Optimization of Low-Temperature Exhaust Gas Waste Heat Fueled Organic Rankine Cycle

Low temperature exhaust gases carrying large amount of waste heat are released by steel-making process and many other industries, Organic Rankine Cycles （ORCs） are proven to be the most promising technology to re- cover the low-temperature waste heat, thereby to get more financial benefits for these industries. The exergy analysis of ORC units driven by low-temperature exhaust gas waste heat and charged with dry and isentropic fluid was per- formed, and an intuitive approach with simple impressions was developed to calculate the performances of the ORC unit. Parameter optimization was conducted with turbine inlet temperature simplified as the variable and exergy effi- ciency or power output as the objective function by means of Penalty Function and Golden Section Searching algo- rithm based on the formulation of the optimization problem. The power generated by the optimized ORC unit can be nearly as twice as that generated by a non-optimized ORC unit. In addition, cycle parametric analysis was performed to examine the effects of thermodynamic parameters on the cycle performances such as thermal efficiency and exergy efficiency. It is proven that performance of ORC unit is mainly affected by the thermodynamic property of working fluid, the waste heat temperature, the pinch point temperature of the evaporator, the specific heat capacity of the heat carrier and the turbine inlet temperature under a given environment temperature.

A prospective study to evaluate the efficacy of an intracardiac electrogram-based atrioventricular and interventricular intervals optimization method in cardiac resynchronization therapy

Background Cardiac resynchronization therapy （CRT） with biventricular pacing improves cardiac function,functional capacity and quality of life in selected patients with heart failure.The current study aimed to evaluate the efficacy of the intracardiac electrogram （IEGM）-based optimization method,QuickOptTM,in Chinese patients treated with CRT.Methods Aortic time velocity integrals （AVTI） achieved at the sensed atrioventricular （AV）,paced AV and interventricular （VV） interval settings recommended by both QuickOptTM and standard echocardiographic optimization were measured in 101 patients.Consistency and the strength of the relationship between the two timing cycle optimization methods were assessed by intra-class correlation coefficient （ICC）.Results The ICC showed good agreement and correlation with what the AVTI achieved at the optimal sensed AV （ICC=0.9683 （0.9535-0.9785））,paced AV （ICC=0.9642 （0.9475-0.9757）） and VV （ICC=0.9730 （0.9602-0.9817）） interval settings determined by the two optimization methods.The average time required by echocardiographic optimization and by QuickOptTM were （78.32±32.40） minutes and （1.98±1.64） minutes respectively （P 〈0.0001）.Conclusion The QuickOptTM algorithm provides a quicker,simpler and reliable alternative to the standard method for timing cycle optimization.（ClinicaITrial.gov Reference Number：NCT00918294）