Design of an Automatic Control Algorithm for Energy-Efficient ...
Design of an Automatic Control Algorithm for Energy-Efficient ...
Design of an Automatic Control Algorithm for Energy-Efficient ...
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3 System description 24<br />
given based on Figure 3.2.<br />
����<br />
�� � � ������ � � ������� � � ����������� (3.14)<br />
����<br />
��<br />
�������<br />
��������<br />
Thermal energy ch<strong>an</strong>ge <strong>of</strong> the windscreen glass [�]<br />
Heat tr<strong>an</strong>sfer rate between the cabin <strong>an</strong>d the windscreen [�]<br />
Heat tr<strong>an</strong>sfer rate between the ambient air <strong>an</strong>d the windscreen [�]<br />
������������ Heat tr<strong>an</strong>sfer caused by other influences like rain or sun [�]<br />
����<br />
�� �<br />
����<br />
��<br />
� ������ ¡ ��� ¡ ��� ¡ ������ ¡ ����<br />
��<br />
������� � ������ ¡ ��� ¡ ��������� ����<br />
�������� � ������� ¡ ��� ¡ ����� ����<br />
�<br />
¡<br />
������ ¡ ��� ¡ ��� ¡ ������<br />
�<br />
������ ¡ ��� ¡ ��������� ������������ ¡ ��� ¡ ����� ����� � �����������<br />
(3.15)<br />
� (3.16)<br />
The temperature <strong>of</strong> the air reaching the middle part <strong>of</strong> the windscreen is lower th<strong>an</strong><br />
at the outlet. This is due to the heat tr<strong>an</strong>sfer to the (here assumed) colder glass. This<br />
will be taken into account with a simple estimation using the already calculated me<strong>an</strong><br />
convection heat tr<strong>an</strong>sfer coefficient at the inner windscreen (equations 3.10 <strong>an</strong>d 3.13) <strong>for</strong><br />
half the windscreen.<br />
�������� � ���<br />
������ ¡ ���<br />
� ¡ ������ ¡ ��������<br />
¡ ���� ���� (3.17)<br />
There are two errors that are made in this equation. ������ is higher in the lower parts<br />
<strong>of</strong> the windscreen due to higher air speeds. On the other h<strong>an</strong>d, the air temperature<br />
difference ���� ���� driving the heat tr<strong>an</strong>sfer diminishes towards the middle. There<strong>for</strong>e,<br />
this estimation should not be used <strong>for</strong> precise calculations but c<strong>an</strong> be integrated into a<br />
controller due to its simplicity.<br />
Now, the windscreen temperature c<strong>an</strong> be written as a function <strong>of</strong> the ambient <strong>an</strong>d