The Effect of Parameter Variation on Spiral Flow Inducing Cannula Performances

Spiral flow-inducing cannula has been shown in previous research to exhibit a considerable effect on flow hemodynamic. However, there is still room for improvement. In this study, several design variations were tested to determine which variants were the best in terms of flow reduction. Computational Fluid Dynamics (CFD) software was used to simulate flow within a spiral flow-inducing cannula with several variations from chamber width and angle differences. The variants were compared against each other by using several flow parameters and a selection method was employed to determine which model was the best. It was found that a variant that has the widest chamber (14 mm) and biggest angle opening (70°) from the chamber to the cannula tube was the best in several parameters, and as such was chosen as the best variant. When compared with the standard straight cannula, the reduction in flow output was recorded to be 30% which is deemed significantly. In conclusion, spiral flow cannula recorded better hemodynamic effects with lower outflow velocity and wall shear stress value.

Bi-Directional Impulse Turbine with Spiral Flow Collector for Tidal Energy Conversion

In order to make use of ocean renewable energy, a combination system of a bi-directional impulse turbine and a bi-directional flow collector for tidal current energy conversion is investigated in this paper. It is the advantage that this turbine system does not need an operation of orientation change according to the reversal of regular tidal orientation when fixed on the seabed. The experimental investigations by using both a circulating water tank and a towing tank showed that the turbine power output could be increased by adopting the flow collector proposed in this study. Then the flow collector with fixed spiral vane named spiral flow collector was investigated by both a circulating water tank test and CFD analysis. The experimental result of the spiral flow collector showed that the performance improvement was found on the increase of axial velocity in the turbine which contributed to the increase of the turbine power output. The results of CFD analysis showed that 180 deg of the skew angle of the fixed spiral vane was suitable in view of the angular moment at the turbine inlet in this case.

Energy and Economic Analysis of Curved, Straight, and Spiral Flow Flat-Plate Solar Water Collector

In this work, the solar water collector flow tube geometry is modified as curved and spiral to enhance the system’s performance. The investigation is carried out experimentally under the meteorological conditions of the Kovilpatti region (9°10 ′ 0 ″ N, 77°52 ′ 0 ″ E), Tamil Nadu, India. The flow pipes of the solar water heater are made of copper material which has higher thermal conductivity to recover the water heat as thermal energy. The influence of the mass flow rate (MF) on the flow pipes with respect to the surface temperature for various configurations of the flow tubes is investigated. The two MFs of 0.0045 kg/s and 0.006 kg/s are tested. The MF of 0.006 kg/s yields the maximum efficiency of 73% compared to the other MF. The straight, curved, and spiral tubes yielded the maximum efficiency of 58%, 62%, and 69%, respectively, at 0.0045 kg/s. Similarly, the MF of 0.006 kg/s obtained an efficiency of 62%, 65%, and 73% for straight, curved, and spiral flow tubes, respectively. The economics and exergy of the system are analyzed. The maximum exergy efficiency of the collector is estimated to be 32% for the MF of 0.0045 kg/s for the spiral flow collector, and for the 0.006 kg/s MF, the obtained exergy efficiency is 27% for the spiral flow water heater. The economic analysis revealed that the expense is $0.0608 and $0.0512 worth of hot water produced for the domestic space heating.

Numerical Simulation Study on Flow Laws and Heat Transfer of Gas Hydrate in the Spiral Flow Pipeline with Long Twisted Band

The natural gas hydrate plugging problems in the mixed pipeline are becoming more and more serious. The hydrate plugging has gradually become an important problem to ensure the safety of pipeline operation. The deposition and heat transfer characteristics of natural gas hydrate particles in the spiral flow pipeline have been studied. The DPM model (discrete phase model) was used to simulate the motion of solid particles, which was used to simulate the complex spiral flow characteristics of hydrate in the pipeline with a long twisted band. The deposition and heat transfer characteristics of gas hydrate particles in the spiral flow pipeline were studied. The velocity distribution, pressure drop distribution, heat transfer characteristics, and particle settling characteristics in the pipeline were investigated. The numerical results showed that compared with the straight flow without a long twisted band, two obvious eddies are formed in the flow field with a long twisted band, and the velocities are maximum at the center of the vortices. Along the direction of the pipeline, the two vortices move toward the pipe wall from near the twisted band, which can effectively carry the hydrate particles deposited on the wall. With the same Reynolds number, the twisted rate was greater, the spiral strength was weaker, the tangential velocity was smaller, and the pressure drop was smaller. Therefore, the pressure loss can be reduced as much as possible with effect of the spiral flow. In a straight light flow, the Nusselt number is in a parabolic shape with the opening downwards. At the center of the pipe, the Nusselt number gradually decreased toward the pipe wall at the maximum, and at the near wall, the attenuation gradient of the Nu number was large. For spiral flow, the curve presented by the Nusselt number was a trough at the center of the pipe and a peak at 1/2 of the pipe diameter. With the reduction of twist rate, the Nusselt number becomes larger. Therefore, the spiral flow can make the temperature distribution more even and prevent the large temperature difference, resulting in the mass formation of hydrate particles in the pipeline wall. Spiral flow has a good carrying effect. Under the same condition, the spiral flow carried hydrate particles at a distance about 3–4 times farther than that of the straight flow.