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Heat and Mass Transfer in Energy Systems

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "F: Electrical Engineering".

Deadline for manuscript submissions: closed (31 May 2019) | Viewed by 59005

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Prof. Dr. Alessandro Mauro

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Dipartimento di Ingegneria, Università degli Studi di Napoli “Parthenope”, Centro Direzionale, Isola C4, 80143 Napoli, Italy
Interests: energy systems; energy efficiency; geothermal energy; numerical modeling; heat transfer
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Nicola Massarotti

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Dipartimento di Ingegneria, Università degli Studi di Napoli “Parthenope”, Centro Direzionale, Isola C4, 80143 Napoli, Italy
Interests: heat and mass transport in porous media and free fluids; finite elements; innovative energy conversion systems; renewable energy sources; geothermal energy; fuel cells; heat and mass transfer in biomedical applications; waste to energy systems
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The purpose of this Special Issue is to collect interesting and original studies demonstrating the importance of properly taking into account heat and mass transfer phenomena in modern energy systems, in order to improve the conversion efficiency, design and operation techniques of these systems.

Given the importance of verification and validation issues for numerical codes, contributions dealing with both numerical approach and combined numerical-experimental approach are appreciated and invited in the Special Issue.

Papers that analyze aspects related to heat and mass transfer, useful for increasing the knowledge on energy systems, on the basis of one or more of the following topics are welcome in this Special Issue:

Energy sources and energy conversion systems
Technologies for renewable energy sources
Heating and air conditioning systems
Solar thermal and photovoltaic
Geothermal energy based systems
Waste to energy systems
Fuel cells
Heat exchangers/heat pipes
Heat and mass transfer in porous media
Heat and mass transfer in indoor environments
Internal flow and heat transfer
Multi-phase flows

Please notice that the above list is not exhaustive. Therefore, works focused on other research areas that are interesting for the Special Issue are also appreciated and invited.

Prof. Dr. Alessandro Mauro
Prof. Dr. Nicola Massarotti
Guest Editors

Manuscript Submission Information

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Keywords

Energy systems
Energy conversion
Geothermal energy
Waste to energy
Conduction
Convection
Radiation
Thermo fluid dynamics
Porous media
Numerical
Experimental
Validation
Verification

Published Papers (13 papers)

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13 pages, 3825 KiB

Open AccessArticle

Model Verification and Justification Study of Spirally Corrugated Pipes in a Ground-Air Heat Exchanger Application

by Kwang-Seob Lee, Eun-Chul Kang, Yu-Jin Kim and Euy-Joon Lee

Energies 2019, 12(21), 4047; https://doi.org/10.3390/en12214047 - 24 Oct 2019

Cited by 5 | Viewed by 2318

Abstract

Ground-air heat exchangers have become an important topic in recent years due to their contributions to the market growth of the ground source heat pump industry. This paper provides a comprehensive study and recommends suggestions on the selection process of a suitable pipe for an air-to-water heat pump (AWHP). Parametric studies including material, turbulent plate quantity, and pipe type were performed to identify an optimal pipe design for high-performance AWHP. Both numerical and experimental studies were carried out to validate current pipe models. Overall, there was good agreement between the numerical model and experimental results. It was determined that a spirally corrugated pipe exhibited excellent thermal power generation with little compromising pressure drop. Finally, a pipe selection example was demonstrated as a design guideline to size an optimal pipe for AWHP application. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Energy Systems)

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13 pages, 3999 KiB

Open AccessArticle

Sensitivity of Axial Velocity at the Air Gap Entrance to Flow Rate Distribution at Stator Radial Ventilation Ducts of Air-Cooled Turbo-Generator with Single-Channel Ventilation

by Yong Li, Weili Li and Ying Su

Energies 2019, 12(18), 3442; https://doi.org/10.3390/en12183442 - 06 Sep 2019

Cited by 1 | Viewed by 2523

Abstract

In the design and calculation of a 330 MW water-water-air cooling turbo-generator, it was found that the flow direction of the fluid in the local stator radial ventilation duct is opposite to the design direction. In order to study what physical quantities are associated with the formation of this unusual fluid flow phenomenon, in this paper, a 100 MW air-cooled turbo-generator with the same ventilation structure as the abovementioned models is selected as the research object. The distribution law and pressure of the fluid in the stator radial ventilation duct and axial flow velocity at the air gap entrance are obtained by the test method. After the calculation method is proved correct by experimental results, this calculation method is used to calculate the flow velocity distribution of the outlets of multiple radial ventilation ducts at various flow velocities at air gap inlets. The relationship between the flow distribution law of the stator ventilation ducts and the inlet velocity of the air gap is studied. The phenomenon of backflow of fluid in the radial ventilation duct of the stator is found, and then the influence of backflow on the temperature distribution of stator core and winding is studied. It is found that the flow phenomenon can cause local overheating of the stator core. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Energy Systems)

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22 pages, 8077 KiB

Open AccessArticle

Estimation of the Biot Number Using Genetic Algorithms: Application for the Drying Process

by Krzysztof Górnicki, Radosław Winiczenko and Agnieszka Kaleta

Energies 2019, 12(14), 2822; https://doi.org/10.3390/en12142822 - 22 Jul 2019

Cited by 22 | Viewed by 4510

Abstract

The Biot number informs researchers about the controlling mechanisms employed for heat or mass transfer during the considered process. The mass transfer coefficients (and heat transfer coefficients) are usually determined experimentally based on direct measurements of mass (heat) fluxes or correlation equations. This paper presents the method of Biot number estimation. For estimation of the Biot number in the drying process, the multi-objective genetic algorithm (MOGA) was developed. The simultaneous minimization of mean absolute error (MAE) and root mean square error (RMSE) and the maximization of the coefficient of determination R² between the drying model and experimental data were considered. The Biot number can be calculated from the following equations: Bi = 0.8193exp(−6.4951T⁻¹) (and moisture diffusion coefficient from D/s² = 0.00704exp(−2.54T⁻¹)) (RMSE = 0.0672, MAE = 0.0535, R² = 0.98) or Bi = 1/0.1746log(1193847T) (D/s² = 0.0075exp(−6T⁻¹)) (RMSE = 0.0757, MAE = 0.0604, R² = 0.98). The conducted validation gave good results. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Energy Systems)

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18 pages, 5529 KiB

Open AccessArticle

Ancillary Services Provided by Hybrid Residential Renewable Energy Systems through Thermal and Electrochemical Storage Systems

by Lorenzo Bartolucci, Stefano Cordiner, Vincenzo Mulone and Marina Santarelli

Energies 2019, 12(12), 2429; https://doi.org/10.3390/en12122429 - 24 Jun 2019

Cited by 15 | Viewed by 5759

Abstract

Energy Management System (EMS) optimal strategies have shown great potential to match the fluctuating energy production from renewables with an electric demand profile, which opens the way to a deeper penetration of renewable energy sources (RES) into the electric system. At a single building level, however, handling of different energy sources to fulfill both thermal and electric requirements is still a challenging task. The present work describes the potential of an EMS based on Model Predictive Control (MPC) strategies to both maximize the RES exploitation and serve as an ancillary service for the grid when a Heat Pump (HP) coupled with a Thermal Energy Storage (TES) is used in a residential Hybrid Renewable Energy System (HRES). Cost savings up to 30% as well as a reduction of the purchased energy unbalance with the grid (about 15%–20% depending on the season) have been achieved. Moreover, the thermal energy storage leads to a more efficient and reliable use of the Heat Pump by generally decreasing the load factor smoothing the power output. The proposed control strategy allows to have a more stable room temperature, with evident benefits also in terms of thermal comfort. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Energy Systems)

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13 pages, 1460 KiB

Open AccessArticle

Comprehensive Electric Arc Furnace Electric Energy Consumption Modeling: A Pilot Study

by Miha Kovačič, Klemen Stopar, Robert Vertnik and Božidar Šarler

Energies 2019, 12(11), 2142; https://doi.org/10.3390/en12112142 - 04 Jun 2019

Cited by 36 | Viewed by 10175

Abstract

The electric arc furnace operation at the Štore Steel company, one of the largest flat spring steel producers in Europe, consists of charging, melting, refining the chemical composition, adjusting the temperature, and tapping. Knowledge of the consumed energy within the individual electric arc operation steps is essential. The electric energy consumption during melting and refining was analyzed including the maintenance and technological delays. In modeling the electric energy consumption, 25 parameters were considered during melting (e.g., coke, dolomite, quantity), refining and tapping (e.g., injected oxygen, carbon, and limestone quantity) that were selected from 3248 consecutively produced batches in 2018. Two approaches were employed for the data analysis: linear regression and genetic programming model. The linear regression model was used in the first randomly generated generations of each of the 100 independent developed civilizations. More accurate models were subsequently obtained during the simulated evolution. The average relative deviation of the linear regression and the genetic programming model predictions from the experimental data were 3.60% and 3.31%, respectively. Both models were subsequently validated by using data from 278 batches produced in 2019, where the maintenance and the technological delays were below 20 minutes per batch. It was possible, based on the linear regression and the genetically developed model, to calculate that the average electric energy consumption could be reduced by up to 1.04% and 1.16%, respectively, in the case of maintenance and other technological delays. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Energy Systems)

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13 pages, 1539 KiB

Open AccessArticle

Analytical and Experimental Investigation of the Solar Chimney System

by Zygmunt Lipnicki, Marta Gortych, Anna Staszczuk, Tadeusz Kuczyński and Piotr Grabas

Energies 2019, 12(11), 2060; https://doi.org/10.3390/en12112060 - 29 May 2019

Cited by 6 | Viewed by 3944

Abstract

In this, paper the authors propose a new simplified method of solving the problem of air flow through a solar chimney system using a classical system of equations for the principles of conservation (momentum, mass, and energy), as well as a general solution to research the problem using similarity theory. The method presented in this paper allows one to design a solar chimney. The theoretical analysis was compared with experimental studies on existing solar towers. The experimental and theoretical studies were satisfactorily consistent. For clarity, the phenomenon of heat flow in the solar chimney was described using dimensionless numbers, such as the Reynolds, Grashof, Galileo, Biot, and Prandtl numbers. In the equations for the dimensionless geometric parameters, the ratios of the collector radius to the thickness gap, height, and chimney radius were used. The method used to test the system of equations allows us to analyse various solar collectors easily. In the scientific literature, there is a lack of a simple calculation method to use in engineering practice, suitable for each type of solar chimney independent of dimensions and construction parameters. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Energy Systems)

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20 pages, 3788 KiB

Open AccessArticle

Desiccant-Based Air Handling Unit Alternatively Equipped with Three Hygroscopic Materials and Driven by Solar Energy

by Piero Bareschino, Francesco Pepe, Carlo Roselli, Maurizio Sasso and Francesco Tariello

Energies 2019, 12(8), 1543; https://doi.org/10.3390/en12081543 - 24 Apr 2019

Cited by 11 | Viewed by 3806

Abstract

The energy demand for the air-conditioning of buildings has shown a very significant growth trend in the last two decades. In this paper three alternative hygroscopic materials for desiccant wheels are compared considering the operation of the air handling unit they are installed in. The analyses are performed by means of the TRNSYS 17^® software, simulating the plant with the desiccant wheel made of: silica-gel, i.e., the filling actually used in the experimental plant desiccant wheel of the University of Sannio Laboratory; MIL101@GO-6 (MILGO), a composite material, consisting of graphite oxide dispersed in a MIL101 metal organic framework structure; Campanian Ignimbrite, a naturally occurring tuff, rich in phillipsite and chabazite zeolites, widespread in the Campania region, in Southern Italy. The air-conditioning system analyzed serves a university classroom located in Benevento, and it is activated by the thermal energy of a solar field for which three surfaces are considered: about 20, 27 and 34 m². The results demonstrate that a primary energy saving of about 20%, 29%, 15% can be reached with silica-gel, MILGO and zeolite-rich tuff desiccant wheel based air handling units, respectively. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Energy Systems)

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24 pages, 10230 KiB

Open AccessArticle

An Object-Oriented R744 Two-Phase Ejector Reduced-Order Model for Dynamic Simulations

by Michal Haida, Rafal Fingas, Wojciech Szwajnoch, Jacek Smolka, Michal Palacz, Jakub Bodys and Andrzej J. Nowak

Energies 2019, 12(7), 1282; https://doi.org/10.3390/en12071282 - 03 Apr 2019

Cited by 6 | Viewed by 3797

Abstract

The object-oriented two-phase ejector hybrid reduced-order model (ROM) was developed for dynamic simulation of the R744 refrigeration system. OpenModelica software was used to evaluate the system’s performance. Moreover, the hybrid ROM results were compared to the results given by the non-dimensional and one-dimensional mathematical approaches of the R744 two-phase ejector. Accuracy of all three ejector models was defined through a validation procedure for the experimental results. Finally, the dynamic simulation of the hybrid ROM ejector model integrated with the R744 refrigeration system was presented based on the summer campaign at three different climate zones: Mediterranean, South American and South Asian. The hybrid ROM obtained the best prediction of ejector mass flow rates as compared with other ejector models under subcritical and transcritical operating conditions. The dynamic simulations of the R744 ejector-based system indicated the ejector efficiency variations and the best efficiency at the investigated climate zones. The coefficient of performance (COP) varied from 2.5 to 4.0 according to different ambient conditions. The pressure ratio of 1.15 allowed a more stabilised system during the test campaign with an ejector efficiency from 20% to over 30%. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Energy Systems)

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19 pages, 5864 KiB

Open AccessArticle

Design and Development of Innovative Protracted-Finned Counter Flow Heat Exchanger (PFCHE) for an Engine WHR and Its Impact on Exhaust Emissions

by Rajesh Ravi and Senthilkumar Pachamuthu

Energies 2018, 11(10), 2717; https://doi.org/10.3390/en11102717 - 11 Oct 2018

Cited by 31 | Viewed by 4937

Abstract

This article describes and evaluates an Organic Rankine Cycle (ORC) for waste heat recovery system both theoretically as well as experimentally. Based on the thermodynamic analysis of the exhaust gas temperature identified at different locations of the exhaust manifold of an engine, the double-pipe, internally–externally protruded, finned counter flow heat exchanger was innovatively designed and installed in diesel engine for exhaust waste heat recovery (WHR). The tests were conducted to find the performance of heat recovery system by varying the fin geometries of the heat exchanger. The effect of heat exchanger on emission parameters is investigated and presented in this work. The experimental results demonstrated that the amount of heat transfer rate, the effectiveness of heat exchange rand the brake thermal efficiency improved with an increase in length and number of the fins. A significant reduction was observed in all major emissions after the implementation of catalytic-coated, protracted finned counter flow heat exchanger. It also demonstrated the possibility of electric power production using steam turbo-electric-generator setup driven by the recovered exhaust heat energy. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Energy Systems)

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25 pages, 5849 KiB

Open AccessArticle

BFC-POD-ROM Aided Fast Thermal Scheme Determination for China’s Secondary Dong-Lin Crude Pipeline with Oils Batching Transportation

by Dongxu Han, Qing Yuan, Bo Yu, Danfu Cao and Gaoping Zhang

Energies 2018, 11(10), 2666; https://doi.org/10.3390/en11102666 - 07 Oct 2018

Cited by 1 | Viewed by 2586

Abstract

Since the transportation task of China’s Secondary Dong-Lin crude pipeline has been changed from Shengli oil to both Shengli and Oman oils, its transportation scheme had to be changed to “batch transportation”. To determine the details of batch transportation, large amounts of simulations should be performed, but massive simulation times could be costly (they can take hundreds of days with 10 computers) using the finite volume method (FVM). To reduce the intolerable time consumption, the present paper adopts a “body-fitted coordinate-based proper orthogonal decomposition reduced-order model” (BFC-POD-ROM) to obtain faster simulations. Compared with the FVM, the adopted method reduces the time cost of thermal simulations to 2.2 days from 264 days. Subsequently, the details of batch transportation are determined based on these simulations. The Dong-Lin crude oil pipeline has been safely operating for more than two years using the determined scheme. It is found that the field data are well predicted by the POD reduced-order model with an acceptable error in crude oil engineering. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Energy Systems)

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15 pages, 5642 KiB

Open AccessArticle

Visualization Study of Startup Modes and Operating States of a Flat Two-Phase Micro Thermosyphon

by Liangyu Wu, Yingying Chen, Suchen Wu, Mengchen Zhang, Weibo Yang and Fangping Tang

Energies 2018, 11(9), 2291; https://doi.org/10.3390/en11092291 - 30 Aug 2018

Cited by 5 | Viewed by 3294

Abstract

The flat two-phase thermosyphon has been recognized as a promising technique to realize uniform heat dissipation for high-heat-flux electronic devices. In this paper, a visualization experiment is designed and conducted to study the startup modes and operating states in a flat two-phase thermosyphon. The dynamic wall temperatures and gas–liquid interface evolution are observed and analyzed. From the results, the sudden startup and gradual startup modes and three quasi-steady operating states are identified. As the heat load increases, the continuous large-amplitude pulsation, alternate pulsation, and continuous small-amplitude pulsation states are experienced in sequence for the evaporator wall temperature. The alternate pulsation state can be divided into two types of alternate pulsation: lengthy single-large-amplitude-pulsation alternated with short multiple-small-amplitude-pulsation, and short single-large-amplitude-pulsation alternated with lengthy multiple-small-amplitude alternate pulsation state. During the continuous large-amplitude pulsation state, the bubbles were generated intermittently and the wall temperature fluctuated cyclically with a continuous large amplitude. In the alternate pulsation state, the duration of boiling became longer compared to the continuous large-amplitude pulsation state, and the wall temperature of the evaporator section exhibited small fluctuations. In addition, there was no large-amplitude wall temperature pulsation in the continuous small-amplitude pulsation state, and the boiling occurred continuously. The thermal performance of the alternate pulsation state in a flat two-phase thermosyphon is inferior to the continuous small-amplitude pulsation state but superior to the continuous large-amplitude pulsation state. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Energy Systems)

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16 pages, 6940 KiB

Open AccessArticle

Experimental Study of a Bubble Mode Absorption with an Inner Vapor Distributor in a Plate Heat Exchanger-Type Absorber with NH₃-LiNO₃

by Jorge J. Chan, Roberto Best, Jesús Cerezo, Mario A. Barrera and Francisco R. Lezama

Energies 2018, 11(8), 2137; https://doi.org/10.3390/en11082137 - 16 Aug 2018

Cited by 12 | Viewed by 4508

Abstract

Absorption systems are a sustainable solution as solar driven air conditioning devices in places with warm climatic conditions, however, the reliability of these systems must be improved. The absorbing component has a significant effect on the cycle performance, as this process is complex and needs efficient heat exchangers. This paper presents an experimental study of a bubble mode absorption in a plate heat exchanger (PHE)-type absorber with NH₃-LiNO₃ using a vapor distributor in order to increase the mass transfer at solar cooling operating conditions. The vapor distributor had a diameter of 0.005 m with five perforations distributed uniformly along the tube. Experiments were carried out using a corrugated plate heat exchanger model NB51, with three channels, where the ammonia vapor was injected in a bubble mode into the solution in the central channel. The range of solution concentrations and mass flow rates of the dilute solution were from 35 to 50% weight and 11.69 to 35.46 × 10⁻³ kg·s⁻¹, respectively. The mass flow rate of ammonia vapor was from 0.79 to 4.92 × 10⁻³ kg·s⁻¹ and the mass flow rate of cooling water was fixed at 0.31 kg·s⁻¹. The results achieved for the absorbed flux was 0.015 to 0.024 kg m⁻²·s⁻¹ and the values obtained for the mass transfer coefficient were in the order of 0.036 to 0.059 m·s⁻¹. The solution heat transfer coefficient values were obtained from 0.9 to 1.8 kW·m⁻²·K⁻¹ under transition conditions and from 0.96 to 3.16 kW·m⁻²·K⁻¹ at turbulent conditions. Nusselt number correlations were obtained based on experimental data during the absorption process with the NH₃-LiNO₃ working pair. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Energy Systems)

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11 pages, 1996 KiB

Open AccessTechnical Note

Thermal Conductivity of Korean Compacted Bentonite Buffer Materials for a Nuclear Waste Repository

by Seok Yoon, WanHyoung Cho, Changsoo Lee and Geon-Young Kim

Energies 2018, 11(9), 2269; https://doi.org/10.3390/en11092269 - 29 Aug 2018

Cited by 29 | Viewed by 4835

Abstract

Engineered barrier system (EBS) has been proposed for the disposal of high-level waste (HLW). An EBS is composed of a disposal canister with spent fuel, a buffer material, backfill material, and a near field rock mass. The buffer material is especially essential to guarantee the safe disposal of HLW, and plays the very important role of protecting the waste and canister against any external mechanical impact. The buffer material should also possess high thermal conductivity, to release as much decay heat as possible from the spent fuel. Its thermal conductivity is a crucial property since it determines the temperature retained from the decay heat of the spent fuel. Many studies have investigated the thermal conductivity of bentonite buffer materials and many types of soils. However, there has been little research or overall evaluation of the thermal conductivity of Korean Ca-type bentonite buffer materials. This paper investigated and analyzed the thermal conductivity of Korean Ca-type bentonite buffer materials produced in Gyeongju, and compared the results with various characteristics of Na-type bentonites, such as MX80 and Kunigel. Additionally, this paper suggests various predictive models to predict the thermal conductivity of Korean bentonite buffer materials considering various influential independent variables, and compared these with results for MX80 and Kunigel. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Energy Systems)

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