masonry heater lecture

HEAT AND

MASONRY HEATERS

Lecture Topics• Introduction• Burning Wood• What is a Masonry Heater-Advantages and Differences• Materials used to Build a Masonry Stove• Ability to Heat• Chimneys-How do they work?

Introduction• About me• What’s the Lecture about?• Burning Wood, Masonry Heaters, Chimneys

Chemical Reaction of Burning Wood• Wood collects energy from sun when growing• When wood burns, it releases roughly the same amount

of heat• PYROLYSIS

• “Primary Combustion” is the burning of solid material directly.

Secondary Combustion

• “Secondary Combustion” is the burning of gas fuels

which produces the flames of a fire.• 3 T’s for Secondary Combustion• Clean and Efficient

• video of secondary combustion

A Masonry Heater• A masonry heater is a site-built or site-assembled, solid-

fueled heating device constructed mainly of masonry materials in which the heat from intermittent fires burned rapidly in its firebox is stored in its massive structure for slow release to the building. It has an interior construction consisting of a firebox and heat exchange channels built from refractory components.-MHA website

Masonry Heater• What is it?

Masonry Heater Differences• Materials-bricks, fire bricks, metal parts, mortars (clay,

firebox mortar), high temperature cement, tiles, various veneers (soapstone, limestone, sandstone )

• Effectiveness• Efficiency-use less wood, burn more cleanly• Good for Environment

Bricks

Fire Bricks

Clay Mortar• Simple clean clay and sand + water• Why? Heater must move with THERMAL EXPANSION

High Temp. Concrete and Mortar• Used mostly in fireroom where temperatures can reach

over 1000 degrees C.

Ability of Different Materials• Brick• Soapstone• Firebrick• Granite • Limestone• Sandstone• Tile (kacheln)

• How do different materials act when used for building a masonry heater?

Things to consider with materials• Density• Conductivity• Specific Heat Capacity• Diffusivity• Emissivity• Thickness

Density• A materials weight per volume• Holds more heat

Conductivity• Thermal Conductivity• Ability to conduct or transmit heat• BTUs/ft/hr/F degree or Watts/m/K degree• Metal conducts quickly• Stone/brick more slowly-good !

Specific Heat Capacity• Energy needed to heat something up OR• How much heat a material can hold

Diffusivity• Speed at which heat moves through a material• Ex. Paper towel• Meters squared /second• Ratio between how fast a material transfers heat to how

well heat is stored

Emissivity• Ability of material to give off or emit heat• Based on ‘black perfect body’ = 1

Thickness• The thicker the material is, the longer it takes for the heat

to travel through....

Common Heater Materials• Masonry brick (red)• Firebrick• Granite• Limestone• Sandstone• Tile (kacheln)

• SOAPSTONE

What about the Chimney?• How or why does a chimney work?• What laws of physics are seen?• Stack effect

Stack Effect in a House

• Pressure differences between air outside and air inside created mostly by the temperature difference.

• Warm air rises, cold air sinks or falls• Chimney is a place for the equaling of pressure to occur• The stack effect is what makes a masonry heater work

In Conclusion......