This report describes a development on a gas engine heat pump which plays topping part of a hybrid heat pump. This hybrid heat pump will be marketed not only for office buildings but also hotels and apartments, and one of the main features is to produce high temperature hot water (70〜80℃) from low temperature unused energy. Judging from the present environmental situation, non-azeotropic refrigerant was adopted instead of CFCs by refrigeration cycle simulation and the optimum mixing ratio was decided for heating cycle and chilling cycle respectively.

View full abstract

A simulation model for ice-on-coil type ice storage tank was developed. The model, which was originated from the stratified-type thermal storage water tank, consists of a complete mixed region with certain depth and the remained piston flow region with one dimensional diffusion. The effects of existence of coils on the flow and mixing characteristics were considered by introducing two parameters, one is the parameter adjusting complete mixed region depth and the other is the heat transfer coefficient between the coil surface and water. Comparing simulation results and experiments, this model well simulated thermal characteristics of the ice-on-coil type thermal storage tank through identification of these parameters. An estimation table of the ice storage tank efficiency was prepared in order to give a useful information in designing ice storage system. Factors and levels for the design of experiment using the orthogonal tables L_<81>(3^<40>) for the ice storage operation and L_<32>(2^<31>) for ice-water storage operation were decided referring several previous simulations and the results of water thermal storage simulations as well. The simulation results proved the importance of the operation schedule, available limit temperature difference and ice packing factor.

View full abstract

This paper constitutes Part 2 in the series of studies on the ground coupled heat pump system. The objective is to clarify a soil freezing effect to increase in heat extraction rate by means of a filed experiment and numerical calculations. A long time field experiment of heat extraction with soil freezing using a vertical concentric pipe of 20m long was performed. The average heat extraction rate during 120 days was about 28W/m. Heat extraction rate per unit temperature difference between the average pipe surface and the soil at 20m deep was about 2.1W/(m・℃). This value was about twice as much as the value obtained under the condition of unfrozen soil. The result suggested that soil freezing is fairly effective to increase in heat extraction rate. Numerical simulations were carried out by using a three-dimensional model for a vertical pipe based on finite difference equations which was introduced in Part 1. A calculation was arranged to be as similar as possible to the actual experimental conditions. With respect to heat extraction rate and changes of soil temperature distributions, results from simulations were similar to the experimental values. Also, it was shown that the ratio of an amount of latent heat of ice content in soil in comparison with a total amount of heat extraction was 27per cent. Factors of increase in heat extraction rate in the ground soil freezing were examined by numerical calculations. Results showed that a considerable part of increase in a amount of heat extraction was provided with a amount of latent heat of phase change.

View full abstract

The purpose of this study is to investigate the effect of different clothing ensembles on the correlation between SET^* and Japanese thermal sensation, and verify the effectiveness of SET^* as a thermal sensation index. Experiments were conducted in summer and winter under the following conditions. Four different clothing ensembles, including summer and winter clothing, were used in the experiments. The clo values calculated by total weight of the ensemble were 0.56, 0.57, 0.74 and 0.89clo for the male, and 0.42, 0.46, 0.76 and 0.88clo for the female. The air velocity in the test chamber was less than 0.2m/s and the relative humidity was 50%rh. The chamber's surface temperatures were controlled to keep mean radiant temperature equaled to the air temperature ranging from 17 to 31℃. Four male and four female subjects were exposed to 27 different conditions ranging from 16 to 31℃ SET^* for about 1 hour. Metabolic rate on the experimental condition (sedentary and keep quiet) was judged at 0.8met. The main results are shown as follows. 1) In both summer and winter, the significant correlation was found between SET^* and the whole body temperature sensation for each clo values. 2) The seasonal difference and the clothing difference were not found in those regression lines. Therefore, SET^* is useful in predicting the whole body temperature sensation for different clothing ensembles (0.42〜0.89clo). 3) The zone of thermal neutrality with temperature sensation votes ranging from 4: slightly cool to 6: slightly warm was around 22〜26℃ SET^* from total 432 observations. This zone coincided with the comfort range reported in ASHRAE St. 55-74 (22.0〜25.4℃ SET^*). 4) The seasonal difference was found between the whole body temperature sensation and the other sensations (the sense of discomfort and the sense of satisfaction). However, under the thermal neutrality, more than 80% of subjects felt the least uncomfortable and satisfactory.

View full abstract

Excessive growth of filamentous organisms has been reported that it was a cause of sludge bulking in activated sludge system for wastewater treatment and had various living factors in many sides of biological engineering fields and operating fields. In this laboratory scale study, each substrate composition in two kinds of synthetic wastewater was settled, and the ways of water feed into the aeration tanks were practiced in order to find growth and control factors of filamentous organisms. The following aspects could be obtained from the experiment. 1) The SV values (y, ml) and MLSS values (x, g) were observed with time in various modified activated sludge processes. Rearranging these results, the relation was obtained as y=ax+b, a value means average SVI value in each experimental period in about ten days. It was apparent that a value was highest (max, 755ml/g) in the extended aeration process with continuous feed of No. 1 synthetic nutrient water. 2) SVI values showed the tendency to be higher in under 0.06 of F/M value (food to microorganism ratio). 3) The multiple regression analysis was practiced between F/M value and the time to bulking occurrence in various substrates feeding methods to each aeration tank.

View full abstract

In designing thermal storage tank it is important to predict the thermal behavior of storage tank for optimization of its performance. A large scale of temperature staratified storage tank was practicaly applied on cooling and heating energy storage system at a DHC energy plant at Osaka in Japan. The purpose of this study is to optimize the storage performance of this large scale of storage tank. Our study consists of two steps. At the step of designing, authors studied on the effect of some design parameters for thermal storage performance by means of numerical simulation and experimental method. From results of simulation study approximate equations was established to predict the thermal storage performance conveniently. Nextly at the step of operation, vertical and horizontal water temperature profile in the storage tank was measured to confirm predicted storage performance at the step of designing and analyze behavior of water temperature nearby the inlet and outlet opening that had not been generally discussed before.

View full abstract

We conducted experiment to determine the optimal thermal environment for elderly concerning the air velocity in the summer. To determine their comfortable thermal environment the male subjects of youth and elder controlled the air velocity so that they feel thermal environment comfortable. We measured their physiological and psychological responses and compared the results with the past experiments which were done with young and elderly female subjects. We carried out experiments in a climate chamber testing simultaneously two subjects. We set up two fan apparatus which were able to regulate the air velocity. The air temperatures were set at 28, 30, 32℃ for the elderly and 26, 28, 30℃ for the young subjects. The mean radiant temperature was equal to the air temperature. The subjects sat on a chair during the experiments in summer clothes (0.4clo). The subjects regulated the air velocities at will so as to feel comfortable at any time. The number of subjects were 10 active elderly and 8 healthy young men. The main results were as follows: 1) The mean skin temperature became higher as the air temperature rose. In the same air temperature, mean skin temperature of the elderly male was lower than of the young male in 0.3〜0.6℃. 2) Before being exposed to air movement, the higher the air temperature became, the higher the thermal sensation vote. The thermal sensation vote after the exposure of the air movement became cooler by the air movement. But the elderly male's reports differed according to the air temperature. 3) Like the young male, the elderly male didn't change the air velocities so that heat flow rate at the forehead and the thermal sensation vote became the same level. It shows that the elderly's physiological function declined and thermal sensation became more insensible. 4) The average of the preferred air velocities at each air temperature were 0.41m/s at 28℃, 0.80m/s 30℃ and 1.08m/s at 32℃ for the elderly male, and 0.46m/s at 26℃, 0.84m/s at 28℃, and 1.37m/s at 30℃ for the young male. In each air temperature the elderly preferred slower air movement than the young, and as the air temperature rose by 2℃ the air velocities became faster by 0.4〜0.5m/s in each age group. 5) Compared with the elderly female's preferred air velocities of the elderly male were slower. It is considered that daily living customs or consciousnesses influence to the preferred air velocities.

View full abstract

For simulating the HVAC systems and their controls, it is necessary to give a further minute description of building, HVAC equipment and control system on dynamics of HVAC systems. The transition responses in some system components occur relatively slowly and in others occur relatively quickly. This paper presents a dynamic model of a chill water cooling and dehumidifying coil by the state transition method in which time step can be freely selected. Experiments concerning dynamics of coil were carried out to examine the validity and the accuracy of the model. Moreover using the developed program, the effect of each parameter on the capacity of cooling and dehumidifying coil has been analyzed and the dynamics of coil have also been investigated.

View full abstract

In the first report, air flow systems had been evaluated for high heat density equipment room cooling. As a result, underfloor supply overhead return system could remove the heat exhaust from the room most effectively. A mathematical model, named average temperature difference ratio model, was developed to estimate vertical average temperature of inlet air to equipment under the condition of heat generation and air flow. If, in addition to the average temperature difference ratio, its vertical distribution of the inlet air temperature is predicted, equipment can be arranged appropriately in a height direction. In this report, a mathematical model of the vertical distribution of temperature difference was examined and given as an algebraic formula. This model was superior to the numerical analysis in the point of simplicity. An experiment was carried out varying the heat density condition from 640 to 1080W/m^2. The experimental result was compared with a calculation result of the vertical distribution model. When an ingredient of horizontal direction flow is small enough and vertical flow is dominant, a calculation result fairly agreed with the experimental results. It shows that the vertical distribution of temperature difference depends only on the ratio of the equipment inlet flow rate to supply air flow rate.

View full abstract

The temperature selective heat storage tank (TSHST) which was proposed in the previous paper can prevent supplied fluid mixing with stored other temperature layer even if the supplying fluid temperature changes in the thermally stratified stage. The temperature selectivity of the TSHST is affected by components of the sub tank and experimental conditions mutually. It is difficult to clarify these relations through experiments only. The purpose of this paper is to propose the method to predict the temperature distribution change in the main tank of the TSHST. In this paper, the measurement of damper resistance has been performed. Pigeonholing experimental results, coefficient of resistance of damper has been expressed by the function of the aspect ratio and opening angle of damper. The TSHS model considering the damper resistance and the static pressure difference between the main tank and the sub tank has been proposed. The method to calculate the temperature distribution in the main tank has been shown. Calculated results have been compared with experimental results and fairy good agreements are obtained. This calculation method is available for the design of the TSHST and prediction of its temperature characteristics.

View full abstract