Anti-icing Coatings
Coating Development and Evaluation
For many applications such as airplane wings, refrigeration, power grid lines, etc., the icing behavior on surfaces needs to be inhibited or manipulated. With the growing market share of electric vehicles (EVs), heat pump technology becomes especially important because it is critical for extending the mileage for EVs. Yet, heat pump performance is severely constrained by frost on the evaporator in low-ambient-temperature environment because frost acts like insulation and blocks the air flow to the evaporator. This project aims to design a durable coating to delay frost formation on evaporators while maintaining their heat transfer performance.
We develop our coating using a vast range of properties of polymers. We then test our coatings in an icing test setup shown in Figure 1. The test setup evaluates both the ice initiation time and the ice propagation time on any substrate over a wide range of environmental conditions (substrate temperature: -30 ºC – 0 ºC; relative humidity 30% – 95%). Icing tests are performed in a transparent chamber in which a constant humidity can be maintained. A sample is adhered to an aluminum cooling stage. The sample is placed vertically for video recording.
Heat Exchanger Frosting
After we develop the coating on a flat surface on the small scale (~cm), we plan to investigate ways to apply the coating on evaporators. The goal of this project will be developing a commercially relevant anti-icing coating for application on evaporators for heat pumps, refrigerators, and air conditioners. The coverage of the overall surface and the uniformity of the thickness will be the two major parameters to be considered.
We plan to test the coating performance in a wind tunnel as shown in Figure 2. Transient and steady-state frost accumulation will be measured for a coated evaporator and a baseline evaporator. The attendant impact of frost on the thermal-hydraulic performance of the evaporator will be quantified. Sensible air-side HTC and friction factors will be measured under conditions with various humidity.
Test setup to precisely measure the ice initiation and propagation times at different substrate temperatures (-30 C - 0 C) and relative humidity (30% - 90%)
Closed-loop wind tunnel to test coupon-size coating samples/full-scale heat exchangers. Air speed: 2 – 10 m/s, air temperature: 15 − 50 ˚C, air relative humidity: ambient RH − 85%
Design of Facilitated Transport Hybrid Membranes for CO2 Separation
CO2 capture technology for CO2-intensive thermal powerplants, petrochemical plants and refineries and other industries with large greenhouse gas production footprint will be the key to achieving and possibly exceeding the ambitious global climate change targets. Various CO2 capture technologies include absorption, adsorption, membrane, biological capture, and cryogenic capture. Compared to other separation methods, membrane separation is generally more energy efficient and environmentally benign, thus has been intensively studied for CO2 capture.
Based on the properties of the materials, there are three types of membranes in general: inorganic, polymeric, and hybrid membranes. Hybrid membranes, or mixed matrix membranes (MMM), which normally consist of an inorganic component incorporated into the polymer matrix in the nanoparticles form are becoming a new trend to improve the performance of polymeric membranes, as they can possess the advantages of both polymeric and inorganic materials. There are two basic types of mechanisms for a typical membrane gas separation process: the solution-diffusion mechanism and the facilitated transport mechanism. The solution-diffusion mechanism has the partial pressure of the penetrant gases as the driving force. The facilitated transport mechanism relies on the reversible acid-base or complexation reactions within membranes, which can be manipulated to preferentially facilitate the transport of CO2 molecules. Figure 3 illustrates CO2 permeation in facilitated transport membranes, which involves facilitated transport of CO2 with carriers besides the underlying solution-diffusion of CO2. The non-reactive gas N2 is transported only by the solution-diffusion mechanism. High CO2 permeability accompanied by high selectivity over N2 can be thus achieved in facilitated transport membranes.
The facilitated transport mechanism can also enhance the CO2 transport of hybrid membranes by incorporating carrier fillers with specific functional groups into the polymer matrix — this new concept is named facilitated transport hybrid membranes (FTHMs). In this project, we will design and fabricate FTHMs for CO2 separation.
CO2-selective facilitated transport membrane: the facilitated transport mechanism helps the CO2 molecules to permeate through the membrane in addition to the solution-diffusion mechanism, while the N2 molecules are only transported via the solution-diffusion mechanism.
Research Sponsors
Research
