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 usedtargetQdot
: the secondary inlet temperature is derived from a target heat rejectionThe 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) ) ) );
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