Izuru Senaha

Impingement heat transfer by jet issuing from a cross-shaped nozzle

Heat transfer characteristics and flow patterns were measured over a plate for various separation distances between the nozzle exit and target plate when air issues from a sharp-edged cross-shaped nozzle and impinges on a plate. The local heat transfer coefficients in the radial direction for different circumferential positions were calculated using the wall temperatures measured by means of thermocouples, and flow patterns were observed using an oil-titanium IV oxide method. The isotherms of the infrared images were also measured using an infrared radiometer with a two-dimensional array of indium-antimony (InSb) sensors. The geometric axes were switched as a result of the self-induced velocity of a vortex filament; the convex corners became flat and the concave corners generated outward ejection. The distributions of the iso-heat transfer coefficient contours correspond well to the flow pattern and the isotherm contours. These contours extended diagonally and demonstrated the St. Andrews cross pattern for short separations, subsequently changing to an octagonal pattern, and then becoming circular at large separations. The correspondence of the heat transfer characteristics to the flow behavior, as well as the heat transfer mechanism are also described.

Heat transfer control by using jet discharge in reattachment region downstream of a backward-facing step

The effect of an air jet perpendicular to the main flow across a backward-facing step on the local heat transfer and pressure coefficients was investigated. The relative height of the step and the position and velocity of the jet were varied, with the aim of controlling the heat transfer characteristics. The exit of the jet was set into the wall opposite the step, and created a bubble of circulating air downstream. The reattachment region of the main flow shifted upstream when the jet was moved upstream or its velocity increased in the case of jet located downstream of step, enhancing the heat transfer. When the jet was located nearly opposite the step, a bistable flow pattern was observed, characterized by different sizes of circulating bubble which created different heat transfer and pressure distributions.

Development of High-Speed and Large-Scale Culture Technology of Marine Algae Using Seawater with High Concentrations of Dissolved Carbon Dioxide

The effective use of marine biomass has recently been identified as a feasible method of renewable energy production. Therefore, to facilitate the effective use of algae biomass, it is essential to develop techniques for the mass production of algal cultures. It is also important to develop artificial culture techniques that are not affected by natural phenomena such as weather. This study utilized a newly developed culture technology that uses seawater with high concentrations of dissolved CO2 (CO2 seawater). The experiments in this study were conducted to test the effects of CO2 seawater on algal growth. In addition to experimental conditions that were previously investigated in industrial algae farming scenarios, it is also necessary to consider the effects of new parameters associated with increased CO2 concentrations. The following four conditions were experimentally investigated: (1) the tolerance of algae to changes in pH, (2) the effect of CO2 seawater on long-term culture growth, (3) the effect of continuous culture experiments, and (4) the effect of water flow rate on cultured algae. The results in terms of having excelled especially indicate that a 1-month long-term algae culture period in seawater with CO2 concentration of 1.0% led to growth that was approximately 4.5 times faster than growth in seawater without the CO2 additive. Furthermore, the results also provided useful information regarding the proper flow rate needed to enhance algal growth.

D224 The heat transfer enhancement mechanism on the forced convection by spraying a slight quantity of mist

This paper describes the heat transfer enhancement mechanism on the forced convection by spraying a slight quantity of mist in a channel of a backward-facing step flow. The mist reduces temperature of a main flow by displacement of the latent heat accompanying evaporation. In this research, about the above-mentioned phenomenon was done by both of the experiment and the computer simulation. And, we compared those results and considered that about the relation of the behavior and evaporation process of the mist. Finally, about the mechanism of the heat transfer enhancement by spraying a slight quantity of mist in a recirculation region was discussed.

Temperature Distributions on an lmpinged Plate with an Underexpanded Jet

The temperature distributions on a flat plate impinged by an underexpanded jet issued from a converging nozzle were measured using infrared camera for various pressure ratio with a fixed nozzle to plate separation L/D=5. As a result, it is found that the temperature near the stagnation point has a maximum value at the total pressure ratio of about 2.5. Moreover the contour maps of isotherms on the plate show that the temperature contours have azimuthal structures mainly with five apexes for relatively large pressure ratio, which means that even the underexpanded jet is issued from the circular nozzle, the temperature distributions are not axsymetric.

Heat transfer enhancement in a parallel plate duct by an oscillating thin plate insertion

Various arrangements were considered for two thin plates, oscillated by a flow in a parallel plate duct, with a view to enhancing the heat transfer along the duct. Heat transfer and pressure distributions were measured at varying the clearances from the wall and various plate separations. The maximum and mean Nusselt numbers have a Reynolds number dependence of Re 0.8 , and were, respectively, 2.3 and 1.6 times as large as those in fully developed turbulent flow, for air with Reynolds number ranging from 9,000 to 37,500. Full-field infrared imaging, a relatively new technique, was used to obtain the temporal and spatial temperature profiles on the wall surface. Isotherm contours of the infrared images correspond well to the heat transfer characteristics and flow