CHAPTER-3

FLOW THROUGH PIPES

• Q1: Define Loss of Head in Pipes.
  Ans: Loss of head in pipes is the reduction in energy or pressure of a liquid as it flows through a pipe. It occurs due to friction and other disturbances in the flow.
• Q2: Define Reynold’s Number.
  Ans: Reynold’s number is a dimensionless number used to determine the type of flow (laminar or turbulent).
  Formula:
  
  Re = (ρVD) / μ
  
  Where:
  ρ = density
  V = velocity
  D = diameter
  μ = viscosity.
• Q3: Define Critical Velocity.
  Ans: Critical velocity is the maximum velocity of a liquid at which the flow remains laminar. If velocity increases beyond this value, the flow becomes turbulent.
• Q4: Define Lower Critical Velocity.
  Ans: Lower critical velocity is the velocity below which the flow is always laminar.
• Q5: Define Upper Critical Velocity.
  Ans: Upper critical velocity is the velocity above which the flow is always turbulent.
• Q6: Name various Loss of Head of a liquid flowing in pipes.
  Ans: The various Loss of Head of a liquid flowing in pipes are as follows:

  • ➔ Major Head Loss
  • ➔ Loss of Head due to Friction
  • ➔ Minor Head Loss
  • ➔ Loss of Head due to Sudden Enlargement of Pipe
  • ➔ Loss of Head due to Sudden Contraction of Pipe
  • ➔ Loss of Head at the entrance of Pipe
  • ➔ Loss of Head in Bends, valves etc.
• Q7: What is Loss of Head due to Friction?
  Ans: Loss of head due to friction is the loss of energy caused by friction between the flowing liquid and the inner surface of the pipe. It is a major head loss.
• Q8: What is Darcy’s Formula for Loss of Head in Pipes?
  Ans: Darcy’s formula is used to calculate head loss due to friction in pipes.
  Formula:
  
  h_f = (fL V²) / (2gD)
  
  Where:
  f = friction factor
  L = length of pipe
  D = diameter
  V = velocity
  g = acceleration due to gravity.
• Q9: What is Chezy’s Formula for Loss of Head in Pipes?
  Ans: Chezy’s formula is used to calculate velocity of flow in pipes.
  Formula:
  
  V = C √(RS)
  
  Where:
  C = Chezy’s constant
  R = hydraulic radius
  S = slope of energy line.
• Q10: What is Loss of Head due to Sudden Enlargement of Pipe?
  Ans: Loss of head due to sudden enlargement occurs when liquid flows from a smaller pipe to a larger pipe suddenly. The velocity decreases and some energy is lost due to turbulence.
  Formula:
  
  h_e = (V₁ − V₂)² / 2g
  
  Where:
  V₁ = velocity in smaller pipe
  V₂ = velocity in larger pipe.
• Q11: What is Loss of Head due to Sudden Contraction of Pipe?
  Ans: Loss of head due to sudden contraction occurs when liquid flows from a larger pipe to a smaller pipe suddenly. The velocity increases and energy is lost due to formation of eddies.
  Formula:
  
  h_c = (V₂² / 2g) × ( (1/C_c) − 1 )²
  
  Where:
  V₂ = velocity in smaller pipe
  C_c = coefficient of contraction
• Q12: What is Loss of Head at the entrance of Pipe?
  Ans: Loss of head at the entrance of pipe occurs when liquid enters the pipe from a tank or reservoir. Energy is lost due to sudden change in flow direction and area.
  Formula:
  
  h_en = K (V² / 2g)
  
  Where:
  K = entrance loss coefficient
  V = velocity in pipe.
• Q13: What is Loss of Head due to Bend in a Pipe?
  Ans: Loss of head due to bend occurs when liquid changes direction in a pipe bend. Energy is lost due to friction and turbulence at the bend.
  Formula:
  
  h_b = K (V² / 2g)
  
  Where:
  K = bend loss coefficient
  V = velocity of flow
• Q14: What is Loss of Head due to Pipe Fittings?
  Ans: Loss of head due to pipe fittings occurs because of valves, tees, reducers and other fittings. These fittings disturb the smooth flow and cause additional energy loss.
  Formula:
  
  h_f = K (V² / 2g)
  
  Where:
  K = loss coefficient of fitting
  V = velocity of flow.