scholarly journals Single-phase media hydrodynamics and heat transfer in heat exchangers with twisted profile tubes

2014 ◽  
Author(s):  
Yu. M. Brodov ◽  
K. E. Aronson ◽  
A. Yu. Ryabchikov ◽  
M. A. Nirenstein
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Single Phase

Numerical Investigation of Heat Transfer Characteristics of Different Nanoparticles Using Modified Eulerian-Eulerian Model

2020 ◽  
Author(s):  
Muzafar Hussain ◽  
Shahbaz Tahir
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Exchangers ◽  
Single Phase ◽  
Reynolds Numbers ◽  
Operating Conditions ◽  
Phase Model ◽  
Heat Transfer Characteristics ◽  
Eulerian Model ◽  
Transfer Characteristics

Abstract Nanofluids are widely adopted nowadays to enhance the heat transfer characteristics in the solar applications because of their excellent thermophysical properties. In this paper, a modified Eulerian-Eulerian model recently developed based on experiments was validated numerically to account for the deviations from the experimental data. The modified Eulerian-Eulerian model is compared with the single-phase model, Eulerian-Eulerian models for TiO2-water at different operating conditions and deviation from the experimental data for each of the model was documented. However, the modified Eulerian-Eulerian model gave much closer results when compared to the experimental data. For the further extension of work, the modified Eulerian-Eulerian model was applied to different nanofluids in order to investigate their heat transfer characteristics. Three different nanoparticles were investigated namely Cu, MgO, and Ag and their heat transfer characteristics is calculated based on the modified Eulerian-Eulerian model as well as the single-phase model for the comparison. For lower values of Reynolds numbers, the average heat transfer coefficient was almost identical for both models with small percentage of error but for higher Reynolds numbers, the deviation got larger. Therefore, single-phase model is not appropriate for higher Reynolds numbers and modified Eulerian-Eulerian model should be used to accurately predict the heat transfer characteristics of the nanofluids at higher Reynolds numbers. From the analysis it is found that the Ag-water nanofluid have the highest heat transfer characteristics among others and can be employed in the solar heat exchangers to enhance the heat transfer characteristics and to further improve the efficiency.

Simulation of Two-Phase Flow and Heat Transfer in Mini- and Micro-Channels for Concentrating Photovoltaics Cooling

2011 ◽  
Author(s):  
Devin Pellicone ◽  
Alfonso Ortega ◽  
Marcelo del Valle ◽  
Steven Schon
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Single Phase ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Micro Scale ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Micro Channels

Advances in concentrating photovoltaics technology have generated a need for more effective thermal management techniques. Research in photovoltaics has shown that there is a more than 50% decrease in PV cell efficiency when operating temperatures approach 60°C. It is estimated that a waste heat load in excess of 500 W/cm2 will need to be dissipated at a solar concentration of 10,000 suns. Mini- and micro-scale heat exchangers provide the means for large heat transfer coefficients with single phase flow due to the inverse proportionality of Nusselt number with respect to the hydraulic diameter. For very high heat flux situations, single phase forced convection in micro-channels may not be sufficient and hence convective flow boiling in small scale heat exchangers has gained wider scrutiny due to the much higher achievable heat transfer coefficients due to latent heat of vaporization and convective boiling. The purpose of this investigation is to explore a practical and accurate modeling approach for simulating multiphase flow and heat transfer in mini- and micro-channel heat exchangers. The work is specifically aimed at providing a modeling tool to assist in the design of a mini/micro-scale stacked heat exchanger to operate in the boiling regime. The flow side energy and momentum equations have been implemented using a one-dimensional homogeneous approach, with local heat transfer coefficients and friction factors supplied by literature correlations. The channel flow solver has been implemented in MATLAB™ and embedded within the COMSOL™ FEM solver which is used to model the solid side conduction problem. The COMSOL environment allows for parameterization of design variables leading to a fully customizable model of a two-phase heat exchanger.

Effect of Surface Roughness on Thermal-Hydraulic Characteristics of Plate Heat Exchanger

2013 ◽  
Vol 597 ◽  
pp. 63-74 ◽  
Author(s):  
Jan Wajs ◽  
Dariusz Mikielewicz
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Single Phase ◽  
Plate Heat Exchanger ◽  
Heat Transfer Surface ◽  
Surface Model ◽  
Phase System ◽  
Hydraulic Characteristics ◽  
Plate Heat

In the paper the experimental analysis of passive heat transfer intensification in the case of modeled plate heat exchanger is conducted. The plate heat exchanger is chosen for the analysis because this kind of heat exchangers could be prospectively applied in the ORC systems, however other areas or application are equally possible. The experimental set-up was assembled at the Department of Energy and Industrial Apparatus of Gdansk University of Technology. The passive intensification was obtained by a modification of the heat transfer surface. The roughness of surface was increased by use of glass shot.During the experiment single-phase convective heat transfer in the single phase system was studied. The experiment was done in two stages. In the first stage the model of commercial plate heat exchanger was investigated, while in the second stage the identical one but with modified heat transfer surface. Model of heat exchanger consisted of three plates. The direct comparison of thermal and flow characteristics between both devices was possible due to assurance of equivalent conditions at the inlet to the system.The thermal and hydraulic characteristics are presented. The thermal analysis shows that in some range of heat flux density the overall heat transfer coefficient was higher for the commercial heat exchanger, while for the other was higher for the heat exchanger with modified surface. The influence of larger roughness on heat transfer cannot unequivocally be evaluated. Therefore as the next step the systematic investigations of model heat exchangers (only with one hot and one cold passage) will be conducted.

Thermo-Hydrodynamic of the Evaporation of Refrigerant R134A in Brazed Plate Heat Exchangers

Volume 3 ◽  
2004 ◽  
Author(s):  
Amir Jokar ◽  
Steven J. Eckels ◽  
Mohammad H. Hosni
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Single Phase ◽  
Flow Analysis ◽  
Phase Flow ◽  
Water Mixture ◽  
Transfer Coefficients ◽  
Plate Heat ◽  
Evaporation Heat ◽  
Brazed Plate Heat Exchangers

The evaporation of refrigerant R134a in three different sizes of Brazed Plate Heat Exchangers (BPHE) is analyzed in this article. The BPHEs are a type of compact plate heat exchanger with parallel corrugated plates which are brazed together in series. In this study, these heat exchangers are utilized as the evaporator of an automotive refrigeration system, and their heat transfer coefficients and pressure drops are obtained experimentally. The refrigerant flows on one side and a 50% glycol-water mixture on the other side of the BPHEs, in a counter flow configuration. The heat transfer coefficient for the single-phase glycol-water mixture flow through the BPHEs is obtained using the Wilson plot technique. The single-phase Fanning friction factor correlation is also obtained using experimental results from the hydrodynamic parameters of glycol-water mixture. The results from the single-phase flow analysis are then extended to the two-phase flow analysis to correlate the evaporation heat transfer and pressure drop for the refrigerant R134a in the BPHEs. In summary, the thermo-hydrodynamic behavior of the evaporation of R143a in brazed plate heat exchangers is analyzed and compared with previous studies.

An Investigation of Heat Transfer on Microchannel Heat Exchanger Flow Arrangement with Gas Heating

2011 ◽  
Vol 145 ◽  
pp. 262-266 ◽  
Author(s):  
Tsung Lin Liu ◽  
Ben Ran Fu ◽  
Chin Pan
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Single Phase ◽  
Thermal Power ◽  
Phase Zone ◽  
Two Phase ◽  
Exhaust Heat ◽  
Gas Heating ◽  
Actual Effectiveness ◽  
Counter Current

The present study investigates the effect of flow arrangement on heat transfer characteristics in two-phase microchannel heat exchangers (MCHEs) with gas heating. The microchannel heat exchangers are developed to utilize the exhaust heat from a high-temperature gas product of a methanol reformer (a part of a reformed methanol fuel cell). Co-and counter-current flow types of MCHE are tested. Working fluids in the hot and cold sides are helium and liquid methanol, respectively. For both single-phase flow regions, the experimental results indicate that the actual effectiveness of the counter-current MCHE is higher than that of the co-current MCHE. Both of the actual effectiveness of co-and counter-current MCHEs significantly increases with an increase of cold side mass flux. Moreover, the actual effectiveness for both types of MCHE is less relationship to the hot-side thermal power in single-phase zone. The highest actual effectiveness is about 0.6 and 0.72 for co-and counter-current MCHEs, respectively.

scholarly journals Single-Phase Heat Transfer and Fluid Flow Phenomena of Microchannel Heat Exchangers

10.5772/32989 ◽  
2012 ◽  
Author(s):  
Thanhtrung Dang ◽  
Jyh-tong Teng ◽  
Jiann-cherng Chu ◽  
Tingting Xu ◽  
Suyi Huang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Exchangers ◽  
Single Phase ◽  
Flow Phenomena

History, Advances, and Challenges in Liquid Flow and Flow Boiling Heat Transfer in Microchannels: A Critical Review

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Liquid Flow ◽  
Heat Exchangers ◽  
Single Phase ◽  
Heat Dissipation ◽  
Flow Boiling ◽  
Thermal Control ◽  
Future Research ◽  
Practical Implementation ◽  
High Heat Flux

As the scale of devices becomes small, thermal control and heat dissipation from these devices can be effectively accomplished through the implementation of microchannel passages. The small passages provide a high surface area to volume ratio that enables higher heat transfer rates. High performance microchannel heat exchangers are also attractive in applications where space and/or weight constraints dictate the size of a heat exchanger or where performance enhancement is desired. This survey article provides a historical perspective of the progress made in understanding the underlying mechanisms in single-phase liquid flow and two-phase flow boiling processes and their use in high heat flux removal applications. Future research directions for (i) further enhancing the single-phase heat transfer performance and (ii) enabling practical implementation of flow boiling in microchannel heat exchangers are outlined.

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