What is Head loss: Definition and 36 Discussions

Hydraulic head or piezometric head is a specific measurement of liquid pressure above a vertical datum.It is usually measured as a liquid surface elevation, expressed in units of length, at the entrance (or bottom) of a piezometer. In an aquifer, it can be calculated from the depth to water in a piezometric well (a specialized water well), and given information of the piezometer's elevation and screen depth. Hydraulic head can similarly be measured in a column of water using a standpipe piezometer by measuring the height of the water surface in the tube relative to a common datum. The hydraulic head can be used to determine a hydraulic gradient between two or more points.

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  1. N

    Effect of pressure due to change in diameter of pipe

    The pump has an outlet size of 4 inch 1) In case 1, 4 inch pipe is connected at length of 20 m 2) In case 2, 2 inch pipe is connected using reducer In both cases the pump outlet conditions are same( having same flow rate at a given pressure) What happens to pressure at the end of the pipe in...
  2. Y

    Estimating head loss from pipe slope?

    I am trying to calculate head loss for a sloped pipe. I found this calculation here, which seems to be what I want..or at least a start: https://www.pumpsandsystems.com/pumps/april-2015-calculating-head-loss-pipeline My confusion/skepticism arises from the fact that the equations in the above...
  3. P

    Pressure required for water discharge

    Hello everyone, I am very interested in knowing the relation to determine the pressure required to push the water upstream. In the attached picture, water is filled inside a tank of volume V and air is constantly flowing inside the tank through an inlet with constant flow rate M. Water should...
  4. M

    Fluid Mechanics: Head Loss Question (Conceptual)

    I am not really worried about the numbers, but more about the simple concepts with head loss in these pipe flow questions. I want to confirm that head loss just means the change in static head, right? I have been advised that for a problem like this, it is nothing more than the conservation of...
  5. O

    Hydraulic Head Loss (minor) loss coefficient References?

    Hi all, Quick question: What do you guys use as your reference for minor head loss coefficients (k). I'm sure those with more experience have their own database/excels of k values found over the years. I have been personally using a combination of my Hydraulic Engineering Textbook and Google...
  6. physea

    I Head loss in a circuit of pump and pipes

    Hello! In an experiment (I don't have the details) the predicted head loss in a circuit of pump and pipes was higher as the flow rate increased, than the actual head loss (pressure differential). Can you tell me please what could result in that? What systematically acting factor created an...
  7. hdp12

    Fluid Mechanics: Bernoulli & Energy Equations Problem- Help?

    Hello there. I took a test yesterday in my thermal fluids 1 class and I was hoping somebody could confirm or critique my answer. (Don't worry, I asked the professor first if I could take the picture) The problem is: Water is pumped from a lake to a pool through a 0.05 m diameter pipe. System...
  8. M

    Some questions on pressure drops and head loss in pipe flow

    I would like to ask you that why pressure drop is constant through pipe? How can we know that dP/dx=constant? Thank you.
  9. S

    Calculating flow rate through turbine

    Hi guys, First post on this forum. Greetings from the Netherlands :) I am currently in the process of designing a turbine used in locks in several canals. The turbine is powered when the lock chamber is being emptyed during the lockage. The goal is to calculate the water level in the lock...
  10. F

    Understanding the Formulas for Major Head Loss in Pipes

    Homework Statement why the author use major loss due to fluid friction is fL(Q^2) / 3(d^5) ? according to darcy weisbech , the major loss due to friction has the formula of fL(v^2) / 2gD why the author wrote it as fL(Q^2) / 3(d^5) ? I don't understand Homework EquationsThe Attempt at a...
  11. F

    How does pipe thickness affect head loss at entrance?

    Homework Statement I was told that for loss of head at entrance , the degree of contaction depends on how thick the pipe walls is . i really don't know the meaning , can someone clarify ? the author also stated that the loss coefficients will vary , for very thin tubes , k is very high ? head...
  12. F

    Calculating Major Head Loss Due to Pipe Friction

    1. The problem statement, all variables and given/known i am having problem of finding the major loss caused by pipe friction in this question. the formula of major loss is given by fL(V^2) / 2gD , how to get the total length of pipe so that i can gt the major head loss? . Relevant equationsThe...
  13. G

    Calculate head loss per meter clarification

    Calculate the head loss per metre length of a capillary tube which has a bore radius of 0.45 mm when a fluid of density 850 kg/m3 and viscosity of 25 cP is flowing at a rate of 50 l/hr. State whether the flow is turbulent or laminar. I have attached my attempt at a solution using poiseuille's...
  14. R

    Fluids: Energy equation involving head loss

    Homework Statement See attached image: Homework Equations p/ρg + V^2/2g + z = constant head loss (major) = f * l/D * V^2/2gThe Attempt at a Solution To use the energy equation while incorporating head loss, I need to determine the velocity in each section of pipe. The problem is I don't know...
  15. F

    How to calculate head loss in a pipe with sudden diameter expansion?

    Homework Statement estimate the energy head lost along a short length of pipe suddenly enlarging a diameter of 350mm to 700mm which discharges 0.7(m^-3) of water per second . the solution given is Q1= Q2 = 0.7(m^3)/s 0.7 = pi ((350x10^-3)^2 ) V1 / 4 , V1= 7.28m/s 0.7 = pi ((700x10^-3)^2 ) V2 /...
  16. F

    How Do You Calculate Head Loss in a Venturi Meter Using Bernoulli's Equation?

    Homework Statement A venturi meter is being calibrated horizontally and has a diameter of 75mm at the entrance and 50mm at the throat . The flow rate is obtained by measuring the time required to collect certain amount of water . The average number of measurement gives 0.614m^3 of water in...
  17. M

    Head Loss and Pressure Rise During Gradual Expansion

    Homework Statement , There is an Head Loss question, two pipes join and expanding parts 30 degrees from the horizantal. Homework Equations The Attempt at a Solution Before attemting a solution I try to understand what a1=a2=1.06 is? Would you like to give some information about it...
  18. F

    Head loss formula in series pipe

    Homework Statement i know that the formula of head loss is (V^2) / 2g , where v =velocity , but , why did the author want to change it to k[(Q)^1/n ] ? Homework EquationsThe Attempt at a Solution
  19. Mingsliced

    Fluid Mechanics - Head Loss Due to Friction

    Homework Statement This is simply a sanity check concerning the system described and attached. My concerns are detailed within my attempts at the solution. Any guidance will be greatly appreciated! The diagram attached represents a process for which a pump and associated pipe work require to...
  20. W

    Head Loss Formula: Gamma Meaning Explained

    Homework Statement what does the gamma in the formula mean ? since the other terms in the formula are the same , i can just cancel it, leaving μ / γ = v /g . So , γ has unit of kg(m^-2)(s^-2) ? Homework EquationsThe Attempt at a Solution
  21. KrisOhn

    Head loss equaling head pressure?

    If you had a fluid in a pipe, with say, 10m of head pressure, what would happen when the head losses of the pipe equaled the head pressure?
  22. T

    Thermofluids, bernoullis equation head loss

    Hi, I just have a few questions on bernoullis equation dealing with power and head loss If the equation for power is p = mass flow rate * g * Hloss, Then is g only used when let's say a pipe is at an elevation ?, because in my book I have an example where g is not used to calculate the power...
  23. E

    Does the flow rate and pressure decrease as the exit height of a pump increases?

    OK, So I have been having an on and off debate with my family about this. I saw a pump at Home Depot that said it has a 30 ft head. Then it went on to show that the flow rate varied as the output of the pump changed in height. Now I thought that this was wrong. I just finished a course in...
  24. C

    Minor head loss for turbulent vs. laminar fluid flow

    Hi, I need clarification on the difference in head loss for turbulent flow and laminar flow. I understand how the head loss due to friction is different for the two regimes. For friction head loss, the friction factor is 64/Re for laminar flow, and a more complex formula for turbulent flow. I...
  25. E

    How to Calculate Flow Rate from Head Loss in a 3 Pipe with Caustic Soda?

    I have head loss (25.95ft) and converted that to pressure (17.19psi). I am trying to find flow rate in 3" sch 80 pipe coming from railcar at 25psi. So outlet pressure is 7.813psi. The fluid is 50% Caustic soda.
  26. Z

    Can head loss be added in parallel like resistors in circuits?

    Homework Statement I have three valve/coil systems connected in parallel as shown in the attached figure. If I know the head loss of each valve/coil is 40 feet, can I add them in parallel like you do with resistors in circuits? Thanks! Homework Equations 1/h=1/h1+1/h2+1/h3 (possibly)...
  27. T

    Head Loss in Pipe - Roughness, Velocity, Length

    Water flows through a horizontal 150 mm diameter pipe with a mean velocity of 2.5m/s. The surface roughness of the pipe is 0.15mm. Determine the head loss in a 30m length of the pipe. Hints, use moody chart, Re = ρVD/μ. Been having trouble with the question, can't seem to do it.
  28. P

    How can the velocity at points of change in pipe systems be determined?

    For minor losses, I read that the pressure drop is equal to the dynamic pressure * loss coefficient. However, in calculating dynamic pressure, it uses a single velocity. How do you determine this velocity when it will vary at the point of change in pipe diameter or direction? I have read...
  29. A

    What are Some Good Online References for Head Loss Coefficients in Ductwork?

    I am working on a project at my summer internship rerouting some duct work and want to do some calculations to see how much changing some of the 90 degree angles in the duct will improve flow. I don't have my Fluids text with me and was wondering if anyone knew of any good references online to...
  30. Z

    Calculating Head Loss in Pumping System for Swimming Pool Design

    Homework Statement I have to design a pumping system. Its for a swimming pool. The pool has various fittings (valves, etc) and pipe lengths. My problem is I cannot find an appropriate K value for the filter and sieve. On the suction side of the pump is various valves and a sieve to...
  31. J

    Calculating Head Loss from Enlargement in Compressible Fluid

    how to calculate head loss due to sudden enlargement in case of compressible fluid? hiiiiii guys, am graduate student, i want to know @ head loss in case of compressible fluid due to sudden enlargement...pls help me ...as soon as possible...
  32. P

    Fluids - Head Loss complicated

    Homework Statement Heated air at 1 atmosphere and 35 deg. Celsius is to be transported in a 150 meter long circular plastic duct (smooth) at a rate of 0.35 cubic meters/sec. If the head loss in the pipe is not to exceed 20 meters, determine the minimum diameter of the duct. Homework...
  33. P

    Head loss due to sudden expansion

    Hi all, I'm sure a lot of you know about the head loss due to sudden expansion: Hl = (1/2g)*(v1-v2)^2 This equation can be derived from Bernoulli, continuity and momentum balans equations. The underlying assumption in deriving this equation is that the pressure just after the expansion...
  34. S

    What causes equal head loss in 3 pipes of different diameters?

    Hey, If you have 3 pipes of different diameter flowing into another.. what needs to be true for the head loss in the 3 pipes to all be equal? ie Hf1 = Hf2 = Hf3 Cheers. :S
  35. T

    Head Loss Calculation: Discrepancies?

    I was reading on this page... http://www.cda.org.uk/megab2/build/pub125/sec4.htm#5.1 ...and I tried calculating head loss using both the forumla given, and the nomogram. Aren't these supposed to give the same result? Or am I missing something fundemental? Because they don't equal each...
  36. T

    Calculating Flow Rates in Pipe Networks: Head Loss Equations

    Hi. I'm trying to determine the flow rates of water in a pipe network. At a junction in a pipe, for example a simple y junction where the water heads out of a tap down a short length of tube before splitting into two lengths of tube of the same diameter, would the head loss equation for one of...
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