Cooling and ventilation of office spaces by displacement ventilation and chilled
ceiling panel systems is potentially more energy efficient than conventional air
conditioning systems. Heat transfer in this type of system is characterised by
the presence of vertical temperature gradients and significant radiant asymmetry.
The room heat transfer models used in current building simulation methods do
not allow adequate representation of this type of system due to their reliance on
a single node to define the internal air temperature. The overall aim of the work
described in the thesis has been to develop a model of this type of system that
is suitable for use in annual building energy simulation. The model presented,
is intermediate in complexity between a CFD numerical model and the current
single air node models, having ten air nodes.
The operating characteristics of displacement ventilation systems, used both with
and without chilled ceiling panels, have been studied by making experimental
measurements in a test chamber and by reference to published experimental data.
Numerical calculations of the flow and temperature fields have been made with
a coupled flow and radiant exchange CFD code. Steady state calculations have
been made of displacement ventilation using a conjugate heat transfer method.
Interesting oscillations in the flow and temperature field of displacement ventilation
operating with a chilled ceiling have been found through adopting a fully
transient calculation procedure.
The thesis describes how the experimental and numerical data has been used to
develop the structure and define the parameters of a simplified nodal model. The
logical development of the model structure, from the most elementary model to one
which is able to capture the effects of the temperature gradients and incomp1ete
mixing of the air in the room is described. A method is also presented whereby
the parameters of the model are found directly from the experimental data by
solving the heat and mass balance equations of the nodal model. The parameters
of the model have been generalised by analysing these calculations and by making
use of established convection coefficient correlations.
The performance of the model is demonstrated by firstly making comparisons of
the experimental and numerical data under steady state conditions, and also by
demonstrating that the model is able to reproduce the characteristics of displacement
ventilation and chilled ceiling systems under different operating conditions.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University. firstname.lastname@example.org