scholarly journals Energetic and Exergetic Investigations of Hybrid Configurations in an Absorption Refrigeration Chiller by Aspen Plus

Processes ◽  
2019 ◽  
Vol 7 (9) ◽  
pp. 609 ◽  
Author(s):  
Xiao Zhang ◽  
Liang Cai ◽  
Tao Chen
Keyword(s):  
Heat Transfer ◽  
Waste Heat ◽  
Aspen Plus ◽  
Coefficient Of Performance ◽  
Heat Sources ◽  
Exergy Destruction ◽  
Absorption Refrigeration ◽  
Exergetic Efficiency ◽  
Complex Heat Transfer ◽  
Steady State Simulation

In the present study, a steady-state simulation model was built and validated by Aspen Plus to assess the performance of an absorption refrigeration chiller according to the open literature. Given the complex heat transfer happening in the absorbers and the generator, several assumptions were proposed to simplify the model, for which a new parameter ε l i q was introduced to describe the ratio of possible heat that could be recovered from the absorption and heat-transferring process in the solution cooling absorber. The energetic and the exergetic investigations of a basic cycle and hybrid cycles were conducted, in which the following parameters were analyzed: coefficient of performance (COP), exergetic efficiency, exergy destruction, and irreversibility. According to the results, the basic cycle exhibited major irreversibility in the absorbers and the generator. Subsequently, two proposed novel configurations were adopted to enhance its performance; the first (configuration 1) involved a compressor between a solution heat exchanger and a solution cooling absorber, and the second (configuration 2) involved a compressor between a rectifier and a condenser. The peak COP and the overall exergetic efficiency (η) of configuration 1 were found to be better, increasing by 15% and 5.5%, respectively, and those of configuration 2 were also upregulated by 5% and 4%, respectively. The rise in intermediate compressor ratio not only reduced the driving generator temperature of both configurations but also expanded the operating range of the system under configuration 1, thus proving their feasibility in waste heat sources and the superiority of configuration 1. Detailed information about the optimal state for hybrid cycles is also presented.

scholarly journals Numerical Simulation and Optimization of Waste Heat Recovery in a Sinter Vertical Tank

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 385 ◽  
Author(s):  
Chenyi Xu ◽  
Zhichun Liu ◽  
Shicheng Wang ◽  
Wei Liu
Keyword(s):  
Heat Transfer ◽  
Power Consumption ◽  
Flow Rate ◽  
Heat Dissipation ◽  
Waste Heat ◽  
Air Flow ◽  
Particle Diameter ◽  
Exergy Destruction ◽  
Air Flow Rate ◽  
Simulation And Optimization

In this paper, a two-dimensional steady model is established to investigate the gas-solid heat transfer in a sinter vertical tank based on the porous media theory and the local thermal non-equilibrium model. The influences of the air flow rate, sinter flow rate, and sinter particle diameter on the gas-solid heat transfer process are investigated numerically. In addition, exergy destruction minimization is used as a new principle for heat transfer enhancement. Furthermore, a multi-objective genetic algorithm based on a Back Propagation (BP) neural network is applied to obtain a combination of each parameter for a more comprehensive performance, with the exergy destruction caused by heat transfer and the one caused by fluid flow as the two objectives. The results show that the heat dissipation and power consumption both gradually increase with an increase of the air mass flow rate. Additionally, the increase of the sinter flow rate results in a decrease of the heat dissipation and an increase of the power consumption. In addition, both heat dissipation and power consumption gradually decrease with an increase of the sinter particle diameter. For the given structure of the vertical tank, the optimal operating parameters are 2.99 kg/s, 0.61 kg/s, and 32.8 mm for the air flow rate, sinter flow rate, and sinter diameter, respectively.

Subfreezing Absorption Refrigeration for Industrial CHP

2018 ◽  
Vol 26 (04) ◽  
pp. 1850033
Author(s):  
Gopalakrishnan Anand ◽  
Donald C. Erickson ◽  
Ellen Makar
Keyword(s):  
Cooling Tower ◽  
Waste Heat ◽  
Careful Consideration ◽  
Integrated System ◽  
Added Value ◽  
Coefficient Of Performance ◽  
Processing Plant ◽  
Absorption Refrigeration ◽  
Exhaust Heat ◽  
Chp System

The design and operation of an advanced absorption refrigeration unit (Thermochiller) as part of an industrial combined heat and power (CHP) system is presented. The unit is installed at a vegetable processing plant in Santa Maria, California. The overall integrated system includes the engine package with waste heat recovery, Thermochiller, cooling tower, and chilling load interface. The unique feature of the system is that both the exhaust and jacket heat are used to supply subfreezing refrigeration. To achieve the low refrigeration temperatures of interest to industrial applications, all components of this integrated system needed careful consideration and optimization. The CHP system has a low emission natural gas-fired 633[Formula: see text]kW reciprocating engine cogeneration package. Both the exhaust heat and jacket heat are recovered and delivered via a hot glycol loop with 105[Formula: see text]C supply temperature and 80[Formula: see text]C return. The 125 ton ammonia absorption chiller (TC125) chills propylene glycol to [Formula: see text]C and has a coefficient of performance of 0.63. TC125 has peak electric demand of 10[Formula: see text]kW for pumps and 8[Formula: see text]kW for the cooling tower fan. The CHP system, including TC125, operates 20[Formula: see text]h per day, six days per week. All operations of TC125 are completely automatic and autonomous, including startups and shutdowns. Industrial refrigeration is typically a 24/7 load and highly energy-intensive. By converting all the engine waste heat to subfreezing refrigeration, Thermochiller brings added value to cogeneration or CHP projects.

Modelling and performance analysis of a single stage open absorption heat pump system in aspen plus using aqueous LiBr and HCOOK: A waste moist heat recovery application

2021 ◽  
pp. 095765092110478
Author(s):  
Muhammad Kashif Shahzad ◽  
Yaqi Ding ◽  
Yongmei Xuan ◽  
Neng Gao ◽  
Guangming Chen
Keyword(s):  
Heat Pump ◽  
Heat Recovery ◽  
Process Model ◽  
Waste Heat ◽  
Lithium Bromide ◽  
Aspen Plus ◽  
Coefficient Of Performance ◽  
Water Recovery ◽  
Pump System ◽  
Absorption Heat Pump

Open absorption heat pump (OAHP) system is more viable option to recover waste heat from moist gas as compared to the traditional condensation methods. This promising technology has great potential for latent heat recovery from moist gas, drying process in paper and other industrial heating applications. This study presents the process modelling and comparative analysis of OAHP system in Aspen Plus using two different solutions by adopting part regeneration technique. The promising potassium formate-water (HCOOK/H2O) which has lower causticity, lower costs and better crystallization characteristics is used as an alternative to the caustic lithium bromide-water (LiBr/H2O) solution in this study. Process model of the system is established in Aspen Plus and, the properties validity is confirmed with published experimental and Engineering Equation Solver (EES) library data. A detailed comparative parametric study is carried out to evaluate the effect of influencing parameters on coefficient of performance (COP), water recovery (φ) and heat recovery (ζ) efficiencies. The performance of OAHP system is found to be very similar using different concentrations as 2.13 COP value for 50% LiBr/H2O and 2.19 for 70% HCOOK/H2O solution over design conditions. Similarly, φ is found to be 0.701, 0.688 while ζ as 0.716 and 0.705 for both the absorbents. Moreover, the system’s operational concentration range is 45-61.3% for LiBr/H2O and 55-82.1% for HCOOK/H2O at 135 °C regeneration heat input. Potassium formate solution having quite similar properties to the aqueous lithium bromide is also confirmed to have similar performance trends using 50% and 70% concentrations.

Waste-Heat Driven Miniature Absorption Refrigeration System Using Ionic-Liquid as a Working Fluid

2011 ◽  
Author(s):  
Yoon Jo Kim ◽  
Sarah Kim ◽  
Yogendra K. Joshi ◽  
Andrei G. Fedorov ◽  
Paul A. Kohl
Keyword(s):  
Ionic Liquid ◽  
Waste Heat ◽  
Coefficient Of Performance ◽  
System Level ◽  
Working Fluid ◽  
Operating Efficiency ◽  
Outlet Temperature ◽  
Absorption Refrigeration ◽  
Refrigeration System ◽  
Absorption Refrigeration System

An ionic-liquid (IL) is a salt in a liquid state usually with an organic cation and inorganic anion. ILs provide an alternative to the normally toxic working fluids in absorption systems, such as the ammonia/water system. They also eliminate the problems of poor temperature match, crystallization and metal-compatibility problems of the water/LiBr system. In the present study, an IL is explored the working fluid of a miniature absorption refrigeration system so as to utilize waste-heat within the system for low-cost, high-power electronics cooling. To determine performance benchmarks for the refrigerant/IL (e.g. [bmim][PF6]) pairs, system-level simulations have been carried out. An NRTL model was built and used to predict the solubility of the mixture as well as the mixture properties such as enthalpy and entropy. The properties of the refrigerants were determined using REFPROP 6.0. Saturation temperatures at the evaporator and condenser were 25°C and 50°C, respectively. Chip power was fixed at 100 W with the operating temperature set at 85°C. R32 gave the highest operating efficiency with the maximum coefficient of performance (COP) of ca. 0.55 while R134a and R152a showed comparable performance with the maximum COP of ca. 0.4 at the desorber outlet temperature of 80°C. When waste-heat is available for the system operation, R134a and R152a COPs were comparable or better than that of R32.

scholarly journals Experimental analysis of triple fluid vapour absorption refrigeration system driven by electrical energy and engine waste heat

2019 ◽  
Vol 23 (5 Part B) ◽  
pp. 2995-3001 ◽  
Author(s):  
Andi Balasubramanian ◽  
Venkatesan Jayaraman ◽  
Suresh Sivan ◽  
Mariappan Vairavan
Keyword(s):  
Thermal Energy ◽  
Waste Heat ◽  
Electrical Energy ◽  
Coefficient Of Performance ◽  
Test Time ◽  
Absorption Refrigeration ◽  
Engine Exhaust ◽  
Power Sources ◽  
Refrigeration Unit ◽  
Absorption Refrigeration System

In this study, performance analysis of absorption refrigeration cycle has been carried out under variable power sources namely electrical and thermal energy sources. The triple fluid vapour absorption system was used in this work. The temperatures at each point in the cycle such as generator, absorber, evaporator and condenser have been measured. The coefficient of performance of the system was calculated and then compared. The results showed that when the cycle driven by electricity, the coefficient of performance varied from 0.28-1.6 along the test time and the generator temperature changed from 66?C to 106?C. When thermal energy used to generate power, the coefficient of performance varied between 0.16 and 0.6 under the generator temperature of 98?C and 150?C. It was observed that the waste heat energy from engine exhaust can be used efficiently and can replace the conventional power source to drive the absorption refrigeration unit.

Improved Exergy Evaluation of Ammonia-Water Absorption Refrigeration System Using Inverse Method

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Adityabir Singh ◽  
Ranjan Das
Keyword(s):  
Cooling Water ◽  
Coefficient Of Performance ◽  
Exergy Destruction ◽  
Absorption Refrigeration ◽  
Dragonfly Algorithm ◽  
Destruction Rate ◽  
Wide Range ◽  
Mass Flowrate ◽  
Operating Temperatures ◽  
Absorption Refrigeration System

Abstract In this study, the compatibility of exergy destruction minimization (EDM) as the main objective is checked by plotting coefficient of performance (COP), exergy coefficient of performance (ECOP), and overall exergy destruction rate by simultaneously varying input operating temperatures for a 28 TR cooling load absorption system. The component-wise variation in exergy destruction is also considered and it is found that the maxima of COP and ECOP, and the minima of overall exergy destruction lies on a common point, and when the variation of operating temperatures is further extended, the exergy destruction in one of the component becomes negative, which marks the upper bound of the present analysis. At highest valid generator temperature (155 °C), the minimum possible overall exergy destruction rate is 53.50 kW and maximum COP is 0.523. Through inverse optimization (IO) using dragonfly algorithm (DA), the same overall exergy destruction rate is achieved for a wide range of generator temperatures much below than 155 °C, and as low as 127.34 °C. The above variation is explained in terms of flow ratio, mass flowrate of steam, and mass flowrate of cooling water.

Energy and exergy analyses of LiBr/H2O absorption cooling system having recto-trapezoidal profile absorber plate

2020 ◽  
pp. 095440622095969
Author(s):  
Rahul Roy ◽  
Balaram Kundu
Keyword(s):  
Solar Collector ◽  
Cooling System ◽  
Coefficient Of Performance ◽  
Inlet Temperature ◽  
Absorption Refrigeration ◽  
Exergetic Efficiency ◽  
Absorber Plate ◽  
Energy And Exergy ◽  
Trapezoidal Profile ◽  
Exergy Analyses

This paper develops a theoretical model for energy and exergy analyses of a solar-powered Lithium-water absorption refrigeration system using a recto-trapezoidal flat plate solar collector. The effect of collector fluid inlet temperature is to examine the overall performance of the solar collector and the vapour absorption system for a wide range of design variables. The parameters computed are energy and exergy efficiencies of the solar collector plate, coefficient of performance, cooling efficiency, exergy destruction rates, thermal exergy loss rates, irreversibility, and exergetic efficiency of the absorption refrigeration cycle. The simulation results indicate that there exists an optimum inlet temperature of collector fluid for the maximum system coefficient of performance and exergetic efficiency. When the cooling system runs at this temperature, the absorber plate volume attains a minimum value. Furthermore, the performance results are significantly better when a higher absorber plate thickness parameter is for the recto-trapezoidal profile. Finally, a comparative study analyzes the collector performance parameters of an absorber plate having rectangular, triangular, or trapezoidal profile by selecting their respective parameters of geometries. When an additional constraint imposes on the plate volume, it found that using a recto-trapezoidal profile instead of a rectangular profile saves at least 30% or more collector material, and also it may have better performance than a triangular or trapezoidal profile.

Exergy analysis: Parametric study on lithium bromide—water absorption refrigeration systems

2007 ◽  
Vol 221 (11) ◽  
pp. 1345-1351 ◽  
Author(s):  
K Sedighi ◽  
M Farhadi ◽  
M Liaghi
Keyword(s):  
Exergy Analysis ◽  
Water Solution ◽  
Lithium Bromide ◽  
Cooling Water ◽  
Coefficient Of Performance ◽  
Absorption Refrigeration ◽  
Exergetic Efficiency ◽  
Evaporator Temperature ◽  
Cooling Water Temperature ◽  
Single Effect

In the current study, an exergy analysis of a single-effect absorption refrigeration cycle using lithium bromide-water solution is carried out. The cycle has been analysed by considering the mass and energy conservation based on the first and second laws of thermodynamics. This analysis provides a detailed information on the effect of different parameters on the system performance. The coefficient of performance (COP), exergetic efficiency (ECOP), and exergy destruction are determined. The results show that a reduction in cooling water temperature caused an improvement in the COP and ECOP. Increasing the evaporator temperature has also improved the COP, but it caused a reduction in the ECOP of the system. Also it can be seen that the parameters' variation at the solution side has a more significant effect on cycle performances.

Investigation on the Optimum Performance of an Irreversible Solar Powered Absorption Refrigeration System

2011 ◽  
Author(s):  
Fang Wei ◽  
Houcheng Zhang ◽  
Lanmei Wu ◽  
Guoxing Lin
Keyword(s):  
Heat Transfer ◽  
Heat Loss ◽  
Solar Collector ◽  
Optimal Parameter ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Absorption Refrigeration ◽  
Refrigeration System ◽  
Absorption Refrigeration System ◽  
Solar Powered

An irreversible solar powered absorption refrigeration system is put forward, in which finite-rate heat transfer with the convection mode from the solar collector to the absorption refrigerator and the radiation-convection heat loss from the solar collector to the ambient, the internal irreversibility inside the working fluid are taken into account. On the basis of thermodynamic analysis and log mean temperature difference (LMTD) methods, the expression between the overall coefficient of performance (COP) of the solar powered absorption refrigeration system and the operating temperature of the solar collector is derived. The influences of heat loss of the solar collector, the irreversibility inside the working fluid, the isobaric temperature ratio, the ratio of heat-transfer coefficients on the optimal performance characteristic of the solar powered absorption refrigeration system are revealed. The results obtained in the present paper are helpful to the optimal parameter design of actual solar powered absorption refrigerators.

Exergy Analysis of a Solar-Driven Dual Parallel-Connected Ejector Refrigeration System

2016 ◽  
Vol 839 ◽  
pp. 100-106
Author(s):  
Yahya Gaafar Abdella Mohammed ◽  
Tawat Suriwong ◽  
Sakda Somkun ◽  
Timeyo Mkamanga Maroyi
Keyword(s):  
Solar Collector ◽  
Exergy Analysis ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Saturated Steam ◽  
Working Fluid ◽  
Electric Heater ◽  
Exergy Destruction ◽  
Refrigeration System ◽  
Exergetic Efficiency

Nowadays, developing solar cooling technologies, especially ejector refrigeration system, has become preferable to scientific researchers. Exergy analysis is a technique in which the basis of evaluation of thermodynamic losses follows the second law rather than the first law of thermodynamics. An experimental exergy analysis of a solar-driven dual parallel-connected ejector (DPE) refrigeration system was conducted using water as working fluid. Saturated steam with 2 bar and 120oC was provided by heat–pipe evacuated tube solar collector with an assistant of an electric heater. The saturated stream was used as a motive flow for the ejectors. The exergy destruction and exergetic efficiency of the main components of the DPE refrigeration system were determined and compared with those when using a single ejector (SE) under same operating conditions. It was found that the most irreversibilities of both systems occurred at the solar collector, electric boiler and ejectors, respectively. Also, the total irreversibility (Exergy destruction) of the system when using DPE was lower than using a SE. In additions, the exergetic efficiency of the ejector, evaporator, and overall system when using DPE were increased by 21%, 10%, and 27%, respectively. The system thermal ratio (STR) and coefficient of performance (COP) of the system using DPE compared with SE were increased by 20% and 23%, respectively.

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