the existing shortcomings pertaining to the stents (migration, mucostasis, and granulation tissue formation). The authors have recently developed a new silicone airway stent (GINA stent) with an anti-migration design, dynamic structure that enables the reduction of stent cross-sectional area, and radio-opacity. The present study aimed to evaluate the mechanical characteristics and performance of the novel GINA stent using a porcine tracheal stenosis model. In the current study, all the tests involved the comparison of the GINA stent [outer diameter (OD, mm): 14; length (L, mm): 55] with the Dumon stent (OD: 14; L: 50). The mechanical tests were performed using a digital force gauge, in order to determine the anti-migration force, expansion force, and flexibility. The present study evaluated the short-term (3 weeks) performance of the two stents after implantation [GINA (n = 4) vs. Dumon (n = 3)] in the porcine tracheal stenosis model. The results pertaining to the comparison of the mechanical properties of the GINA and Dumon stents are stated as follows: anti-migration force (18.4 vs. 12.8 N, P = 0.008); expansion force (11.9 vs. 14.5 N, P = 0.008); and flexibility (3.1 vs. 4.5 N, P = 0.008). The results pertaining to the comparison of the short-term performance of the GINA and Dumon stents are stated as follows: mucus retention (0/4 vs. 0/3); granulation tissue formation (0/4 vs. 0/3); and migration (1/4 vs. 2/3). The GINA stent displayed better mechanical properties and comparable short-term performance, compared to the Dumon stent.

Long-acting antiretroviral implants could help protect high-risk individuals from HIV infection. We describe the design and testing of a long-acting reservoir subcutaneous implant capable of releasing cabotegravir for several months. We compressed cabotegravir and excipients into cylindrical pellets and heat-sealed them in tubing composed of hydrophilic poly(ether-urethane) -. The implants have a 47 mm lumen length, 3.6 mm outer diameter, and 200 μm wall thickness. Four cabotegravir pellets were sealed in the membrane, with a total drug loading of 274 ± 3 mg. In vivo, the implants released 348 ± 107 μg/day (median value per implant, N = 41) of cabotegravir in rhesus macaques. Five implants generated an average cabotegravir plasma concentration of 373 ng/ml in rhesus macaques. The non-human primates tolerated the implant without gross pathology or microscopic signs of histopathology compared to placebo implants. Cabotegravir plasma levels in macaques dropped below detectable levels within two weeks after the removal of the implants.

The boiling heat-transfer performances of R1234ze(E)/R152a (0.4/0.6 by mass) flowing inside a horizontal micro-fin tube of 9.52 mm outer diameter were researched by experiment. Under the experiment...

High-flux fine hollow fiber nanofiltration (HFNF) membranes were prepared by interfacial polymerization (IP) using polysulfone (PSF) ultrafiltration (UF) membranes with an outer diameter of 425 μm ...

A micro-machined tip-separable microneedle structure fabricated using a molding process was placed on the end of a metal rod with the outer diameter of 2.0 mm to produce a spear-shaped microneedle, and an applicator for inserting this microneedle into the skin based on a commercially available stamp mechanism was developed. The fabricated spear-shaped microneedle with the needle holder was inserted into the stamp mechanism and a load cell was embedded between the push button and the microneedle for quantitatively evaluating the applied force during microneedle insertion. A PDMS sheet with the Young’s modulus of 0.8 MPa, similar to that of human skin, was used as the artificial skin sample. The tip part was separated from the base and successfully embedded into the skin when the relatively large force of 64.9 N was applied within the time period of 426 ms. The tip was completely embedded to the depth of 0.305 mm below the skin surface, and thus the puncture marks generated by the insertion were almost completely closed thanks to the elasticity of the PDMS at the surface.

It is known that hydrogen embrittlement could result in warping and destruction of pure Pd membranes, which limits the working temperatures to be above 293 °C. This study attempted to investigate the relationship between hydrogen embrittlement resistance and membrane geometry of ultrathin pure Pd membranes of 2.7–6.3 μm thickness. Thin tubular Pd membranes with an o.d. of 4 mm, 6 mm and 12 mm immediately suffered from structural destruction when exposed to H2 at room temperature. In contrast, thin hollow fiber membranes (outer diameter, 2 mm, thickness < 4 μm) exhibit strong resistance against hydrogen embrittlement at temperatures below 100 °C during repeated heating/cooling cycles at a rate up to 10 °C min−1 under H2 atmosphere. This is ascribed to reduced lattice strain gradients during α–β phase transition in cylindrical structures and lower residual stresses according to in situ XRD analysis, which shows a great prospect in low temperature applications.

This paper presents both experimental and analytical investigation to monitor the effect of dynamic pile-soil-pile interaction on the nonlinear coupled response of a 6-pile group placing in different arrangements of piles under rotating machine induced vibrations. Another aspect of the present study is the theoretical prediction of parameters responsible for the nonlinear coupled response of the pile foundation. The pile groups comprised of hollow steel piles with an outer diameter of 0.114 m and a length of 3 m. Coupled vibration field tests are performed on the pile groups laid in two different set of pile arrangements (2 $$\times$$ 3 and 3 $$\times$$ 2 pile groups) to obtain the dynamic horizontal and rocking responses of the pile groups under different eccentric moments. For theoretical study, the continuum approach with superposition method is used to determine the nonlinear dynamic responses of the pile groups. The analytical frequency-amplitude responses for both types of vibrating displacements are compared with the dynamic field test results and the variations of the influencing parameters for the nonlinear dynamic response of the soil-pile system are predicted for coupled vibration. For 3 × 2 pile group, the resonant frequencies are found lower and resonant amplitudes are found higher than the values of the 2 × 3 pile group for all eccentric moments. It is also observed that the stiffness and damping of the 3 × 2 pile group shows lesser values than the 2 × 3 pile group even if the input analytical parameters are same for both the pile groups. From the results, it can be concluded that the effect of dynamic pile-soil-pile interaction is more pronounced for 3 × 2 pile group as compared to the 2 × 3 pile group.

The condensation heat transfer characteristics of a new environmental refrigerant mixture R1234ze (E)/R152a (mass ratio 40:60, named NCUR01) in a horizontal micro-fin tube with an outer diameter of...

Background The follicular unit excision (FUE) technique has become the preferred method for hair transplants over the traditional strip harvest technique due to low scar visibility and shorter recovery time for the patient. However, a limitation of the FUE technique is the potential for graft trauma due to the small diameter, sharp punches used to harvest individual follicular units. Aims Here, we introduce the novel edge out FUE punch that is designed with a thicker wall and has an internal bevel. We describe how the dynamics of this punch reduces the risk of follicle transection. Methods A review of the available literature and information on the edge out punch in comparison with other punch shapes, as well as the authors' experience in this area, is provided. Results The edge out punch is designed with thick walls and an internal bevel, placing the sharp cutting edge on the outer diameter. The dynamics of this punch aid in directing the graft into the center of the punch lumen and keeps the sharp cutting edge away from the hair follicles deeper in the dermis, reducing the risk of follicle transection. Conclusion The dynamics of the forces generated by the edge out punch aid in minimizing follicular transections during graft harvesting. By understanding the dynamics behind this novel punch, hair restoration surgeons (HRSs) can optimize their surgical technique to obtain consistently high-quality grafts during FUE.

Some aspects of the life cycle extension of RC tower which is a chemical enterprise was described. This technological tower of ammonium seliters granulation has a height of +71,30 m. From this height to the Mark +46,10 mthe tower is made in a metal frame with diameter at the axes of the column22,56 m. The façade of this part is made of mounted keramzytoconcrete panels and in line constructional glazing. Between the marks 0,00 ÷ +46,10 mthe building has a monolithic RC trunk, which has a cylindrical outline in the form of a shell with an outer diameter of12,88 mand a thickness of0,3 mwalls.During 46 years of operation in chemical influences, the surface layers of the tower’s concrete trunk significantly lost its design strength.According to the results of almost regular surveys, the category of RC trunk technical condition was consistently classified as unsuitable for normal maintenance. A significant deterioration of the technical condition came in 2017, after which the building was withdrawn from the technological process, which gave impulse to the searching process of technical solution for the strengthening and chemical protection of the tower to prolong the life cycle of the entire facility.As a result of the survey the construction of the tower shall strengthening by a system of radial and vertical stiffening ribs was developed. It required a substantial unloading of the entire tower.Swiss concern Sika, one of the world leaders in the field of development and implementation of innovative technologies and materials for construction and industry, successfully implements its developments in Ukraine. For the above-described construction the firm Sika offered repair and chemical protection systems against aggressive influences for the internal and external surfaces of the tower shell, which will allow to significantly protect it and prolong the life cycle of structure., У роботі розглянуті деякі аспекти родовження життєвого циклу баштової промислової споруди на хімічному підприємстві. Ця технологічна башта гранулювання аміачної селітри має висоту +71,30 м. З цієї висоти до відмітки +46,10 мбашта виконана у металевому каркасі з ді­аметром за осями колон22,56 м. Фасад цієї частини виконаний з навісних керамзитобетонних панелей та стрічковим заскленням. Між відмітками ±0,00÷+46,10 мспоруда має монолітний залізобетонний стовбур, який має циліндричний обрис у вигляді оболонки з зовнішнім діаметром12,88 мта товщиною стінки0,3 м.За час 46-ти річної експлуатації в умовах хімічних впливів, поверхневі шари бетону стовбура башти суттєво втратили свою проектну міцність. За результатами практично регулярних обстежень, категорія технічного стану залізобетонного стовбура стабіль­но класифікували як непридатну до нормальної експлуатації. Значне погіршення технічного стану наступило у 2017 році, після чого споруда була виведена з технологічного процесу, що дало поштовх процесу пошуку конструктивних рішень для капітального ремонту з підсиленням та хімзахисту стовбура башти для продовження життєвого циклу всієї споруди.За результатами обстеження була запропонована конструкція посилення стовбура башти системою радіальних та вертикальних ребер жорсткості, що потребувало суттєвого розвантаженя всієї баштиШвейцарський Концерн Sika, який є одним із світових лідерів у галузі розроблення та впровадження інноваційних технологій та матеріалів для будівництва і промисловості, з успіхом реалізує свої напрацювання в Україні.Для розглянутої споруди фірма Sika запропонувала системи ремонтів та хімзахисту від агресивних впливів внутрішньої та зовнішньої поверхонь залізобетонного стовбура башти, що дасть можливість суттєво захистити його та продовжити життєвий цикл споруди.

The Central Solenoid (CS) is a key element of the ITER Magnet system, including six identical coils, called modules, assembled together to form a 4 m outer diameter, 13 m high solenoid. It is a superconducting magnet, using a 45 kA Nb3Sn conductor internally cooled by circulation of supercritical helium at 4.5 K with a peak field up to 13 T. It is enclosed inside a structure providing vertical pre-compression and mechanical support. Procurement of the components and the special assembly tooling of the ITER CS is the responsibility of US ITER, the ITER Domestic Agency of the USA, while the ITER Organization (IO) will carry out the assembly of these components. US ITER has awarded several contracts since 2011 to supply seven modules, including a spare, structure components, and the special tooling required for the CS pre-assembly. All deliveries are scheduled with the objective to start the CS assembly at IO site early 2021. IO is now actively preparing this new phase. This paper describes the general CS pre-assembly activities from modules stacking to the pre-compression at 210 MN. The special assembly processes and related tooling are detailed. A focus is given on the module lifting operation, the extensions assembly and the pre-compression. For these last two processes, IO has investigated alternative assembly options that will be presented.

The non-interference uniform speed rope drilling coring device is a tool for investigating samples of submarine underground leakage hydrate rock formations. In the process of coring, the penetration resistance of the shoe is large, and the rock stratum is disturbed, which results in disturbance of the rock sample's original state. In order to solve this problem, the standard core diameter is ∅72 mm and the length is the length of a single cylinder. For example, a drilling coring device with a working outer diameter d not more than 90 mm is used to optimize the size and structure of the shoe. To ensure the strength of the tube shoe, the related dimensions of the shoe were optimized using finite element analysis software, and the structure of the shoe was improved based on the optimized dimensions. The results of the size optimization are: a = 20 °, 11 = 13mm, and a = 1.5mm: the structural improvement results are: the front cone surface at the lower end of the rube shoe is changed to a regular mesa, and the number of regular mesa sides is 32. The LS-DYNA dynamic simulation results show that the penetration resistance of the tube shoe after size optimization and structure improvement is significantly reduced, so the disturbance of the drilling and coring device to the rock formation is also reduced, and the quality of the sample is improved.

The liquid emitting from capillary subjected to a high electric voltage could be dispersed in different ways depending on applied potential and flow rate. The electro-spraying of deionized water was experimentally studied adopting the high-speed camera under different operating parameters. The time resolved images and evolution of drop or/and jet initiation, pulsation, deformation, and separation from capillary tip or meniscus were captured and analyzed. The known electro-spraying modes were identified according to the geometrical forms of meniscus, jet, or/and drop. A spherical droplet with diameter larger than the outer diameter of capillary could be generated in dripping mode at low potential, while a spherical droplet with diameter smaller than outer diameter of capillary could be observed in micro-dripping mode with relative high potential. Spindle-like droplet could be found in spindle mode and usually further disperse into a few of drops with different size for larger flow rate. In the range of applied potential and flow rate, oscillating jet and simple jet could be found, where a long jet could be elongated by electric stresses and further break up into finer drops with highly charged drops. In addition, the operating parameters and drop sizes for different modes are also discussed. Meanwhile, the spraying modes with double capillaries were also observed and discussed.

OBJECTIVE To compare the outer diameter (OD) of conventional and radial sheaths from different manufacturers for sizes typically used in infant catheterization. BACKGROUND The smallest sheath size is recommended to minimize risk of arterial injury in infants. However, sheath size refers to its internal diameter (ID), but it is the larger OD that determines risk. The OD varies between manufacturers and is frequently not known to the end user. METHODS Three authors measured the OD of 3, 3.3, 4, 5, and 6 French (Fr) sheaths from different manufacturers using a Mitutoyo digital micrometer. Continuous variables are reported as mean ± SD. The midshaft and proximal-shaft sheath measurements were compared using an independent samples t test. Agreement between author measurements was tested using intra- and inter-rater reliability analysis. Manufacturer sheath OD measurements were obtained. Statistical significance was set at p

OBJECTIVE To determine the effects of 2 augmentation techniques on the mechanical properties of titanium cannulated bone screws. SAMPLE 33 titanium cannulated bone screws (outer diameter, 6.5 mm; guide channel diameter, 3.6 mm). PROCEDURES 11 screws were allocated to each of 3 groups. The guide channel of each screw was filled with polymethyl methacrylate bone cement alone (OCS group) or in combination with a 3.2-mm-diameter orthopedic pin (PCS group) or remained unmodified (control group) before mechanical testing. Each screw underwent a single-cycle 3-point bending test to failure with a monotonic loading rate of 2.5 mm/min. Failure was defined as an acute decrease in resistance to load of ≥ 20% or a bending deformation of 15 mm. Mechanical properties were determined for each screw and compared among the 3 groups. RESULTS All screws in the control and OCS groups and 1 screw in the PCS group broke during testing; a 15-mm bending deformation was achieved for the remaining 10 screws in the PCS group. Maximum load and load at failure differed significantly among the 3 groups. Stiffness and load at yield for the PCS group were significantly greater than those for the control and OCS groups but did not differ between the control and OCS groups. CONCLUSIONS AND CLINICAL RELEVANCE Use of bone cement and an orthopedic pin to fill the guide channel of cannulated screws significantly increased the strength of the construct, but ex vivo and in vivo studies are necessary before this augmentation technique can be recommended for clinical patients.

The paper deals with optimization of hollow sinking process of seamless steel tube E235. Specifically, the last two sequences are merged into one drawing pass by one tool. Saving one hollow sinking operation will save rebuilding on the drawing bench, tube handling and increase drawing capacity in short time. The input feedstock with outer diameter O18 mm and wall thickness 0.9 and 1.0 mm was drawn into tube with final dimension O10 × 1.0 mm by single-die and double-die. The aim of the numerical simulations was to compare the flow of material by means of monitored values (stress, deformation) in different technologies. The final drawn tubes differed in wall thickness. This is due to the stress-strain state in the deformation zone. Both simulation and experiment of cold drawing of O18 × 0.9 (1.0) mm hollow into O10 × 1.0 mm tube confirmed that the double-die configuration is inferior to the single-die one when it comes to the optimum material flow.

In this work an experimental study is made to find out the thermal performance of heat pipe solar collector (HPSC) using distilled water and R134a as working fluid. The HPSC is fabricated from the copper tube with the outer diameter of 58 mm and length of 1800 mm. The experimental work is carried out under different operating conditions. The input parameters such as temperature distribution and time on the thermal efficiency of the HPSC were investigated, compared and discussed. From the results, it is observed that the efficiency of the HPSC increases when R134a was used instead of distilled water.

To clarify deformation behavior of tubes in hollow sinking, the outer diameter and surface quality of the final drawn tubes were evaluated. Copper tubes were drawn for one pass under various drawing conditions (e.g., die reduction, drawing speed ratio, and die half angle) without an inner tool. The result of the experiment indicates the deformation behavior of tubes during hollow sinking. The outer diameter of the drawn tube on the die entrance became less than that of the starting material. Free surface roughening seems to develop on the outer surface of the drawn tube on the die entrance side due to the outer diameter reduction. Therefore, the height deviation in the outer uneven surface of the drawn tube on the die entrance became greater than that of the starting material. The height deviation on the die exit side was less than that on the die entrance side because of the tube deformations subjected by the die. The outer diameter decreased from the die approach end as either the drawing speed ratio or the die half angle increased. The height deviation in the outer uneven surface of the drawn tube on the die exit side became larger as the outer diameter decreased from the die approach end due to free surface roughening.

The process of tube drawing was carried out in laboratory conditions using a special drawing jig clamped in a testing machine. The aim of the performed experiment was to determine the influence of technological parameters, namely the plastic strain degree, friction and drawing speed on the magnitude of the drawing force and the accuracy of the dimensions of the tubes drawing. The main monitored parameter was the plastic strain degree, the values of which changed when drawing three tubes with outer diameters of O14, 16 and 18 mm to a final outer diameter of O12 mm. The paper evaluates the influence of the plastic strain degree on the magnitude of the force required to the tubes drawing and on the dimensional accuracy of the wall thickness of the produced tubes. Research has shown that the plastic strain degree had an effect on the thickening of the tube wall, with a greater increase in thickness at higher degrees of deformation. This positive change in thickness was within the permissible tolerances applicable to the producing of precision tubes.