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Problem with HeatExchanger:AirToAir:SensibleAndLatent

asked 2018-11-20 08:21:13 -0500

kenny.c's avatar

updated 2018-11-20 08:35:55 -0500


I’m modelling a centralized AHU with heating coil, cooling coil and a heat exchanger in EnergyPlus. My total ventilation rate is 0,3867 m³/s (CAV) for 15 zones. I think there’s something wrong with my heat exchanger (HeatExchanger:AirToAir:SensibleAndLatent) but I don’t know what exactly. When I turn off my heating coil, cooling coil and heat exchanger, the air temperature of the ventilation into the room is slightly above the outdoor drybulb (which is normal). But when I turn on the heat exchanger (while the heating and cooling coils remain off), the air temperature of the ventilation is 20-24°C with an average outdoor drybulb of 5°C. The Sensible Effectiveness of my heat exchanger is 0,85 so normally it should not be possible to heat the air supply temperature from an outside temperature of 5°C to an inside air temperature of 24°C. Am I overlooking something? Thank in advance!

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Also is the effectiveness and efficiency of the heat exchanger the same or is it something different in EnergyPlus?

kenny.c's avatar kenny.c  ( 2018-11-21 07:53:10 -0500 )edit

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answered 2018-12-04 14:47:52 -0500

Is there any recirculated air? My guess is that the HX is conditioning the outdoor air which then mixes with some return air. Use these output variables to see exactly what it happening in the system.

Output:Variable,*,System Node Temperature,hourly; !- HVAC Average [C]
Output:Variable,*,System Node Mass Flow Rate,hourly; !- HVAC Average [kg/s]
Output:Variable,*,System Node Humidity Ratio,hourly; !- HVAC Average [kgWater/kgDryAir]
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Asked: 2018-11-20 08:21:13 -0500

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Last updated: Dec 04 '18