Conforto térmico em espaços públicos de passagem: estudos em cidades do Estado de São Paulo

This paper presents the results of a study on the thermal comfort in open urban spaces, undertaken in pedestrian streets located in the three towns, Campinas, Baurú, and Presidente Prudente, in the state of Sao Paulo. The study was developed as part of a more extensive project on thermal comfort in different kinds of open public spaces in Brazil. The methodology involved monitoring the microclimatic variables (air and globe temperature, humidity, air velocity and global solar radiation), and structured interviews, in order to assess the actual thermal comfort through the Actual Sensation Vote (ASV) and the personal users’ variables. The Physiological Equivalent Temperature (PET) was also calculated. The results show different limits for neutral temperature in each city: 20-29ºC for Campinas, 21-30 ºC for Bauru and 14-24 ºC for Presidente Prudente). However, 59.5% of the total sample (308 out of 519 individuals) indicated comfort limits ranging from 18 to 26 ºC, which is consistent with the limits proposed by Monteiro and Alucci for the city of Sao Paulo. These results can contribute to evaluate the thermal quality of other public spaces in the same towns.

Experiences on using closed-loop control systems for smoke control

The main objective of ventilation systems in case of fire is the reduction of the possible consequences by achieving the best possible conditions for the evacuation of the users and the intervention of the emergency services. In the last years, the required quick response of the ventilation system, from normal to emergency mode, has been improved by the use of automatic and semi-automatic control systems, what reduces the response times through the support to the operators decision taking, and the use of pre-defined strategies. A further step consists on the use of closedloop algorithms, which takes into account not only the initial conditions but their development (air velocity, traffic situation, etc), optimizing the quality of the smoke control process

Experiences on the specification of algorithms for fire and smoke control in road tunnels

The main objective of ventilation systems in case of fire is the reduction of the possible consequences by achieving the best possible conditions for the evacuation of the users and the intervention of the emergency services. The required immediate transition, from normal to emergency functioning of the ventilation equipments, is being strengthened by the use of automatic and semi-automatic control systems, what reduces the response times through the help to the operators, and the use of pre-defined strategies. A further step consists on the use of closed-loop algorithms, which takes into account not only the initial conditions but their development (air velocity, traffic situation, etc.), optimizing smoke control capacity.

A 2D computational parametric analysis of the sheltering effect of fences on a railway vehicle standing on a bridge and experiencing crosswinds

In a crosswind scenario, the risk of high-speed trains overturning increases when they run on viaducts since the aerodynamic loads are higher than on the ground. In order to increase safety, vehicles are sheltered by fences that are installed on the viaduct to reduce the loads experienced by the train. Windbreaks can be designed to have different heights, and with or without eaves on the top. In this paper, a parametric study with a total of 12 fence designs was carried out using a two-dimensional model of a train standing on a viaduct. To asses the relative effectiveness of sheltering devices, tests were done in a wind tunnel with a scaled model at a Reynolds number of 1 × 105, and the train’s aerodynamic coefficients were measured. Experimental results were compared with those predicted by Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations of flow, showing that a computational model is able to satisfactorily predict the trend of the aerodynamic coefficients. In a second set of tests, the Reynolds number was increased to 12 × 106 (at a free flow air velocity of 30 m/s) in order to simulate strong wind conditions. The aerodynamic coefficients showed a similar trend for both Reynolds numbers; however, their numerical value changed enough to indicate that simulations at the lower Reynolds number do not provide all required information. Furthermore, the variation of coefficients in the simulations allowed an explanation of how fences modified the flow around the vehicle to be proposed. This made it clear why increasing fence height reduced all the coefficients but adding an eave had an effect mainly on the lift force coefficient. Finally, by analysing the time signals it was possible to clarify the influence of the Reynolds number on the peak-to-peak amplitude, the time period and the Strouhal number.

Train-induced pressure on pedestrians

A simple analytical model for the train-induced flow and its effects on pedestrians is presented in this paper. The expressions developed for the induced air velocity and pressure on the pedestrian surface, as well as their dependence with time, are obtained from unsteady potential theory. The relevant parameters and their effects are analysed, in particular the sensitivity of the pressure coefficient and its rate of change on the train and pedestrian transverse size, the distance to the tracks and the pressure measurement location on the pedestrian surface. In spite of the extreme simplicity of the model and the expressions obtained, good correlation is observed with previously existing experiments. With this work, an absence of published studies concerning analytical approaches to the problem of vehicle-induced pressure on pedestrians is intended to be covered, allowing for simplified testing procedures.

Mathematical modeling of drying process of unripe banana slices

Unripe banana flour (UBF) production employs bananas not submitted to maturation process, is an interesting alternative to minimize the fruit loss reduction related to inappropriate handling or fast ripening. The UBF is considered as a functional ingredient improving glycemic and plasma insulin levels in blood, have also shown efficacy on the control of satiety, insulin resistance. The aim of this work was to study the drying process of unripe banana slabs (Musa cavendishii, Nanicão) developing a transient drying model through mathematical modeling with simultaneous moisture and heat transfer. The raw material characterization was performed and afterwards the drying process was conducted at 40 ºC, 50 ºC e 60 ºC, the product temperature was recorded using thermocouples, the air velocity inside the chamber was 4 m·s-1. With the experimental data was possible to validate the diffusion model based on the Fick\'s second law and Fourier. For this purpose, the sorption isotherms were measured and fitted to the GAB model estimating the equilibrium moisture content (Xe), 1.76 [g H2O/100g d.b.] at 60 ºC and 10 % of relative humidity (RH), the thermophysical properties (k, Cp, ?) were also measured to be used in the model. Five cases were contemplated: i) Constant thermophysical properties; ii) Variable properties; iii) Mass (hm), heat transfer (h) coefficient and effective diffusivity (De) estimation 134 W·m-2·K-1, 4.91x10-5 m-2·s-1 and 3.278?10-10 m·s-2 at 60 ºC, respectively; iv) Variable De, it presented a third order polynomial behavior as function of moisture content; v) The shrinkage had an effect on the mathematical model, especially in the 3 first hours of process, the thickness experienced a contraction of about (30.34 ± 1.29) % out of the initial thickness, finding two decreasing drying rate periods (DDR I and DDR II), 3.28x10-10 m·s-2 and 1.77x10-10 m·s-2, respectively. COMSOL Multiphysics simulations were possible to perform through the heat and mass transfer coefficient estimated by the mathematical modeling.

Effect of harvest time and drying on supersweet sweet corn seed quality

A supersweet sweet corn hybrid, Pacific H5, was grown under field conditions in South-East Queensland to study the effects of harvest time and drying conditions on seed quality. Cobs were harvested at different times to obtain seed with two moisture percentage ranges (20-30% and 40-50%) and dried to 12% moisture under different combinations of drying temperatures (30 degrees C, 40 degrees C and 50 degrees C) and air velocities (1.25 m/s, 2.75 m/s and 4.30 m/s). Dried seed was stored at 30 degrees C with bimonthly monitoring of seed quality for 12 months. For standard as well as cold test germinations, statistical analysis yielded significant main effects for temperature, air velocity and harvest moisture content and significant interactions for drying temperature by harvest moisture and drying temperature by air velocity. Germination at the beginning of storage was unaffected by drying temperatures up to 40 degrees C regardless of harvest moisture but was lower at 50 degrees C for higher moisture. However, germination at the end of the storage period of 12 months was greatest for seed harvested at higher moisture and dried at temperatures up to 40 degrees C. Germination was not affected by air velocity for drying temperatures up to 40 degrees C but at 50 degrees C it generally decreased with increase in air velocity. To slow down seed deterioration during storage, it is recommended that sweet corn seed should be harvested at a higher moisture range (40-50%) and dried at 40 degrees C and 4.30 m/s air velocity. The drying temperature can be raised to 50 degrees C for seed harvested at a low moisture range (20-30%) provided the air velocity is kept low (1.25 m/s).

The Single drop drying of heat-sensitive materials

The literature relating to the principles and practice of drying of materials, particularly those susceptible to thermal degradation or undesirable loss of volatile components, has been reviewed. Single droplets of heat-sensitive materials were dried whilst suspended in a horizontal wind tunnel from a specially-designed, rotating thermocouple which enabled direct observation of drying behaviour and continuous measurement of droplet temperature as drying progressed. The effects of drying air temperature and initial solids concentration on the potency of various antibiotics, viz. ampicillin, chloramphenicol, oxytetracycline, streptomycin and tetracycline, were assessed using a modified Drug Sensitivity Testing technique. Only ampicillin was heat-sensitive at temperatures above 100°C, e.g. at an air temperature of 115°C its zone diameter was reduced from 100% to 45%. Selected enzymes, viz. dextran sucrase and invertase, were also dried and their residual activities determined by High Performance Liquid Chromatography. The residual activity of dextran sucrase was rapidly reduced at temperatures above 65°C, and the residual activity of invertase reduced rapidly at temperatures above 65°C; but drying with short residence times will retain most of its activity. The performance of various skin-forming encapsulants, viz. rice and wheat starch, dextrin, coffee, skim milk, fructose, gelatine 60 and 150 Bloom, and gum arabic, was evaluated to determine their capabilities for retention of ethanol as a model volatile, under different operating conditions. The effects of initial solids concentration, air velocity and temperature were monitored for each material tested. Ethanol content was analysed by Gas Liquid Chromatography and in some cases dried crusts were removed for examination. Volatiles retention was concluded to depend in all cases upon the rate and nature of the skin formation and selective diffusion phenomena. The results provided further insight into the inter-relationship between temperature, residence time and thermal degradation of heat-sensitive materials. They should also assist in selection of the preferred dryer for such materials, and of the operating parameter to enable maximum retention of the required physico-chemical characteristics in the dried materials.

Solids mixing and segregation in a gas spout-fluid bed-effect of the distributor design

This work is concerned with the assessment of a newer version of the spout-fluid bed where the gas is supplied from a common plenum and the distributor controls the operational phenomenon. Thus the main body of the work deals with the effect of the distributor design on the mixing and segregation of solids in a spout-filled bed. The effect of distributor design in the conventional fluidised bed and of variation of the gas inlet diameter in a spouted bed were also briefly investigated for purpose of comparison. Large particles were selected for study because they are becoming increasingly important in industrial fluidised beds but have not been thoroughly investigated. The mean particle diameters of the fraction ranged from 550 to 2400 mm, and their specific gravity from 0.97 to 2.45. Only work carried out with binary systems is reported here. The effect of air velocity, particle properties, bed height, the relative amount of jetsam and flotsam and initial conditions on the steady-state concentration profiles were assessed with selected distributors. The work is divided into three sections. Sections I and II deal with the fluidised bed and spouted bed systems. Section III covers the development of the spout-filled bed and its behaviour with reference to distributor design and it is shown how benefits of both spouting and fluidising phenomena can be exploited. In the fluidisation zone, better mixing is achieved by distributors which produce a large initial bubble diameter. Some common features exist between the behaviour of unidensity jetsam-rich systems and different density flotsam-rich systems. The shape factor does not seem to have an affect as long as it is only restricted to the minor component. However, in the case of the major component, particle shape significantly affects the final results. Studies of aspect ratio showed that there is a maximum (1.5) above which slugging occurs and the effect of the distributor design is nullified. A mixing number was developed for unidensity spherical rich systems, which proved to be extremely useful in quantifying the variation in mixing and segregation with changes in distributor design.

A study of the aerodynamic characteristics of captor hoods in local exhaust ventilation systems

The research objectives were:- 1.To review the literature to establish the factors which have traditionally been regarded as most crucial to the design of effectlve exhaust ventilation systems. 2. To design, construct, install and calibrate a wind tunnel. 3. To develop procedures for air velocity measurement followed by a comprehensive programme of aerodvnamic data collection and data analysis for a variety of conditions. The major research findings were:- a) The literature in the subject is inadequate. There is a particular need for a much greater understanding of the aerodynamics of the suction flow field. b) The discrepancies between the experimentally observed centre-line velocities and those predicted by conventional formulae are unacceptably large. c) There was little agreement between theoretically calculated and observed velocities in the suction zone of captor hoods. d) Improved empirical formulae for the prediction of centre-line velocity applicable to the classical geometrically shaped suction openings and the flanged condition could be (and were) derived. Further analysis of data revealed that: - i) Point velocity is directly proportional to the suction. flow rate and the ratio of the point velocity to the average face velocity is constant. ii) Both shape, and size of the suction opening are significant factors as the coordinates of their points govern the extent of the effect of the suction flow field. iii) The hypothetical ellipsoidal potential function and hyperbolic streamlines were found experimentally to be correct. iv) The effect of guide plates depends on the size, shape and the angle of fitting. The effect was to very approximately double the suction velocity but the exact effect is difficult to predict. v) The axially symmetric openings produce practically symmetric flow fields. Similarity of connection pieces between the suction opening and the main duct in each case is essential in order to induce a similar suction flow field. Additionally a pilot study was made in which an artificial extraneous air flow was created, measured and its interaction with the suction flow field measured and represented graphically.

Technical and economic study of plantain food products

Plantain (Banana-Musa AAB) is a widely growing but commercially underexploited tropical fruit. This study demonstrates the processing of plantain to flour and extends its use and convenience as a constituent of bread, cake and biscuit. Plantain was peeled, dried and milled to produce flour. Proximate analysis was carried out on the flour to determine the food composition. Drying at temperatures below 70ºC produced light coloured plantain flour. Experiments were carried out to determine the mechanism of drying, the heat and mass transfer coefficients, effect of air velocity, temperature and cube size on the rate of drying of plantain cubes. The drying was diffusion controlled. Pilot scale drying of plantain cubes in a cabinet dryer showed no significant increase of drying rate above 70ºC. In the temperature range found most suitable for plantain drying (ie 60 to 70ºC) the total drying time was adequately predicted using a modified equation based on Fick's Law provided the cube temperature was taken to be about 5ºC below the actual drying air temperature. Studies of baking properties of plantain flour revealed that plantain flour can be substituted for strong wheat flour up to 15% for bread making and up to 50% for madeira cake. A shortcake biscuit was produced using 100% plantain flour and test-marketed. Detailed economic studies showed that the production of plantain fruit and its processing into flour would be economically viable in Nigeria when the flour is sold at the wholesale price of NO.65 per kilogram provided a minimum sale of 25% plantain suckers. There is need for government subsidy if plantain flour is to compete with imported wheat flour. The broader economic benefits accruing from the processing of plantain fruit into flour and its use in bakery products include employment opportunity, savings in foreign exchange and stimulus to home agriculture.

Avaliação térmica e desempenho do processo de secagem de misturas de graviola e leite em secador de leito de jorro

The soursop (A. muricata) is a fruit rich in minerals especially the potassium content. The commercialization of soursop in natura and processed has increased greatly in recent years. Drying fruit pulp in order to obtain the powdered pulp has been studied, seeking alternatives to ensure the quality of dehydrated products at a low cost of production. The high concentration of sugars reducing present in fruits causes problems of agglomeration and retention during fruit pulp drying in spouted bed dryers. On the other hand in relation to drying of milk and fruit pulp with added milk in spouted bed, promising results are reported in the literature. Based on these results was studied in this work drying of the pulp soursop with added milk in spouted bed with inert particles. The tests were based on a 24 factorial design were evaluated for the effects of milk concentration (30 to 50% m/m), drying air temperature (70 to 90 °C), intermittency time (10 to 14 min), and ratio of air velocity in relation to the minimum spout (1.2 to 1.5) on the rate of production, of powder moisture, yield, rate of drying and thermal efficiency of the process. There were physical and chemical analysis of mixtures, of powders and of mixtures reconstituted by rehydration powders. Were adjusted statistical models of first order to data the rate of production, yield and thermal efficiency, that were statistically significant and predictive. An efficiency greater than 40% under the conditions of 50% milk mixture, at 70 ° C the drying air temperature and 1.5 for the ratio between the air velocity and the minimum spout has been reached. The intermittency time showed no significant effect on the analyzed variables. The final product had moisture in the range of 4.18% to 9.99% and water activity between 0.274 to 0.375. The mixtures reconstituted by rehydration powders maintained the same characteristics of natural blends.

Design and development of a diagonal-airflow batch dryer for spatial drying homogeneity

Das Verfahren der Lebensmitteltrocknung wird häufig angewendet, um ein Produkt für längere Zeit haltbar zu machen. Obst und Gemüse sind aufgrund ihres hohen Wassergehalts leicht verderblich durch biochemische Vorgänge innerhalb des Produktes, nicht sachgemäße Lagerung und unzureichende Transportmöglichkeiten. Um solche Verluste zu vermeiden wird die direkte Trocknung eingesetzt, welche die älteste Methode zum langfristigen haltbarmachen ist. Diese Methode ist jedoch veraltet und kann den heutigen Herausforderungen nicht gerecht werden. In der vorliegenden Arbeit wurde ein neuer Chargentrockner, mit diagonalem Luftstömungskanal entlang der Länge des Trocknungsraumes und ohne Leitbleche entwickelt. Neben dem unbestreitbaren Nutzen der Verwendung von Leitblechen, erhöhen diese jedoch die Konstruktionskosten und führen auch zu einer Erhöhung des Druckverlustes. Dadurch wird im Trocknungsprozess mehr Energie verbraucht. Um eine räumlich gleichmäßige Trocknung ohne Leitbleche zu erreichen, wurden die Lebensmittelbehälter diagonal entlang der Länge des Trockners platziert. Das vorrangige Ziel des diagonalen Kanals war, die einströmende, warme Luft gleichmäßig auf das gesamte Produkt auszurichten. Die Simulation des Luftstroms wurde mit ANSYS-Fluent in der ANSYS Workbench Plattform durchgeführt. Zwei verschiedene Geometrien der Trocknungskammer, diagonal und nicht diagonal, wurden modelliert und die Ergebnisse für eine gleichmäßige Luftverteilung aus dem diagonalen Luftströmungsdesign erhalten. Es wurde eine Reihe von Experimenten durchgeführt, um das Design zu bewerten. Kartoffelscheiben dienten als Trocknungsgut. Die statistischen Ergebnisse zeigen einen guten Korrelationskoeffizienten für die Luftstromverteilung (87,09%) zwischen dem durchschnittlich vorhergesagten und der durchschnittlichen gemessenen Strömungsgeschwindigkeit. Um den Effekt der gleichmäßigen Luftverteilung auf die Veränderung der Qualität zu bewerten, wurde die Farbe des Produktes, entlang der gesamten Länge der Trocknungskammer kontaktfrei im on-line-Verfahren bestimmt. Zu diesem Zweck wurde eine Imaging-Box, bestehend aus Kamera und Beleuchtung entwickelt. Räumliche Unterschiede dieses Qualitätsparameters wurden als Kriterium gewählt, um die gleichmäßige Trocknungsqualität in der Trocknungskammer zu bewerten. Entscheidend beim Lebensmittel-Chargentrockner ist sein Energieverbrauch. Dafür wurden thermodynamische Analysen des Trockners durchgeführt. Die Energieeffizienz des Systems wurde unter den gewählten Trocknungsbedingungen mit 50,16% kalkuliert. Die durchschnittlich genutzten Energie in Form von Elektrizität zur Herstellung von 1kg getrockneter Kartoffeln wurde mit weniger als 16,24 MJ/kg und weniger als 4,78 MJ/kg Wasser zum verdampfen bei einer sehr hohen Temperatur von jeweils 65°C und Scheibendicken von 5mm kalkuliert. Die Energie- und Exergieanalysen für diagonale Chargentrockner wurden zudem mit denen anderer Chargentrockner verglichen. Die Auswahl von Trocknungstemperatur, Massenflussrate der Trocknungsluft, Trocknerkapazität und Heiztyp sind die wichtigen Parameter zur Bewertung der genutzten Energie von Chargentrocknern. Die Entwicklung des diagonalen Chargentrockners ist eine nützliche und effektive Möglichkeit um dei Trocknungshomogenität zu erhöhen. Das Design erlaubt es, das gesamte Produkt in der Trocknungskammer gleichmäßigen Luftverhältnissen auszusetzen, statt die Luft von einer Horde zur nächsten zu leiten.

Correlations between thermal environment and egg quality of two layer commercial strains

Heat stress limits the productivity of laying hens, as reflected by egg production and egg quality. The present study aimed at showing the correlations between egg quality parameters and environmental variables recorded on the day eggs were laid and on the previous days. Birds were housed in battery cages in a commercial poultry house. Main component analyses were used to verify associations between environmental and production variables, and Pearson's linear correlation tests were used to further investigate those associations. Analyses were carried out separately for to layer strains, Dekalb® White and Hy-Line® w36, and the variables egg weight (g), eggshell weight (g), specific gravity (g/cm³) and eggshell percentage (%) were compared with the environmental variables of the same day of the production, and one, two, three, and four days before egg production. Sound intensity measured inside the houses was positively associated with the quality parameters of eggs produced on the next day. Thermal environmental variables affected the egg quality differently in each strain, particularly air temperature, internal roof tile temperature, relative humidity, and air velocity. Ammonia concentration measured inside the houses was lower than 1ppm, and did not affect production performance.

Experimental and modeling studies of forced convection storage and drying systems for sweet potatoes

Sweet potato is an important strategic agricultural crop grown in many countries around the world. The roots and aerial vine components of the crop are used for both human consumption and, to some extent as a cheap source of animal feed. In spite of its economic value and growing contribution to health and nutrition, harvested sweet potato roots and aerial vine components has limited shelf-life and is easily susceptible to post-harvest losses. Although post-harvest losses of both sweet potato roots and aerial vine components is significant, there is no information available that will support the design and development of appropriate storage and preservation systems. In this context, the present study was initiated to improve scientific knowledge about sweet potato post-harvest handling. Additionally, the study also seeks to develop a PV ventilated mud storehouse for storage of sweet potato roots under tropical conditions. In study one, airflow resistance of sweet potato aerial vine components was investigated. The influence of different operating parameters such as airflow rate, moisture content and bulk depth at different levels on airflow resistance was analyzed. All the operating parameters were observed to have significant (P < 0.01) effect on airflow resistance. Prediction models were developed and were found to adequately describe the experimental pressure drop data. In study two, the resistance of airflow through unwashed and clean sweet potato roots was investigated. The effect of sweet potato roots shape factor, surface roughness, orientation to airflow, and presence of soil fraction on airflow resistance was also assessed. The pressure drop through unwashed and clean sweet potato roots was observed to increase with higher airflow, bed depth, root grade composition, and presence of soil fraction. The physical properties of the roots were incorporated into a modified Ergun model and compared with a modified Shedd’s model. The modified Ergun model provided the best fit to the experimental data when compared with the modified Shedd’s model. In study three, the effect of sweet potato root size (medium and large), different air velocity and temperature on the cooling/or heating rate and time of individual sweet potato roots were investigated. Also, a simulation model which is based on the fundamental solution of the transient equations was proposed for estimating the cooling and heating time at the centre of sweet potato roots. The results showed that increasing air velocity during cooling and heating significantly (P < 0.05) affects the cooling and heating times. Furthermore, the cooling and heating times were significantly different (P < 0.05) among medium and large size sweet potato roots. Comparison of the simulation results with experimental data confirmed that the transient simulation model can be used to accurately estimate the cooling and heating times of whole sweet potato roots under forced convection conditions. In study four, the performance of charcoal evaporative cooling pad configurations for integration into sweet potato roots storage systems was investigated. The experiments were carried out at different levels of air velocity, water flow rates, and three pad configurations: single layer pad (SLP), double layers pad (DLP) and triple layers pad (TLP) made out of small and large size charcoal particles. The results showed that higher air velocity has tremendous effect on pressure drop. Increasing the water flow rate above the range tested had no practical benefits in terms of cooling. It was observed that DLP and TLD configurations with larger wet surface area for both types of pads provided high cooling efficiencies. In study five, CFD technique in the ANSYS Fluent software was used to simulate airflow distribution in a low-cost mud storehouse. By theoretically investigating different geometries of air inlet, plenum chamber, and outlet as well as its placement using ANSYS Fluent software, an acceptable geometry with uniform air distribution was selected and constructed. Experimental measurements validated the selected design. In study six, the performance of the developed PV ventilated system was investigated. Field measurements showed satisfactory results of the directly coupled PV ventilated system. Furthermore, the option of integrating a low-cost evaporative cooling system into the mud storage structure was also investigated. The results showed a reduction of ambient temperature inside the mud storehouse while relative humidity was enhanced. The ability of the developed storage system to provide and maintain airflow, temperature and relative humidity which are the key parameters for shelf-life extension of sweet potato roots highlight its ability to reduce post-harvest losses at the farmer level, particularly under tropical climate conditions.