Liquid Heat Transfer Research Articles

Experimental investigations on the design of a dual-media thermal energy storage with liquid metal

Liquid metals are a promising heat transfer fluid with stability over a wide temperature range and high thermal conductivity. In concentrating solar energy power plants, as well as in the steel processing facilities heat is generated at high temperature level. Many fluids begin to decompose at such high temperatures and gases have poor thermal conductivity, making it difficult to effectively store and extract heat from the source. Liquid metal heat transfer fluids are able to effectively transport energy at a wide range of temperatures (150 ∘C–1000 ∘C). Existing heat transfer fluids, such as molten salts, have a working range between 290 ∘C and 565 ∘C for example. Depending on the metal selected, thermal conductivity can be 30 to 100 times higher than molten salts, but liquid metals have lower energy density. The liquid metal can be paired with a filler material having a higher energy density to develop a system with high energy transport and storage capability. The first lab-scale experiment of thermocline energy storage with liquid metal as a heat transfer fluid and a zirconium silicate filler, called VESPA [Vorversuch EnergieSPeicher Aufbau (ger.), engl. Preliminary test for energy storage setup], was carried out to prove the concept. So far, there are promising, yet only numerical investigations of thermocline energy storage with liquid metal as heat transfer fluid. The storage system under investigation was a dual-media thermocline energy storage system with liquid lead–bismuth eutectic as heat transfer fluid and zirconium silicate as filler material. The experiments were executed at temperatures from 180 ∘C to 380 ∘C, and focused on design aspects of the energy storage system. Different modes of operation of the storage system were investigated, including charging, discharging, and stand-by. Results are presented showing changes in the vertical temperature profile of the energy storage while varying mass flow, inlet temperature, and filler material.

Using lattice Boltzmann method to control entropy generation during conjugate heat transfer of power-law liquids with magnetic field and heat absorption/production

Using lattice Boltzmann method to control entropy generation during conjugate heat transfer of power-law liquids with magnetic field and heat absorption/production

A multiscale finite element method for coupled heat and water transfer in heterogeneous soils

Large-scale modeling of coupled heat and water transfer (CHWT) is challenging due to the spatial variabilities of soil hydraulic and thermal properties. A multi-scale finite element method (MsFEM) has been designed for simulating liquid water fluxes in unsaturated soils. In this study, the MsFEM approach is expanded as a new scheme that can handle CHWT in soils. Two groups of MsFEM basis functions are constructed to incorporate the heterogeneities in soil hydraulic conductivity and thermal conductivity, and a Petrov-Galerkin formulation is adopted to implement the proposed MsFEM scheme. The MsFEM scheme is also exploited as a sequential solver when heat transfer and water transfer are expressed in a partially coupled formulation (Wang et al., 2022a). Numerical examples illustrate that, without essentially increasing the computing load, the MsFEM scheme can improve the accuracy by up-to 30% compared to the standard finite element method (FEM), especially for thermally driven water transfer. Some fine scale spatial variations in soil temperature can only be revealed with the MsFEM scheme. If the MsFEM sequential solver is applied, the coupled heat and water transfer model can be rewritten into a sequence of modules, where liquid water transfer, heat transfer and vapor transfer are solved step-by-step, but the thermally driven liquid water is omitted due to its relatively small value (Wang et al., 2022a). With the MsFEM sequential solver, a flexible modeling architecture can be achieved at the cost of a relatively small increase of error (<5%). Therefore, the MsFEM scheme presented in this study is an effective numerical approach to simulating CHWT in heterogeneous soils.

Characteristics of air-liquid heat and mass transfer in a bubble column humidifier.

Bubble columns are recently used for the humidification of air in water treatment systems and fuel cells. They are well applicable due to their excellent heat and mass transfer and their low technical complexity. To design and operate such devices with high efficiency, the humidification process and the impact of the operating parameters need to be understood to a sufficient degree. To extend this knowledge, we use a refined and novel method to determine the volumetric air–liquid heat and mass transfer coefficients and the humidifier efficiency for various parametric settings. The volumetric transfer coefficients increase with both of the superficial air velocity and the liquid temperature. It is further shown that the decrease of vapor pressure with an increase of the salinity results in a corresponding decrease in the outlet humidity ratio. In contrast to previous studies, liquid heights smaller than 0.1 m are investigated and significant changes in the humidifier efficiency are seen in this range. We present the expected humidifier efficiency with respect to the superficial air velocity and the liquid height in an efficiency chart, such that optimal operating conditions can be determined. Based on this efficiency chart, recommendations for industrial applications as well as future scientific challenges are drawn.

Modeling liquid rocket engine coolant flow and heat transfer in high roughness channels

The design of thrust chambers of modern liquid rocket engines is moving towards the use of additive layer manufacturing techniques, which are replacing traditional techniques because of its inherent advantages of customization and flexibility of design and prototyping phase that in the end leads to advantages in terms of production costs and times. In this framework, the realization of suitable cooling channels, which are characterized by tiny cross section, can lead to high relative surface roughness, as a result of the manufacturing process. Despite the increased friction loss, high roughness channels are considered often with interest because of the corresponding increase of heat transfer and thus cooling efficiency. However, the correlation between the increase of friction and heat transfer changes at high roughness. As a consequence, the commonly used assumption for heat transfer prediction at low roughness may lead to order of magnitude errors if extended to high roughness channels. To respond to the request of a reliable heat transfer prediction model, the correction introduced by Aupoix to the Spalart-Allmaras turbulence model to take into account for high roughness in external flows is extended and validated here for the application to high roughness channels. The implementation of the proposed correction allows to predict realistic values of the convective heat transfer coefficient, in agreement with the correlations reported in the literature.

Effect of salt fingers on heat transfer for different non‐uniform concentration profiles in a micropolar liquid

AbstractThis paper discusses the theoretical aspects of the effect of salt fingers on heat transfer for different non‐uniform concentration profiles in a micropolar liquid layer kept between two parallel plates of infinite extent separated by a thin layer, heated and soluted from above. The onset of salt finger convection (convection due to the salt finger process) is studied through the linear stability analysis theory. The system of partial differential equations is solved numerically using the normal mode analysis method and the required solution is found by applying the Galerkin method. The effect of heat transfer and concentration of micropolar liquid is obtained for (i) free–free, (ii) rigid–rigid, and (iii) rigid–free isothermal, permeable with no‐spin boundary conditions. The effect of different micropolar parameters (i.e., coupling parameter, micropolar heat conduction parameter, couple stress parameter, and inertia parameter) has been analyzed on the onset of stationary convection, and the results are depicted graphically. It is shown that different non‐uniform concentration gradients, diffusivity ratio, coupling parameter, and solutal Rayleigh number influence the heat transfer in the system. The phase of concentration flow for different boundary conditions is compared and analyzed.

Hybrid nanofluids development and benefits: A comprehensive review

Hybrid nanofluids (HNFs) have received the prominent attention of researchers due to their improved thermophysical properties than conventional liquids and single-phase nanofluids. Such high potential heat transfer fluids are obtained from the suspension of two or more dissimilar nanoparticles in a regular heat transfer liquid. Owing to the high heat transfer properties of hybrid nanofluid, these are widely used in industrial processes, manufacturing processes, and biomedical engineering. This framework presents a detailed review of hybrid nanofluids preparation, stability, thermophysical properties, and importance in various engineering fields. Furthermore, present analysis addresses the pH control and ultrasound intensity of hybrid nanofluid. This analysis also manifests a hybrid nanofluid preparation method and suitable nanoparticles mixers for various industrial uses. This study reveals some future trends and possibilities related to HNF and a few suggestions regarding the scope in the future research in this area. A big impact with small particles for coming years. The hybrid nanofluid are having higher thermal conductivity which affects significantly to machining output response variables. By hybridizing the suitable combination of nanoparticles, the required heat transfer effect can be obtained still at low particle concentrations.

Numerical Simulation Study on the Layered Phenomenon of Lakes and Reservoirs Destroyed by a Forced Circulation Device

Thermal stratification is a common phenomenon in lakes and reservoirs. It has a significant influence on water quality dynamics. The destruction of the thermal stratification of lakes and reservoirs can affect the water environment, improve the water quality and the water environment quality and prevent the occurrence of eutrophication. In this study, computational fluid dynamics (CFD) combined with a Eulerian two-phase flow model is used to predict the damage caused by an airlift device to the thermal stratification phenomenon of lake water. The results show that the two devices with different sizes can contribute to a certain exchange of kinetic and thermal energy, affecting the liquid velocity and temperature in the lake water under the condition of different gas velocities. Furthermore, the degree of damage to the thermal stratification phenomenon of lake reservoir is small. However, with the same gas velocity, the device with a guide plate can have a greater impact on the liquid velocity and temperature in the lake water. Further prediction results show that the airlift installed with a guide plate can affect the heat transfer of liquid in the lake and reservoir better and destroy the thermal stratification phenomenon effectively. The quantitative results of model prediction can provide an effective basis for future field scale-up experiments.

Hybrid heat transfer with falling film and pool boiling using R-134a outside a vertical tube

In this study, falling liquid film, pool boiling and hybrid heat transfer with refrigerant R-134a outside a vertical tube were experimentally investigated. A smooth tube and an enhanced tube specially designed for falling film were adopted for the tests. The results revealed that the heat transfer ratio of falling film to pool boiling gradually decreased as the heat flux increased for the two tubes. The heat transfer coefficients (HTCs) of falling film were smaller than those of pool boiling at a heat flux of 25 and 40 kW m−2 for the smooth and enhanced tubes, respectively. In the hybrid heat transfer mode analysis, it was observed that at a low heat flux, the HTCs of a completed falling film were higher than those of other heat transfer modes; moreover, the proportion increase of pool boiling led to a slight decrease in performance. However, at a high heat flux, a modest increase in the submerged height of the tubes in the refrigerant was beneficial for improving the performance, and the heat transfer had an optimal effect at the height of 800 mm and 600 mm for the smooth and enhanced tubes, respectively. Based on the experimental data, the heat transfer correlations of falling film combined with pool boiling at different submerged heights were obtained according to a dimensional analysis. The findings of the study serve as a guide for the design of vertical evaporators.

Performance study of heat and mass transfer in a counterflow liquid to air membrane-based parallel-plate dehumidifier

Liquid to air membrane energy exchanger (LAMEE) is the most important component in a liquid desiccant air conditioning system. Three main configurations of LAMEE are presented in the literature: co-current, counterflow, and cross-counter flow. In this paper, we evaluated the performance of a counterflow LAMEE dehumidifier in terms of its cooling capacity (CC) and moisture removal rate (MRR). A numerical model was developed and validated with experimental results. The impact of solution properties and inlet air characteristics on the LAMEE’s performance were investigated. Simulation results show that CC and MRR are enhanced by decreasing the temperature and increasing the concentration of the liquid desiccant simultaneously. In order to obtain an optimal performance of the LAMEE, the solution mass flow rate should be equal to or slightly higher than the inlet air mass flow rate. On the other hand, we found that both CC and MRR increase with increasing inlet air temperature and relative humidity. Even though solution properties and inlet air characteristics affect the MRR and the CC, they have a negligible effect on the required air sensible cooling to meet the supply air condition (Qsen). The characteristics of outlet air provided by the LAMEE are in a stable state condition, which proves that the LAMEE has a wide range of adaptability in different operating conditions.

Effects of inclination angle and heat power on heat transfer behavior of flat heat pipe with bionic grading microchannels

Bionic structure has become a popular tool to design heat pipes for its ability of heat transfer enhancement and liquid transport. Inspired by the powerful water collection and transfer capability of pitcher plant surface, this paper presents a new flat heat pipe design with bionic grading microchannels (BGFHP) based on special high-low structured surface. Firstly, the performance advantages of BGFHP are revealed by comparing the heat transfer performance and visible internal flow characteristics of BGFHP and conventional FHP. Secondly, the performance variation and influence trend of BGFHP are investigated experimentally with inclination angle and thermal power as variables. Finally, thermal management effects of natural cooling, FHP and BGFHP in fuel cells are compared to demonstrate the practical application of BGFHP. Results show that the high-low channel structure of BGFHP has the advantages of micro-channel hydraulic transport, and the small channel increases the heat transfer area, circulation efficiency and gas phase flow area, resulting in better start-up time and heat transfer capacity than the traditional FHP. The thermal resistance of BGFHP is reduced by 22%, while the thermal conductivity is increased by more than 40%. In the load range of 10–26 W and inclination angle range of 0–90°, the overall thermal resistance and temperature uniformity of BGFHP decreases and then increases as the inclination angle increases. With the increase of heat power, the thermal resistance of BGFHP gradually decreases, whereas the temperature uniformity first decreases and then increases. The optimal working condition of BGFHP is 45° and 24 W, with a minimum thermal resistance of 0.21 K/W. In the fuel cell temperature control test, the BGFHP was able to maintain the temperature below 52 °C, which is 5 °C lower compared to the FHP. This result shows the advantage of the BGFHP in terms of temperature control.

Surface film deformation by melt moving in an alternating magnetic field and the integral criterion of such film stability

The paper concerns some aspects of the induction melting technology improvement. The generalized mathematical model is presented which contains governing equations for the alternating magnetic field (AMF) diffusion into the liquid metal, heat and mass transfer in the melt and elastic deformation of the dielectric film covering partially the melt surface. The integral strain criterion is suggested which describes the total stress excited in the film by the melt motion. The model validation results are described. The influence of the film size on its stress–strain state is studied numerically for different values of external AMF frequency and strength. We calculate and classify realizable surface flow regimes depending on the AMF frequency and model, how this near-surface flow deforms the film of different sizes. An integral strain criterion is introduced, which lets to estimate the film break condition. The map of regimes is drawn which demonstrates the possible film radii at which the film does not break and does not deform depending on the AMF frequency and strength. It is shown, that integral strain criterion predicts well the film stress–strain state and conforms to the map of regimes. The results of numerical modeling, technique of the integral strain criterion calculation and examples of its application are given.

Turbulent heat transfer in a liquid metal tube flow with azimuthally inhomogeneous heat flux

An experimental study of the convective heat transfer in a turbulent liquid metal tube flow with azimuthally inhomogeneous heat flux is presented. Prior to the liquid metal experiments, the validation of the test section was realized using water. These results showed a very good agreement with literature data. For the liquid metal experiments, an eutectic alloy of gallium, indium and tin (GaInSn) was used. The Péclet number was varied between 1400 and 3600, thus in a regime of forced convection. Experiments with homogeneous heating over the full circumference of the tube and inhomogeneous heating over half of the circumference with the other half being insulated, were performed. The azimuthally averaged Nusselt number and the temperature distribution in the tube wall were investigated. The results suggest that the azimuthally averaged Nusselt number for water and liquid metal tube flows with inhomogeneous heating over the circumference can be calculated sufficiently well with literature correlations for uniform heat flux. For an inhomogeneous heat flux the azimuthal temperature gradient in the tube wall increases for higher Reynolds number and is more pronounced for GaInSn than for water. Furthermore, impurities like oxide particles significantly decrease the liquid metal convective heat transfer coefficient.

Impact of liquid coolant subcooling on boiling heat transfer and dryout in heat-generating porous media

The present article discusses the impact of liquid coolant subcooling on multiphase fluid flow and boiling heat transfer in porous media with internal heat generation. Although extremely relevant and important, only limited studies are available in the open literature on the effects of coolant subcooling in heat-generating porous media and hence, this requires a detailed analysis. The present analysis is carried out using a validated computational model of multiphase fluid flow through clear fluid and porous media considering the relevant fluid transport, heat transfer and mass transfer phenomena. Results suggest that the qualitative nature of boiling heat transfer from the heat-generating porous body, with subcooled coolants, remain similar to that observed with a saturated coolant. Quantitative differences are, however, observed as a result of solid–liquid convective heat transfer, and competing mechanisms of boiling and condensation heat transfer, when subcooled liquid coolant is present. It is observed that a substantially larger heating power density is required - as coolant subcooling is increased - for achieving the same temperature rise in the porous body. Dryout power density at different coolant subcooling is also observed to follow a similar trend. The thermal energy removal limit is, hence, observed to be substantially enhanced in presence of subcooled coolants. Further, the dryout region within the porous body is observed to gradually shift towards its interior as the coolant subcooling is increased.

A comprehensive review on computational studies of falling film hydrodynamics and heat transfer on the horizontal tube and tube bundle

Falling film evaporation is a promising technology widely applied in refrigeration, desalination and beyond applications owing to the great advantages. However, the liquid film hydrodynamics and heat transfer performance are studied insufficiently. Compered with experiments, numerical simulations are economical and efficient especially in the study of liquid film, through which some microscopic understandings are expected to be extracted. In this paper, a comprehensive review for a large pool of computational studies about falling liquid film flow and heat transfer on the horizontal tube and tube bundle is presented. Computational methods of liquid–gas two-phase flow and mass transfer model, as well as relevant researches were first introduced. Then, the studies on the falling film hydrodynamics, film thickness, sensible heat transfer, flow pattern, evaporation and boiling outside the single tube, tube bundle, special-shaped tube and entire evaporator studied with 2D and 3D models are respectively reviewed in order. Then, the investigations on the falling film breakout and dryout are reviewed. And then, the numerical predictions of falling film thickness and heat transfer coefficient are involved. Afterthat, the benchmark data for falling film numerical simulation are summarized. Finally, some future needs and recommendation relating to crucial technologies that must be solved are proposed.

Experimental Investigation of Plume Diffusion Behavior of LNG Accident Release Underwater

To deal with the significantly serious problem of environmental pollution, the use of clean energy is vigorously promoted by governments and corporations in all countries. Therefore, the offshore transportation and trade of LNG has become the main way of energy supplication in cross regional. The potential risk of LNG release from ships or offshore pipelines may cause disastrous consequences, which requires a better consideration and evaluation of the consequences of LNG accidental release. The main purpose of this paper is to understand the special physical phenomena of LNG underwater leakage and the dynamic behavior of rising plume. A small-scale indoor underwater leakage experimental platform was designed and built in a wind tunnel. The plume rising behavior of underwater release of the cryogenic liquid were recorded by a high-speed camera. Through the image processing techniques, the physical model of cryogenic liquid heat transfer underwater was established and verified. In addition, the effects of different sizes and pattern of the orifices and release pressures on plume radius were evaluated. An empirical relationship for predicting the plume diffusion radius under different pool sizes was established based on the method of dimensionless analysis.

Chemical compatibility of F82H and 316L in liquid metal heat transfer mediums Li, Na and NaK

Liquid metals Li, Na and NaK are the candidate heat transfer mediums which are installed in the irradiation capsule of advanced fusion neutron source. The compatibility issue of F82H and 316L in the candidate heat transfer mediums was studied by means of the corrosion tests at the temperature up to 823 K. The depletion of Cr, C and Fe from the steel was caused in liquid Li. The Li diffusion into the steel matrix was analyzed by TOF-SIMS. The corrosion in liquid Na was caused by the Na diffusion into the steel matrix and the surface oxidation. The corrosion in NaK was similar with that in liquid Na.

Heat transfer by liquid convection in particulate fluidized beds

In this work the theoretical model for heat transfer from a wall to a liquid-solid fluidized bed by liquid convective mechanism has been proposed and developed. The model is based on thickness of boundary layer and film theory. The key parameter in the model is the distance between two adjacent particles which collide with the wall. According to the proposed model, the liquid convective heat transfer in a fluidized bed is 4 to 5 times more intense than in a single-phase flow. Additionally, the wall-to-bed heat transfer coefficient has been measured experimentally in water?glass particles fluidized bed, for different particle sizes. Comparison of the model prediction with experimental data has shown that size of the particles strongly influences the mechanism of heat transfer. For fine particles of 0.8 mm in diameter, the liquid convective heat transfer model represents adequately the experimental data, indicating that particle convective mechanism is negligible. For coarse particles of 1.5?2 mm in diameter, the liquid convective heat transfer mechanism accounts for 60 % of the overall heat transfer coefficient.

Heat Transfer Analysis of the MHD Stagnation Point Flow of a Non‐Newtonian Tangent Hyperbolic Hybrid Nanofluid past a Non‐Isothermal Flat Plate with Thermal Radiation Effect

Heat transfer phenomena are used in a variety of industries, including chemical devices, shipbuilding, power plants, electronic devices, and medicinal plants. Propylene glycol, engine oil, water, and ethylene glycol are common single‐phase heat transfer liquids used in a variety of industries, including chemical process industries and thermal power plants. Therefore, the authors are interested in investigating the magnetohydrodynamic flow of a water‐based hybrid nanofluid containing ferrous and graphene oxide nanoparticles past a flat plate. The stagnation points, as well as the effects of magnetic field and thermal radiation are taken into account in this analysis. The non‐Newtonian tangent hyperbolic flow, which is laminar and incompressible, is also considered to investigate the non‐Newtonian behavior of the hybrid nanofluid flow. The proposed model has been solved analytically with the help of HAM. The convergence of HAM is shown with the help of figure. The hydrothermal characteristics of hybrid nanofluid flow past a nonisothermal flat plate at a stagnation point are affected by the necessary parameters. The results show that the boosting volume fractions of the ferrous and graphene oxide nanoparticles have significantly reduced the velocity field, while the thermal field has increased with the augmenting volume fractions of the ferrous and graphene oxide nanoparticles. The increasing power‐law index has augmented the viscosity of the non‐Newtonian hybrid nanofluid flow due to which the velocity field escalated. However, this impact is opposite for the thermal field. Due to the direct relation between the Weissenberg number and relaxation time, the greater Weissenberg number has reduced the velocity profile, while increased the thermal field.

Experimental study on thermal-mechanical properties of energy pile in saturated clay foundation

Based on the laboratory model test， the thermal-mechanical response of the energy pile in saturated clay foundation under multiple temperature cycles was studied. The temperature field around the pile， the settlement of pile and soil， the additional heating stress of pile and the shaft friction were analyzed. The results show that the temperature of pile and soil decreases along the depth and radial direction respectively， when the temperature rises. The settlement of pile top caused by cooling is greater than the expansion caused by heating. The heat transfer liquid was heated from 5 ℃ to 70 ℃， then maintained for 24 h， and then cooled to 5 ℃ for 5 h. This cycle for 3 times results in irreversible cumulative settlement of pile top. The settlement decreases with the distance from the pile， and the sedimentation rate of the soil decreases with the increase of the number of cycles. After three cycles， the settlement of soil surface 130 mm away from pile side reaches 1.42% of diameter of pile. The additional stress and the shaft friction of pile caused by temperature load increase gradually with the increase of temperature and number of cycles. The maximum additional heating stress reaches 695.40 kPa under working load， and the value varies with the change of pile top constraint condition， and its position moves gradually upward with the increase of the load on pile top. When heating， the negative shaft friction occurs in the upper part of the pile and the positive shaft friction occurs in the lower part. When cooling， the results are just the opposite. Under the action of the working load， the negative shaft friction area of the pile becomes smaller， and the zero-displacement point moves upward gradually. <fig fig-type="abstract-image" id="F1" orientation="portrait" position="float"><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="SP.J.1249-2022-39-1-85/9857FEDA-6661-4785-AADA-D5A71C0EB8A5-F001.jpg"/></fig>