| An antifreeze
solution circulates through the collector, and a
heat exchanger transfers the heat from the
antifreeze solution to the tank water. When toxic
heat exchange fluids are used, a double-walled
exchanger is required. Generally, if the heat
exchanger is installed in the storage tank, it
should be in the lower half of the tank.
The system
illustrated in Figure 3 is an example of this system
type. Here a heat transfer solution is pumped
through the collector in a closed loop. The loop
includes the collector, connecting piping, the pump,
an expansion tank and a heat exchanger. A heat
exchanger coil in the lower half of the storage tank
transfers heat from the heat transfer solution to
the potable water in the solar storage tank. An
alternative of this design is to wrap the heat
exchanger around the tank. This keeps it from
contact with potable water.
The brain of the system is a differential
controller. In conjunction with collector and tank
temperature sensors, the controller determines when
the pump should be activated to direct the heat
transfer fluid through the collector.
The fluid used in this system is a mixture of
distilled water and antifreeze similar to that used
in automobiles. This type of fluid freezes only at
extremely low temperatures so the system is
protected from damage caused by severe cold. |
Saturday July 05, 2008 - 12:46 PM
