Numerical and experimental studies on laminar hydrodynamic and thermal characteristics in fractal-like microchannel networks. Part B: Investigations on the performances of pressure drop and heat transfer

2013 ◽  
Vol 66 ◽  
pp. 939-947 ◽  
Author(s):  
Chun-ping Zhang ◽  
Yi-fu Lian ◽  
Xiang-fei Yu ◽  
Wei Liu ◽  
Jyh-tong Teng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Experimental Studies ◽  
Thermal Characteristics

Microtomography-Based Analysis of Pressure Drop and Heat Transfer Through Open Cell Metal Foams

2013 ◽  
Author(s):  
M. Oliviero ◽  
S. Cunsolo ◽  
W. M. Harris ◽  
M. Iasiello ◽  
W. K. S. Chiu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Metal Foam ◽  
High Surface ◽  
Thermal Characteristics ◽  
Industrial Applications ◽  
Metal Foams ◽  
Surface Evolver ◽  
Periodic Cell ◽  
Numerical Predictions

Their light weight, open porosity, high surface area per unit volume and thermal characteristics make metal foams a promising material for many industrial applications involving fluid flow and heat transfer. Pressure drop and heat transfer of porous media have inspired a number of experimental and numerical studies. Many models have been proposed in the literature that correlate the pressure gradient and the heat transfer coefficient with the mean cell size and porosity. However, large differences exist among results predicted by different models. Most studies are based on idealized periodic cell structures. In this study, the true 3-D micro-structure of the metal foam is obtained by employing x-ray computed microtomography (XCT). For comparison, ideal Kelvin foam structures are developed in the free-to-use software “Surface Evolver” surface energy minimization program. Pressure drop and heat transfer are then investigated using the CFD Module of COMSOL® Multiphysics code. A comparison between the numerical predictions from the real and ideal geometries is carried out.

scholarly journals Experimental Studies on a Solar Air Heater Having V-Corrugated Absorber Plate with Obstacles Bent Vertically

2014 ◽  
Vol 493 ◽  
pp. 86-92 ◽  
Author(s):  
Ekadewi A. Handoyo ◽  
Djatmiko Ichsani ◽  
Prabowo ◽  
S. Sutardi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flat Plate ◽  
Air Temperature ◽  
Temperature Rise ◽  
Experimental Studies ◽  
Bottom Plate ◽  
Solar Air Heater ◽  
Absorber Plate ◽  
Air Heater

A solar air heater (SAH) is a simple heater using solar radiation that is useful for drying or space heating. Unfortunately, heat transfer from the absorber plate to the air inside the solar air heater is low. Some researchers reported that obstacles are able to improve the heat transfer in a flat plate solar air collector and others found that a v-corrugated absorber plate gives better heat transfer than a flat plate. Yet, no work of combining these two findings is found.This paper describes the result of experimental study on a SAH with v-corrugated absorber plate and obstacles bent vertically started from 80oto 0owith interval 10oon its bottom plate. Experiments were conducted indoor at five different Reynolds numbers (1447 Re 7237) and three different radiation intensities (430, 573, and 716 W/m2).It is found that the obstacles improve SAH performance. Both the air temperature rise and efficiency increase with inserting obstacles bent at any angle vertically. Unfortunately, the air pressure drop is increasing, too. Obstacles bent vertically at smaller angle (means more straight) give higher air temperature rise and efficiency. However, the optimum angle is found 30o. The air temperature rise and efficiency will be 5.3% lower when the obstacles bent 30oinstead of 0o, but the pressure drop will be 17.2% lower.

Flow Structure and Enhanced Heat Transfer in Channel Flow With Dimpled Surfaces: Application to Heat Sinks in Microelectronic Cooling

2006 ◽  
Vol 129 (2) ◽  
pp. 157-166 ◽  
Author(s):  
Carlos Silva ◽  
Egidio Marotta ◽  
Leroy Fletcher
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Structure ◽  
Channel Flow ◽  
Experimental Studies ◽  
Heat Sinks ◽  
Flat Plates ◽  
Design Factor ◽  
Friction Factors ◽  
Modeling And Experiments

The use of dimple technology for improvement in friction factors and enhancement of heat transfer has been attracting the attention of many scientists and engineers. Numerical and experimental studies have shown there is a positive improvement (two-fold on average) in Nusselt number when dimpled surfaces are compared to flat plates, and this improvement is achieved with pressure drop penalties that are small when compared to other more intrusive types of turbulence promoters. When arrays of specific dimple geometry are used, pressure drop penalties are roughly equivalent to the heat transfer improvement. This, at least theoretically, will enable the design of smaller heat transfer devices such as heat sinks, which are especially appealing in those applications where size is an important design factor. A literature review of numerical modeling and experiments on flow over dimpled surfaces was performed, and key parameters and flow structure were identified and summarized. With these premises, a numerical model was developed. The model was validated with published experimental data from selected papers and fine tuned for channel flow within the laminar flow regime. Subsequently, the model was employed for a specific application to heat sinks for microelectronic cooling. This paper, then, provides a comparative evaluation of dimple technology for improving heat transfer in microelectronic systems.

Research on the Flow Boiling and Heat Transfer of Ethanol in a Corrugated Mini-Channel

2011 ◽  
Vol 66-68 ◽  
pp. 876-881
Author(s):  
Wei Chang ◽  
Shu Sheng Zhang ◽  
Shuai Tian ◽  
Meng Jia Huo
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Phase Interface ◽  
Experimental Studies ◽  
Heating Wall ◽  
Heat And Mass Exchange ◽  
System Pressure

Based on the establishment of a two-dimensional model, a numerical simulation was conducted in this paper to study the flow boiling and heat transfer characteristics of ethanol in a corrugated mini-channel. User defined functions were employed to describe the key processes of heat and mass exchange at the phase interface. Bubble growth profile was monitored over time and its influence on system pressure drop and heat transfer coefficient was also analyzed. The simulation result shows that the nucleation sites tend to distribute near the internal peaks of the heating wall due to the enhanced local turbulence. The system pressure drop increases over the heating time and fluctuates within a certain range. The heat transfer coefficient decreases with increasing quality, and this trend is consistent with the result of similar experimental studies.

Progress in Gas-Side Fouling of Heat-Transfer Surfaces

1990 ◽  
Vol 43 (3) ◽  
pp. 35-66 ◽  
Author(s):  
W. J. Marner
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Experimental Studies ◽  
Heat Transfer Surface ◽  
Experimental Results ◽  
Considerable Progress ◽  
Insulating Layer ◽  
The Past ◽  
Measuring Devices ◽  
Recent Developments

The purpose of this paper is to present a review of recent developments in gas-side fouling, which may be defined as the deposition of an insulating layer of material onto a heat-transfer surface in the presence of a dirty gas stream. Four major topics are covered in the review: (a) Recent reviews involving various aspects of gas-side fouling, (b) Gas-side fouling mechanisms with special emphasis on transport to the surface, (c) Analytical studies including deposition, heat transfer, and pressure drop models, and (d) Experimental studies including gas-side fouling measuring devices and experimental results. Although the review focuses on work carried out during the past 10–15 years, a number of earlier contributions to the gas-side fouling literature are also included. Gas-side fouling is an extremely complex, multifaceted phenomenon and although considerable progress in this area has been made through the years, it is clear that much work remains to be done.

scholarly journals Study of heat transfer and pressure drop characteristics of air heat exchanger using PCM for free cooling applications

2016 ◽  
Vol 20 (5) ◽  
pp. 1543-1554 ◽  
Author(s):  
Sivakumar Kalaiselvam ◽  
Kanchipuram Sureshkumar ◽  
Vijeykishoor Sriram
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Phase Change Materials ◽  
Thermal Characteristics ◽  
Ambient Air ◽  
Dynamics Modeling ◽  
Tube Heat Exchanger ◽  
High Heat Transfer ◽  
Free Cooling

Free cooling is the process of storing the cool energy available in the night ambient air and using it during the day. The heat exchanger used in this work is a modular type which is similar to the shell and tube heat exchanger. The shell side is filled with Phase Change Materials (PCM) and air flow is through the tubes in the module. The modules of the heat exchanger are arranged one over other with air spacers in between each module. The air space provided in between the module in-creases the retention time of the air for better heat transfer. Transient Computational Fluid Dynamics modeling is carried out for single air passage in a modular heat exchanger. It shows that the PCM phase transition time in the module in which different shape of fins is adopted. The module with rectangular fins has 17.2 % reduction in solidification compared with the plain module. Then steady state numerical analysis is accomplished to the whole module having the fin of high heat transfer, so that pressure drop, flow and thermal characteristics across the module and the air spacers are deter-mined for various air inlet velocities of 0.4 to 1.6 m/s. To validate the computational results, experiments are carried out and the agreement was found to be good.

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