This paper describes the effectiveness of residential combined heat and power (CHP) systems by using load following gas engine in cold regions for energy conservation. First, evaluation of the basic performance of gas engine CHP system was executed. The AC electrical efficiency and heat recovery efficiency were 21.6% and 53.9% at approx. 1.2 kW, and the high performance was maintained at lower load conditions. Second, the dependence rate on electric power of each house was more than 80%. Finally, comparison with a rated output gas engine and the optimum energy demand conditions for the load following gas engine were shown by numerical analyses.
We would like to report regarding the latest absorption chiller-heater, which has reduced energy consumption drastically by increasing efficiency at the partial load by two methods in the following. One of methods is to control the circulated solution flow rate optimally, and the other is to expand the operation range to a lower temperature for cooling water. Furthermore, Absorption chiller-heater has been also optimized for replacement work. The weight of absorption chiller-heater is reduced thoroughly by a new design of high temperature generator, and the replacement work for it is carried out easily and successfully to avoid an additional work such as reinforcement work for the existing foundation.
In the field of the air-conditioning equipment for vehicles, the conversion to HFO1234yf from R134a is considered in recent years. Furthermore, heating by HP is considered with the spread of a hybrid car, EV(s), etc. Under such circumstances, the demand to a high-efficiency heat exchanger is increasing, and the performance improvement of air-side which affects the performance of a heat exchanger greatly becomes important, especially. In this research, the optimization technique which used CFD and an experimental design method about corrugated louver fin mostly used with the air-conditioning equipment for the present vehicles for the purpose of optimization of the air side heat transfer characteristic of a heat exchanger was established.
The quality of ice cream surface degrades significantly from alteration of the surface properties due to the repetition of thaw-recrystallizing accompanied with temperature vibration at subzero temperature, a little above the melting temperature. For understanding the phenomena in detail, ice crystals in ice cream after once thawed and recrystallized was observed morphologically, and evaluated quantitatively by fractal analysis. It was shown that the shape of ice crystal recrystallized from once thawed ice cream was modified from round shape to complex shape, of which the degree depended on thawing temperature at subzero temperature. However, the ice crystal retuned gradually into round shape with increasing the holding time at the thawing temperature. These phenomena would be caused by spatial micro distribution of high concentration part which was organized in thawed ice cream by freezing concentration. That is, the complex ice crystal formed in thawed ice cream at subzero temperature would be induced by losing the micro uniformity of concentration.
We have focused on the novel desiccant dehumidification system, which is operated under isothermal condition by using heat exchanger as a desiccant unit. In this system, thermal energy generated by adsorption phenomena is removed by flowing heat exchanging fluid during dehumidification process, resulting that it is expected to achieve a large amount of dehumidified water by promotion of adsorption. In this study, a fundamental investigation was performed to estimate overall mass transfer coefficient of water vapor on silica-gel, which controls the dehumidification rate of the system, under isothermal condition. Adsorption experiments were isothermally conducted using copper tube coated with silica-gel on the inner wall under various air velocity, thickness of adsorbent and humidity of inlet air conditions. The overall mass transfer coefficient was determined by fitting experimental result with numerical one. As a result, it was found that overall mass transfer coefficient increased with increasing air velocity and decreasing thickness of silica gel coated. In addition, the mass transfer coefficient of water vapor was formulated as a function of Reynolds number and thickness of adsorbent.
It is effective to supply the chickens with cooled drinking water to prevent heat exhaustion of them in summer. In this study, drinking water cooling system installed in chicken coop is investigated. In the system, double tube heat exchanger is used. Drinking water is filled in the outer tube and is cooled by cooling water flowing in the inner tube. The temperature of drinking water depends on the ambient temperature, insulation of the tubes, cooling power of the chiller and flow rate of the cooling water. In this study, using simple formulations, the average temperatures of drinking water and cooling water are estimated and the temperature distribution of drinking water in the heat exchanger is calculated. Additionally, the guide for selecting the chiller suitable for the water cooling system is proposed.
An advanced solar air conditioning system for commercial use was developed. Features of the system are (1) a single/double effect combined absorption chiller utilizes solar hot water by priority and the natural gas consumption is minimized, (2) to reduce heat capacity and heat loss, the system has no storage tank, and (3) a developed controller minimizes the electric consumption of hot water pump and enhances the collector efficiency by measuring solution temperature. Through the demonstration, (1) the chiller was driven only by the solar hot water when the air conditioning demand was low, (2) chilled water temperature was stable by controlling the back-up gas burner, and (3) the pump was operated only when the solar hot water temperature reaches high enough but as low as possible to drive the chiller. The CO2 emission was reduced by about 16% from April 2010 to March 2011, compared with the previous system.
A numerical calculation method has been developed to determine the optimum thawing method for minimizing the increase of metmyoglobin content (metMb) as an indicator of color change in tuna meat during thawing. In this paper, the effects of different thawing media, such as warm water or cold air, is investigated in terms of increasing metmyoglobin content predicted by numerical calculation. Subsequently, we carried out the validation of so-called thermal equalize thawing, i.e., the combined thawing method using both hot water and cold air as thawing media, which is popularly used by professional chefs. As a result, it is confirmed the thermal equalize thawing reduces thawing duration without spoiling the quality of fish meat. In addition, we attempt to evaluate the improved thermal equalize thawing that employs three times repeating of placing into hot water and cold air.
The extracellular matrix (ECM) of frozen tissue has been histologically investigated by applying the cryocoating method improved by Fink (1986) as well as the immunohistochemical staining. Sections of frozen tuna tissue for light microscopy was obtained by the cryocoating method that consisted of coating the surface of the precut tissues by a coating media and drying it until a coating film was formed. Additionally, an immunohistochemical staining was attempted to stain the ECM in the section of tuna tissue prepared by the cryocoating method. The target molecular of the immunohistochemical staining was laminin that is one of the major proteins included in the ECM. As results, it was found that the cryocoating method could prepare the sections with minimal alteration of the ice crystal shapes in frozen tuna as well as Kawamoto method. By using the immunohistochemical staining combined with the cryocoating method, it was revealed that the ice crystals caused damages not only on the cytoplasm but also on the ECM. Further, image analysis told us that the area ratio of the ECM is decreased considerably from 4.8% to 1.0% during freezing, while the cytoplasm is less decreased from 95.2% to 50.0%.
In this paper, ice layer containing many bubbles was formed by freezing high density micro-bubble water on a copper plate, which was tilted downward. We observed the ice layer and obtained its closed-porosity by measuring volume of the ice layer. From the results, it was found that larger bubbles due to coalescence of micro-bubbles were trapped in the ice layer and caused reduction of closed-porosity and of freezing rate. The larger bubbles, however, reduced with tilting the cooling plate because they could not hold on the tilted surface of the ice layer. We show that the cooling plate tilted at 30 degrees angle to horizontal formed a high closed-porosity ice layer with keeping freezing rate. In addition, a heat transfer analysis of the process was carried out and was validated by comparison with the experimental results. The analysis results revealed a relation between velocity of ice layer surface and porosity. And finally, the analysis results of constant cooling rates provide optimum cooling conditions for forming gas-containing ice, in which amount of contained gas is maximum.