How to design a rocket mass heater for maximum efficiency?

Combustion Chamber Design

The combustion chamber is the heart of the rocket mass heater, where fuel is burned to produce heat. For maximum efficiency, design the combustion chamber with a large enough diameter to ensure proper combustion, but not so large that it reduces heat transfer. A diameter of 6-8 inches (15-20 cm) is a good starting point. The chamber should also have a length of at least 12-15 inches (30-38 cm) to allow for complete combustion. Use a refractory material such as ceramic fiber or castable refractory to line the chamber and withstand high temperatures.

Riser and Vortex Design

The riser is the vertical tube that connects the combustion chamber to the heat exchanger. A well-designed riser creates a vortex that pulls heat from the combustion chamber and transfers it to the heat exchanger. To create a proper vortex, design the riser with a diameter that is 10-20% smaller than the combustion chamber. This will create a velocity gradient that pulls the hot gases upward, creating a vortex that transfers heat efficiently. The riser should also be long enough to allow for complete combustion and heat transfer, with a minimum length of 12-15 inches (30-38 cm).

Insulation and Heat Exchanger

Insulation and a well-designed heat exchanger are crucial for maximizing efficiency in a rocket mass heater. Use a high-quality insulation material such as Reflectix or Thinsulate to line the exterior of the heater, and ensure that all seams are sealed to prevent heat loss. The heat exchanger should be designed to transfer heat efficiently, with a large surface area and a long enough length to allow for complete heat transfer. A heat exchanger with a surface area of at least 10-15 square feet (0.9-1.4 square meters) is a good starting point.