scholarly journals An Improved Analysis Method for Organic Rankine Cycles Based on Radial-Inflow Turbine Efficiency Prediction

2018 ◽  
Vol 9 (1) ◽  
pp. 49 ◽  
Author(s):  
Peng Li ◽  
Zhonghe Han ◽  
Xiaoqiang Jia ◽  
Zhongkai Mei ◽  
Xu Han ◽  
...  
Keyword(s):  
Heat Source ◽  
Ambient Temperature ◽  
Operating Conditions ◽  
Condensation Temperature ◽  
Analysis Method ◽  
Source Temperature ◽  
Evaporation Temperature ◽  
Turbine Efficiency ◽  
Heat Source Temperature ◽  
Radial Inflow Turbine

The organic Rankine cycle (ORC) has been demonstrated to be an effective method for converting low-grade heat energy into electricity. This paper proposes an improved analysis method for the ORC system. A coupling model of the ORC system with a radial-inflow turbine efficiency prediction model is presented. Multi-objective optimization was conducted for a constant turbine efficiency ORC system (ORCCTE) and a predicted turbine efficiency ORC system (ORCDTE), and the optimization results were compared. Additionally, a sensitivity analysis was conducted with respect to the heat source temperature and the ambient temperature. It can be found that the predicted turbine efficiency decreases with the increasing evaporation temperature, and increases with the increasing condensation temperature. The turbine efficiency is not constant and it varies with operating conditions. The distribution of the Pareto frontier for ORCCTE system and ORCCTE system is different. Compared with the ORCCTE system, the ORCDTE system has a lower optimal evaporation temperature, but a higher optimal condensation temperature. The deviation between the predicted turbine efficiency and the constant turbine efficiency increases with the increasing heat source temperature but decreases with the increasing ambient temperature. Thus, the difference in the theoretical analysis results between ORCCTE system and ORCDTE system increases with the increasing heat source temperature but decreases with the increasing ambient temperature.

Performance of Working Fluids for Power Generation in a Supercritical Organic Rankine Cycle

2012 ◽  
Author(s):  
Rachana Vidhi ◽  
Sarada Kuravi ◽  
Saeb Besarati ◽  
E. K. Stefanakos ◽  
D. Yogi Goswami ◽  
...  
Keyword(s):  
Power Generation ◽  
Heat Source ◽  
Thermal Efficiency ◽  
Thermodynamic Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluids ◽  
Source Temperature ◽  
Heat Source Temperature ◽  
Organic Fluids

This paper reports on the performance of various organic refrigerants and their mixtures as working fluids for power generation in a supercritical Rankine cycle (SRC) from geothermal sources. Organic fluids that have zero or very low ozone depletion potential and are environmentally safe are selected for this study. Geothermal source temperature is varied from 125–200°C, and the cooling water temperature is changed from 10–20°C. The effect of varying operating conditions on the performance of the thermodynamic cycle has been analyzed. Operating pressure of the cycle has been optimized for thermal efficiency for each fluid at each source temperature. The condensation pressure is determined by the cooling condition and is kept fixed for each condensation temperature. Energy and exergy efficiencies of the cycle have been obtained for the pure fluids as a function of heat source temperature. Mixtures of organic fluids have been analyzed and effect of composition on performance of the thermodynamic cycle has been studied. It is observed that thermal efficiency over 20% can be achieved for 200°C heat source temperature and the lowest cooling temperature. When mixtures are considered as working fluids, the thermal efficiency of the cycle is observed to remain between the thermal efficiencies of the constituent fluids.

scholarly journals Nucleation and Condensation of Magnesium Vapor in Argon Carrier

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1441
Author(s):  
Jibiao Han ◽  
Daxue Fu ◽  
Junhua Guo ◽  
Zonghui Ji ◽  
Zhihe Dou ◽  
...  
Keyword(s):  
Heat Source ◽  
Flow Rate ◽  
Vapor Condensation ◽  
Condensation Temperature ◽  
Atomic Collisions ◽  
Condensation Zone ◽  
Source Temperature ◽  
Heat Source Temperature ◽  
Vapor Partial Pressure ◽  
Condensed Product

The nucleation and condensation of Magnesium (Mg) vapor carried by argon gas (Ar) were examined. The condensation of Mg vapor at a heat source temperature of 1273–1473 K and Ar flow rate of 0.1–0.4 m3/h was analyzed. The result indicated that the condensation temperature is affected by the heat source temperature and Ar flow rate, and the condensation temperature of Mg vapor was 1013.3 K at a heat source temperature of 1473 K and Ar flow rate of 0.2 m3/h. The effects of Mg vapor partial pressure and temperature of the condensation zone on the nucleation and condensation of Mg vapor carried by Ar were calculated and analyzed in terms of atomic collisions and critical nucleation radius. Increased vapor oversaturation and decreased condensation temperature were favorable for liquid nucleation growth. The Mg condensation products in Ar flow rate of 0.2 m3/h at a heat source temperature of 1473 K were analyzed by XRD, SEM, and EDS, which indicated that the condensed product was of high purity and not easily oxidized in Ar flow. In this paper, the quality of Mg vapor condensation was controlled, which provided the theoretical and experimental basis for a continuous Mg production process.

scholarly journals Operational Optimisation of a Non-Recuperative 1-kWe Organic Rankine Cycle Engine Prototype

2019 ◽  
Vol 9 (15) ◽  
pp. 3024 ◽  
Author(s):  
Chinedu K. Unamba ◽  
Paul Sapin ◽  
Xiaoya Li ◽  
Jian Song ◽  
Kai Wang ◽  
...  
Keyword(s):  
Steady State ◽  
Heat Source ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Electric Heater ◽  
Part Load ◽  
Source Temperature ◽  
Heat Source Temperature

Several heat-to-power conversion technologies are being proposed as suitable for waste-heat recovery (WHR) applications, including thermoelectric generators, hot-air (e.g., Ericsson or Stirling) engines and vapour-cycle engines such as steam or organic Rankine cycle (ORC) power systems. The latter technology has demonstrated the highest efficiencies at small and intermediate scales and low to medium heat-source temperatures and is considered a suitable option for WHR in relevant applications. However, ORC systems experience variations in performance at part-load or off-design conditions, which need to be predicted accurately by empirical or physics-based models if one is to assess accurately the techno-economic potential of such ORC-WHR solutions. This paper presents results from an experimental investigation of the part-load performance of a 1-kWe ORC engine, operated with R245fa as a working fluid, with the aim of producing high-fidelity steady-state and transient data relating to the operational performance of this system. The experimental apparatus is composed of a rotary-vane pump, brazed-plate evaporator and condenser units and a scroll expander magnetically coupled to a generator with an adjustable resistive load. An electric heater is used to provide a hot oil-stream to the evaporator, supplied at three different temperatures in the current study: 100, 120 and 140 ∘ C. The optimal operating conditions, that is, pump speed and expander load, are determined at various heat-source conditions, thus resulting in a total of 124 steady-state data points used to analyse the part-load performance of the engine. A maximum thermal efficiency of 4.2 ± 0.1% is reported for a heat-source temperature of 120 ∘ C, while a maximum net power output of 508 ± 2 W is obtained for a heat-source temperature at 140 ∘ C. For a 100- ∘ C heat source, a maximum exergy efficiency of 18.7 ± 0.3% is achieved. A detailed exergy analysis allows us to quantify the contribution of each component to the overall exergy destruction. The share of the evaporator, condenser and expander components are all significant for the three heat-source conditions, while the exergy destroyed in the pump is negligible by comparison (below 4%). The data can be used for the development and validation of advanced models capable of steady-state part-load and off-design performance predictions, as well as predictions of the transient/dynamic operation of ORC systems.

scholarly journals Utilisation of bleed steam heat to increase the upper heat source temperature in low-temperature ORC

2011 ◽  
Vol 32 (3) ◽  
pp. 57-70 ◽  
Author(s):  
Dariusz Mikielewicz ◽  
Jarosław Mikielewicz
Keyword(s):  
Power Plant ◽  
Low Temperature ◽  
Heat Source ◽  
Silicone Oil ◽  
Hot Water ◽  
Working Fluid ◽  
Preliminary Heating ◽  
Source Temperature ◽  
Heat Source Temperature ◽  
Steam Heat

Utilisation of bleed steam heat to increase the upper heat source temperature in low-temperature ORC In the paper presented is a novel concept to utilize the heat from the turbine bleed to improve the quality of working fluid vapour in the bottoming organic Rankine cycle (ORC). That is a completely novel solution in the literature, which contributes to the increase of ORC efficiency and the overall efficiency of the combined system of the power plant and ORC plant. Calculations have been accomplished for the case when available is a flow rate of low enthalpy hot water at a temperature of 90 °C, which is used for preliminary heating of the working fluid. That hot water is obtained as a result of conversion of exhaust gases in the power plant to the energy of hot water. Then the working fluid is further heated by the bleed steam to reach 120 °C. Such vapour is subsequently directed to the turbine. In the paper 5 possible working fluids were examined, namely R134a, MM, MDM, toluene and ethanol. Only under conditions of 120 °C/40 °C the silicone oil MM showed the best performance, in all other cases the ethanol proved to be best performing fluid of all. Results are compared with the "stand alone" ORC module showing its superiority.

A Study on the Cooling Characteristics of TMA Clathrate Compound with Additives

2006 ◽  
Vol 326-328 ◽  
pp. 1275-1278 ◽  
Author(s):  
Chang Oh Kim ◽  
Jin Heung Kim ◽  
Nak Kyu Chung
Keyword(s):  
Heat Source ◽  
Phase Change ◽  
Specific Heat ◽  
Freezing Point ◽  
Phase Change Temperature ◽  
Source Temperature ◽  
Heat Source Temperature ◽  
Clathrate Compound ◽  
Supercooling Degree ◽  
Change Temperature

This study aims to find out cooling characteristics of TMA 25wt%-water clathrate compound with ethanol such as supercooling, phase change temperature and specific heat. For this purpose, ethanol is added as per weight concentration and cooling experiment is performed at -6, -7 and -8, cooling heat source temperature, and it leads the following result. (1) Phase change temperature is decreased due to freezing point depression phenomenon. Especially, it is minimized as 5.1 and 5.0, 3.8 according to cooling source temperature in case that 0.5wt% of ethanol is added. (2) If 0.5wt% of ethanol is added, average supercooling degree is 0.9 and minimum supercooling is 0.8, 0.7 according to cooling heat source temperature. The restraint effect of supercooling is shown. (3) Specific heat shows tendency to decrease if ethanol is added. It is 3.013~3.048 kJ/kgK according to cooling heat source temperature if 0.5wt% of ethanol is added. Phase change temperature higher than that of water and inhibitory effect against supercooling can be confirmed through experimental study on cooling characteristics of TMA 25wt%-water clathrate compound by adding additive, ethanol.

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