rinnakkaisvirtalämmönvaihdin

Rinnakkaisvirtalämmönvaihdin is a type of heat exchanger where the two fluids flow in the same direction. This is in contrast to counter-current heat exchangers, where the fluids flow in opposite directions, or cross-flow heat exchangers, where the fluids flow perpendicular to each other.

In a parallel flow heat exchanger, the hot fluid enters at one end of the exchanger and flows along its length, while the cold fluid enters at the same end and flows in the same direction. As the fluids travel through the exchanger, heat is transferred from the hot fluid to the cold fluid. The driving force for heat transfer is the temperature difference between the two fluids.

A key characteristic of parallel flow heat exchangers is that the temperature difference between the two fluids is greatest at the inlet and decreases along the length of the exchanger. This means that the effectiveness of heat transfer is lower compared to counter-current flow, as the cold fluid never reaches as high a temperature as it could, and the hot fluid never reaches as low a temperature as it could. Consequently, for a given heat transfer area, a parallel flow heat exchanger will transfer less heat than a counter-current one.

Despite this limitation, parallel flow heat exchangers have their applications. They can be simpler to construct and may be preferred in situations where the risk of thermal stress due to large temperature differences between the inlet and outlet is a concern. They can also be useful when a high degree of mixing of the fluids is undesirable or when the pressure drop needs to be minimized in a specific flow path. The choice between parallel flow, counter-current, or cross-flow depends on the specific design requirements, desired efficiency, and cost considerations for a particular application.