Page 237 - Handbook of Gold Exploration and Evaluation
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208 Handbook of gold exploration and evaluation
Table 4.3 Relative values of water properties as functions of temperature (after
Dingman, 1984)
Temperature
C p K
ëC
0 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.000
5 1.0001 0.8500 0.8500 0.9907 0.9963 0.9953 1.016
10 0.9986 0.7314 0.7315 0.9815 0.9940 0.9904 1.031
15 0.99926 0.6374 0.6379 0.9932 0.9934 0.9857 1.046
20 0.99836 0.5607 0.5616 0.9630 0.9915 0.9810 1.062
25 0.99720 0.4983 0.4997 0.9524 0.9910 0.9763 1.077
30 0.99580 0.4463 0.4482 0.9418 0.9907 0.9715 1.093
mass density;
weight density; dynamic viscosity; kinematic viscosity;
surface tension; C p heat capacity; latent heat of evaporation; K molecular thermal
conductivity.
where Q S is the rate of movement of matter, momentum, or energy through a
unit area normal to the direction of gradient of mass, momentum, or energy.
ds =dx represents the gradient of mass, momentum, or energy in the x direction.
D S is a diffusion coefficient, or diffusivity for mass, momentum, or energy in the
medium. The term Q is generally called a flux density (flow per unit area per
unit of time). Equations for the specific case of matter are sometimes called
mass-transfer equations. For momentum, the rate of momentum transfer is
proportionate to the viscosity and to the velocity gradient. The gradient of heat
energy depends upon the diffusivity of heat energy in the medium, the heat
capacity of the medium and its temperature.
4.2.3 Gravitational forces in open channel flow
Gravitational forces (including hydrostatic pressure) may be derived in magni-
tude and pressure for fluids at rest and in motion. Due to these two forces, the
elevation of an element of fluid above a horizontal datum will represent its
gravitational potential energy. Expressions derived for the magnitude of
potential energy at any point in a stationary fluid allow gradients of mechanical
potential energy to be computed that will induce flow in open channels. The
relative magnitudes of these and other forces that come into play once flow
commences tend to resist or change the direction of motion. The most important
forces that affect the nature of flow in natural stream channels are due to the
relative proximity of boundary conditions
Hydrostatic pressure
The static water pressure P W exerted against a plane area of surface A under a
fluid of height h is given by the expression:
