Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our User Agreement and Privacy Policy.

Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our Privacy Policy and User Agreement for details.

Like this presentation? Why not share!

3,711 views

Published on

Fans and Blowers Principles

No Downloads

Total views

3,711

On SlideShare

0

From Embeds

0

Number of Embeds

8

Shares

0

Downloads

415

Comments

0

Likes

8

No embeds

No notes for slide

- 1. Fan is a machine used to add energy to the gaseous fluid to increase its pressure. Fans are used where low pressures (from a few mm of water to 50 mm Hg) and comparatively large volume are required. They run at relatively low speed, the casing and impeller usually built of sheet iron. FAN TYPES 1) AXIAL FLOW FANS - the flow of the gases is parallel to the fan shaft. a. tube axial b. vane axial c. Propeller 2) RADIAL OR CENTRIFUGAL FLOW FANS- the flow of gases depends upon the centrifugal action of the impeller or rotor. a. Straight blades b. Forward curved blades c. Backward curved blades d. Double curved blades
- 2. Propeller Fan Tubeaxial Fan Centrifugal Fan Air in Housing Rotor Motor Air out Vaneaxial Fan
- 3. COMMON USES OF FANS 1. Ventilation and air conditioning 2. Forced and induced draft service for boilers 3. Dust collection 4. Drying and cooling of materials 5. Cooling towers 6. Mine and tunnel ventilation 7. Pneumatic conveying and other industrial process work Head Calculations 2 1 discharge suction For a fan Z = 0 ; PE = 0 and Q = 0, because fans are designed to overcome fluid friction. No cooling system is needed due to small temperature differential between suction and discharge.
- 4. From Bernoulli’s energy theorem 1. For fans installed with both suction and discharge duct 2 P2 P1 v 2 v 1 ht γ 2g 2 m of gas 2. For fans installed with only a suction duct; P2 = 0 gage 2 0 P1 v 2 v 1 ht γ 2g 2 m of gas 3. For fans installed with only discharge duct; P1 = 0 gage and v1 = 0 2 P2 v 2 ht γ 2g m of gas
- 5. let P2 P1 hs m of gas γ 2 v 2 v1 hv 2g 2 m of gas ht = hs + hv m of gas Where: hs - static head at which a fan operates, m of gas hv - velocity head at which a fan operates, m of gas ht - total head added to the fluid, m of gas
- 6. Head Conversion: From m of gas to m of water hw γ gh g γw ρ gh g ρw m of water htw = hsw + hvw Where: h - stands for ,total head, static head or velocity head w - refers to water; g - refers to gas
- 7. FAN POWER FP = Qwhtw KW STATIC POWER SP = Qwhsw KW where Q - capacity in m3/sec w - specific weight of water (gage fluid) in KN/m3 htw - total head in m of WG hsw - static head in m of WG FP - total fan power in KW SP - Static power in KW Static Power - is that part of the total air power, that is used to produced the change in static head.
- 8. FAN EFFICIENCY FP η x 100 % F BP STATIC EFICIENCY SP η x 100% S BP BP - Brake or shaft power in KW
- 9. FAN LAWS A. Variation in speed and impeller diameter Q ND3 H N2D2 B. Variation in impeller Speed Q N ; H N2 ; Power N3 C. Variation in impeller size; Tip speed = C ; = C and same proportions; H = C Q D2 ; Power N2 ; N 1/D D. Variation in impeller size; N = C; = C ; Same proportions Q D3 ; Power D5 ; H D2 ; Tip Speed D E. Variation in density; Q = C; N =C; D = C; system = C H ; Power F. Variation in Density; D = C; H = C 1 Q ; Power ρ 1 1 ; N ρ ρ
- 10. G. Variation in density; m = C;D = C; system = C 1 Q ; H ρ 1 1 1 ; N ; Power 2 ρ ρ
- 11. A certain fan delivers 340 m3/min of air at a static pressure of 25.4 mm WG when operating at a speed of 400 RPM and requires an input of 3 KW. If in the same installation 425 m3/min of air are desired, what will be the new Q, hsw and Fan power required? (40 mm WG;500 RPM;6 KW )
- 12. Q1 340m 3 / min hs1 0.025m of H 2 O N1 400 RPM BP1 3 KW Q 2 425 m 3 /min N2 BP2 From Fan Laws Q N; h N 2; P N 3 Q2 N 2 Q1 N1 425 N 2 340 400 N 2 500 RPM 2 h s2 500 25 400 hs 2 39.1 mm WG BP2 500 3 400 BP2 6 KW 3
- 13. BLOWERS Blower is a machine used to compressed air or gas by centrifugal force to a final pressure not exceeding 241 KPa gage. Usually blower has no cooling system or it is not water cooled. COMPRESSION OF GASES The design of blower is usually based upon either an adiabatic or isothermal compression. A. For Adiabatic or Isentropic Compression: P P2 P1 2 PVk = C 1 V
- 14. k 1 T2 P2 k T1 P1 P k 1k kP1Q 2 W 1 P k 1 1 W QγH where Q V1 Q - capacity in m3 /sec H - adiabatic head in meters P k 1k 1000kRT1 2 H 1 m of gas gk 1 P1
- 15. B. For Isothermal Compression: P P2 2 PV = C 1 P1 V P1V1 P2 V2 C P2 P2 W P1Q ln mRT1ln KW P1 P1 W QγH KW H 1000RT1 P2 ln g P1 meters where H - isothermal head in meters Q - capacity in m3/sec g - gravitational acceleration in msec2
- 16. Efficiency: A. Adiabatic or Isentropic Efficiency Isentropic Work ηk x 100% Actual Work B. Isothermal Efficiency Isothermal Work ηI x 100% Actual Work RATIO OF THE ADIABATIC TEMPERATURE RISE TO THE ACTUAL TEMPERATURE RISE P k 1k T1 2 1 P 1 Y ' T2 T1
- 17. RELATIONSHIP FOR CORRECTING PERFORMANCE CURVES 1. Volume Flow Q B NB Q A NA 2. Weight Flow mB NB P1B m A N A P1A T1A T 1B 3. Pressure Ratio P k 1k 2 1 P 2 1 B NB T1A N T k 1 P k A 1B 2 1 P 1 A P2 rp (pressure ratio) P1
- 18. 4. Head 2 HB N B 2 HA NA 5. Brake Power BPB NB BPA N A 3 P1B P 1A T1A T 1B P k 1k 2 1 P BPB P1B Q B 1 B BPA P1A Q A k 1k P 2 1 P 1 A Where: 1 - suction 2 - discharge A - 1st condition B - 2nd condition R - gas constant, KJ/kg-K P - absolute pressure in KPa - density, kg/m3 T - absolute temperature, K H - head, m - specific weight, KN/m3 Q - capacity, m3/sec BP - brake power, KW N - speed, RPM W - work, KW m - mass flow rate, kg/sec
- 19. Copyright: YURI G. MELLIZA 324619CYE

No public clipboards found for this slide

×
### Save the most important slides with Clipping

Clipping is a handy way to collect and organize the most important slides from a presentation. You can keep your great finds in clipboards organized around topics.

Be the first to comment