scholarly journals Heat Transfer Enhancement due to Acoustic Fields: A Methodological Analysis

Acoustics ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 281-294 ◽  
Author(s):  
Alessandro Franco ◽  
Carlo Bartoli
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Thermodynamic System ◽  
Industrial Applications ◽  
General Validity ◽  
Physical Mechanisms ◽  
Physical Phenomena

The aim of this paper is to expose the main involved physical phenomena underlying the alteration of convective heat transfer in a heat exchanger subjected to imposed vibrations. This technique seems to have interesting features and industrial applications, such as for efficiency increases, heat transfer rate control and cleanliness action. However, a clear description and comprehension of how vibrations may alter the convective heat transfer coefficient in a heat exchanger has still not been reached due to the complexity of the involved physical mechanisms. For this reason, after a presentation and a schematization of the analyzed thermodynamic system, the fundamental alterations of the thermo-fluid dynamics fields are described. Then, the main involved physical phenomena are exposed for the three cases of gaseous, monophasic liquid and boiling liquid mediums. Finally, on the basis of the characteristics of these described phenomena, some considerations and indications of general validity are presented.

scholarly journals Heat Transfer Enhancement with Acoustic Fields: An Exposition of the Main Involved Physical Phenomena

2019 ◽  
Author(s):  
Alessandro Franco ◽  
Carlo Bartoli
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Thermodynamic System ◽  
Industrial Applications ◽  
General Validity ◽  
Efficiency Increase ◽  
Physical Phenomena

The aim of this paper is to expose the main involved physical phenomena underlying the alteration of convective heat transfer in a heat exchanger subjected to imposed vibrations. This technique seems to have interesting features and industrial applications, such as efficiency increase, heat transfer rate control and cleanliness action. However, a clear description and comprehension of how vibrations may alter the convective heat transfer coefficient in a heat exchanger is no still reached due to the complexity of the involved physical mechanisms. For this reason, after a presentation and a schematisation of the analyzed thermodynamic system, the fundamental alterations of the thermo-fluid dynamics fields are described. Then, the main involved physical phenomena are exposed for the three cases of gaseous, monophasic liquid and boiling liquid mediums. Finally, on the basis of the characteristics of these described phenomena, some considerations and indications of general validity are presented.

scholarly journals Experimental Study on a Pulsation-enhanced Heat Transfer Device

2020 ◽  
Vol 6 (4) ◽  
pp. 243-251
Author(s):  
Z. Liu ◽  
A. Levtsev ◽  
Y. Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Heat Flow ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Pulsation Frequency ◽  
Enhanced Heat Transfer

The pulsation-enhanced heat transfer technology is introduced, and a volume coil heat exchanger is designed. A pulsation valve is installed at the heat exchanger outlet of the heat exchanger to pulsate the heat medium, and the same heat exchanger is subjected to pulsation and non-pulsation heat transfer tests. Based on the experiments, combined with the theory of pulsation-enhanced heat transfer technology, heat transfer capacity, heat flow, and convective heat transfer coefficient coefficients, the effective temperature difference, heat flow, and convective heat transfer coefficient of the heat exchanger at different pulse frequencies are analyzed. The relationship between the pulsation frequency of the heat transfer effect of the heat exchanger is obtained. The test results show that the heat exchanger has higher heat exchange efficiency when there is pulsation under the test conditions.

Heat Transfer Enhancement in Split and Recombine Flow Configurations: A Numerical and Experimental Study

2016 ◽  
Author(s):  
Mojtaba Jarrahi ◽  
Jean-Pierre Thermeau ◽  
Hassan Peerhossaini
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Working Fluid ◽  
Transfer Enhancement

Heat transfer enhancement in laminar regime by split and recombine (SAR) mechanism, based on the baker’s transformation, is investigated. Two different heat exchangers, called SAR1 and SAR2, are studied. Their geometries are inspired from the previous studies reported in the literature. The working fluid on both, shell and tube side, is water and the temperature on the shell side is kept constant. Experiments are carried out for the Reynolds number range 100<Re<3000 when the Prandtl number is between 4.5 and 7.5. The results show that the convective heat transfer coefficient in the first element of heat exchanger SAR1 is higher than that in the second one, i.e. SAR2. However, the variation in the convective heat transfer coefficient from the first to the third element along the heat exchanger SAR2 is less significant than that observed for SAR1. Moreover, SAR2 causes a higher pressure drop, especially when Re>1000, and provides a less uniform temperature field at the outlet.

Heat Transfer Analysis of Internally Grooved Copper Tube R404-A Evaporators

2012 ◽  
Author(s):  
Cenk Onan ◽  
Derya B. Ozkan ◽  
Levent Ceran
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Copper Tube ◽  
Tube Heat Exchanger ◽  
Grooved Tube

Internally grooved copper tubes are used extensively in HVAC applications, direct expansion batteries and air or water cooled heat exchangers. The advantage of internally grooved copper tubes in evaporator and condenser units is an increase in the refrigerant-side heat transfer coefficient. When an internally grooved tube heat exchanger and a smooth-tube heat exchanger with the same dimensions are compared, the overall heat transfer coefficient and convective heat transfer coefficient are found to increase in different ratios. In addition to this difference, the refrigerant side pressure is found to be a function of the groove geometry, pitch space and choice of refrigerant. In this study, which is different from previous studies in the literature performed using single internally grooved tube condensers and evaporators, refrigerant R404-A is studied in the internally grooved tube evaporator. The heat transfer in the evaporator described here is 30% better than that observed in a conventional smooth-copper-tube evaporator. In the internally grooved tube, the internal surface area is 68% larger than that inside the smooth reference tube. As a result, the convective heat transfer coefficient inside the internally grooved tube is found to be lower than that in the smooth tube.

Enhancement of Heat Transfer by Nanoparticles Added to the Working Fluid of Swimming Pool Heat Exchangers

2012 ◽  
Author(s):  
N. Ashrafi ◽  
Y. Bashirzadeh
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Convective Heat Transfer ◽  
Tio2 Nanoparticles ◽  
Convective Heat ◽  
Heat Exchangers ◽  
Convective Heat Transfer Coefficient ◽  
Swimming Pool ◽  
Working Fluid ◽  
Enhancement Of Heat Transfer

The present experimental study reports on enhancement of heat transfer by addition of nanoparticles to the working fluid of commercial swimming pool heat exchangers under laminar flow condition. Three different concentrations of Titanium dioxide nanoparticles were added to the water as working fluid of a typical forced convective heat exchanger used to transfer heat to public swimming pools. The experimental setup is capable of measuring velocity, heat transfer rate, and temperature at different points. TiO2 nanoparticles with mean diameter of 20 nm were used. The effects of concentration of suspended nanoparticles and that of Reynolds number on forced convective heat transfer were investigated. It is observed that at 0.1%, 0.5% and 1% weight concentration of suspended TiO2 nanoparticles, the average convective heat transfer coefficient improved by 1.1%, 15.9% and 31.6% respectively. The coefficient is further increased at higher Reynolds numbers. The efficiency of heat exchanger is evaluated for different scenarios.

scholarly journals Convective Heat Transfer and Pumping Power Analysis of MWCNT + Fe3O4/Water Hybrid Nanofluid in a Helical Coiled Heat Exchanger with Orthogonal Rib Turbulators

2021 ◽  
Vol 9 ◽  
Author(s):  
Misagh Irandoost Shahrestani ◽  
Ehsan Houshfar ◽  
Mehdi Ashjaee ◽  
Payam Allahvirdizadeh
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Exchangers ◽  
Volume Fraction ◽  
Convective Heat Transfer Coefficient ◽  
Hybrid Nanofluid ◽  
Pumping Power ◽  
Rib Turbulators

Utilizing nanofluids in heat exchangers can lead to improved thermal performance. Nanofluids with suspended carbon nanotubes are specifically desirable in thermal systems because of their unique capabilities. In this study, convective heat transfer and required pumping power are studied simultaneously for a helical coiled heat exchanger with laminar water flow while incorporating 0.1 and 0.3 percent volume fraction of the hybrid nanofluid MWCNT + Fe3O4/water. Two different geometries of bare and ribbed tubes are used for the heat exchanger part. The ribs are chosen to be orthogonal, i.e., 90° with respect to the inclined ones. Three different Reynolds numbers are selected for investigation, all in laminar flow regime based on the non-dimensional M number defined in coiled tubes. Computational fluid dynamics is used to study thermal and fluid behavior of the problem. The convective heat transfer coefficient can serve as a criterion to measure the effectiveness of utilizing nanofluids in heat exchangers by taking the pressure drop and pumping power of the system into consideration. Finally, the artificial neural network curve fitting tool of MATLAB is used to make a good fit in the data range of the problem. It is shown that for most cases of the study, the pumping power ratio is less than 1 that can be considered appropriate from energy consumption viewpoint.

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