English

The characteristics of a hybrid air-conditioning system, utilizing natural and mechanical ventilation, is investigated in an office setting. The characteristics of the indoor environment are examined with CFD(Computational fluid Dynamics) simulation under various conditions of incoming outdoor air. The control of the room air conditioning system (VAY system) is included in the calculation through changing the supply air volume to keep the task zone's temperature at a target temperature.

An isothermal air curtain for isolation of smoking areas in restaurants was designed, built and evaluated in a test facility using oil-smoke visualisation and tracer measurements. The test facility was a ventilation test room set up as a small restaurant, with tables, chairs, person simulators (cylindrical heat sources) and balanced mechanical ventilation. Fresh air was supplied in the non-smoking section of the room, exhaust air drawn from the smoking area, and the air curtain was attached to the ceiling between the two sections.

A three dimensional computational fluid dynamics (CFO) analysis has been used to predict airflow patterns in laboratory fume hoods. The simulation includes bypass fume hood primary operational features including the top and bottom bypasses, front airfoils, and rear slotted baffles. The study included the effects on the fume hood airflow of sash height changes, an operator positioned outside the fume hood, and equipment within the main fume hood chamber.

In many buildings, for instance tunnels, underground, parking areas and industrial halls, the L/H is so large that the flow pattern induced by a two dimensional supply air jet along the ceiling can be completely different from that in rooms of normal sizes. Earlier model experiments indicate that, in this case, the supply jet will have a limited penetration length (Ire) because the entrainment generates a backward flow in the lower part of the ventilated space which at a given distance will disperse or deflect the jet.

A study is being conducted to assess the performance of displacement ventilation in high-ceiling areas such as commercial and industrial manufacturing facilities. These areas, which can range from 5 to 20 meters in height, often feature high internal heat loads and contaminants associated with heat sources. Very little performance data exists for displacement ventilation installations in high-ceiling areas, particularly any which account for the influence of wall temperature.

The paper presents a comparison between the results of experimental tests airflow pattern forming in a room with displacement ventilation and numerical calculation. The heat source in the room was a heating plate. Quasi-laminar diffusers supplied the air with the ventilation change rate from l to 7 h-1. Temperature and velocity distributions in the plume and in its surroundings as well as the tracer gas concentrations in the background were measured. The airflow in the room was also predicted by means of CFD, using the standard k-E turbulence model and standard log-law wall-functions.

Two-dimensional computational simulations are performed to examine the effect of vertical location of a convective heat source on thermal displacement ventilation systems. In this study, a heat source is modeled with seven different heights from the floor (0.5m, 0.75m, 1.0m, 1.25m, 1.5m, 1.75m, 2.0m) in a displacement ventilation environment. The flow and temperature fields in thermal displacement ventilation systems vary depending on the location of the heat source. As a heat source rises, the convective heat gain from the heat source to an occupied zone becomes less significant.

In the modem office environment there are numerous heat generating equipment. In addition there are loads from solar radiation and heat produced by people. Therefore, the loads will often exceed.the load the ventilation system can cope with. To meet this demand on extra cooling capacity the commercial market provides cooling ceiling panels and cooling beams. A literature review shows that until now the majority of the research has been focused on the cooling performance and only a minor part on the thermal comfort and air quality.

The thermal dynamic behaviour of buildings is solved by different methods; one of them is based on simulation by means of thermal node models. Computed results of the internal air temperature or the surface temperature are influenced by the used method, by the model for a solved problem situation, and by input values of model elements. The influence of the particular model element can be found by means of a sensitivity analysis.

Cooling ceiling systems are controlling only the sensible heat balance of the rooms; they are always combined with a ventilation system foreseen to control indoor humidity and to cover air renewal requirements. Between the types of cooling ceiling in use, the passive chilled beams seem to be the most sensitive to ventilation air influence. Jn most of the cases, the ventilation outlets are located in the ceiling void, and consequently this generates a penalty on the beam cooling power. The work presented aims at estimating this influence, through results issued from experimental studies.