文档介绍：Frost growth and densification on a flat surface in laminar flow with variable
humidity
M. Kandula1
ESC- Team QNA, NASA Kennedy Space Center, Florida 32899, USA
Abstract
Experiments are performed concerning frost growth and densification in laminar flow over a flat
surface under conditions of constant and variable humidity. The flat plate test specimen is made
of aluminum-6031, and has dimensions of mm. Results for the first variable
humidity case are obtained for a plate temperature K, air velocity of m/s, air
temperature K, and a relative humidity continuously ranging from 81 to 54%. The
second variable humidity test case corresponds to plate temperature K, air velocity of
m/s, air temperature K, and a relative humidity ranging from 66 to 59%. Results
for the constant humidity case are obtained for a plate temperature K, air velocity of
m/s, air temperature of 295 K, and a relative humidity of %. Comparisons of the data with
the author's frost model extended to modate variable humidity suggest satisfactory
agreement between the theory and the data for both constant and variable humidity.
Key words: Frost growth, Densification, Variable humidity, Flat Surface, Laminar flow
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Nomenclature
he convective heat transfer coefficient (W/m2 K)
hm convective mass transfer coefficient (kg/m2 s)
k1 effective thermal conductivity of frost (W/m K)
L plate length (m)
Lsv latent heat of sublimation (kJ/kg)
T temperature (K)
u air velocity (m/s)
Greek Symbols
fjJ relative humidity (%)
v kinematic viscosity (m2/s)
3
p 1 frost density (kg/m )
3
Pice ice density (kg/m )
OJ humidity ratio of moist air, kg (water vapor)/kg(dry air) or kgvlkga
Subscripts
a atr
m melting
s frost surface
v water vapor
w wall
I. Introduction
Frost formation represents an important consideration in ma