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Applications
Published in Raj P. Chhabra, CRC Handbook of Thermal Engineering Second Edition, 2017
Joshua D. Ramsey, Ken Bell, Ramesh K. Shah, Bengt Sundén, Zan Wu, Clement Kleinstreuer, Zelin Xu, D. Ian Wilson, Graham T. Polley, John A. Pearce, Kenneth R. Diller, Jonathan W. Valvano, David W. Yarbrough, Moncef Krarti, John Zhai, Jan Kośny, Christian K. Bach, Ian H. Bell, Craig R. Bradshaw, Eckhard A. Groll, Abhinav Krishna, Orkan Kurtulus, Margaret M. Mathison, Bryce Shaffer, Bin Yang, Xinye Zhang, Davide Ziviani, Robert F. Boehm, Anthony F. Mills, Santanu Bandyopadhyay, Shankar Narasimhan, Donald L. Fenton, Raj M. Manglik, Sameer Khandekar, Mario F. Trujillo, Rolf D. Reitz, Milind A. Jog, Prabhat Kumar, K.P. Sandeep, Sanjiv Sinha, Krishna Valavala, Jun Ma, Pradeep Lall, Harold R. Jacobs, Mangesh Chaudhari, Amit Agrawal, Robert J. Moffat, Tadhg O’Donovan, Jungho Kim, S.A. Sherif, Alan T. McDonald, Arturo Pacheco-Vega, Gerardo Diaz, Mihir Sen, K.T. Yang, Martine Rueff, Evelyne Mauret, Pawel Wawrzyniak, Ireneusz Zbicinski, Mariia Sobulska, P.S. Ghoshdastidar, Naveen Tiwari, Rajappa Tadepalli, Raj Ganesh S. Pala, Desh Bandhu Singh, G. N. Tiwari
Heat transfer enhancement [or enhanced heat transfer, or for that matter enhanced mass transfer (Bergles et al., 1983; Manglik and Bergles, 2004)] refers to the study of techniques for improving the thermal performance of a heat (or mass) exchange device or system. It is sometimes also referred to as heat transfer augmentation or intensification. In general, this entails an increase in the heat transfer coefficient and encapsulates the broader science and engineering of methods for producing higher convective heat/mass transfer coefficients, reducing frictional losses, and increasing the overall thermal–hydrodynamic efficiencies of exchangers. Attempts to increase “normal” heat transfer coefficients have been recorded for more than 150 years in modern history (Bergles and Manglik, 2013) and indeed date back several thousand years in antiquity (Manglik and Jog, 2009). As a result, there is a very large store of information that has been documented and disseminated in several periodic surveys (Manglik and Bergles, 2004; Bergles and Manglik, 2013; Manglik et al., 2013). The literature comprising of technical publications, excluding patents and manufacturers’ literature, has expanded rapidly since 1955 and approximately 350–450 papers and reports on the subject are now published annually.
Fouling on Enhanced Surfaces
Published in Ralph L. Webb, Nae-Hyun Kim, Principles of Enhanced Heat Transfer, 2004
The commercial viability of enhanced heat transfer surfaces is dependent on their long-term fouling characteristics. The problem of heat transfer surface fouling is of concern for both plain and enhanced surfaces. Although fouling is generally regarded as a more serious problem for liquids than for gases, gas-side fouling can be important in certain situations. Section 2.7 describes the importance of fouling in heat exchanger design and explains why fouling is an important concern for enhanced surfaces. A primary concern for enhanced surfaces is their fouling rate, relative to a plain surface, when operated at the same velocity. At present, the state of the art does not allow quantitative prediction of the fouling resistance that will occur on smooth or enhanced surfaces in actual field installations. However, recent and ongoing research is advancing our quantitative understanding of fouling phenomena. Readers interested in general information describing the state of the art on fouling are referred to books by Somerscales and Knudsen [1979], Garrett-Price et al. [1985], Melo et al. [1987], and Bott [1995]. Watkinson [1990, 1991] and Bergles and Sommerscales [1995] provide review articles of fouling on enhanced heat transfer surfaces.
Recent Progress on Nanofluids and Their Potential Applications
Published in Victor M. Starov, Nanoscience, 2010
J. R. Moffat, K. Sefiane, R. Bennacer, Y. Guo
However, nanofluids are two-phase fluids in nature and have some common features of solid–liquid mixtures. Several factors, such as gravity, Brownian force, and friction force between the fluid and ultrafine solid particles, the phenomena of Brownian diffusion, sedimentation, dispersion, may coexist in the main flow of a nanofluid. Considering this, the slip velocity between the fluid and the particles may not be zero, despite the particle sizes. Irregular and random movement of the particles increases the energy exchange rates in the fluid, that is, thermal dispersion takes place in the flow of the nanofluid. The single-phase approach cannot account for this. A modified single-phase dispersion model was developed to account for both mechanisms [12,54], where an analogy with the treatment of turbulence was adopted to indicate the effect of thermal dispersion resulting from the chaotic movement of nanoparticles in the flow. A heat transfer correlation for nanofluid was obtained thus: Nux=[1+C⋅Penf′(0)]θ′(0)Rem, where f′ and θ‘ are the derivatives of dimensionless velocity and dimensionless temperature, respectively. Experimental work was undertaken to determine the unknown parameter in the derived formula. The authors of Ref. [54] indicated that nanoparticles enhanced heat transfer rate by increasing the thermal conductivity of the nanofluid and incurring thermal dispersion in the flow, which was an innovative way of augmenting heat transfer process.
Numerical study on structure optimization and heat transfer characteristic of distributed pulsating flow heat exchanger
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Lei Chen, Hongxin Zhang, Song Huang, Jianjun Li
According to Figure 12, these can be concluded: (1) The irregular velocity streamlines from the branch pipe with the vortex generator interweaved through the sixth layer from the first layer of the tube bundle, filling the entire shell domain. (2) The area percentage of high-temperature contour in the shell domain increases (The average temperature of the fluid in the shell domain is 316.81 K). (3) Area percentage of heigh-velocity contour, the area percentage of heigh turbulence eddy frequency, and the area percentage of heigh turbulence kinetic energy in shell domain fluid all increase. After calculating the results obtained from numerical simulations with the selected optimal parameters, the average surface Nusselt number Nuv of DPFETB-HE is 26.5. It is 3 times the minimum Nuv (Test1), 1.61 times the average Nuv obtained in Test1-Test9, increase 7.22% over the maximum Nuv (Test9). Therefore, the comparison results mentioned above are sufficient to demonstrate the optimal parameters obtained by the Taguchi method in this paper can effectively improve the heat transfer performance of DPFETB-HE. Therefore, the above studies have important theoretical significance and practical value in optimizing and developing heat exchange equipment and enhanced heat transfer technology.
Control volume finite element method for entropy generation minimization in mixed convection of nanofluids
Published in Numerical Heat Transfer, Part B: Fundamentals, 2019
As described previously, nanofluids are fluids which contain nanoscale particles and typically have enhanced heat transfer characteristics and thermal conductivity when compared to a base fluid such as water, ethylene glycol, or oil. Nanoparticles are made from the synthesis of metallic or nonmetallic materials such as metals, nitrides, oxides, and graphite. They can be synthesized by various procedures such as gas condensation, chemical precipitation, or mechanical attrition. Nanofluids are formed through a colloidal mixture of nanoparticles and a base fluid. Limitations and challenges of nanofluids in engineering systems include possible wall surface erosion, an increase in pumping power due to the presence of nanoparticles, and potential instability due to silts of particles.
Numerical investigation of transient responses of triangular fins having linear and power law property variation under step changes in base temperature and base heat flux using lattice Boltzmann method
Published in Numerical Heat Transfer, Part A: Applications, 2021
Abhishek Sahu, Shubhankar Bhowmick
Extended surface [1] have been arresting the interest of researcher from last 100 year since the breakthrough by Harper and Brown [2], thereafter inspired by this work, fins are used in air cooled, aircraft engine to enhance the heat transfer work, furthermore analysis of trapezoidal fin and radial fin are also done. This was a masterful commencement for analysis of fin or array of fins. Applications of fins are not limited, it can be used efficiently in the applications such as cooling of electronic component, heat exchanger devices to enhance the heat transfer rate and to extract the heat from surrounding. The various applications area of fins are space vehicles, gas turbine engine, and internal combustion engine, refrigeration systems, air-cooled heat exchangers, gas turbine blades, condensing heat exchangers, etc. Fins are the extended surfaces, wherein enhanced heat transfer is achieved by adding thin metal strips on the primary surface. The phenomena of heat transfer in the fin start by conducting the heat through extended solid surface and the surrounding fluid takes away the heat by convection. These processes start only when the primary surface (fin base) of the fin is subjected to either temperature or heat flux. Once the process is completed, the temperature at any location does not change with respect to time for a given set of boundary conditions, a state of equilibrium is reached known as steady state. However, this requirement of enhanced heat transfer is achieved on the expense of cost of extra material and weight/volume of the material. In designing of fins, minimum volume of fins could be achieved by selecting the suitable profile of fins and considering the transient analysis. It will design fins under specific operating condition, hereby the precise amount of material is selected for specific application. This will help in utilization of precise amount of material in designing of fins for specific application.