Thermal noise low temperature cold water machine

by:CBFI     2020-10-04
Low temperature refrigerator is one of the main direction of completely without moving parts. Drive based on the thermal effect of thermoacoustic refrigerator is an important representative, developing very rapidly in recent years. Simply put, thermoacoustic effect refers to the phenomenon of mutual transformation between heat and work. From the point of view of acoustics, it is compressible fluid acoustic oscillation and solid medium produced by thermal interaction between all ability effect. Can produce thermoacoustic effect of fluid medium compressibility, must have a larger thermal expansion coefficient, small prandtl number, and for large temperature difference, small energy flow density, fluid heat, for smaller temperature difference, and high energy flow density, fluid heat to play. Therefore, the ideal gas such as air, helium, helium, in particular, apply to a larger temperature difference, small energy flow density, the simple liquid of near critical area, such as CO2, simple hydrocarbons, etc. , applicable to small temperature difference, and high energy flow density.

the concept of thermoacoustic refrigeration is the LosAlamos national laboratory firstly, etc are put forward in the 1980 s. In the hot end of the resonance tube input acoustic power, working gas in the resonance tube by adiabatic compression and booster effects from inflation. In hot air is compressed at left stack, temperature rise, then to the plate stacked hot. In hot plate fold the right end of gas adiabatic expansion, the temperature is lower than the local stack temperature, air mass from the endothermic stack. Such waves of each cycle, the air will heat from the hot plate fold the right end to the left end of the transfer, make on both ends of the temperature difference increases, the refrigeration effect.

of stack based on thermoacoustic acoustic field type, type can be divided into standing wave thermoacoustic machine type and travelling-wave thermoacoustic machine. Of standing-wave thermoacoustic machine run time based on the internal irreversibility of thermodynamic cycle, and the irreversible heat transfer between gas and board fold caused by entropy limits the standing-wave thermoacoustic machine efficiency, its thermodynamic efficiency often can't be very high, generally at 0. 2 the following. Machine is similar to travelling wave thermoacoustic Stirling thermodynamic cycle, and the process is the intrinsic reversible, therefore travelling-wave thermoacoustic machine efficiency is higher than in theory has the intrinsic irreversibility of standing-wave thermoacoustic machines.
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