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2 pages, 166 KiB

Open AccessEditorial

Special Issue on Thermodynamic and Exergy Analyses of Cooling, Power, and Energy Systems

by Xiaolin Wang and Firoz Alam

Appl. Sci. 2022, 12(23), 12364; https://doi.org/10.3390/app122312364 - 2 Dec 2022

Viewed by 829

Abstract

Due to the energy crisis and environmental impact caused by fossil fuel energy, improving the efficiency of cooling, power, and energy systems has become one of the most important aspects of energy sectors [...] Full article

(This article belongs to the Special Issue Thermodynamic and Exergy Analyses of Cooling, Power, and Energy Systems)

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17 pages, 7137 KiB

Open AccessArticle

Investigation on Dynamic Characteristics of the Reed Valve in Compressors Based on Fluid-Structure Interaction Method

by Yanfeng Wang, Jin Wang, Zhilong He, Junwei Sun, Tao Wang and Changhai Liu

Appl. Sci. 2021, 11(9), 3946; https://doi.org/10.3390/app11093946 - 27 Apr 2021

Cited by 8 | Viewed by 2712

Abstract

The flow in the gap between the reed and the valve seat has a significant influence on the dynamic characteristics of the reed valve used in reciprocating compressors. The fluid–structure interaction (FSI) method is an effective method for studying reciprocating compressors. A three-dimensional [...] Read more.

The flow in the gap between the reed and the valve seat has a significant influence on the dynamic characteristics of the reed valve used in reciprocating compressors. The fluid–structure interaction (FSI) method is an effective method for studying reciprocating compressors. A three-dimensional FSI model of a reciprocating compressor with a reed valve is established in this paper, which has an important influence on the flow rate characteristic of reciprocating compressors. Furthermore, an experimental investigation is implemented to verify the FSI model. Based on the established FSI model, the pressure distribution on the reed valve surface is identified by varying the height of the suction valve limiter and the rotational speed of the compressor, which has an important effect on the dynamic characteristics of the reed valve. Although the low-pressure region, due to the Bernoulli effect on the surface of the reed, hinders the rapid opening of the valve to some extent, it is obviously beneficial to the timely closure of the valve and increases the volumetric efficiency of the compressor. Moreover, the optimal height of the valve limiter and the appropriate rotational speed of the compressor are obtained. Full article

(This article belongs to the Special Issue Thermodynamic and Exergy Analyses of Cooling, Power, and Energy Systems)

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25 pages, 846 KiB

Open AccessArticle

Residue Cost Formation of a High Bypass Turbofan Engine

by Lugo-Méndez Helen, Castro-Hernández Sergio, Salazar-Pereyra Martín, Valencia-López Javier, Torres-González Edgar Vicente and Lugo-Leyte Raúl

Appl. Sci. 2020, 10(24), 9060; https://doi.org/10.3390/app10249060 - 18 Dec 2020

Cited by 6 | Viewed by 3082

Abstract

The kinetic energy produced by a turbofan engine is inseparable from the unavoidable generation of waste heat dissipated into the environment and the chemical exergy of exhaust gases. However, exergoeconomic cost analyses of these propulsion systems have focused only on the formation process [...] Read more.

The kinetic energy produced by a turbofan engine is inseparable from the unavoidable generation of waste heat dissipated into the environment and the chemical exergy of exhaust gases. However, exergoeconomic cost analyses of these propulsion systems have focused only on the formation process of the functional product and not the cost of residue formation. In this study, symbolic thermoeconomics was applied to evaluate the impact of residue formation on the production costs of a turbofan engine and analyze the effect of component malfunctions on the fuel impact formula for diagnosing anomalies. The GE90-115B high bypass turbofan engine under takeoff conditions and a thrust requirement of 510 kN was considered as a case study. The total exergoeconomic cost of the engine was 26,754.28 USD/h: 61.04% corresponded to external resources; 0.14% and 33.07% corresponded to waste heat dissipated from the bypass and core engine, respectively; 3.28% corresponded to the chemical exergy of the exhaust gases; 2.47% corresponded to capital and operating costs. A malfunction analysis revealed that a 1% reduction in the isentropic efficiency of the compressor reduced the total kinetic exergy by −0.77 MW, increased fuel consumption by 0.49 MW, and generated irreversibility and residue of 0.80 and 0.45 MW, respectively. Full article

(This article belongs to the Special Issue Thermodynamic and Exergy Analyses of Cooling, Power, and Energy Systems)

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14 pages, 4673 KiB

Open AccessArticle

Development and Testing of a Roots Pump for Hydrogen Recirculation in Fuel Cell System

by Linfen Xing, Jianmei Feng, Wenqing Chen, Ziyi Xing and Xueyuan Peng

Appl. Sci. 2020, 10(22), 8091; https://doi.org/10.3390/app10228091 - 15 Nov 2020

Cited by 19 | Viewed by 3658

Abstract

In this paper, the development and testing of a Roots pump with a new rotor profile for hydrogen recirculation in the fuel cell system are presented. The design method of the rotor profile, port position, and structure of the pump is presented. A [...] Read more.

In this paper, the development and testing of a Roots pump with a new rotor profile for hydrogen recirculation in the fuel cell system are presented. The design method of the rotor profile, port position, and structure of the pump is presented. A prototype of a three-lobe Roots pump with helical rotors was fabricated, and its performance was experimentally tested. The measured data show that the effect of the pressure difference on the flow rate and volumetric efficiency of the Roots pump is the most significant, while the effect of suction pressure is limited. It is concluded that the leakage rather than flow resistance is the key factor, which has a major influence on volumetric and isentropic efficiency. The comparison of the performance is also given by the measured results of the same Roots pump working with air, helium, and hydrogen. Finally, the successful integration of the Roots pumps into three PEM fuel cell systems is reported and the optimal operating parameters of the Roots pump in the systems under various loads are also presented. It is found that the performance of the Roots pump integrated into the fuel cell system is better than that measured with pure hydrogen on the test rig. The performance maps composed of all the measured data of the Roots pump are very helpful for the optimal design and operation of the fuel cell system. Full article

(This article belongs to the Special Issue Thermodynamic and Exergy Analyses of Cooling, Power, and Energy Systems)

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15 pages, 4248 KiB

Open AccessArticle

Effects of Working Fluids on the Performance of a Roots Pump for Hydrogen Recirculation in a PEM Fuel Cell System

by Jianmei Feng, Linfen Xing, Bingqi Wang, Huan Wei and Ziyi Xing

Appl. Sci. 2020, 10(22), 8069; https://doi.org/10.3390/app10228069 - 13 Nov 2020

Cited by 17 | Viewed by 3280

Abstract

In this paper, the performance of a Roots pump for hydrogen recirculation in proton exchange membrane (PEM) fuel cell system is simulated based on CFD modeling. The Roots pump is in a three-lobe configuration with helical rotors, and it is developed specifically for [...] Read more.

In this paper, the performance of a Roots pump for hydrogen recirculation in proton exchange membrane (PEM) fuel cell system is simulated based on CFD modeling. The Roots pump is in a three-lobe configuration with helical rotors, and it is developed specifically for fuel cell systems between 60 to 110 kW. A three-dimensional model of the Roots pump is established to predict the pump performance, including the flow rate and power consumption under various operating conditions. Extensive simulations were conducted and then verified experimentally by operating with working fluids of air and helium. Based on the validated CFD model, the contents of water vapor and nitrogen in the hydrogen recirculated are taken into account to evaluate the Roots pump performance numerically according to the actual conditions of the recirculating hydrogen at the stack outlet. It is shown that the volumetric efficiency and isentropic efficiency are improved with the increase fraction of water vapor and nitrogen. It is found that the performance of the Roots pump integrated in the PEM fuel cell system is between the performance of the pump working with air and helium. Finally, correlations of volumetric efficiency and isentropic efficiency are given based on the CFD results to show the general pattern of this kind of hydrogen pump. It is believed that these equations are very helpful to the design and operation control of the PEM fuel cell system. Full article

(This article belongs to the Special Issue Thermodynamic and Exergy Analyses of Cooling, Power, and Energy Systems)

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11 pages, 3036 KiB

Open AccessArticle

Investigation on the Mass Flow Rate of a Refrigerator Compressor Based on the p–V Diagram

by Zhilong He, Dantong Li, Lantian Ji, Xiaolin Wang and Tao Wang

Appl. Sci. 2020, 10(19), 6650; https://doi.org/10.3390/app10196650 - 23 Sep 2020

Cited by 2 | Viewed by 4097

Abstract

The refrigerant mass flow rate of a refrigerator compressor can only be measured by a mass flow meter and heat balance method. This paper focuses on the expansion and compression phase in which the compressor cylinder is closed, and proposes a measurement method [...] Read more.

The refrigerant mass flow rate of a refrigerator compressor can only be measured by a mass flow meter and heat balance method. This paper focuses on the expansion and compression phase in which the compressor cylinder is closed, and proposes a measurement method of instantaneous mass flow of the refrigerator compressor. The comparison of the experimental pressure variation in the p–V diagram and the theoretical adiabatic process implied that the expansion and compression process of the refrigerator compressor approximated the adiabatic process. Based on the approximations and the experimental p–V diagram, a calculation method for refrigerant mass in the cylinder during the expansion and compression phase is proposed. Subsequently, the mass flow of the refrigerator compressor can be obtained. Furthermore, compared with experimental data and based on the method proposed in this paper, the error of the mass flow rate obtained is less than 3.13%. Based on this calculation method and the experimental p–V diagram, the influence of suction pressure on compressor performance is investigated. Full article

(This article belongs to the Special Issue Thermodynamic and Exergy Analyses of Cooling, Power, and Energy Systems)

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21 pages, 28399 KiB

Open AccessArticle

Energy and Exergy Analyses of a Combined Infrared Radiation-Counterflow Circulation (IRCC) Corn Dryer

by Chengjie Li, Bin Li, Junying Huang and Changyou Li

Appl. Sci. 2020, 10(18), 6289; https://doi.org/10.3390/app10186289 - 10 Sep 2020

Cited by 10 | Viewed by 2389

Abstract

Energy consumption performance evaluation of an industrial grain dryer is an essential step to check its current status and to put forward suggestions for more effective operation. The present work proposed a combined IRCC dryer with drying capacity of 4.2 t/h that uses [...] Read more.

Energy consumption performance evaluation of an industrial grain dryer is an essential step to check its current status and to put forward suggestions for more effective operation. The present work proposed a combined IRCC dryer with drying capacity of 4.2 t/h that uses a novel drying technology. Moreover, the existing energy–exergy methodology was applied to evaluate the performance of the dryer on the basis of energy efficiency, heat loss characteristics, energy recovery, exergy flow and exegetic efficiency. The results demonstrated that the average drying rate of the present drying system was 1.1 g_water/g_{wet matter} h. The energy efficiency of the whole drying system varied from 2.16% to 35.21% during the drying process. The overall recovered radiant energy and the average radiant exergy rate were 674,339.3 kJ and 3.54 kW, respectively. However, the average heat-loss rate of 3145.26 MJ/h indicated that measures should be put in place to improve its performance. Concerning the exergy aspect, the average exergy rate for dehydration was 462 kW and the exergy efficiency of the whole drying system ranged from 5.16% to 38.21%. Additionally, the exergy analysis of the components indicated that the combustion chamber should be primarily optimized among the whole drying system. The main conclusions of the present work may provide theoretical basis for the optimum design of the industrial drying process from the viewpoint of energetics. Full article

(This article belongs to the Special Issue Thermodynamic and Exergy Analyses of Cooling, Power, and Energy Systems)

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14 pages, 6708 KiB

Open AccessArticle

Analysis and Optimization of Truck Windshield Defroster

by Zhilong He, Xide Qu, Lantian Ji, Weifeng Wu and Xiaolin Wang

Appl. Sci. 2020, 10(16), 5671; https://doi.org/10.3390/app10165671 - 15 Aug 2020

Cited by 5 | Viewed by 3334

Abstract

Frosting and fogging of automobile windshields is a common problem that emerges in daily driving. It is important and essential to quickly and completely defrost the windshield for safety purposes. In this study, a three-dimensional mathematical model was applied to investigate the flow [...] Read more.

Frosting and fogging of automobile windshields is a common problem that emerges in daily driving. It is important and essential to quickly and completely defrost the windshield for safety purposes. In this study, a three-dimensional mathematical model was applied to investigate the flow distribution and flow characteristics on the windshield of a medium-size Model N800 truck. The simulation results were first compared with experimental data. The results showed that the simulation model could reliably predict the defrosting performance on the windshield. This model was then used to optimize the design of the defrosting duct that comprised the main part of the defroster. It was found that the guide plate and outlet position of the defrosting duct were the two major factors affecting the defrosting performance. Therefore, the guide plate was first optimized and the defrosting performance was analyzed. The results showed that the average pressure loss dropped by 21.56%, while the defrosting efficiency at the front white zone was improved to 89%. The position of the outlet of the airflow was further studied. The results showed that the defrosting efficiency at the front zone could be further improved to 99%. Full article

(This article belongs to the Special Issue Thermodynamic and Exergy Analyses of Cooling, Power, and Energy Systems)

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28 pages, 4400 KiB

Open AccessArticle

Regenerative Organic Rankine Cycle as Bottoming Cycle of an Industrial Gas Engine: Traditional and Advanced Exergetic Analysis

by Javier Cardenas Gutierrez, Guillermo Valencia Ochoa and Jorge Duarte-Forero

Appl. Sci. 2020, 10(13), 4411; https://doi.org/10.3390/app10134411 - 27 Jun 2020

Cited by 25 | Viewed by 3003

Abstract

This investigation shows a traditional and advanced exergetic assessment of a waste heat recovery system based on recuperative ORC (organic Rankine cycle) as bottoming cycle of a 2 MW natural gas internal combustion engine. The advanced exergetic evaluation divides the study into two [...] Read more.

This investigation shows a traditional and advanced exergetic assessment of a waste heat recovery system based on recuperative ORC (organic Rankine cycle) as bottoming cycle of a 2 MW natural gas internal combustion engine. The advanced exergetic evaluation divides the study into two groups, the avoidable and unavoidable group and the endogenous and exogenous group. The first group provides information on the efficiency improvement potential of the components, and the second group determines the interaction between the components. A sensitivity analysis was achieved to assess the effect of condensing temperature, evaporator pinch, and pressure ratio with net power, thermal efficiencies, and exergetic efficiency for pentane, hexane, and octane as organic working fluids, where pentane obtained better energy and exergetic results. Furthermore, an advanced exergetic analysis showed that the components that had possibilities of improvement were the evaporator (19.14 kW) and the turbine (8.35 kW). Therefore, through the application of advanced exergetic analysis, strategies and opportunities for growth in the thermodynamic performance of the system can be identified through the avoidable percentage of destruction of exergy in components. Full article

(This article belongs to the Special Issue Thermodynamic and Exergy Analyses of Cooling, Power, and Energy Systems)

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16 pages, 2388 KiB

Open AccessArticle

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

by Kyoung Hoon Kim, Hyung Jong Ko and Chul Ho Han

Appl. Sci. 2020, 10(5), 1813; https://doi.org/10.3390/app10051813 - 6 Mar 2020

Cited by 4 | Viewed by 2302

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Thermodynamic and Exergy Analyses of Cooling, Power, and Energy Systems)

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