Frost is no friend to heating, ventilation, air-conditioning and refrigeration (HVAC&R) equipment. For decades, researchers have explored ways to prevent and remove frost buildup that can compromise HVAC&R equipment performance. Now, a team of UMD mechanical engineering researchers has extensively demonstrated application of a promising method called the electrohydrodynamic (EHD) technique that can substantially reduce the frost growth and eventually eliminate frost formation on heat transfer surfaces. The Center for Environmental Energy Engineering (CEEE) team presented their findings in Philosophical Transactions A in a special theme issue on “Heat and Mass Transfer in Frost and Ice,” published last month.

EHD uses high-voltage electric fields to affect the amount and shape of frost formation. As the electric field is increased, ice crystals are pulled in the direction of the electric field, thus becoming thinner, weaker and easier to remove from the surface.

“This increase in the growth rate causes the ice crystal to become thinner and more fragile, which makes it easier to fracture and remove,” says lead author Franciene Pacheco de Sa Sarmiento, a postdoctoral researcher with CEEE’s Advanced Heat Exchangers and Process Intensification Consortium. The other authors are Assistant Research Professor Andres Paul Sarmiento and CEEE Co-Founder and Minta Martin Professor Michael Ohadi.

There’s little consensus on the specific parameters that best facilitate EHD, such as AC versus DC voltage, the researchers found. Other questions include whether a continuous application of the electric field or an intermittent application yields better results. “Additional studies aimed at the EHD control of frost are needed to settle several uncertainties and inconsistencies among some of the previous studies,” says Pacheco de Sa Sarmiento. The next step for the UMD team includes working with CEEE’s industry consortia members to apply the use of EHD frost control to HVAC equipment under realistic operating conditions and geometry scales.

Download the paper: “Control of frost formation in refrigeration applications utilizing the electrohydrodynamic technique—fundamentals, past work and prospects.”