Thermimage (version 4.0.1)

forcedparameters: Parameters required for forced convection equation.

Description

Parameters required for forced convection equation and heat exchange estimation.

Usage

forcedparameters(V = 1, L = 0.1, Ta = 20, shape = "hcylinder")

Arguments

V

Air velocity in metres/second. Used in call to Reynolds(). Default is 0.1.

L

Characteristic dimension in metres. Default value is 0.1.

Ta

Air temperature in degrees celsius. Used in call to Reynolds(). Default is 20.

shape

"sphere", "hplate", "vplate", "hcylinder", "vcylinder" to denote shape and orientation. h=horizontal, v=vertical. Default shape is "hcylinder"

Value

A vector of length two, with values c and n.

Details

Gates (2003) describes coefficients that characterise the base and exponent values used to calculate Nusselt numbers from Reynolds number as: c*Re^n. This function will return those parameters.

References

Blaxter, 1986. Energy metabolism in animals and man. Cambridge University Press, Cambridge, UK, 340 pp.

Gates, DM. 2003. Biophysical Ecology. Dover Publications, Mineola, New York, 611 pp.

See Also

freeparameters Nusseltforced

Examples

# NOT RUN {
## The function is currently defined as
function (V = 1, L = 0.1, Ta = 20, shape = "hcylinder") 
{
    Re <- Reynolds(V, L, airviscosity(Ta))
    if (shape == "vplate" | shape == "hplate") 
        shape <- "plate"
    if (shape == "vcylinder" | shape == "hcylinder") 
        shape <- "cylinder"
    if (shape == "plate") {
        c = 0.595
        n = 0.5
    }
    if (shape == "sphere") {
        c = 0.37
        n = 0.6
    }
    if (shape == "cylinder" & Re >= 0.4 & Re < 4) {
        c <- 0.891
        n = 0.33
    }
    if (shape == "cylinder" & Re >= 4 & Re < 40) {
        c <- 0.821
        n = 0.385
    }
    if (shape == "cylinder" & Re >= 40 & Re < 4000) {
        c <- 0.615
        n = 0.466
    }
    if (shape == "cylinder" & Re >= 4000 & Re < 40000) {
        c <- 0.174
        n = 0.618
    }
    if (shape == "cylinder" & Re >= 40000 & Re < 4e+05) {
        c <- 0.024
        n = 0.805
    }
    coeffs <- c(c, n)
    names(coeffs) <- c("c", "n")
    coeffs
  }
  # Example:
V<-1
L<-0.1
Ta<-20
shape="hcylinder"
forcedparameters(V, L, Ta, shape)

shape="vcylinder"
forcedparameters(V, L, Ta, shape)

shape="hplate"
forcedparameters(V, L, Ta, shape)

shape="vplate"
forcedparameters(V, L, Ta, shape)

shape="sphere"
forcedparameters(V, L, Ta, shape)

# }