Award Date


Degree Type


Degree Name

Master of Science (MS)


Mechanical Engineering

First Committee Member

Yitung Chen

Number of Pages



This thesis deals with the numerical simulation of the ceiling air distribution (CAD) system and the Under Floor Air Distribution (UFAD) system based on the dimensions of BTLab at UNLV. Ceiling Air Distribution (CAD) with variable air volume (VAV) and Under Floor Air Distribution (UFAD) systems have been widely used in different countries. CAD-VAV and UFAD systems designs have been influenced by increasing emphasis on indoor air quality (IAQ), energy conservation, environmental effects, safety, and economics. So, 3-D Computational Fluid Dynamics (CFD) analysis technique was applied to design high energy efficiency and human comfort CAD-VAV and UFAD systems. The goal of this research project is to analyze energy efficiency with thermal comfort for CAD - VAV and UFAD systems and reduce the design cycle through the development of mathematical and computational models. The University of Nevada Las Vegas (UNLV) has conducted the laboratory phase of this task which was conducted by a different research team by which a test protocol has been developed and implemented in the UNLV Center, the BTLab. This experimental task is to test the performance of UFAD systems compared to CAD systems, including comfort, energy use, indoor air quality IAQ. The experiment has been conducted based on ASHRAE Standard 113-1990 - Method of Testing for Room Air Diffusion. FLUENTRTM 6.2 is a computational fluid dynamics (CFD) software package to simulate fluid flow problems. The general purpose CFD code FLUENTRTM is used as a numerical solver for the present 3D simulation. A non-staggered grid storage scheme is adopted to define the discrete control volumes. The solver used is a segregated solver which is a solution algorithm with which the governing equations are solved sequentially. The SIMPLE algorithm is used to resolve the coupling between pressure and velocity. An implicit technique is used to linearize the discrete and non-linear governing equations. The discretization method used by the FLUENTRTM is FVM in which the space is divided into a finite number of control volumes and solves the partial differential equations. Integration of the governing equations on the individual control volumes constructs algebraic equations for the discrete dependent variables such as velocities, pressure and temperature. In this research work, thermal comfort environment of the CAD & UFAD system is investigated and compared with the experimental values; From the numerical study of the BTLab for CAD system, results show that the temperature and velocity profiles inside the test space are well mixed. Three test planes have been studied to compare these numerical results with the experimental study which show good agreement. The spray angle of the swirl diffuser is considered to be the crucial part and the airflow distribution strongly depends on the spray angle. A Parametric study has been made on the spray angle of the swirl diffuser considering the spray angle from 3° to 7° in which the spray flow for single swirl diffuser is studied. From the velocity and temperature profiles and path lines, the approximated spray angle is around 5.3° which is considered to be a good choice. The UFAD system of BTLab is numerically studied and thermal load is not considered in this study. The results show that the flow from the diffuser is highly helical and twisted and a clean zone is formed as per the previous publication [50]. This shows that the obtained results from the numerical study are reasonable. These numerical results for UFAD system are benchmarked with the experimental results.


Application; CAD; Comfort; Computational; Design; Dynamic; Efficiency; Energy; Fluid; High; Human; Systems; UFAD; VAV

Controlled Subject

Mechanical engineering

File Format


File Size

3072 KB

Degree Grantor

University of Nevada, Las Vegas




If you are the rightful copyright holder of this dissertation or thesis and wish to have the full text removed from Digital Scholarship@UNLV, please submit a request to and include clear identification of the work, preferably with URL.


IN COPYRIGHT. For more information about this rights statement, please visit