Since hot-water supply has high percentage of energy consumption in residential sector, improvement in the efficiency of a gas water heater is an important issue. In order to improve thermal the efficiency of a gas water heater, an additional heat exchanger is required for latent heat recovery from the exhaust humid combustion. In this paper, the history of gas water heater, the technologies developed for latent heat recovery gas water heater and the recent progresses in the development of latent heat recovery heat exchanger are presented.
In this paper, the environmentally friendly recycling systems are introduced. The environmentally friendly mineral resource extraction, recycling and environmental technologies that utilize the multi phase flow are classified into different kinds of multiphase. In the mineral resources extraction, grinding, wet separation, flotation, magnetic separation and electrostatic separation are introduced. As for recycling technologies, short time crushing, jigging, heavy dense media separation, sink and float separation using magnetic fluid, fluidized bed, liquid-liquid separation, magnetic separation, triboelectrostatic separation are discussed. Water purification and recycling resources are also listed as the environmental technologies.
With a life style of healthy and sustainable (LOHAS) intention, superheated steam cooking ovens have attracted attention recently. According to the main issue of this review, the establishment of a resource saving society, we introduce an outline of the principle of superheated steam including its characteristics; the generating apparatus itself, the application of food processing including the sterilization, drying and environmental fields. Superheated steam is steam at a temperature higher than water's boiling point. If saturated steam is heated at constant pressure, its temperature will rise, producing superheated steam. To produce superheated steam in a power plant or for processes (such as cooking), the saturated steam, from the steam drum is passed through a super heater. Superheated steam has three heat characteristics; condensation heat transfer, convection heat transfer, and emission heat transfer, respectively. In the present review, we describe the induction heating of a carbon element for a generator. By using these merits, we applied them for food processing, including household cooking. Besides energy saving and environmental benefits, the oxygen-free atmosphere appears to improve product quality by retarding some deterioration reactions in food materials. Under-atmospheric pressures are often required with foodstuffs, which are sensitive to high temperatures due to denaturalization reactions. These benefits increase the added value of foodstuff, including unused or discarded natural resources by changing them into a powder. Superheated steam characteristics are useful for environmental remediation, especially recycle and reuse of active-charcoal and the washing and drying processes of the drum tube recycling industry and the same time we show not only the total cost saving, but also decreased dramatically energy and water exhaustion. From our evidence, we propose that superheated steam technology is useful in the food processing and environmental industries, but have a high potential for other industrial applications in the near future as well.
Biodiesel as fatty acid methyl esters is an alternative for fossil diesel that is commercially produced by transesterification of oils with methanol under vigorous stirring with an alkaline catalyst. This is because oils and methanol cannot be miscible each other to have two phase reaction system. For further dissemination, waste oils and unused plant oils with toxic substances should be efficiently used as biodiesel. However, the alkali-catalyzed method is not simply applicable to the lower-grade waste oils, because such oils contain not only triglycerides as major component but also free fatty acids as minor component, the latter of which reacts with alkaline catalyst to produce saponified products. Therefore, non-catalytic supercritical methanol methods such as one-step supercritical methanol method (Saka Process) and two-step supercritical methanol method (Saka-Dadan Process) have been developed. By these methods, transesterification of triglycerides and esterification of free fatty acids proceed simultaneously without any catalysts, because the ionic products of methanol is increased in its supercritical condition, while a dielectric constant of methanol is decreased such that triglycerides and methanol can become miscible each other in its supercritical state and its reactivity can be tremendously enhanced. After completion of its reaction, however, fatty acid methyl esters as biodiesel can be phase-separated from methanol in an ordinary condition. Thus, pure biodiesel can be readily achieved. Such attracting behaviors of supercritical fluid technology were discussed to overcome problems in two-phase reaction system in the alkali-catalyzed method.
In slow freezing of water that includes solutes, pure ice is produced and most of the solutes are removed from the frozen phase and concentrated in an unfrozen liquid phase. At fast freezing rate, however, large part of the solutes from solution is captured into the freezing interface and then the solution is not concentrated. To prevent this capture of the solutes, the strong agitation of the freezing interface is very effective. We have been studying the applicability of ultrasonic irradiation to the agitating method, and found that the freeze concentration efficiency of solutes is improved greatly by this irradiation. In this paper, the effects of the freezing rate and the ultrasonic irradiation on the freeze concentration characteristics are reported.
The aim of this work is to investigate the influence of the addition of alcohol on the behavior of an external-loop airlift reactor with a porous plate. The mass transfer parameter in dilute aqueous solutions of three aliphatic alcohols (methanol, ethanol and n-propanol) was examined using five kinds of porous plates. The results showed that dilute alcohol addition enhanced dramatically liquid-phase volumetric mass transfer coefficient, kLaR, in the riser, especially led to the remarkable enhancement of that for the porous plate having small pore diameter due to smaller bubble diameter than with water system. This behavior is enhanced by alcohols with long carbon chain lengths probably due to the inhibition of bubble-bubble coalescence at the porous plate and in the liquid. This surprising result might be explained by a strong increase in kL values in liquid-phase volumetric mass transfer coefficient due to the increasing amount of small bubbles leading to large partial pressure of transfer component within bubbles based on capillary pressure as explained previously . Also, the results showed that the liquid-phase volumetric mass transfer coefficient increased with the concentration of alcohol, but led to reduction of the volumetric mass transfer coefficient over any critical concentration for each porous plate. Moreover, empirical equation for liquid-phase volumetric mass transfer coefficient is obtained.