TAGS: Cost Efficiency Appliances
Texas A&M researchers have enhanced the dehumidification efficiency of a polymer that could help develop more energy-efficient systems with a smaller carbon footprint.
Cost-effective and Energy-efficient HVAC Systems
In this new study, Texas A&M University researchers have described an organic material, called polyimides, that uses less energy to dry air. Furthermore, the researchers said polyimide-based dehumidifiers can bring down the price of HVAC systems, which currently cost thousands of dollars.
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In this study, we took an existing and rather robust polymer and then improved its dehumidification efficiency,” said Hae-Kwon Jeong, McFerrin professor in the Artie McFerrin Department of Chemical Engineering. “
These polymer-based membranes, we think, will help develop the next generation of HVAC and dehumidifier technologies that are not just more efficient than current systems but also have a smaller carbon footprint.”
Strong and Heat-resistant Polyimides to the Rescue
Jeong and team turned to a cost-effective organic material called polyimides that are well-known for their high rigidity and tolerance for heat and chemicals. At the molecular level, the basic unit of these high-performance polymers are repeating, ring-shaped imide groups connected in long chains. The attractive forces between the imides gives the polymer its characteristic strength and thus an advantage over mechanically weak zeolites. But the dehumidification properties of the polyimide material needed enhancement.
The researchers first created a film by carefully applying polyimide molecules on a few nanometers-wide alumina platforms. Next, they put this film in a highly concentrated sodium hydroxide solution, triggering a chemical process called hydrolysis. The reaction caused the imide molecular groups to break and become hydrophilic. When viewed under a high-powered microscope, the researchers uncovered that the hydrolysis reactions lead to the formation of water-attractive percolation channels or highways within the polyimide material.
Successful Water Extraction by Polyimide Membrane
When tested, the enhanced material for dehumidification, the polyimide membrane was very permeable to water molecules. In other words, the membrane could extract excess moisture from the air by trapping them in the percolation channels. The researchers noted that these membranes could be operated continuously without the need for regeneration since the trapped water molecules leave from the other side by a vacuum pump that is installed within a standard dehumidifier.
Jeong said his team carefully designed their experiments to partial hydrolysis wherein a controlled number of imide groups become hydrophilic.
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The strength of polyimides comes from their intermolecular forces between their chains,” Jeong said. “
If too many imides are hydrolyzed, then we are left with weak material. On the other hand, if the hydrolysis is too low, the material won’t be effective at dehumidification.”
Need to Improve Performance
Although polyimide membranes have shown great promise in their potential use in dehumidification, Jeong said their performance still lags zeolite membranes.
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This is a new approach to improve the property of a polymer for dehumidification and a lot more optimizations need to be done in order to further enhance the performance of this membrane,” Jeong said. “
But another key factor for engineering applications is it must be cheap, especially if you want the technology to be reasonably affordable for homeowners. We are not there yet but are certainly taking strides in that direction.”
Source: Texas A&M