What method involves heat transfer by circulation within gas or liquid?

The method that involves heat transfer by circulation within a gas or liquid is convection. In this process, warmer parts of a fluid (which can be either a gas or a liquid) become less dense and rise, while cooler, denser parts sink. This creates a continuous circulation pattern that facilitates the transfer of heat.

Convection is fundamental in processes such as boiling water or the distribution of heat in a room from a heating system where warmer air rises and cooler air is drawn in to replace it. Understanding this concept is critical in fire dynamics, as it explains how heat influences fire spread and behavior within different environments.