Heat transfer characteristics of impinging jet on a hot surface with constant heat flux using Cu2O–water nanofluid: An experimental study

2020 ◽  
Vol 112 ◽  
pp. 104509 ◽  
Author(s):  
Mohsen Amjadian ◽  
Habibollah Safarzadeh ◽  
Mehdi Bahiraei ◽  
Saeed Nazari ◽  
Behrang Jaberi
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Flux ◽  
Impinging Jet ◽  
Constant Heat Flux ◽  
Heat Transfer Characteristics ◽  
Constant Heat ◽  
Transfer Characteristics ◽  
Hot Surface

Heat Transfer Characteristics of Gaseous Flows in Micro-Channels With Negative Heat Flux

2006 ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Constant Heat Flux ◽  
Channel Height ◽  
Gas Temperature ◽  
Heat Transfer Characteristics ◽  
Constant Heat ◽  
Transfer Characteristics ◽  
Micro Channels ◽  
Gaseous Flows

Two-dimensional compressible momentum and energy equations are solved to obtain the heat transfer characteristics of gaseous flows in micro-channels with CHF (constant heat flux) whose value is negative. The combined effect of viscous dissipation and compressibility is also investigated. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The computations are performed for channels with constant heat flux with range from −104 to −102 Wm−2. The channel height ranges from 10 to 100 μm and the aspect ratio of the channel height and length is 200. The stagnation pressure varies from 120 to 500 kPa. The outlet pressure is fixed at the atmosphere. The wall and bulk temperatures in micro-channels are compared with those of the case of positive heat flux and also compared with those of the incompressible flow in a conventional sized channel. In the case of negative heat flux, temperature profiles normalized by heat flux have different trends in the case of positive heat flux, when flow is fast. A gas temperature falls down due to the energy conversion. A correlation for the prediction of the wall temperature of the gaseous flow in the micro-channel is proposed.

Heat Transfer Characteristics of CuO-Base Oil Nanofluid Laminar Flow Inside Flattened Tubes Under Constant Heat Flux

2010 ◽  
Author(s):  
P. Razi ◽  
M. A. Akhavan-Behabadi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Constant Heat Flux ◽  
Electrical Heating ◽  
Heat Transfer Characteristics ◽  
Constant Heat ◽  
Base Oil ◽  
Transfer Characteristics

An experimental investigation has been carried out to study the heat transfer characteristics of CuO-Base oil nanofluid flow inside horizontal flattened tubes under constant heat flux. The nanofluid flowing inside the tube is heated by an electrical heating coil wrapped around it. The convective heat transfer coefficients of nanofluids are obtained for laminar fully developed flow inside round and flattened tubes. The effect of different parameters such as Reynolds number, flattened tube internal height, nanoparticles concentration and heat flux on heat transfer coefficient is studied. Observations show that the heat transfer performance is improved as the tube profile is flattened. The heat transfer coefficient is increased by using nanofluid instead of base fluid. Also, it can be concluded that decreasing the internal height of the flattened tubes and increasing the concentration of nanoparticles both contribute to the enhancement of heat transfer coefficient.

Heat Transfer Characteristics of Gaseous Slip Flow in Concentric Micro Annular Tubes

2009 ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Koichi Suzuki
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Incompressible Flow ◽  
Slip Flow ◽  
Outer Wall ◽  
Constant Heat Flux ◽  
Heat Transfer Characteristics ◽  
Constant Heat ◽  
Transfer Characteristics ◽  
Adiabatic Case

A concentric micro annular passage is a basic and important micro-geometry of micro-fluidic-systems from simple heat exchanger to the most complicated nuclear reactors. Therefore, heat transfer characteristics of gaseous flows in concentric micro annular tubes with constant heat flux whose value was positive or negative were numerically investigated. The slip velocity, temperature jump and shear stress work were considered on the slip boundary. The numerical methodology was based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The computations were performed for two thermal cases. This is, the heat flux was constant at the inner wall and outer wall was adiabatic (Case 1) and the heat flux was constant at the outer wall and the inner wall was adiabatic (Case 2). Each constant heat flux of 104 Wm−2 for the positive value and −104 Wm−2 for the negative value was chosen. The outer tube radius ranged from 20 to 150 μm with the radius ratio 0.02, 0.05, 0.1, 0.25 and 0.5 and the ratio of length to hydraulic diameter was 100. The stagnation pressure was chosen in such a way that the exit Mach number ranges from 0.1 to 0.7. The outlet pressure was fixed at the atmospheric pressure. The heat transfer characteristics in concentric micro annular tubes were obtained. The wall and bulk temperatures with positive heat flux are compared with those of negative heat flux cases and also compared with those of the simultaneously developing incompressible flow. The results show that the compressible slip flow Nusselt number is different from that of incompressible flow. And, the temperatures normalized by heat flux have different trends whether heat flux value is positive or negative. A correlation for the prediction of the heat transfer characteristics of gas slip flow in concentric micro annular tubes is proposed.

scholarly journals Experimental Research on Heat Transfer Characteristics of CuO Nanofluid in Adiabatic Condition

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Yu Guangbin ◽  
Gao Dejun ◽  
Chen Juhui ◽  
Dai Bing ◽  
Liu Di ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mass Fraction ◽  
Constant Heat Flux ◽  
Average Particle ◽  
Heat Transfer Characteristics ◽  
Flow Loop ◽  
Constant Heat ◽  
Transfer Characteristics ◽  
Experimental Apparatus

The laminar convective heat transfer behavior of CuO nanoparticle dispersions in glycol with the average particle sizes (about 70 nm) was investigated experimentally in a flow loop with constant heat flux. To enhance heat exchange under high temperature condition and get the more accurate data, we try to improve the traditional experimental apparatus which is used to test nanofluid heat transfer characteristics. In the experiment five different nanoparticle concentrations (0.25%, 0.50%, 0.80%, 1.20%, and 1.50%) were investigated in a flow loop with constant heat flux. The experimental results show that the heat transfer coefficient of nanofluid becomes higher than that of pure fluid at the same Reynolds number and increased with the increasing of the mass fraction of CuO nanoparticles. Results also indicate that at very low volume concentrations nanofluid has no major impact on heat transfer parameters and the pressure of nanofluids increased by the mass fraction increase.

Heat Transfer Characteristics of Gaseous Slip Flow in Concentric Micro-Annular Tubes

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Koichi Suzuki
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Incompressible Flow ◽  
Slip Flow ◽  
Outer Wall ◽  
Constant Heat Flux ◽  
Heat Transfer Characteristics ◽  
Constant Heat ◽  
Transfer Characteristics ◽  
Adiabatic Case

A concentric micro-annular passage is a basic and important microgeometry of microfluidic-systems from simple heat exchanger to the most complicated nuclear reactors. Therefore, heat transfer characteristics of gaseous flows in concentric micro-annular tubes with constant heat flux whose value was positive or negative were numerically investigated. The slip velocity, temperature jump, and shear stress work were considered on the slip boundary conditions. The numerical methodology was based on the arbitrary-Lagrangian–Eulerian method. The computations were performed for two thermal cases. That is, the heat flux that was constant at the inner wall and outer wall was adiabatic (case 1) and the heat flux that was constant at the outer wall and the inner wall was adiabatic (case 2). Each constant heat flux of 104 Wm−2 for the positive value and −104 Wm−2 for the negative value was chosen. The outer tube radius ranged from 20 μm to 150 μm with the radius ratios of 0.02, 0.05, 0.1, 0.25, and 0.5 and the ratio of length to hydraulic diameter was 100. The stagnation pressure was chosen in such a way that the exit Mach number ranges from 0.1 to 0.8. The outlet pressure was fixed at the atmospheric pressure. The heat transfer characteristics in concentric micro-annular tubes were obtained. The wall and bulk temperatures with positive heat flux are compared with those of negative heat flux cases and also compared with those of the simultaneously developing incompressible flow. The results show that the Nusselt number of compressible slip flow is different from that of incompressible flow. However, the temperatures normalized by heat flux have different trends whether heat flux value is positive or negative. A correlation for the prediction of the heat transfer characteristics of gas slip flow in concentric micro annular tubes is proposed.

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