This paper presents the melting behavior and heat transfer characteristics of a water-insoluble m... more This paper presents the melting behavior and heat transfer characteristics of a water-insoluble material immersed in water. N-hexadecane, popularly used as a phase change material, is adopted as a water-insoluble material. A rectangular n-hexadecane solid is placed vertically in the water. The melting behavior of n-hexadecane and its melting rate are then observed under a variety of water temperature conditions in the test vessel. An evaluation of the melting behavior and the local heat transfer coefficient indicates that the ambient water flow along the vertical n-hexadecane block enhances heat transfer at the upper side of the block as the ambient water temperature becomes lower. The upward flow of the melting liquid prevents the melting heat transfer at the upper part of the block as the ambient water temperature becomes higher. The variation of the shape of the top part of the block then changed and the heat transfer coefficient barely decreased when Polyoxyethylene Sorbitan Monooleate (Tween 80) was added in the water.
New Challenges for Winter Road Service. XIth International Winter Road CongressWorld Road Association - PIARC, 2002
This paper describes how, in cold regions, snow and ice accretion to road accessories causes seri... more This paper describes how, in cold regions, snow and ice accretion to road accessories causes serious damage. In particular, information necessary for traffic safety does not reach road users when snow or ice adheres to road signs. For this reason, the prevention of accretion and the removal of accreted snow and ice are significant for ensuring safe road traffic in winter. In recent years various methods for controlling snow and ice on road signs have been suggested. This method chiefly depend on shifting the stagnation points of airflow from the standpoint of fluid mechanics, or an application of ice-accretion retardant materials made of water-repellant silicon or fluorine resin. However, no methods have been completely successful in controlling snow and ice. This paper proposes a new control method for the prevention of snow and accretion to road signs that is inexpensive to implement and maintain.
International Journal of Thermophysics, Mar 1, 1997
The paper is concerned with measurenaents of the surface tension of aqueous binary solutions at l... more The paper is concerned with measurenaents of the surface tension of aqueous binary solutions at low temperatures. The eflects of both temperature and concentration on the surface tension of CaCI,. NaCIO~, and propylene glycol have been investigated. A differential capillary-rise method was employed lbr the measurements. The results showed that the surface tension of CaCI 2 and NaCIO~ increases monotonically as the concenm~tion of the solution increases, while for the propylene glycol solution the surlace tension decreases with increasing concentration. The surface tension of the testing liquids was found to be an almost-linear function of temperature from 20'~C to just above the freezing temperature. Equations lbr the surface tension of the three aqueous binary solutions as a function of temperature and concentration are presented.
This paper presents the flow and heat transfer characteristics of an ice slurry flow through cyli... more This paper presents the flow and heat transfer characteristics of an ice slurry flow through cylinder arrays. A mixture of ice particles and trehalose water is utilized as the testing ice slurry. Experiments are carried out under some parameters such as a velocity of the ice slurry, a heat flux, and a layout of cylinder array. The distribution of the local heat transfer coefficient on the surface of a heated cylinder is evaluated. In addition, flow behavior in the test section is observed carefully as well. Experiments using an aqueous solution as a testing fluid are also carried out, and the specific characteristics of ice slurry relative to single phase liquid are discussed. It is found that the staggered layout of cylinders shows higher heat transfer coefficients than the aligned layout setting.
Proceedings of the 23<sup>rd</sup> IIR International Congress of Refrigeration: Prague, Czech Republic, August 21-26, 2011. Overarching theme: Refrigeration for Sustainable Development., Aug 21, 2011
Polymer electrolyte fuel cell (PEFC) has been developing as clean power generation technology. Ho... more Polymer electrolyte fuel cell (PEFC) has been developing as clean power generation technology. However, there are some subjects to spread PEFC among industries and homes in the world. The one of such subjects is drop in power generation performance and durability caused by heat and mass distribution in a single cell of PEFC. The purpose of this study is to point out the dominant factor of heat and mass transfer phenomena and clarify the reason for heat and mass distribution in a single cell. With the aid of observation window, the in-plane temperature distribution in single cell under power generation was measured by thermograph. The influence of operation conditions on temperature distribution was investigated. Moreover, to clarify the heat and mass transfer mechanism theoretically, the simulations to investigate the factor needed for the ideal reaction and evaluate the influence of separator structure on heat and mass distribution were carried out.
This paper discusses a pulsating heat pipe (PHP) using a self-rewetting fluid. Unlike other commo... more This paper discusses a pulsating heat pipe (PHP) using a self-rewetting fluid. Unlike other common liquids, selfrewetting fluids have the property that the surface tension increases with temperature. The increasing surface tension at a higher temperature can cause the liquid to be drawn towards a heated surface if a dry spot appears, and thus to improve boiling heat transfer. In experiments, 1butanol and 1-pentanol were added to water at a concentration of less than 1 wt% to make self-rewetting fluid. A pulsating heat pipe made from an extruded multiport tube was partially filled with the self-rewetting fluid water mixture and tested for its heat transport capability at different input power levels. The experiments showed that the maximum heat transport capability was enhanced by a factor of four when the maximum heater temperature was limited to 110ºC. Thus, the use of a self-rewetting fluid in a PHP was shown to be highly effective in improving the heat transport capability of pulsating heat pipes
This paper presents the melting behavior and heat transfer characteristics of a water-insoluble m... more This paper presents the melting behavior and heat transfer characteristics of a water-insoluble material immersed in water. N-hexadecane, popularly used as a phase change material, is adopted as a water-insoluble material. A rectangular n-hexadecane solid is placed vertically in the water. The melting behavior of n-hexadecane and its melting rate are then observed under a variety of water temperature conditions in the test vessel. An evaluation of the melting behavior and the local heat transfer coefficient indicates that the ambient water flow along the vertical n-hexadecane block enhances heat transfer at the upper side of the block as the ambient water temperature becomes lower. The upward flow of the melting liquid prevents the melting heat transfer at the upper part of the block as the ambient water temperature becomes higher. The variation of the shape of the top part of the block then changed and the heat transfer coefficient barely decreased when Polyoxyethylene Sorbitan Monooleate (Tween 80) was added in the water.
New Challenges for Winter Road Service. XIth International Winter Road CongressWorld Road Association - PIARC, 2002
This paper describes how, in cold regions, snow and ice accretion to road accessories causes seri... more This paper describes how, in cold regions, snow and ice accretion to road accessories causes serious damage. In particular, information necessary for traffic safety does not reach road users when snow or ice adheres to road signs. For this reason, the prevention of accretion and the removal of accreted snow and ice are significant for ensuring safe road traffic in winter. In recent years various methods for controlling snow and ice on road signs have been suggested. This method chiefly depend on shifting the stagnation points of airflow from the standpoint of fluid mechanics, or an application of ice-accretion retardant materials made of water-repellant silicon or fluorine resin. However, no methods have been completely successful in controlling snow and ice. This paper proposes a new control method for the prevention of snow and accretion to road signs that is inexpensive to implement and maintain.
International Journal of Thermophysics, Mar 1, 1997
The paper is concerned with measurenaents of the surface tension of aqueous binary solutions at l... more The paper is concerned with measurenaents of the surface tension of aqueous binary solutions at low temperatures. The eflects of both temperature and concentration on the surface tension of CaCI,. NaCIO~, and propylene glycol have been investigated. A differential capillary-rise method was employed lbr the measurements. The results showed that the surface tension of CaCI 2 and NaCIO~ increases monotonically as the concenm~tion of the solution increases, while for the propylene glycol solution the surlace tension decreases with increasing concentration. The surface tension of the testing liquids was found to be an almost-linear function of temperature from 20'~C to just above the freezing temperature. Equations lbr the surface tension of the three aqueous binary solutions as a function of temperature and concentration are presented.
This paper presents the flow and heat transfer characteristics of an ice slurry flow through cyli... more This paper presents the flow and heat transfer characteristics of an ice slurry flow through cylinder arrays. A mixture of ice particles and trehalose water is utilized as the testing ice slurry. Experiments are carried out under some parameters such as a velocity of the ice slurry, a heat flux, and a layout of cylinder array. The distribution of the local heat transfer coefficient on the surface of a heated cylinder is evaluated. In addition, flow behavior in the test section is observed carefully as well. Experiments using an aqueous solution as a testing fluid are also carried out, and the specific characteristics of ice slurry relative to single phase liquid are discussed. It is found that the staggered layout of cylinders shows higher heat transfer coefficients than the aligned layout setting.
Proceedings of the 23<sup>rd</sup> IIR International Congress of Refrigeration: Prague, Czech Republic, August 21-26, 2011. Overarching theme: Refrigeration for Sustainable Development., Aug 21, 2011
Polymer electrolyte fuel cell (PEFC) has been developing as clean power generation technology. Ho... more Polymer electrolyte fuel cell (PEFC) has been developing as clean power generation technology. However, there are some subjects to spread PEFC among industries and homes in the world. The one of such subjects is drop in power generation performance and durability caused by heat and mass distribution in a single cell of PEFC. The purpose of this study is to point out the dominant factor of heat and mass transfer phenomena and clarify the reason for heat and mass distribution in a single cell. With the aid of observation window, the in-plane temperature distribution in single cell under power generation was measured by thermograph. The influence of operation conditions on temperature distribution was investigated. Moreover, to clarify the heat and mass transfer mechanism theoretically, the simulations to investigate the factor needed for the ideal reaction and evaluate the influence of separator structure on heat and mass distribution were carried out.
This paper discusses a pulsating heat pipe (PHP) using a self-rewetting fluid. Unlike other commo... more This paper discusses a pulsating heat pipe (PHP) using a self-rewetting fluid. Unlike other common liquids, selfrewetting fluids have the property that the surface tension increases with temperature. The increasing surface tension at a higher temperature can cause the liquid to be drawn towards a heated surface if a dry spot appears, and thus to improve boiling heat transfer. In experiments, 1butanol and 1-pentanol were added to water at a concentration of less than 1 wt% to make self-rewetting fluid. A pulsating heat pipe made from an extruded multiport tube was partially filled with the self-rewetting fluid water mixture and tested for its heat transport capability at different input power levels. The experiments showed that the maximum heat transport capability was enhanced by a factor of four when the maximum heater temperature was limited to 110ºC. Thus, the use of a self-rewetting fluid in a PHP was shown to be highly effective in improving the heat transport capability of pulsating heat pipes
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