7.5-i

APPENDIX 7.5. BLOWER FAN CURVES

TABLE OF CONTENTS

7.5.1 INTRODUCTION ................................................... 7.5-1

7.5.2 STATIC PRESSURE ................................................. 7.5-4

7.5.3 SHAFT POWER ..................................................... 7.5-4

LIST OF TABLES

Table 7.5.1.1 Models Used For Virtual Furnace Blowers ........................... 7.5-1

Table 7.5.2.1 Coefficients to Calculate Pressure for Different Blower Sizes ............... 7.5-4

Table 7.5.3.1 Coefficients to Calculate Shaft Power for Different Blower Sizes ............ 7.5-5

LIST OF FIGURES

Figure 7.5.1.1 Blower Fan Curves for Lau #DD9-8A ............................... 7.5-2

Figure 7.5.1.2 Blower Fan Curves for Lau #DD10-8A .............................. 7.5-2

Figure 7.5.1.3 Blower Fan Curves for Lau #DD10-10A ............................. 7.5-3

Figure 7.5.1.4 Blower Fan Curves for Lau #DD11-10AT ............................ 7.5-3
7.5-1

APPENDIX 7.5. BLOWER FAN CURVES

7.5.1 INTRODUCTION

Blower manufacturers provide blower fan curves for both pressure and shaft power as

functions of airflow. The Department chose four blowers from Lau Industries, a manufacturer that

supplies blowers to the furnace industry, to match the four virtual model furnace blowers.

The models DOE used for the different virtual furnace blowers are listed in Table 7.5.1.1. 

Table 7.5.1.1 Models Used For Virtual Furnace Blowers 

Airflow Capacity Blower Size Lau Industries Model

800 cfm (2 ton) 9 X 8 DD9-8A

1200 cfm (3 ton) 10 X 8 DD10-8A

1600 cfm (4 ton) 10 X 10 DD10-10A

2000 cfm (5 ton) 11 X 10 DD11-10AT

Pressure and shaft power curves for these blowers are available in fan selection software from

Lau Industries.1 Figures 7.5.1.1 - 7.5.1.4 show the curves for these blowers. The Department fit

polynomial equations of air flow to the static pressure and shaft power curves of these blowers. 

Knowing these equations permits the Department to calculate static pressure and shaft power at any

airflow rate.
7.5-2

0

0.5

1

1.5

0 1000 2000 3000 4000 5000

Q, Airflow (CFM)

P, Static Pressure (in. w.g)

0

1

2

3

H, Shaft Power (hp)

P

H

Figure 7.5.1.1 Blower Fan Curves for Lau #DD9-8A

0

0.5

1

1.5

0 1000 2000 3000 4000 5000

Q, Airflow (CFM)

P, Static Pressure (in. w.g)

0

1

2

3

H, Shaft Power (hp)

P

H

Figure 7.5.1.2 Blower Fan Curves for Lau #DD10-8A
7.5-3

0

0.5

1

1.5

0 1000 2000 3000 4000 5000

Q, Airflow (CFM)

P, Static Pressure (in. w.g)

0

1

2

3

H, Shaft Power (hp)

P

H

Figure 7.5.1.3 Blower Fan Curves for Lau #DD10-10A

0

0.5

1

1.5

0 1000 2000 3000 4000 5000

Q, Airflow (CFM)

P, Static Pressure (in. w.g)

0

1

2

3

H, Shaft Power (hp)

P

H

Figure 7.5.1.4 Blower Fan Curves for Lau #DD11-10AT
7.5-4

7.5.2 STATIC PRESSURE

The coefficients for the polynomial equation for static pressure rise across the blower as a

function of airflow are shown in Table 7.5.2.1. The speeds at which they were tested are included in

the table as well. The coefficients vary depending on blower size. The equation used to fit static

pressure is:

P(Q) = c0 + c1 × ( Q/1000) + c2 × (Q/1000)^2 + c3 × (Q/1000)^3 + c4 × (Q/1000)^4

where: 

Q = airflow (cfm),

P = static pressure (in.w.g.), and

c0-c4 = coefficients.

Table 7.5.2.1 Coefficients to Calculate Pressure for Different Blower Sizes

Blower Size Speed c0 c1 c2 c3 c4

11 × 10* 1055 2.816408 -14.45755 50.06729 -79.1925 57.93131

10 × 10 1020 0.571842 0.952433 -0.40526 0.027687 0

10 × 8 1044 0.05092 2.51260 -1.96989 0.64310 -0.08909

9 × 8 1084 1.25829 -1.09850 1.17555 -0.56167 0.06693

*

 For this blower size, the coefficient Q was divided by 4000, not 1000 as shown in the equation.

7.5.3 SHAFT POWER

Shaft power is the mechanical power input to the blower. It is the power required to rotate the

blower wheel at the tested speed under the tested static pressure and airflow conditions.

The Department determined shaft power using a second-order polynomial equation. The

coefficients vary depending on blower size. Table 7.5.3.1 shows the different blower sizes and their

corresponding coefficients that DOE used to determine shaft power.

H(Q) = h0 + h1 × ( Q/1000) + h2 × (Q/1000)2

where: 

Q = airflow (cfm), 

H = shaft power (hp), and

h0, h1, h2 = coefficients.
7.5-5

Table 7.5.3.1 Coefficients to Calculate Shaft Power for Different Blower Sizes

Blower size Speed h0 h1 h2

11 × 10 1055 0.02424 0.209691 0.073447

10 × 10 1020 0.052032 0.195255 0.072613

10 × 8 1044 0.012244 0.187546 0.086849

9 × 8 1084 0.044483 0.100756 0.108843
7.5-6

REFERENCES

1. Lau Industries, Whirl Wind IV, Version 4.0, Fan Application Software. 2000.

http://www.lau-ind.com/whirlwind.htm