A Modified T-Method Simulation for Multi-fan Duct Systems
AbstractIn this study, we introduce the Modified T-Method which can be applied to the prediction of the flow distribution in multi-fan duct systems. Introduction of individual flow routes enables the division of a complicated multi-fan ductwork into a set of simultaneous single-fan subsystems. The present method was tested on the single-fan duct system presented in the ASHRAE handbook. The test system consisted of several branches and a fan. Our results showed good agreement with those published. Also, we tried another approach, in which the symmetry of a two-fan duct system was investigated. Verification was accomplished successfully by the analysis of a two-fan duct system that yielded physical consistency. In order to evaluate the utility and capability of the title method, a bathroom ventilation system in a 20-storey residential building was selected as an example of an application. Under the typical design conditions, the air flow rate of each exhaust fan at the balance point was predicted successfully and it was shown that such information can lead to an engineering estimate for the system performance as a whole. While some deficiencies in ventilation were found in bathrooms on the lower floors with 6mmAq-rated exhaust fans, they disappeared over the building as a whole by using fans of enhanced static pressures, 7 and 8mmAq. Finally, the work has demonstrated that this method is likely to be useful for the design of multi-fan duct systems.