Document Type


Date of Award


Degree Name

Doctor of Philosophy in Mechanical Engineering - (Ph.D.)


Mechanical and Industrial Engineering

First Advisor

Chao Zhu

Second Advisor

Zhiming Ji

Third Advisor

I. Joga Rao

Fourth Advisor

Eon Soo Lee

Fifth Advisor

Teh C. Ho


Distillation of aqueous solutions and aqueous mixtures has vast industrial applications, including desalination, wastewater treatment, and fruit juice concentration. Currently, two major distillation technologies are adopted in the industry, membrane separation and thermal distillation. However, both of them face certain inevitable drawbacks. Membrane separation has disadvantages as relying on high-grade energy, requiring membrane, fouling problem, narrow treatment range, limited scalability, and vibrating and noisy operating conditions. Traditional thermal distillation technologies can avoid above concerns but has other shortcomings, such as relatively low energy efficiency and yield rate, complicated and bulky system structure, and scaling problem.

This project proposes an innovative membrane-free low-grade energy driven distillation technology that overcomes all the above drawbacks in current membrane distillation and thermal distillation via a multi-stagger-staged spray flash distillation system. The technology consists of three innovative features: polydispersed spray flash distillation process for improving the evaporation rate and efficiency; the multi-stagger stage arrangement of the system design for realizing a parallel operating control with inter-stage heat recovery; actively vacuumed vapor extraction for achieving a highly thermal non-equilibrium process. Specifically, spray nozzles are equipped within each evaporation chamber to take advantage of pressure dropping demand and boost the distillation effect by dramatically increasing the evaporation area. Each stage is parallelly arranged with each other, in which only the first stage needs an external heat input, and the rest of the stages will be heated via inter-stage heat recovery. All stages are connected to the same active vacuum source. Hence, the operating pressure of each stage can be independently controlled to achieve the most optimized operation. The distillation efficiency will be improved and the non-condensable gas will be timely removed by such an active vapor extraction. In this way, the proposed system can achieve unique advantages such as low-grade heat driven, better yield rate and energy efficiency, no membrane, wider treatment range, scalable, no scaling problem, and safe and quiet operating conditions.

In this dissertation, the technology is developed by the following research logic: proposing an overall system design with working concepts; parametrically studying the curial sub-processes (spray flash and vapor vacuuming) via models and experiments; building the overall systematic model for thermodynamic analysis and system optimization. Specifically, interwind sub-works are conducted as follows: a design of multi-stagger-stage actively vacuumed distillation system; modeling and experimental study of highly non-equilibrium spray flash process; modeling and experimental study of the further spatially dependent salinity effect in spray flash distillation; a point-based modeling methodology of droplet flash process; a CFD study of spray flash process; modeling and experimental study of a lab-scale two-stage prototype; thermodynamic analysis with an overall systematic model.