Effect Of Heat Storage Research Articles

Combustion Kinetics Characteristics of Solid Fuel in the Sintering Process

In order to systematically elucidate the combustion performance of fuel during sintering, this paper explores the influence of three factors, namely coal substitution for coke, quasi-particle structure and the coupling effect with reduction and oxidation of iron oxide, on fuel combustion characteristics, and carries out the kinetic calculation of monomer blended fuel (MBF) and quasi-granular fuel (QPF). The results show that replacing coke powder with anthracite can accelerate the whole combustion process. MBF and QPF are more consistent with the combustion law of the double-parallel random pore model. Although the quasi-particle structure increases the apparent activation energy of fuel combustion, it can also produce a heat storage effect on fuel particles, improve their combustion performance, and reduce the adverse effect of diffusion on the reaction process. In the early stage of reaction, the coupling between combustion of volatiles and reduction of iron oxide is obvious. The oxidation of iron oxide will occur again when the combustion reaction of fuel is weakened.

Effect of regeneration heat and energy storage on thermal drying performance in a hardwood solar kiln

The use of energy efficiency tools and solar energy in wood drying can help reduce the often heavy energy consumption of industrial dryers. The rational management of energy in terms of drying has attracted a lot of attention and the main objective of this work is to adapt the techniques of renewable energy and energy saving in solar kilns. The present work is therefore a contribution to the improvement of energy efficiency and the modeling of a solar wood kiln with thermal storage and heat regeneration. The drying system consists of five main units, a drying chamber, a multi-pass solar air collector, a cylindrical parabolic solar collector, a thermal storage tank and a Closed Feed Air Heater. The investigation carried out in this work is based on the establishment of mass and energy conservation equations in different components of the drying system. The governing equations of heat and mass transfer are solved using the implicit finite difference method. The discrepancies between the experimental and numerical results do not exceed 5%. The results show that the drying time is shorter in June and longer in December. The drying time decreases as the collector area increases and the boards thickness decreases. By incorporating a Closed Feed Air Heater with an effectiveness of 0.75, in the solar dryer, the collector and drying efficiency values are increased from 0.48 to 0.56 and 0.43 to 0.88, in June, respectively. The integration of the thermal storage unit in the solar kiln has the effect of reducing the drying time up to 40 and 60%, in June and December, respectively. Moreover, the combined use of thermal storage and regeneration heat is efficient in reducing the energy consumption ratio (kWh.m−3) up to 50% and 54%, in June and December, respectively. The proposed solution can significantly improve thermal drying performance and thus overcoming the problem of longer drying time, especially in winter.

Thermal Response Characteristics of Intermittently Cooled Room with Tube-Embedded Cooling Slab and Optimization of Intermittent Control

The heat storage effect of the tube-embedded slab cooling system (TESCS) makes the intermittent operation feasible, a reasonable intermittent strategy can fully realize the energy saving effect. This paper purposes to optimize the intermittent control schemes for TESCS by simulation. The response of the thermal environment intermittently cooled by TESCS is firstly studied. Then, the intermittent control schemes of TESCS are studied. On the basis of the dual-objective optimization for thermal comfort and energy efficiency, the optimal scheme is established. The results show that the tube-embedded slab has significant heat storage and release characteristics under intermittent cooling condition. Its maximum cooling capacity appears about one hour after the stop of cooling. Reducing the cooling duration can reduce the system energy consumption, but increasing the cooling duration can reduce the system peak load. Twenty-four-hour cooling can reduce the peak load by about 70%, 67%, and 41%, respectively, compared with 6-h, 8-h, and 12-h cooling. The effect of the cooling duration on the thermal comfort and energy efficiency is much greater than the cooling time distribution. Frequent starts and stops of the pump can increase the cooling capacity obtained by the room to a certain extent. Daytime cooling provides higher comfort and energy efficiency while night cooling can reduce the chiller’s peak cooling requirement by about 25%.

The effect of heat storage on supercritical flow stability in two heated parallel channels

One-dimensional (1-D) numerical simulations were carried out of two vertical heated parallel- channel experiments using a linear frequency domain approach to investigate the wall energy storage effect on the system's stability boundary for supercritical water up-flow. Oscillatory instability boundaries of the experimental cases with two different wall thicknesses, uniform and non-uniform power distributions are produced, assessed and discussed. In all, 31 cases were examined. These instability predictions with wall energy storage effects are compared with experimental data and other numerical results obtained without wall heat effects. There is improved agreement on the stability boundary predictions when the wall energy storage effect is included; however, all results fall within the experimental uncertainty. There is a cancellation effect of the wall energy storage in two parallel channels compared to a single channel. Consequently, the effect of wall energy storage is relatively small for the experiments modeled.

The effect of heat storage to properties and energy recovery of pyrolysis products from agricultural waste

The pyrolysis process is the conversion of a biomass into biofuel but the process requires a high amount of external heat in order to increase the temperature of raw material which affects the production costs and energy efficiency. The effect of heat storage to control a temperature on the shell of pyrolysis reactor for the properties and energy recovery of pyrolysis products were considered in this study. Agricultural waste drop tube pyrolysis reactor that was designed into double layer shell wall to contain ceramic bead for heat storage. The parametric test of this study as temperature (350 °C – 550 °C), and biomass type (corncob, coffee grounds and coffee husk) were investigated. This result showed that, the heating rate of the reactor when starting to the setting temperature of the comparison testing (CT) was lower than that of the heat storage testing (HT). It indicated that the energy input for the reactor in case of HT was lower than that from CT. The yield of bio-oil and bio-char of the HT were lower than that of the CT in the same pyrolytic temperature. When increasing temperature for 350 °C to 550 °C effected to decreasing the yield of bio-char while the maximum yield of bio-oil found in the temperature of 450 °C. The heating value of pyrolysis products were increased in the higher temperature. The bio-fuel products from corncob had the higher heating value (HHV) and the energy recovery higher than that from another biomass.

Thermal Characterization of Pinus radiata Wood Vacuum-Impregnated with Octadecane

The incorporation of phase change materials (PCM) in construction components has become an alternative to reduce the effect of thermal loads in buildings with low thermal inertia. This study put together the effective heat storage capacity of an organic phase change material (O-PCM, octadecane) with the construction and production potential of Pinus radiata in Chile. The wood is impregnated with octadecane by using the Bethell method, showing that it has good retention of the impregnator, and that its size was not modified. Differential scanning calorimetry analysis (DSC) showed that the composite material could achieve fusion enthalpy values from 36 (20.8 MJ/m3) to 122 J/g (108.9 MJ/m3). The transient line heat source method used, indicated that impregnation of Pinus radiata with octadecane increases its specific heat at temperatures from 15 to 20 °C, while its thermal conductivity decreases in the radial and the tangent directions, and increases in the longitudinal direction, showing a decrease in the orthotropic behavior of the wood. The ability of Pinus radiata wood to store latent heat positioned it as a candidate material to be considered in the building industry as a heat storage system.

Multi-objective optimization of thermal performance of packed bed latent heat thermal storage system based on response surface method

In this study, a simplified numerical model was developed to calculate the internal thermal distribution rules and thermal performance index of a packed bed latent heat thermal storage system (PBLHTES). The accuracy of the model was verified by comparing numerical results with experimental data. The response surface method (RSM) was applied to study and optimize the thermal performance of the PBLHTES. The quadratic regression model of three response indices was established based on 130 groups of Box–Behnken design (BBD) model scheme results, and rationality was verified through analysis of variance (ANOVA). The results showed the degree of influence of single factors and interactive factors on each performance index. The combined effect of the main interactive factors was analyzed in detail. The multi-objective optimized results indicated that effective heat storage time, effective heat storage, and exergy efficiency decreased by 30.24%, increased by 39.81%, and improved by 7.50%, respectively, compared with the basic working conditions before optimization.

Analysis of the reliability of heat supply from hybrid energy source based on WPP and CHPP

The paper is devoted to the problem of the reliability analysis the functioning of the hybrid energy source based on the wind power plant (WPP) and the combined heat and power plant (CHPP). The main effect of the proposed technology is substituting a part of the fossil fuel used at CHPP (or other heat sources) for the production of electricity and thermal energy. At the same time, CHPP operates according to the heat schedule, i.e. in accordance with changes in the heat loads of consumers. In this regard, the attention in the study is focused on the problem of the reliability analysis of the heat supply (heating) from a hybrid energy source. To assess the reliability of heat supply, one of the main complex reliability index (RI) is used - the availability factor (AF), and the system of equations of a stationary markov process is used as a mathematical model of the states evolution of the studied object. Calculation of AF is made in accordance with seasonal changes in heat loads (annual heat load schedule); the heat storage effect of consumers (thermal inertia) and the factor of a possible decrease in wind speed are also additionally taken into account. Case study is carried out on a test circuit of the hybrid energy source (WPP+CHPP), as a result of which some analytical characteristics are obtained.

Heat storage effect of the operative temperature in PASSOL laboratory

In different Comfort Standards, for different building functions the requirements for summer and also for winter period differ. The operative temperature is one of these parameters, which in different Comfort Standards for summer-winter period specifies the building's comfort category. This paper presents the results of measurement of the operative temperature in PASSOL laboratory with different heat storage and using night ventilation.

Effect of the ground heat storage on solar chimney power plant performance in the South of Tunisia: Case of Tozeur

In this paper, the ground heat storage effect on the performance of a SCPP implemented in the South of Tunisia, is investigated. First, a 3D CFD ANSYS-Fluent model is used to study the SCPP performance in the region of Tozeur, which represents the best location in the country, in terms of energy production for a SCPP. Such an installation with a geometry similar to the Manzanares plant, can produce averagely around 150 MWh/year of electrical energy. Subsequently, the study of the effect of the thermal storage on the SCPP performance is presented using an in-house code. In this model, a two-dimensional cylindrical domain is used for the transient conduction in the ground and 1D buoyancy driven flow for the air flow. Such a modeling approach is much more efficient that the full conjugate heat transfer CFD solution obtained through ANSYS-Fluent CFD software and enables the simulation of long term transient behavior. Moreover and for more realistic results, the model uses real weather data for wind speed, ambient temperature and solar radiation. With this model, the performance of three types of ground storage media are investigated. Results show that the ratio between the released and stored energies depends mainly on the season and the energy production is increased by about 35% compared to a system without storage. The results demonstrate the importance of including long-term thermal storage when modelling SCPP.

Hygrothermal Properties of Raw Earth Materials: A Literature Review

Raw earth historic and contemporary architectures are renowned for their good environmental properties of recyclability and low embodied energy along the production process. Earth massive walls are universally known to be able to regulate indoor thermal and hygroscopic conditions containing energy consumptions, creating comfortable interior spaces with a low carbon footprint. Therefore, earth buildings are de facto green buildings. As a result of this, some earthen technologies have been rediscovered and implemented to be adapted to the contemporary building production sector. Nevertheless, the diffusion of contemporary earthen architecture is decelerated by the lack of broadly accepted standards on its anti-seismic and thermal performance. Indeed, the former issue has been solved using high-tensile materials inside the walls or surface reinforcements on their sides to improve their flexural strength. The latter issue is related to the penalization of earth walls thermal behavior in current regulations, which tent to evaluate only the steady-state performance of building components, neglecting the benefit of heat storage and hygrothermal buffering effect provided by massive and porous envelopes as raw earth ones. In this paper, we show the results of a paper review concerning the hygrothermal performance of earthen materials for contemporary housing: great attention is given to the base materials which are used (inorganic soils, natural fibers, and mineral or recycled aggregates, chemical stabilizers), manufacturing procedures (when described), performed tests and final performances. Different earth techniques (adobe, cob, extruded bricks, rammed earth, compressed earth blocks, light earth) have been considered in order to highlight that earth material can act both as a conductive and insulating meterial depending on how it is implemented, adapting to several climate contests. The paper aims to summarize current progress in the improvement of thermal performance of raw earth traditional mixes, discuss the suitability of existing measurement protocols for hygroscopic and natural materials and provide guidance for further researches.

Critical comparison between thermal performance test (TPT) and thermal response test (TRT): Differences in heat transfer process and extractable information

In the field of ground-source heat pumps (GSHPs), thermal response tests (TRTs) with constant heat rate have been conducted to estimate the design parameters of ground heat exchangers (GHEs), and thermal performance tests (TPTs) with constant inlet temperature have been conducted to examine the heat exchange performance of GHEs. These two experimental methods have been discussed insufficiently, and therefore, they are sometimes perceived as completely different experiments with mutually exclusive extractable information. However, both methods provide similar information, although there are differences in the heat transfer process. For better understanding these two methods and extending the utilization potential of TPT and TRT data, this study analyzes and discusses the following two issues using numerically generated datasets: (1) differences in heat transfer process between TRTs and TPTs and (2) effect of different physical processes on the extractable information and its accuracy, such as the ground thermal conductivity, borehole thermal resistance, unit heat exchange rate, and transient ground thermal resistance. From the viewpoint of the heat transfer process, we found that the GHE’s heat storage effect disappears faster in TPT than in TRT. When estimating ground thermal properties, this difference allows the TPT to be more accurate with shorter experiment time than the TRT. Additionally, we found that the TRT overestimated the GHE thermal performance compared to the TPT. However, when the heat storage effect was removed, both methods provided almost identical results. A comparison of experimentally obtained ground thermal resistances, which are required in the ASHRAE design method, with those obtained from the infinite cylindrical source model indicated that the TPT showed discrepancy rates less than ±8% whereas the TRT showed larger discrepancy rates. In particular, when the heat storage effect is not removed, the discrepancy rate for the short-term ground thermal resistance increased by ~27%.

Experimental Optimization of a Solar Distillation Unit

Today global warming is a big issue. Ambient temperature have drastically increased, leading to severe droughts especially in those areas which receive less than average rainfall. Inadequate supply of quality drinking water especially in the rural areas have led to develop a distillation system with affordable cost and less maintenance in rural areas. Countries like India and South Africa are getting ample amount of solar energy almost throughout the year. Solar based water distillation unit- Solar still can be great solution to those kind of areas. Efficiency of the solar distillation can be improved by increasing evaporation rate which is a function of incident radiation. Further by increasing concentration of total dissolved salts in the water, base plate absorptivity and efficient energy absorbing material, by providing additional heat with solar water pre-heaters efficiency of solar still can be improved. Here experiments were carried out in order to find out optimum water bath depth and salt concentration in water in solar still for maximizing the yield. Experiments are also carried out by adding heat storage material and effect of salt concentration on yield.

Thermal Storage Effect Analysis of Floor Heating Systems Using Latent Heat Storage Sheets

The thermal energy storage (TES) is an energy storage method implemented to reduce the heating energy consumption of buildings by utilizing a high-efficiency heating system and a TES system. Therefore, in this study, a TES system is applied to a high-efficient floor heating system. Various methods are available to utilize the sensible heat and latent heat for TES, and a phase change material (PCM) that can store the latent heat is used in this study. The PCM is used in the form of a heat storage sheet. The physical property analysis results show that the phase change interval of the PCM was 17–32 °C, the latent heat amount was 40.39 J/g, and the specific heat was 1.5 J/(g K). The dynamic heat analysis confirmed the peak temperature rise during heating, and the maximum value at the surface was 1.04 °C. In addition, during cooling, a cooling delay time of up to 5 h was observed due to the heat storage effect of the PCM. Therefore, it is possible to store thermal energy by using a material called PCM, and the saved heat energy can reduce the heating energy requirement of buildings.

Thermal performance of a heating system combining solar air collector with hollow ventilated interior wall in residential buildings on Tibetan Plateau

Solar air heating is very promising in residential buildings on Tibetan Plateau, and effective heat storage is indispensable for continuous heating. Exterior wall is often used for the heat storage, whereas the interior wall is seldom exploited. This paper investigates a heating system combining solar air collector with hollow ventilated interior wall for residential buildings on Tibetan Plateau. A simplified model based on discrete mathematics is established by EnergyPlus and is validated for modeling this system. With this model, a case study is performed to evaluate thermal performances of this system. Moreover, influencing factors of this system are analyzed as well. Results show that compared with the other two typical systems this system increases the minimum indoor air temperature by 6.5 °C and 3.2 °C with night heating need reduced by 79.9% and 60.7%, respectively. For the interior wall material, time constant and thermal inertia are dominant. The optimum window-wall ratio for the south façade is within 0.3–0.4, while the best circulation air flow rate is within 300–500 m³/h. The outdoor air temperature has few influences on the heating performance of this system. Overall, this system is applicable to the heating of residential buildings on Tibet Plateau.

Investigating the effect of pumice stones sensible heat storage on the performance of a solar still

In this communication, a single slope basin type solar still is investigated for the climatic conditions of Aligarh (27.89° N, 78.08° E), India. The solar still was tested for the change in the amount of energy storage material (pumice stones) for a constant amount of water (10 L) in the basin. An experiment was initially conducted without any energy storage material and was later compared with the experimental data of solar still with 5 kg and 10 kg pumice stones. Daytime yield for the solar still without energy storage material was found to be 1950 ml; and decreased for solar stills with 5 kg and 10 kg pumice stones as 1748 and 1618 ml of distillate, respectively. The productivity of the solar still during nighttime enhanced due to energy storing capacity of pumice stones but the overall production reduced by increasing the mass of pumice stones. Further, the three cases were also compared on the basis of heat transfer coefficients from water to glass, and glass to the ambient. The overall thermal efficiency of the solar still with no mass, 5 kg and 10 kg pumice stones was found to be 35.1%, 29.3% and 28.8% respectively.

Influence of NiTi alloy phase change heat-storage particles on thermophysical parameters, phase change heat-storage thermoregulation effect, and pavement performance of asphalt mixture

Phase change material is a high thermal storage substance, which can reduce temperature-related diseases of asphalt pavement when mixed with asphalt mixture. In this paper, NiTi alloy phase change heat-storage asphalt mixture (NiTi APCHAM) are prepared by using equal volume parts to replace fine asphalt aggregates partially with the NiTi alloy phase change energy-storage particles (NiTi APCEP). As the temperature increases, the specific heat capacity of NiTi APCHAM will increase first and then decrease due to the heat-storage effect of NiTi APCEP. The thermal conductivity coefficient of NiTi APCHAM shows a linear increasing trend with the increase in the substitution rate of NiTi APCEP. Adding NiTi APCEP in asphalt mixture can reduce its daily maximum temperature. Increasing admixture of NiTi APCEP in asphalt mixture can help to improve the phase change heat-storage thermoregulation capacity of the mixture. However, at a 6 wt% substitution rate of NiTi APCEP, the latent heat thermoregulation efficiency of NiTi APCEP reaches to maximum. With the increase in the content of NiTi APCEP, the Marshall stability of asphalt mixture gradually increases, and flexural-tensile strain at low temperature decreases gradually. By contrast, the water stability of the asphalt mixture is unaffected by the addition of NiTi APCEP.

Combined Heat and Power Optimal Dispatch Considering Wind Power Uncertainty

Large-scale integration of wind power is a clean alternative to power generation, but the uncertainty of wind power has become a huge dispatch challenge, which is much more serious in the northeast of China. For this reason, heat storage is configured to decouple thermoelectric constraint of CHP unit, releasing its flexibility and improving its peak-shifting ability. A random variable is introduced to represent wind power deviations firstly, then a chance constraint economic dispatch model of an aggregation unit containing wind power and CHP unit is established to explain the standby effect of heat storage on wind power uncertainty. Finally, a case study is conducted to verify the performance of the heat storage. The example results show that when configured with heat storage, the CHP unit have broadened its adjustable electrical output range, so more reserve capacity is released to cope with wind power uncertainty.

Superhydrophobic Coatings from Beeswax‐in‐Water Emulsions with Latent Heat Storage Capability

AbstractBeeswax particles are homogenously emulsified in commercial aqueous polymer dispersion, without additional dispersing agents and surfactants. Emulsions display very good stability with wax droplet size distribution around 350 nm. The wax to polymer ratio in the emulsions can be tuned without compromising emulsion stability. The emulsions are spray coated in order to create either hydrophobic or superhydrophobic coatings. For superhydrophobicity, silica nanoparticles are dispersed in the emulsions at different concentrations. Beeswax‐rich coatings such as the ones with 1:1 beeswax:polymer ratio or more, including the superhydrophobic ones, demonstrate promising latent heat storage characteristics, suitable for thermal management applications. Electron microscopy studies show that as a result of emulsification, the polymer encapsulates the wax droplets/particles as a nanothin shell, preventing a major problem related to low melting point phase change materials referred to as leaching. Hence, the coatings can be heated well above the melting point of beeswax (≈62 °C) and can still demonstrate effective heat storage during the cooling stage. This water‐based coating process using ecofriendly material constituents can easily be scaled up and used in responsive coating applications, ranging from electronics to interior or exterior structural buildings requiring efficient energy management and thermal energy savings.

Distribution and forecast of air temperature in determining of heat output of the district heating substation with heat storage

The aim of this article was to determine the energetic effect of adapting the control method of district heating substation to a solution using dispersed heat storage. The current control method of district heating substation uses the equations for regulating the temperature distribution of the installation water based on the value of the external temperature. This control method causes a significant amount of heat not consumed by end users. To adapt the control method to a solution using dispersed heat storage the following values were analyzed: the forecast of external temperature and duration of episodes with the lowest external temperatures on the heat output of the district heating substation based on 63 heating seasons. Obtained results were presented for a district heating substation in Poland. The analysis shows that a temperature of -15°C can be adopted as the reference to determine the expected heat output of the district heating substation. On this basis the demand for heat output for central heating purposes was 406 kW instead of 430 kW. The energetic effect of use dispersed heat storage to compensate the reduced heat output of the district heating substation was 24 kW with a compensation time of 24.2 h.