INFLUENCE of THE EVAPORATOR POSITION IN STATIC DOMESTIC REFRIGERATORS

The temperature and velocity distributions of the air inside the cabinet of domestic refrigerators affect the quality of food products. If the consumer knows the location of warm and cold zones in the refrigerator, the products can be placed in the right zone. In addition, the knowledge of the thickness of thermal and hydrodynamic boundary layers near the evaporator and the other walls is also important. If the product is too close to the evaporator wall, freezing can occur, and if it is too close to warm walls, the products can be deteriorated. The aim of the present work is to develop a steady state computational fluid dynamics (CFD) model for domestic refrigerators working on natural convection regime. The Finite Volume Methodology is chosen as numerical procedure for discretizing the governing equations. The SIMPLE-Semi-Implicit Method for Pressure-Linked Equations algorithm applied to a staggered mesh was used for solving the pressure-velocity coupling problem. The Power-Law scheme is employed as interpolation function for the convective-diffusive terms, and the TDMA-Tri-Diagonal Matrix Algorithm is used to solve the systems of algebraic equations. The model is applied to a commercial static refrigerator, where the cabinet is considered an empty three-dimensional rectangular cavity with one drawer at the bottom of the cabinet, but without shelves. In order to analyze the velocity and temperature fields of the air flow inside the cabinet the evaporator temperature, Te, was varied from -20 degrees C to 0 degrees C, and nine different evaporator positions are evaluated for evaporator temperature of -15 degrees C. The cooling capacity of the evaporator for the steady state regime is also computed for each case. One can conclude that the vertical positioning of the evaporator inside the cabinet plays an important role on the temperature distribution inside the cabinet.

Simulação numérica da fase líquida na deposição de filmes finos via sol-gel: aplicações para dióxido de estanho

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Spatial variations at different observational scales and the seasonal distributions of stream macroalgae in a Brazilian subtropical region

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Air velocity and exposure time to ventilation affect body surface and rectal temperature of broiler chickens

Increasing air movement over poultry by using fans (ventilation) has become an accepted means of reducing environmental heat stress over the last several years. The purpose of this study was to evaluate the effect of air velocity and exposure time to ventilation on body surface and rectal temperature of broiler chickens. Male broiler chickens aged 36-42 days were placed in individual wire cages and exposed to five different air velocities (5.7, 4.2, 3.1, 2.4, or 1.8 m/sec). Throughout the experiment head, back, leg, and rectal temperatures were monitored every 10 min during a 30-min period for each air velocity. The data showed that exposure time to the wind affected (P<.05) leg and body temperature, with a rapid reduction being observed during the first 10 min. There was a reduction in leg temperature with air velocity of 2 m/sec; however, air velocity lower than 4.5 m/sec was not effective in decreasing head and back temperature. The results suggest that air velocity of 2 m/sec, in air temperature of 29 degrees C, improves heat loss in the birds. The data also indicate that exposure time to ventilation seems to be a critical point in the maintenance of bird thermal homeostasis.

Spontaneous Interblink Time Distributions in Patients with Graves' Orbitopathy and Normal Subjects

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Levenberg-Marquardt application to two-phase nonlinear parameter estimation for finned-tube coil evaporators

A procedure for calculation of refrigerant mass flow rate is implemented in the distributed numerical model to simulate the flow in finned-tube coil dry-expansion evaporators, usually found in refrigeration and air-conditioning systems. Two-phase refrigerant flow inside the tubes is assumed to be one-dimensional, unsteady, and homogeneous. In themodel the effects of refrigerant pressure drop and the moisture condensation from the air flowing over the external surface of the tubes are considered. The results obtained are the distributions of refrigerant velocity, temperature and void fraction, tube-wall temperature, air temperature, and absolute humidity. The finite volume method is used to discretize the governing equations. Additionally, given the operation conditions and the geometric parameters, the model allows the calculation of the refrigerant mass flow rate. The value of mass flow rate is computed using the process of parameter estimation with the minimization method of Levenberg-Marquardt minimization. In order to validate the developed model, the obtained results using HFC-134a as a refrigerant are compared with available data from the literature.

Model for determining flow diameter and economic velocity in water elevating systems

The purpose of this paper was to develop a model for calculating the economical flow diameter and velocity, by obtaining the economical diameter, using Swamee's friction factor equation, by minimizing the total annual cost. The application of the model to a regular supply condition showed that the diameter of the actual condition, 250 mm, compared with the diameter calculated by the mode, at the same tariff as that applied to the property ( ground), 284.1 mm, involved the necessity to generate, transmit, and distribute extra electrical energy, due to the higher load loss caused by the original diameter, approximately 30800 kWh/year. This means that in one year, the consumer would spend R$2,804.00 more on pumping cost alone.

Parturition intervals and distributions of parturitions by months of buffalo in Southern and South-eastern Brazil

Reproductive rate is an important component of economic success in livestock production. Parturition interval (IEP) is a direct measure of the productivity of the animal. Long IEP reduce the number of calves produced per year. The objective this study was to determine the distribution of parturitions across month and to evaluate factors affecting IEP. The data included 7,588 parturitions of Murrah, Mediterranean and Carabobo buffalo from 10 herds in Southern and South-eastern Brazil. The analysis of distribution of parturitions evaluated the effects of month, year and their interaction on birth date of calves by using a Chi-Square test in SAS PROC FREQ (SAS Institute, Cary, NC, USA). Parturition intervals (n = 2,630) were evaluated using analysis of variance in SAS PROC GLM. The model for IEP included the fixed effects of season (December to May = 1, June to November = 2), year, season x year, sex of the preceding parturition, age of weaning of the previous calf, and herd. All sources of variation were significant (P<0.0001) except sex of the preceding parturition (P <0.85). The mean IEP was 446.7 +/- 10.4 days, for seasons 1 and 2 IEP were 419.8 +/- 11.3 and 473.6 +/- 40.7 days, respectively, a difference of 54 days. As weaning age increased there was a lengthening of IEP. Buffalo in Brazil showed seasonal parturition with calving concentrated from January to April, although the frequency by month differed across years (P<0.0001). These months also had the lowest calving interval.

Spatial and seasonal distributions of Callinectes danae (Decapoda, Portunidae) in Ubatuba Bay, São Paulo, Brazil

The spatial and seasonal distributions of Callinectes danae Smith, 1869, in Ubatuba Bay, São Paulo, Brazil, were investigated as a part of a broad study on the general biology of portunids along the northern coast of São Paulo State, Brazil. Swimming crabs were collected during one year, from September 1995 to August 1996, along eight transects determined according to local physiographic features. Three replicate trawls were performed monthly at each transect. Depth. salinity, dissolved oxygen, temperature, organic matter content, and texture of the sediment were measured. Callinectes danae individuals were concentrated in shallow water close to the discharge of estuaries where the bottom is composed of fine and very fine sand. The species was more abundant in the warmer months. During the study period, C. danae exhibited continuous reproduction with a peak of reproductive intensity in June. Within this area, some sites are particularly favorable for C. danae establishment due to a combination of factors and prevailing local conditions.

On a symmetry in strong distributions

A strong Stieltjes distribution d psi(t) is called symmetric if it satisfies the propertyt(omega) d psi(beta(2)/t) = -(beta(2)/t)(omega) d psi(t), for t is an element of (a, b) subset of or equal to (0, infinity), 2 omega is an element of Z, and beta > 0.In this article some consequences of symmetry on the moments, the orthogonal L-polynomials and the quadrature formulae associated with the distribution are given. (C) 1999 Elsevier B.V. B.V. All rights reserved.

A mass-transportation approach to a one dimensional fluid mechanics model with nonlocal velocity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Distribution of Rhodophyta in streams from São Paulo State, southeastern Brazil

Distribution of Rhodophyta was investigated in 172 stream segments, which were sampled from May to October in 1992-1993 and 1996-1997 in six natural regions (parts of biomes or geological areas) of São Paulo State, southeastern Brazil. Red algae occurred in 60.5 % of stream segments sampled, a high frequency in comparison with other major surveys in the world (18-65 %). 17 species of freshwater red algae were found, of which the most widespread was Batrachospermum delicatulum occurring in 17 sites of five regions. The proportion of morphological types was as follows: gelatinous filaments (62.5 %), free filaments (19 %), tufts (12.5 %) and crusts (6 %); all but free filaments can be considered as having mechanisms to tolerate stress provoked by current velocity. No significant difference was found between the frequency distributions of variables measured for all streams and for those with red algae. Rhodophyta occurred under the following conditions (means): temperature (19.0 degrees C), current velocity (48 cm s(-1)), specific conductance (74 mu S cm(-1)), turbidity (8 NTU), oxygen (67.3 %) and pH (6.9 +/- 0.7). on the basis of species composition among the regions, the following patterns were evident: 1) the number of red algal species per region ranged from 1 to 10; 2) the highest proportion of sites with red algae (65-73 %) was found in hard water regions and in Atlantic rainforest, whereas the lowest (50 %) was found in tropical rainforest; 3) more than half of the species were exclusive from a single region, whereas the higher proportion of exclusive species was in the subtropical rainforest (50 %). No combination of stream variables was clearly associated with the occurrence of red algae for the regions as a whole. Species composition for streams and rivers of São Paulo State revealed higher similarities with other tropical regions and had few species in common with freshwater red algal floras of other continents.

The influence of an abdominal support for a dental stool in the distributions and electrical activity of the longissimus and the superior trapezius muscle in dentists

This study evaluated the influence an abdominal support attached to a traditional stool, of those used by dentists, has on the body's distribution of the electrical activity of the superior trapezius and the longissimus thoracic muscles of dental students during the execution of a clinical procedure. The results showed no significant difference in the body's distribution in the seat and backrest, but did reveal there was a weight discharge of 3.1 +/- 1.9% of dentist's body weight in the abdominal support. The 9 o'clock position proved to be the best position to perform clinical procedures. It was also observed that the position was closer to the body's axis.

Asymptotic soliton train solutions of Kaup-Boussinesq equations

Asymptotic soliton trains arising from a 'large and smooth' enough initial pulse are investigated by the use of the quasiclassical quantization method for the case of Kaup-Boussinesq shallow water equations. The parameter varying along the soliton train is determined by the Bohr-Sommerfeld quantization rule which generalizes the usual rule to the case of 'two potentials' h(0)(x) and u(0)(x) representing initial distributions of height and velocity, respectively. The influence of the initial velocity u(0)(x) on the asymptotic stage of the evolution is determined. Excellent agreement of numerical solutions of the Kaup-Boussinesq equations with predictions of the asymptotic theory is found. (C) 2003 Elsevier B.V. All rights reserved.

Local duality and charge symmetry violation in quark distributions

We use local quark-hadron duality to calculate the nucleon structure function as seen by neutrino and muon beams. Our result indicates a possible signal of charge symmetry violation at the parton level in the very large x region.