Control items and adaptability to hardwares and the effect of them are discussed at first in order to raise the quality of Air-conditioning and air-conditioning system. Among the optimizations applied to Osaka Ohbayashi Building which were described in the former report, outside air intake and environmental analysis, delivered air temperature reset from air-conditioners, and pre-heating and -cooling are handled in this report, which belong to air-conditioning main system in the total structure. Significance, softwares and actual results are shown in each of these. Prediction techniques used in this part are extrapolation, exponential smoothing and learning factor method which were described in Part 1. Penalty function is important to increase rapid conformity, and therefore introduced to each software. The effectiveness and adaptability of optimization to these subsystems are made sure through actual results on environmental indices.

View full abstract

Optimization of Thermal Storage Operation and Selection of Heat Source are reported. Thermal storage system is the most difficult subsystem to operate and control in accordance with the design philosophy, while this subsystem governs energy conservation and effective use of energy source. Temperature profiles are the most convenient and meaningful measures to design and control the thermal storage. Thus, temperature profiles are used to predict the state of storage, and they are predicted via the prediction of heat load. Heat load is to be estimated and predicted using Kalman filter on day-base as well as time-base, which is quite useful to apply for instationary and nonergodic systems. Results are shown with actual data to evaluate the effectiveness of this optimization methodology. Co-relation between heat load and outside-air-temperature and/or solar insolation are also described.

View full abstract

Optimization of Heat Recovery and Efficiency of Heat Source Machines are reported. The latter is subdivided into surging protection routine, outlet temperature reset and water delivery temperature reset to fancoil-units. The significance, software and the actual results for each are described. In heat recovery optimization, heat load prediction by Kalman Filter is also used as described in the former report. Objective function for this routine is heat balance between hot and cold, while the coefficient of performance for the system combining the heat pump, pump power and storage loss is adopted as that for outlet temperature reset routine. In addition to above-mentioned routine, pump number control sequence and efficiency control for total heat exchanger are described. Then the author has almost finished to report the total figure of optimalizing control concept, hardware and softwares of Osaka Ohbayashi Building. Finally, in order to show the effectiveness of the control, author shows the results of energy consumption, performance of heat-pump and coefficient of energy consumption for air-conditioning, which author think is most important for this kind of practical research and development.

View full abstract

In designing ventilation systems for high-temperature plants, some methods based on the assumption that the indoor temperature is uniformly distributed are already established. The temperature gradient there, however, is steeper than in a heated building generally found in commercial or residential areas. For this reason, the present paper describes the scale model studies of mechanical ventilation carried out to develop a new method taking full advantage of the temperature distribution The temperature gradient was far more marked vertically than forizontally, forming a temperature stratification. The temperature stratification was mathematically expressed with the temperature difference ratio which was found to depend on the ratio of the volume of ventilation to surplus heat. The experimental equation of the temperature difference ratio led to a new method for calculating the necessary rate of ventilation which takes into account the full effect of the temperature stratification.

View full abstract

The efficiency-reduced temperature (η-T^*) curve of the tested collector unit, which was composed of evacuated glass tubes of 100mm outer-diameter and flat-tube absorbers coated with selective surface, was described by η=0.94-0.22T^*-0.01T^<*2>, where T^* means U_0(T_m-T_a)/I, T_m being average temperature of heat transfer fluid in the collector, T_a: ambient temperature, I: solar insolation, and U_0: nondimensionalizing coefficient of 10W/m・℃. The test was conducted by GIRI Nagoya procedure which was slightly modified from NBS/ASHRAE procedures. The η intercept (η_0) of 0.94 was larger than the calculated value, (0.78), based upon transmittance of the glass tube and solar absorptance of the absorber plate. The absorption of solar radiation reflected by the ground surface behind the absorber plate and also the absorption of diffuse solar radiation from the sky behind it caused the increment of about 0.12 from the calculated η_0 value of 0.78. The deviation of each (η-T^*) datum from its performance curve was relatively small compared with those of flat plate single and/or double glazing collectors, because the effect of changes of environmental conditions such as wind speed, ambient temperature, and incident solar radiation on the efficiency of collector at a fixed T^* value was relatively small as predicted by the heat transfer calculation applied to simple model of tubular collector under the ad hoc assumptions. For instance, the change of climatic conditions ranged from (v=1m/s, T_a=20℃, I=850W/m^2) to (v=3, T_a=30, I=950) caused an efficiency variation by only 0.015 at T^*=0.7 for the evacuated collector. The obtained value of global heat loss coefficient (2.2+0.1T^*) represented the effect of evacuation and selective surface of the tested collector. This small coefficient might cause the difficulty of precise direct measurement of heat losses from the collector for some ranges of (T_m-T_a) under no incidence of solar radiation due to the limitation of precision of the thermopile used for the measurement of the fluid temperature difference between collector inlet and outlet. In the direct heat losses measurements under no incidence of solar radiation, heat is transfered from the fluid in tube to the plate, while heat is transfered reversely in the efficiency measurement under the proper incidence of solar radiation. Therefore, the absorber plate temperature is different between both cases even at the same T_m. This difference of plate temperature causes the variation of the heat loss coefficient of the collector especially in present case. The caution should be taken account in application of the testing procedure like BSE, in which the η_0-T^* relation is constructed by directly measured η_0 value and the global heat loss coefficient determined by the direct heat losses measurements.

View full abstract

For the purpose of adjusting a flow rate in piping systems, the valves are widely used in industry, none the less for undesirable energy losses due to flow contraction. The valve is a sort of devices that forces fluid flow to contract and to enlarge in a pipe, and an orifice is a typical example of it. In such a device, fluid flow exhibits various phenomena, such as separation, contraction and expansion, and if its sectional area ratio of orifice to pipe is small, the injurious effects of cavitation, i.e. noise, vibration and increasing head loss, will be induced. There are a large number of papers on cavitation in valves and orifices, where the cavitation numbers are defined differently by various researchers. However, there are very few attempts to generalize the conditions of cavitation occurring in valves and orifices which have similar flow and cavitation conditions. An analogy can be found between the phenomena of cavitation occurring in such devices, on the basis of experimental results on the most standard ones, namely sharp-edged and cylindrical orifices. On a simple assumption, the critical condition of cavitation occurrence in such ones can be well prescribed universally by the cavitation number which is determined with the static pressure and velocity head upstream of those devices. Furthermore, based on experimental data of not only these orifices but also two-dimensional gate and butterfly valves, it is concluded that an empirical equation on desinent cavitation number is well expressed with area ratio and contraction coefficient which is calculated from two-dimensional potential theory with free stream line.

View full abstract

The dividing flow mechanisms in pipe junctions were investigated systematically. The Navier-Stokes equations describing the laminar flow field in the two-dimensional pipe junctions were solved numerically. The flow field in the real pipe junctions were studied experimentally by means of a flow visualization technique. The flow mechanisms in the pipe junctions were considered theoretically and experimentally.

View full abstract

There are a few papers reported about the high rate of heat transfer at the point of a water jet impingement. The value of the coefficient "h" of heat transfer decreases with a radius increasing steeply. And the effective cooling radius is not limitted definitely. For the application of water jet cooling to a flat plate, it is necessary to know the distribution function of "h" on the plate and the effective cooling area. The local values of "h" were measured in this experiment, in which the vertical circular water jet impinges against the horizontal plane. And a theoretical equations about "h" and the radius of the effective cooling area were obtained by the "apporoximate method of Karman-Pohlhausen". The comparison with equation of "h" and experimental data had a good agreement. For the convenience of cooling design, the relation between optimum water flow rate and nozzle pressure to give the proposed heat removal was discussed.

View full abstract

A study of cooling by a single water jet impinged on the horizontal flat plate had reported in the previous paper. In this paper, the mean coefficient of heat transfer between 9 jets, which were held in square array, and the surface of plate are measured in wide range. The radius (γ_j) of the hydraulic jump and the thickness (δ_<m2>) of water film were measured, and observed that the former became smaller and the latter varied thicker with respect to the reduction of nozzle distances respectively. The experimental formulae about γ_j, δ_<m2> were obtained by the data above mentioned. The mean coefficient of heat transfer of single jet based upon square area of plate was computed by the theoretical treatment. It was found that the theoretical equation of heat transfer rate about the single nozzle could be applied to the case of multi jets. Furthermore, the jet was impinged against the limitted area constrained by dikes, which was considered as if the simulation instead of actual multi nozzles experiments. The value of heat transfer rate and the radius of jump in this experiment so-called "simulation" were coincided with the data of the actual multi jets.

View full abstract

While a computer simulation is the most accurate method in estimating annual space heating load, the simulation programs require large computers usually which can not be used practically in designing a residential house, and the detailed informations of the house must be prepared to run the program. A simplified method is still attractive for the easiness. Insulation and other energy saving technics can be examined with easy hand calculation in early stage of the design. Heating degree days method widely used often overestimates the annual heating load, since the heating effects of the solar radiation and the internal heat sources such as lightings and refrigirators and other appliances are not properly considered. The method described in this paper is based on the steady state heat balance of a heating season, in which these heating effects are considered. In order to examine the assumptions of the steady state heat balance equation, unsteady state heat loads were simulated for 17 models with three kinds of houses insulated with two or three ways for three climatic conditions, i.e. Sapporo, Tokyo, Kagoshima. As the comparison between the simulated loads and the loads calculated by simplified method showed good agreements, it was found that the steady state equation could be used as the basic equation for the simplified calculation of annual heating load. The average room temperature of a heating season which is necessary in the heat balance equation is uncertain in the simplified calculation, so that the correction factor modify the temperature difference of the average room temperature and the average outdoor air temperature was introduced in the basic equation. Using the experimental design method, a set of 81 combinations of the factors affecting the heating load was made for the simulations of the heating load in order to examine the characteristics of the correction factor. The equation obtainning the correction factor was fitted with the parameters selected by analyzing the results of the simulations, and with the fitted equation the charts finding the correction factor were made for practical use. Accuracy of the simplified method was examined and it was concluded that with the simplified method the annual heating load can be calculated easily within the allowable range of errors.

View full abstract