Article

The latent heat of fusion of some metals

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

The latent heats of a number of the commoner metals have been measured by determining the total heat of liquid and solid from a series of initial high temperatures. The calorimetry was by the method of mixtures, introducing several refinements, of which the chief were the use of fairly large charges of metal (of the order of 2 kilograms), and a device by which the hot charge was not allowed in contact with the water of the calorimeter until the latter was completely closed; this eliminates error due to production and escape of steam, with a consequent loss of heat. The device referred to consisted in the provision of a sheet metal vessel suspended by threads from the main lid of the calorimeter. The aperture through which the charge was introduced was closed by a rotating lid, in the main lid, and the crucible being introduced, was submerged after the closing of this smaller lid by means of a wire passing through an eyelet in the base of the calorimeter, and out at the top. The results for the latent heat are given below: - Metal. Melting point, °C. Latent Heat. (Calories per gm.) Aluminium 657 92.4 Antimony 630 24.3 Bismuth 269 13.0 Lead 327 6.26 Magnesium 644 46.5 Tin 232 14.6 Zinc 420 26.6 The Paper also contains values for the specific heats up to the melting point, obtained by differentiation of the temperature-total heat curves.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Magnesium is an alkaline earth metal, the thermophysical properties of which have been studied in more detail than those of other elements in group IIA of the periodic table. Experimental research has been carried out in a large number of works [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], and recommended data are given in a number of reference books [19][20][21][22][23][24], reviews [25][26][27][28][29], and databases [30,31]. An analysis of the information available in the literature has generally shown a satisfactory agreement between data on the volumetric, caloric, and transport properties of magnesium in the solid state. ...
... A similar situation can be observed during consideration of data available in the literature on the caloric properties of magnesium. The values of the magnesium fusion enthalpy measured in [13,18] differ from each other by a factor of almost two. The scatter in the data on the enthalpy [13,14,[16][17][18] and heat capacity [14,16,18] of liquid magnesium significantly exceeds the measurement error. ...
... The values of the magnesium fusion enthalpy measured in [13,18] differ from each other by a factor of almost two. The scatter in the data on the enthalpy [13,14,[16][17][18] and heat capacity [14,16,18] of liquid magnesium significantly exceeds the measurement error. Moreover, the existing experimental results even do not suggest any conclusions about the behavior of the temperature dependence of the heat capacity of liquid magnesium. ...
Article
Full-text available
A number of thermophysical properties of pure magnesium are measured with highaccuracy over a wide range of temperatures in the solid and liquid states. The enthalpy andisobaric heat capacity of magnesium are investigated over a temperature range of 431–1176 K with application of a massive high-temperature isothermal drop calorimeter. The estimated errorin the data on enthalpy and heat capacity is 0.2% and 0.5%, respectively. The enthalpy of fusion ofmagnesium is 8455 ± 22 J/mol. The thermal conductivity and thermal diffusivity of solid and liquidmagnesium are measured in the range of 291 K to 1221 K by the laser flash method. The errors in thethermal conductivity measurements are 2–5% for the solid state and 4–6% for the liquid one. It isshown that the thermal conductivity and thermal diffusivity of magnesium decrease about 1.5 timesduring melting. Our results are compared with data in the literature and with calculations based onthe Wiedemann–Franz law. Approximation equations are constructed and tables of recommendedvalues of the investigated properties of magnesium are presented for a temperature range of 291–1221 K for the condensed state.
... Similar measurements were carried out later by Jaeger and Bottema [42], Fig. 4a, and they provide more reliable data, although both set of measurements are in reasonable agreement. Iitaka [43], Awbery and Griffiths [44] and Umino [45] carried out measurements of H o (T)-H o (293). From this set of measurements the data from Awbery and Griffiths [44] and Umino [45] are in a good agreement with each other, while data from Iitaka differ significantly [43], Fig. 4b. ...
... Iitaka [43], Awbery and Griffiths [44] and Umino [45] carried out measurements of H o (T)-H o (293). From this set of measurements the data from Awbery and Griffiths [44] and Umino [45] are in a good agreement with each other, while data from Iitaka differ significantly [43], Fig. 4b. The most recent measurements were carried by Genot [46], however the actual temperature of the calorimeter was specified in the paper as 471 K (198°C), which makes it impossible to compare with experimental measurements from other authors. ...
... Similar peculiarities were taken into account as in the analysis of data as for solid tin enthalpy drop data. A comparison of the data from Iitaka [43], Awbery and Griffiths [44] and Umino [45] showed that these results are in reasonable agreement (Fig. 6). The only high temperature measurements were carried out by Feber et al. [51] These results seem to be in agreement with lower temperature data. ...
Article
Thermodynamic data for crystalline white and grey tin were assessed using an extended Einstein model from 0 K. Ab-initio simulations in the framework of density functional theory (DFT) with the quasiharmonic approximation (QHA) were carried out to define the heat capacities for both phases of tin from 0 K up to room temperatures. Good agreement was observed between theoretical and experimental heat capacities, which makes it possible to combine theoretical and experimental data to determine the standard entropies. Data for the liquid phase were described using a two state model. During the assessment, careful analysis of the experimental data was carried out. In order to fulfil the need for a precise evaluation of So298 we needed to use an additional technique using multiple Einstein functions, which allows the experimental heat capacity and enthalpy data for the solid phase to be approximated accurately from 0 K up to the melting point and to estimate solid phase transition entropy and enthalpy which are difficult to measure due to a high activation barrier. Additional measurements of heat capacity were carried out where existing data were scarce.
... As discussed in Supplementary Note B, the main difference between both assessments is that that a lower Einstein temperature was attributed to the amorphous phase in the present work, and that the high temperature heat content data from Feber et al. [79] were reproduced more closely, as highlighted in Fig. 7(b). [26,44,79,[160][161][162][163][164][165][166][167][168] and the recent assessment from Khvan et al. [26] 4.3.2 Volume and related properties ...
... Turnbull [160] that were selected by Khvan et al. [26]. All the available heat content data [26,79,[165][166][167][168] were also considered in the optimization, except for the earlier measurements from Wüst et al. [164] which were found to be inconsistent with other studies. ...
Article
Full-text available
An assessment of the Sn unary system is presented. First, the literature on phase equilibria, the thermodynamic properties, the volume and related properties, and shock compression of tin is thoroughly reviewed. Second, the Sn system is investigated by means of synchrotron X-ray diffraction in a diamond-anvil cell up to pressures and temperatures of 57 GPa and 730 K. New information is obtained on the thermal stability and thermal expansion coefficient of the γ (I4/mmm) and γ’’ (Im3¯m) phases. Third, density functional theory calculations are conducted on the six allotropic phases of tin observed in experiments using both a local density approximation (LDA) and a generalized gradient approximation (GGA) functional. This combined experimental and theoretical investigation provides further insights on the pronounced metastable nature of Sn in the 30 - 70 GPa range. Last, a Gibbs energy modeling is conducted using the recently proposed Joubert-Lu-Grover model which is compatible with the CALPHAD method. Special emphasis is placed on discussing extrapolations to high pressures and temperatures of the volume and of the thermodynamic properties. While the description of the heat capacity is approximate at moderate pressure, all available data are closely reproduced up to 2500 K, which is 5 times higher than the atmospheric pressure melting point of tin, and 150 GPa, which is almost 3 times the standard bulk modulus of β-Sn.
... As discussed in Supplementary Note B, the main difference between both assessments is that that a lower Einstein temperature was attributed to the amorphous phase in the present work, and that the high temperature heat content data from Feber et al. [79] were reproduced more closely, as highlighted in Fig. 7(b). [26,44,79,[159][160][161][162][163][164][165][166][167] and a recent assessment [26] 4.3.2 Volume and related properties ...
... Turnbull [159] that were selected by Khvan et al. [26]. All the available heat content data [26,79,[164][165][166][167] were also considered in the optimization, except for the earlier measurements from Wüst et al. [163] which were found to be inconsistent with other studies. ...
Preprint
Full-text available
An assessment of the Sn unary system is presented. First, the literature on phase equilibria, the thermodynamic properties, the volume and related properties, and shock compression of tin is thoroughly reviewed. Second, the Sn system is investigated by means of synchrotron x-ray diffraction in a diamond-anvil cell up to pressures and temperatures of 57 GPa and 730 K. New information is obtained on the thermal stability and thermal expansion coefficient of the gamma (I4/mmm) and gamma" (Im-3m) phases. Third, density functional theory calculations are conducted on the six allotropic phases of tin observed in experiments using both a local density approximation (LDA) and a generalized gradient approximation (GGA) functional. This combined experimental and theoretical investigation provides further insights on the pronounced metastable nature of Sn in the 30 - 70 GPa range. Last, a Gibbs energy modeling is conducted using the recently proposed Joubert-Lu-Grover model which is compatible with the CALPHAD method. Special emphasis is placed on discussing extrapolations to high pressures and temperatures of the volume and of the thermodynamic properties. While the description of the heat capacity is approximate, all available data are closely reproduced up to 2500 K, which is 5 times higher than the atmospheric pressure melting point of tin, and 150 GPa, which is almost 3 times the standard bulk modulus of beta-Sn. Therefore, this approach appears promising to model multi-component phase diagrams at high pressure.
... Awbery and Griffiths [53] dropped samples of 99.9% purity (he reported that before the experiment the impurity was 0.002% Fe and Cu) into an ice calorimeter. After the experiment the author determined the impurity levels to be 0.012% Fe and 0.004% O. Awbery and Griffiths [53] stated that the uncertainty was about 1%; we consider it to be approximately 15% by comparison with the results of other experiments. ...
... Awbery and Griffiths [53] dropped samples of 99.9% purity (he reported that before the experiment the impurity was 0.002% Fe and Cu) into an ice calorimeter. After the experiment the author determined the impurity levels to be 0.012% Fe and 0.004% O. Awbery and Griffiths [53] stated that the uncertainty was about 1%; we consider it to be approximately 15% by comparison with the results of other experiments. ...
Article
Thermodynamic data for the crystalline and liquid phases of pure lead were critically assessed. A thermodynamic description was obtained using an extended Einstein model for the crystalline phase and a two state model for the liquid phase. The assessment was carried out through careful analysis of the experimental data published in the scientific literature. Additional measurements using enthalpy drop were also carried out in the present work to remove ambiguities in published experimental data.
... Conceptually speaking, the external heating of the electrons would have to provide sufficient heat energy to heat both ionic and electronic systems to 933K and provide the heat of fusion. With the experimentally determined values γ = 1.35 · 10 −3 J/(mol K) [109] and E fusion = 10431.1 J/mol [110], one can determine E melt e as E melt e = 22654.8 J/mol. ...
Preprint
Full-text available
We introduce machine learning (ML) models that predict the electronic structure of materials across a wide temperature range. Our models employ neural networks and are trained on density functional theory (DFT) data. Unlike other ML models that use DFT data, our models directly predict the local density of states (LDOS) of the electronic structure. This provides several advantages, including access to multiple observables such as the electronic density and electronic total free energy. Moreover, our models account for both the electronic and ionic temperatures independently, making them ideal for applications like laser-heating of matter. We validate the efficacy of our LDOS-based models on a metallic test system. They accurately capture energetic effects induced by variations in ionic and electronic temperatures over a broad temperature range, even when trained on a subset of these temperatures. These findings open up exciting opportunities for investigating the electronic structure of materials under both ambient and extreme conditions.
... Where: is the latent heat of fusion of the aluminum (396 kJ/kg) [10]. ...
Article
Full-text available
Aluminum is one of the most versatile engineering metals, finding its use in a variety of fields including construction, architecture, aerospace, automotive, consumer products, and many more. The high demand for aluminum production is driven by its advantageous physical, chemical, and mechanical properties, such as a high strength to weight ratio and good corrosion resistance. Additionally, aluminum can be recycled using processes that require only a fraction of the energy required for primary production. Aluminum recycling is primarily accomplished by melting in foundries. In some aluminum foundries, a large amount of energy is lost due to poor insulation and an inaccurate knowledge of the crucible temperature. This project focused on designing a safe, efficient electric aluminum foundry. Using theoretical calculations, an electric foundry was designed to melt 3.0 kg of aluminum cans using ~9 MJ of energy. A prototype was successfully fabricated and tested with attention to the structural, thermal, and electrical design aspects. Experiments showed that the foundry was capable of melting 3.0 kg of aluminum cans using ~11 MJ of energy, which was close to the theoretical calculations. The normalized energy usage of the foundry was ~6.9 MJ per kg of pure aluminum produced, which compares well with benchmarked aluminum recycling foundries.
... Wherein is the latent heat of fusion of the aluminum (396 kJ/kg). [10] iii. Heat lost due to conduction ...
Preprint
Full-text available
Aluminum is one of the most versatile engineering metals, finding its use in a variety of fields including construction, architecture, aerospace, automotive, consumer products, and many more. The high demand for aluminum production is driven by its advantageous physical, chemical, and mechanical properties, such as a high strength to weight ratio and good corrosion resistance. Additionally, aluminum can be recycled using processes that require only a fraction of the energy required for primary production. Aluminum recycling is primarily accomplished by melting in foundries. In some aluminum foundries, a large amount of energy is lost due to poor insulation and an inaccurate knowledge of the crucible temperature. This project focused on designing a safe, efficient electric aluminum foundry. Using theoretical calculations, an electric foundry was designed to melt 3.0 kg of aluminum cans using ~9 MJ of energy. A prototype was successfully fabricated and tested with attention to the structural, thermal, and electrical design aspects. Experiments showed that the foundry was capable of melting 3.0 kg of aluminum cans using ~11 MJ of energy, which was close to the theoretical calculations. The normalized energy usage of the foundry was ~6.9 MJ per kg of pure aluminum produced, which compares well with benchmarked aluminum recycling foundries.
... In the present study, the thermal conductivity value had been assumed to be equal to 5.7 times of that corresponding to ambient temperature, as reported by Zhang et al. [32]. Latent heat of fusion, solidus, and liquidus temperature values were kept equal to 389 kJ/kg, 880 K, and 911 K, respectively [33,34]. Convective heat transfer coefficient in the air and emissivity were considered to be equal to 11 W/m 2 K and 0.03, respectively [35]. ...
Article
A proper combination of thermal and mechanical loads is generally maintained to provide the necessary complicated shape and profile to the sheet metal in shipbuilding, aerospace, and others, for which an experienced operator should have the knowledge of the equivalence of these two loads. A study was conducted to establish the equivalence of thermal and mechanical loads in terms of their capability to produce the same deflection. The maximum deflection of a simply supported beam-like structure with small thickness subjected to only thermal load had been determined using finite element analysis. Moreover, the temperature profile followed during the heating and cooling was plotted. A test rig was fabricated for determination of the same and necessary comparison to establish this equivalence.
... Leadbetter [24] investigated anharmonic and electronic effects in Al utilizing the theoretical heat capacity at constant volume. Awbery and Griffiths [25] and Speros and Woodhouse [26] measured the heat of fusion and melting temperature of pure Al by drop calorimetry and differential scanning calorimetry, respectively. ...
Article
In developing the next generation of Calphad databases, new models are used in which each term contributing to the Gibbs energy has a physical meaning. To continue the development, finite temperature density-functional-theory (DFT) results are used in the present work to discuss and suggest the most applicable and physically based model for Calphad assessments of solid phases above the melting point (the breakpoint for modeling the solid phase in previous assessments). These results are applied to investigate the properties of a solid in the superheated temperature region and to replace the melting temperature as the breakpoint with a more physically based temperature, i.e., where the superheated solid collapses into the liquid. The advantages and limitations of such an approach are presented in terms of a new assessment for unary aluminum.
... The peak temperature is a crucial parameter for the formation of Al- alloyed contacts, as it significantly affects both the electrical and the structural contact properties [5,7,8,15,25]. Thereby, the effective peak temperature T peak,eff of the alloying process can significantly differ from the set peak temperature of the furnace due to the high latent heat of the Al paste [26,27]. In the fol- lowing, our model is used to determine T peak,eff . ...
Article
In this study, we present detailed theoretical and experimental investigations on full-area alloying from screen-printed aluminum pastes on silicon surfaces for solar cell applications. We introduce a simple analytical model for the description of the alloying process derived from existing models for evaporated Al layers, which we adapt to printed Al pastes. Thereby, we particularly account for the recrystallization of Si within the paste particles, which we refer to as parasitic Si recrystallization. Applying our model, we demonstrate good accordance of calculated with measured eutectic layer thicknesses. We show that the model can be versatilely used to investigate screen-printed Al-alloyed contacts in detail: We demonstrate that the latent heat of the Al paste significantly influences the alloying process. Thus, the effective peak temperature of the alloying process can be several 100. °C below the set peak temperature of the firing furnace. By combining calculations of the effective peak temperature with measurements of the Al doping concentration, we determine a parameterization of the solid solubility of Al in Si down to the eutectic temperature of 577. °C. Our investigations therefore provide improved understanding of alloying from printed Al pastes and enable the specific optimization of Al-alloyed contacts.
... This was accomplished using the calorimeter built in this investigation. A capsule charged with a known mass of PCM would undergo measurements in the drop Table 3 Thermal properties of zinc (Awbery and Griffiths, 1925;Grønvold and Stølen, 2003;Incropera and DeWitt, 2002). ...
... The melting temperature of the eutectic mixture is measured by current authors using a differential scanning calorimeter (DSC), as displayed in Fig. 1. Additionally, metallic zinc, with a melting point of 420 C [23] and latent heat of 113 kJ/kg [26], could also be a good PCM to store thermal energy for electricity generation. As described earlier, for practical reasons, phase change materials must be encapsulated. ...
Article
The relevance of research into the thermophysical properties of lead is associated with the implementation of a BREST-300 reactor project. The enthalpy of solid and liquid lead in the range of 432–1327 K was measured by the mixing method using a massive isothermal calorimeter. The enthalpy of melting was determined. Approximation equations for the temperature dependence of enthalpy in the range of 298.15–1325 K were obtained to determine the isobaric heat capacity. The existence of a heat capacity minimum for liquid lead in the region of 830 K was established. An analysis of existing recommended and experimental data on the caloric properties of lead was performed. The need for new measurements of the enthalpy and heat capacity of a melt at temperatures above 1050 K is substantiated.
Article
Solar energy offers over 2,945,926 TWh/year of global Concentrating Solar Power (CSP) potential, that can be used to substitute fossil fuels in power generation and mitigate 2.1 GtCO 2 of greenhouse gas (GHG) emission to support Sustainable Development Goals (SDGs) set by the United Nations (UN). Thermal energy storage (TES) is required in CSP plants to improve dispatchability, reliability, efficiency, and economy. Of all TES options, the latent heat thermal energy storage (LHTES) together with phase change materials (PCMs) exhibit the highest potential in terms of efficiency and economy. PCM properties thus become the ultimate decider of CSP performance. This paper reviews over 200 of published articles and websites to describe the history, identify the technologies, economics, and current trends of PCM as LHTES material for CSP plants. A list of 163 PCM candidates suitable for LHTES systems in low-temperature (T < 220 • C), medium-temperature (220 • C < T < 420 • C), and high-temperature (T > 420 • C) applications is presented for the first time. Research gaps are identified to determine the future directions.
Article
We introduce machine learning (ML) models that predict the electronic structure of materials across a wide temperature range. Our models employ neural networks and are trained on density functional theory (DFT) data. Unlike most other ML models that use DFT data, our models directly predict the local density of states (LDOS) of the electronic structure. This provides several advantages, including access to multiple observables such as the electronic density and electronic total free energy. Moreover, our models account for both the electronic and ionic temperatures independently, making them ideal for applications like laser heating of matter. We validate the efficacy of our LDOS-based models on a metallic test system. They accurately capture energetic effects induced by variations in ionic and electronic temperatures over a broad temperature range, even when trained on a subset of these temperatures. These findings open up exciting opportunities for investigating the electronic structure of materials under both ambient and extreme conditions.
Article
In this work the effect of cooling rate on the dual-phase (L12/B2) AlCoCrFeNi2.1 Eutectic High-Entropy Alloy was investigated. AlCoCrFeNi2.1 powders were made using a drop-tube facility, achieving powders of sizes ranging from 850 µm ≤ d < 1000 µm to 38 µm ≤ d < 53 µm with corresponding estimated cooling rates of 114 Ks⁻¹ to 1.75×106 Ks⁻¹ respectively. Average interlamellar spacing decreases from 2.10 µm in the as-cast alloy to 348 nm in the powders of the 38 µm < d < 53 µm size fraction. Although decreased interlamellar spacing is expected to enhance microhardness, such a relation was not as strong as expected, with microhardness of the powders found to vary only slightly from an average value of 340 Hv0.03. This unexpected result is explained via the observation of increased FCC volume fraction. With increasing cooling rate, the microstructure of AlCoCrFeNi2.1 was found to evolve gradually from regular eutectic to colony eutectic, followed by dendritic with eutectic the interdendritic regions. In particles of size d < 212 µm BCC dendrites were observed, either dominating the structure or coexisting with FCC dendrites.
Article
The concentrated solar energy which is one of the renewable energy sources, is examined in metal melting which requires high temperatures. The study is carried out for the first time in an environment where total solar radiation of 1394 kWh m⁻²-year and sunshine duration of 2132 h-year at the sea level in Trabzon province at 41° latitudes and 39° longitudes. In the present work, a single concentrator model of solar furnace system is presented. Parabolic dish with a diameter of 1.42 m was used for the first time with high reflection rate chromium nickel foil in the concentration of the solar rays. To store the concentrated solar beams, a metal melting furnace is designed, manufactured and tested. Total heat loss analysis of the furnace according to measured experimental values is performed for the designed solar furnace. The melting process of the aluminum metal was realized in the furnace. In the experiment, the efficiency of the system was calculated based on the measured temperatures and solar radiations. The system efficiency which consists of the parabolic solar concentrator and the solar furnace was found to be approximately 46% at the average focal temperature of 1023 K. In the melting process, the efficiency of the furnace is calculated as the ratio of stored energy to the absorbed solar energy on the surface. The total thermal efficiency 22% is calculated for the first time in the aluminum melting process and mass flow rate is 0,0667 g s⁻¹ at this time.
Thesis
Full-text available
A numerical heat transfer analysis of encapsulated phase change material (EPCM) capsules was conducted by employing the enthalpy-porosity and VOF methods simultaneously to capture the complex multi-phase heat transfer that occurs within the capsules. The results of the numerical methods employed were validated by comparing the final shape of the solid phase change material (PCM) predicted to that seen within sectioned experimental capsules. The validated methods were used to study the effect that an internal void space has on the heat transfer within an EPCM capsule. Its effect is immediately noticeable as the isotherms no longer form the concentric rings predicted by the unsteady diffusion equation since the void acts as an insulator reducing the conduction rate in the upper portion of the capsule. Additionally, the increased melting rate resulting from convection in the molten PCM further reshapes the solid-liquid interface. In contrast, the solidification process is conduction-dominated and limited by the thermal conductivity of the chosen PCM resulting in considerably longer solidification times. The impact of an internal void on the overall heat transfer was further examined by considering three limiting cases of an upper void, central void, and random void distributions where the upper void is positioned opposite to the orientation of the gravitational vector. Since the PCM for the central void distribution is in direct contact with the entire capsule shell, it has the highest heat transfer rate during the initial melting stages leading to it having a melting time that is 22% and 39% faster than the random and upper void distributions. In an ideal world, one would like to keep the void located as close to the center of the capsule as possible. The vastly different evolution of the solid-liquid interface for the three cases considered highlights the profound impact an internal void has on the temporal and spatial evolution of the solid-liquid interface. The results for a single EPCM capsule were extended by evaluating the performance of a pilot-scale EPCM-based latent heat thermal energy storage (TES) system. The capsules sequentially showed the same evolution of the melting front within the capsules over the course of the charging process. The numerical results were compared to experimental recorded values for the temperature in the furthest downstream EPCM capsule. Agreement within 3% was seen during the initial solid sensible heating stages, however as the capsules began to melt the discrepancy increased due to a poor estimate for the values of the latent heat of fusion of NaNO3. This resulted in a 8% faster predicted melting time. However, this has minimal effect on the overall energy storage of the system due to the large operational temperature range applied in the current experiment. 65% of the 22 MJ of energy release by the heat transfer fluid (HTF) was stored in the 17.7 kg of NaNO3; 20% of this energy can be attributed to latent heat energy storage. Therefore, the system is able to store a large fraction of energy supplied by the HTF with a significant contribution from latent heat. Furthermore, if the operational temperature range were smaller the fraction of latent heat energy storage would have been significantly larger. The second law analysis of an example TES system was conducted to determine the benefit of s system employing a multiple PCMs. As expected, the latent heat-based systems were able to store more energy and exergy with comparable efficiencies than systems that rely on sensible heat only. Furthermore, when the overall cycle performance is examined, systems with multiple PCMs perform better than corresponding single PCM-based systems. While for the operating conditions and PCMs chosen the 2-PCM system was superior, great care is required during the design of an EPCM-based TES system as the difference between the melting point of the PCMs and the inlet temperatures during charging and discharging greatly affect the performance of the system. Lastly, experimental evaluations of the use of metallic oxides as new novel PCMs were conducted. In particular, the eutectic compounds in the Na2O-B2O3 system were investigated as they offer higher energy storage densities at melting temperatures comparable to the previously investigated nitrate and chloride salts. However, the material that was formed during the preparation of the samples was not a eutectic compound due to sodium evaporation and therefore did not melt congruently. Once the initial composition of the material was determined, the discrepancy between the theoretical and experimental energy storage were shown to be within the ±2% uncertainty of the calorimetry system. While these initial results are promising, further research is required before these metallic oxides can be integrated into EPCM-based latent heat TES systems as a superior alternative to the currently employed nitrate and chloride salts.
Article
When designing transient suppression circuits housed on interface assemblies to protect internal circuits from power surges, there exists a need to accurately determine the minimum printed circuit board (PCB) trace width required to tolerate given transients without fusing due to overheating. This paper presents four different PCB trace models that may be used for this purpose. The predicted trace widths are compared with each other for validation by comparison. In addition, selected results are tested to further validate the accuracy of the models.
Article
The objective of this research was to develop encapsulated phase change materials (EPCMs) that can store thermal energy at temperatures up to 450 °C, suitable for applications in concentrating solar power systems. From initial explorations of candidate media, the two salts (PCMs) NaNO3 and eutectic NaCl–MgCl2 were selected for further development as storage media with phase change. A specialized calorimeter with requisite size and temperature capability was designed and built to obtain enthalpy values of the PCMs at temperatures below and above their melting points. The latent heats of phase change can contribute 57% and 75% to storage capacity of the NaNO3 and NaCl–MgCl2 media, respectively, for a 100 °C temperature swing bracketing the salts’ melting points. After calibration, this calorimeter was then used to determine the actual energy storage capacity achieved by capsules of EPCMs of various dimensions. The calorimeter tests proved that the salts and the encapsulation methods chosen here can store thermal energy effectively while taking advantage of the latent heat of phase change. Repeated thermal-cycles showed sustained performance of the EPCMs, with no discernible diminishment in storage capacity.
Article
The heat capacity of zinc has been determined by adiabatic calorimetry from 298.15 to 940K. For crystalline zinc Cp,m increases from 25.47JK−1mol−1 at the former temperature to an evenly extrapolated value of 30.96JK−1mol−1 at the triple-point temperature 692.681K (ITS-90). The estimated heat capacity increment of fusion is 2.46JK−1mol−1. For liquid zinc the heat capacity decreases from 33.42JK−1mol−1 at Tfus to 32.31JK−1mol−1 at 940K. Thermodynamic function values have been derived and are tabulated for selected temperatures after revaluation of earlier low temperature results.
Article
1. Die freie Bildungsenergie des Aluminiumoxyds wurde von Zimmertemperatur bis 2600° K mit Hilfe des 3. Wärmesatzes nach einer vollständigen Sichtung der thermischen Daten berechnet. Bei 298,1° K wurde die freie Energie zu 371,1 kcal gefunden.
Article
Es wurde der Zusammenhang der Zeitdauer des Haltepunktes auf der Abkühlungskurve mit der Schmelzwärme von Metallen und ihren Verbindungen ermittelt. Mit Hilfe dieser Feststellung konnten dann die Schmelzwärmen der Metallverbindungen, sowie von Mg und A1, bestimmt werden. Zur Kontrolle wurden dieselben nochmals nach dem kalorimetrischen Verfahren bestimmt.
  • Atti
  • Torino
Atti. Torino., 17, 111, 1882. Mem. Inst. Lomb., 16, 1, 1891.
  • R S Proc
Proc. R.S., 72, 177, 1903. 2s. Anorg. Chem., 87, 81, 1914.
  • Ann
  • Phys
Ann. Phys., 31, 606, 1910. 2s. Phys. Chem., 71, 257, 1910. Wiss. Abh. P.T. Reichs, 3, 269, 1900. (a) Phil. Trans., 213, 119, 1913. (b) Proc. R.S., 90, 557, 1914. ( U ) Sitz. Akad. Berlin, 261, 1910. (b) Ann. Phys., 36, 395, 1911.
  • Robertson
Robertson. Proc. Chem. Soc., 18, 131, 1903.
  • Ewald
Ewald. Ann. Phys., 44, 1213, 1914.
  • R S Proc
Proc. R.S., 72, 177, 1903. 2s. Anorg. Chem., 87, 81, 1914. Ann. Phys., 31, 606, 1910. 2s. Phys. Chem., 71, 257, 1910. Wiss. Abh. P.T. Reichs, 3, 269, 1900.
  • Griffiths
  • Nernst
  • Schimff