1Department of Mechanical Engineering, LBS College of Engineering, Kasaragod-671542, India.
2Department of Mechanical Engineering, National Institute of Technology Calicut, Kozhikode-673601, India.
List of symbolsC(c)
Concentration of particles in the gas
CpSpecific heat of gas with suspended particle at constant pressure
C(c)Concentration of particles in the gas
CpSpecific heat of gas with suspended particle at constant pressure
GrGrashoff number
HHalf width of channel
kThermal conductivity of gas particle mixture at constant pressure
KThermophoretic coefficient
LNon dimensional channel height
P(p)Non-dimensional pressure
Q(q)Intensity of heating
PrPrandtl number
T(t)Temperature
U(u)Longitudinal velocity
V(v)Transverse velocity
V (vt)Thermophoretic velocity perpendicular to the plate surface
X,Y (x,y)Coordinates along the length of the plate and perpendicular to the plate surface, respectively
Greek symbolsβCoefficient of thermal expansion
μDynamic viscosity of the gas
νKinematic viscosity of the gas
ρDensity of the gas
SubscriptswWall or plate surface value
oFree stream value
Superscripts*Non dimensional property value
αProperty exponent for density
βProperty exponent for viscosity
γProperty exponent for thermal conductivity
The hot flue gas containing soot particles are found to get deposited on the walls of a chimney as the gas flows through the relatively cooler passage. The velocity acquired by the particle towards the cooler surface and the resultant force acting on the particle are known as thermophoretic velocity and thermophoretic force respectively. Fouling of gas turbine blades and heat exchanger surface are common examples of this phenomenon. The present paper deals with the effect of variation of properties with respect to temperature on thermophoretic phenomenon of natural convection flow in a parallel plate channel. Property variation is taken into by property ratio method in which the property ratio is expressed as a function of temperature ratio. The functional relationship is obtained by fitting the property values within the temperature limits. The natural convection boundary layer equations are solved by finite difference marching technique. Thermophoretic flux which is the mass of particles deposited per unit time per unit area which is determined along the channel height for Pr = 0.70 with air as dispersing medium and oil fog suspension with experimentally determined value of thermophoretic coefficient Kt = 0.75. Comparison is made between constant property and the variable property results for thermophoretic coefficient. It is observed that thermophoretic wall flux decreases when variation of properties with respect to temperature are taken into account. Computer code is written for solution and the results are presented in the form of graphs.
