1. A rotary heat exchanger comprising: a. structural support for supporting rotating shafts; b. a power input shaft journalled in bearings in said structure for rotation; c. a rotating rotor mounted on said power input shaft so as to rotate in unison therewith, said rotor having an axis of rotation, structural walls, a radial center, and a periphery said rotor having: i. first fluid passageway comprising: I. first entry port having a first area of opening and disposed near the center of said rotor so as to have a small first diameter and a first radius with respect to a central longitudinal axis of said power input shaft and said rotor; II. at least one first radially extending passageway having first means for ensuring that a first fluid therewithin rotates at substantially the same rotational speed as said rotor for effecting centrifugal compression and effecting a high pressure, compressed fluid at elevated temperature at the outermost periphery of said rotor; said first means serving as cooling means and being heat conductive for cooling said first fluid during centrifugal compression thereof; said first means being disposed adjacent a second fluid passageway for conducting heat to a second fluid in said second fluid passageway; III. a first peripheral portion communicating with said first radially extending passageway and peripherally disposed in said rotor for collecting said high pressure compressed fluid; IV. at least one second radially extending passageway communicating with said first peripheral portion and extending inwardly toward the center of said rotor; said second radially extending passageway having second means for recovering the work associated with deceleration of a compressed first fluid; and V. a first discharge port having a second area of opening that is operably sufficient for automatic flow of a first fluid and having a second diameter and a second radius with respect to said central longitudinal axis that are greater, respectively, than said first diameter and said first radius for effecting automatic flow of said first fluid and less than the respective diameter and radius of said peripheral portion for consuming less power and for effecting greater efficiency in operation; said first discharge port communicating with said second radially extending passageway for discharge of a first fluid therefrom; ii. second fluid passageway comprising: I. a second entry port having a third area of opening and disposed near the center of said rotor so as to have a small third diameter and third radius with respect to a central longitudinal axis of said power input shaft and said rotor; II. at least one third radially extending passageway having third means foR ensuring that a second fluid therewithin rotates at substantially the same rotational speed as said rotor; said third means serving as heating means and being heat conductive for heating said second fluid by heat conducted from said first fluid both during compression of said first fluid and at said first peripheral portion; III. a second peripheral portion communicating with said third radially extending passageway and peripherally disposed in said rotor for collecting said second fluid; IV. at least one fourth radially extending passageway communicating with said second peripheral portion and extending radially inwardly toward the center of said rotor; said fourth radially extending passageway having fourth means for recovering the work associated with deceleration of a second fluid; and V. a second discharge port having a fourth area of opening and having a fourth diameter and a fourth radius with respect to said central longitudinal axis that are less than the respective diameter and radius of said second peripheral portion for consuming less power and effecting greater efficiency of operation; said second discharge port communicating with said fourth radially extending passageway for discharge of said second fluid therefrom; and iii. heat conductive walls intermediate said first and second peripheral portions of, respectively, said first and second fluid passageways and said first and third means for conducting heat from said high pressure, compressed fluid at elevated temperature to said second fluid; d. a compressible first fluid being automatically passed through said first fluid passageway in said rotor without requiring energy exteriorly of said rotor; said first fluid being heated by centrifugal compression and transferring heat to said second fluid through at least said heat conductive wall intermediate said first and second peripheral portions and said first and third means such that said compressible first fluid is at a lower temperature at its outlet from said rotary heat exchanger than it was at its inlet thereto; and e. a second fluid being flowed through said second fluid passageway and being heated in at least its said peripheral portion by heat transferred from said first fluid such that said second fluid is at a higher temperature at its outlet from said rotary heat exchanger than it was at its inlet thereto.