SectionsHygienic air handling units
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Hygienic air handling units

Hygienic execution makes the required cleanliness possible to achieve, inspect and maintain. The room duty determines the actual filtration, leakage and verification requirements.

Principle and scope

Hygienic execution addresses cleanability, drainage, access, suitable internal surfaces, sealed filter mounting and controlled leakage. It is a construction and verification requirement that can apply to different airflow and treatment arrangements.

Define the room risk, pressure relationships, filtration stages and cleaning procedure. Fine-particle or high-efficiency filtration does not make a complete installation suitable for a cleanroom or clinical process by itself. The project needs the required performance evidence and commissioning results.

Cleanability and evidence

Specify accessible surfaces, drainability, compatible cleaning agents, filter sealing and inspection provisions. Separate a tested casing or component claim from evidence for the supplied assembly. Record which specification and edition apply to the project and which tests or inspections verify them. An AHU label alone does not validate room cleanliness.

Related components: Air filter

Calculate only the sensible air duty. The result does not confirm hygienic execution, cleanliness, filtration or certification.

Calculate sensible air load

Sensible air load calculation

Calculate the heat rate associated with a specified temperature change in one air stream. Enter all five values for your stated operating conditions.

Mass flow ṁ = ρ × V̇ / 3600; temperature change ΔT = Tout − Tin; sensible heat rate Q̇ = ṁ × cp × ΔT. With the units below, the result is in kW. Positive Q̇ means heating; negative Q̇ means cooling. Zero flow or zero temperature difference gives zero sensible load.

For a steady, single-phase air stream with constant user-supplied properties. The balance excludes latent heat, moisture changes, phase change, shaft work and kinetic/potential energy changes. It does not select a fan, coil or complete AHU.

Topic for the local draft

Opening a page does not select anything. A topic choice records context only; no product or configuration is selected.

Operating inputs

Use density at the same state and volume basis as the entered airflow. Enter cp in kJ/(kg·K), not J/(kg·K). Density and cp are editable assumptions; no universal values are prefilled. Check that your temperatures and properties describe gas-phase air. This tool does not check phase boundaries or property-table consistency.

Interactive calculation requires JavaScript. The formula, units, scope and reference information remain available here for manual use.

Modular

Modularity can provide useful access and section choice for a hygiene specification. It also creates joints that must remain sealed and cleanable after transport and site assembly. Require the evidence and inspection plan to cover those joints, the final section schedule and the supplied revision.

Direct expansion

Hygienic DX treatment requires both refrigeration compatibility and cleanable wet-coil construction. Specify the drain pan, droplet control where needed, inspection access and cleaning method. Stable humidity or room cleanliness cannot be inferred from the presence of a DX coil.

Related components: Direct-expansion coil · Condensate drainage

Commissioning and service

Commission the required pressure relationships, filters and drain functions; retain the prescribed verification records. Maintenance must preserve cleanliness during access and restore filter seals and access-panel tightness. Replacing a filter with a nominally similar size does not prove equivalent filtration or sealing.

Related components: Air filter · Condensate drainage

UPGR sectional AHU with a partly withdrawn finned coil, copper headers and a removable access panel.

Access to a finned coil in a sectional AHU. Reserve space for removing the access panel and handling the coil; the actual removal procedure follows the equipment documentation.

Access opening
Provides access to the coil section.
Finned coil
The removable assembly must fit through the access opening and be handled with suitable support.
Headers and connections
Check disconnection requirements and available service space before removal.
Back to section: Hygienic execution

A guide to equipment and selection; the final configuration and performance require project-specific confirmation.