Critical Flow of Dense Gases - Modeling and Experimental Validation

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:HyphenationZone>21</w:HyphenationZone> <w:DoNotOptimizeForBrowser /> </w:WordDocument> </xml><![endif]--> <p class="MsoNormal" style="margin: 0cm 14.2pt 0.0001pt; text-align: justify; line-height: normal;"><span style="font-size: 10pt; font-family: &quot;Times New Roman&quot;;" lang="EN-US">The critical mass flow of dense gases strongly depends on real gas effects. In the present work the detailed assessment of the <span style="color: black;">critical flow conditions and the limiting mass velocity in the flow of refrigerants has been experimentally verified. C</span>ritical flow function <em>C* </em>data for <em>R-410A</em> and <em>R-507A</em> have been predicted based on <em><span style="color: black;">Martin&ndash;Hou</span></em><span style="color: black;"> equation of state</span>. The computational study was assured by implementation of theoretical model [1] for one dimensional (1D) and non-linear gas dynamic problems. This model, with the corrections for the boundary layer (<em>BL</em>) displacement thickness, gives a better prediction of the critical flow function than classical approach. Appropriate sonic flow conditions have been executed in the pressurized closed loop system by using <em>ISO 9300</em> critical <em>Venturi</em> <em>nozzle</em>. Measurements of critical mass flow for dense superheated vapour of <em>R-410A</em> and <em>R-507A</em></span><span style="font-size: 10pt;" lang="EN-US"> </span><span style="font-size: 10pt; font-family: &quot;Times New Roman&quot;;" lang="EN-US">carried out on laboratory test stand have confirmed the accuracy of the model and its physical significance. A main result of the investigations is a set of graphs <em>C*</em>(<em>T₀</em>, <em>p₀</em>) and tables<em> </em>for an assumed range of stagnation temperature <em>T₀</em> and pressure <em>p₀</em>at the upstream flow.</span></p>