RADIANT VS. DRY BULB TEMPERATURE (GRAPH 1)
In theory, one might expect to find a great difference
between radiant and dry bulb temperatures in a space heated by a wood burning
stove. It was our initial assumption that the average dry bulb temperature
would be considerably lower than the average radiant temperature throughout
the room. This assumption seemed appropriate due to the fact that
a radiant heat source is responsible for heating surrounding surfaces and
not directly heating the air. The warmth felt from the stove is analogous
to the way the sun heats our bodies even on cold winter days.
However, the data shows a less dramatic difference
between the dry bulb and radiant temperatures than what was expected.
Perhaps this difference occurred from the unseasonably warm and sunny weather
during the period of analysis. It is also important to consider the
influences of the large south facing windows which provided solar gain
in the room. In an ideal experiment the sun would be prevented from
entering the room and the outside temperatures would be more typical of
winter conditions.
In spite of the unfortunate nature of scientific
experiments, there are clear facts presented by this graph about the thermal
conditions of the space. Reading from left to right there is a sharp
increase in the pink line indicating the period in which the fire box was
emitting the maximum amount of radiant temperature. This is also
the period with the greatest difference between the radiant temperature(pink)
and the dry bulb temperature(purple). As a result, the heat felt
in the space would predominately be a product of the radiant warmth of
the stove. Later in the day, however, the difference between the
radiant and dry bulb temperature diminishes and the room levels out at
a comfortable temperature of 72 degrees Fahrenheit.
MEAN RADIANT TEMPERATURES THROUGHOUT THE ROOM (GRAPH 2)
Graph 2 indicates the stove's effectiveness in providing
a consistent level of radiant heat throughout the room except for a four
and a half hour period following the initial firing. The zone closest
to the stove (zone 2) receives the greatest amount of radiant heat for
that period. As noted earlier it is not until the fire burns out
that the room temperature begins to equalize. Eventually, the extreme
zone of the room (zone 4 with a distance of 18 feet from the stove) is
only a few degrees cooler than zone two, which is 6 feet from the stove.
It is also apparent that the surface temperature
of the stove (dark blue line) peaks approximately six hours after the fire
burns out. Being constructed entirely of soap stone, the stove conducts
heat effectively through the entire thermal mass. In addition, the
stove is designed to channel smoke in a meandering pattern around the fire
box as well as through the entire cavity of the stove before releasing
it to the atmosphere. This maximizes total heat output from the wood
exposing the stone to the highest possible temperatures for optimum absorption.
As a result, the stove continues to heat itself long after the fire burns
out. The surface temperature of the stove does not drop below 108
degrees Fahrenheit before the following day's firing.
THE NEAR AND FAR ZONES (GRAPHS 3 AND 4)
These graphs show the greatest temperature difference
between zones 2 and 4. This difference occurs at the initial firing
and gradually diminishes as the fire burns out. The fire burns for
approximately two hours, producing the maximum radiant temperature of 94
degrees Fahrenheit at the closest zone(2) and a maximum temperature of
85 degrees Fahrenheit at the furthest zone(4). Three hours later
the radiant and dry bulb temperatures of both zones(2 and 4) are within
a three degree difference relative to each other. Through the night
the temperatures fall at a slow, constant rate (about 5 degrees Fahrenheit)
and by morning there is still little difference between the radiant and
dry bulb temperature in the near and far zones.
COMPARING THE DATA (GRAPH 5)