Heat exchanger

Properties

The heat exchanger is modelled as a volumetric energy source where the energy transfer between two fluid streams is based on an effectiveness, specified as a function of the mass flow rates.

$$Q_t = e \left(\dot{m}_1 , \dot{m}_2 \right) \left(T_2 - T_1\right) \dot{m}_1 C_p,$$

Where:

$Q_t$ : total heat source

$e(\dot{m}_1,\dot{m}_2)$ : effectiveness table

$\dot{m}_1$ : net mass flux entering heat exchanger [kg/s]

$\dot{m}_2$ : secondary mass flow rate [kg/s]

$T_1$ : primary inlet temperature [K]

$T_2$ : secondary inlet temperature [K]

$C_p$ : specific heat capacity [J/kg/K]

The energy source is distributed across the cells according to:

$$Q_c = \frac{V_c |U_c| (T_c - T_{\ref})}{\sum(V_c |U_c| (T_c - T_{\ref}))},$$

Where:

$Q_c$ : energy source for cell

$V_c$ : volume of the cell [m3]

$U_c$ : local cell velocity [m/s]

$T_c$ : local call temperature [K]

$T_{\ref}$ : min or max(T) in cell zone depending on the sign of $Q_t$ [K]

Optional entries:

• primaryInletT : sets the primary inlet temperature. If not set, the flux-averaged temperature is used
• targetQdot : the secondary inlet temperature is derived from a target heat rejection

Usage

The option is specified using:

heatExchanger1
{
    type            effectivenessHeatExchanger;
    selectionMode   cellZone;
    cellZone        porosity;

    secondaryMassFlowRate   1.0;
    secondaryInletT 336;
    faceZone        facesZoneInletOriented;
    outOfBounds     clamp;
    file            "effTable";

    // Optional
    // primaryInletT 293;
    // targetQdot   1500;
}

The two-dimensional effectiveness table is specified according to, e.g. for the table

	mfr2,1	mfr2,2	mfr2,3
mfr1,1	A	B	C
mfr1,2	D	E	F
mfr1,3	G	H	I

the equivalent entry becomes:

(
    (
        mfr1,1
        (
            (mfr2,1    A)
            (mfr2,2    B)
            (mfr2,3    C)
        )
    )
    (
        mfr1,2
        (
            (mfr2,1    D)
            (mfr2,2    E)
            (mfr2,3    F)
        )
    )
    (
        mfr1,3
        (
            (mfr2,1    G)
            (mfr2,2    H)
            (mfr2,3    I)
        )
    )
);

Further information

Tutorials

• none

Source code

• heatExchangerSource

History: Introduced in version v3.0+