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Cool Thermal Energy Storage
Published in Moghtada Mobedi, Kamel Hooman, Wen-Quan Tao, Solid–Liquid Thermal Energy Storage, 2022
Several criteria need to be evaluated before selecting a PCM for a particular application. First, materials with very latent heats of fusion (hsl) are advantageous. The latent heat of fusion is the amount of energy absorbed or released by a material during melting or solidification, respectively. Traditionally, the latent heat of fusion is described on a per-mass basis, and water has the highest latent heat on a per-mass basis of any other common substance used as a PCM at moderate temperatures. Recently, it has become popular to describe PCMs on a per-volume basis for building applications, since space, rather than weight, is more of an issue in HVAC-related applications [16]. By describing PCMs in terms of energy storage density, often described in units kWh/m3, instead of kJ/kg as for the per-mass basis, other PCMs become more attractive when space-based issues are relevant. Water has an energy storage density of ~92 kWh/m3; however, some inorganic PCMs such as salt hydrates have energy storage densities well above 100 kWh/m3. Salt-hydrate PCMs have also been gaining popularity due to new demand for reducing the footprint of TES systems in buildings. Furthermore, although nothing can surpass pure water in terms of cost, salt hydrates are relatively inexpensive.
Structure of Molecules
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
An increase in molecular weight often leads to an increase in melting point. The most important feature of a molecule that influences melting point is, however, more difficult to describe. The more symmetrical a molecule, the higher the melting point. Conversely, the more amorphous a molecule, the lower the melting point. Which has the higher melting point, A or B?
Fields that vary with time
Published in Andrew Norton, Dynamic Fields and Waves, 2019
Now consider something quite different. Suppose you want to melt a small piece of brass or steel, perhaps as part of some jewellery you are making. The melting temperatures of these metals are so high that it is difficult to melt them by direct heating. The standard method of melting uses an induction furnace, similar to that shown in Figure 1.3a. Superficially, this consists of a box with a hinged door, inside which is a ceramic crucible. A wire leads from the box to an electricity supply. The metal is placed in the crucible, the door is closed, the switch is thrown to complete the circuit, and after a while the metal melts. Taking apart the box to see how it works (Figure 1.3b), you would discover a solenoid encircling the crucible. (The solenoid is contained in a water jacket to keep it from overheating.)
A computer-aided unit process sustainable modelling for manufacturing processes: case for extrusion process
Published in Production & Manufacturing Research, 2019
In the process of melting metal in oil fired furnaces, heat energy is provided in form of furnace oil, diesel and other fuels. The quantity of fuel consumption primarily depends on the heat energy required to increase the temperature of material from the ambient temperature to the required injection temperature. The process of melting features a complex phase transformation and change in state of material from solid state to the liquid. During this transformation, heat energy is required to raise the temperature of the casting alloy from ambient to superheated and melting temperatures. Thus, total heat energy can be given by the following relation (Bill, 2005).
TIG torch surfacing of metallic materials – a critical review
Published in Transactions of the IMF, 2019
M. Azwan, M. A. Maleque, M. M. Rahman
The melting process or fusion process is a method that uses high temperatures that produce a melt pool with metallurgical bonding upon solidification. The development of the fusion process on metallic materials has been accelerated with the discovery of electric energy. The evolution of the melting process was rapid from the eighteenth century as can be seen in Figure 1.41,42 The heat fused can be used to modify the near-surface layer of the substrate material in order to enhance its hardness and wear performance. The melting process is commonly utilised to reinforce metallic surfaces with ceramic particles due to the superior hardness and thermal stability of the latter.
Synthesis and characterisation of novel aromatic ester swallow-tailed cholesteric liquid crystal polymers
Published in Liquid Crystals, 2023
Zhong-Xin Ge, Yi-Min Wang, Jiang-Tao Sun, Zi-Yun Zhang, Ying-Gang Jia, Mei Tian, Dan-Shu Yao
In general, there are many factors that can affect the melting point and clearing point of a compound, such as molecular structure, molecular weight, flexibility, intermolecular force, etc. It can be seen from Table 2, by comparing the melting points of M1 and M2, it is found that the melting point of M2 is much smaller than that of M1, which may be attributed to the following reasons: although the molecular weight of M2 is large, its flexibility increases and its rigidity decreases with the increase of the number of C atoms. At the same time, the branching arrangement leads to the increase of molecular spacing, the deterioration of molecular ordering, and the weakening of intermolecular force. On the other hand, the liquid crystal property of the monomer M2 is better than that of M1. This is because although both M1 and M2 belong to swallow-tailed liquid crystal compounds, M2 has one more branch than M1, so M2 molecules are arranged more closely. The arrangement and accumulation of molecules with high density is the driving force to induce the formation of liquid crystal phase, so M2 exhibits better liquid crystal properties. However, the structure of M3 is more similar to the traditional rod-like liquid crystal structure. The length-to-diameter ratio of the liquid crystal elementary is larger, and the melting point and clearing point of the monomer are higher, so the liquid crystal performance is best.