Campbell HFP01SC Manual de usuario descargar pdf (Pagina 28)

Model HFP01SC Self-Calibrating Soil Heat Flux Plate

6. Soil Heat Flux and Storage

The soil heat flux at the surface is calculated by adding the measured flux at a

fixed depth, d, to the energy stored in the layer above the heat flux plates. The

specific heat of the soil and the change in soil temperature, ∆T

, over the

output interval, t, are required to calculate the stored energy.

The heat capacity of the soil is calculated by adding the specific heat of the dry

soil to that of the soil water. The values used for specific heat of dry soil and

water are on a mass basis. The heat capacity of the moist is given by:

()

CCCC

sbdmw bdvw

=+ =+ρθ ρθρC

(1)

= (2)

where C

is the heat capacity of moist soil, ρ

is bulk density, ρ

is the density

of water, C

is the heat capacity of a dry mineral soil, θ

is soil water content

on a mass basis, θ

is soil water content on a volume basis, and C

is the heat

capacity of water.

This calculation requires site specific inputs for bulk density, mass basis soil

water content or volume basis soil water content, and the specific heat of the

dry soil. Bulk density and mass basis soil water content can be found by

sampling (Klute, 1986). The volumetric soil water content is measured by the

CS616 water content reflectometer. A value of 840 J kg

-1

for the heat

capacity of dry soil is a reasonable value for most mineral soils (Hanks and

Ashcroft, 1980).

The storage term is then given by Eq. (3) and the soil heat flux at the surface is

given by Eq. (4).

TCd

∆

(3)

sfc cm

= S

(4)

7. Maintenance

The HFP01SC requires minimal maintenance. Check the sensor leads monthly

for rodent damage.

8. In-Situ Calibration Theory

For detailed information on the theory of the in-situ calibration, see the Theory

section of the Hukseflux manual or visit the application section of the

Hukseflux web site at

http://www.hukseflux.com/heat%20flux/applic&spec.pdf.

Equation 6 in the Hukseflux manual is used to compute a new calibration every

three hours. The heater is on for a total of 180 seconds. Table 7 lists the

1 2 ... 23 24 25 26 27 28 29 30 31 32

Comentarios a estos manuales

Sin comentarios

Campbell HFP01SC Manual de usuario Pagina 28

Comentarios a estos manuales

Relacionado con productos y manuales para De medición, control y control Campbell HFP01SC