Cleanroom air-conditioning loads cannot be estimated using the per-unit-area indices for comfort air conditioning. Cleanroom supply air volume is often determined first by cleanliness class, air changes per hour, or face velocity, and is frequently greater than the air volume needed to satisfy only the sensible and latent loads; the outdoor air volume should be taken as the greater of "exhaust air plus positive-pressure makeup" and "40 m³ per person per hour" in accordance with GB 50073-2013, rather than adding the per-person outdoor air on top again. Reheat is not for reaching the apparatus dew point; rather, after the air has been overcooled to condense moisture, it restores the supply air temperature. Heat dissipation from process equipment, fan temperature rise, and positive-pressure makeup air volume must all be calculated as separate items; otherwise the unit is easily oversized or undersized.
Air-conditioning load is the amount of heat that must be removed from the room per unit time (cooling load) to maintain the indoor temperature and humidity parameters within the required range, or the amount of heat that must be supplied to the room under heating conditions (heating load). This definition holds for both comfort air conditioning and cleanroom air conditioning. The difference lies in this: the control objectives differ, and so do the items that account for the bulk of the load.
Below, load calculation and system design are separated into two lines of approach. Clauses involving outdoor air volume and pressure differential are checked against GB 50073-2013; any proportional figures appearing in the text that have no source in a standard serve only as commonly observed ranges in engineering practice, not as specified values that must be met or must not be exceeded.
How is the supply air volume of a cleanroom determined? Why is it often not calculated from the cooling load?
Comfort air conditioning mainly governs temperature, h