Michio Yanadori

Heat transferential study on a heat storage container with phase change material

Abstract This paper presents heat transfer characteristics of a heat storage container utilizing latent heat storage material, calcium chloride hexahydrate (melting point 28°C). The heat storage container is consisted of a vertical cylindrical pipe with a vertical heat transfer tube at the center and the latent heat storage material containing into the cylindrical pipe. The heat release and heat transfer characteristics during the solidification of the latent heat storage material are experimentally studied. The following results are obtained. The relation between the time and total heat flow rate, that is, the heat release characteristics have the following three stages: (1) the stage of sensible heat release from liquid heat storage material, (2) the latent heat release stage, (3) the stage of sensible heat release from solid heat storage material. The actually measured values of thermal resistance show a tendency similar to that of the theoretical values, but their absolute values are smaller than those of theoretical values by about 40%. This is because the solidified crystals of heat storage material do not grow in circular shape concentric with the heat transfer pipe but grow in dendritical shape, and dendritical crystallized portions function as fins.

Heat transfer study on a heat storage container with a phase change material. (Part 2. Heat transfer in the melting process in a cylindrical heat storage container)

Abstract Calcium chloride hexahydrate as a latent-heat storage material is placed in a vertical cylindrical heat storage container, and a vertical single pipe for heat transfer purpose is also inserted in the container. In this setup, the heat transfer rates during melting of the heat storage material are measured. It is shown that heat transfer from the heat transfer pipe to the heat storage material is largely influenced by natural convection at the melting liquid layer section. Also, regarding heat transfer at this melting liquid layer section, a new experimental equation useful for thermal design of heat storage containers has been established.

Fundamental study of the melting process of crushed ice in a heat storage container

This report deals with heat transfer in the melting process of crushed ice filling an ice/water heat storage container. The volumetric heat transfer rate and melting end-times are measured for the cases when rectangular-type, small-stone-type, and particle-type ice in the container are melted using circulating warm water. The melting end-time is shortest for small-stone-type ice and longest for particle-type ice. The volumetric heat transfer rate is greater for small-stone-type ice and rectangular-type ice than for particle-type ice. The flow rate of the circulating warm water fed into the tank from an inlet pipe has a major effect on the heat transfer rate.

Study on the heat-flow controllable heat exchanger (1st report): Thermal characteristics of heat-flow controllable heat exchanger

Abstract To regulate temperature in passive solar houses and green houses, the authors have developed a heat exchanger capable of controlling the heat flow. It has a thermal switch mechanism without mechanically moving parts. It consists of an evaporator, a condenser, a vapor passage pipe, a liquid return pipe having an inverted-U-pipe, and a heater mounted on the inverted-U-pipe. The heat exchanger can transfer, or reduce to zero, heat from the evaporator to the condenser by regulating a slight heater input. The authors have fabricated a model of the heat-flow controllable heat exchanger to examine its thermal switching and heat exchange characteristics, and then compared the obtained results with calculation results. It was clarified that the experimental results agree with the calculation results.

Study on the heat-flow controllable heat exchanger (2nd report): Dehumidification in the greenhouse by the ventilation type dehumidifier with heat-flow controllable heat exchanger

A novel ventilation type dehumidifier with heat-flow controllable heat exchanger was installed on the wall of a greenhouse. Dehumidification and heat recovery experiments were conducted. The construction of the novel dehumidifier is simpler than that of the conventional dehumidifier with a compressor. It was found that the required input for the ventilation type dehumidifier was less than that of a conventional dehumidifier with compressor.

Cold energy release characteristics of an ice/air direct contact heat exchanger

This paper deals with the cold energy release characteristics of an ice/air direct contact heat exchanger. Characteristics of the outlet temperature, humidity, and time history of heat release are examined when the initial height of the ice-cube-packed bed in the heat exchanger is changed. The following results were obtained in these experiments: (I) Inlet air of 30 °C is lowered to about 0 °C when passed through the heat exchanger, and the absolute humidity of the outlet air is reduced to about a quarter of that of the inlet air. (2) There is an optimum height of the ice-cube-packed bed to maximize the amount of cold energy release. (3) This heat exchange method can supply about twice as much cold energy as is released by an ordinary fin-tube-type heat exchanger even if the air velocity in the heat exchanger is reduced to about 0.38 times that of the fin-tube-type heat exchanger. (4) A nondimensional correlation equation for predicting the time taken for the ice-cube-packed bed to completely melt is derived.