temperature stratification

The impinging jet ventilation (IJV) system has been proposed as a new air distribution strategy and is expected to overcome the disadvantages of the mixing ventilation system (MV), which is the most widely used system, and displacement ventilation, which provides better air quality than MV.  

The impinging jet ventilation system (hereinafter referred to as IJV) has been proposed as a new air conditioning ventilation system. Properties of indoor environment with this system using impinging jet are complicated. The present paper reports fundamental properties of indoor air with distributed interior heat generation load assuming an office. The experiment was conducted in the climate chamber of which floor area was 27.0 m2, and basic properties of temperature and CO2 distributions were investigated.

Describes a study based on experimental work carried out in the full-size MiniBat experimental cell, comprising two zones separated by a wall and a door. Experiments were carried out in a steady state, under isothermal and non-isothermal conditions, with a heating system and a manikin. To determine ventilation effectiveness the tracer gas method was used. It was injected into zone 1 and two positions were examined. The study concluded that the heating system favoured the mixing of the air in the cell, which means that the ventilation effectiveness was always close to one.

19 university students were asked about their thermal comfort while attending ordinary lessons in a displacement ventilated test room of typical classroom size. Two different ceiling heights were tested. Both the general temperature level and the strength of the vertical temperature stratification in the room increased continuously during the lessons due to the presence of the students, however slower with the higher ceiling.

A set of formulae for natural ventilation by thermal buoyancy is derived for a room with two opening and with a linear temperature stratification. The formulae are based on the fundamental flow equations, and they cover air velocities, temperature differences and ventilation rates in relation to opening areas, opening position, net heat input, building geometry, and temperature stratification. The temperature stratification can simply be taken into account by introducing a stratification factor E and by using the mean difference between indoor and outdoor temperatures.

Information on thermal plume characteristics is essential for designing ventilation systems with displacement air supply. Empirical, analytical and computational fluid dynamics are the commonly used approaches to evaluate air temperatures, velocities and airflow rates in thermal plumes above different heat sources. However, only limited information is available on the behavior of thermal plumes in rooms with a temperature gradient along the room height.