Ali Najah Al-Shamani

Theoretical study of new combined absorption-ejector refrigeration system

An improved system of the new combined single stage absorption cycle operated with NH3/H2O as working fluid was performed. In order to enhance performance the cycle a new configuration of absorption system was utilized. The performances of two configurations of the combined absorption cycle were compared; a) with common solution heat exchanger and b) divided the streamline of solution heat exchanger to recover the internal heat. Based on the analysis, it has been shown that the second configuration a significant reduction of the required generator and absorber loads by about 20% and 17% respectively, with increased coefficient of performance (COP) about 12% compared to the first configuration. This improvement in the overall COP is found due to improve energy utilization efficiency significantly.

Thermodynamic analysis of new concepts for enhancing cooling of PV panels for grid-connected PV systems

The temperature rise in photovoltaic cells causing drop in their open-circuit voltage is a serious issue to be dealt with. A wide range of cooling techniques have been proposed by researchers due to its positive results on electrical efficiency during operation. One of the prominent techniques in the field is using a hybrid photovoltaic thermal (PV/T) design which in turns utilizes a working fluid to extract the heat from the collector. Various PV/T designs have been proposed, most prominently nanofluid and nanofluid with nano-PCM-based PV/T. This paper aims to evaluate the two techniques of cooling a grid-connected PV system and examines the systems electrical and combined efficiency, in addition to performing exergy analysis. The two systems are experimentally tested for outdoors conditions in Bangi, Malaysia. The results show the two systems achieving highest electrical exergies of 73 and 74.52 for nanofluid and nanofluid with nano-PCM, respectively. Both systems achieved higher exergies than water-cooled and conventional GCPV.

Study of heat transfer due to turbulent flow of nanofluids through rib-groove channel

Nanofluids for improve characteristics flow in a rib-groove channel are investigate. The continuity, momentum and energy equations were solved by FLUENT program. The bottom wall of channel is heated while the upper wall is symmetry, the left side velocity inlet, and the right side is outlet (pressure out). Four different rib-groove shapes are used. Four different types of nanoparticles, Al2O3, CuO, SiO2, and ZnO with different volumes fractions in the range of 1% to 4% and different nanoparticle diameter in the range of 25 nm to 70 nm, are dispersed in the base fluid water are used. In this paper, several parameters such as different Reynolds numbers in the range of 10000 < Re < 40000 are investigated. The numerical results indicate that the trapezoidal with increasing height in the flow direction rib- trapezoidal groove has the best heat transfer and high Nusselt number; the nanofluids with SiO2 have the best behavior. The Nusselt number increases as the volume fraction increases and it decreases as the nanoparticle diameter increases.