Date of Award

Fall 1989

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical Engineering

Committee Director

A. Sidney Roberts, Jr.

Committee Member

S. K. Chaturvedi

Committee Member

Jen-Kuang Huang

Call Number for Print

Special Collections; LD4331.E56O25

Abstract

Heating, Ventilation and Air Conditioning (HVAC) building operations with emphasis on reduced energy costs and occupant comfort require a dynamic control of short response (minutes) elements of HVAC systems. Hence, it is imperative to acquire better methods of non-linear modeling for prescription of thermal controls which will regulate space conditions over wide parameter ranges without undue cycling or steady state errors. A first step towards this goal is identification and inclusion of short response dynamics elements in the HVAC systems model while retaining essential non-linearities. A single zone environmental chamber is modeled in the heating mode. In the model, non­ linear dynamic control of variable air flow rate is central to manipulating the thermal mass of the chamber to delay the requirement for heating. The time dependent energy and mass trans-fer equations were success-fully solved in the time domain using a fourth order Runge-Kutta differential equation solver with variable time step on a microcomputer.

Experiments were performed on an environmental chamber to measure air temperature response, while testing the ability of the system to maintain a set dry bulb temperature during different control scenarios. The results show that, the response of the non-linear feed back system is sensitive to changes in parameter such as heat input, mass flow rate of air, and heat transfer coefficients. For a small change in a parameter, the system response may go from a stable state to a cyclically stable, or even to an unstable state. The model simulation time trajectories captured these controllability characteristics of the thermal room experiment.

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DOI

10.25777/ejnc-dw44

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