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Pongjet Promvonge - One of the best experts on this subject based on the ideXlab platform.
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thermo hydraulic performance in Heat Exchanger Tube with v shaped winglet vortex generator
Applied Thermal Engineering, 2020Co-Authors: Pongjet Promvonge, Sompol SkullongAbstract:Abstract This article presents the influence of V-shaped winglet vortex generators (V-WVGs) inserted into a constant Heat-fluxed Tube on thermal characteristics. In the present experiment, two V-WVG types: V-shaped rectangular- and delta-winglets (V-RW and V-DW) were mounted periodically on both sides of a straight tape before insertion into the Tube with four relative winglet pitches (PR = P/D = 0.5, 1.0, 1.5 and 2.0) and three winglet blockage ratios (BR = b/D = 0.1, 0.15 and 0.2) at a fixed attack angle (α = 45°). Effects of geometric parameters of both V-WVGs on thermal performance enhancement were studied using air as tested fluid in a turbulence condition, Reynolds number (Re) ranging between 4130 and 25,900. The measured result has been shown that the V-RW performs higher rate of Heat transfer as well as friction loss than the V-DW and the rise in BR results in higher increase of the Heat transfer rate and friction loss while the increment in PR yields the reversing tendency for both V-WVG types. A new thermal-performance enhancement factor (TEF) has been introduced and it reveals that the V-DW has TEF in a range of 1.82–2.0 or around 3% above the V-RW where its peak regarded as the optimal point is at BR = 0.15 and PR = 1.0. Empirical correlations for the Nusselt number and friction factor to assess the real merits of a Heat Exchanger Tube with V-WVGs are determined.
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thermal performance of Heat Exchanger Tube inserted with curved winglet tapes
Applied Thermal Engineering, 2018Co-Authors: Sompol Skullong, Pongjet Promvonge, Chinaruk Thianpong, Nuthvipa Jayranaiwachira, Monsak PimsarnAbstract:Abstract The paper deals with the effect of curved-winglet (CW) inserts on thermal and flow behaviors in a constant Heat-fluxed Tube. A straight tape is used to support the 45° CWs mounted repeatedly on both tape sides to generate two pairs of longitudinal counter-rotating vortices along the test Tube in order to assist the chaotic flow mixing and to disrupt the boundary layer leading to faster rate of Heat transfer. The airflow and Heat transfer behaviors in the Tube are examined for Reynolds number (Re) in the range of 4150–25,400. The curved-winglet tape (CWT) parameters involved are the winglet attack angle of 45°, three relative winglet heights (b/D = BR = 0.1, 0.2 and 0.3) and winglet pitches, (P/D = PR = 0.5, 1.0 and 2.0). The investigation reveals that the maximum thermal enhancement factor (TEF) of the CWT is about 1.62 at BR = 0.1 and PR = 1.0. For further improvement, the CWT at BR = 0.1 and PR = 1.0 is modified by punching the CW to be the perforated-curved-winglet tape (P-CWT) to reduce the pressure loss. The P-CWT characteristics include five different punched hole diameters (d = 1.0, 1.5, 2.0, 2.5 and 3.0 mm). The experimental results show that TEF of all the P-CWTs is higher than that of the CWT and the maximum TEF of 1.76 higher than the CWT around 9% is found for d = 1.5 mm. To understand the flow pattern and Heat transfer mechanism, a three-dimensional CFD investigation is also performed and for validation, the good agreement between numerical and experimental results is found. For experimental data, empirical correlations for Nu, f and TEF for the CWT and P-CWT inserts are also determined.
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experimental and numerical Heat transfer investigation in a tubular Heat Exchanger with delta wing tape inserts
Chemical Engineering and Processing, 2016Co-Authors: Sompol Skullong, Pongjet Promvonge, Nuthvipa Jayranaiwachira, Chinaruk ThianpongAbstract:Abstract Effects of insertion of a straight tape with double-sided delta wing pairs (called “delta-wing tape”, DWT) used as a longitudinal vortex generator (LVG) on forced convective Heat transfer and flow friction characteristics in a uniform Heat-flux Heat Exchanger Tube are investigated experimentally and numerically in the present work. The experiment is conducted for turbulent airflow with the Reynolds number (Re) from 4200 to 25,500. The delta wings are in a forward-wing arrangement with three wing inclination angles (α = 30°, 45° and 60°) and with five ratios of wing-pitch to Tube-diameter (P/D = PR = 0.5, 1.0, 1.5, 2.0 and 2.5). Influences of the DWT insert on Heat transfer in terms of Nusselt number (Nu) and pressure drop in the form of friction factor (f) are examined. The results indicate that the DWT provides the increases in Nu and f up to 505% and 69 times above the plain Tube, respectively and the maximum thermal enhancement factor (TEF) is at 1.49. The 60° DWT with PR = 0.5 yields the highest Nu and f but the 30° one with PR = 1.0 gives the best TEF. To understand the flow structure and Heat transfer mechanism, a three dimensional CFD simulation of the inserted Tube is also performed. The simulated results are validated and are in good agreement with the current measurements. A simulated Heat transfer and fluid flow structure is also reported.
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thermal performance enhancement in a Heat Exchanger Tube fitted with inclined vortex rings
Applied Thermal Engineering, 2014Co-Authors: Pongjet Promvonge, Narin Koolnapadol, Monsak Pimsarn, Chinaruk ThianpongAbstract:Abstract The influence of inclined vortex rings (VR) on Heat transfer augmentation in a uniform Heat-fluxed Tube has been investigated experimentally. In the present work, the 30° inclined VRs were mounted repeatedly in the Tube with various geometry parameters of the VR, three relative ring width ratios (BR = b/D = 0.1, 0.15 and 0.2) and four relative ring pitch ratios (PR = P/D = 0.5, 1.0, 1.5 and 2.0). Air was employed as the test fluid in the Tube for the Reynolds number from 5000 to 26,000. The aim at using the VRs is to create counter-rotating vortices inside the Tube to help increase the turbulence intensity as well as to convey the colder fluid from the core regime to the Heated-wall region. To find an optimum thermal performance condition, the effect of BR and PR values on the Heat transfer and pressure loss in the Tube is examined. The experimental results show a significant effect of the presence of the VRs on the Heat transfer and pressure loss over the smooth Tube. The larger BR value provides higher Heat transfer and pressure loss than the smaller one while the PR gives an opposite trend. However, the VR at BR = 0.1 and PR = 0.5 yields the best thermal performance.
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effect of perforated twisted tapes with parallel wings on Heat tansfer enhancement in a Heat Exchanger Tube
Energy Procedia, 2012Co-Authors: Chinaruk Thianpong, Pongjet Promvonge, Petpices Eiamsaard, Smith EiamsaardAbstract:Abstract This article reports an experimental investigation on Heat transfer and pressure drop characteristics of turbulent flow n a Heating Tube equipped with perforated twisted tapes with parallel wings (PTT) for Reynolds number between 500 and 20500. The design of PTT involves the following concepts: (1) wings induce an extra turbulence near Tube all and thus efficiently disrupt a thermal boundary layer (2) holes existing along a core Tube, diminish pressure losswithin the Tube. The parameters investigated were the hole diameter ratio (d/W = 0.11, 0.33 and 0.55) and wing depthratio (w/W = 0.11, 0.22 and 0.33). A typical twisted tape was also tested for an assessment. Compared to the plain ube, the Tubes with PTT and TT yielded Heat transfer enhancement up to 208% and 190%, respectively. The valuation of overall performance under the same pumping power reveal that the PTT with d/W = 0.11 and w/W = .33, gave the maximum thermal performance factor of 1.32, at Reynolds number of 5500. Empirical correlations of he Heat transfer, friction factor and thermal performance for Tubes with PTTs were also developed. In addition, the wirling/axial flow patterns of Tube with PTT were visualized using dye injection technique.
Smith Eiamsaard - One of the best experts on this subject based on the ideXlab platform.
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Heat transfer enhancement of tio2 water nanofluid in a Heat Exchanger Tube equipped with overlapped dual twisted tapes
Engineering Science and Technology an International Journal, 2015Co-Authors: Smith Eiamsaard, K Kiatkittipong, W JedsadaratanachaiAbstract:Abstract Titanium dioxide (TiO 2 ) in water as nanofluid was employed for Heat transfer enhancement together with overlapped dual twisted tapes (O-DTs). The study encompassed Reynolds numbers from 5400 to 15,200, O-DTs with overlapped twist ratios ( y o / y ) of 1.5, 2.0 and 2.5 and nanofluids with TiO 2 volume concentrations ( ϕ ) of 0.07%, 0.14% and 0.21%. The experimental and numerical results indicated that O-DTs with smaller overlapped twisted ratio delivered a stronger swirl intensity and higher turbulent kinetic energy (TKE). The use of O-DTs at the smallest overlapped twist ratio of 1.5 enhanced Heat transfer rates up to 89%, friction factor by 5.43 times and thermal performance up to 1.13 times as compared to those of plain Tube. In addition, Heat transfer increased as TiO 2 volume concentration of nanofluid increased, owing to the increases of contact surface and thermal conductivity. The simultaneous use of the O-DTs having twist ratios 1.5 with the nanofluid with TiO 2 volume concentration of 0.21% resulted in Heat transfer enhancement around 9.9–11.2% and thermal performance improvement up to 4.5% as compared to the use of O-DTs alone. The empirical correlations of Heat transfer rate ( Nu ), friction factor ( f ) and thermal performance ( η ) in a constant wall Heat flux Tube equipped O-DTs at different overlapped twist ratios ( y o / y ) and volume concentrations of TiO 2 nanoparticles ( ϕ ) are also reported for Heat transfer applications.
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effect of perforated twisted tapes with parallel wings on Heat tansfer enhancement in a Heat Exchanger Tube
Energy Procedia, 2012Co-Authors: Chinaruk Thianpong, Pongjet Promvonge, Petpices Eiamsaard, Smith EiamsaardAbstract:Abstract This article reports an experimental investigation on Heat transfer and pressure drop characteristics of turbulent flow n a Heating Tube equipped with perforated twisted tapes with parallel wings (PTT) for Reynolds number between 500 and 20500. The design of PTT involves the following concepts: (1) wings induce an extra turbulence near Tube all and thus efficiently disrupt a thermal boundary layer (2) holes existing along a core Tube, diminish pressure losswithin the Tube. The parameters investigated were the hole diameter ratio (d/W = 0.11, 0.33 and 0.55) and wing depthratio (w/W = 0.11, 0.22 and 0.33). A typical twisted tape was also tested for an assessment. Compared to the plain ube, the Tubes with PTT and TT yielded Heat transfer enhancement up to 208% and 190%, respectively. The valuation of overall performance under the same pumping power reveal that the PTT with d/W = 0.11 and w/W = .33, gave the maximum thermal performance factor of 1.32, at Reynolds number of 5500. Empirical correlations of he Heat transfer, friction factor and thermal performance for Tubes with PTTs were also developed. In addition, the wirling/axial flow patterns of Tube with PTT were visualized using dye injection technique.
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influence of double sided delta wing tape insert with alternate axes on flow and Heat transfer characteristics in a Heat Exchanger Tube
Chinese Journal of Chemical Engineering, 2011Co-Authors: Smith Eiamsaard, Pongjet PromvongeAbstract:Abstract The convective Heat transfer and friction behaviors of turbulent Tube flow through a straight tape with double-sided delta wings (T-W) have been studied experimentally. In the current work, the T-W formed on the tape was used as vortex generators for enhancing the Heat transfer coefficient by breakdown of thermal boundary layer and by mixing of fluid flow in Tubes. The T-W characteristics are (1) T-W with forward/backward-wing arrangement, (2) T-W with alternate axis (T-WA), (3) three wing-width ratios and (4) wing-pitch ratios. The experimental result reveals that for using the T-W, the increases in the mean Nusselt number ( Nu ) and friction factor are, respectively, up to 165% and 14.8 times of the plain Tube and the maximum thermal performance factor is 1.19. It is also obvious that the T-W with forward-wing gives higher Heat transfer rate than one with backward-wing around 7%. The present investigation also shows that the Heat transfer rate and friction factor obtained from the T-WA is higher than that from the T-W. In addition, the flow pattern and temperature fields in the T-W Tube with both backward and forward wings were also examined numerically.
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experimental investigation of convective Heat transfer and pressure loss in a round Tube fitted with circular ring turbulators
International Communications in Heat and Mass Transfer, 2010Co-Authors: Vichan Kongkaitpaiboon, K. Nanan, Smith EiamsaardAbstract:Abstract This paper presents the effect of the circular-ring turbulator (CRT) on the Heat transfer and fluid friction characteristics in a Heat Exchanger Tube. The experiments were conducted by insertion of CRTs with various geometries, including three different diameter ratios (DR = d/D = 0.5, 0.6 and 0.7) and three different pitch ratios (PR = p/D = 6, 8 and 12). During the test air at 27 °C was passed through the test Tube which was controlled under uniform wall Heat flux condition. The Reynolds number was varied from 4000 to 20,000. According to the experimental results, Heat transfer rates in the Tube fitted with CRTs are augmented around 57% to 195% compared to that in the plain Tube, depending upon operating conditions. In addition, the results also reveal the CRT with the smallest pitch and diameter ratios offers the highest Heat transfer rate in accompany with the largest pressure loss.
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experimental investigation of convective Heat transfer and pressure loss in a round Tube fitted with circular ring turbulators
International Communications in Heat and Mass Transfer, 2010Co-Authors: Vichan Kongkaitpaiboon, K. Nanan, Smith EiamsaardAbstract:article i nfo Available online 14 February 2010 This paper presents the effect of the circular-ring turbulator (CRT) on the Heat transfer and fluid friction characteristics in a Heat Exchanger Tube. The experiments were conducted by insertion of CRTs with various geometries, including three different diameter ratios (DR=d/D=0.5, 0.6 and 0.7) and three different pitch ratios (PR=p/D=6, 8 and 12). During the test air at 27 °C was passed through the test Tube which was controlled under uniform wall Heat flux condition. The Reynolds number was varied from 4000 to 20,000. According to the experimental results, Heat transfer rates in the Tube fitted with CRTs are augmented around 57% to 195% compared to that in the plain Tube, depending upon operating conditions. In addition, the results also reveal the CRT with the smallest pitch and diameter ratios offers the highest Heat transfer rate in accompany with the largest pressure loss.
Chinaruk Thianpong - One of the best experts on this subject based on the ideXlab platform.
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thermal performance of Heat Exchanger Tube inserted with curved winglet tapes
Applied Thermal Engineering, 2018Co-Authors: Sompol Skullong, Pongjet Promvonge, Chinaruk Thianpong, Nuthvipa Jayranaiwachira, Monsak PimsarnAbstract:Abstract The paper deals with the effect of curved-winglet (CW) inserts on thermal and flow behaviors in a constant Heat-fluxed Tube. A straight tape is used to support the 45° CWs mounted repeatedly on both tape sides to generate two pairs of longitudinal counter-rotating vortices along the test Tube in order to assist the chaotic flow mixing and to disrupt the boundary layer leading to faster rate of Heat transfer. The airflow and Heat transfer behaviors in the Tube are examined for Reynolds number (Re) in the range of 4150–25,400. The curved-winglet tape (CWT) parameters involved are the winglet attack angle of 45°, three relative winglet heights (b/D = BR = 0.1, 0.2 and 0.3) and winglet pitches, (P/D = PR = 0.5, 1.0 and 2.0). The investigation reveals that the maximum thermal enhancement factor (TEF) of the CWT is about 1.62 at BR = 0.1 and PR = 1.0. For further improvement, the CWT at BR = 0.1 and PR = 1.0 is modified by punching the CW to be the perforated-curved-winglet tape (P-CWT) to reduce the pressure loss. The P-CWT characteristics include five different punched hole diameters (d = 1.0, 1.5, 2.0, 2.5 and 3.0 mm). The experimental results show that TEF of all the P-CWTs is higher than that of the CWT and the maximum TEF of 1.76 higher than the CWT around 9% is found for d = 1.5 mm. To understand the flow pattern and Heat transfer mechanism, a three-dimensional CFD investigation is also performed and for validation, the good agreement between numerical and experimental results is found. For experimental data, empirical correlations for Nu, f and TEF for the CWT and P-CWT inserts are also determined.
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experimental and numerical Heat transfer investigation in a tubular Heat Exchanger with delta wing tape inserts
Chemical Engineering and Processing, 2016Co-Authors: Sompol Skullong, Pongjet Promvonge, Nuthvipa Jayranaiwachira, Chinaruk ThianpongAbstract:Abstract Effects of insertion of a straight tape with double-sided delta wing pairs (called “delta-wing tape”, DWT) used as a longitudinal vortex generator (LVG) on forced convective Heat transfer and flow friction characteristics in a uniform Heat-flux Heat Exchanger Tube are investigated experimentally and numerically in the present work. The experiment is conducted for turbulent airflow with the Reynolds number (Re) from 4200 to 25,500. The delta wings are in a forward-wing arrangement with three wing inclination angles (α = 30°, 45° and 60°) and with five ratios of wing-pitch to Tube-diameter (P/D = PR = 0.5, 1.0, 1.5, 2.0 and 2.5). Influences of the DWT insert on Heat transfer in terms of Nusselt number (Nu) and pressure drop in the form of friction factor (f) are examined. The results indicate that the DWT provides the increases in Nu and f up to 505% and 69 times above the plain Tube, respectively and the maximum thermal enhancement factor (TEF) is at 1.49. The 60° DWT with PR = 0.5 yields the highest Nu and f but the 30° one with PR = 1.0 gives the best TEF. To understand the flow structure and Heat transfer mechanism, a three dimensional CFD simulation of the inserted Tube is also performed. The simulated results are validated and are in good agreement with the current measurements. A simulated Heat transfer and fluid flow structure is also reported.
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thermal performance enhancement in a Heat Exchanger Tube fitted with inclined vortex rings
Applied Thermal Engineering, 2014Co-Authors: Pongjet Promvonge, Narin Koolnapadol, Monsak Pimsarn, Chinaruk ThianpongAbstract:Abstract The influence of inclined vortex rings (VR) on Heat transfer augmentation in a uniform Heat-fluxed Tube has been investigated experimentally. In the present work, the 30° inclined VRs were mounted repeatedly in the Tube with various geometry parameters of the VR, three relative ring width ratios (BR = b/D = 0.1, 0.15 and 0.2) and four relative ring pitch ratios (PR = P/D = 0.5, 1.0, 1.5 and 2.0). Air was employed as the test fluid in the Tube for the Reynolds number from 5000 to 26,000. The aim at using the VRs is to create counter-rotating vortices inside the Tube to help increase the turbulence intensity as well as to convey the colder fluid from the core regime to the Heated-wall region. To find an optimum thermal performance condition, the effect of BR and PR values on the Heat transfer and pressure loss in the Tube is examined. The experimental results show a significant effect of the presence of the VRs on the Heat transfer and pressure loss over the smooth Tube. The larger BR value provides higher Heat transfer and pressure loss than the smaller one while the PR gives an opposite trend. However, the VR at BR = 0.1 and PR = 0.5 yields the best thermal performance.
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effect of perforated twisted tapes with parallel wings on Heat tansfer enhancement in a Heat Exchanger Tube
Energy Procedia, 2012Co-Authors: Chinaruk Thianpong, Pongjet Promvonge, Petpices Eiamsaard, Smith EiamsaardAbstract:Abstract This article reports an experimental investigation on Heat transfer and pressure drop characteristics of turbulent flow n a Heating Tube equipped with perforated twisted tapes with parallel wings (PTT) for Reynolds number between 500 and 20500. The design of PTT involves the following concepts: (1) wings induce an extra turbulence near Tube all and thus efficiently disrupt a thermal boundary layer (2) holes existing along a core Tube, diminish pressure losswithin the Tube. The parameters investigated were the hole diameter ratio (d/W = 0.11, 0.33 and 0.55) and wing depthratio (w/W = 0.11, 0.22 and 0.33). A typical twisted tape was also tested for an assessment. Compared to the plain ube, the Tubes with PTT and TT yielded Heat transfer enhancement up to 208% and 190%, respectively. The valuation of overall performance under the same pumping power reveal that the PTT with d/W = 0.11 and w/W = .33, gave the maximum thermal performance factor of 1.32, at Reynolds number of 5500. Empirical correlations of he Heat transfer, friction factor and thermal performance for Tubes with PTTs were also developed. In addition, the wirling/axial flow patterns of Tube with PTT were visualized using dye injection technique.
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thermal characteristics in a Heat Exchanger Tube fitted with dual twisted tape elements in tandem
International Communications in Heat and Mass Transfer, 2010Co-Authors: Smith Eiamsaard, Chinaruk Thianpong, Petpices Eiamsaard, Pongjet PromvongeAbstract:Abstract The paper presents a comparative investigation of enhanced Heat transfer and pressure loss by insertion of single twisted tape, full-length dual and regularly-spaced dual twisted tapes as swirl generators, in a round Tube under axially uniform wall Heat flux ( UHF ) conditions. The investigation encompassed the Reynolds number based on the inlet Tube diameter ( D ) ranging from 4000 to 19,000. The experiments are performed using single twisted tapes and full-length dual twisted tapes with three different twist ratios ( y / w = 3.0, 4.0 and 5.0) and also regularly-spaced dual twisted tapes with three different space ratios ( s / D = 0.75, 1.5 and 2.25). The effects of major parameters on Heat transfer and friction factor are discussed and the results from both single and dual twisted tape inserts are compared with those from the plain Tube. The result shows that the Heat transfer of the Tube with dual twisted tapes is higher than that of the plain Tube with/without single twisted tape insert. For both single twisted tape and full-length dual twisted tapes, Nusselt number ( Nu ) and friction factor ( f ) tend to increase with decreasing twist ratio ( y / w ). The average Nusselt number and friction factor in the Tube fitted with the full-length dual twisted tapes at y / w = 3.0, 4.0 and 5.0, are respectively 146%, 135% and 128%; and 2.56, 2.17 and 1.95 times of those in the plain Tube. For the regularly-spaced dual twisted tapes, the Heat transfer rate is decreased with increasing space ratio ( s / D ). The average Nusselt numbers in the Tube fitted with the regularly-spaced dual twisted tapes ( s / D ) of 0.75, 1.5 and 2.25 are respectively, 140%, 137% and 133% of that in the plain Tube. With the similar trend mentioned above, all dual twisted tapes with free spacing yield lower Heat transfer enhancement in comparison with the full-length dual twisted tapes ( s / D = 0.0).
M M K Bhuiya - One of the best experts on this subject based on the ideXlab platform.
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performance assessment in a Heat Exchanger Tube fitted with double counter twisted tape inserts
International Communications in Heat and Mass Transfer, 2014Co-Authors: M M K Bhuiya, A S M Sayem, M Islam, M S U Chowdhury, M ShahabuddinAbstract:The present study explored the effects of the double counter twisted tapes on Heat transfer and fluid friction characteristics in a Heat Exchanger Tube. The double counter twisted tapes were used as counter-swirl flow generators in the test section. The experiments were performed with double counter twisted tapes of four different twist ratios (y = 1.95, 3.85, 5.92 and 7.75) using air as the testing fluid in a circular Tube turbulent flow regime where the Reynolds number was varied from 6950 to 50,050. The experimental results demonstrated that the Nusselt number, friction factor and thermal enhancement efficiency were increased with decreasing twist ratio. The results also revealed that the Heat transfer rate in the Tube fitted with double counter twisted tape was significantly increased with corresponding increase in pressure drop. In the range of the present work, Heat transfer rate and friction factor were obtained to be around 60 to 240% and 91 to 286% higher than those of the plain Tube values, respectively. The maximum thermal enhancement efficiency of 1.34 was achieved by the use of double counter twisted tapes at constant blower power. In addition, the empirical correlations for the Nusselt number, friction factor and thermal enhancement efficiency were also developed, based on the experimental data.
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thermal characteristics in a Heat Exchanger Tube fitted with triple twisted tape inserts
International Communications in Heat and Mass Transfer, 2013Co-Authors: M M K Bhuiya, M S U Chowdhury, M Shahabuddin, Manabendra Saha, L A MemonAbstract:Abstract In the present study, the influences of triple twisted tapes on Heat transfer rate, friction factor and thermal enhancement efficiency were experimentally investigated. The triple twisted tapes were used as swirl flow generators in the test section. The investigations were conducted using the mild steel triple twisted tapes with four different twist ratios ( y = 1.92, 2.88, 4.81 and 6.79) for Reynolds number ranging from 7200 to 50,200 under uniform Heat flux condition. The experimental results demonstrated that the Nusselt number, friction factor and thermal enhancement efficiency increased with decreasing twist ratio. The results indicated that the presence of triple twisted tapes led to a higher increase in the Heat transfer rate over the plain Tube. The Nusselt number and friction factor of using the triple twisted tape inserts were found to be increased up to 3.85 and 4.2 times when compared with the plain Tube, respectively. The Heat transfer performance was evaluated based on the constant blower power and the performance was achieved to be 1.44 by the use of triple twisted tape inserts. Finally, correlations were developed based on the data gathered during this work for predicting the Heat transfer, friction factor and thermal enhancement efficiency through a circular Tube fitted with triple twisted tape inserts in terms of twist ratio ( y ), Reynolds number (Re) and Prandtl number (Pr).
Suneet Singh - One of the best experts on this subject based on the ideXlab platform.
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evaluation of transient characteristics of medium temperature solar thermal systems utilizing thermal stratification
Applied Energy, 2018Co-Authors: Rudrodip Majumdar, Sandip K Saha, Suneet SinghAbstract:Abstract System level transient moving boundary models are interesting in the context of advanced control of the solar thermal systems. However, development of control-oriented Heat Exchanger models faces the key challenges that these models should remain both reasonably accurate and mathematically tractable. In this paper, dynamic moving boundary model is developed for the medium temperature (∼200 °C) solar thermal power plant using a novel concept based on auxiliary pressurized water storage tank to enhance overall thermal efficiency, where the time varying pressure on the subcooled organic Rankine cycle working fluid (refrigerant) at the two-phase Heat Exchanger inlet is considered as the sole independent variable and all other thermodynamic variables are assumed to be dependent on the specified pressure. Modified idealized stratification model is adopted to analysis the thermal stratification in the storage tank. Small sinusoidal variation about the steady-state pressure level is considered to investigate its effect on the Heat Exchanger Tube wall temperature and the length of different flow regimes. Additionally, the model incorporates a provision to capture the effect of transient changes in the bulk temperature of the Heat transfer fluid (commercial thermic oil) on the moving phase change boundaries in the working fluid side of the Heat Exchanger. At an indicative solar radiation level of 450 W/m2, the primary energy transfer at the solar collector is found to be enhanced by about 11% by using an auxiliary pressurized water storage tank, compared to the case where commercial thermic oil is used in the collector loop. The overall thermal efficiency of the solar thermal system for a peak power level of 840 kWt is estimated as 20.75%.
