Multipass Heat Exchanger Sizing for Optimum Liquid Oxygen Densification with Liquid Nitrogen

Abstract

A liquid oxygen (LO2) densifier model was developed using the EASY5 engineering software program, and a parametric study was conducted using the model to determine the effects of densification flow rate and heat exchanger tube diameter on LO2 densification. The study shows that LO2 subcooling increases with decreasing heat exchanger flow rate and increasing tube diameter. Hence, it is desirable to have lower densification flow rates and larger tube diameters to maximize subcooling. The study also shows that a maximum LO2 subcooling of 22.1 R can be obtained at 1 lbm/sec or 6.4 gpm per tube in a 300-ft long and 11⁄4-in aluminum tube. Under these conditions, the pressure drop through a single tube is only 1.1 psi, even with 38 bends in each tube. To achieve 128 gpm (20 lbm/s) densification flow rate as reported in earlier densification studies using a single pass heat exchanger, the multipass shell-and-tube heat exchanger can be designed to have 20 tubes and 20 passes per tube. Compared with the single pass heat exchanger, the multipass heat exchanger is much shorter and has a simpler design with only one shell.