الفهرس 
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Abstract
This study is concerned with the experimental investigation on heat transfer enhancement of an impinging free liquid jet on a hot surface copper plate with different shapes, by replacing the base fluid, distilled water with Al2O3– distilled water nanofluid.
Different shapes of hot surface of copper plate (Flat, Waved, Corrugated, Convex and Concave), different impingement Reynolds numbers 〖Re〗_iranging from (7,565 to nearly 18,460), five nanoparticles concentrations (0%, 0.2%,0.5%,1% and 2%, respectively) were studied using distilled water and AL2O3nanofluid jet impingement.
The experimental test rig consists of three parts fluid cycle, heating system and data acquisition system.
In order to create a hot surface, heated copper plates with different surface shapes (flat, corrugated, waved, convex and concave) were designed.
The two-step method was used for preparation of nanofluid AL2O3 (10nm). Initially, the AL2O3 nanoparticles was mixed in the distilled water then submitted to sonication treatment for 30 minutes to disperse all the materials and to break the agglomerates.
The distilled water or AL2O3nanofluidflows from a three litre cylindrical container using a pump. The flow rate is controlledand measured by a valve and a flow meter.The water or nanofluid jet emerges from thenozzle and impinges on a horizontal hot circular copper plate. The falling liquid is collected in a fluid sump.
The experimental results indicated that impingement Reynolds number plays a major role in the heat transfer process.As the increase of 〖Re〗_i from 7747 to 18460 results in 36.8 % enhancement in Nusselt number in case of water jet on flat plate.
It is also found that using nanofluid jet enhances the heat transfer, the experimental data showed an increase in Nusselt number that can reach up to 32.2% at 2% concentration in case of corrugated surface. This result indicated that using nanofluid as a heat transfer enhancer and can enhance the heat transfer process.
The experimental data showed that the shape of hot surface can enhance heat transfer process as Nusselt number increased up to 58.7% using water jet and 57.1% in case of nanofluid jet due to hot surface shape difference with the best enhancement in corrugated surface at the same impingement Reynolds number.
Finally, it was noted that surface shape, impingement Reynolds number and nanofluid concentration can significantly affect the heat transfer enhancement process.The accumulative effect of using nanafluid jet 2% with corrugated surface with higher flow rate on Nusselt number can reach 185%. On the other hand, using a dispersant for the nanofluid as polyethylene glycol keeps the nanofluid suspension and prevents agglomeration, but reduces its heat transfer enhancement effect by 2.5%.
Keywords: Nanofluid, Heat Transfer, Surface Shapes, Impingement Jet.
This study is concerned with the experimental investigation on heat transfer enhancement of an impinging free liquid jet on a hot surface copper plate with different shapes, by replacing the base fluid, distilled water with Al2O3– distilled water nanofluid.
Different shapes of hot surface of copper plate (Flat, Waved, Corrugated, Convex and Concave), different impingement Reynolds numbers 〖Re〗_iranging from (7,565 to nearly 18,460), five nanoparticles concentrations (0%, 0.2%,0.5%,1% and 2%, respectively) were studied using distilled water and AL2O3nanofluid jet impingement.
The experimental test rig consists of three parts fluid cycle, heating system and data acquisition system.
In order to create a hot surface, heated copper plates with different surface shapes (flat, corrugated, waved, convex and concave) were designed.
The two-step method was used for preparation of nanofluid AL2O3 (10nm). Initially, the AL2O3 nanoparticles was mixed in the distilled water then submitted to sonication treatment for 30 minutes to disperse all the materials and to break the agglomerates.
The distilled water or AL2O3nanofluidflows from a three litre cylindrical container using a pump. The flow rate is controlledand measured by a valve and a flow meter.The water or nanofluid jet emerges from thenozzle and impinges on a horizontal hot circular copper plate. The falling liquid is collected in a fluid sump.
The experimental results indicated that impingement Reynolds number plays a major role in the heat transfer process.As the increase of 〖Re〗_i from 7747 to 18460 results in 36.8 % enhancement in Nusselt number in case of water jet on flat plate.
It is also found that using nanofluid jet enhances the heat transfer, the experimental data showed an increase in Nusselt number that can reach up to 32.2% at 2% concentration in case of corrugated surface. This result indicated that using nanofluid as a heat transfer enhancer and can enhance the heat transfer process.
The experimental data showed that the shape of hot surface can enhance heat transfer process as Nusselt number increased up to 58.7% using water jet and 57.1% in case of nanofluid jet due to hot surface shape difference with the best enhancement in corrugated surface at the same impingement Reynolds number.
Finally, it was noted that surface shape, impingement Reynolds number and nanofluid concentration can significantly affect the heat transfer enhancement process.The accumulative effect of using nanafluid jet 2% with corrugated surface with higher flow rate on Nusselt number can reach 185%. On the other hand, using a dispersant for the nanofluid as polyethylene glycol keeps the nanofluid suspension and prevents agglomeration, but reduces its heat transfer enhancement effect by 2.5%.
Keywords: Nanofluid, Heat Transfer, Surface Shapes, Impingement Jet.