The pressure in one point of the network is the sum of energies of dynamic and static pressures. These transformations of energy are reversible or irreversible
the pressure loss is irreversible loss of pressure because the head loss is converted into heat or noise that we can not re-transformed into pressure.
The pressure generated by changing altitude or height of load (hydrostatic pressure) is reversible: If the duct up of 1 meter, and down of 1 meter, the balance is zero:
the pressure generated by the change in velocity (dynamic pressure) is reversible:If for a given flow a converging cone accelerates the fluid the pressure decreases (see Bernoulli), but if another diverging cone, positioned downstream, slows down the fluid to its original speed, the balance of dynamic pressure is zero:
Modeling a network of fluid (air flow, hydraulic or other) predicts the evolution of pressures, velocities and flow of operation of a network based on its parameters of implantation:
- Types of flow generators (fans, pumps, gravity flow, water tower ..)
- Vertical drop
- Pipe diameters (and their lengths and roughness)
- Elements passed through (junctions separations, reductions, elbows, valves ...)
- Branches or loops
- Calculations of flow rates, resulting from the Bernoulli, which gives the relationship of balance of energy between two points in a fluid stream
- sum of the energies of pressure entering in the network
- sum of the energies of pressure coming out of the network + pressure used by the network.
- Static pressure. The static pressure is provided by the pump, pressure tank or water tower
- the static load: height gradient between the entry point and exit point.
- Dynamic pressure: kinetic energy of the fluid entry
- the static load: height gradient between the entry point and exit point
- Dynamic pressure: kinetic energy of the fluid at the outlet of network
- For air systems, the static load due to vertical drop is negligible.
- For closed systems, energy dynamic pressure and the static load output are returned to the input, so it is ignored in the calculation of the energy needed to operate the system.
- In a closed network, the operating point depends only on to the head loss, and the pressure curve of the pump: The pump should provide a pressure equal to the sum of pressure losses.
- In an open network, the operating point depends on the losses, the vertical drop between the entry and exit points, and the kinetic energy (dynamic pressure) given to the fluid.