Experimental and numerical investigations have been performed to study the natural convection heat transfer from a longitudinal fin arrays at different orientation angles. For such purpose, an experimental test rig was manufactured to be used for these investigations. It basically consists of base plate, an array of parallel longitudinal fins, heating unit and layers of thermal insulation. During the experiments, the fin spacing (S) was varied from 3.375 to 33 mm, while the fin height (H) from 15 to 60 mm. The orientation angle (Ф) was changed from 0° to 180°, and temperature difference between fin and surrounding (∆T) from 35 to 95 °C. To understand the general flow patterns dominating flows from the heat sink, the three-dimensionless elliptic governing equations were solved using finite volume computational fluid dynamics (CFD) code. A comparative study between the experimental and numerical results was performed to verify the numerical code. It was found for the configuration tested that the heat transfer rate per unit base area increases with the increase in the fin spacing and reaches a maximum value then decreases with farther increase in the fin spacing. The maximum heat dissipation occurs at optimal spacing 5. 6 S opt = mm. Moreover, the average heat transfer coefficient was found to have a maximum value at Ф = 0° and decreased with the increase of (Ф) to reach a minimum value at Ф = 90°. Empirical correlations between Nussult number, Rayleigh number, fin spacing, fin height, orientation angle, temperature difference between the fin and surroundings were derived.

In this paper a low complexity MIMO MC-CDMA receiver is proposed. We investigate the receiver performance and complexity in the case of despreading multicarrier code division multiple access signals (MC-CDMA) prior to V-BLAST detection in multiple input multiple output systems (MIMO). The proposed structure shows that for iterative detection, despreading before detection (DBD) reduces the effect of multiple access interference (MAI), and the reported results demonstrate improved bit error rate (BER) performance and user capacity of the system over despreading after detection (DAD). Furthermore, DBD results in reduced system complexity. The performance of both detectors is evaluated using computer simulations for a frequency selective slow Rayleigh fading channel.

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