Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
After some investigative simulations, reading the Engineering Reference and the I/O Reference multiple times, I realised that the descriptions in the documentations were a bit misleading and resulted in a wrong assumption on my side.
Basically the output Baseboard Total Heating Rate is not the the total system output power, as a sum of the radiant and convective heating:
Baseboard Total Heating Rate ≠ Baseboard Radiant Heating Rate + Baseboard Convective Heating Rate
but rather the total heating rate that actually reaches the zone (directly or indirectly) via convection and is equal to equation 15.734 (Engineering Reference):
Baseboard Total Heating Rate = q_req = (q_surf,c - q_surf,z) + q_conv + q_people
where (q_ surf,c - q_ surf,z) is the heating which gets actually delivered to the zone through convection at the surfaces after being absorbed by the wall. This is only a fraction of Baseboard Radiant Heating Rate (q_ rad) which gets absorbed by specified surfaces of the zone – the remainder gets either conducted through the wall, stored in the wall (q_ cond) or re-emitted by radiation to other walls ( q_ reflec):
(q_surf,c - q_surf,z) = q_rad - (q_cond + q_reflec)
So:
Baseboard Electricity Rate = q / efficiencyBaseboard Radiant Heating Rate: q_ rad = q * Frac_ radBaseboard Convective Heating Rate q_ conv = q * (1 - Frac_ rad)Baseboard Total Heating Rate (should better be called "Baseboard Total Zone Heating Rate"):
q_ req = (q_ surf,c - q_ surf,z) + q_ conv + q_ people
