A density equation for saturated vapor and liquid 3 He is presented based on 205 experimental measurements for temperatures greater than 0.2 K collected after a careful survey of the literature. The average deviation of the densities predicted by the equation against the experimental values is 0.39%. There are only 16 points with deviations larger than 1%. This equation is valid for both liquid and vapor densities of 3 He up to the critical temperature of 3.3157 K. The form of the equation satisfies known scaling laws approaching the critical point, with β = 0.3653. In the low-density limit, the vapor curve of our equation matches smoothly to the published virial equation density at a temperature of 1.62 K and at the saturation pressure. The rectilinear density deviates from the critical density by less than 0.28% down to 0.48 K.
Thermoacoustic effect, as a subprocess of the photoacoustic effect, can also convert heat to acoustic wave by a thermoacoustic prime mover, and can also pump heat by acoustic wave in a thermoacoustic refrigerator. The present study focuses on a thermoacoustically driven pulse tube refrigerator, utilizing sound from a thermoacoustic prime mover to drive a pulse tube refrigerator. Experiments emphasize on the characteristics of both the thermoacoustic prime mover and the combined refrigeration system, including resonant frequency, onset temperature, pressure amplitude, and refrigeration temperature, etc. A cryogenic temperature lower than 120 K has been achieved from the present system. Much effort is also devoted to the influence of some working gases, such as helium–argon mixture, on the performance of the system.
A new form of a fluid state equation, based on a conceptual extrapolation from the Debye equation for the specific heat of solid materials is described. The Debye characteristic temperature, , which is nominally a constant for solids, becomes a function of the fluid density ρ. Further assuming = c 1 ρ 2/3 (1 + c 2 ρ + c 3 ρ 2 + · · ·) yields the conventional fluid virial equation in the high-T and low-ρ limits for a monatomic fluid. Additional terms must be added to describe (a) the compressibility of the dense subcooled fluid and (b) properties in the near-critical range. Discussion of the Gruneisen parameter and other factors is included. This Debye fluid theory was used as a state equation for 3 He, continuous from 0.005 K to above room temperature.
On the basis of the equation of state and the phase equilibrium equations of helium-3 ( 3 He), a computer program for calculating the thermodynamic properties of 3 He has been created. With this program, many iso-property tables were prepared for generating p-h and T-s diagrams of 3 He over the range of temperature from 0.2 K to 300 K and pressures up to 300 MPa. Compared with the previous diagrams plotted with interpolated experimental data sets, the new ones are more thermodynamically consistent and cover a broader temperature and pressure range. The estimated overall random errors of the diagrams are within 2 %.
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