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New Advancement in Heat and Mass Transfer: Fundamentals and Applications (Volume II)

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "J1: Heat and Mass Transfer".

Deadline for manuscript submissions: closed (22 November 2023) | Viewed by 8831

Special Issue Editors

Merchant Marine College, Shanghai Maritime University, Shanghai 201306, China
Interests: energy storage; heat and mass transfer; numerical methods; petroleum storage and transportation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Heat transfer, widely involved in various energy systems, has a great impact on the safety and energy consumption of these systems. The establishment of energy-efficient operation schemes for these systems requires a good understanding of heat transfer characteristics. In the context of carbon neutrality, energy saving is of particular interest, but it requires a more accurate and detailed understanding of behavior of heat transfer to establish more energy-efficient schemes. Therefore, some traditional heat transfer problems are reconsidered and investigated with more advanced techniques to clarify the comprehensive heat transfer characteristics involved. In addition, with the development of new technologies, equipment tends to be microscale or nanoscale, and heat transfer within microscale or multiscale systems are new problems which have been encountered in recent years.

This special issue is a continuation of the previous and successful series of Special Issue with topic of “Heat and Mass Transfer”. It aims to cover new advancements in heat transfer, either fundamentals or applications, in different research fields. Topics of interest include but are not limited to the following:

Fundamentals of heat transfer:

  • Multiphase flow and heat transfer;
  • Multiscale heat transfer;
  • Combustion;
  • Heat and mass transfer in porous media;
  • Radiation;
  • Biofluid dynamics and heat transfer;

Experimental and numerical research on  heat transfer related to:

  • Fossil and renewable energy using systems;
  • Energy conversion and storage systems;
  • Heat exchangers;
  • Fuel cells;
  • Heat pipe;
  • Air conditioning and refrigeration;
  • Heat transfer enhancement;
  • Thermal insulation.

Apart from original research related to the abovementioned topics, studies on the state of the art in relation to previous works are also welcome.

Dr. Guojun Yu
Dr. Huijin Xu
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • heat and mass transfer
  • numerical heat transfer
  • heat transfer enhancement
  • heat convection
  • heat conduction
  • heat radiation
  • thermal storage
  • thermal insulation
  • phase change

Related Special Issue

Published Papers (7 papers)

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Research

Jump to: Review

15 pages, 5110 KiB  
Article
Study on Preparation and Properties of PNIPAm/PPy Hydrogel Hygroscopic Material for Solid Dehumidification System
by Jinlin Liu, Yu Wang, Zilong Zhong, Zhou Zhou, Dongliang Chen, Weijie Wang and Shuaixing Mai
Energies 2023, 16(13), 5112; https://doi.org/10.3390/en16135112 - 02 Jul 2023
Viewed by 1089
Abstract
Air-conditioning systems account for 40–60% of the energy consumption of buildings, and most of this figure corresponds to the cooling and dehumidification process of air-conditioning units. Compared with traditional compressed air-conditioning systems, solid adsorption dehumidification systems possess good potential to improve indoor air [...] Read more.
Air-conditioning systems account for 40–60% of the energy consumption of buildings, and most of this figure corresponds to the cooling and dehumidification process of air-conditioning units. Compared with traditional compressed air-conditioning systems, solid adsorption dehumidification systems possess good potential to improve indoor air quality and reduce buildings’ energy consumption. However, there are still some problems that prevent the use of solid adsorption dehumidification systems, such as their complexity and high regeneration temperatures. The key to solving the above problem is the discovery of more suitable adsorbents. In this paper, poly N-isopropylacrylamide/polypyrrole (PNIPAm/PPy) hydrogel was selected as the research object, and the performance of the dehumidification material and its potential for application in solid dehumidification systems were studied. It was found that the pore structure of PNIPAm/PPy was relatively complex and that there were abundant pores with uneven pore sizes. The minimum pore size was about 4 μm, while the maximum pore size was about 25 μm, and the pore sizes were mostly distributed between 8 and 20 μm. Abundant and dense pores ensure good hygroscopic and water-releasing properties of the resulting hydrogel. The PPy inside the hydrogel acts as both a hygroscopic and photothermal agent. In an environment with a relative humidity of 90%, 60%, and 50%, the hygroscopic efficiency of PNIPAm/PPy reached 80% in about 75, 100, and 120 min, and the corresponding unit equilibrium hygroscopic capacity values were 3.85 g/g, 3.72 g/g, and 3.71 g/g, respectively. In the initial stage, the moisture absorption increased with the increase in time; then, the increase in moisture absorption decreased. When the temperature was below 40 °C, the hygroscopic performance of PNIPAm/PPy was almost temperature-independent. The PNIPAm/PPy with different thicknesses showed similar moisture absorption efficiency. The lowest desorption temperature of PNIPAm/PPy was 40 °C, which indicates that low-grade energy can be used for material desorption. And the higher the temperature, the faster the desorption rate of PNIPAm/PPy and the higher the desorption amount. It can be seen that the PNIPAm/PPy hydrogel presents good desorption performance and can be used repeatedly. Full article
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8 pages, 1905 KiB  
Communication
Comparative Investigation on the Thermophysical Property and System Performance of R1234yf
by Gailian Li, Tingxiang Jin, Ran Xu and Zijian Lv
Energies 2023, 16(13), 5033; https://doi.org/10.3390/en16135033 - 28 Jun 2023
Viewed by 862
Abstract
In this paper, an experimental study of R1234yf replacing R22 in window air conditioning was carried out. The optimum types of capillary tubes and the charge amount were obtained, and the system performance of the window air conditioning charged with R1234yf was tested [...] Read more.
In this paper, an experimental study of R1234yf replacing R22 in window air conditioning was carried out. The optimum types of capillary tubes and the charge amount were obtained, and the system performance of the window air conditioning charged with R1234yf was tested in an air conditioner performance teat facility under nominal and high-temperature conditions. The results revealed that the cooling capacity and coefficient of performance (COP) of the air conditioner charged with R1234yf were 28.5% and 11.1%, respectively, under nominal conditions, which were lower than that of R22. Under high-temperature conditions, the cooling capacity of R1234yf was still lower than that of R22, but the COP was slightly higher. This suggests that R1234yf may be a suitable substitution for R22 in high-temperature environment. Full article
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20 pages, 4148 KiB  
Article
Investigating the Drying Process of Ceramic Sanitary Ware at Low Temperature
by Ricardo S. Gomez, Kelly C. Gomes, José M. A. M. Gurgel, Laís B. Alves, Hortência L. F. Magalhães, Raíssa A. Queiroga, Gustavo C. P. Sousa, Aline S. Oliveira, Anderson F. Vilela, Bruna T. A. Silva, Danielle B. T. Vasconcelos, Glauco R. F. Brito and Antonio G. B. Lima
Energies 2023, 16(10), 4242; https://doi.org/10.3390/en16104242 - 22 May 2023
Cited by 4 | Viewed by 1452
Abstract
Drying is one of the stages with the highest energy consumption in the manufacturing process of ceramic materials and aims to reduce the product’s moisture to levels necessary for safe firing stage, reducing the chances of defect formation. For sanitary ware, there is [...] Read more.
Drying is one of the stages with the highest energy consumption in the manufacturing process of ceramic materials and aims to reduce the product’s moisture to levels necessary for safe firing stage, reducing the chances of defect formation. For sanitary ware, there is an additional energy cost in the pre-drying stage, which takes place immediately after removing the parts from the molds, and is carried out in an environment with lower temperatures (ranging from 30 to 40 °C). This work aims to experimentally study the drying process of sanitary ware at low temperatures, with particular reference to sanitary toilets with industrial dimensions. Four drying experiments were carried out in an oven with different operating conditions (temperature and relative humidity). The results indicate that an increase in temperature and reduction in relative humidity provoke a faster drying rate. For some physical situations, it is more interesting to dedicate efforts to reducing the relative humidity of the drying air instead of seeking solutions to raise its temperature. Furthermore, a correlation between the linear retraction and moisture content was observed; the greater the moisture loss, the greater the sample shrinkage. Full article
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18 pages, 7910 KiB  
Article
Investigation on Effective Thermal Conductivity of Fibrous Porous Materials as Vacuum Insulation Panels’ Core Using Lattice Boltzmann Method
by Bangqi Chen, Ankang Kan, Zhaofeng Chen, Jiaxiang Zhang and Lixia Yang
Energies 2023, 16(9), 3692; https://doi.org/10.3390/en16093692 - 25 Apr 2023
Cited by 2 | Viewed by 1051
Abstract
Vacuum Insulation Panels (VIPs) provide significant adiabatic performance for heat/cooling systems to reduce energy consumption. The application of fibrous porous material (FPM) as the ideal core of VIPs has gained global attention in recent decades. The microstructure and physical properties of FPMs, filled [...] Read more.
Vacuum Insulation Panels (VIPs) provide significant adiabatic performance for heat/cooling systems to reduce energy consumption. The application of fibrous porous material (FPM) as the ideal core of VIPs has gained global attention in recent decades. The microstructure and physical properties of FPMs, filled as novel VIPs’ core material, and holding superior thermal performance, affected effective thermal conductivity (ETC) greatly. Aiming to deeply understand heat transfer mechanisms, a holistic simulation method that combined with a developed 3D FPM structure generation method and a D3Q15-Lattice Boltzmann method (LBM) is proposed to simulate the heat transfer in FPM and to illuminate the influence factors of ETC on the microstructure of FPM in a vacuum. The improved and modified mesoscopic 3D fibrous random micro-structure generation approach involved five structural parameters: generation probability of nucleus growth, fiber length, diameter, coincidence rate, and orientation angle. The calculation model of ETC is established, and the discrete velocity, distribution, evolution, and boundary conditions of D3Q15-LBM are invested in detail. The model is validated with influences of different microstructure parameters. It indicated that FPM with finer diameter, smaller average pore size, and bigger orientation angle easily gain the lower ETC in a vacuum. The ETC was also affected by the orientation angles of fibers. The more the heat transfer direction is inconsistent with the length direction of the fiber, the better the adiabatic performance is. The reliability of the model is verified by comparison, and this work is a reference to optimize the fibrous core of VIPs. Full article
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20 pages, 6942 KiB  
Article
Numerical Investigation on the Performance of IT-SOEC with Double-Layer Composite Electrode
by Yan Shao, Yongwei Li, Zaiguo Fu, Jingfa Li and Qunzhi Zhu
Energies 2023, 16(6), 2525; https://doi.org/10.3390/en16062525 - 07 Mar 2023
Cited by 2 | Viewed by 1462
Abstract
The double-layer composite electrode has attracted increasing attention in the field of intermediate-temperature solid oxide electrolysis cells (IT-SOEC). To investigate the effects of the cathode diffusion layer (CDL) and cathode functional layer (CFL) structure on performance, a three-dimensional multi-scale IT-SOEC unit model is [...] Read more.
The double-layer composite electrode has attracted increasing attention in the field of intermediate-temperature solid oxide electrolysis cells (IT-SOEC). To investigate the effects of the cathode diffusion layer (CDL) and cathode functional layer (CFL) structure on performance, a three-dimensional multi-scale IT-SOEC unit model is developed. The model comprehensively considers the detailed mass transfer, electrochemical reaction and heat transfer processes. Meanwhile, percolation theory is adopted to preserve the structural characteristics and material properties of the composite electrode. The mesostructure model and the macroscopic model are coupled in the solution. The effects of the porosity of the CDL, the electrode particle size and the composition of the composite electrode in the CFL on the mass transport process and electrolysis performance of the IT-SOEC unit are analyzed. The results show that the appropriate mass flux and energy consumption in the electrode are obtained with a CDL porosity in the range of 0.3–0.5. The decrease in the electrode particle size is conducive to the improvement of the electrolysis reaction rate. The maximum reaction rate in the CFL increases by 32.64% when the radius of the electrode particle is reduced from 0.5 μm to 0.3 μm. The excellent performance can be obtained when the volume fractions of the electrode phase and electrolyte phase in the CFL tend to be uniform. This study will provide guidance for the performance optimization of IT-SOEC and further promote the development of IT-SOEC hydrogen production technology in engineering applications. Full article
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27 pages, 9317 KiB  
Article
Comparative Study on Boiling Heat Transfer Characteristics and Performance of Low-Temperature Heating System of R744 and Its Azeotropic Refrigerant
by Dahan Sun, Xin Zhang, Zhongyan Liu and Hao Zhang
Energies 2023, 16(3), 1313; https://doi.org/10.3390/en16031313 - 26 Jan 2023
Cited by 2 | Viewed by 1057
Abstract
R744 is the most competitive and ideal natural refrigerant when flammability and toxicity are strictly limited. However, there are still some problems when it is applied to a heating system. For example, the discharge pressure of the system exceeds 10 MPa, it increases [...] Read more.
R744 is the most competitive and ideal natural refrigerant when flammability and toxicity are strictly limited. However, there are still some problems when it is applied to a heating system. For example, the discharge pressure of the system exceeds 10 MPa, it increases the cost of the system, and the cycle efficiency is also low. To solve these problems, this paper proposes to replace R744 by mixing R744 and ethane at a ratio of (77.6/22.4) to form an azeotropic refrigerant. At present, there is little research on R744 azeotropic refrigerant. Therefore, this paper first establishes the CFD model and compiles the UDF program to focus on flow boiling heat transfer characteristics, and then, it analyzes the performance of R744 and its azeotropic refrigerant in a low-temperature heating system. The results show that the heat transfer coefficient of R744 and its azeotropic refrigerant decreases with an increase in mass flux and increases with an increase in heat flux and saturation temperature; the heat transfer coefficient of azeotropic refrigerant is greater than R744; and there is no dryness under the same conditions. Under a given operating condition, there is a critical point that makes the performance of azeotropic refrigerant better than R744, and this critical point is related to the outlet temperature of a gas cooler, and the system discharge temperature of azeotropic refrigerant is significantly lower than that of R744. In conclusion, azeotropic refrigerant has certain advantages in heat transfer and system performance compared with R744, which will also play an important role in promoting the replacement of refrigerant in the future. Full article
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Review

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16 pages, 3378 KiB  
Review
Review of Oil–Water Flow Characteristics of Emptying by Water Displacing Oil in Mobile Pipelines
by Yan Chen, Guang Li, Jimiao Duan, Huishu Liu, Shuo Xu, Yang Guo, Weixing Hua and Junze Jiang
Energies 2023, 16(5), 2174; https://doi.org/10.3390/en16052174 - 23 Feb 2023
Cited by 1 | Viewed by 1291
Abstract
Water displacing oil is one of the main emptying methods for mobile pipelines. It has the advantages of being a simple process and highly safe. At present, the determination of a water displacing oil scheme of mobile pipelines is based on the oil–oil [...] Read more.
Water displacing oil is one of the main emptying methods for mobile pipelines. It has the advantages of being a simple process and highly safe. At present, the determination of a water displacing oil scheme of mobile pipelines is based on the oil–oil alternating transport theory of product oil pipelines. However, the insolubility of the oil phase and the water phase results in a great difference between the flow characteristics of water displacing oil and the oil–oil alternating transport of a product oil pipeline. In addition, due to the effect of buoyancy, the oil phase gathers at the high point of the pipeline and forms a liquid accumulation, which is difficult to carry away by water flow, resulting in the low emptying efficiency of the mobile pipeline. The essence of water displacing oil in a mobile pipeline is an oil–water two-phase unsteady displacement flow, involving liquid–liquid displacement flow, oil–water two-phase flow and water carrying oil. Aiming at such problems, domestic and foreign scholars have carried out a large number of theoretical and experimental studies, established the oil–water mixing model of water displacing oil and the relationship between macroscopic quantity (flow pattern, pressure drop and water content) and microscopic quantity (local flow field and droplet dispersion pattern, etc.) under each flow type, and explored the influence of pipeline diameter, oil phase velocity, pipeline inclination angle and other parameters on the capacity of carrying liquid accumulation. On this basis, this paper analyzes the shortcomings of the current research on the oil–water flow characteristics of water displacing oil in a mobile pipeline from three aspects: the formation mechanism of the oil–water mixture, displacing flow characteristics of immiscible fluids and flow characteristics of water carrying oil. Five future research directions are proposed, including the interface morphology and flow field characteristics of oil–water two-phase layered flow, local mixing characteristics of an oil–water two-phase dual continuous flow interface, droplet distribution and flow characteristics of oil–water two-phase dispersed flow, unsteady flow characteristics of the oil–water mixture of water displacing oil and oil accumulation and flow characteristics in topographic relief pipes. Full article
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