DOE-2 Reference Manual Version 2.1 - DOE2.com

. Outside Air Flow RateIf OUTSIDE-AIR-CFM is defined, it is taken as the amount of ventilation airfor that zone. Otherwise, the program takes the larger of (OA-CHANGES) x(lone Volume)/60 min. per hr. and (OA-CFM/PER) x number of people as the amountof ventilation air for the zone. If these are not specified at the zone levelfor zonal systems, the program mUltiplies the MIN-OUTSIDE-AIR fraction timesthe zone CFM to arrive at a value of the ventilation air for the design calculation.During the simulation, the MIN-AIR-SCH will also be operative; it isignored for the design calculation and the other specifications are used.For central systems the design outside air ratio is taken to be the valueof (a) MIN-OUTSIDE-AIR, (b) the ratio of the sum of the zone ventilation airto the SUPPLY-CFM, or (c) the ratio of the sum of the zone exhaust air to theSUPPLY-CFM. In other words, if the user enters EXHAUST-CFM at the zone leveland leaves out all other references to outside air, the program will stillcreate an outside air ratio adequate to account for the exhausted air. lonelevel specifications take precedence over SYSTEM level MIN-OUTSIDE-AIR.The last consideration with regard to the air supply is the minimum cfmratio associated with variable air volume systems. If for zonal systemsMIN-CFM-RATIO is not defined at the zone level, the value of MIN-CFM-RATIOdefined at the system level is assumed to apply to the units located in eachzone. If MIN-CFM-RATIO is not specified, it is calculated as the larger of(a) the minimum cfm ratio needed to account for the ventilation and (b) theminimum cfm ratio needed to meet the heating requirements. If theMIN-CFM-RATIO is specified as less than the value specified for outside air(exhaust or ventilation), a 100 per cent outside air variable air volumesystem is simulated below the minimum outside air point.c. Heating and Cooling Capacities and Extraction RatesIf the user has specified the HEATING-CAPACITY, the input value is adjustedfor off-rated cfm using the RATED-CFM value and the RATED-HCAP-FCFM function.This adjustment factor is 1.0, if the keyword RATED-CFM is not entered. Theheat addition rate, printed in the VERIFICATION report SV-A, is computed fromthis heating capacity, using the conditions at the peak heating load to subtractthe ventilation load. The heat addition rate shown in SV-A includes thebaseboard heating rate, in addition to the air system heating rate.If the user has not specified the HEATING-CAPACITY, the heat addition rateis computed from MAX-HE AT-RATE or the peak heating load, while theHEATING-CAPACITY, which includes the ventilation load, is computed from (a)the airflow rate, (b) the temperature of the mixed return air and outsideventilation air, and (c) the off-coil air temperature, based on the conditionsat the peak heating load. The user should know that the value of the heataddition rate printed in SV-A iSSfi"own for TITUstratfv-e-purposesonly.---rIleactual heat addltlon rate-rs-carculated anew each hour durlng the SlmulatlOn.The situation for cooling is similar, except that the program must treatthe water balance in the air (both return air and outside ventilation air), inaddition to the sensible cooling load. Again, the weather conditions at thetime of the cooling peak loads are used in the calculation of the total andIV.302 (Revised 5/81)