PCM

Melting of the ice/water as the phase change material in a horizontal single-tube annulus is sluggish when the stable stratification exists at the bottom of the configuration. To obviate this problem, three heat transfer enhancement techniques could be implemented using the enthalpy-based lattice Boltzmann method with the double distribution function method to accelerate the process. The multifarious arrangements of the tubes in this horizontal annulus are investigated to expand the region affected by the natural convection. Also, the dispersion of the Cu nanoparticles in the base PCM could boost the thermal conductivity and melting rate. Finally, the metallic porous matrix made of nickel–steel alloys and saturated with the base PCM could be used to enhance the thermal conductivity of the base

Gypsum, due to its unique property and pleasing appearance has made it the material of choice in the construction industry. Gypsum products hold a predominant position in the construction space due to their excellent insulation property both thermal and acoustic and effective fire protection. When used precisely with the innovative materials gypsum can develop the ability against moisture penetration and stability towards impact. Several research works have been done on the mechanical property and durability of gypsum under various circumstances. This paper gives an outline of the process of hydration, dehydration and setting of gypsum of the various admixtures on gypsum. This paper is also concerned with the effect of different types of fibres on gypsum products. Moreover, this paper tries to glean out the previous experimental and analytical studies on gypsum that will serve as a tool for future research works. Efforts have been made to summarize all the information available on the topics related to gypsum and suggestions for future work are also presented.

— CVSD (continuous variable slope delta) modulation is popular effective scheme for companded delta modulation for audio signal. CVSD is best coding technique for improving receiver sensitivity. Here in this paper, we discuss brief introduction about continues variable slope delta modulation codec system and its comparison.

... Ahmet Koca a , Hakan F. Oztop b , Tansel Koyun c and Yasin Varol a , Corresponding Author Contact Information , E-mail The Corresponding Author. ... from 1.22 to 2.63 kW, whereas the rate of heat stored in the LHS unit were 111.2 and 79.9 W. Sari and Kaygusuz [11] conducted ...

The use of Phase Change Material (PCM) improves the thermal storage capacity of Solar Thermal Accumulators
because of its high energy storage density as latent heat, during SolideLiquid phase changes
at constant temperature. The present work is interested in the PCM (Paraffin C18) solidification in thermal
storage coaxial tubes with internal and external horizontal fins for conditioning systems with two air
passages. With this intention, the first stage includes the presentation of a numerical model based on the
continuity, momentum and thermal energy equations handled by the finite volume method. This numerical
approach aims to study the impact of natural convection, occurring in the liquid phase, on the
solidification time of PCM and the temporal evolution of the solidification front. This paper also investigates
the effect of fins number on heat transfer enhancement.

Desalination is a process in which saline water is separated in two parts using different forms of energy. Here we are going to discuss desalination of saline water using solar energy. The solar distiller purifies water by first evaporating and then condensing it. Distilled water contains no salts, minerals or any organic impurities. This distilled water can be used for drinking purposes, applications in hospitals, replenishing batteries, and so on. Our try here is to enhance the solar still productivity using PCM and by varying the angle of the solar still from ground surface. Phase change materials are the thermal energy storage materials. They store energy in the process of changing their aggregate state from solid to liquid. PCM starts melting whenever temperature goes beyond its melting point. The experimental results illustrated that the use of PCM and angle variation with solar still is cost effective and viable in enhancing the evaporation rate as well as thermal conductivity hence freshwater production. Based on the performance evaluation, the daily productivity of freshwater was increased compared to conventional solar still.

Results of an extensive experimental investigation performed to study the effect of different values of wall heat flux in a rectangular PCM (phase change material) test cell on the melting process are presented. A new experimental system consisting of a rectangular cross-section test cell formed from poly-carbonate sheet, copper plates and mica heaters was constructed. During experiments uniform wall heat flux (q 00 wall = 675, 960 and 1295 W/m 2) were applied to both the left and right sides of the test cell. Thermocouples were used to measure the temperature at different locations inside the PCM and on the surface of the copper plates and an infrared camera was used to measure the polycarbonate sheet external surface temperature distribution. The results show the expected strong correlation between the magnitude of wall heat flux and the melt fraction in the PCM as it drives the convective heat transfer. The transparent polycarbonate wall makes it possible to observe the location of the solid/liquid interface and determine melt fractions. The experiments have produced a significant experimental data set for the validation of numerical models simulating the solid/liquid phase change process and PCM melting in geometrical configurations relevant to, for example, latent heat thermal energy storage systems.

Cool roofs are effective solutions to counter the overheating of building roofs, inhabited spaces below and urban areas in which buildings are located thanks to their capability of reflecting solar radiation. Nonetheless, the relatively low surface temperatures that they induce can cause condensation of humidity and leave the surface wetted for large part of the day, thus promoting the growth of bacteria, algae and other biological fouling; this can cause a quick decay of the solar reflective performance. Biological growth is countered by surface treatments, which, however, may be toxic and forbidden in many countries and may also vanish quickly. It can also be countered by lowering the thermal emittance and thus decreasing heat transfer by infrared radiation to the sky and the consequent night undercooling, but this can decrease the performance of cool roofs. An alternative approach, which is analyzed in this work, is to embed in the first layer below the cool roof surface a phase change material (PCM) that absorbs heat during the daytime and then releases it in the nighttime. This can increase the minimum surface temperatures, thus reducing the occurrence humidity condensation and also the biological growth. In this work, preliminary results on the coupling of a cool roof surface with a PCM sublayer are presented, being obtained by theoretical investigation on commercial materials and taking into account the time evolution pattern of the environmental conditions.

In this paper the electrical distribution transformer has been studied numerically and the effect of outside temperature on its cooling performance has been investigated. The temperature range studied covers the hot climate regions. 250 KVA distribution transformer is chosen as a study model. A novel cooling fluid is proposed to improve the cooling performance of this transformer, transformer oil-based microencapsu-lated phase change materials suspension is used with volume concentration (5–25)% as a cooling fluid instead of pure transformer oil. Paraffin wax is used as a phase change material to make the suspension, in addition to the ability of heat absorption due to melting, the paraffin wax considered as a good electrical insulator. Results obtained show that, using of MEPCM suspension instead of pure transformer oil lead to improve the cooling performance of transformer by reducing its temperature and as a consequence increasing its protection against the breakdown. The melting fraction increased with increasing outside temperature up to certain temperature after which the melting fraction reach maximum constant value (MF = 1) which indicate that, the choosing of PCM depend on the environment in which the transformer is used.

El Centro de Estudios del Movimiento Obrero y Socialista presenta en este libro, reunidos por primera vez, los documentos más importantes de cada uno de los congresos nacionales que realizó el Partido Comunista Mexicano a partir de 1919, año de su fundación, hasta su disolución acordada en 1981. Esta recopilación de cincuenta y cinco documentos, que dista de ser la totalidad del material existente, ha procurado ser una cuidadosa selección de aquellos que permiten el conocimiento de aspectos significativos de la historia de una organización partidista que fue parte indisociable de la historia política de México durante el siglo xx, y cuya memoria es indispensable para entender el país de nuestros días y vislumbrar los posibles horizontes de la lucha por la emancipación.

Prospective 6-center study. OBJECTIVE.: To evaluate outcomes of cervical disc replacement performed adjacent to a prior cervical fusion. The use of disc replacement adjacent to a prior anterior cervical decompression and fusion (ACDF) is an attractive reconstructive option, obviating the need for a multilevel fusion. This study reports outcomes from patients with and without previous ACDF receiving the porous coated motion (PCM) artificial cervical disc in a United States Federal Drug Administration Investigational Device Exemption trials. Patients between ages of 18 and 65 with single-level cervical radiculopathy and/or myelopathy, unresponsive to at least 6 weeks of nonsurgical therapy, or experiencing progressive neurologic symptoms were enrolled. Clinical outcomes are compared for patients receiving a PCM disc at a level adjacent to a prior ACDF ("adjacent") and those without having previously had fusion ("primary"). 126 PCM patients were primary (mean age: 4...