Desiccant Process-Airflow Sizing for Deep and Low-Temperature Drying

ScopeSizes 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 manufacturer's performance map governs the achievable depression; reactivation air must be ducted outside.

Formula or tablelb_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.

Source and editionPsychrometric mass balance and the desiccant process-airflow method, by name; ANSI/IICRC S500. The 4.5 / 7000 / 1.043 constants are not edition-bound.

Free accessThe same psychrometric mass balance the grains-removed tile uses, in reverse: process airflow carries the water-removal rate across the wheel at the design depression.

What governsEstimate. AHJ and licensed professional govern.

API field namesrequired_pints_per_day, design_grain_depression, nameplate_process_cfm, lb_per_hr, process_cfm, units_needed

• Standard air 4.5 lb/hr per cfm per (grains/lb/7000) = 60 min/hr x 0.075 lb/ft^3 standard air densitypure-math.js convention
• Constants 7000 grains/lb, 1.043 lb/pint water densitypure-math.js convention
• Achievable depression the manufacturer's performance map governs the inlet->outlet grain depression; reactivation exhaust air must duct outsidemanufacturer performance map