Industrial Ventilation Design Procedure Industrial Ventilation Design Procedure

Industrial Ventilation Design Procedure

Industrial Ventilation Design Procedure 1. 2. 3. 4. 5. 6. 7. 8. Find Q Determine d Calculate actual V Calculate VP Find VP loss coefficients Calculate Fan SP Calculate Fan TP Choose Fan rpm from Fan Table Design Procedure 2

Losses v Inches of water v Percent of velocity pressure v Friction losses v Elbow losses v Other losses v v v Hood entry losses Orifice losses Expansion and Contraction losses Air cleaner losses Stack losses Design Procedure 3

Review Of Design Tables v Refer to FIGURE 5 -15 to find hood entry loss coefficients. v Refer to FIGURE 5 -16 to find elbow losses. v Refer to TABLE 5 -5 and TABLE 5 -6 to find friction loss for the given diameter and velocity. v Refer to TABLE 5 -7 A and TABLE 5 -7 B to find velocity for a given VP. v Refer to TABLE 5 -8 to find area for a given diameter. v Refer to TABLE 5 -10 to find Air Density Correction Factor for a given temperature and barometric pressure. v Review rest of the tables given in chapter 5. Design Procedure 4

Review Of Design Tables v For solving various problems given in chapter # 5 the corresponding figures are given in chapter # 10. v For solving design problem 4, tables 10. 70. 1 to 10. 70. 4 will be useful. v Before solving the design problems go through the figure and data given in chapter 10. Design Procedure 5

Review Of Design Tables v Refer to TABLE 3 -1 to find the various ranges of capture velocities. v Refer to TABLE 3 -2 to find the range of minimum duct velocities for various contaminants. v Go through all the figures in chapter # 3 representing various hoods. Design Procedure 6

Design Procedure v GIVEN DATA: v Ventilation system: v v Laboratory Hood Volumetric Flow Rate, Q = 1500 CFM Minimum Transport Velocity, V = 4000 FPM Stamped elbow with R / D = 2 Design Procedure 7

Design Procedure v Download DESIGN PROBLEM-1 v Line 1: Inlet Section v Line 2: Target Volume Flow Rate, Q = 1500 CFM (Given). v Line 3: Minimum Transport Velocity, V = 4000 FPM (Given). v Line 4: Maximum Duct Diameter, D = 8. 29” We know Q = V * A Hence Duct Area = Q / A = 1500 / 4000 = 0. 375 Sq. Ft. We know A = (Pi * D 2) / 4 Hence, D = 8. 29” Design Procedure 8

Design Procedure v Line 5: Selected duct diameter = 8” We got Maximum Duct Diameter D = 8. 29” We have to choose a diameter that is less than maximum selected diameter so that minimum transport velocity is not maintained in the duct. So, let’s choose 8” diameter. Note: Your choice is limited by the sizes given in the table. v Line 6: Duct Area = 0. 349 Sq. ft. Duct Area (from TABLE 5 -8 at D = 8”) = 0. 349 Sq. ft. v Line 7: Actual Duct Velocity = 4298 FPM Velocity = Q / Area = 1500 / 0. 349 = 4928 fpm Design Procedure 9

Design Procedure v Line 8: Duct Velocity Pressure = 1. 15” WG Duct VP (from TABLE 5 -7 A at V = 4298 FPM) = 1. 15” WG v Line 9 -16 = N/A (since there are no slots) v Line 17: Duct Entry Loss Coefficient = 0. 49 Given, hood has a flanged duct end From TABLE 5 -15 for a hood that has a flanged duct end, entry loss coefficient is 0. 49 Design Procedure 10

Design Procedure v Line 18: Acceleration Factor ( 1 or 0) = 1 Since acceleration factor is 1 for hoods. v Line 19: Duct Entry Loss per VP (17 + 18) = 1. 49” WG v Line 20: Duct Entry Loss (8 * 19) = 1. 714 v Line 21: Other Losses = 0 v Line 22: Hood Static Pressure, SPh (16+20+21) = 1. 714” WG v Line 23: Straight Duct Length = 35 ft (Given) v Line 24: Friction Factor (Hf) = 0. 0304 From TABLE 5 -5 at D = 8” and V = 4000 FPM Hf = 0. 0304 v Line 25: Friction Loss per VP (23 * 24) = 1. 064 v Line 26: No. of 900 degree Elbows = 1 Design Procedure 11

Design Procedure v Line 27: Elbow Loss Coefficient = 0. 13 From TABLE 5 -16 for a stamped elbow and R/D = 2 v Line 28: Elbow Loss Factor (26 * Loss Factor(27)) = 0. 13 v Line 28 -32 = N/A Since there are no branch entries v Line 33: Duct Loss per VP (25 + 28 + 31+ 32) = 1. 1940 v Line 34: Duct Loss (8 * 33) = 1. 3731 v Line 35: Duct Segment SP Loss (22 + 34) = 3. 087” WG v Line 36: Other Losses = N / A v Line 37: Cumulative Static Pressure = 3. 087” WG v Line 38: Governing Static Pressure = -3. 087” WG Design Procedure 12

Design Procedure v Line 39 -42 = N / A v Line 1: Outlet Section v Line 2 -8 same as for inlet section v Line 9 -22 = N / A as outlet is exhaust that is it will not have suction part v Line 23: Straight Duct Length = 10 ft (Given) v Line 24: Friction Factor (Hf) = 0. 0304 From TABLE 5 -5 at D = 8” and V = 4000 FPM Hf = 0. 0304 v Line 25: Friction Loss per VP (23 * 24) = 0. 3019 v Line 26: No. of 900 degree Elbows = 1 Design Procedure 13

Design Procedure v Line 27: Elbow Loss Coefficient = 0. 13 v v v v From TABLE 5 -16 for a stamped elbow and R/D = 2 Line 28: Elbow Loss Factor (26 * Loss Factor(27)) = 0. 13 Line 28 -32 = N/A Since there are no branch entries Line 33: Duct Loss per VP (25 + 28 + 31+ 32) = 0. 4319 Line 34: Duct Loss (8 * 33) = 0. 4990 Line 35: Duct Segment SP Loss (22 + 34) = 0. 499” WG Line 36: Other Losses = N / A Line 37: Cumulative Static Pressure = 0. 499” WG Line 38: Governing Static Pressure = -0. 499” WG Design Procedure 14

Design Procedure Final Calculations: v The Fan SP = Spo – SPin - VPin = 0. 499 – (-3. 087) – 1. 15 = 2. 436 FPM v The Fan TP = VPo + SPo – SPin - VPin = 1. 15 + 0. 499 – (-3. 087) – 1. 15 = 3. 586 FPM v BHP = (Fan TP * Q) / 6362 * η = (3. 586 * 1500) / (6362 * 0. 9) = 0. 94 hp Where: η = Mechanical Efficiency (here taken as 0. 9) You have completed the design of laboratory hood. Design Procedure 15

Design Problems v Download DESIGN PROBLEM – 2, 3, 4 and start doing the problems v All are of the same procedure with minor changes. v For fan pressure calculations refer 5. 8 in the text book. v Refer 5. 9 to know the corrections for velocity changes. v Refer 5. 13 in the text book to get an idea of corrections for non-standard density. v Go through various problems given in the text book. Design Procedure 16

CALCULATION OF Vpr v For design problems 3 and 4 you need to calculate corrected volumetric flow rate and VPr. v For calculating corrected volumetric flow rate and VPr formulae are given in the design spread sheets. v Refer to the spread sheet solution and word solution given carefully. Design Procedure 17