ERV Total Enthalpy Recovery
The total heat an energy-recovery ventilator saves, and the enthalpy of the air it hands the coil.
Example
You enter
- Ventilation airflow through the ERV (cfm) 1000
- Enthalpy (total-energy) effectiveness (0-1) 0.75
- Outdoor-air enthalpy (Btu/lb) 38
- Return/exhaust-air enthalpy (Btu/lb) 28
You get
- Total energy recovered 33750 Btu/hr (cooling recovery)
- Supply-air enthalpy leaving the wheel 30.50 Btu/lb
Details, formula, and sources
Q = 4.5 x CFM x effectiveness x (h_oa - h_ra), supply enthalpy = h_oa - eff x (h_oa - h_ra). 1000 CFM, 0.75, 38 -> 28 Btu/lb -> 33,750 Btu/hr recovered, 30.5 Btu/lb supply; a winter 12 vs 28 Btu/lb recovers -54,000 Btu/hr (heating). Enthalpies come from a moist-air psychrometric calculation. The ERV's rated effectiveness governs.
Q = 4.5 x CFM x effectiveness x (h_outdoor - h_return); h_supply = h_outdoor - effectiveness x (h_outdoor - h_return).
The energy-recovery-ventilator total (enthalpy) recovery relation (ASHRAE Handbook - Fundamentals / AHRI 1060 effectiveness), by name.
The 4.5 x CFM x effectiveness x enthalpy-difference total-recovery relation is a standard published air-side result; the effectiveness is the AHRI 1060 rating.
Estimate. AHJ and licensed professional govern.
Field names used by the API: cfm, effectiveness, h_outdoor, h_return, q_total_btuh, h_supply
- Total recovery Q = 4.5 x CFM x effectiveness x (h_oa - h_ra)ASHRAE Fundamentals
- Supply state h_supply = h_oa - effectiveness x (h_oa - h_ra)definition of effectiveness
- Rated effectiveness the AHRI 1060 total-energy effectiveness at design airflowscope of this tile