Heat transfer aspects and analysis of regenerative cooling in semi-cryogenic thrust chamber with fixed and variable aspect ratio coolant channels

Semi-cryogenic rocket engines have very high combustion temperatures inside its thrust chambers which lead to huge chamber wall heat fluxes. Hence appropriate cooling methods are to be implemented to maintain the chamber wall temperatures within the safe limits. Regenerative cooling is the most commonly used cooling method in liquid propellant rocket engines. Recent studies has shown that using coolant channels having high height to width ratios (Aspect ratio) results in better cooling of the thrust chamber walls but implementing such channels along the entire length of the thrust chamber produces excessive coolant pressure drop. In this study, a computer program has been developed to perform two dimensional heat transfer analysis of regenerative cooled thrust chambers with coolant channels of rectangular cross section. The effect of aspect ratio and number of coolant channels on chamber wall temperature as well as coolant pressure drop is analysed. Analysis has also been conducted for variable aspect ratio coolant channels such that high aspect ratios are employed only in the critical regions. The engine considered for analysis is designed to produce 600 kN of thrust, has a chamber pressure of 60 bar and runs on LOX/RP-1 mixture with RP-1 as the coolant.