Effects of surfactants on thermal performance and pressure drop in mini-channels- An experimental study

Author(s):  
Saber Mohammadi ◽  
Faramarz Hormozi ◽  
Elham Hosseini Rad
2014 ◽  
Vol 18 (4) ◽  
pp. 1315-1326 ◽  
Author(s):  
Ahmad Sajadi ◽  
Seyed Sadati ◽  
Masoud Nourimotlagh ◽  
Omid Pakbaz ◽  
Dariush Ashtiani ◽  
...  

In this experimental study heat transfer and pressure drop behavior of ZnO/water nanofluid flow inside a circular tube with constant wall temperature condition is investigated where the volume fractions of nanoparticles in the base fluid are 1% and 2%. The experiments? Reynolds numbers ranged roughly from 5000 to 30000. The experimental measurements have been carried out in the fully-developed turbulent regime. The results indicated that heat transfer coefficient increases by 11% and 18% with increasing volume fractions of nanoparticles respectively to 1% and 2% vol. The measurements also showed that the pressure drop of nanofluids were respectively 45% and145% higher than that of the base fluid for volume fractions of 1% and 2% of nanoparticles. However experimental results revealed that overall thermal performance of nanofluid is higher than that of pure water by up to 16% for 2% vol. nanofluid. Also experimental results proved that existing correlations can accurately estimate nanofluids convective heat transfer coefficient and friction factor in turbulent regime, provided that thermal conductivity, heat capacity, and viscosity of the nanofluids are used in calculating the Reynolds, Prandtl, and Nusselt numbers.


Author(s):  
Arun K. Karunanithi ◽  
Fatemeh Hassanipour

Previous studies have shown that stacked multi-layer mini-channels heat sinks with square or circular channels have advantages over traditional single layered channels in terms of both pressure drop and thermal resistance. In this work, porous media is used in the multi-layered stacked mini-channels instead of square or rectangular channels and the effect of the same on pressure drop and thermal performance is studied. Porosity scaling is done between the layers of porous media and is compared with unscaled stacked multilayer channel. Porosity scaling allows the porosity to vary from one layer to the next layer and could result in a lower pressure drop and better thermal performance.


2020 ◽  
Vol 92 (3) ◽  
pp. 30901
Author(s):  
Suvanjan Bhattacharyya ◽  
Debraj Sarkar ◽  
Ulavathi Shettar Mahabaleshwar ◽  
Manoj K. Soni ◽  
M. Mohanraj

The current study experimentally investigates the heat transfer augmentation on the novel axial corrugated heat exchanger tube in which the spring tape is introduced. Air (Pr = 0.707) is used as a working fluid. In order to augment the thermohydraulic performance, a corrugated tube with inserts is offered. The experimental study is further extended by varying the important parameters like spring ratio (y = 1.5, 2.0, 2.5) and Reynolds number (Re = 10 000–52 000). The angular pitch between the two neighboring corrugations and the angle of the corrugation is kept constant through the experiments at β = 1200 and α = 600 respectively, while two different corrugations heights (h) are analyzed. While increasing the corrugation height and decreasing the spring ratio, the impact of the swirling effect improves the thermal performance of the system. The maximum thermal performance is obtained when the corrugation height is h = 0.2 and spring ratio y = 1.5. Eventually, correlations for predicting friction factor (f) and Nusselt number (Nu) are developed.


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