Effects of spontaneous condensation in steam-driven screw expanders

10th International Conference on Compressors and their Systems

Grieb, Manuel^1 ; Brümmer, Andreas^1

TU Dortmund University, Department of Fluidics, Leonhard-Euler-Str. 5, Dortmund

44227, Germany^1

关键词: Classical nucleation theory;    Equation of state;    Expansion phase;    Metastable region;    Positive displacement;    Spontaneous condensation;    Steam condensation;    Thermodynamic simulations;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/232/1/012078/pdf
DOI  :  10.1088/1757-899X/232/1/012078

来源: IOP

【 摘 要 】

Condensation and its effects on turbo machinery operation are well understood and have been widely investigated. However, only little scientific work on condensation in positive displacement machines has been published. Although, depending on machine type, high expansion rates and, as a consequence, significant supersaturation can be achieved for working fluids with a negative saturation vapour curve. In this paper the effects of spontaneous steam condensation in screw expanders are discussed. Classical nucleation theory is used for the thermodynamic simulation of operational behaviour. The study shows at which point during the expansion phase spontaneous condensation can be expected, and typical nucleation rates are determined. Since the calculation of condensation requires a suitable fluid model providing consistent data for the metastable region, the advantages of Pollak's equation of state over the IAPWS property formulation are demonstrated. The impact of released latent heat during expansion on chamber states is depicted. Furthermore, a comparison of purely metastable expansion with equilibrium expansion is provided in order to show the full range discrepancies.