Mid-Atlantic Masonry Heat - Warms you like a hug
Tulikivi Talk - Direct Thermal Gain's Impact on Thermal Comfort
The following discussion of direct thermal gain attempts to convey insight as to how the radiant transfer of heat from one object to another relates to hearth products in general and Tulikivi heaters in particular.
Hearth appliance can radiate heat to a room in the same way the sun radiates heat to the earth, providing direct thermal gain to persons in the area surrounding the appliance. They can do this when their radiant surfaces are warmer than a person’s body. During the heating season, this direct thermal gain generates a warm, cozy feeling which is missing with heating systems that transfer heat indirectly by convection or the circulation of forced air.
The comfort zone around a hearth appliance providing direct thermal gain to a room, can vary in size significantly. For example, woodstoves with high surface temperatures of 400-600° F. have a ring-shaped comfort zone around them, the direct thermal gain is uncomfortably hot near the stove and dissipates as one moves away. The loss of direct thermal gain occurs because the stove’s high surface temperatures cause the air around the stove to expand and rise to the ceiling, converting the stoves heat transfer from that of radiant to convection. There is a narrow band around the stove where the direct thermal gain is not too hot, near the stove and has not dissipated, away from the stove.
In contrast, a Tulikivi heater has thousands of pounds of thermal mass which captures the heat from a fire and then radiates that heat from its surface, for an extended period, long after the fire has gone out. The large thermal mass allows the heater to maintain moderate surface temperatures of 100-150° F. These lower temperatures minimize the conversion of heat transfer from radiant to convection. The Tulikivi’s temperature is not too hot to touch or lean against, while its direct thermal gain is felt on all the surfaces, objects and persons throughout the room. Its gentle radiant heat transfer warms the room without promoting drafty circulation of air from windows and other cold room surfaces, persons in the room experience significantly improved thermal comfort.
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