As part of grappling with energy saving and the global environmental protection, the tendency evaluating cost, energy consumption and environmental load generated by production activity during the product life cycle is remarkably rising. Applying this to the operation phase of heat sources system, the multiobjective decision making will be requested in order to decide the system operation strategy, from the viewpoint of the optimal operation including criteria other than the cost minimum operation. In this paper, we proposed a method that the importance degree of each criterion in the multiobjective decision making environment composed of two or more criteria is extracted by the interaction with a decision maker and that multiobjective optimal solution of the heat sources system operation scheduling is derived from the acquired preference information. Moreover, we presented the results of the multiobjective optimal operation scheduling simulation of a model heat sources system by using the proposed method and compared the results with that of the single objective optimal operation scheduling.

View full abstract

The purpose of this study is to estimate the reliability level for building facilities. In the previous paper (Part 1), we proposed the Reliability Interval Estimation Chart, and we analysed the field data by the two kinds of interval estimation methods. Moreover, we discussed the Bayesian method in estimating the MTBF, and then analysed it by using the data of building facilities. So in this paper, the authors estimate and evaluate many parameters of the failure time distribution by computer simulation. We simulate the exponential distribution in random numbers, normal distribution and Weibull distribution by the probability paper method, likelihood method and the Bayesian method. And we discuss these results and the interval estimation etc.. Moreover we simulate the building facility in the random failure rate. The paper has emphasised the importance of having the treatment of few field data for building facilities.

View full abstract

In this study, the characteristics of air-mass and heat transport within an atrium are systematically analyzed by means of model experiments and CFD, Computational Fluid Dynamics. In this paper, experiments with a model of 1/20 scale are systematically carried out in order to examine the influence of heat flux through the walls on flow and temperature fields within a model atrium under occupied zone cooling. The results of the experiments are the following: (1) the heat flux through the ceiling has considerable influence on the indoor thermal environment, (2) reduction (or removal) of the heat flux through the ceiling reduces vertical temperature distribution and enlarges suitable space for occupancy, (3) the heat flux through the floor considerably influences on vertical temperature distribution and the height of cooled zone space for occupancy, which has approximately same temperature as one at an exhaust inlet, (4) and when the recirculating flow caused by heat flux through the wall restrains the recirculating flow caused by supply jet, the air mixing is reduced in the lower part of the space and the height of cooled zone space for occupancy is lowered. This decrease of the occupied zone height is better for the occupied zone cooling system from the thermal load point of view.

View full abstract

This paper describes a method to calculate the basic weighting factors by solving a total of 16 heat balance equations including the surface of furniture against a unit pulse excitation absorbed by the i th interior surface and to obtain the cooling load weighting factors for solar heat gain through windows without blinds by combining the basic weighting factors and the distribution ratios of solar radiation transmitted through windows without blinds on each surface of the room calculated from an approximate equation proposed by Xia and Kimura in accordance with the basic theory of dynamic cooling load calculation for air-conditioning as described in the 11th edition of SHASE Handbook. Calculation results indicate that the basic theory and calculation procedures of the 11th edition of SHASE Handbook are valid and the weighting factors relating space cooling load to solar radiation transmitted through windows without blinds calculated from present paper are quite different from the values of SHASE because of considering the thermal delay characteristics of furniture in this study. This study confirms that the thermal delay characteristics of furniture has a substantial influence upon estimating the space cooling load from solar heat gain through windows without blinds.

View full abstract

In the present paper the measured environment and operation of a ventilation system of a subway station for six years long are reported. Then the calculated temperatures using computer simulation are compared with the measured values. The followings are results obtained; 1) The air temperature of the platform is 14 degree Celsius higher than the outside air in winter, therefore, heat recovery from the exhaust air can be appreciated. 2) In summer, it can also be utilized as a free cool energy. source because the air temperature of the platform and the tunnel is often lower than the outside. Especially the tunnel air is more useful since the temperature is normally cooler than outside for a whole day. 3) In the subway system the air temperature has risen gradually after construction. The rate of increase was 1.02 degree Celsius in 6 years after construction. 4) During the summer in 1994, the ventilation system was operated for whole days to prevent water vapor condensation at the stations of a newly extended line. As the results the air temperature of the platform decreased about 0.5 to 1.0 degree Celsius in comparison with the temperature during the normal ventilation schedule. 5) The humidity difference between inside and outside seems not to be significant, in other words, the water vapor generated from people and ground water in the subway does not have much effect on the environment of a subway system. 6) It was recognized that CO_2 concentration increases in rush hours by about several tens of ppm, however, the increase is not significant. 7) The measured air temperatures sufficiently agreed with the results obtained by the computer simulation method proposed in our previous research even though some assumptions differ from the real.

View full abstract

In the previous paper, the authors developed the simulation model of artificial waste heat from buildings equipped with air-conditioning systems. Using this model, it is proved that under the whether condition in Osaka, the amount of sensible waste heat which affects the thermal environment in urban areas is quite different, depending upon the air-conditioning systems used. In this paper, the same simulation has been carried out under various climatic conditions observing the influence of wheather conditions to the characteristic of waste heat. Moreover, the amount of thermal load to the atmosphere (including the heat flux from ground surface in a specific business area) was calculated. From the Results, it is proved that the infleuence of air-conditioning systems to the total sensible heat flux from the district is quite large.

View full abstract

Stopping air conditioning system in a few minutes, passive indoor temperature change will be caused. The Passive Rhythming Air Conditioning System is a new proposal for air conditioning method using this temperature change. This method repeats passive temperature change once or twice an hour. To stop air conditioning system is one of the most effective energy conservation method. But, the influence of temperature change on thermal comfort should be examined. This paper describes the results of subjective experiments on the effects of passive temperature change on thermal comfort conducted in summer season. The main results are as follows; 1) There are no difference on thermal comfort between the Passive Rhythming Air Conditioning System and ordinary (constant temperature control) system in case of 26℃ of base temperature. 2) In case of 5 and 10 minutes of stopping period in the Passive Rhythming Air Conditioning System, subject's vote on comfort are rather better than ordinary systems. 3) It is suggested that the Passive Rhythming Air Conditioning System is the favorable air conditioning system especially for females.

View full abstract

For developing the calculation model of compression type refrigerators used in generalized simulation tools for energy estimation of air-conditioning systems, a method based on cooling and heat rejection rates and power input of compressors is proposed. The linear relationship between the cooling rate and the inlet chilled and cooling water temperatures were conducted so that the calculation model of refrigerators can easily be combined with another component of the whole system to be simulated. The experiment was carried out using a refrigerator with a cooling capacity of 19.2kW for validating the calculation model. The results showed that even in the conditions of variable chilling water inlet temperature, the calculated values agreed with the measured results within an allowable range of the error for applying the simulation of air conditioning systems. The hour by hour simulation procedure with the on/off controlled refrigerating system is also examined with the part load ratio curve obtained using the results of the experiment.

View full abstract

From the economical viewpoint in large indoor spaces such as factories and atriums, it is desirable to limit the air conditioned space to the specific area occupied. This paper analyzes about new local air conditioning system where the Coanda effect of a plane jet is utilized. When the plane jet is discharged from a slot horizontally into a half-confined space opening upward and at the opposite end, the jet is forced to curve and attaches to the floor, forming a cavity space covered by the jet. By applying warm or cool jet, we can use this cavity space for air conditioning. However when the warm plane jet is discharged, the Coanda effect does not usually occur by the influence of buoyancy. In this paper, first, we analyzed the trajectory of the warm jet, considering the effect of the pressure difference produced by the entrained air, so that we could find the critical conditions where the Coanda effect appears. As the results the critical condition, represented as a function of modified Archimedes number and denoted by K_c for the warm jet where the Coanda effect occurs, was identified as K_c=1.0k_p^<-0.96> (k_p: center line velocity constant). Secondly, we analyzed the air temperature difference between inside and outside of the cavity space by applying the characteristics of the free non-isothermal jet. Temperature difference ratio in the cavity is found to be represented as in the following equation. Δθ_i/Δθ_o≒0.90(H_s/k_ph)^<-1/2> Δθ_i, Δθ_o: temperature difference between cavity and room air, outlet and room air, respectively, h: slot width, H_s: height of slot location.

View full abstract

We made a basic study on the heat supply temperature level of Combined Heat and Power (CHP) system, from both sides of enthalpy and exergy, by defining performance indices. Rising temperature level does not affect the total thermal efficiency of the CHP plant with a back-pressure turbine, but decreases it with an extraction-condensing turbine. The total exergy efficiency increases slightly or barely varies of both type as supply temperature rising. The saving ratio of primary energy to the conventional system in which power and heat energy are generated individually, increases with supply temperature lowering as far as the CHP plant itself. However, taking acount of power demand and heat loss for conveyance of heat, it has been seen that there exist optimal points in heat supply temperature.

View full abstract