Component 507: Fan or Pump by HVACSIM+
General Description
The pump or fan model calculates a pressure rise and an efficiency as
functions of a mass flow rate, using dimensionless performance curves. The
performance curves are represented by polynomials, with empirically determined
coefficients which must be supplied by the user. The efficiency is used to
compute a temperature rise across the fan or pump, as well as power
consumption. The last parameter, MODE, determines whether air or water
properties (density and specific heat) are to be used.
Nomenclature
Cf - dimensionless flow coefficient
Ch - dimensionless pressure head coefficient
Cp - specific heat of fluid (kJ/kg-C)
D - diameter of blades or impeller (m)
E - power consumption (kW)
N - rotational speed (rps)
Pi - inlet pressure (kPa)
Po - outlet pressure (kPa)
Ti - inlet temperature (C)
To - outlet temperature
w - mass flow rate (kg/s)
n - efficiency
p - fluid density (kg/m^3)
Mathematical Description
The dimensionless flow coefficient and the dimensionless pressure head
coefficient are defined as follows:
Cf=w/(pN(D^3))
Ch=1000*DeltaP/(p(N^2)(D^2))
where DeltaP is the pressure rise, Po - Pi, in kilopascals. The factor of 1000
converts the pressure difference from pascals to kilopascals for dimensional
consistency. For this reason, the units given in the nomenclature section must
be used.
The model determines the head coefficient, Ch, and the efficiency, n,
as functions of the flow coefficient, Cf:
Ch=a0 + a1Cf + a2(Cf^2) + a3(Cf^3) + a4(Cf^4)
n=e0 + e1Cf + e2(Cf^2) + e3(Cf^3) + e4(Cf^4)
The 'a' and 'e' coefficients must be supplied as parameters by the users. The
inlet pressure is then obtained from the definition of Ch:
Pi=Po - 0.001(Ch)p(N^2)(D^2)
The efficiency is used to compute power consumption, and a temperature rise is
calculated on the assumption that all inefficiencies heat the fluid:
E=w(DeltaP)/(np)
To=Ti + (Po-Pi)/(p(Cp))*(1/n-1)
Component 507 Configuration
Inputs Description
1 w - fluid mass flow rate (kg/s)
2 Po - outlet pressure (kPa)
3 N - rotational speed (rps)
4 Ti - inlet temperature (C)
Outputs Description
1 Pi - inlet pressure (kPa)
2 To - outlet temperature (C)
3 E - power consumption (kW)
Parameters Description
1-5 ai - coefficients for head vs. flow curve
6-10 ei - coefficients for efficiency curve
11 D - diameter (m)
12 Mode - air=1, water=2
Reference:
1. HVACSIM+ Building Systems and Equipment Simulation Program Reference
Manual (NBSIR 84-2996)
Daniel R. Clark
United States Department of Commerce
National Institute of Standards and Technology
Gaithersburg, Maryland 20899-0001