The importance of heat transfer by natural convection in enclosures can be found in many engineering applications, such as energy transfer in buildings, solar collectors, nuclear reactors and electronic packaging. An experimental study was conducted to investigate heat transfer by natural convection in a rectangular fin plate with circular perforations as heat sinks. The patterns of the perforations included 24 circular perforations (holes) for the first fin; the number of perforations increased by eight for each fin to 56 in the fifth fin. These perforations were distributed in 6-14 rows and four columns. Experiments were carried out in an experimental facility that was specifically designed and constructed for this purpose. It was observed that the temperature along the non-perforated fin dropped from 30 to 25°C, but the temperature drop for the perforated fins was from 30 to 23.7°C at low power (6 W). The drop in temperature between the fin base and the tip increased as the diameter of the perforations increased. The temperature drop at the highest power (220 W) was from 250 to 49°C for the nonperforated fin and from 250 to 36°C for the perforated fins. The heat transfer rate and the coefficient of heat transfer increased with an increased number of perforations.

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In this numerical investigation, three‐dimensional analysis has been used to study the effect of finned channels configuration of (circular, square, and triangular shape) and fin spacing with four rows in staggered arrangements. The finite volume method with k‐ ω turbulent model is applied to estimate the heat transfer and flow characteristics. The results illustrate that the development of the boundary layer between the fins surfaces is credited to the finned channels configuration, fin spacing, and Reynolds number. Moreover, the results of pressure drop and heat transfer with various channel configuration and different fin spacings (1.6, 2, and 4 mm) are presented and validated with the available correlations. The triangular‐finned channel with 1.6 mm fin spacing offered higher heat transfer enhancement followed by square‐ and circular‐finned channels. A considerable agreement was observed when the current findings and the existing correlations were compared, with a maximum deviation of 15% for all the cases.

A recent study of the design of solar distillation with solar radiation concentration was carried out by an independent device. Transformer oil was used as a fluid to transfer heat to the distilled basin. The design and operational variables are essential, such as distiller dimensions, concentration ratio, pressure, and temperature. A mathematical model was proposed to simulate the system for 2 July 2018 from 10 AM to 4 PM in the climatic conditions of the city of Kirkuk, Iraq. Fuzzy logic (FL) was used to select the affected parameters: water temperature (T w ), water pressure (P w ), glass temperature (T g ), and vapor pressure (P g ) which have a separated membership function that control the linguistic variables. The results showed that the best performance of the distiller is at T w = 100°C, P g = 10 000 Pa, T g = 20°C, and P w = 20 000 Pa, and concentration ratio of 30. This study used FL to analyze solar distiller performance and identify optimum temperature, pressure, and concentration ratio on the productivity of solar distiller. K E Y W O R D Sconcentric solar collector, fuzzy logic control, solar distiller

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