English

Ventilation effectiveness is an important means to describe and evaluate the performance of a ventilation system. In terms of ventilation tasks, this paper presents a unified physical model for the ventilation efficiency scales based on conservation principles to which a ventilation system should conform. Transport equations for the local mean age of air and contaminant are respectively obtained, which can be integrated solved by the CFD program. To validate the proposed model and CFD simulation of the ventilation efficiency, a 2-D laminar ventilation flow is analysed.

On the bases of the definitions of air conditioning period, dehumidifying period and heating period, this paper puts forward to the exchanging conditions and psychometric process of ventilation system in residences. In order to improve on thermal environment quality and indoor air quality (IAQ), new strategies must be found to control both temperature and humidity of ventilation system.

This paper founds the procedures of standard summer meteorological parameters in hot summer and cold winter region, determines the hourly meteorological model of dry and wet temperature change for sunny days, cloudy and rainy days, and builds up Chongqing's standard summer meteorological parameter database. Then based on hourly-degree method, this paper also analyses the ventilation cooling loads with new concepts such as ventilation cooling load index (VCLI), ventilation cooling temperature degree hour (CDH), cooling wetness hour (CWH0 and cooling enthalpy hour (CEH_.

In accordance with the regular and irregular variation principle of high-rise building wind pressure with the variation of time, wind direction proposed in associated reference and high-rise building around flow aerodynamic characteristic. An analysis is made about the characteristic and range in which wind pressure on high-rise building changes largely with coming flow, time and wind direction in the paper. On this base, this paper points out that building heat load and air infiltration rate is unstable and has large fluctuation in certain period.

Thermal comfort field studies were conducted in three different sessions (morning, afternoon and night) of the day to evaluate the actual thermal comfort perception of the occupants. Direct and indirect assessment of the thermal acceptability were performed to investigate whether the naturally ventilated indoor environment meet the ASHRAE Standard-55's 80% acceptability criteria. Comparison of thermal sensation and thermal comfort votes revealed that a high proportion of people experiencing sensations of +2, +3 still found the conditions to be comfortable.

A one-dimensional unsteady flow model with a moving pollutant source is used for calculating airflow velocity and pollutant distribution inside the single-track railway tunnel when a train passes through it. Calculations are made about the distribution of pollutant concentration inside the tunnel when a train passes through it under the conditions of different tunnel lengths, different amount of pollutant emissions, etc.

The substance of AC fresh air control is that fully utilises outdoor fresh air according to enthalpy of outdoor air, so achieves the goal of energy saving and improving indoor quality. The normal way is adjusting the amount of fresh air according to enthalpy which is calculated on the basis of temperature and humidity in and out door, this is called "enthalpy control". But because the cost of humidity sensor cell is high, its life is short, and it is very difficult to maintain, the long time and reliably running control systems are actually very short.

A numerical study was carried out to gain an understanding of the ventilation performance of solar chimneys with uniform heat flux from both walls. Results showed that a currently available predication method, which has been validated with narrow chimneys, may not be suitable for wide chimneys. It was also shown that for geometrically similar chimneys, the ventilation flow rate, Q, increases with the solar radiation intensity, q, and the chimney height, H, and can be well correlated by Q q1/3H4/3 regardless of height/gap ratio and the occurrence of reverse flows.

The aim of this paper is to verify the applicability of coupling thermal and multizonal simulation codes to the study of hybrid ventilated buildings. One of the main problems in hybrid ventilation building design is the evaluation of ventilation control strategies. This point has rarely been adequately developed during design phase by means of dynamic simulations analysis; often actually an insufficient analysis of control strategies it has revealed to be the first cause of complaints from the occupants. This paper aims at demonstrating a satisfactory solution of this problem.

Based on measured wall temperatures made by an infrared camera the flow and temperature fields were computed for an atrium. The nature of this atrium is a large enclosure inside a school building surrounded by halls and classrooms. Within a hybrid ventilation concept the stack effect during the summer time is used to form the main driving force for the night cooling of the classrooms. Time dependant computations were carried out to obtain the flow and temperature fields inside the atrium under various boundary conditions.