Natural Rubber Tube Research Articles

High-performance polymer-based regenerative elastocaloric cooler

Alternative methods of refrigeration are critical for performance optimization and environ- mental sustainability. Prototype systems using caloric materials have shown the advantages of a high coefficient of performance (COP) and low global warming potential. Elastocaloric elastomers can meet ongoing needs, but their implementation in functional heat pumps or coolers remains challenging due to their requirement for a large deformation and low thermal conductivity. Moreover, a scalable design is required to achieve high cooling power. As a leap forward for the use of polymers in larger scale caloric devices, we developed experimental elastocaloric polymer coolers with two different geometries using natural rubber tubes. We confirmed that a suitable geometry partially compensated for the low thermal conductivity and led to performances comparable to those of other caloric devices. Several operating conditions were tested to determine the optimal temperature span, cooling power, and COP for both device geometries. Under a specific operating condition, one of the prototypes exhibited a maximum temperature span > 8 K, a maximum COP of 6, and an output cooling power of 1.5 W; this power outperforms other prototypes based on polymers or ceramics. The parallelization of rubber tubes will facilitate realistic elastocaloric polymer coolers on a larger scale.

Regenerative cooling using elastocaloric rubber: Analytical model and experiments

Caloric materials exhibit significant entropy variations when applying appropriate excitation, pushing forward the development of solid-state cooling systems. Their development includes materials' properties optimization, with a focus on their adiabatic temperature change when driven at their limit. In order to sustain the device development, an analytical model for regenerative cooling systems is presented in this work. It consists of a caloric material driven cyclically so that it exhibits harmonic temperature variations, whereas an oscillating fluid layer is exchanging heat with the caloric material, leading to a net heat flux along one given direction. The heat transfer equation was solved analytically for harmonic excitations along the direction perpendicular to caloric material layers separated by fluid layers. In the second step, the problem was solved along an axis parallel to the layers. In order to validate the model, an experimental proof of concept was developed based on a natural rubber tube inside which water flows harmonically. The comparison between the model and experiment is given, while the model highlights the importance of the thermal boundary layer and how the geometry of the device easily compensates for the low thermal conductivity of natural rubber.

巻フィルムチューブ式SMA人工筋肉アクチュエータのモバイル化と拮抗配置による剛性制御手法の検討

The endoskeleton humanoid robot needs an artificial muscle that is comparable with a human muscle from a viewpoint of form, flexibility, output force, output displacement and the responses. For this realizing, we are studying a Shape Memory Alloy (SMA) actuator that protected by a rolled film tube have the high heat resistance and the high flexibility. In this study, this actuator is inserted into a natural rubber tube for mobilizing and experimented about its antagonistic stiffness control.

Elastic properties of natural rubber tubes produced by dip‐coating

AbstractThe mechanical properties of rubber tubes produced by dip‐coating technique and the influence of the fabrication process on their structural properties were evaluated. Cyclic tension versus deformation tests were performed to investigate the elastic properties of the samples and to understand the changes in rubber tubes behavior under repetitive stress. The effect of the wall thickness on the elastic response of the tubes was also studied. The mechanical properties of opened tubes were also investigated for transversal and longitudinal directions to evaluate the influence of the fabrication process on the alignment of the polymer chains. This investigation indicated that the fabricated tubes are resistant and extremely elastic. They can be elongated up to 800% of its initial length before rupture, and thicker tubes are a bit more resistant to elongation than the thinner ones. In addition, the fabricated tubes have an anisotropic structure due to the fabrication process. Finally, natural rubber tubes may have a great potential to be used as vascular prosthesis, or in other applications that require a large range of resistance and elasticity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 702–707, 2006

Analysis of Self-Excited Oscillation of Fluid Flow in a Collapsible Tube by Introducing Incremental Theory

This study is to simulate the self-excited oscillation taking place in a flow of the collapsible tube such as a venular vessel or a natural rubber tube. In order to understand the mechanism, one dimensional model is used to formulate the strong interaction between fluid and tube. In flow region, it is assumed that one dimensional incompressible flow with varying widths of tube is considered. The stabilized Galerkin method combined with the predictor multi-corrector algorithms is im plemented. In structure region, the beam element is used for longitudinal deformation of the tube and the experimental formula, tube law, been employed to evaluate the circumferential stiffness. The tube is subjected to very large deformation and unstable, bucking, characteristic. Then, we tried to introduce incremental theory of virtual work principle. The HHT-α method is also used in the timeintegration schemes. By introducing the incremental formulation, significant improvement is obtained. The mechanism and the relationship between pressure and deformation of the self-excited oscillation were shown in these computations of simple model.

Elucidation of propulsive force of microrobot using magnetic fluid

Using the pattern of the peristaltic movement of an earthworm, a microrobot was developed for traveling in a tube using a magnetic fluid. In this microrobot, a cell equivalent to a segment of the earthworm is composed of a natural rubber tube into which a water-based magnetic fluid is sealed up. The cells are connected with rod-like elastic bodies of natural rubber. It was confirmed that this robot can travel in an acrylic tube (inner diameter: 12 mm, outer diameter: 14 mm) by providing a shifting magnetic field from the exterior. This article will describe how our microrobot is propelled, the mechanism of its propulsion, and the analytical results of the propulsive force.

349 磁性流体を用いた蠕動運動型ロボット

Using a magnetic fluid, the earthworm-type robot was developed for running the peristaltic movement. In this earthworm-type robot, a cell equivalent to a segment of the earthworm is composed of a natural rubber tube into which a water-based magnetic fluid is sealed up. The cells are connected with rod-like elastic bodies of natural rubber. It was confirmed that this robot can travel in an acrylic tube (inner diameter : 12mm, outer diameter : 14mm) by providing a shifting magnetic field from the exterior. This article will describe the pattern of the peristaltic movement of an earthworm, how our earthworm-type robot moves, the mechanism of its movement.

F-0811 柔軟なチューブ内の流れの動的特性(S43-3 呼吸・循環系の数値シミュレーション)(S43 生体力学シミュレーション)

This is the study of the self-excited oscillations taking place in a flow of a collapsible tube such as a venular vessel or a natural rubber tube. In order to understand the mechanism, a one-dimensional simple model is used to formulate the strong interaction between the fluid and tube. The beam element is used for the longitudinal deformation of the tube and an experimental formula, tube law, is employed to evaluate the circumferential stiffness in the incremental forms. It is assumed that there is one dimensional incompressible flow with varying widths. The governing equation is expressed in the form of symmetric systems. Also, a stabilized method combined with the predictor multi-corrector algorithm is implemented. The mechanism and the relationship between pressure and deformation of the self-excited oscillation were shown in these computations of a simple model.

Performance monitoring of a thermosyphon solar hot water heater with a parallel thermoplastic natural rubber tube absorber

Performance monitoring of a domestic hot water thermosyphon solar collector with TPNR (thermosplatic natural rubber) tubing as the absorber plate was conducted. A commercial blend of TPNR (DVNR 9011) was used as the absorber plate. The domestic hot water thermosyphon solar collector system used was the parallel-type absorber plate. An output temperature output of 65°C was obtained from the collector for a typical day of 550 W m −2 and ambient temperature of 26°C. For the performance monitoring, two methods were used. In the first method, the storage tank was filled up with water the night before the test and temperature readings were recorded form sunrise to sunset. The tank was then drained during the night-time, refilled and made ready for the next day's test. The end-of-the-day temperature rise in the storage tank and the accumulated total solar radiation values were also noted over the same period. The tests were repeated under varied environmental conditions that covered low and high radiation intensities. A temperature rise of 30°C in the storage tank was obtained for this system at an average yearly value of accumulated solar radiation of 4.5 kWh m −2. In the second method, the temperature readings without draw-off or draining of the hot water from the storage tank were recorded for six days and a temperature range of 60–70°C was obtained in the storage tank. Hence, this system has the potential to be used as a domestic thermosyphon solar hot water heating system.

Propagation of sound waves in a multi-layered viscoelastic tube.

Theoretical and experimetal investigation are given on the propagation of sound waves in a cylindrical viscoelastic tube of multi-layered material. In the analysis, the locally reacting model is applied for the tube wall vibration. Simplified theory is presented in the case of single-layered and two-layered tubes, and the influence of the tube wall thickness on the resonance of the wall vibration is discussed. The phase velocity and absorption of sound waves are measured by using silicone and natural rubber tubes. The experimental results are in good agreement with the theoretical prediction. The same measurements for two-layered tube which is made by inserting the natural rubber tube into the silicone rubber tube are done and are compared with the theory.

Modification of natural rubber by different grafting techniques

An attempt has been made to graft a hydrophylic monomer of N,N.dimethyl acrylamide (DMAA) onto natural rubber (NR) tube by simultaneous, per-oxidation and preirradiation grafting techniques. It was found that the grafting by simultaneous grafting technique results a maximum 29 wt% degree of grafting and by peroxidation and preirradiation techniques, results the maximum 42 wt% and 13 wt% degree of grafting, respectively. It was concluded that the peroxidation technique is the most appropriate to obtain a high degree of grafting in radiation copolymerization of DMAA onto NR.

Blood compatibility assessment of graft copolymer (NR-g-DMAA) tubes

Graft copolymer (NR-g-DMAA) tubes have been prepared by using simultaneous radiation-induced grafting of N,N-dimethyl-acrylamide, CH 2CHCON(CH 3) 2, (DMAA) onto natural rubber (NR) tubes. The blood compatibility of the NR-g-DMAA tubes was assessed with three methods, namely in vitro test, ex vivo once through test and ex vivo loops test. In the case of the in vitro test, a simple whole blood contacting procedure has been employed. The ex vivo once through test involves the exposing of NR-g-DMAA tubes with once through flow of fresh canine blood and then it was inspected for any evidence of clot. In the case of ex vivo loops test, the NR-g-DMAA tube was implanted at external jugular vein of a mongrel canine and the blood flow in the NR-g-DMAA tube was detected with an ultrasonic flow meter. It was found that the blood compatibility of NR-g-DMAA tubes is improved significantly with the increasing degree of grafting. All the NR-g-DMAA tubes having a degree of grafting of about 30 wt % or more exhibit good blood compatibility. It was also found that the blood compatibility of the NR-g-DMAA tube is better than that of a medical grade silicon rubber (SiR) tube.

Performance of a tubular elastic sparger

AbstractElastic spargers were made from natural latex rubber tubes by repeatedly piercing the tube wall with a lance‐shaped needle to make multiple, axially‐aligned, slit‐like punctures. Gas holdups, volumetric mass transfer coefficients and pressure drops were measured at several gas flowrates for single elastic spargers oriented vertically in a column of liquid, and compared with the corresponding measurements for a rigid sparger.

Modification of natural rubber tubes for biomaterials. II. Radiation‐induced grafting of N,N‐dimethylaminoethylacrylate (DMAEA) onto natural rubber (NR) tubes

AbstractRadiation‐induced simultaneous grafting of N,N‐dimethylaminoethylacrylate (DMAEA) onto NR tubes has been studied to improve blood compatibility of NR tubes. In the grafting of DMAEA onto NR tubes, effect of grafting parameters such as solvent, monomer concentration, temperature, dose, and dose rate on the grafting yield was investigated. As the results, it was found that the grafting proceeds effectively in the presence of carbontetrachloride (CCI4) as a solvent. The initial rate of grafting was found to be proportional to 0.70 power of dose rate and to 0.95 power of monomer concentration. The activation energy for this grafting system was calculated to be 6.78 kcal/mol. The evaluation of blood compatibility of NR‐g‐DMAEA was carried out by ex vivo test. Blood compatibility of those samples was found to be dependent on only grafting yield. When the degree of grafting is higher than 30 wt %, blood compatibility of NR tube could be improved by DMAEA grafting. This is the same tendency which that of previous grafting system of NR‐g‐DMAA.

Modification of natural rubber tubes for biomaterials I. Radiation‐induced grafting of N,N‐dimethyl acrylamide onto natural rubber tubes

AbstractRadiation‐induced simultaneous grafting of N,N‐dimethyl‐acrylamide (DMAA) onto natural rubber (NR) tubes has been studied to improve blood compatibility of the NR tubes. Concerning grafting of DMAA onto NR tubes, it was found that the grafting proceeds effectively in the presence of carbon tetrachloride (CCl4) as a solvent. The degree of grafting was found to be saturated at about 26 wt%, but a higher degree of grafting can be obtained by either “so called two‐step grafting” or “putting a standing time for a while before irradiation.” The initial grafting rate was proportional to 0.85 power of dose rate. The apparent activation energy of the graft‐copolymerization was 7.42 kcal/mol. Evaluation of blood compatibility of DMAA‐grafted NR tubes has been carried out by ex vivo test. According to the results, significant improvement of blood compatibility was obtained for the samples in which degree of grafting is higher than 30 wt%.

Development of a circulatory model to predict the change in the hemodynamics between with and without pumping of a left ventricular assist device(LVAD)

During the LVAD pumping, it is difficult to evaluate the degree of the cardiac function of the natural heart. To solve this problem, a mechanical circulatory model with which the cardiac function of the natural heart can be predicted without stopping of the LVAD pumping has been developed. This model was a closed circuit composed of three pulsatile pumps as the LVAD and the right and left heart, five compliance tanks as the capacitance elements of the blood vessels and three needle valves as the peripheral resistance. The outflow conduit from the left heart was specially designed by using a natural rubber tube, the inertance and capacitance of wich were similar to those of the natural aorta. To simulate some of the control of circulation, two servo mechanisms for the automatic control system were designed and incorporated in the simulator. One was used for the control of the cardiac output based on a “Staring's law, ” and the other was used for the control of pre-capillary resistance simulating the autonomic control. The specifications of this system were determined on the basis of the physiological data. Twelve pairs of clinical hemodynamic data of on/off tests of LVAD pumping were analyzed with this simulation system. Firstly, the standard hydrodynamic condition during LVAD pumping were determined in the mock circulatory system referred from the pumping-on data of the clinical cases. Then, the LVAD was stopped and hydrodynamic simulation data during the stop of LVAD pumping were obtained. When these predicted data were compared with the corresponded human hemodynamics, the difference in the cardiac output between simulation and clinical data was kept within only ±0.1L/min in each test. The differences in the left atrial pressure and the aortic pressure were within ±2.5mmHg and ±5.0mmHg, respectively. These data suggested that our simulation model has an adequate characteristics to predict the change in the hemodynamics of the clinical cases and it will provide many useful informations to know the recovery process of the filing heart and to determine the optimal control strategy of the LVAD.

Generation and Propagation of Finite-Amplitude Waves in Flexible Tubes

Highly reproducible finite-amplitude waves, generated by a modified electromagnetic plane-wave generator, characterized by a rise time <0.5 μsec, peak pressures of 20–100 bar, and time constants of 5–10 μsec in the exponential pressure decay behind the front, are propagated along the axes of water-filled steel, perspex, and natural rubber tubes (30–50 mm i.d., 40–100 mm o.d.). Using new, very small piezoelectric transducers with a high natural frequency, pressure-time functions are measured at different axial and radial tube positions. The frequency domain equation for wave propagation in elastic fluid-filled tubes is developed and solved numerically on an IBM 360/75 computer for water-filled tubes of steel and perspex in the frequency range 1 kHz–1 MHz, giving dispersion curves for phase and group velocities of the first six propagation modes. Using the fast Fourier transform technique on the initial finite-amplitude waves together with (1) the dispersion relationship for the Fourier components, (2) a mode selection procedure, and (3) a new expression for choosing the interval of integration, the waves are “synthesized” again at different tube positions. Surprisingly good agreement between measured and calculated pressure—time functions is found. The work throws new light on the distribution of energy in the modes of propagation and on the influence of parameters of the materials considered on finite-amplitude wave propagation.