Use of low grade heat sources in combined ejector–double effect absorption refrigeration systems

2012 ◽  
Vol 226 (5) ◽  
pp. 607-622 ◽  
Author(s):  
Leili Garousi Farshi ◽  
SM Seyed Mahmoudi ◽  
Marc A Rosen ◽  
Morteza Yari
Keyword(s):  
Double Effect ◽  
Low Grade ◽  
Heat Sources ◽  
Absorption Refrigeration ◽  
Low Grade Heat

Meanline Analysis and CFD Study of a Radial Inflow Turbine With Vaneless Distributor for Low Temperature Organic Rankine Cycle

2020 ◽  
Author(s):  
M. Deligant ◽  
S. Braccio ◽  
T. Capurso ◽  
F. Fornarelli ◽  
M. Torresi ◽  
...  
Keyword(s):  
Energy Demand ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Low Grade ◽  
Heat Sources ◽  
Turbine Wheel ◽  
Good Efficiency ◽  
Low Grade Heat

Abstract The Organic Rankine Cycle (ORC) allows the conversion of low-grade heat sources into electricity. Although this technology is not new, the increase in energy demand and the need to reduce CO2 emissions create new opportunities to harvest low grade heat sources such as waste heat. Radial turbines have a simple construction, they are robust and they are not very sensitive to geometry inaccuracies. Most of the radial inflow turbines used for ORC application feature a vaned nozzle ensuring the appropriate distribution angle at the rotor inlet. In this work, no nozzle is considered but only the vaneless gap (distributor). This configuration, without any vaned nozzle, is supposed to be more flexible under varying operating conditions with respect to fixed vanes and to maintain a good efficiency at off-design. This paper presents a performance analysis carried out by means of two approaches: a combination of meanline loss models enhanced with real gas fluid properties and 3D CFD computations, taking into account the entire turbomachine including the scroll housing, the vaneless gap, the turbine wheel and the axial discharge pipe. A detailed analysis of the flow field through the turbomachine is carried out, both under design and off design conditions, with a particular focus on the entropy field in order to evaluate the loss distribution between the scroll housing, the vaneless gap and the turbine wheel.

scholarly journals Comparative Thermodynamic Analysis of Kalina and Kalina Flash Cycles for Utilizing Low-Grade Heat Sources

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3311 ◽  
Author(s):  
Kyoung Kim ◽  
Chul Han ◽  
Hyung Ko
Keyword(s):  
Mass Fraction ◽  
Power Production ◽  
Low Grade ◽  
Heat Sources ◽  
Kalina Cycle ◽  
Thermodynamic Performance ◽  
Locally Maximal ◽  
The Difference ◽  
Proposed Modification ◽  
Low Grade Heat

The Kalina flash cycle (KFC) is a novel, recently proposed modification of the Kalina cycle (KC) equipped with a flash vessel. This study performs a comparative analysis of the thermodynamic performance of KC and KFC utilizing low-grade heat sources. How separator pressure, flash pressure, and ammonia mass fraction affect the system performance is systematically and parametrically investigated. Dependences of net power and cycle efficiencies on these parameters as well as the mass flow rate, heat transfer rate and power production at the cycle components are analyzed. For a given set of separator pressure and ammonia mass fraction, there exists an optimum flash pressure making exergy efficiency locally maximal. For these pressures, which are higher for higher separator pressure and lower ammonia mass fraction, KFC shows better performance than KC both in net power and cycle efficiencies. At higher ammonia mass fraction, however, the difference is smaller. While the maximum power production increases with separator pressure, the dependence is quite weak for the maximum values of both efficiencies.

scholarly journals Cool Steam Method for Desalinating Seawater

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2385
Author(s):  
Pedro Arnau ◽  
Naeria Navarro ◽  
Javier Soraluce ◽  
Jose Martínez-Iglesias ◽  
Jorge Illas ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Heat Source ◽  
Latent Heat ◽  
Heat Sink ◽  
Low Grade ◽  
Heat Sources ◽  
Working Pressure ◽  
Multi Stage ◽  
Heat Of Evaporation ◽  
Low Grade Heat

Cool steam is an innovative distillation technology based on low-temperature thermal distillation (LTTD), which allows obtaining fresh water from non-safe water sources with substantially low energy consumption. LTTD consists of distilling at low temperatures by lowering the working pressure and making the most of low-grade heat sources (either natural or artificial) to evaporate water and then condensate it at a cooler heat sink. To perform the process, an external heat source is needed that provides the latent heat of evaporation and a temperature gradient to maintain the distillation cycle. Depending on the available temperature gradient, several stages can be implemented, leading to a multi-stage device. The cool steam device can thus be single or multi-stage, being raw water fed to every stage from the top and evaporated in contact with the warmer surface within the said stage. Acting as a heat carrier, the water vapor travels to the cooler surface and condensates in contact with it. The latent heat of condensation is then conducted through the conductive wall to the next stage. Net heat flux is then established from the heat source until the heat sink, allowing distilling water inside every parallel stage.

scholarly journals Exergy Analysis of Kalina and Kalina Flash Cycles Driven by Renewable Energy

2020 ◽  
Vol 10 (5) ◽  
pp. 1813
Author(s):  
Kyoung Hoon Kim ◽  
Hyung Jong Ko ◽  
Chul Ho Han
Keyword(s):  
Exergy Analysis ◽  
Power Production ◽  
Ammonia Concentration ◽  
Exergy Efficiency ◽  
Low Grade ◽  
Heat Sources ◽  
Exergy Destruction ◽  
Kalina Cycle ◽  
Low Grade Heat ◽  
Exergy Performance

The Kalina cycle (KC) has been recognized as one of the most efficient conversion systems of low-grade heat sources. The Kalina flash cycle (KFC) is a recently proposed novel cycle which is equipped with an additional flash process to the KC. In this study, the exergy performance of KC and KFC driven by a low-grade heat source are investigated comparatively. The dependence of the exergy destruction at each component as well as the system’s exergy efficiency on ammonia concentration, separator pressure and, additionally, flash pressure for KFC, are systematically investigated. Results showed that KFC can be optimized with respect to flash pressure on the base of exergy efficiency, and the component where largest exergy destruction occurs varies for different separator pressure and ammonia fraction in both systems. It is also shown that the maxima of net power production and exergy efficiency in KFC with optimal flash pressure are superior to those in KC.

Optimization of Organic Rankine Cycles Using Dry Fluids

2006 ◽  
Author(s):  
P. J. Mago ◽  
L. M. Chamra ◽  
C. Somayaji
Keyword(s):  
Waste Heat ◽  
Operating Parameters ◽  
Low Grade ◽  
Heat Sources ◽  
Second Law Analysis ◽  
Waste Energy ◽  
Organic Rankine Cycles ◽  
Low Grade Heat ◽  
Organic Fluids ◽  
System Operating

This paper presents an optimization of Organic Rankine Cycles "ORC" using dry organic fluids, to convert waste energy to power from low grade heat sources. The dry organic working fluids under investigation are R113, R245ca, R123, and Isobutene. Different configurations such as reheat ORC and regenerative ORC will be analyzed and compared with the basic ORC in order to determine the configuration that presents the best performance. The optimization for the different configurations will be performed using a combined first and second law analysis by varying some system operating parameters at various reference temperatures and pressures. Some of the results show that regenerative ORC produces higher efficiency compared with the basic ORC while also reducing the amount of waste heat needed to produce the same power with a less irreversibility.

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