What forms of flow are commonly encountered in boilers?

During the flow of a fluid, each particle moves in a straight line along the axis of the tube; a flow state in which the particles do not mix with or interfere with one another is known as laminar flow. When a moving particle not only moves in a straight line along the axis of the tube but also experiences lateral disturbances, causing the particles to mix with one another and the flow lines to become disordered, this state of flow is called turbulence. In boilers, the flow state of real fluids such as water, steam, flue gas, air, etc., is almost always turbulent; only liquids with high viscosity (heavy oil, lubricating oil) exhibit laminar flow at low velocities. The flow state of liquids has different advantages and disadvantages in various situations. When the fluid is in a turbulent state, the intense disturbances between molecules are beneficial for enhancing heat transfer. However, due to turbulence, the flow resistance must increase, resulting in higher energy losses.