Power plants – Motor operated by expansion and/or contraction of a unit of... – Unit of mass is a gas which is heated or cooled in one of a...
Patent
1982-07-28
1983-11-08
Ostrager, Allen M.
Power plants
Motor operated by expansion and/or contraction of a unit of...
Unit of mass is a gas which is heated or cooled in one of a...
60517, F02G 104
Patent
active
044134754
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to Stirling-cycle engines, also known as regenerative thermal machines, and more particularly to a new family of thermodynamic working fluids for such machines. The working fluids of the present invention are specifically selected with regard to whether or not they possess a high dynamic heat transfer coefficient, as defined by known empirical relations for heat transfer in turbulent flows, in addition to other requisite thermophysical properties such as chemical inertness and thermal stability. They are disclosed to be improved agents for use in all heat engines which embody a practical approximation to the well known Stirling thermodynamic cycle and which are employed in the production of both mechanical power (i.e., prime movers, compressors, fluid pumps) and refrigeration (i.e., refrigerators, air conditioners, heat pumps, gas liquefiers).
A Stirling-cycle engine is a machine which operates on a closed regenerative thermodynamic cycle, with periodic compression and expansion of a gaseous working fluid at different temperature levels, and where the flow is controlled by volume changes in such a way as to produce a net conversion of heat to work, or vice versa. The regenerator is a device which in prior art takes the form of a porous mass of metal in an insulated duct. This mass takes up heat from the working fluid during one part of the cycle, temporarily stores it within the machine until a later part of the cycle, and subsequently returns it to the working fluid prior to the start of the next cycle. Thus the regenerator may be thought of as an oscillatory thermodynamic sponge, alternately absorbing and releasing heat with complete reversibility and no loss.
A reversible process for a thermodynamic system is an ideal process, which once having taken place, can be reversed without causing a change in either the system or its surroundings. Regenerative processes are reversible in that they involve reversible heat transfer and storage; their importance derives from the fact that idealized reversible heat transfer is closely approximated by the regenerators of actual machines. Thus the Stirling engine is the only practical example of reversible heat engine which can be operated either as a prime mover or as a heat pump.
BACKGROUND
The Stirling-cycle engine was first conceived and reduced to practice in Scotland 164 years ago. A hot-air, closed-cycle prime mover based on the principle was patented by the Reverend Robert Stirling in 1817 as an alternative to the explosively dangerous steam engine. Incredibly, this event occured early in the Age of Steam, long before the invention of the internal combustion engine and several years before the first formal exposition of the Laws of Thermodynamics.
Air was the first and only working fluid in early 19th century machines, whereas hydrogen and helium have been the preferred working fluids for modern machines. In Great Britain, Europe, and the United States thousands of regenerative hot air prime movers in a variety of shapes and sizes were widely used throughout the 19th century. The smaller engines were reliable, reasonably efficient for their time, and most important, safe compared with contemporary reciprocating steam engines. The larger engines were less reliable, however, because they tended to overheat and often succumbed unexpectedly to premature material failure.
Toward the end of the 19th century the electric motor and the internal combustion engine were developed and began to replace not only the Stirling-cycle engines, but also the reciprocating steam engines of that era. These new machines were preferred because they could produce greater power from more compact devices and because they were more amenable to simple power level controls. Both of these limitations of the original Stirling engine are directly attributable to the use of air as the working fluid. That is, the specific power capacity and the overall mechanical complexity of a practical Stirling-cycle machine are direct consequences of the inherent p
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Morton, Jr. W. Brown
Ostrager Allen M.
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