Field measurement & verification of residential duct leakage methods and CFD analysis of HVAC mixing box

The research work in this thesis is subdivided to providing the initial results of the experimental work followed by simulation work at the end. The experimental work proposes a new measurement technique for measuring total and local leakages in ducts. The experimental work in this research tries to focus effort on finding the approximate locations of leaks in the HVAC residential duct systems to direct better the effort of duct sealing. This technique can provide several advantages over existing techniques. It will eventually have a greater potential to locate leaks so that retrofitting in ducts can be focused on leaky locations. Field studies were performed in 11 houses in Las Vegas. Out of these, 4 houses were selected for fixing the leakages in them and the tests were repeated on these houses to verify the duct leakage reduction and benefits. The proposed method can offer a more cost effective approach when compared to other methods in the future. It reduces the total leakage for different houses by 14.4% to 46.5% of the total initial leakage rate. The second part of this thesis consists of performing a CFD study of HVAC Mixing box. Return air is supplied from the top of the box and outside air supplied from the back of mixing box. The temperature and velocity profiles of air in the HVAC mixing box were analyzed. The effects of carbon dioxide concentration in the mixing box were also analyzed. The current CFD simulation results were compared to previous field measurements of temperature stratification in a mixing box published in the International Journal of Energy Research in 2001. The CFD results showed that within the experimental error given in the previous paper the CFD temperature distribution predictions were reasonably close to the experimental results indicating that a detailed CFD approach can be used for predictive purposes