Optimization of thermal cooling Parameters applied to rock Storage systems
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Date
2015
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Abstract
This study presents a mathematical model for thermal energy storage in low energy
buildings. The cooling system which uses rock bed for storing night cooling to be
used later for daytime air conditioning is presented. The work initially focuses on the
mathematical descriptions of the thermal cooling applied to rock storage system. A
numerical method of solution is outlined and the results are compared with measured
data at the outlet of the bed both using the measured inlet temperature. A good
agreement of trend is observed. The results show two effects of the cooling system
on the air temperature, which are damping and time delay of the peaking. The
differences are examined through sensitivity analyses for both the convective heat
transfer coefficient and mass flow rate. A parametric study for heat storage with
materials and bed size is given.
A genetic algorithm (GA) is used as a tool to identify the thermal cooling system
parameters related to the mathematical model, including the radius of the sphere
(rocks), mass flow rate, convective heat transfer coefficient and length of the rock
bed. The simulation results have shown an improvement on the performance of the
model with identified parameters compared to the performance before parameter
optimization. In general, the model with optimal parameters has shown robustness to
predict the performance of the cooling system by reducing the input (air) temperature
as much as possible at the time when the temperature is hottest.
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PhD Thesis