Lisäpainehäviöitä

Lisäpainehäviöitä, known in English as additional pressure losses or minor losses, refer to the energy losses that occur in a fluid flow system beyond the friction losses along straight pipes. These losses are generally smaller in magnitude compared to friction losses, hence the term "minor losses," but they can become significant in systems with many fittings or changes in direction.

These additional losses arise from disturbances in the flow pattern. When fluid passes through components like valves, elbows, tees, expansions, or contractions, the smooth, streamlined flow is disrupted. This disruption leads to turbulence, recirculation zones, and eddies, all of which dissipate energy from the flow, converting it into heat. For example, a sharp 90-degree elbow causes significant flow separation and turbulence, resulting in a noticeable pressure drop. Similarly, sudden changes in pipe diameter, either an increase (expansion) or decrease (contraction), force the fluid to change its velocity and direction, leading to further energy dissipation.

Quantifying lisäpainehäviöitä is typically done using a loss coefficient, often denoted by 'K' or 'ζ'. This dimensionless coefficient is specific to each type of fitting or component and is determined experimentally. The pressure loss due to a specific fitting is then calculated by multiplying the loss coefficient by the dynamic pressure of the fluid, which is proportional to the square of the fluid's velocity. The total additional pressure loss in a system is the sum of the individual losses from all fittings and components. Accurate calculation of these losses is crucial for proper system design, ensuring adequate flow rates and preventing undersized pumps.