EXPERIMENTS DURING FLOW BOILING OF A R22 DROP-IN: R422D ADIABATIC PRESSURE GRADIENTS

R22, the HCFC most widely used in refrigeration and air-conditioning systems in the last years, is phasing-out. R422D, a zero ozone-depleting mixture of R125, R134a and R600a (65.1%/31.5%/3.4% by weight, respectively), has been recently proposed as a drop-in substitute. For energy consumption calculations and temperature control, it is of primary importance to estimate operating conditions after substitution. To determine pressure drop in the evaporator and piping line to the compressor, in this paper the experimental adiabatic pressure gradients during flow boiling of R422D are reported for a circular smooth horizontal tube (3.00 mm inner radius) in a range of operating conditions of interest for dry-expansion evaporators. The data are used to establish the best predictive method for calculations and its accuracy: the Moreno-Quibèn and Thome method provided the best predictions for the whole database and also for the segregated data in the annular flow regime. Finally, the experimental data have been compared with the adiabatic pressure gradients of both R22 and its much used alternative R407C available in the literature

Carbon Dioxide Heat Transfer Coefficients And Pressure Drops During Flow Boiling: Assessment Of Predictive Methods

Among the alternatives to the HCFCs and HFCs, carbon dioxide emerged as one of the most promising environmentally friendly refrigerants. In past years many works were carried out about CO2 flow boiling and very different two-phase flow characteristics from conventional fluids were found. In order to assess the best predictive methods for the evaluation of CO2 heat transfer coefficients and pressure gradients in macro-channels, in the current article a literature survey of works and a collection of the results of statistical comparisons available in literature are furnished. In addition the experimental data from University of Naples are used to run a deeper analysis. Both a statistical and a direct comparison against some of the most quoted predictive methods are carried out. Methods implemented both for low–medium pressure refrigerants and specifically developed for R744 are used in the comparison. Some general indications about the choice of the predictive methods dependently on the operating conditions are given

Seismic vulnerability assessment on a territorial scale based on a Bayesian approach

Italian historical centres are mostly characterized by aggregate buildings. As defined by the Italian codes (Norme Tecniche per le Costruzioni 2008 and Circolare n. 617), the analysis of the most representative local mechanisms of collapse must be performed in order to assess their vulnerability. In this article, the out-of-plane local mechanisms of collapse analysis is implemented by applying a new method of analysis based on a probabilistic approach. Usually information which are necessary for the implementation of the local mechanisms analyses are affected by uncertainty or are missing, therefore in lots of cases it is only possible to hypothesize them on the basis of the other buildings information collected during the on-site survey. In this context, the implementation of a Bayesian approach allows to deduce buildings lacking information (i.e. wall thickness and interstorey height) starting from certain collected data (i.e. facades height). The historical centre of Timisoara (Romania) is selected as the case study for the implementation of this new method of analysis, given the extension of the on-site survey already carried out in the area (information about more than 200 structural units have been collected) and the seismic vulnerability assessment on an urban scale already performed by applying a traditional method. Results obtained by adopting the two approaches are then compared and a validation and a calibration of the new one is carried out

The application of a Bayesian approach to assess the seismic vulnerability of historical centers

The seismic vulnerability of historical centers at a territorial scale cannot be assessed performing detailed analysis which are usually adopted at the single building scale. In fact, a traditional complete survey would be extremely time-consuming and not sustainable for this purpose. The approach described in this paper is based on the idea that it is possible to infer quantities which cannot be directly detected from buildings outside inspection starting from parameters that can be measured. In order to achieve this purpose, a Bayesian approach is applied, updating initial hypotheses when new data become available. In this context, the procedure herein proposed aims at applying a probabilistic approach instead of a deterministic one to define facades inter-storey height starting from buildings height knowledge. In order to validate the method, for out of plane local mechanisms of collapse (walls overturning), horizontal loads multiplier \uf0610 values are calculated and compared to results obtained by using data collected on-site

Líquenes como posibles agentes de deterioro de areniscas en las ruinas jesuíticas de San Ignacio Miní (provincia de Misiones, Argentina)

The ruins of San Ignacio Miní, in NE Argentina, Misiones Province, included by the UNESCO in the list of World Heritage in 1984, were built in the 18th century by the Guarani people under the supervision of the Jesuite Congregation. The ruins are located in a tropical weather zone, exposed to extreme conditions of heat and humidity affecting the rocks used in its construction. These rocks are identified as siliceous sandstones, mainly formed by rounded to subrounded clasts, with scarce angulose particles, containing 96% quartz. Weather characteristics encourage the growth of vascular plants as well as algae and mosses and other organisms that damage materials. Among these, there are 18 lichen species (belonging to 18 genera), 8 foliose, 3 fruticose and 7 crustose. The damaging action of these lichens has been observed through SEM observations and EDAX microanalysis of rock samples colonized by Caloplaca sp. and Buellia sp.Incluidas en la lista de Patrimonio Mundial por la UNESCO, las ruinas de San Ignacio Miní, en el NE de Argentina, provincia de Misiones, fueron construidas en el siglo XVIII por pobladores guaraníes supervisados por la Compañía de Jesús. Las ruinas se encuentran en una zona de clima tropical, expuestas a condiciones extremas de calor y humedad que alteran a las rocas empleadas en su construcción. Estas rocas se identifican como areniscas silíceas, formadas por clastos redondeados a sub-redondeados, con escasas partículas angulosas, con un contenido de 96,0% cuarzo. Las características del clima favorecen el desarrollo tanto de plantas vasculares como también de musgos, algas y otros organismos capaces de dañar a los materiales. Entre éstos se incluyen 18 especies de líquenes (pertenecientes a 18 géneros), 8 foliosos, 3 fruticosos y 7 crustosos. Las observaciones con SEM y los microanálisis EDE de muestras de roca colonizadas por Caloplaca sp. y Buellia sp sugieren que estos líquenes ejercen una acción negativa sobre la roca

Energy performances assessment of extruded and 3d printed polymers integrated into building envelopes for a south Italian case study

Plastic materials are increasingly becoming used in the building envelope, despite a lack of investigation on their effects. In this work, an extruded Acrylonitrile-Butadiene-Styrene panel has been tested as a second-skin layer in a ventilated facade system using a full-scale facility. The experimental results show that it is possible to achieve performances very similar to conventional materials. A numerical model has then been developed and used to investigate the performances of plastic and composite polymer panels as second-skin layers. The experimental data has been used to verify the behavior of the numerical model, from a thermal point of view, showing good reliability, with a root mean square error lower than 0.40◦C. This model has then been applied in different refurbishment cases upon varying: The polymer and the manufacturing technology (extruded or 3D-printed panels). Eight refurbishment case studies have been carried out on a typical office building located in Napoli (Italy), by means of a dynamic simulation software. The simulation results show that the proposed actions allow the reduction of the thermal and cooling energy demand (up to 6.9% and 3.1%, respectively), as well as the non-renewable primary energy consumption (up to 2.6%), in comparison to the reference case study

Density waves and 1/f1/f density fluctuations in granular flow

We simulate the granular flow in a narrow pipe with a lattice-gas automaton model. We find that the density in the system is characterized by two features. One is that spontaneous density waves propagate through the system with well-defined shapes and velocities. The other is that density waves are so distributed to make the power spectra of density fluctuations as $1/f^{\alpha}$ noise. Three important parameters make these features observable and they are energy dissipation, average density and the rougness of the pipe walls.Comment: Latex (with ps files appended