Low-speed axial fans are used extensively for ventilation purposes in industrial and commercial buildings. In agricultural applications, such as a greenhouse, the ventilation is critical, since entire crops can be damaged or destroyed if a clean air supply is not maintained. The cost-marginal nature of these businesses demand that operating costs be kept to a minimum, hence there is a strong motivation to develop higher efficiency ventilation fans. An analysis of a low-speed axial fan has been developed using a control volume-based energy balance. The specific fan is an axial ventilation fan that is commonly found on agricultural facilities such as green-houses or livestock buildings. These fans induce an airflow from a large building into the open atmosphere at very low (or often effectively zero) system restriction or pressure rise. The definition for static efficiency, which is commonly used by the axial fan community, is examined and its implications are discussed. Since static efficiency yields a zero-percent efficient fan at a zero pressure rise operating condition, the ventilation fan industry has developed an alternate definition of efficiency. This alternate definition of efficiency, along with other proposed definitions, are described and their limitations are discussed. A new definition of efficiency is introduced and its basis in the integral energy equation is identified. The primary loss mechanisms of low-speed axial turbomachinery are discussed and scaling arguments are developed and used in the integral energy equation analysis. The results of this analysis yield an expanded expression of efficiency in which the loss mechanism terms can be empirically determined. When analyzed with values for a particular fan system, these results can further be used as the basis for an optimization study of that fan system.

Volume Subject Area:
Process Industries
Topics:
Fans, Ventilation, Pressure, Structures, Air flow, Energy budget (Physics), Optimization, Turbomachinery
1.
Hanan, J.J. (1998), Greenhouses, Advanced Technology Protected Horticulture, CRC Press, Boca Raton, FL.
2.
Wheeler, E. F. and Both, A. J. (2002), “Evaluating Greenhouse Mechanical Ventilation System Performance,” Agricultural and Biological Engineering Fact Sheet I-42, The Pennsylvania State University, University Park PA.
3.
Mangold
D. W.
,
Hazen
T. E.
and
Hays
V. W.
 (
1967
), “
Effect of air temperature on performance of growing-finishing swine
,”
Trans. ASAE
10
(
3)
:
370
–
375
.
4.
Fuquay
J. W.
 (
1981
), “
Heat stress as it affects animal production
,”
J. Animal Sci.
52
(
10
:
164
–
174
).
5.
Nienaber
J. A.
,
Shanklin
M. D.
,
Hahn
G. L.
and
Manak
R. C.
 (
1985
), “
Performance of neonatal and newly-weaned pigs as affected by temperature and diet
,”
Trans. ASAE
28
(
5)
:
1626
–
1634
.
6.
Nienaber
J. A.
,
Hahn
G. L.
and
Yen
J. T.
 (
1987
), “
Thermal environmental effect on growing-finishing swine: Part I - Growth, feed intake and heat production
,”
Trans. ASAE
30
(
6)
:
1772
–
1775
.
7.
Overhults, D.G. and Gates, R.S. (1993), “Energy Use in Tunnel Ventilated Broiler Houses,” Livestock Environment IV, Fourth Intl Symposium, Coventry, England, July 6-9, pp. 339–346.
8.
Potter, M.C. and Foss, J.F. (1982), Fluid Mechanics, Great Lakes Press, Okemos.
9.
Lakshminarayana, B. (1996), Fluid Dynamics and Heat Transfer of Turbomachinery, Wiley and Sons, Inc., New York.
10.
Wilson, D. G. and Korakianitis, T. (1998), The Design of High-Efficiency Turbomachinery and Gas Turbines, 2nd Edition, Prentice Hall.
11.
Dixon, S. L. (1998), Fluid Mechanics, Thermodynamics of Turbomachinery, 4th Edition, Butterworth-Heinemann.
12.
Wallis, R. A., Axial Flow Fans and Ducts, Wiley and Sons, Inc., New York, 1983.
13.
Ford, S.E., Christianson, L. L., Riskowski, G. L., Funk, T.L. (1999), Agricultural Ventilation Fans, Performances and Efficiencies, UILU ENG 99-7001.
14.
AMCA Directory of Agricultural Products with Certified Ratings (2000), Air Movement and Control Association, Inc. Publication 262-00.
15.
Bleier, F. P. (1998), Fan Handbook: Selection, Application and Design, McGraw-Hill, New York.
16.
Osborne, W. C. (1966), Fans, Pergamon Press, Oxford.
17.
McDonald
A. T.
, and
Fox
R. W.
, “
An Experimental Investigation of Incompressible Flow in Conical Diffusers
”,
International Journal of Mechanical Sciences
,
8
,
2, February 1966
, pp.
125
–
139
.
18.
Neal, D. R. (2002), M.S. Thesis, Department of Mechanical Engineering, Michigan State University.
This content is only available via PDF.
Copyright © 2006
 by ASME
You do not currently have access to this content.