Flow Boiling Module

The Flow Boiling Test Module (FBM) investigates flow boiling phenomena in microgravityThe condition of perceived weightlessness created when an object is in free fall, for example when an object is in orbital motion. Microgravity alters many observable phenomena within the physical and life sciences, allowing scientists to study things in ways not possible on Earth. The International Space Station provides access to a persistent microgravity environment.. It contains temperature and pressure sensors, a heated test section, and flow visualization hardware to capture microgravity flow boiling steady-state and critical heat flux (CHF) data. The FBM consists of a rectangular flow channel 5.0 mm high by 2.5 mm wide, with an adiabatic developing length of 327.9 mm, a heated section of 114.6 mm with heating provided on two opposite sides, and an exit length of 60.9 mm. Flow of nPFH is introduced/pumped into the channel at different flow rates up to 40 g/s as subcooled, saturated liquid or two-phase fluid, and as the fluid passes through the heated section, flow boiling occurs. The heat flux to the heated section is increased in a prescribed manner until the critical heat flux is achieved. Two sets of seven Type-E thermocouples are inserted into shallow holes along the centerline of each copper plate between the resistors. If any of these thermocouples senses a maximum temperature of 122 °C or greater, the flight software decreases the power to the heaters in the FBM and records the heat rate imposed on the heaters that resulted in the 122 °C as the CHF. Pressure is also measured at five different locations along the unheated and heated section. Up to 175 W per side can be delivered to the heaters in the FBM. A high-speed camera of 2,000 frames/s is used in FBM to capture the flow boiling process and the state of the fluid near and at the critical heat flux point.