ASHRAE+62.1-2022+(1) - Page 050
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(This appendix is not part of this standard. It is merely informative and does not contain requirements necessary for conformance to the standard. It has not been processed according to the ANSI require- ments for a standard and may contain material that has not been subject to public review or a consen- sus process. Unresolved objectors on informative material are not offered the right to appeal at ASHRAE or ANSI.)
INFORMATIVE APPENDIX F ACCEPTABLE MASS-BALANCE EQUATIONS FOR USE WITH THE IAQ PROCEDURE
When applying the Indoor Air Quality Procedure from Section 6.3, mass-balance analysis may be employed to determine outdoor air ventilation requirements to control concentrations to meet design targets.
Table F-1 presents mass-balance equations for analysis of single-zone systems. Figures F-1 and F-2 show representative single-zone systems. A filter may be located in the recirculated airstream (location A) or in the supply (mixed) airstream (location B). The equations do not account for sources within the HVAC system that may occur, such as filter off-gassing, energy recovery carryover of specific gases, or generation of particles or compounds.
VAV single-zone systems reduce the circulation rate when the thermal load is lower than the design load. This is accounted for by a flow reduction fraction ( Fr ).
A mass-balance equation for each design compound or PM2.5 may be written and used to determine the required outdoor airflow or the breathing zone resultant concentration for the various system arrangements. Six permutations for air-handling and single-zone air distribution systems are described in Table F-1. The mass-balance equations for computing the required outdoor airflow and the breathing-zone contaminant concentration at steady-state conditions for each single-zone system are presented in Table F-1.
If the allowable breathing zone design target is specified, the equations in Table F-1 may be solved for the zone outdoor airflow rate ( Voz ). When the zone outdoor airflow rate is specified, the equations may be solved for the resulting breathing zone design compound or PM2.5 concentration.
While the calculation methods in this appendix are based on single-zone systems and steady-state analysis, calculation methods that account for multiple-zone and transient effects are also available (see Dols and Walton [2002] in Informative Appendix P).
Table F-1 Required Zone Outdoor Airflow or Space Breathing Zone Contaminant Concentration with Recirculation and Filtration for Single-Zone Systems
Required Recirculation Rate
Filter Outdoor Required Zone Outdoor Airflow Space Breathing Zone Location Flow Airflow ( V in Section 6) Contaminant Concentration
Outdoor
Airflow
Required Zone Outdoor Airflow
( Voz in Section 6)
None VAV 100%
A Constant Constant
A VAV Constant
B Constant Constant
B VAV 100%
B VAV Constant
N
Voz = ------------------------------------------------------------ EzFr Cbz - 1 - Ef Co Cbz
Voz = ----------------------------------------------------- EzN C - bzE - zF 1 rRV - ErEf f CCbzo - Cbz
Voz
Voz
N N = E ------------------------------------ zFr Cbz - Co Cbz = Co + ----------------- EzFrVoz -
= N ------------------------------------- E - z ECzRVbz - rECfoC bz - Cbz
= --------------------------------------- N + EzVozCo Ez Voz + RVrEf
= ------------------------------------------- N + EzVozCo - Ez Voz + FrRVrEf
Voz
= -------------------------------------------- N - EEz zCFbzrRV - CrEof Cbz Cbz
= ------------------------------------------------- N + EzVoz 1 - Ef Co Ez Voz + RVrEf
= N -----------------------------------------------------+ EzFrVoz 1 - Ef C - o EzFrVoz
= ------------------------------------------------- N + EzVoz 1 - Ef Co Ez Voz + FrRVrEf
Voz
= ----------------------------------------------------- Ez NCbz - - Ez RV 1 - rEEffC bzCo - Cbz
48 ANSI/ASHRAE Standard 62.1-2022