# HydroGeoSphere/Heat Transfer

To enable heat transfer, you must define the temperature species in the solute definition block as described in Section 5.6.3.1. Note that the unit for temperature must be °C and that all heat transfer properties must be given in the SI-units kilogram-meter-second-Celsius. The thermal properties of the solids are specified in the material property file. The following instructions can be used to control the heat transfer solution:

## Do heat transfer...End edit

Causes **grok** to begin reading a group of heat transfer instructions until it encounters an End instruction.

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The available instructions are:

## Thermal conductivity of water edit

**k_l**[W L^{−1}K^{−1}] Thermal conductivity of the liquid phase.

Assigns a uniform value to the thermal conductivity of groundwater. If this instructions is used, the thermal conductivity of water is assumed constant and equal to . It is therefore not calculated from the water temperature, which is the default setting.

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## Specific heat capacity of water edit

**c_l**[J kg^{−1}K^{−1}] Specific heat capacity of the liquid phase.

Assigns a uniform value to the specific heat capacity of water. If this instructions is used, the specific heat capacity of water is assumed constant and equal to . It is therefore not calculated from the water temperature, which is the default setting.

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## Mechanical heat dispersion edit

Causes mechanical heat dispersion to be simulated. The default is no mechanical heat dispersion.

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The following instruction can be used to define initial temperatures for the problem:

## Initial temperature profile edit

**temp_top**[°C] The temperature at the top of the domain.**temp_grad**[K m^{−1}] The prevailing geothermal gradient.

Calculates a depth profile of temperature and assigns the values to the initial temperature.

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The following instructions can be used to define the heat source boundary condition:

## Zero order source edit

**npanel**Number of panels in the time-variable, zero-order source function. For each panel, enter the following:

- (a)
**ton_val,toff_val, (bc val(j),j=1,nspeciesmob)**Time on [T], time off [T] and mass of solute produced per unit volume of porous medium solids per unit time [M L^{−3}].

- (a)

Nodes in the chosen zones area assigned zero-order source boundary conditions.

A panel is a point in time at which the source term is set to a new value. The first panel would normally start at time zero. The source term given for the last panel will be maintained until the end of the simulation. You can assign a static source term for the duration of the simulation by setting **npanel** to 1, **ton_val** to 0.0 and **toff_val** to a large number.

Note that if **nspeciesmob** is greater than 1, additional values of **bc_val** should be included.

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## Exponential zero order source edit

**heat_q_zero**Heat production at*t*= 0.**heat_constant**Constant in the exponential function.

Nodes in the chosen zones area assigned an exponentially decreasing zero-order heat source boundary conditions.

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