Thermimage (version 2.1)

qconv: Estimates the area specific heat transfer by convection (W/m2)

Description

Estimates heat transfer by convective heat exchange, using the heat transfer coefficient estimate, surface temperature, and air temperature. Positive value = heat gain from air to object. Negative value = heat loss from object to air.

Usage

qconv(Ts = 30, Ta = 20, V = 1, L = 0.1, c = NULL, n =NULL, a=NULL, b = NULL, m = NULL, 
type = "forced", shape="hcylinder")

Arguments

Ts

Surface temperature (degrees celsius). Default value is 30.

Ta

Air temperature (degrees celsius). Default value is 20.

V

Air velocity (m/s). Default value is 1.

L

Characteristic dimension (m) of object. Usually the vertical dimension (i.e. height). Default value is 0.1.

c

coefficient used in forced convection (see Blaxter, 1986, default value is 0.24)

n

coefficient used in forced convection (see Blaxter, 1986, default value is 0.6)

a

coefficient used in free convection (see Gates, 2003. default value is 1)

b

coefficient used in free convection (0.58 upright cylinder, 0.48 flat cylinder, default value is 0.58)

m

coefficient used in free convection (0.25 laminar flow, default value is 0.25)

type

"forced" or "free" - to calculate convection coefficient for either forced or free convection. Default value is "forced"

shape

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

Details

Estimates an area specific rate of heat transfer (W/m2), where a negative value depicts heat loss from surface to air, while positive value depicts heat gain from air to surface. Uses the gradient in temperature (Ta minus Ts) multiplied by a convection coefficient to estimate heat transfer from a surface. Designed for estimating steady state heat exchange from animal surfaces using thermal images.

References

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

See Also

hconv

Examples

## The function is currently defined as
function (Ts = 30, Ta = 20, V = 1, L = 0.1, c = NULL, n = NULL, a=NULL,
    b = NULL, m = NULL, type = "forced", shape="hcylinder") 
{
    qconv <- (Ta - Ts) * hconv(Ta = 20, V = 1, L = 0.1, c = NULL, n = NULL, a=NULL,
    b = NULL, m = NULL, type = "forced", shape="hcylinder")
    qconv
  }

# Example:
Ts<-30
Ta<-20
V<-1
L<-0.1
type="forced"
shape="hcylinder"

qconv(Ts=Ts, Ta=Ta, V=V, L=L, type=type, shape=shape)

qconv(Ts=Ts, Ta=Ta, V=V, L=L, type=type, shape="sphere")