scholarly journals Analysis of heat transfer and irreversibility of organic rankine cycle evaporator for selecting working fluid and operating conditions

2020 ◽  
Vol 24 (3 Part B) ◽  
pp. 2013-2022
Author(s):  
Shuang Ye ◽  
Yan Xu ◽  
Yu Chen ◽  
Wei Huang
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Thermal Resistance ◽  
Heat Transfer Performance ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Transfer Performance ◽  
Irreversible Loss

Organic Rankine cycle (ORC) is suitable to converting the normally hard to utilize low temperature thermal energies, such as geothermal energy, solar energy, and industrial waste heat, to electricity through utilizing low boiling organic working fluids. The performance of ORC system is dramatically affected by the selections of working fluid and working conditions. As a key component of waste heat recovery, the irreversible loss of evaporator also has great influence on the performance of ORC system. In this paper, we study the heat transfer performance in evaporator under the condition that the heat source parameters and pinch point temperature difference are identified. It is found that the heat transfer performance is affected by Cr, the ratio of heat capacity flow rates between the working fluid and the heat source fluid. The equivalent thermal resistance, deducing from the concept of entransy, to measure the irreversability during the heat transfer process is used. Then, the parameter ?r, the ratio between latent heat and sensible heat of working fluid is defined. With the parameters Cr and ?r, we investigate the relationship between the heat transfer and irreversible loss, and deduce the condition that maximum heat transfer and minimum equivalent thermal resistance occurs. Finally, a calculation method is established to choose the optimum working fluid and the evaporation condition.

Calculation and Optimization of Heat Transfer between the Low Exergy Heat Source and Organic Rankine Cycle Applied to Heat Recovery Systems

2013 ◽  
Vol 597 ◽  
pp. 45-50
Author(s):  
Sławomir Smoleń ◽  
Hendrik Boertz
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Heat Recovery ◽  
Power Plants ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Optimization Procedure ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Total System

One of the key challenges on the area of energy engineering is the system development for increasing the efficiency of primary energy conversion and use. An effective and important measure suitable for improving efficiencies of existing applications and allowing the extraction of energy from previously unsuitable sources is the Organic Rankine Cycle. Applications based on this cycle allow the use of low temperature energy sources such as waste heat from industrial applications, geothermal sources, biomass, fired power plants and micro combined heat and power systems.Working fluid selection is a major step in designing heat recovery systems based on the Organic Rankine Cycle. Within the framework of the previous original study a special tool has been elaborated in order to compare the influence of different working fluids on performance of an ORC heat recovery power plant installation. A database of a number of organic fluids has been developed. The elaborated tool should create a support by choosing an optimal working fluid for special applications and become a part of a bigger optimization procedure by different frame conditions. The main sorting criterion for the fluids is the system efficiency (resulting from the thermo-physical characteristics) and beyond that the date base contains additional information and criteria, which have to be taken into account, like environmental characteristics for safety and practical considerations.The presented work focuses on the calculation and optimization procedure related to the coupling heat source – ORC cycle. This interface is (or can be) a big source of energy but especially exergy losses. That is why the optimization of the heat transfer between the heat source and the process is (besides the ORC efficiency) of essential importance for the total system efficiency.Within the presented work the general calculation approach and some representative calculation results have been given. This procedure is a part of a complex procedure and program for Working Fluid Selection for Organic Rankine Cycle Applied to Heat Recovery Systems.

Theoretical and experimental investigation of an organic Rankine cycle for a waste heat recovery system

2009 ◽  
Vol 223 (5) ◽  
pp. 523-533 ◽  
Author(s):  
W Gu ◽  
Y Weng ◽  
Y Wang ◽  
B Zheng
Keyword(s):  
Heat Source ◽  
Entropy Generation ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Entropy Generation Rate ◽  
Working Fluid ◽  
Total Entropy ◽  
Waste Heat Recovery System ◽  
Cycle Efficiency

This article describes and evaluates an organic Rankine cycle (ORC) for a waste heat recovery system by both theoretical and experimental studies. Theoretical analysis of several working fluids shows that cycle efficiency is very sensitive to evaporating pressure, but insensitive to expander inlet temperature. Second law analysis was carried out using R600a as a working fluid and a flow of hot air as a heat source, which is not isothermal, along the evaporator. The result discloses that the evaporator's internal and external entropy generation is the main source of total entropy generation. The effect of the heat source temperature, evaporating pressure, and evaporator size on the entropy generation rate is also presented. The obtained useful power is directly linked to the total entropy generation rate according to the Gouy—Stodola theorem. The ORC testing system was established and operated using R600a as a working fluid and hot water as a heat source. The maximum cycle efficiency of the testing system is 5.2 per cent, and the testing result also proves that cycle efficiency is insensitive to heat source temperature, but sensitive to evaporating pressure. The entropy result also shows that internal and external entropy of the evaporator is the main source of total entropy generation.

scholarly journals Configuration Selection of the Multi-Loop Organic Rankine Cycle for Recovering Energy from a Single Source

Entropy ◽  
2021 ◽  
Vol 23 (11) ◽  
pp. 1435
Author(s):  
Youyi Li ◽  
Tianhao Tang
Keyword(s):  
Heat Source ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Optimal Solution ◽  
Rankine Cycle ◽  
Optimal Number ◽  
Exergy Efficiency ◽  
Working Fluid ◽  
Levelized Cost Of Electricity ◽  
Multi Objective

The Organic Rankine Cycle (ORC) is a well-established way to recover energy from a single waste heat source. This paper aims to select the suitable configuration, number of loops, and working fluids for the Multi-Loop ORC (MLORC) by using multi-objective optimization. The thermodynamic and economic performance of MLORC in three various configurations was analyzed. Multi-objective optimizations of the series and parallel MLORC using different working fluid groups were conducted to find the optimal configuration, number of loops, and working fluid combination. The analysis results show that the series–parallel MLORC performed the worst among the three configurations. The optimization results reveal that series MLORC has a higher exergy efficiency than the parallel MLORC. The exergy efficiency of the optimal solution in series dual-loop, triple-loop, and quadruple-loop ORC is 9.3%, 7.98%, and 6.23% higher than that of parallel ORC, respectively. Furthermore, dual-loop is the optimal number of cycles for recovering energy from a single heat source, according to the grey relational grade. Finally, the series dual-loop ORC using cyclohexane\cyclohexane was the suitable configuration for utilizing a single waste heat source. The exergy efficiency and levelized cost of electricity of the series dual-loop ORC with the optimal parameters are 62.18% and 0.1509 $/kWh, respectively.

scholarly journals Multi-objective optimization of CuO based organic Rankine cycle operated using R245ca

2019 ◽  
Vol 116 ◽  
pp. 00062 ◽  
Author(s):  
Parth Prajapati ◽  
Vivek Patel
Keyword(s):  
Heat Transfer ◽  
Thermal Efficiency ◽  
Heat Exchangers ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Multi Objective Optimization ◽  
Multi Objective ◽  
Source Fluid

The present work deals with multi objective optimization of nanofluid based Organic Rankine Cycle (ORC) to utilise waste heat energy. Working fluid considered for the study is R245ca for its good thermodynamic properties and lower Global Warming Potential (GWP) compared to the conventional fluids used in the waste heat recovery system. Heat Transfer Search (HTS) algorithm is used to optimize the objective functions which tends to maximize thermal efficiency and minimize Levelised Energy Cost (LEC). To enhance heat transfer between the working fluid and source fluid, nanoparticles are added to the source fluid. Application of nanofluids in the heat transfer system helps in maximizing recovery of the waste heat in the heat exchangers. Based on the availability and cost, CuO nanoparticles are considered for the study. Effect of Pinch Point Temperature Difference (PPTD) and concentration of nanoparticles in heat exchangers is studied and discussed. Results showed that nanofluids based ORC gives maximum thermal efficiency of 18.50% at LEC of 2.59 $/kWh. Total reduction of 7.11% in LEC can be achieved using nanofluids.

A Computer Program for Working Fluid Selection of Low Temperature Organic Rankine Cycle

2015 ◽  
Author(s):  
Muhammad Ansab Ali ◽  
Tariq Saeed Khan ◽  
Ebrahim Al Hajri ◽  
Zahid H. Ayub
Keyword(s):  
Low Temperature ◽  
Heat Source ◽  
Computer Program ◽  
Fossil Fuels ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Power Production ◽  
Working Fluid ◽  
Low Grade

Fossil fuels are continuously depleting while the global energy demand is growing at a fast rate. Additionally, fossil fuels based power plants contribute to environmental pollution. Search for alternate energy resources and use of industrial waste heat for power production are attractive topics of interest these days. One way of enhancing power production and decreasing the environmental impact is by recuperating and utilizing low grade thermal energy. In recent years, research on use of organic Rankine cycle (ORC) has gained popularity as a promising technology for conversion of heat into useful work or electricity. Due to simple structure of ORC system, it can be easily integrated with any energy source like geothermal energy, solar energy and waste heat. A computer program has been developed in engineering equation solver (EES) environment that analyzes and selects appropriate working fluid for organic Rankine cycle design based on available heat sources. For a given heat source, the program compares energy and exergy performance of various working fluids. The program also includes recuperator performance analysis and compares its effectiveness on the overall thermal performance of the Rankine cycle. This program can assist in preliminary design of ORC with respect to best performing refrigerant fluid selection for the given low temperature heat source.

scholarly journals Study on Heat Transfer Performance of Non-integral Capillary Core Sintered Uniform Plate

2021 ◽  
Vol 7 (5) ◽  
pp. 292-301
Keyword(s):  
Heat Transfer ◽  
Particle Size ◽  
Heat Source ◽  
Thermal Resistance ◽  
Copper Powder ◽  
Heat Transfer Performance ◽  
Copper Plate ◽  
Transfer Performance ◽  
Filling Rate ◽  
Large Particle Size

This paper mainly introduces the sintering process of the monolithic capillary wick and analyzes the influence of different copper powder particle size, filling rate, copper powder shape and heat source size on the heat transfer performance of the isothermal plate. The experimental results show that: (1) For the isothermal plate sintered with spherical copper powder, the capillary force of large particle size copper powder is small, but the flow resistance is also small, and the performance of the isothermal plate sintered with large particle size copper powder is better. (2) In the case of low filling rate, the isothermal plate is dried due to insufficient return fluid. In the case of high filling rate, on the one hand, the thickness of the liquid film at the evaporation end of the isothermal plate is large, resulting in additional thermal resistance. On the other hand, the thin film evaporation mode will be transformed into pool boiling mode, which will reduce the heat transfer performance. (3) Spherical copper powder sintered plate with regular shape has the best performance, while dendritic copper powder sintered plate has relatively high thermal resistance. (4) The heat source area has a great influence on the thermal resistance of the plate. Under the same heating power, the thermal resistance of the small area heat source is much higher than that of the large area heat source; The thermal resistance of sintered copper plate is lower than that of pure copper plate under two heat source areas.

An Investigation of Flat-Plate Oscillating Heat Pipes

2010 ◽  
Author(s):  
Peng Cheng ◽  
Scott Thompson ◽  
Joe Boswell ◽  
Hongbin Ma
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Flat Plate ◽  
Heat Transfer Performance ◽  
Operating Temperature ◽  
Pure Water ◽  
Heat Pipes ◽  
Copper Plate ◽  
Working Fluid ◽  
Transfer Performance

The heat transfer performance of flat-plate oscillating heat pipes (FP-OHPs) was investigated experimentally and theoretically. Two layers of channels were created by machining grooves on both sides of copper plate, in order to increase the channel number per unit volume. The channels had rectangular cross-sections with hydraulic diameters ranging from 0.762 mm to 1.389 mm. Acetone, water and diamond/acetone, gold/water and diamond/water nanofluids were tested as working fluids. It was found that the FP-OHP’s thermal resistance depended on the power input and operating temperature. The FP-OHP charged with pure water achieved a thermal resistance of 0.078°C/W while removing 560 W with a heat flux of 86.8 W/cm2. The thermal resistance was further decreased when nanofluid was used as the working fluid. A mathematical model predicting the heat transfer performance was developed to predict the effects of channel dimension, heating mode, working fluid and operating temperature on the thermal performance of the FP-OHP. Results presented here will assist in optimization of the FP-OHP and provide a better understanding of heat transfer mechanisms occurring in an OHPs.

Research on Thermal Resistance of Micro Heat Pipe with Sintered Wick

2013 ◽  
Vol 589-590 ◽  
pp. 552-558
Author(s):  
Xi Bing Li ◽  
Xun Wang ◽  
Yun Shi Ma ◽  
Zhong Liang Cao
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
High Heat ◽  
Working Fluid ◽  
Transfer Performance ◽  
Total Thermal Resistance ◽  
Vapor Cavity ◽  
Micro Heat Pipe

As a highly efficient heat dissipation unit, a micro heat pipe is widely used in high heat flux microelectronic chips, and its thermal resistance is crucial to heat transfer capacity. Through analyses of the structure and heat transfer performance of a circular heat pipe with sintered wick, the theoretical model of total thermal resistance was established on heat transfer theory, and then simplified, finally a testing platform was set up to test for total thermal resistance performance. The testing results show that when the micro heat pipe is in optimal heat transfer state, its total thermal resistance conform well with that from the theoretical model, and its actual thermal resistance is much lower than that of the rod made of the material with perfect thermal conductivity and of the same geometric size. With the increment of heat transfer capability, the total thermal resistance of a micro heat pipe with sintered wick decreases first, then increases and reaches the minimum when it is in the optimal heat transfer state. The greater total thermal resistance in low heat transfer performance is mainly caused by too much working fluid accumulating in evaporator and the lower velocity in vapor cavity, and the greater total thermal resistance in high heat transfer performance is mainly due to the working fluid drying up in condenser. Total thermal resistance is related to many factors, such as thermal conductivity of tube-shell material, wall thickness, wick thickness, copper powders grain size and porosity, the lengths of condenser and evaporator, and the diameter of vapor cavity etc.. Therefore, the structure parameters of a micro heat pipe with sintered wick should be reasonably designed according to the specific conditions to ensure its heat transfer capacity and total thermal resistance to meet the requirements.

scholarly journals Research on Performance Test Characteristics of Solar Energy ORC Generator Set

2018 ◽  
Vol 232 ◽  
pp. 04007
Author(s):  
Yongkang Zhang ◽  
Jinghui Song ◽  
Yunfeng Xia
Keyword(s):  
Heat Transfer ◽  
Power Generation ◽  
Heat Source ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Source Condition ◽  
Power Cycle ◽  
Solar Powered ◽  
Regenerative Cycle

In order to study the performance of low-temperature solar-powered ORC generator sets, a solar-powered ORC power generation test bench was designed and built. In the experiment, R-123 was used as the organic Rankine cycle working fluid, and the solar ORC power generation system was experimentally studied. The research results show that when the direct solar radiation intensity is about 400W, the temperature of the heat transfer oil at the outlet of the collector can reach 140 °C. When the temperature of the heat transfer oil at the outlet of the collector is around 110°C, the collector efficiency of the collector can reach about 60%. Under the heat source condition, when the power cycle part is switched from the basic cycle to the regenerative cycle mode, the collector heat collection efficiency can reach about 60%. Under the heat source condition, when the power cycle part is switched from the basic cycle mode to the regenerative cycle mode, the measured efficiency is increased from 9.3% to 10.8%, and the measured cycle efficiency is increased from 1.57% to 1.67%, which is an increase of 6.07%. The measured cycle system efficiency is about 10%, and the heat recovery mode is slightly higher than the basic cycle mode. The organic Rankine cycle performance under different working fluid flows was also investigated in the experiment. The maximum measured average power was 386.27 W when the working fluid flow was 6.88 kg·s. At a certain heat source temperature, as the flow rate of the working fluid increases, the inlet pressure of the expander increases, and the circulating output work also increases. Under a certain working fluid flow rate, as the temperature of the heat source increases, the temperature of the inlet of the expander increases, and the inlet pressure increases. the cycle output work also increased.

scholarly journals Zeotropic Mixture Selection for an Organic Rankine Cycle Using a Single Screw Expander

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1022
Author(s):  
Xinxin Zhang ◽  
Yin Zhang ◽  
Zhenlei Li ◽  
Jingfu Wang ◽  
Yuting Wu ◽  
...  
Keyword(s):  
Heat Source ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Energy Utilization ◽  
Working Fluid ◽  
Low Grade ◽  
Outlet Temperature ◽  
Single Screw ◽  
Zeotropic Mixture

The organic Rankine cycle (ORC) is a popular and promising technology that has been widely studied and adopted in renewable and sustainable energy utilization and low-grade waste heat recovery. The use of zeotropic mixtures in ORC has been attracting more and more attention because of the possibility to match the temperature profile of the heat source by non-isothermal phase change, which reduces the irreversibility in the evaporator and the condenser. The selection of working fluid and expander is strongly interconnected. As a novel expander, a single screw expander was selected and used in this paper for efficient utilization of the wet zeotropic mixtures listed in REFPROP 9.1 in a low-temperature subcritical ORC system. Five indicators, namely net work, thermal efficiency, heat exchange load of condenser, temperature glide in evaporator, and temperature glide in condenser, were used to analyze the performance of an ORC system with wet and isentropic zeotropic mixtures as working fluids. The calculation and analysis results indicate that R441A with an expander outlet temperature of 320 K may be the suitable zeotropic mixture used for both open and close type heat source. R436B may be selected with an expander outlet temperature of 315 K. R432A may be selected with an expander outlet temperature from 295 K to 310 K.

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