Desiccant Process-Airflow Sizing for Deep and Low-Temperature Drying
Sizes a desiccant dehumidifier by the process airflow needed to carry a target water-removal rate across the wheel at the deep grain depression it can hold - the deep / low-temperature and specialty Class 4 drying path the refrigerant sizing never covers, from the same psychrometric mass balance grains-removed uses in reverse. The manufacturer's performance map governs the achievable depression; reactivation air must be ducted outside.
Formula and source
lb_per_hr = required_pints_per_day x 1.043 / 24; process_cfm = lb_per_hr x 7000 / (4.5 x design_grain_depression); units_needed = ceil(process_cfm / nameplate_process_cfm). 4.5 = 60 min/hr x 0.075 lb/ft^3 standard air; 7000 grains/lb; 1.043 lb/pint.
Psychrometric mass balance and the desiccant process-airflow method, by name; ANSI/IICRC S500. The 4.5 / 7000 / 1.043 constants are not edition-bound.
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