Optimal Design of ORC Systems with a Low-Temperature Heat Source

A numerical model of subcritical and trans-critical power cycles using a fixed-flowrate low-temperature heat source has been validated and used to calculate the combinations of the maximum cycle pressure (Pev) and the difference between the source temperature and the maximum working fluid temperature (DT) which maximize the thermal efficiency (ηth) or minimize the non-dimensional exergy losses (β), the total thermal conductance of the heat exchangers (UAt) and the turbine size (SP). Optimum combinations of Pev and DT were calculated for each one of these four objective functions for two working fluids (R134a, R141b), three source temperatures and three values of the non-dimensional power output. The ratio of UAt over the net power output (which is a first approximation of the initial cost per kW) shows that R141b is the better working fluid for the conditions under study.

[1]  Mohammed Khennich,et al.  Thermodynamic analysis and optimization of power cycles using a finite low‐temperature heat source , 2012 .

[2]  Vincent Lemort,et al.  Technological and Economical Survey of Organic Rankine Cycle Systems , 2009 .

[3]  N. Galanis,et al.  Analysis of a carbon dioxide transcritical power cycle using a low temperature source , 2009 .

[4]  I. Obernberger,et al.  Description and evaluation of the new 1,000 kWel organic rankine cycle process integrated in the biomass CHP plant in Lienz, Austria , 2002 .

[5]  Yu-Chun Hou,et al.  Development of an equation of state for gases , 1955 .

[6]  Ronald DiPippo,et al.  Second Law assessment of binary plants generating power from low-temperature geothermal fluids , 2004 .

[7]  Ennio Macchi,et al.  Efficiency Prediction for Axial-Flow Turbines Operating with Nonconventional Fluids , 1981 .

[8]  Olav Bolland,et al.  Working fluids for low-temperature heat source , 2010 .

[9]  Tao Guo,et al.  Fluids and parameters optimization for a novel cogeneration system driven by low-temperature geother , 2011 .

[10]  W. Worek,et al.  Optimum design criteria for an Organic Rankine cycle using low-temperature geothermal heat sources , 2007 .

[11]  Andreas Schuster,et al.  Efficiency optimization potential in supercritical Organic Rankine Cycles , 2010 .

[12]  Nicolas Galanis,et al.  Parametric study and optimization of a transcritical power cycle using a low temperature source , 2010 .

[13]  Minggao Ouyang,et al.  Study of working fluid selection of organic Rankine cycle (ORC) for engine waste heat recovery , 2011 .

[14]  E. Stefanakos,et al.  A REVIEW OF THERMODYNAMIC CYCLES AND WORKING FLUIDS FOR THE CONVERSION OF LOW-GRADE HEAT , 2010 .

[15]  Jinliang Xu,et al.  The optimal evaporation temperature and working fluids for subcritical organic Rankine cycle , 2012 .

[16]  Chi-Chuan Wang,et al.  Effect of working fluids on organic Rankine cycle for waste heat recovery , 2004 .

[17]  N. Lai,et al.  Working fluids for high-temperature organic Rankine cycles , 2007 .

[18]  H. Baehr,et al.  An International Standard Formulation for the Thermodynamic Properties of 1,1,1,2‐Tetrafluoroethane (HFC‐134a) for Temperatures from 170 K to 455 K and Pressures up to 70 MPa , 1994 .