Generally, in a large space, a nozzle-type outlet is used as the outlet of an air-conditioning unit. However, most of the air flow from the outlet is dispersed and lost before reaching the target point. The air flow that the target point is only a part of the original. Moreover, in terms of heat-transport as well as airflow, cold air or warm air will diffuse before reaching the target point. Therefore, only some cold air or warm air can reach the target point. On the other hand, a vortex ring has high mass and momentum transporting capability. The compact and unchanged characteristic of vortex rings is suitable for obtaining high-density distribution of the transported fluid within a specific confined region. In this study, the aim was to produce vortex rings continuously, and apply them to an air mass utilizing their high heat-transport capacity to realize ductless ceiling-air-conditioning in a large space. We describe the behavior of a series of vortex rings showing how they behave compared to single vortex rings. The examination was performed by using computational fluid dynamics (CFD). In the study, the jetting speed and the volume of one shot were used as parameters. Accordingly, we found the following. 1) When the vortex rings are repeatedly produced, the arrival distance of the second and subsequent vortex rings become short. Therefore, it is necessary to devise for extending the range of a vortex ring. 2) Increasing the jet velocity tends to increase the reaching range of the vortex rings and the heat-transport range. 3) When the jet velocity increases, the turbulence on the transfer course of vortex rings becomes strong, and the vortex ring cannot maintain a stable state. 4) Even if the volume of jet in each time is reduced and the frequency of vortex ring generation is increased, the reaching range of the vortex ring and the heat-transport range scarcely change. 5) If the volume of jet in each time is reduced, the trailing surplus air decreases and the behavior of vortex rings becomes stable.
This study discusses the influence of primary equipment load setting on the estimated HVAC energy consumption in building energy management by using system simulation. In this study, two real existing government office buildings were chosen for the examination. Some procedures for the simulation modeling of air-side HVAC system in the design phase were examined to estimate the energy consumption of primary equipment. As a result, it was confirmed that there was not much difference in the estimated energy consumption between the case where all actual equipment specifications were modeled and the case where the air handling unit was modeled based on the floor number mean maximum heat load. This paper proposes the points of attention that need to be considered in the operational phase and recommends a methodology for the utilization of the measured operational data as simulation boundary conditions for estimating the energy consumption. These are widely applicable methods for the energy management of HVAC systems.
In this study, the sensitivity analysis of observation error on the estimation accuracy of data assimilation was conducted. The analysis focused on the estimation of unknown contaminant source distribution in an indoor environment, and was conducted through a numerical experiment. In the experiment, some data assimilations were applied with pseudo observation data with several sizes of observation errors, which follow the normal distribution. The assimilation results were compared to evaluate the impact of observation errors on the estimation accuracy. The results of numerical experiments indicated that observation errors cause a decrease in the accuracy of estimation, and an increases in the deviation of the accuracy. The impact of observation errors increased with decreasing spatial and temporal resolution of the observation data.