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1

Effect of serrated circular rings on heat transfer augmentation of circular tube heat exchanger

Kharkwal Himanshi, Singh Satyendra

Archives of Thermodynamics

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2022

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Vol. 43, no 2

129--155

EN

Limiting energy resources has led researchers to find new innovative ways to enhance heat exchanging devices thermal performance in power generating systems. Thus, the present paper analyzes passive techniques of enhancing the thermal performance of a single tube heat exchanger. Experimental and numerical investigation on heat transfer enhancement using aserrated circular ring with twisted tape is carried out. The work incorporates the determination of Nusselt number, friction factor, thermal performance factor for serrated circular ring with twisted tape with variation in diameter ratio (0.8 and 0.85) and pitch ratio (2 and 3). Air is used as a working fluid with Reynolds number 6000–24000. The experiment is conducted by providing a constant wall heat flux of 1000 W/m2 to the system and thereby taking results at a steady state. The experimental and computational findings obtained for the smooth tube case are compared with the standard correlations of Dittus–Boelter and Blasius. Based on experimental and numerical investigation, there is 5.16 times augmentation in heat transfer and 3.05 times improvement in thermal performance factor over the smooth tube heat exchanger. In addition, the study of entropy generation rate for every geometrical parameter has been conducted, and their influence on the system’s thermal behaviour is presented. The results obtained in the present study may help the researchers of the same research area to find similar inserts and new ways of enhancing the thermal performance of heat exchangers.

2

Mixed convection in MHD flow and heat transfer rate near a stagnation-point on a non-linear vertical stretching sheet

Fenuga O. J., Hassan A. R., Olanrewaju P. O.

International Journal of Applied Mechanics and Engineering

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2020

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Vol. 25, no. 1

37--51

EN

This work investigates the mixed convection in a Magnetohydrodynamic (MHD) flow and heat transfer rate near a stagnation-point region over a nonlinear vertical stretching sheet. Using a similarity transformation, the governing equations are transformed into a system of ordinary differential equations which are solved numerically using the fourth order Runge-Kutta method with shooting technique. The influence of pertinent flow parameters on velocity, temperature, surface drag force and heat transfer rate are computed and analyzed. Graphical and tabular results are given to examine the nature of the problem. The heat transfer rate at the surface increases with the mixed convection.

3

Experimental investigation of augmented thermal and performance characteristics of solar air heater ducts due to varied orientations of roughness geometry on the absorber plate

Sahu Mukesh Kumar, Matheswaran M. M., Bishnoi Pardeep

Archives of Thermodynamics

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2020

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Vol. 41, no 3

147--182

EN

This paper presents the outdoor experimental results for thermal performance analysis of artificially roughened solar air heaters (SAHs). Circular wire ribs have been arranged to form arc shape geometry on the absorber plates and have been tested for two configurations of SAHs named as arc shape apex-downstream flow and arc shape apex-upstream flow SAH. Roughness parameters have been taken as relative roughness pitch in the range of 8–15, angle of attack 45°–75°, and for fixed relative roughness height of 0.0454, duct width to duct height ratio of 11. During the experimental analysis the mass flow rate varied from 0.0100 to 0.0471 kg/s. Based on the experimental results it was found that roughness with apexupstream flow SAH is having higher value of thermal efficiency, heat removal factor and collector efficiency factor as compared to roughness with apexdownstream flow SAH and simple absorber plate SAH. In the range of the operating parameters investigated the maximum of thermal efficiency, heat removal factor, and collector efficiency factor have been found.

4

Numerical simulation of flow and heat transfer in hydromagnetic micropolar fluid between two stretchable disks with viscous dissipation effects

Ali K., Ahmad S., Ashraf M.

Journal of Theoretical and Applied Mechanics

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2016

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Vol. 54 nr 2

633--643

EN

A study of magnetohydrodynamic (MHD) flow with viscous dissipation and heat transfer in an electrically conducting laminar steady viscous incompressible micropolar fluid between two infinite uniformly stretching disks is presented. The transformed self similar nonlinear ODEs are first linearized using a quasi linearization method and then solved by employing a combination of a direct and an iterative method. The study may be beneficial to flow and thermal control of polymeric processing.

5

Heat transfer through the regular polyhedrons with asymmetric boundary conditions

Pelińska-Olko E.

Archives of Thermodynamics

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2012

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Vol. 33, no. 3

123-131

EN

During heat transport through the walls of a hollow sphere, the heat stream can achieve extreme values. The same processes occur in regular polyhedrons. We can calculate the maximum heat transfer rate, the so-called critical heat transfer rate. We must assume here identical conditions of heat exchange on all internal and external walls of a regular polyhedron. The transfer rate of heat penetrating through the regular polyhedron with different heat transfer coefficients on the walls is called the heat transfer rate with asymmetric boundary conditions. We show that the heat transfer rate in this case will grow up if we replace those coefficients with their average values.

6

An application of electrochemical technique in analysis of heat distribution in a tube bank during gas-liqiud two-phase flow

Siejka K., Ulbrich R.

Turbulence : international journal

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2007

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Vol. 12

105-113

EN

Electrochemical technique was applied to analyze the heat distribution in a tube bank in a bubbling gas-liquid flow column reactor. Results of the research on distribution of heat transfer rate on the surface of horizontal oriented tube bundles with two-phase gas-liquid crosswise flow in shell side of heat exchangers were presented in the paper. Basing on the obtained results, authors recognize electrochemical technique as very useful and of a great potential. It's noteworthy since it provides for finding mean and local heat transfer coefficients that result from conditions in both hydraulic and thermal developing region. Moreover, this technique seems to be low cost one and is the most accurate of all indirect methods of determining heat transfer coefficient.

7

Modified single-zone model of radiation recuperator with microfinned surface

Karczewski K.

Metallurgy and Foundry Engineering

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2007

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Vol. 33, no. 2

129-139

EN

Modified single-zone model of radiation recuperator with microfinned surface were elaborated. In this model the researches of heat transfer and hydraulic resistance microfinned elements were applied. To calculate the recuperator wall temperature weight mean temperature was used. By elaborated model radiation recuperator with microfinned surface to glass furnace were calculated. Single-zone model makes possible the project of small overall dimensions recuperators to industrial furnaces.

PL

Opracowano zmodyfikowany jednostrefowy model rekuperatora radiacyjnego z mikroużebrowaniem. W modelu wykorzystano badania wymiany ciepła i oporów przepływu mikroużebrowanych elementów rekuperatorowych. Temperaturę ścianki przegrody rekuperatora obliczono średnią ważoną. Według opracowanego modelu zaprojektowano rekuperator radiacyjny z mikroużebrowaniem do pieca szklarskiego. Model jednostrefowy umożliwia projektowanie małych gabarytowo rekuperatorów radiacyjnych do pieców przemysłowych.

8

Universal method of calculation of radiation recuperators with microfinned surface

Karczewski K.

Metallurgy and Foundry Engineering

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2005

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Vol. 31, No 2

185-200

EN

Universal method of calculation of radiation recuperators with microfinned surface were elaborated. The algorithm of method applied: model investigations of heat transfer and hydraulic resistance on recuperator elements with microfins, the surface ratio and micro-fin efficiency. The universal method of calculation developed in the paper makes possible the recuperator's design to industrial furnace.

PL

Opracowano ogólną metodę obliczeń rekuperatorów radiacyjnych z mikroużebrowaniem. W algorytmie obliczeń zastosowano badania modelowe intensyfikacji wnikania ciepła i oporów przepływu elementów rekuperatorowych z mikroużebrowaniem, stosunek mikroużebrowania i sprawność mikrożebra. Ogólna metoda obliczeń umożliwiła wykonanie konstrukcji rekuperatora radiacyjnego do pieca przemysłowego.

9

Modified zonal model of radiation recuperators with microfinned surface

Karczewski K.

Metallurgy and Foundry Engineering

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2004

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Vol. 30, No 1

43-59

EN

Modified zonal model of radiation recuperators with microfinned surface was elaborated. The model equations are describing the function between walls, furnace gas and preheating air temperatures. In equations model researches heat transfer and hydraulic resistance of recuperator microfinned elements was applied. To calculate the recuperator wall temperature the rule of falsi method was used. Modified zonal model makes possible the projects of radiation recuperators with microfinned surface to industrial furnace.

PL

Opracowano zmodyfikowany strefowy model rekuperatorów radiacyjnych z mikroużebrowaniem. Równania modelu opisują zależności pomiędzy temperaturami ścian przegród, spalin i podgrzanego powietrza. W równaniach wykorzystano badania wymiany ciepła i oporów przepływu elementów rekuperatorowych z mikroużebrowaniem. Do obliczenia temperatury ścianki rekuperatora dostosowano metodę „reguła falsi". Zmodyfikowany strefowy model umożliwia projektowanie rekuperatorów radiacyjnych z mikroużebrowaniem dla pieców przemysłowych.