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      Assessment of evaporative cooling efficiency in greenhouses equiped with wetted porous plates Translated title: Evaluación de la eficiencia de equipos de enfriamiento evaporativo usando placas porosas en invernaderos

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          Abstract

          Abstract The main objective of this study was to experimentally validate a mechanistic model for predicting the cooling efficiency (η) of wetted porous plates built with expanded clay. The expanded clay material was physically characterized by specific mass, surface area, and volume. The model was validated with dry bulb temperature (Tdb, °C) and air relative humidity (RH, %) data, which were continuously monitored in two different points, upstream and downstream the direction of the air passing through the porous plate. Data collection was carried out consecutively for a period of 10 days, between 11:00 a.m. and 4:00 p.m. Average values for η, simulated and observed, were 74.8 ± 7.4% and 68.3 ± 8.3%, respectively. Based on the developed model, it was observed that η was higher than 40% for Tdb > 30 °C and constant RH at 45%. The simulation for predictions indicates that the increase in the air temperature greater than 20 °C may affect negatively the production in greenhouses from states located in tropical and subtropical countries as Minas Gerais, Brazil, if some design criteria in the evaporative cooling system are not revised.

          Translated abstract

          Resumen El objetivo principal de este estudio fue validar experimentalmente un modelo mecánistico para predecir la eficacia de enfriamiento (η) de placas porosas construidas con arcilla expandida. El material de arcilla expandida fue físicamente caracterizado encontrando su masa específica, área superficial y volumen. El modelo fue validado con datos de temperatura de bulbo seco (Tdb, ° C) y humedad relativa del aire (humedad relativa,%) que fueron continuamente monitoreados en dos puntos diferentes, en contra y a favor de la dirección del aire que pasa a través de la placa porosa. La recolección de datos se llevó a cabo de forma consecutiva durante un período de 10 días entre las 11:00 y 4:00 p.m. Los valores medios de η, simulados y observados, fueron 74,8 ± 7,4% y 68,3 ± 8,3%, respectivamente. Basado en el modelo desarrollado, se observó que η fue mayor del 40% para Tdb> 30 ° C y HR constante en 45%. La simulación indicó que el aumento de la temperatura del aire puede afectar negativamente la producción en invernaderos en Estados como Minas Gerais, Brazil, si no se revisan algunos criterios de diseño en el sistema de enfriamiento por evaporación.

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          Performance evaluation of three different types of local evaporative cooling pads in greenhouses in Sudan

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            Numerical Calculation of Psychrometric Properties in SI Units

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              Impact of global warming on beef cattle production cost in Brazil

              Global warming is affecting agribusiness in its economic aspects. Therefore, the prediction of the evolution of Brazilian beef cattle production cost was made using the IPCC forecast scenario for global warming. The methodology consisted of two steps: (i) the development of a fuzzy model that estimated the grazing land capacity (RP) decrease risk as a function of the changes in the average total rain index, air temperature and increase in extension of the dry season; and (ii) the design of an algorithm for predicting the decrease in production as function of the RPfuzzy model, that results in the impact in beef cattle productivity, and consequent increase in production costs. Historical environmental data from important producing counties in the Cerrado were organized and a set of fuzzy Gaussian functions were developed, and three possible settings (optimistic, medium and pessimistic) were considered. The decrease in beef cattle productivity was estimated using the losses in production due to the increase in air temperature and vulnerability of pasture capacity. The boundary settings for the total increase of production cost scenario used the number of animals per area of grazing land, the adoption of grain supplement and its future scenario; and the result output function pointed to a threshold within a variation from an increase in production cost of 80% (optimistic) to 160% (pessimistic). Under the optimistic scenario the total cost of Brazilian beef cattle production in the Cerrado became near to US\(2.88 kg-1, while in the pessimistic scenario this cost reached US\) 4.16 kg-1, challenging the international competitiveness of this economic segment.
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                Author and article information

                Contributors
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Journal
                dyna
                DYNA
                Dyna rev.fac.nac.minas
                Universidad Nacional de Colombia (Medellín, Antioquia, Colombia )
                0012-7353
                December 2017
                : 84
                : 203
                : 118-125
                Affiliations
                [3] Rondonópolis Mato Grosso orgnameUniversidade Federal de Mato Grosso orgdiv1Departamento de Ingeniería Agrícola Brazil joframluiz@ 123456gmail.com
                [4] Medellín Antioquía orgnameUniversidad Nacional de Colombia orgdiv1Facultad de Ciencias Agrarias Colombia aosorio@ 123456unal.edu.co
                [1] Lavras Minas Gerais orgnameUniversidade Federal de Lavras orgdiv1Departamento de Ingeniería Brazil flavio.damasceno@ 123456deg.ufla.br
                [2] Saint-Genès-Champanelle orgnameInstitut National de la Recherche Agronomique France luciano.mendes@ 123456inra.fr
                Article
                S0012-73532017000400118
                10.15446/dyna.v84n203.59564
                1ecc5e40-b921-405a-b0ac-0edf34e02c9a

                This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

                History
                : 25 September 2017
                : 12 September 2016
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 30, Pages: 8
                Product

                SciELO Colombia


                Invernadero,modelo matemático,simulación,transferencia de calor y masa.,Greenhouse,mathematical modeling,simulation,heat and mass transfer.

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