Naoto Haruki

Drag and Heat Transfer Reduction Phenomena of Drag-Reducing Surfactant Solutions in Straight and Helical Pipes

Flow drag and heat transfer reduction phenomena of non-ionic aqueous surfactant solutions flowing in helical and straight pipes have been experimentally investigated at surfactant solution concentration range of 250-5000 ppm and temperature range of 5-20°C. The helically coiled pipes have curvature ratios range of 0.018-0.045. Experimental findings indicate that the friction factors and the heat transfer coefficients of the surfactant solution in helical pipes are significantly higher than in a straight pipe and lower than Newtonian fluid flow like water through the same coils in the turbulent drag reduction region. Drag reduction and heat transfer reduction increase with an increase in surfactant solution concentration and temperature in the measured concentration and temperature ranges. On the other hand, they decrease with increasing of the curvature ratio. A set of empirical expressions for predicting the friction factor and the average Nusselt number for the surfactant solutions flow through helical and straight pipes have been regressed based on the obtained data in the present experiments.

Fin Efficiency of an Annular Fin Composed of a Substrate Metallic Fin and a Coating Layer

An analytical solution to a composite annular fin made of a substrate metallic fin and a coating layer has been carried out. Useful expressions for calculating temperature distribution and fin efficiency have been derived. Comparing the analytical results to those of numerical calculation, the premise for the expressions is also explored. Theoretical analyzing results show that fin efficiency of a coated fin decreases with an increase of the coating layer thickness if the thermal conductivity of coating layer is much less than that of the substrate metallic fin. Whereas, the reverse influence of the coating layer thickness on the fin efficiency appears if the thermal conductivity of the coating layer is beyond the above range.

An experimental investigation of sorption process in fluidized bed with cooling pipe

An experimental investigation of a fluidized bed with multiple cooling pipes was conducted to study adsorption characteristics of a new organic sorbent desiccant material (HU300P) for a new air conditioning system. The mass ratio of the present sorbent desiccant powder type is from 1.3 to 2.3 times greater than that of silica gel. The sorption rate of the water vapor in the sorbent bed was measured under various conditions. It was found that the sorption rate is highly dependent on the effect of cooling pipes. The sorption ratio increases and the completion time for the sorption process decreases by using multiple cooling pipes.

Microalgal Culture for Chlorella sp. using a Hollow Fiber MembraneModule

A hollow fiber culture system has been proposed for supplying the carbon dioxide to the microalgae, to replace the conventional air bubbling system which has been adopted to supply carbon dioxide in most conventional microalgal culture. In order to examine the usefulness of hollow fiber membranes for the microalgal culture, the microalgal growth rate for Chlorella sp. and the effective mass transfer coefficient of carbon dioxide through the hollow fiber membranes have been measured using the proposed photobioreactor filled with hollow fibers. The microalgal growth rate using hollow fiber membranes was found to be three times greater than that observed in the conventional non-membrane photobioreactor. An experimental investigation has been conducted so as to evaluate the effect of the volume flow rate of the carbon dioxide and its concentration of the feed air through the hollow fibers on the microalgal growth rate. The present study clearly indicates that the hollow fiber membrane is quite useful for the microalgae culture in terms of enhancing both microalgal growth rate and dissolution rate of the carbon dioxide.

Flow drag and heat transfer reduction of flowing water containing fibrous material in a straight pipe

Abstract It has been well known that some kinds of surfactants are useful to reduce flow drag in a turbulent pipe flow by Toms effect. However, it is expensive to make these surfactants harmless to the environment. On the other hand, the fibrous material such as pulp fibers and cellulose are harmless additives to the environment. This paper deals with the drag reduction and heat transfer characteristics of the water suspension flow mixed with fine fibers in a circular straight pipe. Measurements of velocity and temperature profiles in a circular pipe were made in order to examine the flow drag and heat transfer characteristics of the turbulent and laminar flow. The nondimensional correlation equations of pipe flow resistance and heat transfer were derived in terms of various nondimensional parameters.

Flow resistance and heat transfer characteristics of organic brine (propylene glycol) solution by adding flow drag reduction additive

Abstract The flow drag and heat transfer reduction effect of brine solution is important technology for the effective energy consumption system. A non ionic surfactant (oleyldihydroxyetyl amine oxide) as the flow drag reduction additive was dissolved in an organic brine (propylene glycol) solution. The pipe friction and heat transfer coefficients of this brine solution have been measured for some experimental parameters. It was found that the flow resistance and heat transfer coefficients of this solution were decreased in the turbulent flow range, but the flow drag and heat transfer reduction tendency was varied with different ranges of the solution temperature.

Drag reduction and heat transfer characteristics of water solutions with surfactants in a straight pipe

The drag reduction and heat transfer characteristics of water solutions with two kinds of surfactants (cetyltrimethylammonium bromide and dodecyltrimethylammonium chloride) in a straight pipe were investigated experimentally. The flow resistance and heat transfer of water solution flow with the two kinds of surfactants were markedly reduced as compared with those of pure water flow. Useful nondimensional correlative equations for flow resistance and heat transfer were derived in terms of various nondimensional parameters.

Flow Drag and Heat Transfer Reduction Characteristics of Organic Brine (Potassium Acetate) and Inorganic Brine (Calcium Chloride) Solutions with Nonionic Surfactant

Flow drag and heat transfer reduction effects are useful in heat energy transportation systems and can lead to lower pumping energy requirements. The purpose of this research is to describe the flow drag and heat transfer reduction characteristics of organic (potassium acetate) and inorganic (calcium chloride) brine solutions. The nonionic surfactant oleyl dihydroxyethyl amine oxide (ODEAO) is used as a drag-reducing additive. The pipe friction coefficient and heat transfer coefficient are investigated experimentally in a straight pipe for each type of solution with ODEAO. These coefficients are found to be lower than those of water in the turbulent flow range. However, the rod-like micelles of ODEAO, which are necessary to induce the flow drag reduction effect, are not readily formed in these solutions. Hence, the flow drag and heat transfer reduction effects are measured only under limited conditions and it is difficult to apply these solutions practically as heat transfer media.