Heat Transfer Coefficient

The heat transfer coefficient (alpha) is a calculated value used to assess the condition inside a heat exchanger. It measures the efficiency of heat transfer between a fluid and a solid surface.

To calculate the heat transfer coefficient, the following formula is used:

Q = alpha x A x (T2 - T1) x Delta t

where alpha represents the heat transfer coefficient, A is the heat transfer surface area, (T2 - T1) is the temperature difference, and Delta t is the examined time frame.

Alternatively, using accessible temperature and volume flow values, a qualitative heat transfer coefficient (alpha m) can be determined using inlet and outlet temperatures and volume flow rates.

Key characteristics include: the heat transfer coefficient depends only on the fluid, its movement and the surface of the solid body, however not on the material of the solid body. It is a process value rather than a material property. For example, when water remains still in tubes, possible heat transfer ranges from 350-500 W/(m2K), but when water flows, it can reach 350-2100 W/(m2K).

Fouling, the accumulation of deposits like dirt, limescale, rust, or biomass, acts as insulation and reduces heat transfer efficiency. Clean heat exchanger surfaces are essential for maintaining optimal heat transfer performance.