Fan (speed control)

File: fan speed.doc

Last edition: 2003-03-20/MK

Author: Lars Halling

History: 96-03-01/HN First released version

96-10-04/MK Updated to Menta 1.20

97-09-01/MK Updated to Menta 3.0

98-12-16/MK New file namne.

2003-03-20/MK Updated to Menta 4.0

Description

Model of fan with speed control. The dynamics from the control signal to the fan speed (rpm) is modelled as a first order system. The rest of the model is static. The model is based on the assumption that one point on the fan curve is known. This point is defined by the air flow (q0), pressure (p0) and fan speed (N0). Other operating conditions is derived from the known operating point and fan laws, cf. 1992 ASHRAE HANDBOOK, pg. 18.4.

The fan speed is assumed to be a linear function of the control signal:

uc=0% => N=0 and p=0

uc=100 % => N=N0 and p=p0

REFERENCES

ASHRAE. (1992):"1992 ASHRAE HANDBOOK, FUNDAMENTALS," SI-edition. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc, Atlanta.

Inputs

(Real) Control Signal, %.

Outputs

(Real) Pressure after Fan, Pa.

(Real) Air Flow, m³/s.

Constants

(Real) p0 = fan pressure in known operating point (Pa). Nominal value = 500 Pa.

(Real) q0 = air flow in known operating point (m³/s). Nominal value = 5.0 m³/s.

(Real) N0 = fan speed in known operating point (rpm). Nominal value = 1400 rpm.

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