A fundamental study of two-dimensional room ventilation flows under isothermal and non-isothermal conditions
Zhang, Jianshun S.
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https://hdl.handle.net/2142/22133
Description
Title
A fundamental study of two-dimensional room ventilation flows under isothermal and non-isothermal conditions
Author(s)
Zhang, Jianshun S.
Issue Date
1991
Doctoral Committee Chair(s)
Christianson, Leslie L.
Department of Study
Agricultural and Biological Engineering
Discipline
Agricultural Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Agricultural
Engineering, Mechanical
Language
eng
Abstract
Understanding room air distribution is essential to the design of a ventilation system and the control of room thermal and air quality conditions. To investigate the various aspects of room air distribution, a Room Ventilation Simulator was developed with several unique features: an outer room with a HVAC (Heating Ventilating and Air-Conditioning) system to simulate different weather conditions by controlling the ambient air environment around the test room; an inner test room of modular design to facilitate changing room dimensions and configurations; an independent HVAC system for the inner test room to study different air supplies; an air delivery system capable of providing air flow rate of 2 to 52 air changes per hour; a uniform floor heating system of 48 individually controllable panels to simulate internal heat loads; a computer controlled data acquisition and probe positioning system to allow automatic measurements at precisely positioned locations; and a flow visualization system to record room air flow patterns. Additionally, computer software was developed for data analyses.
Detailed spatial distributions of velocities, turbulence intensities, turbulent kinetic energy and temperatures were measured within a full and 1/4th scale test rooms and at the air diffusers. Such detailed data are useful for understanding the room air flow characteristics and for evaluating and improving numerical simulation models of room air motion. Particularly, the effects of diffuser air velocity and internal heat load on the mean and turbulent characteristics of the room air flows were analyzed using the full scale data.
Scaling methods for predicting room air motion were investigated theoretically and experimentally. For non-isothermal room air flows, the critical Archimedes number, at which the diffuser air jet fell immediately after entering the room, decreased when the room dimensions decreased. A new scaling method was proposed based on the relative deviation of Archimedes number from its critical value. Comparison between the full and 1/4th scale tests indicated that the new method has improvements over previous ones.
Additionally, the uncertainty of a hot wire anemometer and its capability of resolving velocity components in low velocity measurements ($<$50 ft/min or 0.25 m/s) were quantified.
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