Master's Thesis Ana de la Pena

Coupled analysis of a layered storage

Thermal stratification in hot water storage tanks is analyzed in this thesis. These tanks play a central
role in thermal heating systems, reason why the analysis of their thermal behavior can be a first step
in order to improve the global efficiency of a thermal system.
In order to analyze thermal stratification inside a water storage tank of 500 liters of capacity, two
different sorts of experiments are carried out so that a complete analysis of the thermal behavior is
achieved. After specifying the requirements of the experiment (i.e. selecting the suitable materials
and equipment), a setup is displayed in order to proceed with the tests, which is chosen accordingly
with the already existing literature. With this setup, which includes the design of a temperature
measuring device, its construction and the calibration of the instruments, specific cases of
study are carried out in where temperature’s measurements are taken as a function of time. These
cases are focused in how the water’s temperature develops through time, either in vertical and in
radial direction, and how the assembly of the temperature measuring device can influence the thermal
stratification. The measurements are taken consistently with the cases described and, after the
gathering of data, the results are presented and validated.
It is concluded that thermal stratification takes place in both vertical and radial direction. A maximum
difference of 23 C can be observed inside the tank in the vertical direction, while in the radial
direction the difference of temperature is less than 1 C. The results also show that different facts influence
to a greater or lesser extent the thermal stratification of the water inside the tank: the use of
the insulation in the tank is a determining factor in how temperatures progress through time, while
the use of the insulation on the pipes may have a significant effect. The influence that the assembly
of the temperature measuring device inside the tank could have on thermal stratification is also
analyzed.