Loading...
8 results
Search Results
Now showing 1 - 8 of 8
- Experimental study of a photovoltaic solar dryerPublication . Grilo, Tiago Santos; Pires, Luís; Silva, Pedro Dinho da; Nunes, JoséThis experimental work focuses specifically on the development and construction of a prototype and the study of different strategies to optimize food drying from solar energy. The main study variable is the efficiency of the solar dryer. In order to optimize the system and increase the drying rate it was decided to use a photovoltaic panel which will power a resistive load - thus obtaining higher air temperature which enters the drying chamber. First, are shown some considerations about the range of applications and methods of harnessing solar energy, emphasizing how important it is to conserve food products through solar drying. To elucidate this concept existing models of solar dryers are reviewed, highlighting the most efficient and representative of each category, in order to understand the work already developed in this area. All experimental results were obtained in drying trials during the summer of 2016. These results demonstrate the advantages and disadvantages of each strategy adopted. Calculations were made and performance parameters discussed, allowing to take conclusions about the modus operandi and design of this type of units. In order to benefit the most of the energy generated, and thus reduce waste, certain measures have been identified that promote the correct use of PV panels for drying agricultural products. All of this work is for the purpose of being adopted by local farmers.
- Current and Future Trends of Refrigerants DevelopmentPublication . Duarte, M. V.; Silva, Pedro Dinho da; Pires, Luís; Gaspar, Pedro DinisIn this chapter is addressed the thematic of refrigerants: its historical evolution; properties; legislation applied in the area and future trends. The first refrigerant being marketed on a large scale was ethyl ether (R610), in 1834. Since then, the evolution of the utilized refrigerants was stimulated, initially due to constructive issues in the refrigeration system and later to environmental issues. This evolution may be divided into four generations: 1st use of any fluid that worked; 2nd safety and durability of the equipment; 3rd ozone layer protection and 4th increase of global warming concerns. During the process of evolution many refrigerants were tested to understanding of their properties. Currently, environmental concerns are taken as guide in the search for new refrigerants. The most promising refrigerants to be used in future are the HFEs, HFOs and HFCs with low-GWP, natural refrigerants and blends between (HCs/HFCs and HFCs/HFOs) refrigerants.
- Current and Future Trends of Refrigerants DevelopmentPublication . Duarte, M.V.; Pires, Luís; Silva, Pedro Dinho da; Gaspar, Pedro DinisIn this chapter is addressed the thematic of refrigerants: its historical evolution; properties; legislation applied in the area and future trends. The first refrigerant being marketed on a large scale was ethyl ether (R610), in 1834. Since then, the evolution of the utilized refrigerants was stimulated, initially due to constructive issues in the refrigeration system and later to environmental issues. This evolution may be divided into four generations: 1st use of any fluid that worked; 2nd safety and durability of the equipment; 3rd ozone layer protection and 4th increase of global warming concerns. During the process of evolution many refrigerants were tested to understanding of their properties. Currently, environmental concerns are taken as guide in the search for new refrigerants. The most promising refrigerants to be used in future are the HFEs, HFOs and HFCs with low-GWP, natural refrigerants and blends between (HCs/HFCs and HFCs/HFOs) refrigerants.
- Current and Future Trends of Refrigerants DevelopmentPublication . Duarte, M. V.; Silva, Pedro Dinho da; Pires, Luís; Gaspar, Pedro DinisIn this chapter is addressed the thematic of refrigerants: its historical evolution; properties; legislation applied in the area and future trends. The first refrigerant being marketed on a large scale was ethyl ether (R610), in 1834. Since then, the evolution of the utilized refrigerants was stimulated, initially due to constructive issues in the refrigeration system and later to environmental issues. This evolution may be divided into four generations: 1st use of any fluid that worked; 2nd safety and durability of the equipment; 3rd ozone layer protection and 4th increase of global warming concerns. During the process of evolution many refrigerants were tested to understanding of their properties. Currently, environmental concerns are taken as guide in the search for new refrigerants. The most promising refrigerants to be used in future are the HFEs, HFOs and HFCs
- The cherry drying as a complementary conservation process to conservation in coldPublication . Nunes, José; Silva, Pedro Dinho da; Pires, Luís; Gaspar, Pedro Dinis; Andrade, Luís P.Cherry is greatly enjoyed by consumers because of its excellent organoleptic and nutritional characteristics. This fruit is of the non-climacteric type, which forces its immediate commercialization after harvesting or else it should be properly conserved in cold. Every year there is a big waste of fresh cherry because he could not be marketed before deteriorating both in cooling chambers, or even in their own cherry trees due to a rapid ripening. In this project, the process of making cherry raisins is studied so as to provide increased use of fresh cherry. For that purpose, three different processes of dehydration of fresh cherry have been used, such as freeze drying, hot-air drying and solar drying. Three types of samples of pitted cherries were also used - natural cherry, blanching cherry and bleaching cherry with osmotic solution of fructose. In order to assess the performance of the dryers the curves of drying rate were determined and to assess the quality of the cherry raisins, fundamental parameters were determined, namely moisture content, water activity (aw), texture, total soluble solids and total acidity. The results show that the drying rate of cherry samples is similar in the lyophilizer and hot air dryer, and yet faster in the latter. The dryer with lower rate drying and hence with higher drying time was the solar dryer. The characteristics of the cherry raisins depend on the type of dryer used and the pre-treatment used. The blanching pretreatment proved to be the most suitable. Regarding dryers, the solar dryer provided good quality cherry raisins, showing great potential at industrial level with the advantage of not consuming energy.
- Characterization of the thermal performance of an outdoor telecommunication cabinetPublication . Silva, Pedro Dinho da; Pires, Luís; Patrício, Carlos Miguel Rosado; Gaspar, Pedro DinisThis work describes the analysis of the thermal performance of an outdoor telecommunication cabinet (OTC) using the computational tool DesignBuilder. The simulation results are compared to the experimental data collected in real cabinet under normal operating conditions. The simulation results show that the air temperature predicted by the model is closer to the temperature measured experimentally inside the cabinet particularly when the weather data files of the computational model have a similar behavior to the actual weather data. Numerical studies show that the use of mechanical ventilation is effective in the extraction of heat generated inside the cabinet.
- Thermal performance, usage behaviour and food waste of domestic refrigerators in a university student communityPublication . Galvão, Diogo Alexandre Sobreiro; Gaspar, Pedro Dinis; Silva, Pedro Dinho da; Pires, LuísFood safety and quality as well as storage conditions leading to food waste are related to the reduced thermal performance of domestic refrigerators, the mismanagement of food stored in it or the misuse of the equipment. This paper analyses the operative conditions of refrigerators in the student community of the University of Beira Interior (Covilhã, Portugal). A test sample of 51 appliances in the student households was instrumented with temperature dataloggers. Simultaneously, surveys on the use of refrigerator and food waste were applied to the students, ultimate users of the appliances. The students, with an average of 23 years old, mostly female (65.9%), live alone (6%), with their parents (24%), or with other students (71%). The test sample of appliances had, on average, a nominal electrical power of 126 W and an inner volume of 205 liters. It was found that the average storage temperature was 5.5ºC. The storage temperature in the appliances increased with the number of people who used it. This figure was largely due to improper use behaviour, in particular the number of times that the refrigerator door was open unnecessarily. The joint analysis of these data allows relating the use behaviour of with food waste. The comparison with similar studies conducted in the past shows that the average storage temperature in the current study is lower, mainly due to the technological evolution of appliances as well as the global awareness concerning food safety and food waste. The results of this work, apart from offering results about the performance of the operative conditions of refrigerators in a community not studied so far, highlights the need for further awareness of good practices to reduce food waste and simultaneously ensure food safety of the perishable food products stored in domestic refrigerators. These results could be extrapolated to the remaining people in order to develop strategies to improve cities sustainability.
- Parametric optimization of surface dielectric barrier discharge actuators for ice sensing applicationPublication . Abdollahzadehsangroudi, Mohammadmahdi; Rodrigues, Frederico; Nunes-Pereira, João; Páscoa, J. C.; Pires, LuísIn this paper a parametric optimization of the dielectric barrier discharge (DBD) plasma actuator is con ducted in order to achieve better ice sensing and deicing performance. For this purpose, different DBD plasma actuators were tested by changing the main geometrical dimension of the DBD plasma actuator and dielectric material. Both the ice sensing and thermal characteristics of the DBD plasma actuator were analyzed and compared. The results reveal that there exists two separate set of optimum parameters that lead to best ice sensing and thermal behavior. For both the sensing and thermal characteristics, the thinnest DBD showed the best performance. Kapton DBD plasma actuator showed the highest surface temperature while PMMA (poly methyl methacrylate) had the best performance for ice sensing. In the end, the deicing performance of a DBD actuator that had in average better thermal and ice sensing performance was tested for deicing an ice layer and a frost layer. The progress of the deicing process and the ice sensing measure on the surface were recorded and analyzed.