Heat Transfer and Pressure Drop for Short Pin-Fin Arrays With Pin-Endwall Fillet

1990 ◽  
Vol 112 (4) ◽  
pp. 926-932 ◽  
Author(s):  
M. K. Chyu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Circular Cylinders ◽  
Significant Finding ◽  
Array Configuration ◽  
Pin Fin ◽  
Pin Fin Arrays

The effects of array configuration and pin-endwall fillet on the heat transfer and pressure drop of short pin-fin arrays are investigated experimentally. The pin-fin element with endwall fillet, typical in actual turbine cooling applications, is modeled by a spool-like cylinder. The arrays studied include an in-line and a staggered array, each having seven rows of five pins. These arrays have the same geometric parameters, i.e., H/D = 1, S/D = X/D = 2.5, and the Reynolds number ranging from 5 × 103 to 3 × 104. One of the present results shows that the staggered array always has a higher array-averaged heat transfer coefficient than its in-line counterpart. However, the pressure drop for the staggered array is higher compared to the in-line configuration. These trends are unaffected by the existence of the pin-endwall fillet. Another significant finding is that an array with pin-endwall fillet generally produces lower heat transfer coefficient and higher pressure drop than that without endwall fillet. This leads to the conclusion that pin-endwall fillet is undesirable for heat transfer augmentation. In addition, nai¨ve use of the heat transfer results obtained with perfectly circular cylinders tends to overestimate the pin-fin cooling capability in the actual turbine. The effects of endwall fillet on the array heat transfer and pressure drop are much more pronounced for the staggered array than for the inline array; however, they diminish as the Reynolds number increases.

scholarly journals Heat Transfer and Pressure Drop for Short Pin-Fin Arrays With Pin-Endwall Fillet

1989 ◽  
Author(s):  
M. K. Chyu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Circular Cylinders ◽  
Significant Finding ◽  
Turbine Cooling ◽  
Array Configuration ◽  
Pin Fin ◽  
Pin Fin Arrays

The effects of array configuration and pin-endwall fillet on the heat transfer and pressure drop of short pin-fin arrays are investigated experimentally. The pin-fin element with endwall-fillet, typical in actual turbine cooling applications is modeled by a spool-like cylinder. The arrays studied include an in-line and a staggered array, each having 7 rows of 5 pins. These arrays have the same geometric parameters, i.e. H/D = 1, S/D = X/D = 2.5, and the Reynolds number ranging from 5 × 103 to 3 × 10. One of the present results shows that the staggered array always has a higher array-averaged mass transfer coefficient than its in-line counterpart. However, the pressure drop for the staggered array is higher compared to the in-line configuration. These trends are unaffected by the existence of the pin-endwall fillet. Another significant finding is that an array with pin-endwall fillet generally produces lower heat transfer coefficient and higher pressure drop than that without endwall-fillet. This leads to the conclusion that pin-endwall fillet is undesirable for heat transfer augmentation. In addition, naive use of the heat transfer results obtained with perfectly circular cylinders tends to overestimate the pin-fin cooling capability in the actual turbine. The effects of endwall-fillet on the array heat transfer and pressure drop are much more pronounced for the staggered array than for the in-line array; however, they diminish as the Reynolds number increases.

Heat Transfer of Pico Projector Using a Piezoelectric Fan With an Aluminum Blade

2017 ◽  
Author(s):  
Jin-Cherng Shyu ◽  
Shu-Kai Jheng
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Pin Fin ◽  
Specific Frequency ◽  
Tip Velocity ◽  
Pin Fin Array ◽  
The Heat Transfer Coefficient

A 120 mm × 53 mm × 19 mm horizontally-oriented pico projector in which both a pin-fin array and a piezoelectric fan were installed was tested to measure the thermal resistance at various heating powers. The operating frequency of the 40 mm × 10 mm aluminum piezoelectric fan ranged from 242 Hz to 257 Hz. The heat transfer coefficient of the pin-fin array was also estimated based on a thermal resistance network of the pico projector. The results showed that the thermal resistance of the pico projector which had a piezoelectric fan vibrating at a specific frequency would not monotonically reduce as the heating power increased. The heat transfer coefficient of the 1.5-mm-wide pin-fin array was higher than that of the 2.0-mm-wide pin-fin array at a given fan tip velocity ranging from 0.26 m/s to 0.76 m/s. The highest heat transfer coefficient of the 1.5-mm-wide pin-fin array reached approximately 21 W/m2K, while the highest heat transfer coefficient of the 2.0-mm-wide pin-fin array was approximately 16 W/m2K. A correlation between Nusselt number of the pin-fin array and Reynolds number was also developed in this study in a form of Nu = 0.3526Re0.1774.

scholarly journals CFD Analysis on the Air-Side Thermal-Hydraulic Performance of Multi-Louvered Fin Heat Exchangers at Low Reynolds Numbers

2017 ◽  
Author(s):  
Arslan Saleem ◽  
Man-Hoe Kim
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Reynolds Numbers ◽  
Hydraulic Performance

The air side thermal hydraulic performance of multi-louvered aluminium fin heat exchangers is investigated. A detailed study was performed to analyse the thermal performance of air over a wide range of Reynolds number i.e. from 30 to 250. Air-side heat transfer coefficient and air pressure drop were calculated and validated over the mentioned band of Reynolds numbers. Critical Reynolds number was determined numerically and the variation in flow physics along with the thermal and hydraulic performance of microchannel heat exchanger associated with R_cri has been reported. Moreover, a parametric study of the multi-louvered aluminium fin heat exchangers was also performed for 36 heat exchanger configurations with the louver angles (19-31°), fin pitches (1.0, 1.2, 1.4 mm) and flow depths (16, 20, 24 mm); and the geometric configuration exhibiting the highest thermal performance was reported. The air-side heat transfer coefficient and pressure drop results for different geometrical configurations were presented in terms of Colburn j factor and Fanning friction factor f, as a function of Reynolds number based on louver pitch.

scholarly journals Investigation on Heat Transfer and Pressure Drop Performance Utilizing GNP-based Colloidal Suspension Flow in Finned Conduit

2021 ◽  
Vol 945 (1) ◽  
pp. 012056
Author(s):  
Yanru Wang ◽  
Cheen Sean Oon ◽  
Manh-Vu Tran ◽  
Joshua Yap Kee An
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Colloidal Suspension ◽  
Convective Heat Transfer Coefficient ◽  
Constant Heat Flux

Abstract Heat exchangers have been widely used in various engineering applications. It is important to develop a highly efficient heat transfer equipment to reduce carbon footprint. In the current research, the effect of 0.025wt% CGNP/water nanofluid on convective heat transfer and pressure drop performance is investigated numerically in finned conduits with circular and square geometry. ANSYS FLUENT is used to analyze the turbulent flow inside the conduits with Reynolds number ranging from 7360 to 28011 and constant heat flux 12254.90W/m2 and 9615.38W/m2 in circular and square geometry, respectively. Only 1/8 of the pipe was constructed in the simulation as the geometry is symmetrical. The numbers of mesh elements are 465488 and 469144 for circular and square conduits. SST k-omega viscous model, SIMPLEC scheme and second-order upwind solvers are used in this model, where SST k-omega viscous model is good at solving turbulence parameters in the near wall boundary regions. It is found that the use of CGNP/water nanofluid can increase convective heat transfer coefficient without increasing pressure drop compared with water. Besides, the circular pipe shows higher heat transfer enhancement compared with square pipe. Furthermore, the increase in Reynolds number enhances the Nusselt number and heat transfer coefficient in both circular and square geometries. It is recommended that circular finned pipe and CGNP/water colloidal suspension could be applied in low turbulence flow setting heat exchanger.

Experimental and Theoretical Research of the Shell Side Heat Transfer Coefficient and Pressure Drop in a Plastic Shell and Tube Heat Exchanger

2011 ◽  
Vol 312-315 ◽  
pp. 187-192
Author(s):  
Rita Aguilar Osorio ◽  
K. Cliffle
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Plastic Shell ◽  
Shell Side ◽  
Tube Heat Exchanger ◽  
Shell And Tube ◽  
Experimental Rig

The aim of this work is to present an experimental research of the shell side heat transfer coefficient and pressure drop in a plastic shell and tube heat exchanger with single segmental baffle. The tube bundle consisted of 110 U-tubes constructed of high-density polyethylene, the inside diameter was 9.2 mm, the tube pitch was 1.5 the out side diameter. The shell was constructed of polypropylene with a diameter of 315 mm. Shell side heat transfer coefficients and pressure drop were determined varying the flow rates. An experimental rig for the experimental research was designed and constructed. The overall experimental rig consisted of two operation cycles. The two fluids used in this system were hot and cold water. The experimental results were compared with theoretical predictions using the Bell-Taborek and Wills and Johnston Methods. The heat transfer coefficient predictions, for Reynolds number greater than 780, showed that the Bell-Taborek and Wills-Johnston methods are in general agreement with the experimental data with only 5% difference, Wills-Johnston overpredicts it and Bell underpredicts it, except at the lower Reynolds number than 780 where there was an average underprediction of 15%. The pressure drop predictions by Wills-Johnston and Bell-Taborek methods were generally acceptable including the inlet and outlet nozzles with the highest experimental data (Reynolds number greater than 780) within a 15% overprediction, however, at the lower data the pressure drop was overpredicted up to 2 times the measured values.

scholarly journals Non-Isothermal Hydrodynamic Characteristics of a Nanofluid in a Fin-Attached Rotating Tube Bundle

Mathematics ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1153
Author(s):  
Mashhour A. Alazwari ◽  
Mohammad Reza Safaei
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Rotation Speed ◽  
Tube Bundle ◽  
Heat Transfer Fluid ◽  
Hydrodynamic Characteristics ◽  
The Heat Transfer Coefficient

In the present study, a novel configuration of a rotating tube bundle was simulated under non-isothermal hydrodynamic conditions using a mixture model. Eight fins were considered in this study, which targeted the hydrodynamics of the system. An aqueous copper nanofluid was used as the heat transfer fluid. Various operating factors, such as rotation speed (up to 500 rad/s), Reynolds number (10–80), and concentration of the nanofluid (0.0–4.0%) were applied, and the performance of the microchannel heat exchanger was assessed. It was found that the heat transfer coefficient of the system could be enhanced by increasing the Reynolds number, the concentration of the nanofluid, and the rotation speed. The maximum enhancement in the heat transfer coefficient (HTC) was 258% after adding a 4% volumetric nanoparticle concentration to the base fluid and increasing Re from 10 to 80 and ω from 0 to 500 rad/s. Furthermore, at Re = 80 and ω = 500 rad/s, the HTC values measured for the nanofluid were 42.3% higher than those calculated for water, showing the nanoparticles' positive impact on the heat transfer paradigm. Moreover, it was identified that copper nanoparticles' presence had no significant effect on the system's pressure drop. This was attributed to the interaction of the fluid flow and circulated flow around the tubes. Finally, the heat transfer coefficient and pressure drop had no considerable changes when augmenting the rotation speed at high Reynolds numbers.

scholarly journals Heat Transfer in Hairpin Heat Exchanger using Magnetite/Water Nanofluid

2019 ◽  
Vol 8 (4) ◽  
pp. 7163-7166
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Magnetite Nanoparticles ◽  
Pure Water ◽  
Number Range ◽  
Heat Transfer Augmentation

The present work deals with heat transfer augmentation in a Hair-Pin heat exchanger using magnetite/water nanofluid at volume concentrations of 0.004%, 0.006% and 0.008% under turbulent flow, the effect of different concentration of magnetite nanoparticles are added in pure water as basefluid on heat transfer coefficient and pressure drop in a hair-pin heat exchanger for counteract flow arrangement are investigated. The magnetite/water nanofluid is flowing through the inner tube and Reynolds number considered is in the range of 16000 to 30000. The results showed that there is 25-33% enhancement in heat transfer coefficient at 0.008% to the water at Reynolds number range of 16000 to 30000.

Heat Transfer and Pressure Drop Characteristics of an Assembly of Partially Segmented Plates

1989 ◽  
Vol 111 (1) ◽  
pp. 44-50 ◽  
Author(s):  
Y. N. Lee
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Width Ratio ◽  
Total Width ◽  
The Heat Transfer Coefficient ◽  
Transfer Models

The heat transfer and pressure drop characteristics of an assembly of plates in a rectangular duct, with part of each plate segmented transversely and the segments inclined at 25 deg to the flow, have been investigated experimentally in the range of Reynolds numbers between 900 and 4000. The segmented-to-total width ratios β were 0.81 and 0.61. Mass transfer measurements of naphthalene were made to obtain the heat transfer coefficient. A new spray technique is described for preparing the mass transfer models, which are so complex that previously reported techniques cannot be applied. The mass transfer models simulate louvered fin surfaces used currently in industries. The heat transfer coefficient is found to be a strong function of the segmented-to-total plate width ratio β, and it decreases as β decreases. The heat transfer coefficient of an existing louver fin heat exchanger whose geometries are in close proximity to one of the model configurations was compared with that of the model, and good agreement was obtained between the two. The pressure drop (through the plate assembly) measurements showed that the pressure drop is mainly due to inertia loss in the experimental range of the present work, and that the streamwise, per-row pressure drop coefficient Kp is a function of only β and independent of the Reynolds number NRe,Dh. It was found, for a fixed blower power, that there exists an optimum Reynolds number (NRe,Dh)opt for maximum Nusselt number at a given segmented-to-total width radio β. A similar trend is also found for a fixed pressure drop.

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