Dear Trnsys users, I Have a question about the indirect evaporative
cooler type 757 from TESS library. I do a very simple simulation with type 757, I just
put parameters in entrance and see the results. If I put the same air flow rate in the primary stream
and in the secondary stream, I get coherent results, the exchange of power
between the two flows is the same. Now, if I put a little air flow rate for the
secondary stream (10 times under the primary air flow rate), the air outlet
temperature in secondary stream decreases, but the air outlet temperature in
the primary stream doesn’t change as it seems that this outlet
temperature only depends on the efficiency, which is based on the primary air
inlet dry bulb temperature and the secondary air inlet wet bulb temperature and
these two parameters does not change if we only change the secondary air flow
rate. Thus, the power change in the primary stream is not
equal to the power change in the secondary stream (calculs below). Is it a voluntary simplification of the model?
Shouldn’t the primary air outlet temperature change to balance the
exchange of power? I thank you in advance. Best Regards, Benjamin BROTTES Nota: I have these parameters : 1 : Primary-stream,in 2 : Primary stream, out 3 : Secondary stream,in 4 : secondary stream, out 1 : T1 = 2 : (trnsys results) T2 = 27.18°C ; HR2 =
47.12% ; h2 = 54.22 kJ/kg 3 : T3 = 4 : (trnsys results) T4 =
T4 = I calculate : Q1 = m1.(h1-h2) = 252 * (57.59-54.22) = 849 kJ/hr Q2 = m2.Cp.(T3-T4) + m2.Lv.(w4-w3) =
252*1.005*(30-28.31) + 252*2432*(0.014-0.01331) = 428 + 551 =
979kJ/hr if m2 =
252 kg/hr = 25.2*1.005*(30-21.99) +
25.2*2432*(0.01664-0.01331) = 202 + 217 = 419 kJ/hr if
m2 = 25.2kg/hr which is very far from 849 kJ/hr |