Preliminary conceptual design and thermodynamic comparative study on vapor absorption refrigeration cycles integrated with a supercritical CO2 power cycle

2018 ◽  
Vol 161 ◽  
pp. 162-171 ◽  
Author(s):  
Hang Li ◽  
Wei Su ◽  
Liyan Cao ◽  
Feng Chang ◽  
Wenkai Xia ◽  
...  
Keyword(s):  
Comparative Study ◽  
Conceptual Design ◽  
Supercritical Co2 ◽  
Absorption Refrigeration ◽  
Power Cycle ◽  
Vapor Absorption ◽  
Vapor Absorption Refrigeration

Second Law Analysis of a Novel Combined Cooling and Power Cycle With Water Harvesting

2005 ◽  
Author(s):  
J. R. Khan ◽  
W. E. Lear ◽  
S. A. Sherif ◽  
John F. Crittenden
Keyword(s):  
High Pressure ◽  
Absorption Refrigeration ◽  
Refrigeration System ◽  
Ambient Conditions ◽  
Power Cycle ◽  
High Pressure Compressor ◽  
Vapor Absorption ◽  
Absorption Refrigeration System ◽  
Vapor Absorption Refrigeration ◽  
Pressure Compressor

The first and second laws of thermodynamics were used to analyze a novel cooling and power cycle that combines a semi-closed cycle called the High Pressure Regenerative Turbine Engine (HPRTE) with a vapor absorption refrigeration system (VARS). Waste heat from the recirculated combustion gas of the HPRTE is used to power the absorption refrigeration unit, which cools the high-pressure compressor inlet of the HPRTE to below ambient conditions and also produces excess refrigeration in an amount that depends on ambient conditions. The cycle is modeled using steady-state thermodynamics, with state-of-the-art polytropic efficiencies and pressure drops for the turbo-machinery and heat exchangers, and accurate correlations for the properties of the NH3-water mixture and the combustion products. Exergy analyses were performed for all the components of the cycle to examine the losses and identify critical plant devices considering different operating conditions. Water produced as a product of combustion is intentionally condensed in the evaporator of the VARS, which is designed to provide sufficient cooling for: the inlet air to the high pressure compressor, water extraction and for an external load. The cycle is shown to operate with a thermal efficiency approaching 46% for a turbine inlet temperature of 1400°C while producing about 1.5 kg of water for each kg of fuel (propane) consumed. The thermal efficiency does not take into account the cooling effect produced in the evaporator of VARS. The combined cycle efficiency at the above operating condition was found to be 49%. Low emissions are also possible on liquid fuels and not just on natural gas. It should be noted that the values of efficiencies obtained are for a medium sized engine with conservative values of the design parameters. It is observed that the largest contribution to the total cycle irreversibility comes from the combustor and accounts for 85% of the total exergy loss. The generator of the vapor absorption refrigeration system is the next largest quantity, accounting for about 3.4% of the total exergy loss. The mass of water extracted from the system increases as the value of the low-pressure compressor ratio is increased. However, this rate of increase is more when the compressor ratio is increased from 1.0 to 2.0 and less as the compressor ratio is further increased. Based on these and prior results, which showed that the HPRTE is very compact and has inherently low emissions, it appears that this cycle would be ideally suited for distributed power and vehicle applications, especially ones with associated air conditioning loads.

Testing and Modeling of a Semi-Closed Gas Turbine Cycle Integrated With a Vapor Absorption Refrigeration System

2006 ◽  
Author(s):  
J. R. Khan ◽  
W. E. Lear ◽  
S. A. Sherif ◽  
E. B. Howell ◽  
J. F. Crittenden ◽  
...  
Keyword(s):  
High Pressure ◽  
Combined Cycle ◽  
Absorption Refrigeration ◽  
Ambient Conditions ◽  
Power Cycle ◽  
High Pressure Compressor ◽  
Refrigeration Unit ◽  
Vapor Absorption ◽  
Absorption Refrigeration System ◽  
Vapor Absorption Refrigeration

A novel cooling and power cycle has been proposed that combines a semi-closed cycle gas turbine called the High Pressure Regenerative Turbine Engine (HPRTE) with a vapor absorption refrigeration system (VARS). The refrigeration cycle (VARS) interacts with the power cycle (HPRTE) solely through heat transfer in the generator and the evaporator. Waste heat from the recirculated combustion gas of the HPRTE is used to power the absorption refrigeration unit, which cools the high-pressure compressor inlet of the HPRTE to below ambient conditions and also produces excess refrigeration, in an amount which depends on ambient conditions. Water produced as a product of combustion is intentionally condensed in the evaporator of the VARS, which is designed to provide sufficient cooling for three purposes: chilling the inlet air to the high pressure compressor, water extraction, and for an external cooling load. In a previous study, the combined cycle was modeled using zero-dimensional steady-state thermodynamics, with the specified values of efficiencies and pressure drops for the turbo-machinery and heat exchangers. The model predicts that the combined cycle with steam blade cooling for a medium-sized engine will have a thermal efficiency of 49%, in addition to the external refrigeration load generated in the cycle which is 13% of the net work output. It also produces about 1.4 kg of water for each kg of fuel (propane) consumed. A small experimental unit demonstrating the HPRTE/VARS combined cycle has been constructed and is currently being tested in the Energy & Gas-dynamic Systems Laboratory at the University of Florida. A 45 HP Rover 1S-60 engine is integrated with a NH3/H2O vapor absorption refrigeration unit having a capacity of 19 Ton Refrigeration. The engine flow-path has been significantly modified to include partial recirculation of exhaust products, turbocharging, and recuperation, thus implementing the HPRTE concept. In addition, a significant modeling effort has been undertaken to simulate the combined cycle operation under design and off-design conditions. Initial experimental results show good agreement with the model predictions, including overall efficiency and water extraction rates.

EXERGY ANALYSIS OF A LiBr–H2O VAPOR ABSORPTION REFRIGERATION PLANT: A CASE STUDY

2014 ◽  
Vol 22 (02) ◽  
pp. 1450010 ◽  
Author(s):  
SANJEEV ANAND ◽  
ANKUSH GUPTA ◽  
SUDHIR KUMAR TYAGI
Keyword(s):  
Performance Optimization ◽  
Exergy Analysis ◽  
Heat Rate ◽  
Exergy Efficiency ◽  
Exergy Loss ◽  
Absorption Refrigeration ◽  
Actual System ◽  
Evaporator Temperature ◽  
Vapor Absorption ◽  
Vapor Absorption Refrigeration

This communication presents the energy and exergy analysis of an actual double effect steam powered LiBr – H 2 O vapor absorption refrigeration plant. Exergy loss, COP, exergy efficiency and heat rate for each component of the system are calculated. The effect of generator as well as evaporator temperature on the COP and exergy efficiency is evaluated and it is found that the irreversibility rate is highest in the generator while it is found to be the lowest in the case of absorber and condenser. It is also found that the COP of the system increases with the increase in the evaporator temperature while it is found to be reverse in case of exergy efficiency. Results revealed that average exergy loss is highest in the generator as compared to other components. The results obtained are helpful for designers to bring changes in the actual system for performance optimization and less wastage of energy. The study clearly explain the operational and maintenance problems in the machine and point out the areas of energy wastage which the operational engineer should look into for the optimum operation of the plant.

Space Cooling Using the Concept of Nanofluids-Based Direct Absorption Solar Collectors

2012 ◽  
Author(s):  
Vivek Vishwakarma ◽  
Nitin Singhal ◽  
Vikrant Khullar ◽  
Himanshu Tyagi ◽  
Robert A. Taylor ◽  
...  
Keyword(s):  
Solar Collector ◽  
Air Conditioning ◽  
Thermal Storage ◽  
Temperate Climate ◽  
Absorption Refrigeration ◽  
Direct Absorption ◽  
Parabolic Trough ◽  
Space Cooling ◽  
Vapor Absorption ◽  
Vapor Absorption Refrigeration

A solar-energy based vapor absorption refrigeration system is potentially an excellent alternative air-conditioning system. However, there are several research challenges to ensure sufficient efficiency and reliability for ensuring widespread implementation. Integration of a parabolic trough solar collector utilizing a mixture of nanoparticles and water with a vapor absorption system has the potential to significantly enhance the efficiency of the system. Such a system makes use of the superior thermo-physical properties of the nanofluid compared to the base fluid. Moreover, the direct absorption phenomenon of solar radiation through interaction with the participating medium (nanofluid) results in a higher temperature rise of the medium in conjunction with higher operating efficiencies as well. At the same time there are certain challenges that need to be identified and addressed in the implementation of this novel concept. For instance, to make it reliable, the system further needs to be integrated with a thermal storage system which facilitates air-conditioning even during non-sunshine hours. Integration of vapor absorption refrigeration technology, parabolic trough with water-nanoparticles mixture as the absorbing medium and a thermal storage facility is the uniqueness of this design which under certain conditions and locations may prove to be an efficient and reliable substitute to the conventional electrical air-conditioning systems. In this particular study a space cooling application for approximately 100 Tons of refrigeration is studied. Hourly variation in sunlight as well as seasonal changes for temperate climate conditions is considered. Parameters such as the cooling load of the space, and waste heat produced by electronics are evaluated. The cooling system driven by the nanofluid-based concentrated parabolic solar collector is mathematical modeled and then the optimization is done by varying the nanoparticle size and volume fraction in order to obtain the best result for collector outlet temperature, thermal efficiency and optical efficiency.

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