# forcedparameters: Parameters required for forced convection equation. In Thermimage: Thermal Image Analysis

## Description

Parameters required for forced convection equation and heat exchange estimation.

## Usage

 `1` ```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"

## 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.

## Value

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

## Author(s)

Glenn J Tattersall

## 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.

`freeparameters` `Nusseltforced`
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58``` ```## 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) ```