Rocket mass heater

Variations of RMH can also be extended for the functions of cooking, heating water, and producing warm air for distribution.

A primary design of a rocket mass heater consists of an insulated combustion chamber where fuel is burned with high efficiency at high temperature, and a large thermal mass in contact with the exhaust gases, which absorbs most of the generated heat before the gases are released to the atmosphere.

[2] According to anecdotes a rocket mass heater might reduce fuel consumption by 80–90% compared to "conventional" stoves.

[3][4] In contrast to conventional wood-burning stoves and fireplaces, in a rocket mass heater, combustion is close to complete.

In a rocket mass heater, by-products of combustion, such as smoke, soot, and creosote compounds, are sucked into the insulated tunnel of the unit, where some[who?]

claim they further combust, releasing even more heat energy to drive the rocket process, unlike a normal fire, where they are blown out the chimney.

In all designs, an internal insulated chimney called a "heat riser", produces an efficient high-temperature burn creating sufficient draft to push exhaust gases through the rest of the system.

In the earliest and most popular form, wood is gravity-fed into a "J-shaped" combustion tube, from where the hot gases enter a well-insulated firebrick or ceramic refractory vertical secondary combustion chamber, the exhaust from which then passes along horizontal metal ducting embedded within a massive thermal store.

[5] More recent alternate developments have instituted a batch-fed horizontal firebox called "batch box", which feeds into the vertical heat riser or secondary combustion chamber.

[10] Because of the relatively low thermal conductivity, a mass consisting of cob can absorb heat and retain it for a longer period.

[8] The heat riser is an insulated, vertical channel that draws flames upward and powers the rest of the firebox.

To allow efficient convective currents, the barrel should be made of steel or materials with higher thermal conductivity.

J-tube rocket mass heater in operation. 1. Vertically inserted wood burns sideways. 2. High temperature creates strong convective currents in the heat riser. 3. Exhaust gas exits sideways. 4. Heat exchange mass absorbs, stores, and radiates away heat. 5. Final exhaust made of Carbon Dioxide and steam)