Solar Thermal Application for the Dairy Industry in Taiwan

Taiwan has been developing clean energy and solar heating for hot water production is a mature technology. The subsidy program (2000-2016) for solar water heaters means that the cumulative area of solar collectors installed was approximately 2.52 million square meters at the end of 2016, in which more than 93% have been installed in the domestic sector. Industrial heat processes represent an area for solar thermal application. This study presents field measurements for solar water heaters installed for sterilization in dairy industry. Global solar radiation can be correlated with the system’s thermal efficiency reasonably well. As a pre-heating system, financial viability is validated.

Reynolds number effect on compressible cylindrical cavity flow

Presence of a cavity changes the mean and fluctuating pressure distributions inside and near the cavity.For cylindrical cavity flow,the diameter-to-depth ratio is the dominant factor.In this study,flow is naturally developed along a flat plate with two different lengths,resulting in different incoming boundary layer thicknesses ahead of the cavity.The effect of Reynolds number based on incoming boundary layer thickness on characteristics of mean and fluctuating pressure distributions is addressed.Pressure sensitive paint was also used to visualize the mean surface pressure patterns.The effect of Reynolds number on the classification of compressible cylindrical cavity flow and self-sustained oscillating frequency is not significant.An increase in Reynolds number results in a reduction in the value of differential pressure or momentum flux near the rear edge.

Self-sustained oscillation for compressible cylindrical cavity flows

The presence of a cavity changes the mean and fluctuating pressure distributions. Similarities are observed between a cylindrical cavity and a rectangular cavity for a compressible flow.The type of cavity flow field depends on the diameter-to-depth ratio and the length-to-depth ratio.The feedback loop is responsible for the generation of discrete acoustic tones. In this study, the selfsustained oscillation for a compressible cylindrical cavity flow was investigated experimentally. For open-type cavities, the power spectra show that the strength of resonance depends on the diameterto-depth ratio（4.43–43.0） and the incoming boundary layer thickness-to-depth ratio（0.72–7.0）. The effective streamwise length is used as the characteristic length to estimate the Strouhal number. At higher modes, there is a large deviation from Rossiter＇s formula for rectangular cavities. The gradient-based searching method was used to evaluate the values of the empirical parameters. Less phase lag and a lower convection velocity are observed.

AModeling Study on ParticleDispersion inWall-Bounded Turbulent Flows

Three physicalmechanismswhichmay affect dispersion of particle’smotion in wall-bounded turbulent flows,including the effects of turbulence,wall roughness in particle-wall collisions,and inter-particle collisions,are numerically investigated in this study.Parametric studies with differentwall roughness extents and with different mass loading ratios of particles are performed in fully developed channel flows with the Eulerian-Lagrangian approach.A low-Reynolds-number k−ǫturbulence model is applied for the solution of the carrier-flow field,while the deterministic Lagrangian method together with binary-collision hard-sphere model is applied for the solution of particle motion.It is shown that the mechanism of inter-particle collisions should be taken into account in the modeling except for the flows laden with sufficiently low mass loading ratios of particles.Influences of wall roughness on particle dispersion due to particle-wall collisions are found to be considerable in the bounded particleladen flow.Since the investigated particles are associated with large Stokes numbers,i.e.,larger than O(1),in the test problem,the effects of turbulence on particle dispersion aremuch less considerable,as expected,in comparison with another two physical mechanisms investigated in the study.