.ScalableTestSuite.Thermal.HeatExchanger.Models.CocurrentHeatExchangerEquations

Information

Cocurrent heat exchanger model consist of two channels A and B, and a separating heat transfer wall in between. Fluids A and B are flowing in the channels A and B respectively. Heat exchanger is assumed to be insulated around the outside, therefore, heat transfer occurs just between the fluids A and B. Fluid B is considered as the hot fluid and fluid A is considered to be the cold fluid.

Heat exchanger mass balance equations for the fluids can be written as:

where ρ is the density of the fluid, A is the cross section and w is the mass flow rate. Density and the cross section are assumed to be constant for the fluids, hence mass flow rate is considered constant along the channels.

Heat exchanger energy balance equations are described considering a small portion l=L/(N-1) on the channels where L is the length of each channel, and N is the number of nodes on the channels. Therefore, N-1 corresponds to the number of channel and wall segments. And, there are N-1 heat flow rates and N-1 temperature variables for the wall which are considered for the segments.

Energy balance equations for cocurrent heat exchanger is very similar to the equations of countercurrent heat exchanger. The difference occurs because of the flow direction of the fluid B, therefore, in cocurrent heat exchanger boundary condition of T_B is described for the first node. And, boundary condition of T_A remained again for the first node.

for j=1…N-1. Energy balance at the each wall segment is modified in terms of temperature variables of fluid B:

for j=1…N-1.

Parameters in the CounterCurrentHeatExchangerEquations:

Parameters Comment
L length of the channels
N number of nodes
wB mass flow rate of fluid B
areaA cross sectional area of channel A
areaB cross sectional area of channel B
rhoA density of fluid A
rhoB density of fluid B
cpA specific heat capacity of fluid A
cpB specific heat capacity of fluid B
cpW specific heat capacity of the wall
gammaA heat transfer coefficient of fluid A
gammaB heat transfer coefficient of fluid B
omega perimeter
l length of each wall segment

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