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Автор Джедай Геон в книжке своей от 1997г. писал: .... звуковое давление жидкости, проходящей от "теплой" до "холодной" стороны регенератора, формирует характерную движущую силу, направленную на нереверсивный поток, или силу, которая "несется" в направлении попутном распространению звуковой волны. Though the introduction of the secondary orifice usually led to increased efficiencies compared to the
OPTR, it also introduced a problem. Performance of the double inlet pulse tube refrigerator was not always
reproducible, and sometimes the cold end temperature would slowly oscillate by several degrees with
periods of several minutes or more. Researchers began attributing this erratic behavior to DC flow that can
occur around the loop formed by the regenerator, pulse tube, and secondary orifice. Asymmetric flow
impedance in the secondary can cause such a DC flow. Even small DC flow carries a large enthalpy flow
from the warm to the cold end because of the large temperature difference at the two ends. In 1997
Gedeon22 showed that the acoustic power flowing from the warm to the cold end of the regenerator brings
about an intrinsic driving force for DC flow or streaming in the same direction as the acoustic power flow.
As a result, an asymmetric secondary is required to cancel the intrinsic tendency for this DC flow. In the
author’s lab the use of a needle valve for the secondary with the needle pointing toward the warm end of
the pulse tube resulted in a no-load temperature on a small pulse tube refrigerator of about 35 K. When the
needle valve was reversed, the no-load temperature increased to about 50 K. A tapered tube, also known as
a jet pump, has also been used to cancel the DC flow23.
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