Experimental study on CuO nanoparticles in distilled water and its effect on heat transfer on a vertical surface

2011 ◽  
Vol 25 (11) ◽  
pp. 2927-2934 ◽  
Author(s):  
Ramakrishna N. Hegde ◽  
Srikanth S. Rao ◽  
R. P. Reddy
2012 ◽  
Vol 5 (1) ◽  
pp. 16
Author(s):  
Ramakrishna N. Hegde ◽  
Srikantha S. Rao ◽  
Ranapratap P. Reddy

2015 ◽  
Vol 23 (03) ◽  
pp. 1550024 ◽  
Author(s):  
Omidreza Ghaffari ◽  
Muhammad Ikhlaq ◽  
Mehmet Arik

According to recent trends in the field of miniature electronics, the need for compact cooling solutions compatible with very thin profiles and small footprint areas is inevitable. Impinging synthetic jets are recognized as a promising technique for cooling miniature surfaces like laptops, tablets, smart phones and slim TV systems. Effect of jet to cooled surface spacing is crucial in cooling performance as well as predicting Nusselt number for such spacing. An experimental study has been performed to investigate the cooling performance of two different synthetic jets actuated with piezoelectric actuators cooling over a vertical surface. Results showed that a major degradation of heat transfer when jets are close to the surface is occurred. Slot synthetic jets showed a better performance in terms of coefficient of performance (COP) than semi-confined circular jets for small jet to surface spacing. Later, a correlation is proposed for predicting Nu number for a semi-confined circular synthetic jet accounting the effects of Re number ([Formula: see text]), jet-to-surface spacing ([Formula: see text] and [Formula: see text]) and the stroke length ([Formula: see text] and [Formula: see text]). It is found that correlation can provide predictions with an [Formula: see text] value of over 98%.


Author(s):  
Tao Wang ◽  
Xuegong Hu ◽  
Dawei Tang

To solve the questions of the middle heat exchanger of space-based laser cooling system such as large heat transfer area and operating mode instability, a MC-MG (Microchannel-Microgroove) microscale heat exchanger is proposed and experimental study is carried out. The experimental results indicate that as the Reynolds number increases, the Nusselt number originally increases and then keeps constant. While adding the volumetric flow rate of distilled water in the microchannels, the total thermal resistance is first reduced and then becomes steady. With increasing the volumetric flow rate of distilled water, the total quantity of heat transfer increases first, then decreases and finally tends to be constant. The average heat transfer coefficient of the heat exchanger reaches to 1.6 × 104W/ (m2-K) and total thermal resistance is less than 0.21K/W. Therefore the solution to cooling laser with the heat exchanger is preferable.


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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