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2. Ductwork airtightness - Wikipedia

   en.wikipedia.org/wiki/Ductwork_airtightness

   The ductwork airtightness level is the airflow rate through ductwork leakages divided by the ductwork area. It is recommended to test at least 10% and 10 m 2 of the duct surface including all duct types and a variety of sizes and components. The ductwork surface area is estimated according to EN 14239. [11]

3. Duct (flow) - Wikipedia

   en.wikipedia.org/wiki/Duct_(flow)

   Some flexible duct markets prefer to avoid using flexible duct on the return air portions of HVAC systems, however flexible duct can tolerate moderate negative pressures. The UL181 test requires a negative pressure of 200 Pa. To use flexible ducting in a system, make sure to pull the duct tight so you get the full internal diameter.

4. Duct leakage testing - Wikipedia

   en.wikipedia.org/wiki/Duct_leakage_testing

   Duct leakage test in the US. A duct leakage tester is a diagnostic tool designed to measure the airtightness of forced air heating, ventilating and air-conditioning (HVAC) ductwork. A duct leakage tester consists of a calibrated fan for measuring an air flow rate and a pressure sensing device to measure the pressure created by the fan flow.

5. Diffuser (thermodynamics) - Wikipedia

   en.wikipedia.org/wiki/Diffuser_(thermodynamics)

   A supersonic diffuser is a duct that decreases in area in the direction of flow which causes the fluid temperature, pressure, and density to increase, and velocity to decrease. These changes occur because the fluid is compressible. Shock waves may also play an important role in a supersonic diffuser.

6. Friction loss - Wikipedia

   en.wikipedia.org/wiki/Friction_loss

   The friction loss is customarily given as pressure loss for a given duct length, Δp / L, in units of (US) inches of water for 100 feet or (SI) kg / m 2 / s 2. For specific choices of duct material, and assuming air at standard temperature and pressure (STP), standard charts can be used to calculate the expected friction loss.

7. Building airtightness - Wikipedia

   en.wikipedia.org/wiki/Building_airtightness

   [1] [6] [7] The ASIEPI project technical report on building and ductwork airtightness estimates the energy impact of envelope airtightness in the order of 10 kWh per m 2 of floor area per year, for the heating needs in a moderately cold region (2500 degree-days). [1]