Topic Editors

Dipartimento di Ingegneria Industriale e Scienze Matematiche (DIISM), Universita' Politecnica delle Marche, 60131 Ancona, Italy
LTEF-Laboratory for Thermodynamics and Energy Efficiency, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split, 21000 Split, Croatia
Department of Mechanical Engineering, University of Aveiro, 3810-193 Aveiro, Portugal
Dr. Alice Mugnini
Dipartimento di Ingegneria Industriale e Scienze Matematiche (DIISM), Universita' Politecnica delle Marche, 60131 Ancona, Italy

Heat Exchanger Design and Heat Pump Efficiency

Abstract submission deadline
closed (31 January 2024)
Manuscript submission deadline
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Topic Information

Dear Colleagues,

Maximizing energy efficiency in air conditioning technologies is one of the most promising areas for limiting energy consumption. Due to the increasing diffusion of heat pumps, the identification of solutions to increase their efficiency and to reduce the environmental impact represents very important areas in which to concentrate research efforts. In particular, a fundamental role for the performance of heat pumps is attributed to heat exchangers, used as a condenser or evaporator. Particularly relevant is research on innovative solutions to obtain more efficient, compact, and economical heat exchangers. It is especially relevant for use of new refrigerants with a reduced GWP but with flammability issues. In addition, it is interesting to evaluate solutions to improve the operating performance of heat pumps by means of improved system integration.

This Topic will include articles on, but not limited to, the following areas:

  • Energy-efficient solutions;
  • Heat exchanger design;
  • Optimal design and optimal management of heat pumps.

Prof. Dr. Fabio Polonara
Prof. Dr. Sandro Nizetic
Prof. Dr. Vítor António Ferreira Da Costa
Dr. Alice Mugnini
Topic Editors

Keywords

  • heat exchanger design
  • heat pumps
  • energy efficiency
  • optimal management
  • optimal design

Participating Journals

Journal Name Impact Factor CiteScore Launched Year First Decision (median) APC
Applied Sciences
applsci
2.7 4.5 2011 16.9 Days CHF 2400
Energies
energies
3.2 5.5 2008 16.1 Days CHF 2600
Entropy
entropy
2.7 4.7 1999 20.8 Days CHF 2600
Thermo
thermo
- - 2021 23.2 Days CHF 1000

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Published Papers (19 papers)

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18 pages, 7335 KiB  
Article
Thermal-Hydraulic Modeling of Oil-Immersed Motor Pump
by Junqiang Shi, Ziyang Li, Jingcheng Gao, Dongjing Chen, Xiaotao Li, Ying Li, Jin Zhang and Xiangdong Kong
Appl. Sci. 2023, 13(16), 9452; https://doi.org/10.3390/app13169452 - 21 Aug 2023
Viewed by 704
Abstract
The integrated design of the motor and axial piston pump eliminates the coupling structure, resulting in a compact and lightweight motor-pump structure. The challenge of motors overheating has always been a major concern. To address this issue, the hydraulic oil throughout the motor [...] Read more.
The integrated design of the motor and axial piston pump eliminates the coupling structure, resulting in a compact and lightweight motor-pump structure. The challenge of motors overheating has always been a major concern. To address this issue, the hydraulic oil throughout the motor pump is utilized for cooling the high-speed motor, effectively improving the power density and heat dissipation capability of the hydraulic power unit. This integrated design approach has successfully resolved the significant issue of overheating motors, leading to enhanced performance of the hydraulic power unit. To address this concern, the entire motor pump’s oil is utilized to cool the high-speed motor. Consequently, the thermodynamic prediction of high-speed motor pumps has become increasingly important. In this study, the impact of motor heat generation on hydrodynamics is analyzed, and the heat transfer of the motor pump is investigated using the control volume method. Furthermore, thermodynamic models of hysteresis loss, eddy current loss, alternating current loss, churning loss, and throttling loss are established for the oil-immersed motor pump. The change in oil viscosity is also considered. The instantaneous temperature change rule of the oil within the oil-immersed motor pump is derived. Additionally, the influence of various working conditions such as pressure and speed on the temperature of the motor pump’s key node is examined. The experimental results indicate the accuracy of the thermodynamic calculation, and the significant effect of motor loss on the leakage temperature. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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36 pages, 3294 KiB  
Review
Increasing Thermal Efficiency: Methods, Case Studies, and Integration of Heat Exchangers with Renewable Energy Sources and Heat Pumps for Desalination
by Konstantin Osintsev, Sergei Aliukov, Sulpan Kuskarbekova, Tatyana Tarasova, Aleksandr Karelin, Vladimir Konchakov and Olga Kornyakova
Energies 2023, 16(13), 4930; https://doi.org/10.3390/en16134930 - 25 Jun 2023
Cited by 2 | Viewed by 1563
Abstract
The article presents an overview of modern analytical methods and experimental studies on the use of heat exchangers as part of different schemes, as well as technologies that increase the efficiency of heat exchangers using renewable energy sources. The main types of heat [...] Read more.
The article presents an overview of modern analytical methods and experimental studies on the use of heat exchangers as part of different schemes, as well as technologies that increase the efficiency of heat exchangers using renewable energy sources. The main types of heat exchangers, and the principles of their operation, are considered. In addition, modern technologies for increasing the efficiency of heat exchangers through design are described. The practical experience of using plate heat exchangers in industry has been studied. An overview of the software development that is used in the design and optimization of heat exchange devices, as well as for the improvement of their energy efficiency, is presented. The presented mathematical models can be used for software that is applicable both to individual segments of plates of heat exchangers and heat exchangers in general, taking into account the dependence of the installation of the entire circuit on environmental parameters and location. In conclusion, recommendations are given for further research directions in the field of using heat exchangers with the inclusion of renewable energy sources. The technique of an energy technology complex, including a heat pump, a photovoltaic panel, and a desalination plant, is presented. The methodology is built around the basic design and energy balance of the complex, and it is also considered from the point of view of the exergetic balance. This allows for the use of additional components, such as a turbo expander for the implementation of the organic Rankine cycle, a wind turbine, and a solar concentrator. This scientific approach can become unified for the design and operation of an energy technology complex. In addition, an exergetic calculation method is presented for a thermal desalination plant operating as part of an energy technology complex with renewable energy sources. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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16 pages, 3473 KiB  
Article
Scientific Approaches to Solving the Problem of Joint Processes of Bubble Boiling of Refrigerant and Its Movement in a Heat Pump Heat Exchanger
by Konstantin Osintsev, Sergei Aliukov, Anton Kovalev, Yaroslav Bolkov, Sulpan Kuskarbekova and Alyona Olinichenko
Energies 2023, 16(11), 4405; https://doi.org/10.3390/en16114405 - 30 May 2023
Cited by 2 | Viewed by 983
Abstract
The joint processes of bubble boiling and refrigerant movement in heat pump tubes are considered. A coil located on the back side of the photovoltaic panel (PVP) is used as an additional heating surface. A mathematical model of the theoretical determination of the [...] Read more.
The joint processes of bubble boiling and refrigerant movement in heat pump tubes are considered. A coil located on the back side of the photovoltaic panel (PVP) is used as an additional heating surface. A mathematical model of the theoretical determination of the temperature on the front surface of the PVP cooled by freon in the coil from the back side has been created. A feature of the numerical simulation of bubble boiling of refrigerant in a coil was the insufficiently detailed study of the process and the lack of references to the results obtained in earlier work. The authors have clarified the boundary conditions and assumptions for numerical simulation of the bubble boiling process of refrigerant R407C. The results were compared with the theoretically found values, and later used in the design of an energy complex consisting of a heat pump and a photovoltaic panel. The mathematical model of theoretical calculation of the PVP temperature and the methodology for constructing a numerical model of bubble boiling of refrigerant as part of the methodology for designing energy technology complexes based on the authors’ plan to present a unified methodology for energy technology complexes for desalination of seawater based on other types of renewable energy sources. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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24 pages, 1944 KiB  
Article
Carnot Battery Based on Brayton Supercritical CO2 Thermal Machines Using Concentrated Solar Thermal Energy as a Low-Temperature Source
by José Ignacio Linares, Arturo Martín-Colino, Eva Arenas, María José Montes, Alexis Cantizano and José Rubén Pérez-Domínguez
Energies 2023, 16(9), 3871; https://doi.org/10.3390/en16093871 - 02 May 2023
Cited by 5 | Viewed by 3204
Abstract
Carnot batteries store surplus power as heat. They consist of a heat pump, which upgrades a low-temperature thermal energy storage, a high-temperature storage system for the upgraded thermal energy, and a heat engine that converts the stored high-temperature thermal energy into power. A [...] Read more.
Carnot batteries store surplus power as heat. They consist of a heat pump, which upgrades a low-temperature thermal energy storage, a high-temperature storage system for the upgraded thermal energy, and a heat engine that converts the stored high-temperature thermal energy into power. A Carnot battery is proposed based on supercritical CO2 Brayton thermodynamic cycles. The low-temperature storage is a two-tank molten salt system at 380 °C/290 °C fed by a field of parabolic trough collectors. The high-temperature storage consists of another two-tank molten salt system at 589 °C/405 °C. Printed circuit heat exchangers would be required to withstand the high pressure of the cycles, but shell and tube heat exchangers are proposed instead to avoid clogging issues with molten salts. The conventional allocation of high-temperature molten salt heat exchangers is then modified. Using solar energy to enhance the low-temperature thermal source allowed a round-trip efficiency of 1.15 (COP of 2.46 and heat engine efficiency of 46.5%), thus increasing the stored power. The basic configuration has a levelised cost of storage of USD 376/MWh while replacing the shell and tube heat exchangers with hybrid printed circuit heat exchangers is expected to lower the cost to USD 188/MWh. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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21 pages, 22810 KiB  
Article
A Dynamic Heat Pump Model for Indoor Climate Control of a Broiler House
by Dimitrios Tyris, Apostolos Gkountas, Panteleimon Bakalis, Panagiotis Panagakis and Dimitris Manolakos
Energies 2023, 16(6), 2770; https://doi.org/10.3390/en16062770 - 16 Mar 2023
Cited by 2 | Viewed by 1470
Abstract
Environment control systems in broiler houses utilize non-renewable electricity and fuels as energy sources, contributing to the increase in greenhouse gases, while not providing optimal conditions. The heat pump (HP) is an energy-efficient technology that can continuously regulate the indoor temperature and relative [...] Read more.
Environment control systems in broiler houses utilize non-renewable electricity and fuels as energy sources, contributing to the increase in greenhouse gases, while not providing optimal conditions. The heat pump (HP) is an energy-efficient technology that can continuously regulate the indoor temperature and relative humidity by combining different operation modes (heating, cooling, and dehumidifying). The current study presents an analytical numerical model developed in Simulink, capable of simulating the thermal loads of a broiler house and the dynamic operation of three heat pumps to cover its needs. Outdoor climatic conditions and broilers’ heat production are used as inputs, while all the heat exchange mechanisms with the external environment are considered. The study investigates the energy use and performance of each HP mode under different environmental conditions. A total of 7 different production periods (PPs) are simulated for a 10,000-broiler house in northern Greece, showing total energy consumption of 18.5 kWh/m2, 43.4 kWh/m2, and 58.7 kWh/m2 for heating, cooling, and dehumidifying, respectively. The seasonal coefficient of performance (SCOP) reaches above 3.1 and 4.8 for heating and dehumidifying, respectively, while the seasonal energy efficiency ratio (SEER) for cooling is above 3.7. Finally, focusing on the two warmer periods, a comparison between cooling with and without evaporative pads was performed, showing similar energy consumption. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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21 pages, 15000 KiB  
Review
A Review of the Performance Improvement Methods of Phase Change Materials: Application for the Heat Pump Heating System
by Cong Zhou, Yizhen Li, Fenghao Wang, Zeyuan Wang, Qing Xia, Yuping Zhang, Jun Liu, Boyang Liu and Wanlong Cai
Energies 2023, 16(6), 2676; https://doi.org/10.3390/en16062676 - 13 Mar 2023
Cited by 1 | Viewed by 1771
Abstract
With the development of the economy and society, energy problems have become a great concern. The heat pump-coupled thermal energy storage (TES) system is a potential form of building heating, which can improve the stability of the grid and promote the consumption of [...] Read more.
With the development of the economy and society, energy problems have become a great concern. The heat pump-coupled thermal energy storage (TES) system is a potential form of building heating, which can improve the stability of the grid and promote the consumption of renewable energy. Phase change materials (PCMs) are widely used in the field of building heating, but there are still some problems such as unsatisfactory melting points, low thermal conductivity, phase separation, and supercooling, which limit the application of PCMs in heat pump heating systems. Therefore, it is very important to improve PCMs by a performance improvement method. This work first summarizes the classification, advantages and disadvantages of PCMs, and introduces the connection between PCMs and heat pumps. Then, a detailed summary of PCMs applied in heat pump heating systems is presented, and a comprehensive review of the performance improvement methods for PCMs, which include additives, encapsulation, and eutectic compounds, is discussed. Finally, the existing problems, solutions, and future research directions are proposed. The emphasis of the research is to clarify the influence of PCMs on heat pump performance and the effect of different performance improvement methods on PCMs, and to illustrate the future development direction for PCMs in heat pump heating technologies, including the matching of heat pumps and PCMs, multi-standard decision methods and advanced control strategies. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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19 pages, 944 KiB  
Article
Numerical Investigation of the Long-Term Load Shifting Behaviors within the Borehole Heat Exchanger Array System
by Haijiang Zou, Siyu Guo, Ruifeng Wang, Fenghao Wang, Zhenxing Shen and Wanlong Cai
Energies 2023, 16(5), 2497; https://doi.org/10.3390/en16052497 - 06 Mar 2023
Viewed by 1247
Abstract
In the process of development and utilization of a large-scale borehole heat exchanger (BHE) array system, the phenomenon of load shifting within BHE array can be observed. In this paper, OpenGeoSys software coupled with TESPy toolkit is used to establish a comprehensive numerical [...] Read more.
In the process of development and utilization of a large-scale borehole heat exchanger (BHE) array system, the phenomenon of load shifting within BHE array can be observed. In this paper, OpenGeoSys software coupled with TESPy toolkit is used to establish a comprehensive numerical model of BHE system (without depicting the heat pump part), and the behaviors of load shifting between BHEs with different design parameters are studied. The results show that the outlet temperature of single BHE and BHE array is generally rising, and the soil temperature around the BHE has accumulated unbalanced heat. The soil temperature near the BHEs array fluctuates more obviously than the single BHE system, and the distribution is uneven. At the end of the 15th year, the soil temperature near the center BHE increased by 2 °C compared with the initial soil temperature, which was more favorable in winter, but was not conducive to the performance improvement in summer. Further analysis by changing the inter-borehole spacing shows that with the increase of the inter-borehole spacing, the load shifting behaviors are gradually weakened, and the maximum shifted load of the central BHE is linear with the change of the inter-borehole spacing. After changing the layout methods, we observe that the more intensive the layout is, the more load shifting behavior is, and the unbalanced rate of soil temperature distribution around the linear layout is lower than other layouts. With the increase in the number of BHEs, the load shifting behaviors are further enhanced. By analyzing the proportion of shifted load amount relative to the average value, it is found that the system will take a longer time to reach heat balance with the increase of BHEs’ number. A shutdown of part of BHEs for a certain period of time will help to improve the long-term operational efficiency of the large-scale shallow ground source heat pump (GSHP) system. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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14 pages, 1883 KiB  
Article
Role of Non-Adiabatic Capillary Tube in Water Cooler Performance
by Lea Di Donato, Alice Mugnini, Fabio Polonara and Alessia Arteconi
Energies 2023, 16(3), 1322; https://doi.org/10.3390/en16031322 - 26 Jan 2023
Viewed by 1444
Abstract
In this paper, a numerical model of a capillary tube is developed. The considered expansion device is placed against the suction line at the inlet of the compressor. Wrapping the capillary tube around the suction line allows heat to be recovered by superheating [...] Read more.
In this paper, a numerical model of a capillary tube is developed. The considered expansion device is placed against the suction line at the inlet of the compressor. Wrapping the capillary tube around the suction line allows heat to be recovered by superheating the refrigerant leaving the evaporator. This increases the degree to which the fluid is superheated, preventing liquid droplets from entering the compressor and causing damage. The open-source software PYTHON is used for modelling the non adiabatic capillary tube, and the results are validated by comparing them with experimental tests. This study demonstrates that an accurate contact of the capillary tube with the suction line affects the superheating of the compressor inlet fluid by increasing its temperature by up to 5 degrees and produces an increase in COP of 3–4%. On the other hand, the length of the capillary tube affects the flow rate of the refrigerant circulating in the cycle; in particular, it is noted that a 300% increase in the capillary tube length leads to a decrease in the refrigerant flow rate of up to 50–60%. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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17 pages, 2359 KiB  
Article
Advanced Exergy Analysis of Ultra-Low GWP Reversible Heat Pumps for Residential Applications
by Volodymyr Voloshchuk, Paride Gullo and Eugene Nikiforovich
Energies 2023, 16(2), 703; https://doi.org/10.3390/en16020703 - 07 Jan 2023
Viewed by 1336
Abstract
Exergy-based methods provide engineers with the best information with respect to options for improving the overall thermodynamic efficiency of an energy conversion system. This paper presents the results of an advanced exergy analysis of an air-to-water reversible heat pump whose performance was analyzed [...] Read more.
Exergy-based methods provide engineers with the best information with respect to options for improving the overall thermodynamic efficiency of an energy conversion system. This paper presents the results of an advanced exergy analysis of an air-to-water reversible heat pump whose performance was analyzed with respect to different working fluids. Environmentally deleterious refrigerants, i.e., R410A and R134a (baselines), and their eco-friendly replacements (R290, R152a, R1234ze(E), and R1234yf) were selected. The evaluations were conducted under the same operating conditions (i.e., with the same cooling and heating demands and outdoor temperatures). Based on conventional exergy analysis, it was determined that different priorities should be given for the thermodynamic improvement of the components according to which heating and cooling modes of the system are in use. Therefore, integrated parameters, i.e., the annual values of exergy destruction, were applied for further analysis. The results obtained showed that the heat pump using R410A provided the largest degree of annual exergy destruction estimated on the basis of conventional exergy analysis (5913 kWh), whereas the heat pump using R290 offered the lowest one (4522 kWh). The annual exergy destruction of the R410A cycle with only unavoidable irreversibilities could be decreased by 50%. In this case, compared to R410A and R134a, R152a and R290 provided lower values of the total annual unavoidable aspects of exergy destruction. Considering technological limitations, when removing all the avoidable irreversibilities within the air exchanger, the largest decrease in the total exergy destruction within the system could be reached. The results obtained from the analysis of the removable irreversibilities showed that the mutual interactions between the compressor, evaporator, and condenser were weak. Finally, it was concluded that, from a thermodynamic point of view, the adoption of R152a and R290 in reversible air-to-water heat pumps as replacements for R410A and R134a is advisable. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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15 pages, 797 KiB  
Article
Air/Water Heat Pumps in Existing Heating and Hot Water Systems for Better Urban Air Quality and Primary Energy Savings: Scenarios of Two Italian Cities
by Alberta Carella, Luca Del Ferraro and Annunziata D’Orazio
Energies 2023, 16(1), 377; https://doi.org/10.3390/en16010377 - 29 Dec 2022
Cited by 2 | Viewed by 1392
Abstract
In a previous work, a significant contribution to urban air pollution, related to fuel-fired heating systems, was recorded. Thus, the replacement of existing boilers for space heating and domestic hot water (DHW) production systems with high-temperature air/water heat pumps (which can operate with [...] Read more.
In a previous work, a significant contribution to urban air pollution, related to fuel-fired heating systems, was recorded. Thus, the replacement of existing boilers for space heating and domestic hot water (DHW) production systems with high-temperature air/water heat pumps (which can operate with radiators, the most common terminals in the existing building stock), is proposed for the improvement of the urban air quality. Scenarios of substitution within the entire residential building stock of two Italian cities, Milan and Salerno, belonging to different climate zones and with their own thermophysical characteristics, were analyzed. For each of them, the consequences of the replacement intervention on emission reduction, primary energy savings and lower CO2 production were evaluated. The results show that reduction of primary energy consumption, evaluated at design outdoor temperature and for the present generation mix, varied between 34% and 54% in Milan and between 43% and 60% in Salerno, for two values of renewable fraction in electricity generation. The reduction of CO2 production was in the range 30–52% in Milan and 39–58% in Salerno, respectively. The only unfavorable case occurred for Milan for a completely non-renewable electricity generation scenario. The replacement intervention, which implies a significant decrease of emissions of pollutants in urban areas, is unobtrusive to citizens, since the heat pumps (HPs) are coupled with current radiators, without the internal distribution system being modified. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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25 pages, 8451 KiB  
Article
Experimental and Theoretical Investigations of a Ground Source Heat Pump System for Water and Space Heating Applications in Kazakhstan
by Yelnar Yerdesh, Tangnur Amanzholov, Abdurashid Aliuly, Abzal Seitov, Amankeldy Toleukhanov, Mohanraj Murugesan, Olivier Botella, Michel Feidt, Hua Sheng Wang, Alexandr Tsoy and Yerzhan Belyayev
Energies 2022, 15(22), 8336; https://doi.org/10.3390/en15228336 - 08 Nov 2022
Cited by 3 | Viewed by 1650
Abstract
The ground source heat pump heating system is considered as one of the best solutions for the transition towards green heating under the continental climate conditions like Kazakhstan. In this paper, experimental and theoretical investigations were carried out to develop a ground source [...] Read more.
The ground source heat pump heating system is considered as one of the best solutions for the transition towards green heating under the continental climate conditions like Kazakhstan. In this paper, experimental and theoretical investigations were carried out to develop a ground source heat pump-based heating system under the weather conditions in Kazakhstan and to evaluate its thermodynamic performance. The water-to-water heat pump heating system, integrated with a ground source heat exchanger and used refrigerant R134a, was designed to provide hot water to meet the requirements for space heating. The predicted values of the coefficient of performance and the experimental results were found to be in good agreement within 6.2%. The thermodynamic performance of the system was also assessed using various environment-friendly refrigerants, such as R152a, R450A, R513A, R1234yf and R1234ze, as potential replacements for R134a. Although R152a is found to be a good alternative for R134a in terms of coefficient of performance and total equivalent warming impact, its flammability hinders its application. The heating system using refrigerants R450A, R513A, R1234yf and R1234ze shows 2–3% lower coefficient of performance than that of R134a. The highest exergy destruction is found to be attributed to the compressor, followed by the expansion valve, evaporator, and condenser. Considering their low flammability and low environmental impact, R450A, R513A, R1234yf and R1234ze are identified as valuable replacements for R134a. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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20 pages, 5885 KiB  
Article
Dynamic Induction Heating Temperature Field Analysis of Spiral Bevel Gears
by Yin Zhang, Hui Zhang, Yixiong Yan and Pengfei Zhu
Appl. Sci. 2022, 12(19), 10018; https://doi.org/10.3390/app121910018 - 06 Oct 2022
Viewed by 1487
Abstract
Combining tooth surface induction heating and shot peening is an efficient method to improve tooth surface performance. Reasonable designs of the induction coil structure and parameters are essential for achieving uniform and efficient tooth surface heating. In this work, to precisely control the [...] Read more.
Combining tooth surface induction heating and shot peening is an efficient method to improve tooth surface performance. Reasonable designs of the induction coil structure and parameters are essential for achieving uniform and efficient tooth surface heating. In this work, to precisely control the tooth surface temperature field and improve the heat uniformity across the tooth surface, a transverse coil (TC) and a longitudinal coil (LC) were designed, and the gear was set to rotate at a constant speed of 20 r/min, dividing the tooth surface is into a shot-peening area and heating area. Further, dynamic numerical simulations were performed using COMSOL Multiphysics in combination with the uniform rotation of gears to investigate the effect of the coil structure on the temperature field of the outer surface of gears. The results of the analyses combining the effects of different electrical parameters revealed that the gear surface temperature under LC heating was more uniformly distributed in the axial and circumferential directions, the tooth surface temperature fluctuations were smaller, the temperature difference between the root and top of the tooth was smaller, an coil heating was more efficient. Thus, the LC was deemed suitable for use as the spiral bevel gear induction heating coil. Finally, heating experiments were conducted using the LC to validate the simulation model. The results show that the use of LC heating can achieve the research goals of uniform temperature field distribution on the tooth surface and efficient temperature rise, providing the prerequisite for shot peening. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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23 pages, 3316 KiB  
Article
Mathematical Model of Air Dryer Heat Pump Exchangers
by Tomasz Mołczan and Piotr Cyklis
Energies 2022, 15(19), 7092; https://doi.org/10.3390/en15197092 - 27 Sep 2022
Cited by 3 | Viewed by 1842
Abstract
This paper presents a mathematical model of heat pump exchangers and their thermal interaction with a fan for an air dryer. The calculation algorithm developed for the finned heat exchangers is based on the ε-NTU method, allowing the determination of air side and [...] Read more.
This paper presents a mathematical model of heat pump exchangers and their thermal interaction with a fan for an air dryer. The calculation algorithm developed for the finned heat exchangers is based on the ε-NTU method, allowing the determination of air side and refrigerant side heat transfer coefficients, evaporator and condenser heat capacity and air parameters at the dehumidifier outlet with known exchanger geometries, initial air parameters and mass flow rate. The model was verified on an industrial dehumidifier test bench. This enabled the heat transfer coefficients for the exchanger to be calculated as a function of the speed and, therefore, the power of the fan’s drive motor. An increase in fan performance on the one hand results in an increase in the heat transfer rate, but, on the other hand, it causes an increase in the total energy consumption of the motor. Thus, while it causes an increase in drying capacity, it also causes an increase in the energy consumption of the dehumidifier. In order to optimise the unit in terms of energy consumption, it is therefore necessary to determine a function that relates the amount of heat exchanged to the efficiency of the fan. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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21 pages, 12792 KiB  
Article
Comparative Study of the Thermal and Hydraulic Performance of Supercritical CO2 and Water in Microchannels Based on Entropy Generation
by Yi Tu and Yu Zeng
Entropy 2022, 24(9), 1312; https://doi.org/10.3390/e24091312 - 16 Sep 2022
Cited by 1 | Viewed by 1471
Abstract
The excellent thermophysical properties of supercritical CO2 (sCO2) close to the pseudocritical point make it possible to replace water as the coolant of microchannels in application of a high heat flux radiator. The computational fluid dynamics (CFD) method verified by [...] Read more.
The excellent thermophysical properties of supercritical CO2 (sCO2) close to the pseudocritical point make it possible to replace water as the coolant of microchannels in application of a high heat flux radiator. The computational fluid dynamics (CFD) method verified by experimental data is used to make a comparison of the thermal hydraulic behavior in CO2-cooled and of water-cooled microchannels. The operation conditions of the CO2-based cooling cases cover the pseudocritical point (with the inlet temperature range of 306~320 K and the working pressure of 8 MPa), and the water-based cooling case has an inlet temperature of 308 K at the working pressure of 0.1 MPa. The channel types include the straight and zigzag microchannels with 90°, 120°, and 150° bending angles, respectively. The analysis result shows that, only when the state of CO2 is close to the pseudocritical point, the sCO2-cooled microchannel is of a higher average heat convection coefficient and a lower average temperature of the heated surface compared to the water-cooled microchannel. The entropy generation rate of the sCO2-cooled microchannel can reach 0.58~0.69 times that of the entropy generation rate for the water-cooled microchannel. Adopting the zigzag structure can enhance the heat transfer, but it does not improve the comprehensive performance represented by the entropy generation rate in the sCO2-cooled microchannel. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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23 pages, 839 KiB  
Article
On the Computational Study of a Fully Wetted Longitudinal Porous Heat Exchanger Using a Machine Learning Approach
by Hosam Alhakami, Naveed Ahmad Khan, Muhammad Sulaiman, Wajdi Alhakami and Abdullah Baz
Entropy 2022, 24(9), 1280; https://doi.org/10.3390/e24091280 - 11 Sep 2022
Cited by 5 | Viewed by 1923
Abstract
The present study concerns the modeling of the thermal behavior of a porous longitudinal fin under fully wetted conditions with linear, quadratic, and exponential thermal conductivities surrounded by environments that are convective, conductive, and radiative. Porous fins are widely used in various engineering [...] Read more.
The present study concerns the modeling of the thermal behavior of a porous longitudinal fin under fully wetted conditions with linear, quadratic, and exponential thermal conductivities surrounded by environments that are convective, conductive, and radiative. Porous fins are widely used in various engineering and everyday life applications. The Darcy model was used to formulate the governing non-linear singular differential equation for the heat transfer phenomenon in the fin. The universal approximation power of multilayer perceptron artificial neural networks (ANN) was applied to establish a model of approximate solutions for the singular non-linear boundary value problem. The optimization strategy of a sports-inspired meta-heuristic paradigm, the Tiki-Taka algorithm (TTA) with sequential quadratic programming (SQP), was utilized to determine the thermal performance and the effective use of fins for diverse values of physical parameters, such as parameter for the moist porous medium, dimensionless ambient temperature, radiation coefficient, power index, in-homogeneity index, convection coefficient, and dimensionless temperature. The results of the designed ANN-TTA-SQP algorithm were validated by comparison with state-of-the-art techniques, including the whale optimization algorithm (WOA), cuckoo search algorithm (CSA), grey wolf optimization (GWO) algorithm, particle swarm optimization (PSO) algorithm, and machine learning algorithms. The percentage of absolute errors and the mean square error in the solutions of the proposed technique were found to lie between 104 to 105 and 108 to 1010, respectively. A comprehensive study of graphs, statistics of the solutions, and errors demonstrated that the proposed scheme’s results were accurate, stable, and reliable. It was concluded that the pace at which heat is transferred from the surface of the fin to the surrounding environment increases in proportion to the degree to which the wet porosity parameter is increased. At the same time, inverse behavior was observed for increase in the power index. The results obtained may support the structural design of thermally effective cooling methods for various electronic consumer devices. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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16 pages, 4252 KiB  
Article
A Heat Exchanger with Water Vapor Condensation on the External Surface of a Vertical Pipe
by Petr Kracík, Filip Toman, Jiří Pospíšil and Stanislav Kraml
Energies 2022, 15(15), 5636; https://doi.org/10.3390/en15155636 - 03 Aug 2022
Cited by 1 | Viewed by 1722
Abstract
The paper is concerned with water vapor condensation on vertical pipes. The vertical position of pipes in a condenser is not discussed very often. Its application has a number of particularities in terms of the numerical determination of heat transfer. In the first [...] Read more.
The paper is concerned with water vapor condensation on vertical pipes. The vertical position of pipes in a condenser is not discussed very often. Its application has a number of particularities in terms of the numerical determination of heat transfer. In the first stage of this paper, the authors focus on the experimental identification of heat transfer during vapor condensation on vertical pipes with a diameter of 14.0 × 1.0 mm. The pipes are placed in a narrow channel and the steam flows around them in a perpendicular direction. Two channel widths were tested, i.e., 20.0 and 24.0 mm. In the second stage, numerical modelling (CFD) is used for a detailed identification of the vapor velocity fields near the pipes. In the third stage, the results of the experimental measurements and numerical modelling are compared with data published by various authors. There are studies in the literature dealing with axial flow around vertical pipes; however, the associated results are based on conditions which are distinct from those applied in our study. The outcome of this paper is the specification of the heat transfer coefficient and the calculation formulas precisely describing the studied condenser configuration. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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16 pages, 3612 KiB  
Article
Constructal Optimizations of Line-to-Line Vascular Channels with Turbulent Convection Heat Transfer
by Daoguang Lin, Zhihui Xie, Gang Nan, Pan Jiang and Yanlin Ge
Entropy 2022, 24(7), 999; https://doi.org/10.3390/e24070999 - 19 Jul 2022
Cited by 1 | Viewed by 1258
Abstract
The multi-scale line-to-line vascular channels (LVCs) widely exist in nature because of their excellent transmission characteristics. In this paper, models of LVCs with turbulent convection heat transfer are established. Based on constructal theory and the entropy generation minimization principle, the constructal optimizations of [...] Read more.
The multi-scale line-to-line vascular channels (LVCs) widely exist in nature because of their excellent transmission characteristics. In this paper, models of LVCs with turbulent convection heat transfer are established. Based on constructal theory and the entropy generation minimization principle, the constructal optimizations of LVCs with any order are conducted by taking the angles at bifurcations as the optimization variables. The heat flux on the channel wall per unit length is fixed and uniform. The areas occupied by vasculature and the total volumes of channels are fixed. The analytical expressions of the optimal angles, dimensionless total entropy generation rate and entropy generation number (EGN) of LVCs with any order versus dimensionless mass flow rate are obtained, respectively. The results indicate that the dimensionless total entropy generation rate of LVCs with any order can be significantly decreased by optimizing the angles of LVCs, which is significantly more when the order of LVCs is higher. As the dimensionless mass flow rate increases, the optimal angles of LVCs with any order remain unchanged first, then the optimal angles at the entrance (root) increase, and the other optimal angles decrease continuously and finally tend to the respective stable values. The optimal angles of LVCs continue to increase from the entrance to the outlet (crown), i.e., the LVCs with a certain order gradually spread out from the root to the crown. The dimensionless total entropy generation rate and EGN of LVCs first decrease and then increase with the growth of the dimensionless mass flow rate. There is optimal dimensionless mass flow rate, making the dimensionless total entropy generation rate and the EGN reach their respective minimums. The results obtained herein can provide some new theoretical guidelines of thermal design and management for the practical applications of LVCs. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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21 pages, 6569 KiB  
Article
Design and Optimization of the Inlet Header Structure in Microchannel Heat Exchanger Based on Flow Distribution Uniformity
by Kaidi Zhang, Wei Wei, Yuwei Sun, Qiang Wu, Min Tang and Mingjian Lu
Appl. Sci. 2022, 12(13), 6604; https://doi.org/10.3390/app12136604 - 29 Jun 2022
Cited by 3 | Viewed by 1931
Abstract
The flow distribution in a printed circuit heat exchanger (PCHE) is of great theoretical and practical significance in the Brayton cycle power generation system. For the straight barrel inlet header PCHE, when S-CO2 flows in the PCHE, the structural types and working [...] Read more.
The flow distribution in a printed circuit heat exchanger (PCHE) is of great theoretical and practical significance in the Brayton cycle power generation system. For the straight barrel inlet header PCHE, when S-CO2 flows in the PCHE, the structural types and working parameters of the inlet header and diversion zone may lead to differences in the flow distribution in each channel of the PCHE. This flow distribution difference affects the thermal hydraulic characteristics of the PCHE. A numerical simulation method was applied to explore the flow uniformity of the PCHE and the overall performance and analyze the influence of the type of straight barrel inlet header PCHE. Within each layer, the flow showed an uneven flow distribution, and the optimized inlet header was the tapered type. The results showed that when the taper angle varies from 6° to 9°, the flow distribution in each layer is relatively uniform. The comprehensive heat transfer performance of the straight-channel PCHE can be improved by 17.3–19.7%. Finally, the response surface and a genetic algorithm were combined to optimize the inlet header. The heat transfer performance of the optimized PCHE was improved by 19.7%. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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9 pages, 487 KiB  
Article
Modular Spiral Heat Exchanger Thermal Modelling
by Bystrík Červenka, Michal Holubčík, Juraj Drga and Milan Malcho
Appl. Sci. 2022, 12(12), 5805; https://doi.org/10.3390/app12125805 - 07 Jun 2022
Cited by 2 | Viewed by 1473
Abstract
Spiral plate heat exchangers (SPHEs) are used in industrial applications due to their enhanced thermal performance and tolerance to a soiled stream. The coupling of several SPHEs in series might further improve performance in terms of the effectiveness parameter. In the present study, [...] Read more.
Spiral plate heat exchangers (SPHEs) are used in industrial applications due to their enhanced thermal performance and tolerance to a soiled stream. The coupling of several SPHEs in series might further improve performance in terms of the effectiveness parameter. In the present study, a compact connection of several SPHE modules is proposed and investigated. For this purpose, a numerical model for the prediction of the effectiveness parameter of a modular SPHE was developed. The model predicted a 2.9% increase in the maximal effectiveness for a two-module SPHE in comparison to a conventional single module SPHE. The temperature profiles of particular streams within the two-module SPHE were predicted. The improved thermal performance and compactness of the modular SPHE configuration observed is advantageous for space-constrained applications. Full article
(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)
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