# Nusseltfree: Nusselt number for free convection. In Thermimage: Thermal Image Analysis

## Description

Nusselt number for free convection. Used in calculating heat loss by convection.

## Usage

 `1` ```Nusseltfree(a=NULL, b = NULL, m = NULL, L = 0.1, Ts = 25, Ta = 20, shape="hcylinder") ```

## Arguments

 `a` Coefficient used in calculating Nu. a is normally 1, except for turbulent flow. `b` Coefficient used in calculating Nu. b is 0.58 for upright cylinders, 0.48 for horizontal cylinders. `m` Coefficient used in calculating Nu. m=0.25 for laminar flow. `L` Characteristic dimension in metres. `Ts` Surface temperature in degrees celsius. Used in call to Grashof() function. `Ta` Air temperature in degrees celsius. Used in call to Grashof() function. `shape` "sphere", "hplate", "vplate", "hcylinder", "vcylinder" to denote shape and orientation. h=horizontal, v=vertical. Default shape is "hcylinder"

## Author(s)

Glenn J Tattersall

## References

Blaxter, K. 1989. Energy Metabolism in Animals and Man Gates, DM. 2003. Biophysical Ecology. Dover Publications, Mineola, New York, 611 pp.

## Examples

 ``` 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``` ```## The function is currently defined as function (a=NULL, b = NULL, m = NULL, L = 0.1, Ts = 20, Ta = 20) { Nu <- b * (Grashof(L, Ts, Ta)*Prandtl(Ta)^a)^m Nu } # Nusselt number for free convection # Example calculation: a<-1 b<-0.58 m<-0.25 L<-1 Ts<-30 Ta<-20 Nusseltfree(a,b,m,L,Ts,Ta) # Free convection is higher when surface temperatures are elevated. This is the effect # that free convection predicts: greater molecular energy of air surrounding a warmer surface # leading to air currents over top of a warm surface. Ts<-40 Nusseltfree(a,b,m,L,Ts,Ta) ```

Thermimage documentation built on Nov. 6, 2018, 1:03 a.m.