Effect of frost growth on the performance of louvered finned tube heat exchangers

With an increase of 53% in air velocity, the frost mass accumulated increased by 28% under Kondepudi and O'Neal (1989) conditions.

“With an increase of 53 % in air velocity, the frost mass accumulated increased by 28 %.”

Higher air velocity leads to a higher heat and mass transfer coefficient, thereby increasing the amount of moisture converted to frost in the same time period.

“They explained that higher air velocity leads to a higher heat and mass transfer coefficient, thereby increasing the amount of moisture being converted to frost in the same time period.”

As air velocity increases, the frosting rate increases.

“For the effect of air velocity on frosting rate, Gatchilov and Ivanova (1979), Kondepudi and O'Neal (1989) and Rite and Crawford (1991) agreed that as the air velocity increases, the frosting rate increases.”

Kondepudi and O'Neal (1989) proposed that the energy transfer coefficient E_o can be expressed by equation (4.4).

“Kondepudi and O'Neal (1989) in their paper proposed that the energy transfer coefficient, E o , can be expressed as follow: p,a o Q.C E LMED.A = (4.4)”

The decreasing trend agrees with results reported by Kondepudi and O'Neal (1989) and Ameen (1993).

“This decreasing trend agrees with all the results reported by researchers such as Kondepudi and O'Neal (1989) and Ameen (1993).”

Kondepudi and O'Neal [2] derived an energy transfer coefficient in terms of the logarithmic-mean enthalpy difference, but they did not attempt to obtain the air-side convective heat transfer coefficient using the enthalpy difference.

“Kondepudi and O Õ Neal [2] derived an energy transfer coefficient in terms of the logarithmic-mean enthalpy difference, but they did not attempt to obtain the air-side convective heat transfer coefficient using the enthalpy difference.”

Very little has been published to address frost formation and defrosting on louvered, folded-fin heat exchangers.

“Since very little has been published to address frost formation and defrosting on louvered, folded-fin heat exchangers, there is little basis available in the open literature for the design of microchannel heat exchangers under frosting conditions.”

Several parameters affect frost formation on outdoor coils, including air velocity, air humidity, air temperature, cold surface temperature, surface energy and fin-base microscopic characteristics, fin geometry, and coil water retention after defrost cycles.

“There are several parameters that affect frost formation on outdoor coils, such as air velocity, air humidity, air tempera ture, cold surface temperature (Kondepudi and O'Neal, 1989; Leeetal., 1997) surfaceenergyandfin basesurfacemicroscopic characteristics (include coatings and roughness or brazing fluxes) (Na and Webb, 2003; Shin et al., 2003), fin geometry and coil water retention after defrost”