ERV Total Enthalpy Recovery
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). Feed enthalpies from moist-air-enthalpy. The ERV's rated effectiveness governs.
Formula and source
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.
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