When air (or any gas) flows in tubes of different diameter, due to Venturi principle pressure in thin sections is smaller than pressure in thick sections. If speed of flow is great, the process of transition between sections can be considered adiabatic. It means that by entering thick section temperature of air increases due to increase of pressure. Since thick and thin sections have direct thermal contact, air flowing in thick section is heating air flowing in thin section. By entering thick section, that air heats up yet more (due to adiabatic increase of pressure). So, every new portion of air, entering thick section has greater temperature than previous portion – the process is recurrent. If there are no losses, the tip temperature will rise to infinity. If we use some part of heat or withdraw some air from the flow Voutlet, the temperature of outgoing air will be
Tout = Tin + ΔTadiabatic*V/Voutlet,
where Tin is temperature of incoming air; ΔTadiabatic is adiabatic increase of temperature at transition; V – volume of air, flowing through device per second; Voutlet – volume of air, exiting outlet holes per second.
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