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Hİ,

I’m developing a small ventilation unit with a ceramic regenerative core and want to test it and validate the sensible effectiveness calculation. The unit runs a 10-minute cycle in two sequential phases with only one fan operating at a time, then they swap:

Phase 1 (5 min): Fan A runs, pulling indoor → outdoor to charge the core with heat (Fan B is off).

Phase 2 (5 min): Fan A stops; Fan B runs, pulling outdoor → indoor through the hot core to deliver heat to the room.

Looking for community opinions on:

Best practice to compute sensible effectiveness for alternating-flow regenerators.

Whether effectiveness should be computed only during the supply half-cycle (Phase 2) using time-synchronous measurements, e.g. eta_s(t) = (T_supply_out(t) - T_outdoor_in(t)) / (T_indoor_in(t) - T_outdoor_in(t)) and then averaged over Phase 2 (time-weighted or mass-weighted if flow is known).

Any references or standards you recommend (papers/lab standards).

Variables for clarity:

T_indoor_in: Air temperature at the indoor inlet (room return)

T_outdoor_in: Air temperature at the outdoor inlet

T_supply_out: Supply air temperature to the room (exists in Phase 2 only)

I can share if helpful: sensor placements, raw time series for both phases, fan PWM/flow data,

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  • $\begingroup$ Looking for community opinions on: ... this site is not for soliciting opinions, it is a question and answer site ... please add a focused, answerable question to your post $\endgroup$ Commented Sep 24 at 18:38
  • $\begingroup$ Fan A runs, pulling indoor → outdoor to charge the core with heat ... that is only a part of Phase 1 $\endgroup$ Commented Sep 25 at 17:28
  • $\begingroup$ "effectiveness" is not a specification. The most "effective" solution would be 2 fans the size of houses and a heat exchanger sized to match. $\endgroup$ Commented Sep 29 at 15:32

1 Answer 1

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Compute instantaneous sensible effectiveness only when the core is delivering supply air to the room (Phase 2) using a time-synchronous definition that matches the usual “effectiveness” concept (how close supply approaches indoor temperature). Then form a cycle-averaged effectiveness by mass-weighted integration over the supply half-cycle. This matches how standards treat rotary/regenerative devices: performance is reported from the delivered heat during the delivery half-cycle and integrated over the test interval.

https://www.ashrae.org/file%20library/technical%20resources/standards%20and%20guidelines/standards%20addenda/84_2013_a_final_08012013.pdf

Also check energy balance over the full cycle.

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