M.Sc Thesis

M.Sc StudentLusztig Schvartz David Dov
SubjectHeat and Mass Transfer in an Adsorptive Thermoacoustic
DepartmentDepartment of Civil and Environmental Engineering
Supervisor ASSOCIATE PROF. Guy Ramon
Full Thesis textFull thesis text - English Version


A major motivation of the research was investigating a possible improved process comparing the traditional "dry" thermoacoustic heat pump - gaining an additional generated heat flux through mass transfer and phase-exchange, "wet" thermoacoustics mediated by adsorption. For validating the process, an experimental system was designed, fabricated and tested, comprising a resonator, loudspeaker and a stack coated with selective adsorbing bed such as 13X and 5A zeolites and 100% water vapor. The system contained air as a model mixture. Temperatures and water vapor mass (humidity) were measured at both sides of a stack under variable conditions like the location of the stack along the resonator, the material of the stack, adsorbent type, the system ambient pressure and the acoustic energy input. In addition, a preliminary CO2 experiment was held.

Clear trends were obtained from the experiment results, which can be cautiously connected with the effect of the added mass transfer to the acoustic heat pump. At more detailed resolution, the type of the coating affected both the temperature and the humidity differences measured and calculated between both sides of the stacks. A 13X zeolite coating usually lead to higher temperature differences, while 5A zeolite and 100% water vapor in most cases reduced it comparing to non-coated stack, and all of them raised humidity differences much more than a non-coated stack, or in other words, a coating material probably increases the effectivity of the mass pump. This trend was clearer at metal stack comparing to cordierite stack. In addition, the thermoacoustic effect was stronger when the stack was located in the end of the resonator, at the area of highest pressure fluctuations, resulted at both higher temperature and humidity deltas comparting the middle of the resonator location. Higher differences can also be linked to higher acoustic power (pressure), but it was consistent only up to ~3000 Pa, while added more acoustic power above that level had less effect, and no effect was observed over ~6000 Pa, probably due to the transition of the heat pump into engine at high heat gradients. In addition, preliminary results for CO2 mass pump indicated possible equivalent trend as seen with the vapor experiments.

Further experimentation is required for examining the practicality and feasibility of the "wet" thermoacoustic heat pump over the "dry" one. Furthermore, this process has the potential to also carry out mixture separation in a simple, continuous, small and portable device compared with current technology, based on Pressure Swing Adsorption (PSA).