Faults that develop in the heat exchanger subsystems in air-conditioning installations
can lead to increased energy costs and jeopardise thermal comfort. The
sensor and control signals associated with these systems contain potentially valuable
information about the condition of the system, and energy management and
control systems are able to monitor and store these signals. In practice, the only
checks made are to verify set-points are being maintained and that certain critical
variables remain within predetermined limits. This approach may allow the detection
of certain abrupt or catastrophic faults, but degradation faults often remain
undetected until their effects become quite severe.
This thesis investigates the appropriateness of using mathematical models to track
the development of degradation faults. An approach is developed, which is based
on the use of analytical models in conjunction with a recursive parameter estimation
algorithm. A subset of the parameters of the models, which are closely related
to faults, is estimated recursively. Significant deviations in the values of the estimated
parameters from nominal values, which represent `correct operation', are
used as an indication that the system has developed a fault. The extent of the
deviation from the nominal values is used as an estimate of the degree of fault.
This thesis develops the theory and examines the robustness of the parameter
estimator using simulation-based testing. Results are also presented from testing
the fault detection and diagnosis scheme with data obtained from a simulated
air-conditioning system and from a full size test installation.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.