Uneven heating can induce unequal flow distribution between the channels, which is undesirable in heat sinks as the channels starved of flow may undergo a premature dry-out, thereby impairing their heat transfer performance, and limiting predictability and reliability. In Liquids and gases, heat transfer takes place by convection. Heat transfer takes place by the process of radiation when there are no particles of any kind which can move and transfer heat. So, in an empty space or vacuum heat is transferred by radiation.

Uneven-heat-transfer is probably the practical norm: thus, in heat exchangers the flows are never uniform (or ideal) and we have to allow for flow asymmetry as best we can. Even-heating is almost an academic case: allowing easier numerical or analytical solutions, that must then have allowances for the non-uniformity.

Dr Jack broughton thank you for your contribution to the discussion

Convection is the main method of heat transfer in fluids such as water and air. In gases, heat transfer takes place by convection. In this process, heat is transferred in the liquid and gases from a region of higher temperature to a region of lower temperature. Convection heat transfer occurs due to the actual movement of molecules. In Liquids and gases, heat transfer takes place by convection. Heat transfer takes place by the process of radiation when there are no particles of any kind which can move and transfer heat. So, in an empty space or vacuum heat is transferred by radiation. Heat can be transferred in liquids or gases by convection. Liquids and gases are fluids because they can be made to flow. The particles in these fluids can move from place to place. Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy. Conduction occurs more readily in solids and liquids, where the particles are closer together than in gases, where particles are further apart. The rate of energy transfer by conduction is higher when there is a large temperature difference between the substances that are in contact. Uneven heating can induce unequal flow distribution between the channels, which is undesirable in heat sinks as the channels starved of flow may undergo a premature dry-out, thereby impairing their heat transfer performance, and limiting predictability and reliability Unequal heating of the earth's surface causes temperature differences which cause pressure differences. Lower temperatures cause higher air pressure. Wind direction is described as where the wind is coming from. The unequal heating of the Earth's surface is caused by the orbiting of the Earth around the Sun. The Earth and the Sun is a sphere, and when the Earth revolves around the Sun, the center of the Earth receives more sunlight than the poles and becomes hotter than other parts of the Earth.