In order to acquire the basis of technical information that will be required for the design and operation of a sewage heat utilization system, this paper discusses the data analysis of operational performance at the DHC plant in Makuhari HB area. The methodology used in this study is to clarify the characteristics of a sewage heat utilization system from compound characteristics of the DHC plant that consists of various heating systems, and evaluate them.
On the basis of the data analysis of operational performance at the DHC plant in Makuhari HB area, it is examined how the properties of the sewage used as a heat source affect the effectiveness of the system. The result of this study suggests that a sewage heat utilization system is able to perform higher efficiency when it is designed as a distributed system that has separate heat sources than a central system.
A series of study has been performed on the metal hydride beds of Ti0.15Zr0.85Cr0.9Fe0.6Ni0.2Mn0.3Cu0.05 (MH-1, using for heat source), Ti0.73Zr0.27Cr1.2Fe0.3Ni0.1Mn0.4Cu0.05 (MH-2, using for cooling load) to measure the effective thermal conductivities. The effective thermal conductivities of MH alloy bed in hydrogen and helium have been examined. Experiment results show that pressure has great influence on effective thermal conductivity in low pressure range. And that influence decreases rapidly with increase of gas pressure. The reason is at low pressure, the mean free path of gas becomes greater than effective thickness of gas film which is important to the heat transfer mechanism. Then, carbon fiber has been used to try to enhance the poor thermal conductivity of MH alloy bed. Three types, two insert methods and three weight percentages of carbon fiber have been examined and compared. The highest effective thermal conductivity has been reached with carbon fiber which has second higher thermal conductivity, and highest weight percentage. This method has acquired 5.4 times higher thermal conductivity than pure metal hydride beds with quite low quantity of additives, only 1.7 wt % of carbon fiber. This is a good result comparing to other method which can reach higher effective thermal conductivity but needs much higher percentage of additives too.
In evaluating results of calorimetrical analysis of aqueous solutions using DSC, it is generally inadequate to use the usual method for pure materials, since the temperature of the solutions varies in wide range through the phase change process. In this study, the original method, in which the specific enthalpy of aqueous solution is expressed as a function of temperature and initial concentration, is proposed. Additionally, the formulation only using the properties of the solution was proposed and the functions of specific enthalpy were derived from the formulation. The functions were compared with the result obtained from DSC, using ethanol, ethylene glycol and Propylene glycol solutions as samples. Since these values agree well with each other, it is found that the function of specific enthalpy can also be obtained from the formulation. Finally, the advantages of this evaluating method for practical use were discussed.
The compressors for air conditioners require high efficiency and reliability. A rotary compressor usually has several micron-size gaps , which may deteriorate its efficiency and/or reliability ; therefore, it is necessary to figure out the behaviors of such gaps while the compressor is in motion, as the first step in developing them. Since the rotary compressors for air conditioners are small, it is difficult to install commercially available sensors to them to measure the gaps. Even it can be done, those sensors may have unacceptable measurement errors due to the temperature drift, because they are placed in the severe refrigerant and oil environment. Consequently, it is need to develop a new advanced sensor for those measurements. This paper describes the newly developed eddy current gap sensor, which is compact-size, heat-resisting and has less temperature drift. Furthermore, the dynamic behavior of the gaps of a rotary compressor in operation is also described, which was measured by it. Each gap was found to be smaller than the pre-estimated designed value. It also tuned out that one of factors was the deformation caused by the cylinder pressure.
This paper presents the heat transfer and pressure drop correlations for condensation in micro-fin tubes. Experimental data for eleven micro-fin tubes with different fin dimensions were used, and the refrigerants tested were R22, R123 and R134a. The predicted results using new correlations show good agreement with experimental results within an absolute deviation of ±30%. Experimental results for the micro-fin tubes were also compared with previous correlations for micro-fin Tubes.
For promotion of further energy conservation, development of a coolant with a higher heat capacity regulated around a room temperature is strongly required. As a candidate of such a new coolant, we employ the clathrate hydrate, i.e., a mixture of Tetra n-butyl ammonium fluoride (TBAF) and water. This clathrate hydrate is composed of the micro crystals with an order of 100 μm in dimension. It retains fluidity and melting point at a room temperature of about 25 °C. Moreover, the melting point is able to be controlled between 25 °C and 0 °C by changing the concentration of TBAF. The temperature can be regulated by its latent heat at the melting point. Characteristics such as the latent heat and the crystal structure of the clathrate have been experimentally obtained to confirm the feasibility for its usage as the latent heat storage around a room temperature.