Mathematical model of absorption and hybrid heat pump

Recovering waste heat from industrial processes is bene ficial in order to reduce the primary energy demands and heat pumps can be used to this purpose.Absorption heat pumps are energy-saving and environment-friendly because use working fluids that do not cause ozone depletion and can reduce the global warming emissions.The hybrid heat pump processes combine the conventional vapor-compression and the absorption heat pump cycles.Studies about the simulations and modeling of hybrid heat pumps are few in literature.In this research a mathematical model for single effect absorption and hybrid heat pump is carried out with Chem Cad? 6.0.1.LiBr–H_2O is used as working fluid while electrolytic NRTL and electrolytes latent heat are used as thermodynamic model due to the better results.Binary parameters of activity coef ficients are regressed from experimental vapor pressure data while default constants are used for the solubility expressions.A design of heat pumps is developed and a new modeling of generator is analyzed.The coef ficient of performance of absorption heat pump and hybrid heat pump is equal to 0.7 and 0.83 respectively.For absorption heat pump a sensitivity analysis is carried out to evaluate the effect of temperature and pressure generator,the concentration of Li–Br solution on coef ficient of performance,cooling capacity and working fluid temperature.For hybrid heat pump,the different coef ficients of performance,the primary energy ratio,the generator heat,and the compressor power are analyzed for different values of compressor proportion.Results show that comparing the two systems the hybrid pump allows to save more primary energy,costs and carbon dioxide emissions with respect to absorption heat pump with the increasing of compressor proportion parameter.Future researches should focus on the construction of this heat pumps integrated in chemical processes as a biogas plant or trigeneration systems.

Synthesis and X-Ray Diffraction Analyses of Calcium Hydroxide Nanoparticles in Aqueous Suspension

Calcium hydroxide nanoparticles in aqueous suspensions (also called nanolime) were successfully employed in Cultural Heritage conservation thanks to the ability of favoring readhesion of the pictorial layer on original carbonatic substrates or allowing to a better superficial cohesion and protection of treated stones. In this work, we have synthesized nanolime particles in aqueous suspension by two different methods. The produced particles were characterized in the laboratory, in terms of structural and morphological features, by means of X-Ray diffraction powder (XRD) and by transmission electron microscopy (TEM), respectively. Nanoparticles were crystalline, regularly shaped, hexagonally plated and with side dimensions generally ranging from 300 nm to 30 nm or less. Crystal structure of nanolime particles directly in the aqueous suspension, has been also analyzed by synchrotron diffraction from X-ray synchrotron radiation (SR-XRD);data have been analyzed by means of the Rietveld method and we have investigated the structure of Ca(OH)2 particles in suspension in terms of cell parameters, atomic coordinates, bond lengths and angles.

Synthesis, Textural and Structural Properties of Calcium Hydroxide Nanoparticles in Hydro-Alcoholic Suspension

The use of calcium hydroxide nanoparticles (nanolime) in hydro-alcoholic suspensions represents a good enhancement in particular in the conservation of stones and surfaces of interest in Cultural Heritage. In this work we have produced nanolime by using our alternative method of synthesis (based on the use of a surfactant agent in the original solution) and we have studied, for the first time, structural and morphological properties of the synthesized nanoparticles directly in hydro-alcoholic suspension by synchrotron X-ray diffraction technique and transmission electron micro-scope observations. The particles characterization was performed on suspensions synthesized by varying surfactant content in the synthesis procedure and the water/alcohol ratio, too. We have found that only pure and crystalline Ca(OH)2 particles produced during the synthesis procedure and they maintained stably in suspension. These particles were hexagonally plated and regularly shaped with side dimension ranging from 300 to 40 nm or less;they had a platy habit and they presented, particularly with high alcohol content in suspension, a preferred orientation along z-axis.

A New and Original Method to Produce Ca(OH)<SUB>2</SUB>Nanoparticles by Using an Anion Exchange Resin

Ca(OH)2 nanoparticles in hydro-alcoholic dispersion (nanolime) were successfully employed in Cultural Heritage conservation, thanks to the ability to overcome the limiting aspects of traditional lime treatments. Nanolime were currently produced by chemical precipitation process, at high temperature, with long times of synthesis, and after several purification steps to remove undesired secondary phases. In this paper, an innovative, simple and original method for nanolime production was described. The method was based on an ion exchange process between an anionic resin and a calcium chloride aqueous solution, operating at room temperature. A pure Ca(OH)2 nanoparticles suspension can be rapidly obtained after separating the resin from suspension, and any purification step was necessary. The exhausted resins can be regenerated and reused for a cyclic nanolime production. Structural and morphological features of the produced nanolime were preliminarily characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Moreover, XRD measurements allowed estimating nanoparticles reactivity by following their carbonatation process in air, in relation to different water/alcohol ratios and medium or high relative humidity conditions. The produced Ca(OH)2 nanoparticles appeared hexagonally plated, with dimension less than 100 nm and, compared with those obtained by typical wet precipitation method, they proved to be more reactive.

Passive Intermodulation Measurement:Challenges and Solutions

In modern wireless communication systems,the signal-to-noise ratio(SNR)is one of the most important performance indicators.When the other radio frequency(RF)performance of the components is well designed,passive intermodulation(PIM)interference may become an important factor limiting the system’s SNR.Whether it is a base station,an indoor distributed antenna system,or a satellite system,there are stringent PIM level requirements to minimize interference and enhance network capacity in multicarrier networks.Especially for systems of high power and wide bandwidth such as 5G wireless communication,PIM interference is even more serious.Due to the complexity and uncertainty of PIM,measurement is the most important means to study and evaluate the PIM performance of wireless communication systems.In this review,the current main PIM measurement methods recommended by International Electrotechnical Commission(IEC)and other standard organizations are introduced,and several key challenges in PIM measurement and their solutions(including the design of PIM tester,the location of the PIM sources,the design of compact PIM anechoic chambers,and the evaluation methods of PIM anechoic chambers)are highlighted.These challenges are of great significance to solve PIM problems that may arise during device characterization and verification in real wireless communication systems.

IE3 Efficiency Induction Motors with Aluminum and Copper Rotor Cage： Technical and Economic Comparison

The aim of this study was to design three-phase induction motors with aluminum and copper cage, in the range 0.75 ÷22 kW, to fulfill the 1E3 efficiency level according to typical performance and standard constraints. The proposed study has concerned TEFC （ totally Enclosed Fan-Cooled ）, 400 V, 50 Hz, SI duty three phase squirrel-cage induction motors only. The motors＇ designs, with AI and Cu cage, have been optimized in order to reach the minimum efficiency level IE3 at lowest active material costs and satisfy the physical and performance constraints of the designs, which are the motor specifications. A suitable optimization procedure has been used which allowed to find the ＂best design＂ by chancing the geometric dimensions of the stator, rotor shape, the stator winding and the stack length. In order to guarantee the goodness and feasibility of the optimized designs, several constrains have been imposed.

Data trustworthiness and user reputation as indicators of VGI quality

Volunteered geographic information(VGI)has entered a phase where there are both a substantial amount of crowdsourced information available and a big interest in using it by organizations.But the issue of deciding the quality of VGI without resorting to a comparison with authoritative data remains an open challenge.This article first formulates the problem of quality assessment of VGI data.Then presents a model to measure trustworthiness of information and reputation of contributors by analyzing geometric,qualitative,and semantic aspects of edits over time.An implementation of the model is running on a small data-set for a preliminary empirical validation.The results indicate that the computed trustworthiness provides a valid approximation of VGI quality.

An innovative trigeneration system using biogas as renewable energy

One of the ways to decrease the global primary energy consumption and the corresponding greenhouse gas emissions is the application of the combined cooling, heating and power generation technologies, known as trigeneration system. In this research an innovative trigeneration system, composed by an absorption heat pump, a mechanical compression heat pump, a steam plant, and a heat recovery plant is developed. The low tem- perature heat produced by absorption chiller is sent to a mechanical compression heat pump, that receives pro- cess water at low temperature from the heat recovery plant and bring it to higher temperatures. The trigeneration system is fed by biogas, a renewable energy. A design and a simulation of the system are developed by ChemCad 6.3 software. The plant produces 925 kW of electrical energy, 2523 kW of thermal energy and 473 kW of cooling energy, by the combustion of 3280 kW of biogas. Primary energy rate （P.E.R.） is equal 1.04 and a sensitivity analysis is carried out to evaluate the effect of cooling capacity, produced electrical energy and process water temperature. The first has a negative effect, while other parameters have a positive effect on P.E.R. Compared to a cogeneration system, the tdgeneration plant produces the 28% higher of power and the 40% lower of carbon dioxide emissions. An economic analysis shows that the plant is economically feasible only consid- ering economic incentives obtained by the use of heat pumps and steam plant at high efficiency. Saving 6431 t.a-1 corresponding to 658000 EUR.a-1 of incentives, the plant has a net present value （N.P.V.） and a pay back period （P.B.P.） respectively equal to 371000 EUR and 4 year. Future works should optimize the process considering cost and energetic efficiency as the two objective functions.

Phase-matching-free parametric oscillators based on two-dimensional semiconductors

Optical parametric oscillators are widely used as pulsed and continuous-wave tunable sources for innumerable applications,such as quantum technologies,imaging,and biophysics.A key drawback is material dispersion,which imposes a phase-matching condition that generally entails a complex design and setup,thus hindering tunability and miniaturization.Here we show that the burden of phase-matching is surprisingly absent in parametric microresonators utilizing mono-layer transition-metal dichalcogenides as quadratic nonlinear materials.By the exact solution of nonlinear Maxwell equations and first-principle calculations of the semiconductor nonlinear response,we devise a novel kind of phase-matching-free miniaturized parametric oscillator operating at conventional pump intensities.We find that different two-dimensional semiconductors yield degenerate and non-degenerate emission at various spectral regions due to doubly resonant mode excitation,which can be tuned by varying the incidence angle of the external pump laser.In addition,we show that high-frequency electrical modulation can be achieved by doping via electrical gating,which can be used to efficiently shift the threshold for parametric oscillation.Our results pave the way for the realization of novel ultra-fast tunable micron-sized sources of entangled photons—a key device underpinning any quantum protocol.Highly miniaturized optical parametric oscillators may also be employed in lab-on-chip technologies for biophysics,detection of environmental pollution and security.