Entirely passive solar air heater with water heat store and heat exchanger of automobile radiators
The automobile radiators are protected from night freezing by being
enclosed in a heat trap -- an insulated space open only
below.
Efficient heat collection requires a significant fall in
the temperature of the air as it passes through the radiator, since
this temperature fall drives the air flow. It is important to use
the necessary heat losses through the outer glazing to cool only the
falling air, as shown. The inner glazing maximizes the chimney effect
and eliminates mixing of falling and rising air. In order for the
automobile radiator to cool the air sufficiently for good air flow when
the output water from the radiators is warm, there would have to
be a substantial rise in the temperature of the water as it rises
through the radiator, so that at least part of the radiator is
cool. This requirement for a substantial temperature rise means
that the heat store has to have significant thermal stratification when
the top of the heat store is at a high temperature which it is desired
to increase efficiently.
The
difficulty of balancing these
factors means experimentation prior to use would be necessary to
determine if this scheme works well. If separate tank or manifold
connections to each radiator proved not to produce sufficient
temperature rise, connecting radiators in series of pairs might be
tried.
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