Feedstuffs supplementation in deteriorated rangelands : effects on performance of small ruminants in arid and semi-arid regions

Meeting: Small Ruminants Research and Development in the Near East, 2-4 Nov. 1988, Cairo, EGIn IDL-298

Experimental Investigation of the Effect of Extended Surfaces on the Performance of Tube Banks in Cross Flow

Experimental results of the heat transfer and pressure drop of an air flow across different configurations of extended surfaces of in-line and staggered tube bank arrangements are reported.Empirical equations relating the heat transfer, pressure drop and flow velocity are obtained. Results indicate that extended surfaces may enhance the heat transfer, but at the same time, they will increase the pressure drop.It is concluded that for Reynolds number (Re) ≤ 6 × 103, the simple basic configuration of a circular cylinder in the in-line arrangement is recommended since it has the highest ratio of heat transfer to pressure drop (Nu/ΔP*). For Re > 6 × 103, the configuration with the extended surface in the downstream end (straight fin) of a staggered arrangement is recommended

Understanding the effects of sand and dust accumulation on photovoltaic modules

Numerical and analytical models of sand and dust particle accumulation on photovoltaic modules in dry regions are presented and supported by a laboratory investigation of sand particle accumulation on a glass surface. Both models and the experimental data indicate that the reduction in the free fractional area can be described by an exponential decay resulting from the formation of clusters of particles. Such clusters can support particles in upper layers which reduce the available area for photon capture by a much smaller amount than particles resting directly on the glass surface. The results qualitatively describe existing field data beyond the linear regime and are developed to account for field conditions, including analysis of photovoltaic module tilt, humidity and wind speed. This investigation is intended as a basis of an engineering design tool to assess the case for including photovoltaics in dry regions