Special Issue "Volatile Compounds and Smell Chemicals (Odor and Aroma) of Food"

1openInternationalopenAprea, E.Aprea, E

Estenosis esofágica benigna en un felino asociada a la administración oral de doxiciclina. Terapéutica endoscópica

Se presenta un caso de estenosis esofágica en un felino, asociada a la administración oral de doxiciclina. Se describe su tratamiento endoscópico.

A numerical analysis of an Active Magnetic Regenerative Refrigerant system with a multi-layer regenerator

Abstract The Active Magnetic Regenerative Refrigeration (AMRR) cycle is a special kind of regenerator for the magnetic refrigerator, in which the magnetic material matrix works both as a refrigerating medium and as a heat regenerating medium, while the fluid flowing in the porous matrix works as a heat transfer medium. The performance of an AMRR cycle depends strongly on the behaviour of the adiabatic magnetization temperature change as a function of material temperature in the flow direction of the regenerator. In the present paper, a practical model for predicting the performance and efficiency of an AMRR cycle has been developed. The model simulates both the ferromagnetic material and the entire cycle of an AMR operating in conformity with a Brayton regenerative cycle. The model simulates different kinds of layered regenerators operating at their optimal operation point. The program study the Gd-x Tb1-x alloys as constituent materials for the regenerator over the temperature range 275 – 295 K, and Gdx Dy1-x alloys in the temperature range 260 – 280 K. With this model, the refrigeration capacity, the power consumption and consequently the coefficient of performance can be predicted. The results show a greater COP for the refrigerator based on the magnetocaloric technology compared with the COP of a classical vapour compression plant working between the same thermal levels

Determination of the compressor optimal working conditions

The replacement of environmentally unfriendly refrigerants and the energy saving demand have recently caused changes of the components and operation of the vapour compression plants; in particular, the compressors have been experiencing upgrades and modifications. The compression systems are usually designed for working under maximum load conditions, but most of the time these plants work under partial load conditions with compressor on–off cycles regulated by a thermostat. As for the variable speed compressor, the speed is continuously controlled to match the compressor capacity to the load required; this allows to save energy when compared to the thermostatic control. The aim of this paper is to identify the compressor current frequency that optimizes the energy, exergy and economy aspects. The determination of the optimum frequency for each working condition is key to build a control algorithm that allows the compressor speed to be continuously regulated by an inverter. This analysis has been applied to the reciprocating and scroll compressors and high energy savings have been achieved

Exergy analysis of a cooling system: experimental investigation on the consequences of the retrofit of R22 with R422D

In this article, the performances of a walk-in air cooler working with R22 and its substitute R422D are experimentally studied. To define a full comparison on the performance characteristics of R22 and R422D, both an energetic and an exergetic analyses are proposed. The experimental investigation was carried out considering four levels of refrigeration capacity: 920, 1340, 1925 and 2250 W. All tests were run at steady-state conditions and by keeping the value of the external air temperature equal to 22°C. The experimental analysis allowed the determination of the COP, the exergetic efficiency, the exergy flow destroyed in each component and other variables characterizing the working of the plant. The results demonstrated that COP of R422D is, on average, 20% lower than that of R22. Furthermore, for plant whose condenser is air cooled, R422D could lead to increase the fan speed or to adopt bigger blowers

Performances of thermostatic and electronic valves controlling the compressor capacity

The performance of the energy consumption of an electronic valve and a classical thermostatic valve has been compared when these expansion valves are adopted in a vapour compression plant subjected to a cold store. The main aim is to verify experimentally which type of expansion valve would be preferable from energy point of view when a classical thermostat or a fuzzy logic algorithm are used as the control system for the refrigeration capacity. The fuzzy logic-based control is able to modulate continuously the compressor speed through an inverter. The results show that with a fuzzy algorithm, the thermostatic expansion valve allows an energy saving of about 8% in comparison with the electronic valve. When on–off control is used, the electric energy consumption obtained both with the electronic valve and with the thermostatic valve is comparable

Analysis of some recharge solutions on varying the R407C composition

In the vapour compression plants possible leaks can vary the composition of a zeotropic refrigerant mixture. The main aim of this paper is to verify experimentally if the plant performances are restored with a proper recharge, when leaks are imposed. As for the R407C mixture the percentage of the less volatile component (R134a) increases, while the percentage of the more volatile components (R32 and R125) decreases when leaks occur. The experimental tests have been realized determining refrigerant leaks from the liquid receiver placed at the condenser outlet and measuring the properties in steady state condition. The recharge is realized in different ways: with R407C, with R134a and R410A or with R32 R125 and R134a. The different solutions are then compared from the economical point of view, in terms of COP, refrigeration power and air temperature at the evaporator outlet, adopting an iteration method. This method determines the real composition of a zeotropic mixture working in a compression plant, when only the temperature and pressure values at the expansion valve inlet and outlet are known

Correlation between oesophageal acid exposure and dyspeptic symptoms in patients with nonerosive reflux disease.

Oesophageal acidification induces dyspeptic symptoms in healthy individuals. This study aimed to evaluate the correlation between oesophageal acid exposure and dyspeptic symptoms in patients with nonerosive reflux disease. METHODS: A total of 68 patients with dominant symptoms of heartburn, negative upper gastrointestinal endoscopy and concomitant dyspeptic symptoms participated in the study. The severity of dyspepsia and reflux-related symptoms was evaluated, and 24-h gastro-oesophageal pH-monitoring study was performed in all patients at baseline and after 4 weeks of therapy with esomeprazole 40 mg. RESULTS: Oesophageal basal acid exposure was pathological in 43 patients and normal in 25 patients, with a similar prevalence and severity of individual dyspeptic symptoms in the two groups. A significant correlation between reflux and dyspepsia scores was observed in the subgroup of patients with normal, but not in those with abnormal pHmetry (r=0.4, P=0.04 and r=0.2 P=0.07, respectively). After esomeprazole, a reduction in severity of dyspepsia (>or=50% with respect to baseline) was observed, independent of improvement of reflux-associated symptoms. Improvement in dyspepsia was, however, similar in patients with normal and abnormal basal acid exposure (14/25 vs. 33/43, respectively, P=NS). CONCLUSION: Dyspeptic symptoms coexist in a subset of nonerosive reflux disease patients, but prevalence and severity of the symptoms seems to be independent of oesophageal acid exposure