diffuser

Intended flow transformation

Record the design objective and distinguish it from observed performance at a particular operating point.

1. Is the intended duty static-pressure recovery, terminal air distribution or a documented combination? definition
2. What evidence distinguishes this component from a nozzle, grille or ordinary duct transition? boundary

Owned flow path

Identify inlet and outlet stations, integral elements and external equipment responsible for driving the fluid.

1. Where do the diffuser's inlet and outlet boundaries lie, and which vanes or terminal elements belong within them? boundary
2. Which upstream source drives the flow, and does the diffuser itself require power only for adjustment or auxiliary functions? provenance

Area and turning profile

Record area variation, length, wall contours and vane geometry with explicit measurement locations.

1. What are the inlet, minimum and outlet effective areas, passage length and relevant wall angles? measurement
2. Which vanes, slots or internal obstructions alter the available area or flow direction? definition

Installation dependencies

Require evidence for inlet-profile assumptions, mounting orientation and outlet clearances.

1. What approach-flow profile, swirl level and connection arrangement underlie the stated performance? provenance
2. What installation changes are necessary if nearby bends, obstructions or discharge surfaces differ from those conditions? action

Matched flow conditions

Record fluid properties, flow rate and inlet and outlet conditions before applying a performance curve.

1. What fluid composition, temperature, density and mass or volumetric flow define this operating point? measurement
2. What are the inlet Mach and Reynolds numbers and downstream pressure, and which documented analysis regime applies? measurement

Recovery and loss accounting

Keep static and total pressure measurements distinct and document any coefficient definition. [NASA pressure definitions](https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/dynamic-pressure/).

1. What static-pressure rise and total-pressure loss occur between the stated stations? measurement
2. Which averaging method, coefficient normalisation and uncertainty accompany these results? provenance

Terminal delivery

Activate terminal distribution criteria only for applicable HVAC diffuser configurations.

1. At what flow rate, supply-to-room temperature difference and terminal velocity were throw, spread and drop established? measurement
2. Which discharge pattern and acoustic limits must the installed terminal satisfy? boundary

Separation and shock state

Record wall-pressure and velocity evidence for separation and, where applicable, shock behaviour; NASA's transonic diffuser study uses these observations. [NASA transonic diffuser study](https://www.grc.nasa.gov/www/wind/valid/transdif/transdif02/transdif02.html).

1. What measurements indicate separation, reattachment, pressure oscillations or shocks at this operating point? measurement
2. Which verified operating limit or diagnostic rule determines whether adjustment or shutdown is required? action

Geometry control

Identify fixed geometry or documented vane, slot and actuator settings without assuming every diffuser is controllable.

1. Which diffuser elements are adjustable, through what range, and with what position feedback? definition
2. What host-system permissions, interlocks and post-adjustment measurements are required before changing a setting? action

Surface and vane integrity

Record fouling, erosion, corrosion, deformation, leakage and vane damage against an inspected baseline.

1. Where have deposits, wear or damage changed the effective area, surface condition or vane alignment? measurement
2. Which cleaning method, repair limit or replacement criterion is documented for these materials and surfaces? action

Verified performance basis

Require applicable test evidence and identify the issuing body, edition and scope of any standard or certification claimed.

1. Which manufacturer limits and applicable standards govern pressure, temperature, materials, acoustic output or air-distribution testing for this application? provenance
2. What inspection and performance results must be obtained after installation, cleaning or geometry repair before accepting the diffuser? action

Check these first

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these check these first hold for the sense of diffuser this model covers, and on what evidence? provenance

Kinds and varieties

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these kinds and varieties hold for the sense of diffuser this model covers, and on what evidence? provenance

Real-world use

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these real-world use hold for the sense of diffuser this model covers, and on what evidence? provenance

Failure modes and hazards

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these failure modes and hazards hold for the sense of diffuser this model covers, and on what evidence? provenance

Neighbouring kinds and how to tell them apart

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these neighbouring kinds and how to tell them apart hold for the sense of diffuser this model covers, and on what evidence? provenance