Utilizing Exhaust Air from Heat Recovery Heat Exchanger with air-to-water heatpump

asked 2015-12-02 04:38:51 -0500

OS-user-AT

2274 ●3 ●14 https://mak-analytics.com

updated 2015-12-02 07:26:45 -0500

__AmirRoth__

4436 ●5 ●17 http://bleedinggreenna...

I would like to utilize exhaust air released to outdoors by heat recovery heat exchanger from the air node which is marked in the following image: image description

However, currently EP does not allow taking this air node as an air inlet node for a air-to-water heatpump (water-heater heatpump), because this air node does not belong to any thermal zone. image description

The desired solution would be to supply the air-to-water heatpump with a mixture of outdoor air and the exhaust air from the specified air node.

IS THERE A WAY TO CIRCUMVENT CURRENT EP RESTRICTIONS ?

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answered 2015-12-08 18:52:57 -0500

Lyle K

2216 ●1 ●14 http://www.aeieng.com/

In EnergyPlus, one workaround would involve plotting the hourly conditions (temperature and humidity) from the node you have highlighted to create custom hourly temperature/humidity schedules.

You could then set the 'Inlet Air Configuration' field of the heat pump to 'Schedule' and select the appropriate schedules in the fields 'Inlet Air Temperature Schedule Name' and 'Inlet Air Humidity Schedule Name'. This will allow you to define custom, hourly conditions for the heat pump evaporator coil.

The hourly schedules could be processed to include a mixture of outdoor air and exhaust from the specified air node as needed.

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Thanks. I have also thought of an EMS solution: defining a temperature sensor for the exhaust air, and calculating a temperature schedule for the mixed air supply for the air-to-water heatpump.

OS-user-AT ( 2015-12-09 02:25:36 -0500 )edit

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answered 2015-12-11 01:57:42 -0500

OS-user-AT

2274 ●3 ●14 https://mak-analytics.com

Currently, I see only the option of an (approximate) EMS solution:

Starting with current heating load, one would have to calculate required air flow for the air-to-water heatpump. This however depends on performance curves of heatpump (depending on air side temperatures, and maybe also humidities as well as water side inlet and outlet temperatures). Now the temperature of the supply air will depend on how much exhaust airflow is available for mixing with outdoor air.

These kind of calculations are however not at all trivial. It would probably require to imitate EnergyPlus algorithms to achieve accurate results.

If someone can come up with better recommendations, you are welcome !