English

Knowledge of the authority of control dampers in HVAC systems may be used for diagnostic purposes or to enhance control performance. In this paper, a method of estimating damper authority in air distribution systems is described. The method only requires measurements that are normally available in modem HV AC systems with digital controls. The method is based on a technique that allows the static pressure drop across a branch to be regulated even if that pressure is not measured. Experimental results on a Variable Air Volume (VA V) air handling unit demonstrate the efficacy of the method.

Dynamic simulation of a seawater-cooled chilling system is performed by using the dynamic models of centrifugal chillers, heat exchangers, seawater and chilled water networks, cooling coil, actuator, sensor, variable-speed pump and DDC controller ofBEMS. The on-line control strategies for the central chilling system are tested and evaluated by using them to control the living chilling system under different AHU dynamic loads in four seasons.

Many houses in Japan have crawl space between the lowest floor and the earth ground which is about 50 cm in height. This is considered as protection against corrosion of wood materials in the floor. Japanese building codes recommend ventilation with outdoor air in this space. In our field research, we found condensation in the crawl space in summer. This is due to low temperature of the ground and high humidity of the outdoor air which is typical of the Asian climate.

At present, numerical simulation of room airflows is mainly conducted by either the Computational-Fluid-Dynamics (CFD) method or various zonal/network models. The CFD approach needs a large capacity of computer and a skillful expert. The results obtained with zonal/network models have great uncertainties. This paper proposes a new simplified method to simulate three-dimensional distributions of air velocity, temperature, and contan-finant concentrations in rooms. The method assumes turbulent viscosity to be a function of length-scale and local mean velocity.

The detailed dynamic simulation of coupled units in HVAC-systems and buildings is gaining increasing importance as strong tool in HVAC-engiiieering and operation. This investigation deals with the basics in the development of an universally applicable dynamic simulator. General fundamentals are formulated some moduls are outlined. Shnulation of a heated 4-room-residence, a solar system. and a storage tank as applications demonstrate the mode of functioning and the potential of the simulator.

Recently, a lower type free-access floor system which realizes improved ease of walking and less sense of confinement has been attracting attention. However, it is known that the lower the design of the air supply chamber, the larger the non-uniformity of the diffuser air velocity profile and the greater the deterioration in room temperature distribution. In this paper, an analytical model is proposed for predicting the non-uniformity of diffuser air velocity at the design stage.

Mathematical models have been used by various researchers to provide both a fundamental understanding of indoor air quality dynamics and a platform for estimation of IAQ constituents in lieu of experimental measurements. Due to the diverse nature of these applications the complexity and hence applicability and accuracy of the models varies tremendously. Some models have been specifically developed for evaluation of the impact of a broad range of environmental conditions on IAQ constituents.

In line with its work on the positioning of gas air-conditioning systems in the commercial sector, the Gaz de France Research and Development Division conducted both experimental and theoretical studies. An air-conditioning system, known as the 'reference solution", was installed and equipped in a building on Division premises. The purpose of the system modelling and simulation study was above all to analyse the building's behavior regarding various criteria, while a technico-economic study compared the various (Generation systems.