A large amount of experimental data illustrating the influence of sound on temperature processes have accumulated in industry and technology research. A temporary lack of an adequate understanding of the physical basis of these processes is forcing us to refer these phenomena to a sequence of physical paradoxes. The Ranque effect and the Hartmann Sprenger effect also belong to this class of phenomena. The author discovered the temperature separation phenomenon in a short vortex chamber. Compressed air is pumped at room temperature from the side peripheral wall toward the centre of the vortex chamber. Experiments revealed that the highest temperature of the periphery was 465 C and the lowest temperature of the central zone was 45 C. This heat transfer process is looked similar to the above phenomena. None of these effects can be explained by conventional heat transfer processes. The concept of Pressure Gradient Elastic Waves (PGEW) is proposed and proved. The concept gives a physical description of the heat transfer in these processes. A PGEW is a special type of elastic wave arising in compressible fluids (gas) with pressure gradient in the presence of density fluctuations (sound). The most important property of this kind of elastic wave is that it transfers energy from a low pressure zone to a high pressure one.
