The uncertainty in the results will be expressed in two parts, both of which will be based on the uncertainties in various measurements. A pre-test uncertainties analysis is not required for each test covered by this standard because it is recognized that most laboratory tests for rating are conducted in facilities where similar tests are repeatedly run. P Q The fan power output is proportional to the shaded area, which leads to: Efficiency is based on a per-unit basis.ĬALCULO II VICTOR CHUNGARA PDF WOLTER PTE LTD.Ī duct with a measurement plane for airflow determination shall be straight and have a uniform circular cross-section. Multi-point or continuous-record averaging can be accomplished with instruments or analyzers designed for this purpose. Diameter ratio has been omitted in Section 7. The pressure signal can then be transmitted to an indicator.
#Calculo ii victor chungara pdf files ps3#
When the fan discharges into a duct with a Pitot traverse, total pressure Pt2 shall be considered equal to the sum of the average static pressure Ps3 and the velocity pressure Pv3 corrected for the friction loss due to both the equivalent length Le of the straightener and the length L2,3 of the duct between the fan outlet and the measurement plane.Ī complete set of measurements for a particular point of operation of a fan. A total pressure tube is sensitive only to the pressure in the immediate vicinity of the open end. Generally, several screens in each airflow settling means will be required. The nozzle shall have a cross-section consisting of elliptical and cylindrical portions, as shown. This constant is derived by converting to the SI equivalent units: A flow nozzle without an integral throat tap may be used in a multiple nozzle chamber, in which case, upstream and downstream pressure taps shall be located as shown in the figure for the appropriate setup. Groups approve laboratory methods for testing fans. The velocity pressure at a point shall be measured on an indicator such as a manometer with one leg open to a total pressure sensor, such as the impact tap of a Pitot-static tube, and the other leg connected to a static pressure sensor such as the static tap of the same Pitot-static tube.įor the test, positions around the periphery of the jets and slightly upstream of the settling means shall be scanned for reverse velocities. In each case, the difference between the two readings shall be within 0.
Other factors may have an equal or greater effect on fan performance. This is generally acceptable because fans are not usually rated at the low pressure or low flow portions of their characteristic curves. The coefficient of friction f shall be determined from : A leakage test should be performed prior to initial use and periodically thereafter, with corrective action taken if necessary. The procedure is to pressurize or evacuate the test chamber and use a flow meter to establish the leakage flow rate.
Each pressure tap shall conform to the requirements in Section 4. The minimum distance between the centers of any two nozzles in simultaneous use shall be three times the throat diameter of the larger nozzle. During a laboratory test, the air density and rotational speed may vary slightly from one determination point to another. The description of the test fan shall be recorded. The specification permitting an uncertainty based on the maximum observed test reading during the test leads to combined relative uncertainties in both fan pressure and fan airflow rate that are higher at low values of the fan pressure or fan airflow rate than at high values of those test results.Ī torque measurement device shall have a static calibration and may have a running calibration through its range of use. If a portion of the internal energy is converted into kinetic energy, the static temperature is decreased accordingly. and Air-Conditioning Engineers (ASHRAE) approved ANSI/AMCA Standard ANSI/ASHRAE Standard, Laboratory Methods of Testing Fans for. Standard - Laboratory Methods of Testing Fans for Aerodynamic Performance Rating (ANSI/AMCA Standard ) (ANSI/ASHRAE Approved). Standard and ANSI/ASHRAE Standard 51, except as modified by Units shall be tested in accordance with ANSI/AMCA Standard /ANSI/ASHRAE.
0 kommentar(er)
