Research projects focus on water treatment, using thermofluids and nanoengineering.
Batch Reverse Osmosis
David has developed new configurations to enable batch reverse osmosis, which uses time-varying pressure to vastly improve energy efficiency. This technology aims to be the most energy efficient membrane desalination process every demonstrated, and modeling work showing this expected performance has been published in the journal Water Research. David was a competitor on the American Water Association's Tech Idol competition for this work. There has been licensing interest for patents on this from at least 3 companies, which are being actively pursued.
Superhydrophobic Nanoengineered Surfaces
Nanoengineered surfaces can enhance the performance of thermal desalination technologies such as membrane distillation. Here, the aim is to improve mass transfer coefficients while simultaneously trying not to enhance heat transfer as much, thus improving the process at a systems-level. This nano-design, combined with a systems level modelling, can enable substantially enhanced air-gap membrane distillation
Thermodynamic Design of Membrane Distillation
How can membrane distillation (MD) systems be made more efficient? This includes work on the effect of tilt angle on air gap MD performance, system optimization, new modeling techniques for MD, superhydrophobic condensing for MD, and design of multistage MD systems. The analysis for these systems includes thermodynamic and heat transfer modeling with Engineering Equation Solver, designing and building experimental systems for testing heat transfer enhancements and the efficiency of new configurations.
Fouling in Membrane Distillation
Fouling resistance is one of membrane distillation’s greatest strengths, but hasn’t been sufficiently understood to exploit this strength. This research includes studies on fouling, nucleation, filtration, surface modification, superhydrophobic coatings, anti-fouling operating conditions, and the use of air layers to reduce fouling and reverse wetting. For these tests, a membrane distillation fouling testbed has been created, and membranes are tested with SEM, fluorescent light microscopy, liquid entry pressure, porosity, XRD, and EDS.
Other Desalination Technologies
With a growing global water crisis as humanity’s water use exceeds renewable rainwater, desalination and water treatment technologies will play a major role in feeding growing demand, sparing rivers and aquifers. Research on other desalination technologies includes analysis of entropy generation when using waste heat, efficiency comparison with other technologies, and efficiency enhancements on mainstream technologies. This work has included multistage flash (MSF), multi-effect distillation (MED), humidification-dehumidification desalination (HDH), mechanical vapor compression (MVC), reverse osmosis (RO), and counter-current reverse osmosis (CCRO).
Energy Efficiency in Buildings
Buildings use 75% of electricity in the U.S., making building energy efficiency among the most critical low-hanging fruit for reducing carbon emissions cheaply. Past research in energy in buildings includes 1/10-size thermally-scaled buildings with energy control systems. Ongoing energy modeling research also included energy modeling for building control systems including variable air volume and demand control ventilation. Past work while working at the building consulting firm ARUP has included energy modeling, heating and cooling system design, and sustainability analysis for office complexes, art museums, university laboratories, hotels, performing arts centers, restaurants, spas, and embassies, including 6 LEED platinum projects. Additionally, undergraduate work has included coordinating the team for the high-tech, sustainable, international “Solar Decathlon” competition.
Coolify: Cold-chain Phase Change Thermal Storage
Unreliable electric grids have left much of the developing world without cold storage chains, contributing to 30-40% food losses in the supply chain, a major component of world hunger. The startup Coolify addresses this challenge with refrigeration systems with phase change thermal storage. The design allows for cheap continues cooling, and also includes a robust insulation system with multiple contained zones. The prototype was constructed in Cambridge, and the technology is being implemented in India. David is the CTO of Coolify
Other Heat Transfer Projects
Other heat transfer projects have included modeling heat transfer for fish ponds, dinosaurs, household geothermal systems using existing water infrastructure, and solar thermal systems.
Non-Heat Transfer Projects
Other projects have included oxycombustion chemical modeling, finite element analysis for gas turbine blades, proposed wetland construction for pollution mitigation, and spaceship modeling.
Photonic nanomaterial photocatalytic membranes
Many pollutants hazardous to human health, including pesticides, fluoropolymers, and pathogens, can be broken down into their constituent minerals through photocatalysis. However, existing membranes need substantially improved UV light utilization and penetration for real world use. We are working on consistently-sized nanostructures near the wavelengths of UV light to control light and enhance the performance of novel photocatalytic membranes.