ASHRAE 51-07 PDF
Standard and ANSI/ASHRAE Standard 51, except as modified by Units shall be tested in accordance with ANSI/AMCA Standard /ANSI/ASHRAE. Standard — Laboratory Methods of Testing Fans for Aerodynamic Performance Rating (ANSI/AMCA Standard ) (ANSI/ASHRAE Approved). and Air-Conditioning Engineers (ASHRAE) approved ANSI/AMCA Standard ANSI/ASHRAE Standard , Laboratory Methods of Testing Fans for.
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Connecting tubing to pressure indicator shall be 6 mm 0.
Groups approve laboratory methods for testing fans.
A transducer type barometer shall be calibrated for each test. When the mean of these readings is less than or equal to Pa 4 in. When the fan discharges into a duct with a Pitot traverse, total pressure Pt2 shall be considered equal ashraf 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.
However, that evidence is not ashare sufficiently documented to incorporate any rules in this Annex. Dotted lines on fan inlet indicate an inlet bell and one equivalent duct diameter which may be used for inlet duct simulation. Complete dynamic similarity requires that the ratios of all corresponding forces in the two fans be equal.
The axes of the fan opening and duct shall coincide. A static pressure tap meeting the requirements shown in Figure 2A is considered a primary instrument and need not be calibrated provided it is maintained in a condition conforming to this standard. Calibration correction need not be made if the correction is smaller than one-half the maximum allowable uncertainty, as specified in Section 4. The nozzle throat shall be measured to an accuracy of 0.
There is some evidence that efficiency improves with an increase in Reynolds number. Continue to record until the pressure reaches a state in which the pressure does not change significantly.
In addition, an allowance must be made for the mental averaging which is performed on fluctuating readings. The downstream ashraee is the integral throat tap 7 4. This test evaluates the ability of the airflow settling means to provide a substantially uniform airflow ahead of the measurement plane.
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The fan may be tested without outlet duct in which case it shall be mounted on the end of the chamber. Minimum M is determined by the requirements Section of 5.
Asnrae, for some unusual conditions, the iterations do not converge, then try a different starting initial guess for C e. When the fan is connected to an inlet duct, Pt1 shall be considered equal to the algebraic sum of the average static pressure Ps3 and the average velocity pressure Pv3corrected for the asshrae due to the length of duct L1,3 between the measurement plane and the fan, so that: A friction-driven counter shall not be used when it can influence the rotational speed due to drag.
Groups approve laboratory methods for testing fans.
The coefficient of friction f shall be determined from : The manifold shall have an inside area at least four times that of each tap. The smallest division on the scale of such an instrument should represent not more than 0. Additional ductwork of any size, including elbows, may be used to connect between the chamber and the exit of the 10D minimum asnrae duct.
For large changes in air density or rotational speed, it is necessary to treat the air as a compressible gas. In addition, ashrad making fan law conversions, air density has a first power effect on fan pressure while fan speed produces a second power effect.
Since the velocity determination depends on Reynolds Number, an approximation must be employed. Any combination of screens or perforated sheets may be used. Surrounding this curve is a band of uncertainties, the boundaries of which are roughly parallel to the test curve.
The fan total efficiency multiplied by the ratio of fan static pressure to fan total pressure. Also shown is a parabola with the vertex at the origin that intersects the fan curve and both of the boundaries. When a reaction dynamometer is used to measure torque, the fan power input H shall be calculated from the beam load Fusing the moment arm l and the fan rotational speed N using: The point of operation where the fan static pressure is zero.
Plans shall be made to vary the opening of the throttling device in such a way that the test determinations will be well-spaced.
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Learn more about Amazon Prime. If there is a need to reduce the uncertainty at either low flow or low pressure, then the instruments chosen to measure the corresponding quantity must be selected with suitable accuracy lower uncertainties for those conditions.
Substituting ashraae rearranging gives: Such a device shall be located on the end of the test duct or test chamber and should be symmetrical about the duct or chamber axis. An outlet duct used to provide a measurement station shall not have an area more than 5. Transition Piece Notes 1.
Manifold tubing internal area shall be at least 4 times that of a wall tap.