The use of natural ventilation systems continues to be a popular feature in low energy, sustainable building design. One feature of natural ventilation is that, depending upon the prevailing climatic or thermal conditions, the airflow through a ventilator can be bi-directional. Aerodynamically, the ventilator, depending upon its construction, may not perform in the same way for the two different flow directions.
The purpose of continuous fan operation is to bring in fresh outdoor air to the conditioned space in order to maintain acceptable indoor air quality. Ventilation not only uses more energy, but it also impacts air distribution system efficiency.This is partially due to various system interactions. The objective of this paper is to quantify the impact of continuous fan operation on energy use and distribution efficiency by introducingtwo new parameters: energy use ratio (EUR) and distribution efficiency ratio (DER).
Fan is a source of noise in ventilation and air conditioning systems. The article provides information about noise emission from different types of fans and the ways to attenuate it, using different types of silencers, including passive and active silencers, or combination of both.
This article describes the physical mechanisms leading to broadband noise from axial fans. It gives the results of a literature survey about the semi-empirical correlations available to predict this noise and their application to two examples : a low pressure fan and a high pressure fan.
A CFD model that incorporates fan-performance characteristics was applied to investigate and compare the air-recirculation performance of the two general designs of unidirectional-flow cleanrooms. For the simulation, typical flow-resistance models of the various components in the air path were used.
The paper describes three methods for determination of the fan energy consumption associated to air filter : the hourly method (calculation of the hourly fan power), the segment method (lifespan filter-associated fan energy), the BIN method (estimation of annual filter-associated fan energy). etailed filter installing date and detailed hourly AHU system simulation.
These methods allow in particular to estimate the filter-associated fan energy consumption and the life-cycle cost of filters.
The main problem in natural ventilation is that its efficiency depends very tightly on the meteorological conditions : high wind velocity and outside temperature lower than inside are optimal conditions for efficient ventilation. Consequently, air renewal inside buildings is very fluctuating from one moment to another, and extreme comportments can be reached from one season to another : in winter, ventilation is usually very satisfying, whereas in summer unwanted reverse airflows can hardly be avoided.