Fulop-Tsutsui interactions on quantum graphs

We examine scale invariant Fulop-Tsutsui couplings in a quantum vertex of a general degree $n$. We demonstrate that essentially same scattering amplitudes as for the free coupling can be achieved for two $(n-1)$-parameter Fulop-Tsutsui subfamilies if $n$ is odd, and for three $(n-1)$-parameter Fulop-Tsutsui subfamilies if $n$ is even. We also work up an approximation scheme for a general Fulop-Tsutsui vertex, using only $n$ $\delta$ function potentials.Comment: 14 pages elsevier format, new references adde

On the properties of simple quantum graphs

高知工科大学博士(工学) 平成20年9月30日授与 (甲第146号)高知工科大学, 博士論文.thesi

A PCM-WATER HEAT EXCHANGER WITH POLYMERIC HOLLOW FIBRES FOR LATENT HEAT THERMAL ENERGY STORAGE: A PARAMETRIC STUDY OF DISCHARGING STAGE

The paper presents a theoretical parametric study into latent heat thermal energy storage (LHTES) employing polymeric hollow fibres embedded in a phase change material (PCM). The polymeric hollow fibres of five inner diameters between 0.5mm and 1.5mm are considered in the study. The effectiveness-NTU method is employed to calculate the thermal performance of a theoretical LHTES unit of the shell-and-tube design. The results indicate that the hollow fibres embedded in a PCM can mitigate the drawback of low thermal conductivity of phase change materials. For the same packing fraction, the total heat transfer rates between the heat transfer fluid and the PCM increase with the decreasing diameter of the hollow fibres. This increase in the heat transfer rate and thus the efficiency of the heat exchange to some extent compensate for the energy consumption of the pump that also increases with the decreasing fibre diameter

Experimental investigations of the performance of a solar air collector with latent heat thermal storage integrated with the solar absorber

The paper deals with experimental investigations of the performance of a solar air collector with latent heat thermal storage integrated with the solarabsorber. The main purpose of heat storage in solar thermal systems is to store heat when the supply of solar heat exceeds demand and release it when otherwise. A number of heat storage materials can be used for this purpose; the phase change materials among them. Short-term latent heat thermal storage integrated with the solar absorber can stabilize the air temperature at the outlet of the collector on cloudy days when solar radiation intensity incident on a solar collector fluctuates significantly. Two experimental front-and-back pass solar air collectors of the same dimensions have been built for the experimental investigations. One collector had a “conventional” solar absorber made of a metal sheet while the solar absorber of the other collector consisted of containers filled with organic phase change material. The experimental collectors were positioned side by side during the investigations to ensure the same operating conditions (incident solar radiation, outdoor temperature)

Experimental investigations of the performance of a solar air collector with latent heat thermal storage integrated with the solar absorber

The paper deals with experimental investigations of the performance of a solar air collector with latent heat thermal storage integrated with the solarabsorber. The main purpose of heat storage in solar thermal systems is to store heat when the supply of solar heat exceeds demand and release it when otherwise. A number of heat storage materials can be used for this purpose; the phase change materials among them. Short-term latent heat thermal storage integrated with the solar absorber can stabilize the air temperature at the outlet of the collector on cloudy days when solar radiation intensity incident on a solar collector fluctuates significantly. Two experimental front-and-back pass solar air collectors of the same dimensions have been built for the experimental investigations. One collector had a “conventional” solar absorber made of a metal sheet while the solar absorber of the other collector consisted of containers filled with organic phase change material. The experimental collectors were positioned side by side during the investigations to ensure the same operating conditions (incident solar radiation, outdoor temperature)

PIV measurement of separated flow in a square channel with streamwise periodic ribs on one wall

In. this study, particle image velocimetry (PIV) is used to investigate the physical process of separated flow in a square channel roughened with periodically transverse ribs on one wall. The ribs obstruct the channel by 15% of its height and are arranged 12 rib heights apart. The Reynolds number based on the bulk-mean velocity and the corresponding hydraulic diameter of the channel, is fixed at 22,000. Assuming flow periodicity in the streamwise direction, the investigated domain is between two consecutive ribs. The emphasis of this study is to give some insight into the turbulence mechanism associated with separation, reattachment, and subsequent redevelopment. Results are included for mean velocity, friction coefficient, vorticity thickness, Reynolds shear stress, anisotropy parameter and production of turbulent kinetic energy and shear stress. Based on the two-point correlation profiles, Taylor microscales are derived to reveal the sizes of the turbulence structure in the longitudinal and lateral directions. Moreover Galilean decomposition is applied to the instantaneous velocity fields. The result shows that the separated shear layer is dominated by the large-scale, unsteady vortical structures

Sundn, PIV measurements of separated flow in a square channel with streamwise periodic ribs on one wall

In this study, particle image velocimetry (PIV) i