Universal Critical Heat Flux (CHF) Correlations for Cryogenic Flow Boiling in Uniformly Heated Tubes

Liquid Nitrogen Flow Boiling Critical Heat Flux in Additively Manufactured Cooling Channels

“…Cryogenic fluids exhibit some unique characteristics, such as low surface tension, low liquid viscosity, low latent heat of vaporization, small density difference between the liquid and gas phases [1], and large compressibility [2]. These unique thermophysical properties of cryogenic fluids have contributed to its application in the multitude of terrestrial and space systems including cooling of high-temperature superconductors [2,3], cryosurgery [4], metal processing [5], air separation units, chilling down of telescopes and satellites [1], regenerative cooling of liquid rocket engines [6,7] and so on. In regeneratively cooled rocket engines, the propellant or the oxidizer flows through the cooling channels surrounding the combustion chamber and nozzle walls to absorb heat and maintain the structural integrity of the thrust chamber [8,9].…”

“…Further increase in heat flux results in the competition between vapor generated at the wall and the replenishing liquid until the hot wall reaches critical heat flux (CHF). Two types of CHF events are encountered for cryogenic cooling, known as departure from nucleate boiling (DNB) type CHF and dry-out type CHF [1]. During DNB, the vapor bubbles from the wall are unable to penetrate the highly sub-cooled liquid core flow at high mass flux resulting in a localized vapor blanket.…”

“…A variety of publications have reported flow boiling CHF values for cryogenic liquids including liquid hydrogen (LH 2 ), helium (LHe), nitrogen (LN 2 ), and methane (LCH 4 ). In 2021, Ganesan et al [1] consolidated 2312 CHF data points from world cryogenic literature dating back to 1959. The database contains single component cryogens flowing vertically upward or downward, and horizontal, and symmetrically heated straight stationary circular channels.…”

“…In addition to high coolant mass flux, small channel cross-sectional area, and high heat transfer rates, other factors, such as channel material, channel geometry, fabrication method and imposed heat flux direction, play significant roles in cooling channel design for liquid rocket engines. Significant experimental research has been reported on cryogenic flow boiling in symmetrically heated circular channels [1]. However, rocket engine cooling channels experience asymmetric heat flux from the combustion chamber hot wall [17][18][19][20].…”

“…Yet, a limited amount of research has addressed the experimental cryogenic flow boiling using non-circular geometries, such as square and high aspect ratio rectangular channels, more specifically asymmetrically heated non-circular cooling channels. Additionally, a vast majority of the cryogenic flow boiling tests have been conducted using stainless steel tubes while some researchers utilized nickel alloys and fewer employed copper and silver tubes [1]. However, Glenn Research Copper (GR-Cop) alloys are the preferred combustion chamber materials due to their high thermal conductivity, low creep and low-cycle fatigue, oxidation and blanching resistance, and high material strength at elevated temperatures with sustained operations [24,25].…”