Heat Storage Device Research Articles

MODELING THE DYNAMICS OF THERMAL ENERGY ACCUMULATORS AS CONTROL OBJECTS

The article defines the relevance of research on options for using heat accumulators in the heat supply system of industrial premises. Typical technological schemes of liquid heat accumulators are considered and shortcomings of existing mathematical models are determined. The technological scheme of a capacitive type battery is selected and analyzed, as the most common in solar heating and hot water systems. It has been established that for a non-stationary process, the thermal inertia of the body reinforcement and thermal insulation cannot be neglected, therefore, the storage tank cannot be considered as a single-capacity object. Based on the analysis of the heat balance of structural elements of heat storage devices, a mathematical model of the dynamics of the accumulator tank as a two-capacity object with lumped parameters is formulated. The resulting simplified mathematical model makes it possible to identify the simulation object (a capacitive type water accumulator). In the considered embodiment, the heat accumulator is used in hot solar water supply systems for preheating water. For use in dual-circuit systems of solar heating and hot water supply, heliolectors with antifreeze are used, and water is heated in heat storage tanks using heat exchangers. The formulated mathematical model of a tank of a combined accumulator with a heat exchanger when used as a liquid heat carrier - antifreeze (to exclude icing of the system), in which, to simplify the model (reduce the order), the heat capacity of the tubes is related to the heat capacity of the heat carrier in the volume of the tubes, and the mass of the body to the mass of liquid in it . For the development and analysis of an automatic temperature control system, the obtained models are a system of nonlinear equations, the solution of which is advisable to carry out in computer environments.

Active thermal insulation method based on the principle of source-sink matching

To reduce the heat consumption and improve the energy efficiency of the heat storage system, this paper puts forward a method of active thermal insulation in the thermal energy storage system. A heat source area for absorbing surplus heat is set in the heat insulation process, whose heat is transmitted to the heat sink area. And the source-sink matching strategy is discussed. Theoretically, this system can achieve reasonable heat distribution and thermal insulation at the same time. In this work, the water heater is selected as a typical heat storage device, and the theoretical method is verified by designing an active insulation device in the water heater. The results show that a low-temperature zone is generated in the water heater as a result of the active thermal insulation device, which reduces the external heat dissipation. At the same time, the installation position of the radiator is conducted through energy level and exergy analysis. The studied case shows that the energy level matching coefficient of the novel water heater system can reach 0.49 and the exergy efficiency can be increased to 24% compared to a conventional system. The active thermal insulation method is expected to provide an effective energy-saving idea for a variety of heat storage systems.

An experimental and analytical study of solidification around an array of horizontal cylinders subjected to free convection flow

In this paper the solidification of a liquid around an array of cooled horizontal cylinders has been investigating experimentally and analytically. The horizontal cylinders can be arranged in various configurations. In this paper one typical example for such a configuration is studied. This is a cyclic system cylinders with cylinders of a diameter of 54 mm a length of 1793 mm and a spacing between them of 100 mm. The cylinders are arranged in an equilateral triangular array. The theoretical part of the paper deals with a simplified solution of the problem of liquid solidification around the horizontal cylinders under the influence of a free convection flow. A simple quasi steady-state model for the solidification process is derived. The model describes the phase change phenomenon with an imposed boundary condition on the solidification front which assumes a distribution of the heat transfer coefficient from the surrounding free convection flow. The simplified theoretical model, which is based on the Happel-Brenner cell method, can be used for a fast preliminary design of latent heat storage devices. In addition, the model considers the effect of a contact layer between the cooled cylinders and the surrounding ice layers. It can be shown, that the solution of the problem can be reduced to the solution of a system of integro-differential equations, which has been solved numerically. In the experimental part of this work, the thickness of the solidified layer was measured by using a newly built test apparatus. Both, the thickness of the solidified layer and the average liquid temperature depend on time. The local heat transfer coefficient at the solidification front was also determined experimentally. Experiments have been done with timely varying fluid temperatures between 293 K to 274 K. The experimental results are found in good agreement with the theoretical model for the obtained results for time dependent thickness of the frozen crust.

Reactive Grand-Canonical Monte Carlo Simulations for Modeling Hydration of MgCl2.

Thermochemical heat-storage applications, based on the reversible endo-/exothermic hydration reaction of salts, are intensively investigated to search for compact heat-storage devices. To achieve a truly valuable storage system, progressively complex salts are investigated. For these salts, the equilibrium temperature and pressure conditions are not always easy to predict. However, these conditions are crucial for the design of thermochemical heat-storage systems. A biased grand-canonical Monte Carlo (GCMC) tool is developed, enabling the study of equilibrium conditions at the molecular level. The GCMC algorithm is combined with reactive force field molecular dynamics (ReaxFF), which allows bond formation within the simulation. The Weeks–Chandler–Andersen (WCA) potential is used to scan multiple trial positions for the GCMC algorithm at a small cost. The most promising trial positions can be selected for recomputation with the more expensive ReaxFF. The developed WCA–ReaxFF–GCMC tool was used to study the hydration of MgCl2·nH2O. The simulation results show a good agreement with experimental and thermodynamic equilibriums for multiple hydration levels. The hydration shows that water, present at the surface of crystalline salt, deforms the surface layers and promotes further hydration of these deformed layers. Additionally, the WCA–ReaxFF–GCMC algorithm can be used to study other, non-TCM-related, reactive sorption processes.

Studies on performance enhancement of heat storage system with multiple phase change materials

This paper aims to improve the heat storage system's performance by using multiple phase change materials (PCMs). A heat storage device is designed with multiple PCMs firstly. The heat storage device consists of three identical shell-tube phase change thermal storage units. The numerical method is developed and verified experimentally. Two parameters, namely the latent heat utilization of PCM (ω) and the heat transfer effectiveness of heat storage device (ε), are introduced to evaluate the performance of energy storage and the heat exchange of the heat storage system with multiple PCMs. The effects of factors on ω and ε are studied, including the thermal conductivity, latent heat and melting temperature difference of PCMs, and the inlet velocity and temperature of heat transfer fluid. Results indicate that increasing the inlet velocity and temperature of HTF can greatly improve ω, but reduce ε. Increasing the thermal conductivity of PCM can obviously improve ω, but it has little effect on improving ε. Multiple PCMs with suitable melting temperature difference can improve both ω and ε. In practice, multiple PCMs can be associated with the above methods to improve the overall performance of the phase change thermal storage system. This research is used to optimize the design of phase change thermal storage device and improve its performance.

Study on the performance of Double-pipe phase heat exchangers in waste heat recovery with heat storage and discharge

The heat transfer performance of the double-pipe phase change heat storage and exothermic device and its cycle system for waste heat recovery was studied experimentally. 10 different experimental conditions were set by adjusting the inlet temperature, inlet flow rate and heat storage time of the phase change heat storage and exothermic device to study the changes of the outlet temperature, heat exchange and the inlet and outlet temperature of the heat sink of the heat-using device. The experimental results show that the higher the inlet temperature, the higher the flow rate and the longer the heat storage time, the higher the average heat exchange and the longer the heat release time of the heat exchanging device. The phase heat exchanger designed and used in this experimental research provides a certain experimental basis and data reference, which can be used for waste heat recovery in industrial and other fields.

Experimental Analysis on Heat Release of Pulsating Heat Pipe Phase Change Regenerator with Different Working Fluids

In order to improve the problems of serious energy waste and low utilization rate, this paper designs and builds an experimental platform for a pulsating heat pipe type phase change heat storage device. The temperature changes with time in the heat storage and release device of the barium hydroxide octahydrate phase change material under different working conditions is studied. The results show that during the heat release process, when the pulsating heat pipe is filled with water, the cooling water temperature rises to the highest, and the heat recovery rate is as high as 64%. Otherwise, the initial temperature of the cooling water during the heat release process is studied. Result shows that the initial temperature of the cooling water increases, the longer the latent heat of phase change and the total heat release time, and the higher the temperature rise of the cooling water. The experimental design of this paper can provide a reference for researchers in related fields.

Experimental Research of the Heat Storage Performance of a Magnesium Nitrate Hexahydrate-Based Phase Change Material for Building Heating

Phase change heat storage material is a preferred material in solar building heating or off-peak electric-heat storage heating technology and is the research focus. A compact phase change thermal storage device has been designed and experimentally studied for improving heating system load in this work. A new type, magnesium nitrate hexahydrate-based phase change material has been studied to improve the cooling degree and crystallization difficulty. The focus of this study is on the heat charging and discharging characteristics of this new phase change material. The heat storage device has two groups of coils, the inner side which carries water and the outer side which is the phase change material. A testing system was built up to value the thermal cycling performance of the heat storage device. The measurement data include phase change material temperature field, water inlet and water outlet mean temperature, heat charging and heat discharging depth, and flow rates over the operating period. The results show the phase change material has a quick response with the operating temperature range of 20–99 °C. Its latent heat is 151.3 J/g at 91.8 °C. The heat storage density of this phase change material is about 420 MJ/m3. The thermal performance degradation is about 1.8% after 800 operation cycles. The phase change thermal storage device shows flexibility and a great potential to improve the capacity and economy of heating systems.

Study of the corrosion of stainless steel with fatty acid/paraffin/graphite composite phase change materials

The corrosion performance of phase change materials on stainless steel was studied using single fatty acid, fatty acid/paraffin mixed phase change materials and fatty acid/paraffin/graphite composite phase change materials as corrosion media. The results show that the corrosion of fatty acid, paraffin and graphite composite phase change materials to stainless steel is very small; among them, stearic acid series of phase change materials are the least corrosive and can be used as the ideal energy storage medium for stainless steel phase change heat storage and heat exchange devices.

Effect of Flow Channel Cross Section Shape on the Performance of Heat Storage Structure

A numerical simulation is carried out for the thermal storage process in a heat storage device with magnesia bricks as thermal energy storage medium. Three types of cross section shapes (square, hexagon, circle) of the flow channel are considered with the inlet air temperature as high as 1023K. The perssure drop, temperature distribution and temperature uniformity of the flow channel are obtained. The results show that the pressure drop of the flow channel with circle cross section is the lowest when the Reynolds number is less than 2300 (in this case the inlet velocity is 5m/s), While when the Reynolds number is more than 2300, the flow channel with square cross section has the lowest pressure drop. The thermal storage time of the heat storage device decreases with the increase of air velocity. The temperature distribution of the flow channel indicates that the flow channel with hexagon cross section has the best comprehensive performance.

Combined dryer with high efficiency for drying high-moist agricultural products

The article discusses a two-chamber solar-fuel drying plant for drying various agricultural products, a distinctive feature of which is the presence of a water jacket and a rubble heat accumulator. Two electric heaters are recommended as heat sources of the dryer: the first is the main one and the second is intermediate. It was found that during daytime operation, solar radiation enters the surface of the drying chambers, and it heats the water in the jacket from 30 ° C to 65 ° C. The latter, in turn, through the chamber wall gives up its heat to the air flow circulating in the chamber space. At night, some of the heat is compensated by the heat accumulated in the water jacket and in the rubble heat accumulator. For rational and energy-saving operation of the drying plant, the modes of power regulation of electric heaters by means of a thyristor regulator have been substantiated. This can save up to 30% of the main power consumption. The paper provides a detailed analysis of the thermal and technical calculations of a rubble heat accumulator and a water jacket, and also determines the charging and discharging times of heat storage devices.

Implication of Bio-convective Marangoni flow of non-Newtonian material towards an infinite disk subject to exponential space-based heat source

In recent years, the research for enhanced thermal transportation is centered around the utilization of nanostructures to avail the prospective benefits in areas of biomedical, metallurgy, polymer processing, mechanical and electrical engineering applications, food processing, ventilation, heat storage devices, nuclear systems cooling, electronic devices, solar preoccupation, magnetic sticking, bioengineering applications, etc. The thermal aspects of nanoliquids and associated dynamics properties are still necessary to be explored. In this thermal contribution, the flow of Casson nanofluid configured by an infinite disk is analyzed. The significance of Marangoni flow with activation energy, thermal and exponential space-dependent heat source, nonlinear thermal radiation and Joule heating impacts is also incorporated. Similarly, variables are affianced to recast the governing flow expressions into highly coupled nonlinear ODEs. The numerical simulation for the prevailing model is elucidated by applying the bvp4c built-in function of computational commercial software MATLAB. Consequences of sundry parameters, namely, magnetic parameter, Prandtl number, radiation parameter, exponential space-dependent heat source parameter, thermal-dependent heat source parameter, Eckert number, Dufour parameter, Soret number, Schmidt number, Marangoni number and Marangoni ratio parameter, mixed convection parameter, buoyancy ratio parameter, bioconvection Rayleigh number, activation energy parameter, thermophoresis parameter, Brownian motion parameter, bioconvection Lewis number, Peclet number microorganisms difference variable versus involved flow profiles like velocity, temperature, concentration of nanoparticles and microorganism field are obtained and displayed through graphs and tabular data.

High Temperature Insulation Design of Capacitive Wall Bushing for High-temperature Solid Electrical Heat Storage Devices

The temperature resistance and voltage level of the wall bushing are the key factors restricting the increase of the heat storage capacity of the solid electrical heat storage device. Therefore, by studying the electrical insulation and heat insulation principles of the wall bushing of the solid electrical heat storage device, a new type of capacitive solid electric heat storage device wall bushing suitable for 66∼500 kV high voltage and 800 °C high temperature was designed, and its internal insulation parameter calculation method considering the influence of high temperature was proposed. The analysis of the bushing through the multi-physics coupling field of temperature field, force field and electric field shows that high temperature deformation does not affect the electrical insulation of the capacitor core. However, in order to reduce the pressure of the outer insulation layer of the bushing, a deformation margin of 3% of the radius of the ground electrode plate still needs to be left. The change of relative dielectric constant will enhance the field strength at the edge of the capacitor core plate and deteriorate the electric field distribution of the bushing. Therefore, when calculating the internal insulation, it is necessary to set a partial discharge calculation margin of 1.4 times and the ratio of the length of the internal and external steps of the capacitor core furnace to 86%. As the voltage level increases, the effect of high temperature on the electric field distribution of the bushing becomes weaker.

Thermal conditions of Adsorptive heat storage device operating in open-mode for heating inflowing air

Thermal conditions of adsorptive heat storage device operating in open-mode were considered when discharged. The main operating parameters affecting the final temperature of airflow which supplied to ventilated premises are determined on the example of heat storage device based on composite ‘silica gel – sodium sulphate’. The main factors which determine a final airflow temperature are confirmed to be initial values of temperature, absolute humidity and speed of airflow which fanned to the adsorbent layer. Algorithm of calculating the operational parameters of adsorptive heat storage device has been further developed. Proposed algorithm involves calculation of diffusion coefficient, mass transfer coefficient, final absolute humidity of airflow, volume of air which passed through adsorbent layer, adsorption, specific adsorption heat and final airflow temperature, then useful heat, heat inputs for operating heat storage device and its efficiency factor are estimated. The adequacy of the proposed algorithm has been confirmed according with experimental data for operating of open mode adsorptive heat storage device. Curves final temperature of inflowing air vs. time of discharge of heat storage device are stated to depend on characteristics of airflow which fanned to the adsorbent layer such as temperature, speed and initial absolute humidity. When these parameters increased, time to achieve plateau, i.e. maximal values of final inflowing air temperature decrease. The dependence of initial values of temperature, absolute humidity, speed of humid airflow and final airflow temperature is shown. Maximal temperatures of at most 65 – 80 ºC are stated at the initial temperatures and absolute humidity of initial airflow within the ranges of 20 – 30 ºC and 0.03 – 0.04 kg/m3, respectively. The results of the present study can be used for the development of energy-efficient systems and devices for air-conditioning in habitual inner space and warehouses.

Magnetized bioconvection flow of Sutterby fluid characterized by the suspension of nanoparticles across a wedge with activation energy

AbstractNanofluids are playing a vital part in advancing practical life. The potential application of nanomaterials in a multitude of scenarios, such oil recovery, the melting of electronic systems in computers, cooling systems, the construction of fluid, cooling spirals, engineering and manufacturing, heat storage devices, and bioengineering. The microorganisms have a vital role to play in numerous applications, such as biological sciences, drugs, and biotechnology, biofuels processing, wastewater treatment, and food production. The current investigation exhibits a numerical model for Sutterby fluid with activation energy, thermal radiation, and bioconvection flowing past a stretching/shrinking wedge. The set of conservative governing partial differential equations (PDEs) is converted into a dimensionless ODEs system by using suitable similarity variables. The obtained new system of the model with dimensionless relative boundary conditions is tackled numerically by manipulating the famous shooting method through bvp4c solver in MATLAB coding. The physical and mathematical findings for profiles of velocity, temperature, concentration, and microbe dispersion owing to various controlling parameter inputs are displayed in tables and graphs. Flow velocity is shown to decrease as the bioconvection Rayleigh number increases. Moreover, the Prandtl number increases, the thermal field of the fluid decreases while it increases for the temperature ratio parameter. Furthermore, it is determined from this situation that the concentration field decreases as the Brownian motion parameter increases. The field of the microorganism decreases as the Peclet number increases.

Thermo-bioconvectional transport of magneto-Casson nanofluid over a wedge containing motile microorganisms and variable thermal conductivity

Nanofluid is one of the wide elaborate technologies in thermal engineering sectors due to its broad solicitations such as, heat exchanger, treatment of cancer, heat storage devices, biomedicine, biotechnology, which is utilized to develop the heat transport rate of heat storage in different devices. Improvement of thermal conductivity using nanoparticles is one of the challenges in these implementations of nanofluids. The aim of this scrutiny is to illustrate bio convectional 2D Casson flow of nanofluid in the existence of swimming gyrostatic microorganisms over stretching wedge. Brownian and thermophoritic diffusions are employed. Influences of thermal radiation, variable thermal conductivity, activation energy with thermal and solutal Robin conditions are taken into account. The conversion of formulated nonlinear system of partial differential equations (PDE’s) into structure of ordinary differential equations (ODE’s) is done through suitable dimensionless variables. The rendered governing coupled equations are computed numerically by using the bvp4c technique. The spectacular effects of interesting numbers against the velocity, the temperature, the concentration and the microorganism fields are analyzed in detail and elaborated through figures. Key outcomes are mentioned. From this analysis, it is noted that solid particles improve the thermal efficiency of base fluids. Velocity of liquid enhances via mixed convection parameter. Temperature distribution rises for larger thermophoresis parameter. The growing bioconvection Lewis number declines the concentration of microorganism. The current outcomes may help in industrial applications. The current work has many implementations in different engineering fields, biotechnology, nanotechnology and medical sciences.

Interconnected-energy hubs robust energy management and scheduling in the presence of electric vehicles considering uncertainties

Energy hubs as a multi-carrier energy system with various energy carriers and conversions have been integrated with smart grids to increase the efficiency, flexibility, and reliability of the network. Today, scheduling multi-energy hubs (MEH) is one of the challenging issues in smart grids. In this paper, the optimal schedule of interconnected MEHs based on the robust optimization in the presence of electric vehicles (EVs) is proposed. A robust optimization approach is considered to deal with uncertainties of electrical price, renewable energy resources (RESs) generations, and electrical loads. In this paper, MEHs network include commercial, industrial, and residential energy hubs. The energy consumption of MEHs consist of electrical, water, gas, and heat. RESs, demand response (DR) programs, heat and electrical energy storage devices are used to supply the energy demand. The aim of the proposed model is reducing the total cost of operation and carbon emission. The price-based demand response program is applied to shift the power consumption from on-peak to off-peak times in response to the price signal. Finally, the problem is solved for the three cases with CPLEX under YALMIP MATLAB. The results illustrate the effectiveness of the proposed model to achieve optimal scheduling of MEHs. The proposed problem is organized in three scenarios, among which the scenario I determines optimal scheduling of MEHs, using robust optimization method. The scenario II investigates the problem with deterministic model. The scenario III evaluates the problem applying robust optimization method without DR program and energy storage device consideration in autonomous EHs. The numerical results show that the total operation cost is increased 15.46% in scenario I compared with the scenario II due to applying the worst-case of uncertainties in robust optimization approach.

Station-grid Co-planning of Integrated Energy System with Consideration of Multi-energy storage and Reliability Cost

In order to improve the reliability of integrated energy system, the station-grid co-planning model and its solution method are proposed. The planning model considers the constraints of distribution network, gas distribution network, heat distribution network and energy station, and aims at minimizing the total planning cost within the planning period including investment cost, maintenance cost and reliability cost. It realizes the optimal planning for the types and locations of energy supply sources, distribution pipelines, energy stations and energy storage devices, such as electricity storage devices, gas storage devices, heat storage devices and cooling storage devices. The model is a mixed integer quadratic programming problem, which is solved by Gurobi. The case study uses the modified electricity-gas-heat integrated energy system to analyse the system planning scheme and planning cost under two scenarios. The results show that the proposed model can reasonably plan the integrated energy system and further improve the reliability of the integrated energy system.

Performance analysis and optimal charging time investigation of solar air heater with packed bed sensible heat storage device

The amount of stored thermal energy and the stratification in the packed bed thermal energy storage systems decrease in the afternoon because of the reduction in the solar power and solar-air heater panel's collector outlet temperature, so the charging process must be ceased at a particular instant. The optimal charging period is determined by considering the degree of stratification, energy/exergy stored, and the energy discharged during the 6 h of space heating. The proposed packed bed is divided into three sections lengthwise. Different bed materials have been placed separately in these regions regarding their volumetric heat capacity to promote stratification and sensible heat storage during charging. The bed's stratification level is determined via an exergy analysis to evaluate the discharge efficiency of the bed. The particle diameter and discharge air velocity on the system's thermal and hydrodynamic performance are inspected. The fan energy consumption during the discharge process is evaluated in the analyses. Distinctively, the air velocity is varied to obtain a minimum heat load of 18 kW for 6 h discharge process. A transient, one-dimensional finite-difference model is developed and validated with an experimental study conducted in the literature. Thermal energy storage and the stratification level are improved thanks to segmented bed by 85% and 135%, respectively.

Numerical simulation for bio-convective flow of Sutterby nanofluid by a rotating disk

Nanofluids play a vital role in the improvement of our practical life. The potential usage of nanomaterials in different applications such as oil recovery, refrigeration systems, a freeze of electrical components in computers, development of liquid displays, cooling spirals, mechanical engineering, electrical engineering, heat storage devices and biotechnology. Swimming microorganisms have a crucial role in various areas of life, such as medicines, bioengineering, biofuels and food processing. Microorganisms are used as antibiotics in medicine and help to create a vaccine. Keeping in mind these applications, the current research provides a mathematical model for bioconvection Sutterby nanofluid flowing past the rotating stretching disk with magnetic field, motile microorganisms, chemical reactions and heat generation. The Brownian movement and thermophoresis diffusions are also considered. The governing equation structures are simplified by suitable transformations. A popular bvp4c solver in MATLAB computational software is employed to achieve numerical results for the non-linear model. The flow evaluation for the effects of several prominent numbers on temperature, velocities, concentration and motile microorganism profiles is executed graphically and numerically. The volumetric concentration of nanomaterial rises for thermophoresis number while shows opposite nature for Prandtl and Lewis parameters. The boosting values of bioconvection Lewis number, Peclet number and bioconvection Rayleigh number decay the motile microorganisms’ concentration.