Cooling channels

In order to keep the wall temperature below the material melting point it is required to use some sort of cooling, for this reason various methods for cooling thrust chambers have been used in the past decades. Surely, regenerative cooling is the most extended method. 

Regenerative cooling uses a stream of propellant flowing through small channels or tubes around the combustion chamber to cool it down, then the heated propellant is fed into the combustion chamber to be burned. The diagram below shows how the temperature is reduced at different points. The notation used for the temperatures at those points is the following:

Tc = Combustion temperature

Taw = Adiabatic wall temperature

Twg = Wall temperature at the gas side

Twc = Wall temperature at the coolant side

Tbc = Coolant bulk temperature

Simulation results

More than 15 designs with their respective simulations have been made in order to provide the engine with an efficient cooling system. The first image shows the temperature along a section of the engine wall. The second one shows the temperature of the coolant inside a channel.

Note that the temperature of methanol is under 423 K because at 70 bars and up to 473 K, methanol is an incompressible liquid. If higher pressure and temperature were reached methanol could become supercritical as shown on the phase diagrame of methanol.

Source: Engineering ToolBox, (2018). Methanol - Thermophysical Properties. [online] Available at: https://www.engineeringtoolbox.com/methanol-methyl-alcohol-properties-CH3OH-d_2031.html