KSLV-II (Korea Space Launch Vehicle - II) launch vehicle is a three staged satellite launch vehicle using a liquid propellant propulsion system in all three stages. It will deliver 1,500 kg satellite to Sun Synchronous Orbit (SSO, 700 km, 98.2°) or 2,600 kg satellite to Low Earth Orbit (LEO, 300 km, 80.3°). Propellants for KSLV-II are kerosene as a fuel and liquid oxygen as an oxidizer for propelling.
Those fuel and oxidizer are stored in on-board tanks separately. To run a liquid propellant rocket engine on ground or in flight, those propellants should be supplied to LRE’s using so-called Propellant Pressurizing Sub-system, which makes propellants be pressurized in tanks using pressurant. A pressurant for PPSS of KSLV-II is helium, which is stored in tanks located in an oxidizer tank. The stored He is under cryogenic condition (50 K) as gaseous state. Such He is heated and expanded through heat exchanger, which is using a combustion gas coming out from gas generator for turbo-pump as an energy source, to be used as pressurant. This paper contains the results of performance analysis and thermal-fluidic numerical analysis to develop the above-mentioned heat exchanger for KSLV-II upper stage (the 2nd stage). The technical requirements for such heat exchanger are as follows: pressurant mass flow rate for oxidizer tank - 0.127 kg/sec; and for fuel tank - 0.043 kg/sec. The outlet temperature of He from heat exchanger is 550±10 K.