Tiled Masonry Stove

What is modelled

A lumped model with three temperatures: the masonry, the room air and the outdoors. The fire delivers heat to the masonry while it burns, the masonry gives heat to the room through its surface, and the room loses heat through its walls. Heavy masonry stores more heat and releases it more slowly, so the room swings less. The 3D page shows the stove and its internal gas path; it has no controls, so every input here is the model's own.

Equations

• Fuel power P = mfuel · 15 MJ/kg / tburn, of which a share γ = 0.72 reaches the masonry (the rest leaves with the flue gas).
• Masonry C dTm/dt = γ P - (hA)(Tm - Tr) with C = m c, c = 900 J/kg/K.
• Room Cr dTr/dt = (hA)(Tm - Tr) - UAr(Tr - Tout).
• Time constant τ = C / (hA); surface area scales as m2/3.

Checks run in the page

• Energy balance over 36 h: heat in = stored in stove and room + lost through the walls.
• Masonry cooling against the exact exponential with the room held fixed.
• Steady state of a continuous fire against the closed form T_out + P/UA.
• Fuel energy against the summed fire power.

Honest simplifications

One lumped temperature for the whole stove, a constant surface coefficient, a fixed share of fire heat reaching the masonry, one air node for the room, no radiation exchange with the walls and no draught or ash losses. Real masonry stoves have strong internal gradients and a surface that is much hotter than the core mean. Numbers are of the right size, not measurements of the Baturyn stove.

• Compare Light stove with Heavy stove: the same fuel gives a hot short peak or a flat long warmth.
• Choose Two firings to see the room hold its temperature across a cold night.
• Raise the room heat loss and watch the comfort hours fall.