Horsepower correction factors report
Question and answers
1. Assuming that the dry bulb temperature is 86 while the wet bulb reading is 77, find the following:
What is the wet bulb depression?
Wet bulb depression = 86°-77°=9°

9 F
What is the dew point temperature?
75.5 F

3. What is the saturation vapor pressure associated with the dry bulb reading? =22.3 mbars
4. What is the saturation vapor pressure associated with the dew point temperature? =16.0 m bars
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2—Relationship between temperature and moisture content of saturated air. The maximum moisture that the air can hold depends on how warm it is; as the temperature rises, so does the saturation point.

5. What is the relative humidity is 60%
6. What is the saturation potential is 8 gr/ft3
7. What is the absolute humidity is given by
absolute humidity = RH*Saturation potential
absolute humidity=8*0.6=4.8 gr/ft^3
Assuming that the dry bulb temperature is 86 while the wet bulb reading is 64.4, find the following:
8. What is the wet bulb depression?
Wet bulb depression = 86°-64.4°=21.6°
=21.6 F
9. From the psychometric chart the dew point temperature is
=56 F
10. What is the saturation vapor pressure associated with the dry bulb reading? =22.3 mbars
11. What is the saturation vapor pressure associated with the dew point temperature? =13.7 mbars
12. What is the relative humidity is 35%
13. What is the saturation potential is 5 gr/ft3
14. What is the absolute humidity is given by
absolute humidity = RH*Saturation potential
absolute humidity=5*0.35=1.75 gr/ft^3
Assuming that the dry bulb temperature is 50 while the wet bulb reading is 48.2, find the following:
15. What is the wet bulb depression?
Wet bulb depression = 50°-48.2°=1.8°
1.8 F

16. From the psychometric chart the dew point temperature is
47F
17. What is the saturation vapor pressure associated with the dry bulb reading? 12.95 mbars
18. What is the saturation vapor pressure associated with the dew point temperature? 10 mbars
19. The relative humidity is 80%
20. What is the saturation potential is 8 gr/ft^3

21. The absolute humidity is given by
absolute humidity = RH*Saturation potential
absolute humidity=8*0.8=6.4 gr/ft^3

Assuming that the dry bulb temperature is 50 while the wet bulb reading is 35.6, find the following:
22. What is the wet bulb depression?
Wet bulb depression = 50°-35.6°=14.4°
= 14.4 F
23. From the psychometric chart the dew point temperature is 31.2F
24. What is the saturation vapor pressure associated with the dry bulb reading? =13 mbars
25. What is the saturation vapor pressure associated with the Dew point temperature? =6.62 mbars
26. The relative humidity is 5%
27. What is the saturation potential is 8 gr/ft3

28. The absolute humidity is given by
8×0.05=0.4 gr/ft^3
=0.4 gr/ft^3
29. Given that the relative humidity in question number 12 is much lower than the relative humidity in question number 19, explain why the absolute humidity in question 14 is higher than the absolute humidity in question 21.
the absolute humidity in question 14 is higher than the absolute humidity in question 21 because
30. What natural phenomenon accounts for the wet bulb depression? Explain why the wet bulb depression is greater when relative humidity is low.

Horsepower Correction Factors
Using the correction factor charts determine the separate correction factors for pressure (fP), temperature (fT), and humidity (fH) and the associated composite correction factor (FC) based upon the specific atmospheric conditions cited.
Atmospheric (fP) X (fT) X (fH) = (FC)
31. Conditions
26.00 in Hg
105 F dry bulb 1.792 X 1.0947 X 1.671 = ___3.278______
90 F wet bulb
26.45 in Hg
32. 84 F dry bulb 1.860 X 1.1087 X 1.9 = ___3.918______
76 F wet bulb
27.70 in Hg
33. 80 F dry bulb 1.928 X 1.1017 X 1.301 = ___2.763______
68 F wet bulb

28.20 in Hg
34. 70 F dry bulb 1.928 X 1.0947 X 1.028 = _2.170________
55 F wet bulb

28.70 in Hg
35. 60 F dry bulb 1.928 X 1.0947 X 1.028 = ___2.170______
45 F wet bulb

29.30 in Hg
36. 50 F dry bulb 1.928 X 1.1017 X 1.387 = __2.946_______
38 F wet bulb

29.93 in Hg
37. 40 F dry bulb 1.996_ X 1.1111 X 1.995 = 4.442
32 F wet bulb

30.60 in Hg
38. 34 F dry bulb 1.996 X 1.1255 X 2.086 = 4.686
32 F wet bulb
Using the techniques learned earlier, and referring to Figures 1 & 2, answer the following questions. Be certain to show all work in order to receive full credit for your answers.
39. the relative humidity associated with question 32 above is = 75%

40. the absolute humidity associated with question 32 above?

6×.75=4.5 gr/ft^3
=4.5 gr/ft^3
41. the relative humidity associated with question 38 above is 5%
42. What is the absolute humidity associated with question 38 above?
5×.05=0.025 gr/ft^3
=0.025 gr/ft^3
43. Given that the relative humidity in questions 39 and 41 is virtually the same, explain why the absolute humidity in question 42 is so much less than that of question 40.
The absolute humidity in question 42 is so much less than that of question 40.

Final exercise
The purpose of horse power correction factors is to correct site and time specific engine performance to standard atmospheric conditions. In a dynamometer test undertaken for a one cylinder Briggs and Stratton engine, the dynamometer had a torque arm of 6.3 inches in length. The table below shows the calculated uncorrected and corrected torque as well as the uncorrected and corrected horsepower.
Atmospheric Conditions of the Test:

Barometric Pressure 28.2 in Hg
Dry Bulb Temperature 100 F
Wet Bulb Temperature 85 F

fP) X (fT) X (fH) = (FC)

1.928 X 1.0947 X 1.682 = 3.559

Rpm Force(W_lbs) Uncorrected torque (tlb-ft)
Lft X Wlbs Corrected Torque (tC lb-ft) tlb-ft X FC BHP Uncorrected Horse power
tlb-ft X rpm/5252 BHPc
Corrected Horsepower
BHP X FC
2000 6.5 3.4125 12.145 1.30 4.63
2500 7.6 3.99 14.200 1.90 6.76
3000 8.0 4.2 14.948 2.40 8.5416
3500 7.7 4.0425 14.387 2.70 9.6093
4000 7.3 3.8325 13.640 2.92 10.3923
4500 6.9 3.6225 12.892 3.10 11.1041

L_ft = 0.525 ft
Uncorrected torque calculations.
Uncorrected torque for 2000 Rpm
〖torque (t〗_(lb-ft)) =W_lbs ×L_ft
t_(lb-ft)=6.5 lbs*0.525 ft=3.4125 lb-ft
Uncorrected torque for 2500 Rpm
〖torque (t〗_(lb-ft)) =W_lbs ×L_ft
t_(lb-ft)=7.6 lbs*0.525 ft=3.99 lb-ft
Uncorrected torque for 3000 Rpm
〖torque (t〗_(lb-ft)) =W_lbs ×L_ft
t_(lb-ft)=8.0 lbs*0.525 ft=4.2 lb-ft
Uncorrected torque for 3500 Rpm
〖torque (t〗_(lb-ft)) =W_lbs ×L_ft
t_(lb-ft)=7.7 lbs*0.525 ft=4.0425 lb-ft
Uncorrected torque for 4000 Rpm
〖torque (t〗_(lb-ft)) =W_lbs ×L_ft
t_(lb-ft)=7.3 lbs*0.525 ft=3.8325 lb-ft
Uncorrected torque for 4500 Rpm
〖torque (t〗_(lb-ft)) =W_lbs ×L_ft
t_(lb-ft)=6.9 lbs*0.525 ft=3.6225lb-ft
Corrected torque calculations where Fc = 3.559
Corrected torque for 2000 Rpm
tC lb-ft)= tlb-ft X FC
tC lb-ft)= 3.4125 lb-ft*3.559= 12.145 lb-ft
Corrected torque for 2500 Rpm
tC lb-ft)= tlb-ft X FC
tC lb-ft)= 3.99 lb-ft*3.559= 14.200lb-ft
Corrected torque for 3000 Rpm
tC lb-ft)= tlb-ft X FC
tC lb-ft)= 4.2 lb-ft*3.559= 14.948lb-ft
Corrected torque for 3500 Rpm
tC lb-ft)= tlb-ft X FC
tC lb-ft)= 4.0425 lb-ft*3.559= 14.387lb-ft
Corrected torque for 4000 Rpm
tC lb-ft)= tlb-ft X FC
tC lb-ft)= 3.8325 lb-ft*3.559= 13.640 lb-ft
Corrected torque for 4500 Rpm
tC lb-ft)= tlb-ft X FC
tC lb-ft)= 3.6225 lb-ft*3.559= 12.892lb-ft
BHP uncorrected calculations
BHP=(T*RPM)/5252
BHP=(3.412*2000)/5252 = 1.30 HP
BHP=(3.99*2500)/5252= 1.90 HP
BHP=(4.2*3000)/5252= 2.40 HP
BHP=(4.0425*3500)/5252 = 2.70 HP
BHP=(3.8325*4000)/5252=2.92 HP
BHP=(3.6225*4500)/5252= 3.10 HP
Corrected BHP calculations
Corrected BHP=BHP*CF
Corrected BHP=1.30 hp* 3.559= 4.63 HP
Corrected BHP=1.90 hp* 3.559= 6.76 HP
Corrected BHP=2.40 hp* 3.559= 8.5416 HP
Corrected BHP=2.70 hp* 3.559= 9.6093 HP
Corrected BHP=2.92 hp* 3.559= 10.3923 HP
Corrected BHP=3.10 hp* 3.559= 11.1041 HP