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Go to Editorial ManagerRecently, major part of convection heat transfer researches focus on increasing fins efficiency by increasing thermal performance for the same fin volume. Metal foam is a promising way to achieve this aim. Performance analysis has been carried out to investigate the heat transfer characteristics of copper fin foam samples. The samples have been compared with the solid metal fin heat transfer. A forced convection heat transfer had been applied to a four specimens. An electrical heater heats up the fins, which are subjected to a stream of the ambient air driven by a blower fan as heat dissipated. The heat flux had been fixed along the tests with three different air velocity used; the forced heat convection had been simulated. The pores density of copper fin foam is varied in the range of 10, 20 & 40 pores per inches (PPI). Thermal performance of copper fin foam has been evaluated in terms of average Nusselt number and thermal resistance of heat sinks. The increasing in the heat transfer rate and average Nusselt number when used metal foam has been found in the range of 36-133 % compare to solid copper. Furthermore, it has been proven that this increment reaches the maximum value for a given PPI even when raise the air velocity.
Cooling greenhouses is essential to provide a suitable environment for plant growth in arid regions. However, using conventional cooling methods are facing many challenges. Filtering out near infra-red radiation (NIR) at the greenhouse cover can significantly reduce the heating load and can solve the overheating problem of the greenhouse air temperature. Four cases of shadings were examined for their ability to improve the indoor condition of a greenhouse cooled by indirect direct evaporative cooler: (shade 1) a single layer of polyethylene film, (shade 2) a double layer of polyethylene film, (shade 3) a double layer of polyethylene film with a green mesh layer (shade 4) a double layer of polyethylene film with a Utrecht Corrugated Cardboard with 3cm holes distributed for incident sun light. An experimental study is conducted to determine the performance parameters of indirect direct evaporative cooling of greenhouse in Baghdad (33.3 oN, 44.4oE) for the four types of shadings. It was found that the percentage reduction in light intensities for shade 1, shade 2 and shade 3 are 15%, 25% and 40% respectively. It percentage reduction solar intensity due to shades is increases at the beginning and ending of sunny period, while it was minimum at noon. The percentage reduction in temperature due to indirect direct evaporative cooling for the shade1, shade 2 and shade 3 and shade 4 are 32.4, 36.3, 42.4, and 47 respectively. The percentage increasing in relative humidity due to indirect direct evaporative cooling for the shade1, shade 2 and shade 3 and shade 4 are 562.5, 729, 871, and 788 respectively. The percentage increasing in temperature due heating load of greenhouse for the shade1, shade 2 and shade 3 and shade 4 are 41.4, 33.2, 20.5, and 11 respectively. The percentage decrease in relative humidity due heating load of greenhouse for the shade1, shade 2 and shade 3 and shade 4 are 43.4, 31, 11.8, and 7 respectively.