LIMITS OF TEMPERATURE SEPARATION IN A VORTEX TUBE

The heating and cooling in a vortex tube is attributed to conversion o f kinetic energy into heat and to the reverse process. A two-component model yields the upper limit for the temperature increase on the hot side: (T(h) - T0)/T0 less-than-or-equal-to X(gamma - 1)/gamma, and a l ower limit for the temperature reduction on the cold side: T(c) greate r-than-or-equal-to T0(1 - X)(gamma-1)/gamma, where gamma = 1.4 for air , and X = (p0 - p(c))/p0 is the normalized pressure drop between the i nlet (p0) and the cold exhaust port (p(c)). Extensive experimental dat a for a vortex tube of 18 mm inner diameter with working fluid air all fall between these limits. The model predicts that the inlet velocity reaches the speed of sound for X = 0.7. No values X > 0.7 could be ob tained in these experiments, indicating that the flow always remain su bsonic.