English

A specific type of centrifugal fan named the "squirrel-cage" is broadly used in parallel configurations within an evaporator unit of HVAC systems for public transport. In these units, interaction effects arise, both between fans themselves and between fans and the structural elements. Blockage effects, such as the electrical motor, the evaporator gate and some aesthetic covering may also appear when these external elements are located very close to the fans aspiration nozzles.

The air tightness of ventilation ductwork was measured in two recently built low-energy houses and in two conventionally built houses in the summer of 2013. The ducts and components were metal in three houses and plastic in one house. The air tightness of the ductwork had been checked by an installation survey after construction. The measured leakage airflows corresponded to air tightness class A or lower, therefore did not satisfy the minimum requirement set for class B regarding the air tightness of ventilation ductwork.

This paper presents results from an on-going project concerning new design procedures for mechanical ventilation systems with low energy use. Conventional constant air volume (CAV) systems are usually balanced using flat plate dampers. The purpose of using balancing dampers is to intentionally introduce pressure drops in the duct system thus nominal airflows are achieved throughout the ductwork within specified tolerances.

Very often the set point temperature is selected to satisfy comfort requirements and/or to save energy consumption in buildings. However, the thermostat location is usually outside the occupied space and located on the wall near a front door or in a hallway that is subject to warm and cold draughts. A discrepancy exists between the temperature at the thermostat location and the occupied zones.

A turbulent jet is the most important flow element in mechanical ventilation. Mixing ventilation is based on the properties of turbulent jets. By entrainment into the jet the ambient air is set into motion. For a jet supplied within a room the enclosure may affect the jet in several ways, through:

This paper describes the effect of outward opening the sash of a window on local and overall wind pressures. Wind tunnel experiments were used for the purpose of evaluation. A centre-pivot roof window on a pitched roof in a modelled scaled building was used in the analysis of wind pressures. The wind pressures were defined in terms of wind pressure coefficients. Traditionally, wind pressure coefficients are extracted from the analysis of a sealed plane surface. These wind pressure coefficients are used to estimate the natural ventilation rate through windows/openings due to wind effect.

As natural wind is continuously fluctuating in both speed and direction, quantifying instantaneous wind-driven natural ventilation rate can be difficult, and often an average effect is used to stabilize the fluctuations. This work performs an experimental investigation to assess the validity of assumptions often used in quantifying airflows through an opening under cross natural ventilation condition. In the experiment, the three velocity components are analyzed for flows approaching and through an open window exposed to natural wind.

Air quality in a classroom is very important. According to a study by Wargocki et al (2012) a shortage of ventilation in the classroom reduces the ability of students to concentrate and causes an increase in the number of errors during the elaboration of tasks. The aim of this study was to contribute to the optimization of acquisition and operating costs of HVAC equipment and to ensure hygienic requirements of air quality in the indoor environment for classrooms.

Air change rate is often used as an important characteristic of indoor environmental quality, which significantly impacts human health. However, easy, effective, real-time and low-cost air change rate measurements in naturally ventilated resident buildings are still a huge challenge. This paper presents a method based on the release of a stable rate of the tracer gas CO2 given off by solid CO2 (dry ice) in an insulated box.  In theory, the dry ice will sublime at a constant rate as long as there is sufficient dry ice in the box.

In typical Chinese commercial kitchens, the large amount of heat and moisture that is generated must be removed. The ventilation and energy consumption rates can be huge. Middle and small scale commercial kitchens in China produce an exhaust airflow rate so large that without a reasonably effective ventilation system, the temperature and contaminant concentrations are far more than acceptable levels. To fulfil all the requirements of indoor air conditioning in an economical manner, a new air distribution pattern called air curtain ventilation (ACV) is presented in this study.