Energy Loss in Bends

Theoretical Basis

The study of the energy losses suffered by a current when it circulates through a hydraulic circuit is vital in the industrial processes where the fluids are used. The causes of energy losses of a fluid when it circulates through a pipe at constant pressure are the following ones:

• Variations of the potential energy of the fluid
• Variations of the kinetic energy
• Friction

The equipment of Local Load Losses studies the losses of kinetic energy of a fluid that circulates through a pipe. These are caused mainly by abrupt variations of velocity due to:

• Abrupt changes of pipe section: widening or narrowing’s
• Perturbation of the normal current flow, due to changes of direction caused by the existence of an elbow or a curve.
• Friction

Practical possibilities

The equipment of Local Load Losses allows observing the load losses experienced by a current of fluid that circulates by a hydraulic system when sudden section or direction variations take place. The valve of flow regulation allows the study of the local load losses suffered by the current in function of the system flow.

• Filling of the manometric tubes
• Measurement of the flow
• Measurement of load losses for a short elbow of 90°, long elbow of 90°, curve of 90°, widening, narrowing, miter and membrane valve. 

Apparatus

1. Manometers
2. PVC Rigid pipes
3. Flexible pipes
4. Widening
5. Narrowing
6. Valves
7. Hydraulic Bench
8. Chronometer

Description

The equipment of Local Load Losses consists of a hydraulic circuit with a set of elements that disrupt the normal flow of the fluid which circulates by the pipe, because of sudden section and direction variations, as well as friction.

These elements are:

1. Two elbow of 90°, a short one and a middle one
2. A curve of 90° or long elbow
3. A widening
4. A sudden section narrowing
5. A sudden direction change, miter type

The equipment has two manometers, Bourdon type: 0 – 2.5 bar and twelve manometric pipes of pressurized water. The system pressurization is carried out with a manual air pump. The hydraulic circuit has pressure takings along the whole system, which enables to measure the Local Load Losses in the system. This equipment has two membrane valves, a valve which enables the regulation of the outlet flow and a valve placed in series with the rest of accessories of the hydraulic circuit. 

Working Procedure

Measurement of load losses for:

a)      long elbow of 90°

b)      widening

c)      narrowing

d)     middle elbow of 90°

e)      short elbow of 90°

f)       miter

g)      membrane valve

a.     We have to assemble the equipment on the Hydraulic Bench.

b.     We have to connect the input tube from the equipment to the pulse mouth of the bench with the quick switch and we connect a flexible conduct to its outlet, so that it can drain in the volumetric tank.

c.     We filled the manometric pipes with water.

d.     When the system is pressurized, the pump is turn on and we gradually open and slightly the valve of the Bench or Group VC, while we open gradually the control valve of the equipment, VVC.

e.     We have to carried out this procedure in a very softly way, in order to avoid that the measurements are out of the scale.

f.      When the valve of Bench or Group is completely open, we regulate the flow with the control valve of the equipment, VVC.

g.     We write down the readings indicated in the manometrics pipes which are associated with the short elbow of 90°, long elbow of 90°, curve of 90°, widening, narrowing, miter and membrane valve.

h.     We also determined the water flow, we also writing down all these values.

i.      The flow control valve of the Bench is closed.

j.      The previous steps are repeated varying the flow by opening the control valve of the equipment.

k.     We complete the following table in appendix as results.

It is possible that when measuring some elements are out of the scale, which disrupts the measuring that we are carrying out. In order to avoid this, you can close the manometric valves of the pipes associated to these elements.