Numerical Simulation of Vapor Bubble Growth In Saline Water Solution During Nucleate Pool Boiling

Abstract

Boiling heat transfer is a two-phase heat transfer phenomenon characterized by formation of vapor bubbles at heated surface. Scarcity of freshwater, population growth, and climate change have increased the demand for desalination and saline water utilization in various energy and chemical plants. Thermal desalination processes use phase change to separate volatile solvents such as water from nonvolatile solutes such as salts. Thermal desalination systems can be effectively coupled with waste heat recovery systems available in various industries. Thermophysical properties of saline water solution is significantly different from freshwater due to presence of salts. This research work numerically simulates growth and departure of vapor bubbles in water with different concentrations of salts, wall superheat and pressures during nucleate pool boiling. Salt concentrations can play an important role in influencing the wall heat transfer and bubble dynamics. A three -dimensional model of vapor bubble is developed using the level-set method. Complete Navier-Stokes equations have been solved using the SIMPLER algorithm. The bubble growth process is simulated in a rectangular domain with bubble placed at bottom on a heated wall. Thermo-physical properties of liquid and vapor are adjusted based on the salt concentrations and pressure. Bubbles grows larger in size and takes less departure time at higher salinities. Higher superheat makes bubble to grow larger, depart faster and improves Nusselt's number. Increasing pressure suppresses the bubble size during departure and makes it stay for longer duration on the wall.