Question: Is Head Loss Always Positive?

What is major head loss?

Major Head Loss – head loss or pressure loss – due to friction in pipes and ducts.

Minor Head Loss – head loss or pressure loss – due to components as valves, bends, tees and the like in the pipe or duct system..

What causes head loss?

The head, pressure, or energy (they are the same) lost by water flowing in a pipe or channel as a result of turbulence caused by the velocity of the flowing water and the roughness of the pipe, channel walls, or fittings. Water flowing in a pipe loses head as a result of friction losses.

Write the relation between head loss and pressure loss. Here, is the density of the flowing fluid, is the pressure loss, and g is the acceleration due to gravity. … Therefore, head loss of the flowing fluid is directly proportional to pressure loss.

What is K in head loss?

Introduction. The K-value, Resistance Coefficient, Velocity Head, Excess Head or Crane method allows the user to characterise the pressure loss through fittings in a a pipe. The K-value represents the multiple of velocity heads that will be lost by fluid passing through the fitting.

What is NPSH required?

NPSH Required (NPSHR): The minimum pressure required at the suction port of the pump to keep the pump from cavitating. … NPSHA MUST be greater than NPSHR for the pump system to operate without cavitating. Put another way, you must have more suction side pressure available than the pump requires.

Which pump is used for high head?

It is clear that PDP are used when we need high outlet pressure and dynamic pumps are used when we need high discharge. Based on this, and many other issues, there are specific applications where reciprocating pumps can be used.

What are the reasons for minor head losses in a pipe?

Major Head Loss – due to friction in pipes and ducts.Minor Head Loss – due to components as valves, fittings, bends and tees.

How is head loss calculated?

Evaluating the Darcy equation provides insight into factors affecting the head loss in a pipeline. If the length of the pipe is doubled, the head loss will double. If the inside pipe diameter is doubled, the head loss will be reduced by half. If the flow rate is doubled, the head loss increases by a factor of four.

What is pump head calculation?

Total Dynamic Head in an industrial pumping system is the total amount of pressure when water is flowing in a system. It is comprised of two parts: the vertical rise and friction loss. It is important to calculate this accurately in order to determine the correct sizing and scale of pumping equipment for your needs.

Is pressure drop good or bad?

Excessive pressure drop will result in poor system performance and excessive energy consumption. Flow restrictions of any type in a system require higher operating pressures than are needed, resulting in higher energy consumption. … There is also another penalty for higher-than-needed pressure.

Why is NPSH important?

The NPSH curve displays the minimum required inlet pressure (expressed in m) allowing the pump to pump in accordance with the performance curve and in order to prevent evaporation of the pumped fluid so as to avoid cavitation inside the pump.

What is negative head pump?

A negative head pump is used where the pump will be situated either level with or above the cold water tank. It then sucks water from the tank to feed the shower. This type may be needed in bungalows, for example, where there is insufficient head below the tank.

What does negative head loss mean?

We know that the head loss must be positive so we can assume a flow direction and compute the head loss. If the head loss is negative, we have assumed the incorrect direction.

Why is head loss important?

In the practical analysis of piping systems the quantity of most importance is the pressure loss due to viscous effects along the length of the system, as well as additional pressure losses arising from other technological equipments like, valves, elbows, piping entrances, fittings and tees.

Can total head be negative?

The suction static head (∆HSS) can either be negative or positive, depending on whether the pump centerline is below the suction fluid surface or above, and the value of suction tank fluid surface pressure head (H1). … The inlet of the system is located at point 1, which is the surface of the suction tank fluid.

What happens if NPSH is negative?

This pressure energy is referred to as Net Positive Suction Head. The NPSH is supplied from the system and is solely a function of the system design on the suction side of the pump. Consequently it’s controlled by the system designer. … If the liquid is below the pump, this becomes a negative value.

What is mean by head loss?

Head loss is potential energy that is converted to kinetic energy. Head losses are due to the frictional resistance of the piping system (pipe, valves, fittings, entrance, and exit losses). Unlike velocity head, friction head cannot be ignored in system calculations. Values vary as the square of the flow rate.

What is the difference between positive and negative suction head?

Distance of the liquid source above or below the pump inlet, measured in feet: can be positive OR negative. Positive suction head occurs when the top of the water source is above the suction Inlet of the pump. Negative elevation refers to suction lift (like from a pond, tank lower than the pump, etc.)

What is minor head loss?

The minor losses are any head loss present in addition to the head loss for the same length of straight pipe. Like pipe friction, these losses are roughly proportional to the square of the flow rate. Defining K, the loss coefficient, by. allows for easy integration of minor losses into the Darcy-Weisbach equation.

What does pressure head mean?

In fluid mechanics, pressure head is the height of a liquid column that corresponds to a particular pressure exerted by the liquid column on the base of its container. It may also be called static pressure head or simply static head (but not static head pressure).

Does head loss affect flow rate?

Head loss does not reduce the fluid velocity (consider a constant diameter pipe with a constant mass flow rate), and it will not be effect the elevation head of the fluid (consider a horizontal pipe with no elevation change from inlet to outlet).