The progress of the two-phase flow research can be divided into four stages. These periods are 1948-1959, 1960-1970, 1971-1979, and 1980-1990. In this 6th Report, the initiation of research into flow oscillation in the natural circulation loop of boilers and boiling water reactors in the first period (1948-1959) is introduced. Also described is the progress of research on flow instability, that is, flow oscillation, in circulation loops conducted for the development of boiling water reactors at the initial stages of the second period.
It is well known that the ice heat storage system is an attractive way of using night-time electric power energy, of saving thermal energy and an effective use of narrow building space. There are numerous ice heat storage systems on the market although there has been no good evaluation of these systems. This review deals with the ice formation mechanism for ice-making methods based on the previous literature. Particular attention is paid to the way the appearance of the ice nucleus and the growth of the ice front are strongly influenced by the water supercooling phenomenon. Moreover, ice crystal growth is explained from the standpoint of molecular and heat transfer theory.
Ice storage is becoming popular due to the peak electricity demand problem and for other reasons of technical interests. This paper overviews the state of the art from the viewpoint of feasibility compared to water thermal storage. Developments in HVAC application technologies and correct evalution methods of the thermal characteristics in the tank are required.
In order to analyze accurately the thermohydrodynamic behavior of gas-liquid two-phase flows, it is important to obtain the appropriate basic equations of mass, momentum and energy conservation. The basic equations presently used are obtained based on the two-fluid model assuming that both phases are continuous fluid. However, when these equations are applied to a dispersed flow such as a bubbly or droplet flow, problems arise regarding matters such as the physical interpretation of each term and ill-posedness. In view of the above, simplified and physically reasonable basic equations for gas-liquid dispersed flows were developed based on the assumptions that phase change rate and/or chemical reaction rate are not so large at interface, that there is no heat generation in a dispersed phase and that a dispersed phase can be treated as isothermally rigid particles. Based on the local instant formulation of mass, momentum and energy conservation of the dispersed flow, time-averaged equations were obtained. It is shown that, in the derived averaged momentum equation, the terms of pressure gradient and viscous momentum diffusion do not appear and that, in the energy equation, the term of molecular thermal diffusion heat flux does not appear. These characteristics of the derived equations were shown to be very consistent concerning the physical interpretation of the gas-liquid dispersed flow. Furthermore, the basic equations obtained always maintained their well-posedness as regards the initial value problem.