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Ge-qun Shu - One of the best experts on this subject based on the ideXlab platform.
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The effects of design parameters on the dynamic behavior of organic ranking cycle for the engine waste heat recovery
Energy, 2018Co-Authors: Xuan Wang, Dongzhan Jing, Ge-qun Shu, Hua Tian, Peng Liu, Xiaoya LiAbstract:Organic Rankine Cycle (ORC) is a suitable way to recover the waste heat of internal combustion engines. Since the engine usually operates under different working conditions, the waste heat recovery system is also under unstable state. Consequently, it is quite meaningful to research the dynamic behavior of the ORC. The dynamic math model of the ORC for waste heat recovery of a natural gas engine is established by Simulink in this paper. Based on these, the effects of design parameters of Evaporating Pressure, condensing Pressure, exhaust outlet temperature and working fluids on the ORC dynamic behavior are researched. The results indicate that the dynamic response speed of the ORC just varies a little with the design Evaporating Pressure, condensing Pressure and exhaust outlet temperature. By contrast, different working fluids lead to quite different dynamic response speed. As a result, when designing the ORC, the working fluid should be considered much more to match the dynamic characters of the engine working condition. Furthermore, it is found that ORCs designed under different Evaporating Pressure, condensing Pressure, exhaust outlet temperature can apply the same PID controller, while it is not suitable for ORCs with different working fluids which have quite distinctive critical temperature.
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Effect factors of part-load performance for various Organic Rankine cycles using in engine waste heat recovery
Energy Conversion and Management, 2018Co-Authors: Xuan Wang, Ge-qun Shu, Hua Tian, Wei Feng, Peng Liu, Xiaoya LiAbstract:The Organic Rankine Cycle (ORC) is regarded as one of the most promising waste heat recovery technologies for electricity generation engines. Since the engine usually operates under different working conditions, it is important to research the part-load performance of the ORC. In order to reveal the effect factors of part-load performance, four different forms of ORCs are compared in the study with dynamic math models established in SIMULINK. They are the ORC applying low temperature working fluid R245fa with a medium heat transfer cycle, the ORCs with high temperature working fluid toluene heated directly by exhaust condensing at low Pressure and high Pressure, and the double-stage ORC. It is regarded that the more slowly the system output power decreases, the better part-load performance it has. Based on a comparison among the four systems, the effects of Evaporating Pressure, condensing condition, working fluid, and system structure on part-load performance are revealed in the work. Further, it is found that the system which best matches with the heat source not only performs well under the design conditions, but also has excellent part-load performance.
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Engine Load Effects on the Energy and Exergy Performance of a Medium Cycle/Organic Rankine Cycle for Exhaust Waste Heat Recovery
MDPI AG, 2018Co-Authors: Peng Liu, Ge-qun Shu, Hua Tian, Xuan WangAbstract:The Organic Rankine Cycle (ORC) has been proved a promising technique to exploit waste heat from Internal Combustion Engines (ICEs). Waste heat recovery systems have usually been designed based on engine rated working conditions, while engines often operate under part load conditions. Hence, it is quite important to analyze the off-design performance of ORC systems under different engine loads. This paper presents an off-design Medium Cycle/Organic Rankine Cycle (MC/ORC) system model by interconnecting the component models, which allows the prediction of system off-design behavior. The sliding Pressure control method is applied to balance the variation of system parameters and Evaporating Pressure is chosen as the operational variable. The effect of operational variable and engine load on system performance is analyzed from the aspects of energy and exergy. The results show that with the drop of engine load, the MC/ORC system can always effectively recover waste heat, whereas the maximum net power output, thermal efficiency and exergy efficiency decrease linearly. Considering the contributions of components to total exergy destruction, the proportions of the gas-oil exchanger and turbine increase, while the proportions of the evaporator and condenser decrease with the drop of engine load
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Engine working condition effects on the dynamic response of organic Rankine cycle as exhaust waste heat recovery system
Applied Thermal Engineering, 2017Co-Authors: Xuan Wang, Ge-qun Shu, Hua Tian, Peng Liu, Dongzhan JingAbstract:Abstract Organic Ranking Cycle (ORC) is paid more and more attention on waste heat recovery of internal combustion engines. The ORC system is usually designed under the rated working condition of engines, while the engine often works under different conditions, which means the ORC system always works at part-load conditions and unsteady state as well. Consequently, the research of ORC dynamic response process is very significant and it is useful to develop the control system which ensures the safety and efficiency of the ORC during the whole running process. ORC is nonlinear system and the dynamic response is not the same under different engine working conditions. Therefore, the dynamic math model of an ORC with a medium heat transfer cycle as waste heat recovery system for a natural gas engine of 1000 kW rated power is built by Simulink in this work. Since ORC is mainly controlled through working fluid pump speed, the dynamic response process to pump speed change of four main ORC parameters (Evaporating Pressure, working fluid enthalpy at the end of heating, superheat degree and condensing Pressure) under various engine working conditions is compared to illustrate the engine working condition effects. The results show that the dynamic response of condensing Pressure does not vary much under different working conditions, while the dynamic response of the other three ORC parameters mentioned above change a lot. Their variation magnitudes become large and their response speeds get slow as the engine working condition declines. Finally, the control system can be improved under low working conditions based on these regularities.
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experimental investigation on thermal os orc oil storage organic rankine cycle system for waste heat recovery from diesel engine
Energy, 2016Co-Authors: Ge-qun Shu, Haiqiao Wei, Hua Tian, Mingru Zhao, Xingyu Liang, Yongzhan Huo, Weijie ZhuAbstract:Abstract With urging needs to decrease the fuel consumption and environment pollution, energy saving and emission reduction technologies in the ICE (internal combustion engine) industry are developed. A thermal OS/ORC (Oil Storage/Organic Rankine Cycle) system was constructed and preliminarily tested for WHR (Waste Heat Recovery) from exhaust gas of a 240 kW diesel engine. The heat balance test of diesel engine without OS/ORC was conducted first to investigate the varying property of exhaust gas, then the OS/ORC system was tested to show its ability against high temperature and variation of exhaust gas. The results show that thermal oil effectively dropped the working temperature of organic fluid to less than 210 °C, which is much lower than the decomposition temperature of many organic fluids. Also, thermal oil brought a significant inertia to the response of system which could be positive against the variation of engine condition. In order to learn more about the operating characteristics of OS/ORC system, the impact of important parameters on each other was investigated quantitatively as well as on the performance of OS/ORC system. The results show that within the given range, higher Evaporating Pressure can obviously improve the performance of OS/ORC while the impact of superheat is nearly negligible.
Joaquín Navarro-esbrí - One of the best experts on this subject based on the ideXlab platform.
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Development and validation of a micro-fin tubes evaporator model using R134a and R1234yf as working fluids
International Journal of Refrigeration, 2015Co-Authors: J.m. Mendoza-miranda, J.j. Ramírez-minguela, V.d. Muñoz-carpio, Joaquín Navarro-esbríAbstract:Abstract This paper presents a model of shell and tube evaporator with micro-fin tubes using R1234yf and R134a. The model developed for this evaporator uses the e-NTU method to predict the Evaporating Pressure, the refrigerant outlet enthalpy and the outlet temperature of the secondary fluid. The model accuracy is evaluated using different two-phase flow boiling correlations for micro-fin tubes and comparing predicted and experimental data. The experimental tests were carried out for a wide range of operating conditions using R134a and R1234yf as working fluids. The predicted parameter with maximum deviations, between the predicted and experimental data, is the Evaporating Pressure. The correlation of Akhavan– Behabadi et al. was used to predict flow boiling heat transfer, with an error on cooling capacity prediction below 5%. Simulations, carried out with this validated model, show that the overall heat transfer coefficient of R1234yf has a maximum decrease of 10% compared with R134a.
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Shell-and-tube evaporator model performance with different two-phase flow heat transfer correlations. Experimental analysis using R134a and R1234yf
Applied Thermal Engineering, 2014Co-Authors: Joaquín Navarro-esbrí, J.m. Mendoza-miranda, Francisco Molés, Bernardo Peris, Ángel Barragán-cervera, Adrián Mota-babiloni, Juan Manuel BelmanAbstract:Abstract This work presents a model of a shell-and-tube evaporator using R1234yf and R134a as working fluids. The model uses the effectiveness-NTU method to predict the evaporation Pressure and the refrigerant and secondary fluid temperatures at the evaporator outlet, using as inputs the geometry of the evaporator, the refrigerant mass flow rate and evaporator inlet enthalpy, and the secondary fluid volumetric flow rate and evaporator inlet temperature. The model performance is evaluated using different two-phase flow heat transfer correlations through model outputs, comparing predicted and experimental data. The output parameter with maximum deviations between the predicted and experimental data is the Evaporating Pressure, being the deviations in outlet temperatures less than 3%. The evaporator model using Kandlikar's correlation obtains the highest precision and the lowest absolute mean error, with 4.87% in the Evaporating Pressure, 0.45% in the refrigerant outlet temperature and 0.03% in the secondary fluid outlet temperature.
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Experimental evaluation of a vapour compression plant performance using R134a, R407C and R22 as working fluids
Applied Thermal Engineering, 2004Co-Authors: Ramón Cabello, E. Torrella, Joaquín Navarro-esbríAbstract:In this paper, the influence of the main operating variables on the energetic characteristics of a vapour compression plant, based on experimental results, is addressed. The experimental tests are performed on a single-stage vapour compression plant using three different working fluids, R134a, R407C and R22. The operating variables considered are the Evaporating Pressure, the condensing Pressure and the superheating degree at the compressor inlet. The performance characteristics followed to analyse the energetic performance are the refrigerating capacity and the power requirements of the reciprocating compressor, presenting and discussing in this work the main experimental results obtained.
E. Torrella - One of the best experts on this subject based on the ideXlab platform.
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boiling heat transfer coefficient variation for r407c inside horizontal tubes of a refrigerating vapour compression plant s shell and tube evaporator
Applied Energy, 2006Co-Authors: E. Torrella, Joaquin Navarroesbri, R CabelloAbstract:Abstract The present paper presents experimental results obtained from a refrigerating vapour-compression plant’s shell-and-tube (1–2) evaporator working with R407C. Several tests have been carried out to study the influence of the Evaporating Pressure and the refrigerant’s mass flow rate on the refrigerant’s boiling heat-transfer coefficient inside horizontal tubes. This work has been performed by analyzing the variations of the evaporator’s overall thermal-resistance, computed using the effectiveness-NTU method, considering the influence of Pressure drops and glide at the evaporator, and finally transferring the results and conclusions to the boiling heat-transfer coefficient. It has been observed that the variations of the boiling heat-transfer coefficient show a dependence on the Evaporating temperature and the refrigerant’s mass-flow rate, which has been analyzed in the test range.
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Experimental evaluation of a vapour compression plant performance using R134a, R407C and R22 as working fluids
Applied Thermal Engineering, 2004Co-Authors: Ramón Cabello, E. Torrella, Joaquín Navarro-esbríAbstract:In this paper, the influence of the main operating variables on the energetic characteristics of a vapour compression plant, based on experimental results, is addressed. The experimental tests are performed on a single-stage vapour compression plant using three different working fluids, R134a, R407C and R22. The operating variables considered are the Evaporating Pressure, the condensing Pressure and the superheating degree at the compressor inlet. The performance characteristics followed to analyse the energetic performance are the refrigerating capacity and the power requirements of the reciprocating compressor, presenting and discussing in this work the main experimental results obtained.
H. Asada - One of the best experts on this subject based on the ideXlab platform.
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Modeling of vapor compression cycles for advanced controls in HVAC systems
Proceedings of 1995 American Control Conference - ACC'95, 1995Co-Authors: Xiangdong He, H. AsadaAbstract:This paper presents a new lumped-parameter model for describing the dynamics of vapor compression cycles. In particular, the dynamics associated with the two heat exchangers, i.e. the evaporator and the condenser, are modeled based on a moving-interface approach by which the position of the two-phase/single-phase interface inside the one-dimensional heat exchanger can be properly predicted. This model relates critical performance outputs, such as Evaporating Pressure, condensing Pressure, and superheat, to actuating inputs including compressor speed, fan speed, and expansion valve opening. In view of regulating multiple performance outputs in modern heat pumps and air conditioning systems, this model is highly useful for the design of multivariable feedback control.
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Multivariable feedback design for regulating vapor compression cycles
Proceedings of 1995 American Control Conference - ACC'95, 1995Co-Authors: Xiangdong He, H. AsadaAbstract:This paper presents multivariable feedback control design for regulating a vapor compression cycle based on a lumped-parameter model. In particular, the conventional control strategy of SISO systems is studied based on the model and experimental tests, and compared to multivariable feedback control. It is shown that multivariable control of compressor speed and expansion valve opening has better performance than the existing SISO control method in regulating superheat and Evaporating Pressure. More importantly, with variable-speed compressor, electronic expansion, indoor and outdoor fans, Evaporating and condensing Pressures, the refrigerant superheat as well as subcool values can be simultaneously controlled to have the desired values such that desired COP can be maintained under different ambient conditions. It is expected that active multivariable feedback control will have wide applications in HVAC&R systems including air conditioners, heat pumps, and refrigerators etc. to achieve high performance and high energy-efficiency.
A. Greco - One of the best experts on this subject based on the ideXlab platform.
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Experimental two-phase Pressure gradients during evaporation of pure and mixed refrigerants in a smooth horizontal tube. Comparison with correlations
Heat and Mass Transfer, 2006Co-Authors: A. Greco, Giuseppe Peter VanoliAbstract:The paper reports the results of an experimental study on Pressure drop during horizontal flow boiling of refrigerants R22, R507, R404A, R134a, R407C and R410A. The test section is a smooth, horizontal, stainless steel tube (6 mm I.D., 6 m length) uniformly heated by Joule effect. The experimental tests are carried out at an almost constant Evaporating Pressure of 7.0 bar varying the mass flow rate in the range 280–1,080 kg/m^2 s. The experimental comparison clearly shown that the Pressure drop of R22 is significantly higher as compared to all the other fluids. The results are compared against well-known Pressure drop prediction methods. The available correlations can be used for both pure fluids and mixtures with no corrective factors, provided the mixture properties are evaluated at local compositions. The Chawla friction correlation is the best-fitting of our experimental data in combination with the heterogeneous momentum Pressure drop model on the basis of the Rouhani-Axelsson void fraction correlation.
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Flow boiling heat transfer with HFC mixtures in a smooth horizontal tube. Part I: Experimental investigations
Experimental Thermal and Fluid Science, 2005Co-Authors: A. Greco, G.p. VanoliAbstract:Abstract The substitution of working fluids in vapour-compression plants causes major problems, because of a reduced plant performance. Therefore, extremely accurate design procedures are needed, because the relative sizing of each plant-component is essential for the cycle performance. For this reason, the knowledge of the heat-transfer characteristics of new fluids in condensers and evaporators is mandatory. The heat-transfer characteristics of R410A and R404A were experimentally investigated and analyzed as a function of Evaporating Pressure, heat- and mass flux. The test section was a smooth, horizontal, stainless steel tube (6 mm ID, 6 m length) uniformly heated by the Joule effect. The working parameter was varied within the following ranges: Evaporating Pressure 3–12 bar, refrigerant mass-flux 290–1100 kg/m 2 s, heat flux 11–39 kW/m 2 , respectively.
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Evaporation of refrigerants in a smooth horizontal tube: prediction of R22 and R507 heat transfer coefficients and Pressure drop
Applied Thermal Engineering, 2004Co-Authors: A. Greco, Giuseppe Peter VanoliAbstract:This paper presents experimental heat transfer coefficients and Pressure drop results obtained during the evaporation of pure R22 and the azeotropic mixture R507 (R125–R143a 50%/50% in weight). The test section was a smooth, horizontal, stainless steel tube (6 mm ID, 6 m length) uniformly heated by Joule effect. The effects of heat flux, mass flux and evaporation Pressure on the heat transfer coefficients have been investigated. Each working parameter was bound within the range: Evaporating Pressure 3–12 bar, refrigerant mass-flux 250–286 kg/m 2 s, heat flux 10.6–17.0 kW/m 2 , respectively. Additionally the experimental results have been compared with existing correlations which characterize the evaporative heat transfer coefficient to assess the validity of these models for refrigerant mixtures. 2004 Published by Elsevier Ltd.