Description
In jet fan tunnel ventilation applications, a degree of uncertainty has arisen with regards to the definition of the fundamental operating parameters such as installed thrust, momentum transfer, pressure distribution, efficiency and even the mathematical basis for an application. It’s believed that a lack of detailed provision of all the force components in an application, can potentially lead to misunderstandings, as a complete mathematical verification of the design remains inaccessible.
This work provides a comprehensive categorisation of all force, momentum and pressure components in a jet fan tunnel ventilation arrangement, demonstrating the origin of the most prominent to the least significant forces in the system. Additionally, momentum and pressure distributions along the tunnel are charted, providing an understanding of the exchange between these parameters and a wholistic verification of the physics/mathematical basis of the application.
Project experience is drawn on, for an undulating tunnel wall shape design, with impacts on force balances, momentum exchange and tunnel pressure distributions explored and presented. A verification methodology for jet fan in tunnel operation, based on the application of Newton’s 2nd and 3rd laws on a thermo-mechanical Open System is proposed, providing a comprehensive and accurate assessment of the balances of all forces and momentums at the system boundaries. The results for a 250N and a 526N ceiling fan tunnel installation, demonstrated a high degree of accuracy in the force-momentum balance (less than 0.2% imbalance for the Open System), giving confidence to the proposed methodology.
