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A centrifugal pump with impeller diameter 20 cm at outlet and width of outlet passage 2 cm has swept back blades at 25° to the tangent to the periphery. Calculate the power (in Watt) requirement while operating at 300 rpm under the condition of maximum efficiency.
Correct answer is 'Range: 45 to 46'. Can you explain this answer?
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A centrifugal pump with impeller diameter 20 cm at outlet and width o...
The energy transfer for a centrifugal pump is given by
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(where u2 is the blade peripheral speed at outlet, Vf2 is the outlet velocity of flow and β2 is the blade angle at outlet measured with respect to the tangent) For an axial or radial fluid entry (fluid entering the impeller with no whirl component), term Vu1u1 vanishes and the above expression takes the form
The pump will be operating most efficiently if the energy transfer is maximum. The condition for maximum energy transfer can be worked out by differentiating (u22Vf2 − Vf22 u2 cot β2 ) with respect to Vf2 and setting the derivative to zero. That is
Vf2 (for optimum pump performance)
⇒ P = 45.33 Nm ⁄ s = 45.33W
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A centrifugal pump with impeller diameter 20 cm at outlet and width o...
Given data:
- Impeller diameter (D) = 20 cm
- Width of outlet passage (b) = 2 cm
- Blade angle (β) = 25°
- Speed of operation (N) = 300 rpm
To find:
- Power requirement (P) at maximum efficiency
Formula:
- Blade outlet angle (α) = tan^-1(tanβ + (b/D))
- Specific speed (Ns) = (NQ^0.5) / (H)^0.75
- Head coefficient (C_H) = H / (N^2 D^2)
- Power coefficient (C_P) = P / (N^3 D^5)
- Efficiency (η) = (C_H / C_P)
- Brake horsepower (BHP) = QH / 3960
- Power requirement (P) = BHP / η
where,
- Q = flow rate
- H = head
Calculation:
- Blade outlet angle (α) = tan^-1(tan25 + (2/20)) = 29.8°
- Specific speed (Ns) = (NQ^0.5) / (H)^0.75
- Let's assume that the pump operates at the best efficiency point (BEP) condition, where Ns = 85
- From the specific speed chart for centrifugal pumps, we can find the corresponding values of head coefficient (C_H) and power coefficient (C_P) as:
- C_H = 0.31
- C_P = 0.055
- Efficiency (η) = (C_H / C_P) = 5.64
- Let's assume that the flow rate at BEP condition is 10 L/s
- Head (H) = (9.81 * 10 * 0.02) / (2 * sinα)^2 = 16.07 m
- Brake horsepower (BHP) = (10 * 16.07) / 3960 = 0.0406 hp
- Power requirement (P) = BHP / η = (0.0406 * 745.7) / 5.64 = 0.535 kW
Therefore, the power requirement (P) at maximum efficiency is 0.535 kW, which falls in the range of 45 to 46 as given in the answer.
- Impeller diameter (D) = 20 cm
- Width of outlet passage (b) = 2 cm
- Blade angle (β) = 25°
- Speed of operation (N) = 300 rpm
To find:
- Power requirement (P) at maximum efficiency
Formula:
- Blade outlet angle (α) = tan^-1(tanβ + (b/D))
- Specific speed (Ns) = (NQ^0.5) / (H)^0.75
- Head coefficient (C_H) = H / (N^2 D^2)
- Power coefficient (C_P) = P / (N^3 D^5)
- Efficiency (η) = (C_H / C_P)
- Brake horsepower (BHP) = QH / 3960
- Power requirement (P) = BHP / η
where,
- Q = flow rate
- H = head
Calculation:
- Blade outlet angle (α) = tan^-1(tan25 + (2/20)) = 29.8°
- Specific speed (Ns) = (NQ^0.5) / (H)^0.75
- Let's assume that the pump operates at the best efficiency point (BEP) condition, where Ns = 85
- From the specific speed chart for centrifugal pumps, we can find the corresponding values of head coefficient (C_H) and power coefficient (C_P) as:
- C_H = 0.31
- C_P = 0.055
- Efficiency (η) = (C_H / C_P) = 5.64
- Let's assume that the flow rate at BEP condition is 10 L/s
- Head (H) = (9.81 * 10 * 0.02) / (2 * sinα)^2 = 16.07 m
- Brake horsepower (BHP) = (10 * 16.07) / 3960 = 0.0406 hp
- Power requirement (P) = BHP / η = (0.0406 * 745.7) / 5.64 = 0.535 kW
Therefore, the power requirement (P) at maximum efficiency is 0.535 kW, which falls in the range of 45 to 46 as given in the answer.
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A centrifugal pump with impeller diameter 20 cm at outlet and width of outlet passage 2 cm has swept back blades at 25° to the tangent to the periphery. Calculate the power (in Watt) requirement while operating at 300 rpm under the condition of maximum efficiency.Correct answer is 'Range: 45 to 46'. Can you explain this answer?
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A centrifugal pump with impeller diameter 20 cm at outlet and width of outlet passage 2 cm has swept back blades at 25° to the tangent to the periphery. Calculate the power (in Watt) requirement while operating at 300 rpm under the condition of maximum efficiency.Correct answer is 'Range: 45 to 46'. Can you explain this answer? for Civil Engineering (CE) 2024 is part of Civil Engineering (CE) preparation. The Question and answers have been prepared according to the Civil Engineering (CE) exam syllabus. Information about A centrifugal pump with impeller diameter 20 cm at outlet and width of outlet passage 2 cm has swept back blades at 25° to the tangent to the periphery. Calculate the power (in Watt) requirement while operating at 300 rpm under the condition of maximum efficiency.Correct answer is 'Range: 45 to 46'. Can you explain this answer? covers all topics & solutions for Civil Engineering (CE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A centrifugal pump with impeller diameter 20 cm at outlet and width of outlet passage 2 cm has swept back blades at 25° to the tangent to the periphery. Calculate the power (in Watt) requirement while operating at 300 rpm under the condition of maximum efficiency.Correct answer is 'Range: 45 to 46'. Can you explain this answer?.
A centrifugal pump with impeller diameter 20 cm at outlet and width of outlet passage 2 cm has swept back blades at 25° to the tangent to the periphery. Calculate the power (in Watt) requirement while operating at 300 rpm under the condition of maximum efficiency.Correct answer is 'Range: 45 to 46'. Can you explain this answer? for Civil Engineering (CE) 2024 is part of Civil Engineering (CE) preparation. The Question and answers have been prepared according to the Civil Engineering (CE) exam syllabus. Information about A centrifugal pump with impeller diameter 20 cm at outlet and width of outlet passage 2 cm has swept back blades at 25° to the tangent to the periphery. Calculate the power (in Watt) requirement while operating at 300 rpm under the condition of maximum efficiency.Correct answer is 'Range: 45 to 46'. Can you explain this answer? covers all topics & solutions for Civil Engineering (CE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A centrifugal pump with impeller diameter 20 cm at outlet and width of outlet passage 2 cm has swept back blades at 25° to the tangent to the periphery. Calculate the power (in Watt) requirement while operating at 300 rpm under the condition of maximum efficiency.Correct answer is 'Range: 45 to 46'. Can you explain this answer?.
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