Optimization of Stirling and Ericsson Cycles Using Solar Radiation V. BADESCU+ SUMMARY A model is considered in this paper which consists of: (i) a source of radiation (the sun); and (ii) two energy converters. The first converters, an absorber, transforms the solar radiation into heat while the second one, a Stirling or Ericsson cycle engines, uses heat to produce mechanical work. Polarization coefficients were introduced to characterize the radiation emitted by the sun and the converter. The maximum conversion efficiency of sunlight into work was determined. Consideration of thermal equilibrium allowed a relationship between the polarization coefficients to he derived. Introduction It is well known that the higher the temperature a working fluid is heated to by a solar collector the lower the collector efficiency will be. However, heat engines are more efficient at higher heat supply temperatures. This indicates that any solar collector - heat engine combination will have an optimum operating temperature. The maximum global efficiency of such collector - engine combinations has been extensively studied. [ 1-9] The ideal case of a Carnot cycle engine has typically been described in the literature. Here I briefly study the case of Stirling and Ericsson cycle engines which might be used in actual space power applications. This has also been discussed by Howell and Bannerol, [3] as well as other authors who took different theoretical approaches. [10-12] The present approach is based on development of the model proposed by Landsberg and Baruch. [13] Power Generation and Conversion Efficiency Following Landsberg and Baruch, (13] I consider a system consisting of two large reservoirs - the pump (p) and the sink (s) - together with two converters. The first converter is the absorber (RI I) and it interacts with both the pump and the sink by interchange of isotropic radiation. In the RI I converter energy received as black body radiation at temperature T is received from the pump and transferred to the second converter - the heat engine (IIW) where it is partially transformed into mechanical work. When the sink docs not emit radiation the energy and entropy balance equations per unit area for the RI I converter arc: * Mechanica, Terniolechnica, Polytechnic Institute of Bucharest, Bucharest 79590 Romania.
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