Survey results of energy saving policy in electric furnace steelmakers and estimated volume of saving energy by exhaust heat recovery in the electric furnaces are reported in this paper. First, the survey results show that more than 30 percent and 90 percent of plants have not studied effective utilization of thermal energy of the electric furnaces inside and outside of the plants, respectively. However, the survey results also show that more than 80 percent and 40 percent of the plants are willing to use the thermal energy of the electric furnaces inside and outside of the plants, respectively. Second, a measurement of cooling water and exhaust gas temperatures in a typical electric furnace shows 66 percent of input energy is used for crude steel production and the rest is lost as the exhaust gas, etc. Third, based on the heat budget analysis, the volume of the steam production by exhaust heat recovery in electric furnaces is estimated to be 11.9t/h for an electric furnace which produces 80t/h of crude steel.

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A series of research including this report aims at the construction of control techniques that achieve the stable operating of the heat source machine enabling the reduction in the water transportation power by controlling flow rate and differential pressure between headers in primary water system. In this report, we were examined the method of improving the stability of heat source machine flow rate to the turbulences such as sudden changes of heat load flow rate and heat source machine operating number changes that was a big problem of primary water system. As a result, the differential pressure setting value between headers was shown when turbulence did not influence it when the operating frequency was calculated by using heat souse system's P-Q model (including pump P-Q property, heat souse machine and others resistance) of the measured heat source system and when the influence of turbulence had been received, the method of calculating the differential pressure measurements between headers as a parameter was shown. It was confirmed that the fluctuation band and the restoration time of heat source machine flow rates were improved as a result of verifying whether the stability of heat source machine flow rate to the sudden change of heat load flow rate improved it by the experiment. Moreover, it was confirmed to the heat source machine operating number change and the change in the heat load flow rate that a steady operating was possible though the variable differential pressure between headers and variable flow rate was controlled by using the heat source system where the different model composed of the ice thermal storage unit and heat pumps.

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This paper proposes a daily periodic simulation method of design thermal peak load by using Expanded AMeDAS design weather conditions. This method was developed for a building energy simulation tool, the BEST and has the following features. (1) The heat balance between multiple zones can be simultaneously solved, (2) it is applicable to any warming-up hours or pulling-down hours assumed in pick-up load calculations for intermittent operation, (3) it is applicable to the cases in which the heating and cooling equipment operates intermittently more than once a day, and (4) it is useful for the evaluation of thermal environment during warming-up or pulling-down hours by using short time intervals for simulation. In the presented method of pick-up load calculation, the minimum thermal capacities that can satisfy the required zone thermal environment at the end of warming-up or pulling-down hours are obtained through iterations. The design peak loads were evaluated by the results from simulations through ten years and the proper warming-up or pulling-down hours assumed in the design simulation were examined. The results of design thermal peak load simulation in a residential houses were also presented.

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The thermal energy storage tanks of multi-connected mixing type have been installed in HVAC systems. Some thermal energy storage tanks, however, have dead water zones due to a buoyancy effect with an improper arrangement and/or an excessive size of connecting holes. In this study, it is purpose to make a mixing model of the thermal energy storage tank considering buoyancy effect. In this paper, a mixing model which based on a mixing model of temperature-stratified thermal energy storage tank was presented. Calculated results by using the mixing model agreed well with results of model experiments and measurements of an actual thermal energy storage tank. Some simulations for thermal energy storage tanks were conducted under various connecting holes conditions. The simulation results for the tank efficiency of thermal energy storage tank were described with the connecting holes conditions. Some ways to improve storage tank efficiency were considered based on the results.

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The energy consumption of air-conditioning system generally accounts for about half of the whole energy consumption of the buildings for business purposes. Usually, the system and machine capacities are designed based on the maximum thermal load. Therefore, in many cases, the system provides inefficient performances under the partial load most of the time. In this paper, we focus on a central heating and cooling plant systems installed in over-medium-sized building. We have developed two low-cost control methods to reduce energy consumption realizing the improvement of system efficiency in low load operation. One is Chillers "0" unit operation control, which shuts down the chillers and circulates only cold and hot water in very low load. The other one is online real-time operation optimized operation control, which optimizes the set values that generally are fixed and maintained in the real time. We adopted these two low-cost control methods to the system in the real building, and proved how effective they work.

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This paper constitutes Part 2 in the series of studies on a radiator made of plastic pipes for air conditioning. A cooling radiator with condensation made of plastic pipes was developed and its cooling performance was estimated to solve the problem that the steel panel radiators for mainly cooling use are expensive for residential use. The cooling capacity without condensation per heat transfer surface area of the plastic radiator is close to that of a palisade steel panel radiator. However, the cooling capacity without condensation per projected area of the plastic radiator is larger than that of the steel radiator because the narrow pitch of the plastic radiator enables the ratio of the heat transfer surface area to the projected area higher. The cooling capacity with condensation per heat transfer surface area of the plastic radiator is smaller than that of the steel radiator because of the low dehumidification performance. However, the cooling capacity with condensation per projected area of the plastic radiator is equivalent to that of the steel radiator.

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