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One of the most energy-intensive processes is the drying process. Therefore, an important task is to reduce heat consumption for drying. Various ways to improve the drying devices of paper and cardboard machines are identified. The main disadvantages of these improvements are given. The limiting factor of heat transfer from water vapor to paper is established. The dependence of thermal resistance on the thickness of the condensate layer is given. The authors have developed a new design for condensate drainage. The developed design allows installing movable siphons without replacement of steam inlet heads of the old type (for fixed siphons) with their insignificant modernization and cutting of an annular groove inside the drying cylinder. This will ensure a minimum level of condensate and eliminate the possibility of suction of steam into the condensate return system. Additionally, this will reduce thermal resistance, heat loss, and reduce energy consumption for paper drying as a whole. Keywords: paper drying, moisture content, drying cylinder, thermal resistance, heat transfer.

Given the thermal management problem aroused by increasing power densities of electronic components in the system, graphene-based papers have raised considerable interest for applications as thermal interface materials (TIMs) to solve interfacial heat transfer issues. Significant research efforts have focused on enhancing the through-plane thermal conductivity of graphene paper, however, for practical thermal management applications, reducing the thermal contact resistance between graphene paper and the mating surface is also a challenge to be addressed. Here, a strategy aimed at reducing the thermal contact resistance between graphene paper and the mating surface to realize enhanced heat dissipation was demonstrated. For this, graphene paper was decorated with polydopamine EGaIn nanocapsules using a facile dip-coating process. In practical TIM application, there was a decrease in the thermal contact resistance between the TIMs and mating surface after decoration (from 46 to 15 K mm2 W−1), which enabled the decorated paper to realize a 26% enhancement of cooling efficiency compared with the case without decoration. This demonstrated that this method is a promising route to enhance the heat dissipation capacity of graphene-based TIMs for practical electronic cooling applications.

Graphene-based papers have recently triggered considerable interests in developing the application as thermal interface materials (TIMs) for addressing the interfacial heat transfer issue, but their low through-plane thermal conductivity (κ⊥), resulting from the layer-by-layer stacked architecture, limits the direct use as TIMs. Although various hybrid graphene papers prepared by combining the graphene sheets and the thermally conductive insertions have been proposed to solve this problem, achieving a satisfactory κ⊥ higher than that of commercial TIMs (>5 W m−1 K−1) remains challenging. Here, a strategy aimed at the construction of heat pathways along the through-plane direction inside the graphene paper for achieving a high κ⊥ was demonstrated through the simultaneous filtration of graphene sheets with two different lateral sizes. The as-prepared graphene paper presented a hierarchical structure composed of loosely stacked horizontal layers formed by large graphene sheets, intercalated by a random arrangement of small graphene sheets. Due to the heat pathways formed by small graphene sheets along the through-plane direction, the hierarchically structured graphene paper exhibited an improved κ⊥ as high as 12.6 W m−1 K−1 after a common graphitization post-treatment. In the practical test, our proposed paper as an all-graphene TIM achieved an enhancement in cooling efficiency of ≈ 2.2 times compared to that of the state-of-the-art TIM, demonstrating its superior performance to meet the ever-increasing heat dissipation requirement.

Establishing and optimizing a distributed parameter thermal path model for transformer windings is an important means to analyze the hot-spot temperature of the windings; furthermore, in the process of improving the thermal path model of transformers and improving the accuracy of their models, the thermal characteristics of the insulation paper are extremely important. A microscopic thermal contact resistance model was established for the contact interface of insulation paper and copper, according to the microscopic morphology parameters of copper and insulation paper observed by atomic force microscopy, the thermal contact resistance under different temperatures was calculated. A dual heat flow test platform was built to test the heat transfer behavior of four different thickness insulation papers under four temperatures, and the thermal contact resistance and thermal bulk resistance with temperature were analyzed. The results show that as the temperature increases, the thermal resistance of the insulation paper becomes larger and the thermal conductivity decreases. The average error between the experimental and theoretical values of the thermal contact resistance under four temperature points in the study is 6.6%. The results provide a data support for establishing and optimizing transformer heat generation and heat transfer models.

The current technologies to treat hypersaline produced water (PW), such as thermal evaporation, are usually energy-intensive and cost-prohibitive. This study developed a low-cost, robust, solar-driven carbon black and airlaid paper-based evaporator (CAPER) for desalination of PW in the Permian Basin, United States. The study aims to better understand the removal of aromatic organic compounds and heavy metals during solar distillation, water output, and heat transfer. Outdoor experiments using CAPER assisted with polystyrene foam in a single slope, single basin solar still achieved an enhanced average evaporation rate of 2.23 L per m2 per day, 165% higher than that of a conventional solar still. Analysis of heat transfer models demonstrated that CAPER solar evaporation achieved an evaporative heat transfer coefficient of ∼28.9 W m−2·K−1, 27.9% higher than without CAPER. The maximum fractional energy of evaporation and convection heat transfer inside the solar still with and without CAPER was ∼81.4% and ∼78.2%, respectively. For the PW with a total dissolved solids concentration of 134 g L−1, solar distillation removed 99.97% salts and over 98% heavy metals. The high removal efficiency of 99.99% was achieved for Ca, Na, Mg, Mn, Ni, Se, Sr, and V. Organic characterization revealed that solar distillation removed over 83% aromatic compounds. Solar desalination using CAPER provides a low-cost and high-performance process to treat PW with high salinity and complex water chemistry for potential fit-for-purpose beneficial uses.

The paper presents the results of investigations on the thermal properties of cellulose and aramid paper impregnated with various liquid insulations. The liquid insulations investigated were mineral oil, synthetic ester, and natural ester. The heat transfer coefficient of the liquid was calculated on the basis of measurements of the thermal expansion, specific heat, density, thermal conductivity and kinematic viscosity of the liquid insulations. Temperatures in the paper and liquid insulations were calculated. The results allow to select the best paper and liquid insulations which provide the most effective cooling in transformers.

This Special Issue will publish selected papers from the International Symposium on Thermal Effects in Gas flow in Microscale ISTEGIM 2019 - A MIGRATE Event (http://www.istegim.eu/), 24-25 October 2019, Ettlingen, Germany. MIGRATE (www.migrate2015.eu) is a H2020 Marie Sklodowska-Curie European Training Network, intended to address some of the current challenges to innovation that faces European industry with regard to heat and mass transfer in gas-based micro-scale processes. This network of 10 participants and 6 associated partners coming from all over the European Community covers different aspects of enhanced heat transfer and thermal effects in gases: from modelling of heat transfer processes and devices, development and characterization of sensors and measurement systems for heat transfer in gas flows as well as thermally driven micro gas separators, to micro-scale devices for enhanced and efficient heat recovery in environmental, transport, telecommunications and energy generation. The MIGRATE Project presents his 2-day symposium, ISTEGIM19, during which the members of the MIGRATE network will showcase the main achievements of the project. The program will include keynote lectures, invited lectures and contributed papers.

This Special Issue of Heat Transfer Engineering includes thirteen selected papers from the 1st International Conference on Nanofluids (ICNf), which was held at Universitat Jaume I, in Castello (Spa...

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2017. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) In building mechanical system research fields, twenty studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (2) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to the ventilated cavity of curtain-wall system for enhancing insulation and preventing condensation, the improvement plans of condensation defect examples in apartment building and the calculation method for the transmitted solar irradiance using the total horizontal irradiance. The subjects of building energy are worked on the energy consumption characteristics in office buildings, energy performance analysis for energy saving potentials in a hospital building, outdoor air cooling system operated with load prediction, building energy efficiency rating changes by enhanced building envelope standards, energy saving effect for the external insulation construction, energy reduction of a heating network through the application of an absorption heat pump, analysis of thermal load profile according to the window retrofit in an old school building, calculating regional balance point temperature for heating degree-days in korea, short-term load prediction using artificial neural network models, the simple window model applied to EnergyPlus, possibility of building energy saving through the building data, optimal cooling operation of a single family house model equipped with renewable energy facility by linear programming. The remained studies are related to the comparison between korea and china evacuation laws in office building, the effect of cold air stimulation during the driver’s drowsiness, the calculation of the attachedpiping-material rate for the building mechanical-service system in office buildings, the development of a modularlightweight steel ceiling system and the evaluation of local loss coefficients for different waveguide-below-cutoff (wbc) arrays of electromagnetic pulse. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, research subjects include the improvement of Type II and double-effect absorption heat pumps, the seasonal performance of compression heat pumps, a vertical receiver in a compression heat pump, the performance of a domestic built-in ice maker and the performance characteristics of a surface water heat pump system. In the alternative refrigeration/energy system category, subjects include a membrane dehumidification system, a CO₂-hydrate circulation system, a Zeolite 13x chemical thermal energy storage system and the performance criteria for heat pumps as a renewable energy device. In the system control category, subjects include a defrosting control system using photoelectric sensors and the control method for an organic thermal storage-chiller system. (4) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for prediction of stratification model for diffusers in underfloor air distribution system using the CFD, transport properties for transportation of captured CO₂, dynamic thermal design of a 1-ton class bio-hydrogen production system simulator, cylindrical premixed burner, heat transfer enhancement in a divergent passage with 30° inclined ribs, the development of regulatory guideline on the applicability of CFD software, a staggered fin, single phase thermal stratification in both cold legs and downcomer. In the area of pool boiling and condensing, effects of tube diameter and surface sub-cooling temperature on R1234ze(E) and R1233zd(E) film condensation heat transfer characteristics in smooth horizontal laboratory tubes, surface energy variations and condensate behaviors on nitrogen ion implanted aluminum surfaces were studied. In the area of industrial heat exchangers, plate type enthalpy exchanger through CFD analysis of elements, fluidized bed heat exchanger for heat recovery from multi-heat sources, paper enthalpy exchange element by impregnation of the spacer, the effect of the air temperature on the air-side heat-transfer coefficient and the friction factor of a fin-and-tube heat exchanger, cooling of telecommunication cabinet, effects of seawater fouling on a plate-frame heat exchanger, carbon dioxide during heating process in the near-critical region for single channel, a heat exchanger for an air-compressor of a railway vehicle were studied.

It is crucial for the successful application of high-temperature superconducting (HTS) power transformers that they are able to survive under abnormal operations, such as a short-circuit fault. Modeling, based on the design of a four-winding three-phase HTS power transformer, suggests severe boiling will occur on the surface of the winding during a short-circuit fault and will jeopardize the turn-to-turn insulation of the HTS power transformer. In this paper, a turn-to-turn insulation breakdown experiment platform involving the introduction of boiling on the surface of electrode has been built. Nomex 410 paper, one of the candidates for turn-to-turn insulation in the design of the HTS power transformer, was tested. The characteristics of dielectric strength of Nomex 410 in three different thicknesses (0.13, 0.18, and 0.25 mm) have been investigated, without boiling, as well as under different boiling situations, in an open bath of liquid nitrogen. The voltage application methods applied during both experiments test the electrical breakdown of Nomex 410 under a dynamic situation. The experiment results show that when under film boiling, compared to the test results for nucleate boiling, the dielectric strength of Nomex 410 paper decreases by approximately 38% of the value when no boiling is involved. Moreover, it is verified that the presence of an electric field accelerates the heat transfer between the liquid nitrogen and the heated electrode.

The series of UK Heat Transfer Conference (UKHTC) has been organized under the auspices of the UK National Heat Transfer Committee since 1984. The UKHTC is currently a premier forum in the UK for t...

This paper was removed from publication at the author’s request. January 15, 2021. Copyright © 2021 by ASME

A review of the most important findings for jets impingement on rotating target is presented, the focus is on the heat transfer and flow dynamics in these jets. These jet configurations are encountered in many industrial applications. A significant number of research studies dealing with computational and experimental studies are reviewed. Different parameters are found to influence the flow and enhance mass and energy transfer in several heat configurations such as; Reynolds number (Re), nozzle geometry, spacing between jet exit and the impinging plate, jet impinging angle and the flow regime at the jet exit. There are a few studies that deal with heat transfer of a flow impinging on a rotating disk due to complexity of the flow structure and the challenges to conduct in-depth experimental investigation. Most studies present profiles of heat transfer coefficients, mean velocity and turbulence rates of the impinging flow. Many researches have reported that the LES can predict heat transfer and flow field data for different impinging angles to study the feedback mechanism between the nozzle and the plate.

The above referenced paper has been removed from publication. (April 21, 2020) Copyright © 2020 by ASME

The horizontal flame spread over paper samples was investigated using a subatmospheric cabin with varied O2 concentration. The 25 kPa is found to be a clear turning point for the flame illumination and structure, radiative heat flux and flame spread rate (FSR), which leads to the transition boundary between the extinction limits and power law regions. In the extinction limits (non-linear) region below 25 kPa, the oxygen partial pressure is low with a small Da number. Consequently, the flame spread is gas phase kinetics controlled, resulting in low burning rate, low radiative heat loss and weak buoyancy, and thus the FSR is more sensitive to the oxygen concentration while less sensitive to the ambient pressure. In the power law (linear) region above 25 kPa, in contrast, the oxygen partial pressure is high and the Da number is large, and the flame spread is heat transfer controlled, which weakens the dependence of FSR on oxygen concentration and enhances the dependence on air pressure.

It is our great pleasure and honor to present this special issue of Heat Transfer Engineering to highlight some of the research works presented at the AIGE 2016 Conference on Energy Conversion, Man...

The temperature distribution is vital to the lifetime and reliability of converter transformer bushings. However, the temperature distribution of epoxy impregnated paper converter bushings under a certain current has usually been calculated through the two dimensional model, without considering the heat convection and radiation effects. In this paper, using the computational fluid dynamics (CFD) and finite element method (FEM) analysis, a 3-D electromagnetic-fluid-thermal analysis method has been proposed. With the considering of heat conduction, heat convection and radiation, the temperature distribution of the converter transformer bushing has been simulated according to the actual operating environment. The temperature and velocity distribution of the converter transformer bushing has been obtained. Moreover, the simulation results have been compared with the experimental results to verify the accuracy of the simulation method. The simulation results, especially for the inner conductor, external conductor and the epoxy impregnated paper, are very close to the experimental results and the maximum temperature difference percentage is within 10 %, which indicates the accuracy and effectiveness of the electromagnetic-fluid-thermal analysis method proposed.

The present comment refers to some doubtful results included in the above mentioned paper.

The factors affecting on the fluting of the coated paper in the web-offset printing are discussed.In the early part of the drying process of the web-offset printing, moisture contained in the coated paper evaporates rapidly from a non-imaged area, resulting a large shrinkage in the cross direction of the coated paper in the non-imaged area. On the contrary, moisture of the coated paper lying under an imaged area evaporates slowly because a printed ink layer on the coated paper acts as heat transfer and moisture evaporation barrier, resulting a small shrinkage in the cross direction of the coated paper in the imaged area. As a result, the non-imaged area of the coated paper compresses the adjoining imaged area in the cross direction during the drying process leading to the buckling of the imaged area. It is the flutes of the coated paper in the web-offset printing.In this case, number of the flutes in the imaged area is defined by three parameters: Pc is the compressive force that acts to the imaged area, S is Gurley stiffness of the coated paper in the cross direction and b is size of the imaged area, as shown in formula (1). If these parameters of the coated paper which some flutings are shown on is fluctuated, the change of number of the fluting is predicted.

In Korea, summer is hot and humid, and air-conditioners consume lots of electricity. In such case, simultaneous usage of indirect evaporative cooler may reduce the sensible heat and save the electricity. In this study, heat transfer and pressure drop characteristics of indirect evaporative cooler made of aluminum, plastic, plastic/paper are investigated both under dry or wet condition. Results show that indirect evaporation efficiencies of the plastic/paper sample (38.5% ~ 51.4%) are approximately the same as those of the aluminum sample (41.9% ~ 47.5%), and are larger than those of the plastic sample (29.0% ~ 37.4%). This suggests that the plastic/paper sample could be a good substitute to the aluminum sample. However, the pressure drops across the paper channel are 92% ~ 106% larger than those across the aluminum channel. The heat transfer coefficients of the paper channel under dry condition are 15% ~ 44% larger than those of the plastic channel. The increases are 185% ~ 203% for the aluminum channel. The pressure drops of the paper channel are 34% ~ 48% larger than those of the plastic channel and 93% ~ 106% larger than those of the aluminum channel. Rigorous heat transfer analysis reveals that, for the plastic sample, 30% ~ 37% of the wet channels remain dry, whereas all the channels are wet for plastic/paper sample. For aluminum sample, the ratio is 17% ~ 23%.

It is our great pleasure and honor to present this special issue of Heat Transfer Engineering to highlight some of the research works presented at the ASME-ATI-UIT 2015 Conference on Thermal Energy Systems: Production, Storage, Utilization, and the Environment that took place on May 17–20, 2015, in Napoli, Italy. The conference was organized under the auspices of the American Society of Mechanical Engineers (ASME), Associazione Termotecnica Italiana (ATI), and Unione Italiana di Termofluidodinamica (UIT). Ten papers included in this special issue were edited by Professor Afshin Ghajar, Editor-in-Chief of Heat Transfer Engineering. The papers report studies of heat transfer related to its enhancement and application to energy systems. The contents open with a paper on experimental measurements in flow boiling heat transfer of low-GWP (Global Warming Potential) refrigerant R1234yf. It is followed by an experimental investigation of volumetric heat transfer coefficient in three-phase direct contact condenser. A study, both experimental and numerical, on dropwise cooling is also presented on studying the cooling effect of two water droplets gently released onto a heated solid surface. Under the framework of passive heat transfer enhancement, a numerical investigation of laminar mixed convection in a two-dimensional, symmetrically, and partially heated vertical channel with nanofluids is provided. Followed by a study that used Ethylene glycol and water (60:40 EG/W mass ratio) as base fluid with SiO2 nanoparticles as nanofluid in order to compute Nusselt number and friction factor for turbulent pipe flow under the heat flux boundary condition. An active method of enhancing cooling of an array of heat sources mounted in a duct was numerically addressed in another paper. The papers on applications in energy systems starts with a numerical analysis of freezing of phase change materials in a thermal energy storage device integrated with a milk storage cooling cycle. Also given is a study on dynamic models for analyzing and evaluating energy storage concepts and interactions with a concentrated solar power system. Moreover, correlations developed from experimental data for predicting dehumidification and thermal performance of a desiccant wheels are presented. They correlate inlet air temperature and humidity ratio, regeneration temperature, air flow rates, and rotational speed. To complete the energy systems topic, a study on two small second-generation compressed air energy storage systems based on a recuperated gas turbine is presented. Special thanks are due to the authors of the papers in this special issue and the reviewers. We extend special thanks to Professor Afshin Ghajar, Editor-in-Chief of Heat Transfer Engineering, who has whole-heartedly supported this conference and the Special Issue. His tireless efforts in assuring high-quality publications are sincerely appreciated.

The Korean summer is hot and humid, and air-conditioners consume considerable amounts of electricity. In such cases, the simultaneous use of indirect evaporative coolers may help reduce the sensible heat and save electricity. In this study, heat transfer and pressure drop characteristics of indirect or regenerative evaporative coolers made from plastic/paper are investigated. The results showed that heat and mass transfer model based on the method predicted the indirect evaporation efficiencies, cooling capacities and pressure drops adequately. Both for indirect or regenerative evaporative cooler, the indirect evaporation efficiency increased with increasing dry channel inlet temperature or relative humidity. The indirect evaporation efficiency of the regenerative evaporative cooler was larger than that of the indirect evaporative cooler.

In this paper, we present an experimental study on measurement of the thermal conductivity and heat pipe effect in both hydrophilic and hydrophobic (Toray TGP-H60) carbon papers (around 200 μm thickness) with/out liquid water. An experimental setup is developed for measuring thermal conductance at different liquid water contents and temperatures without dissembling the testing device for water addition. Theoretical analysis is also performed to evaluate the apparent conductance of heat pipe effect. We found that liquid water presence inside these materials increases the overall thermal conductivity. At high temperature around 80 °C, the heat pipe effect is evident for the hydrophilic paper; while for the hydrophobic one, the heat pipe effect is found to be smaller. The distinction is likely due to the different patterns of the capillary liquid flow in the two media. For the hydrophobic paper, liquid water flows back to the evaporation side when the breakthrough pressure is reached and flow is through preferred routes of small flow resistance. As a result, heat pipe effect is active only in part of the medium, therefore smaller than that in the hydrophilic one. The results are important for understanding the heat transfer phenomena occurring in porous media and effects of material surface property. © 2012 Elsevier Ltd. All rights reserved.

This Special Issue of Heat Transfer Engineering includes ten selected papers from the 15th UK Heat Transfer Conference, which was held at Brunel University London on 4th to 5th September 2017. The ...