Question

Explain with your own words, how turbulence increases heat transfer.

Answer 1

Type of flow is characterized by the Reynolds number. if Reynolds number is greater than 2300 for pipe flow, flow is characterized as turbulent and if Re number is greater than 500000 for flat plates, flow is characterized as turbulent flow. Turbulent flow leads to enhanced dissipation due to better mixing of fluid compared to laminar flow.

In laminar flow where streamlines slide one another, molecules travel in the well-defined path, heat transfer takes due to molecular diffusion. Since there is no mixing of the fluid, energy transfer takes place by pure conduction from one layer of fluid to another layer. Usually, the thermal conductivity of fluids is less which leads to less energy transfer.

unlike laminar flow, In turbulent flow, the flow passes better mixing characteristics. Irregular velocity fluctuations due to turbulent motion are the primarily responsible factor for heat transfer as well as momentum transfer. innumerable eddies generated by the turbulent motion enhances energy transfer. Frictional coefficients are much higher here compared to laminar flow which enhances heat transfer. Due to cross flow characteristics of turbulent flow, fluid particle collied with each other at random and give up their energy. In addition to conduction like laminar flow, better mixing of fluid particles and fluid layers enhance heat transfer as they give up energy each other while colliding each other.