scholarly journals Effect of Reynolds Number and Property Variation on Fluid Flow and Heat Transfer in the Entrance Region of a Turbine Blade Internal-Cooling Channel

2005 ◽  
Vol 2005 (1) ◽  
pp. 36-44 ◽  
Author(s):  
R. Ben-Mansour ◽  
L. Al-Hadhrami
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mass Flow Rate ◽  
Heat Transfer Rate ◽  
Turbine Blade ◽  
Flow Rate ◽  
Transfer Rate ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Flow And Heat Transfer

Internal cooling is one of the effective techniques to cool turbine blades from inside. This internal cooling is achieved by pumping a relatively cold fluid through the internal-cooling channels. These channels are fed through short channels placed at the root of the turbine blade, usually called entrance region channels. The entrance region at the root of the turbine blade usually has a different geometry than the internal-cooling channel of the blade. This study investigates numerically the fluid flow and heat transfer in one-pass smooth isothermally heated channel using the RNGk−εmodel. The effect of Reynolds number on the flow and heat transfer characteristics has been studied for two mass flow rate ratios (1/1and1/2) for the same cooling channel. The Reynolds number was varied between10 000and50 000. The study has shown that the cooling channel goes through hydrodynamic and thermal development which necessitates a detailed flow and heat transfer study to evaluate the pressure drop and heat transfer rates. For the case of unbalanced mass flow rate ratio, a maximum difference of8.9% in the heat transfer rate between the top and bottom surfaces occurs atRe=10 000while the total heat transfer rate from both surfaces is the same for the balanced mass flow rate case. The effect of temperature-dependent property variation showed a small change in the heat transfer rates when all properties were allowed to vary with temperature. However, individual effects can be significant such as the effect of density variation, which resulted in as much as9.6% reduction in the heat transfer rate.

scholarly journals Heat Transfer by Natural Convection through V-Corrugated Plates

1970 ◽  
Vol 36 ◽  
pp. 1-5
Author(s):  
Mohammad Ali ◽  
M Hasanuzzaman
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Mass Flow Rate ◽  
Heat Transfer Rate ◽  
Flow Rate ◽  
Transfer Rate ◽  
Inlet Temperature ◽  
Cold Plate ◽  
Plate Temperature ◽  
Square Enclosure

An experimental investigation is performed on natural convection heat transfer through a square enclosure of V-corrugated vertical plates. The objective of this investigation is to study the variation of heat transfer rate through the square enclosure with the variation of both hot and cold plate temperatures. Hot plate temperature is varied by heat input. To vary cold plate temperature two parameters are considered: one is mass flow rate of water used to remove heat from cold plate and the other is the inlet temperature of water. Air is the media to transfer heat from the hot V-corrugated plate to cold V-corrugated plate. The result shows that the increase of mass flow rate increases the heat transfer rate and the decrease of water inlet temperature increases the heat transfer rate.Journal of Mechanical Engineering Vol.36 Dec. 2006 pp.1-5DOI = 10.3329/jme.v36i0.804

scholarly journals A Study on the Heat Transfer Rate Performance of the Hot Water Circulating in the Tubes in the Hot Water Panels Laid in the Walls and Floor of a Small Leisure Cabin in Relation to Changes in the Temperature and Flow Rate of the Hot Water

2021 ◽  
Vol 58 (1) ◽  
pp. 3468-3476
Author(s):  
Dong-Hyun Cho
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Heat Transfer Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Energy ◽  
Transfer Rate ◽  
Hot Water ◽  
Radiant Heat Transfer ◽  
Rate Performance

In this study, hot water panels were laid in the three walls as well as the floor of a small leisure cabin to implement radiant heating with the heat supplied by the hot water circulating inside the hot water tubes in the hot water panels. As a result of the study as such, compared to the forced convection heating at the current technology level in which air is forced to circulate by the air conditioner, the radiant heat transfer by the hot water panels laid in the floor and walls of the small leisure cabin in this study implemented more comfortable heating and wellbeing heating beneficial to health because it implemented heating without any movement or circulation of air. In addition, this study investigated heater accessories suitable for small leisure cabins not larger than 6 m2 to significantly reduce thermal energy and manufacturing costs. The thermal energy lost by hot water per unit time and the thermal energy obtained by air inside the small leisure cabin per unit time coincided well at the accuracy of ±5%. Therefore, the reliability of the result of the heat transfer rate accuracy experiment in this study was secured. As the mass flow rate of the hot water increased, the heat transfer rate performance of the small leisure cabin improved. In addition, as the mass flow rate of hot water increased, the heat transfer rate performance of the small leisure cabin improved linearly.

The Effect of Reynolds and Prandtl Number on Flow inside of Plan Channel of Waved Bottom Wall under Mixed Convection

2018 ◽  
Vol 16 ◽  
pp. 21-29
Author(s):  
Houssem Laidoudi ◽  
Mohamed Bouzit
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Bottom Wall ◽  
Governing Equations ◽  
Flow And Heat Transfer ◽  
Ansys Cfx ◽  
Commercial Code ◽  
Reynolds Number Increase

2D simulations of incompressible fluid in plan channel of waved bottom wall is carried out in this paper to understand and to determine correctly the effects of the Reynolds, Prandtl and Richardson numbers on the fluid flow and heat transfer of waved channel wall. The governing equations involving continuity, momentum and energy are solved numerically based on commercial code which called ANSYS-CFX. The results are presented and discussed for the range of following conditions as:Re= 60 to 250,Pr= 0.7 to 30,Ri= 0 to 1 at fixed value of blockage ratio. The numerical results showed that increase in Richardson number and/ or Prantl number For Reynolds number limited between 60 and 200 increases tightly the heat transfer rate. For the value 250 of Reynolds number increase in the buoyancy strength reduces the value of heat transfer rate.

The Flow and Mixed Convection around Tandem Circular Cylinders at Low Reynolds Number

2017 ◽  
Vol 378 ◽  
pp. 59-67
Author(s):  
Houssem Laidoudi ◽  
Blissag Bilal ◽  
Mohamed Bouzit
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mixed Convection ◽  
Drag Coefficient ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Richardson Number ◽  
Circular Cylinders ◽  
Thermal Buoyancy ◽  
Flow And Heat Transfer

A numerical investigation is carried out to understand the effects of thermal buoyancy and Reynolds number on flow characteristics and mixed convection heat transfer over three isothermal circular cylinders situated in a tandem arrangement within a horizontal channel. The distance between cylinders is fixed at the value of 2.5 widths of the cylinder. The obtained results are presented and discussed for the range of conditions as: Re = 5 to 40, Ri = 0 to 2 at fixed Pr number of 1 and blockage ratio β = 0.25. The main results are depicted in terms of streamlines and isotherm contours to analyze the effect of thermal buoyancy on fluid flow and heat transfer rate. Moreover, the overall drag coefficient and Nusselt number are computed to elucidate the role of Reynolds number and Richardson number on the flow and heat transfer. It is found that increase in the Richardson number increases the drag coefficient of the upstream cylinder whereas it decreases the heat transfer rate of this cylinder. The superimposed of thermal buoyancy created a new sort of recirculation zones between the tandem cylinders.

The Effect of Side Wall Mass Extraction on Pressure Loss and Heat Transfer of a Ribbed Rectangular Two-Pass Internal Cooling Channel

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
Marco Schüler ◽  
Frank Zehnder ◽  
Bernhard Weigand ◽  
Jens von Wolfersdorf ◽  
Sven Olaf Neumann
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Loss ◽  
Side Wall ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Trailing Edge ◽  
Wall Mass

Gas turbine blades are often cooled by using combined internal and external cooling methods where for internal cooling purposes, usually, serpentine passages are applied. In order to optimize the design of these serpentine passages it is inevitable to know the influence of mass extraction due to film cooling holes, dust holes, or due to side walls for feeding successive cooling channels as for the trailing edge on the internal cooling performance. Therefore, the objective of the present study was to analyze the influence of side wall mass extraction on pressure loss and heat transfer distribution in a two-pass internal cooling channel representing a cooling scheme with flow towards the trailing edge. The investigated rectangular two-pass channel consisted of an inlet and outlet duct with a height-to-width ratio of H/W=2 connected by a 180 deg sharp bend. The tip-to-web distance was kept constant at Wel/W=1. The mass extraction was realized using several circular holes in the outlet pass side wall. Two geometric configurations were investigated: A configuration with mass extraction solely in the outlet pass and a configuration with mass extraction in the bend region and outlet pass. The extracted mass flow rate was 0%, 10%, and 20% of the inlet channel mass flow. Spatially resolved heat transfer distributions were obtained using the transient thermochromic liquid crystal technique. Pressure losses were determined in separate experiments by local static pressure measurements. Furthermore, a computational study was performed solving the Reynolds-averaged Navier–Stokes equations using the commercial finite-volume solver FLUENT. The numerical grids were generated using the hybrid grid generator CENTAUR. Three different turbulence models were considered: the realizable k-ε model with two-layer wall treatment, the k-ω-SST model, and the v2-f model. The experimental data of the investigation of side wall ejection showed that the heat transfer in the bend region slightly increased when the ejection were in operation, while the heat transfer in the section of the outlet channel with side wall ejection was nearly not affected. After this section, a decrease in heat transfer was observed, which can be attributed to the decreased mainstream mass flow rate.

The Effect of Side Wall Mass Extraction on Pressure Loss and Heat Transfer of a Ribbed Rectangular Two-Pass Internal Cooling Channel

2009 ◽  
Author(s):  
Marco Schu¨ler ◽  
Frank Zehnder ◽  
Bernhard Weigand ◽  
Jens von Wolfersdorf ◽  
Sven Olaf Neumann
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Loss ◽  
Side Wall ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Trailing Edge ◽  
Wall Mass

Gas turbine blades are often cooled by using combined internal and external cooling methods, where for internal cooling purposes usually serpentine passages are applied. In order to optimize the design of these serpentine passages it is inevitable to know the influence of mass extraction due to film cooling holes, dust holes or due to side walls for feeding successive cooling channels as for the trailing edge on the internal cooling performance. Therefore, the objective of the present study was to analyse the influence of side wall mass extraction on pressure loss and heat transfer distribution in a two-pass internal cooling channel representing a cooling scheme with flow towards the trailing edge. The investigated rectangular two-pass channel consisted of an inlet and outlet duct with a height-to-width ratio of H/W = 2 connected by a 180° sharp bend. The tip-to-web distance was kept constant at Wel/W = 1. The mass extraction was realized using several circular holes in the outlet pass side wall. Two geometric configurations were investigated: A configuration with mass extraction solely in the outlet pass, and a configuration with mass extraction in the bend region and outlet pass. The extracted mass flow rate was 0%, 10%, and 20% of the inlet channel mass flow. Spatially resolved heat transfer distributions were obtained using the transient thermochromic liquid crystal technique. Pressure losses were determined in separate experiments by local static pressure measurements. Furthermore, a computational study was performed solving the Reynolds-Averaged Navier-Stokes equations (RANS method) using the commercial Finite-Volume solver FLUENT. The numerical grids were generated using the hybrid grid generator CENTAUR. Three different turbulence models were considered: the realizable k-ε model with two-layer wall treatment, the k-ω-SST model, and the v2-f model. The experimental data of the investigation of side wall ejection showed that the heat transfer in the bend region slightly increased when the ejection was in operation, while the heat transfer in the section of the outlet channel with side wall ejection was nearly not affected. After this section a decrease in heat transfer was observed which can be attributed to the decreased mainstream mass flow rate.

scholarly journals CFD Analysis of Turbulent Heat Transfer Characteristics in Cubical Enclosure

2019 ◽  
Vol 9 (1) ◽  
pp. 6116-6120
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Turbulent Flow ◽  
Mass Flow Rate ◽  
Heat Transfer Rate ◽  
Flow Rate ◽  
Transfer Rate ◽  
Flow Behavior ◽  
Cubical Enclosure ◽  
Flow Case

In this paper we present the turbulent flow and convective heat transfer phenomena inside a cubical enclosure with an internal heat source. The enclosure is designed with an inlet and outlet vent and the heat source is mounted on the bottom wall. The turbulent flow is modeled by the computational fluid dynamics (CFD) approach using Lambremhorst k- ε turbulence model. A finite difference method is used to discretize the governing equations and an in- house CFD used is developed for simulating the turbulent characteristics . The parametric study is performed for the assisting and opposing flow character stics inside the enclosure by varying the Grashof (Gr) and Reynolds (Re) number in the range of 105 ≤ Gr ≤ 1010 and 102 ≤ Re ≤ 106. The present study emphasises that the inertial force and buoyancy force has significant impact on the recirculation flow p attern inside the enclosure . The heat transfer rate is drastically influenced by the assisting and opppsing flow behavior developed inside the enclosure. It is observed that the mass flow rate across the outlet vent increases linearly with the Reynolds nu mber. The flow behavior is highly chaotic with the development of instabilities inside the enclosure . The streamlines and temperature distribution patterns inside the enclosure indicated that the assisting flow enhanced the heat transfer rate by 48% while the opposing flow suppressed the heat transfer rate by 45% inside the enclosure. A multi recirculating convective cell pattern is formed at higher Grashof number and the size of the cell increases with increase in Grashof number . It is also found that the mass flow rate across the outlet vent increases linearly for assisting flow case while it decreases for the opposing flow case. It is evident from the present study that the assisting flow case is best suited for heat transfer enchancement in cubical enclosure.

Thermal Performance Assessment of Turbulent Flow Through Dimpled Tubes

2010 ◽  
Author(s):  
Pornchai Nivesrangsan ◽  
Somsak Pethkool ◽  
Kwanchai Nanan ◽  
Monsak Pimsarn ◽  
Smith Eiamsa-ard
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Heat Transfer Rate ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Staggered Arrangement ◽  
Plain Tube ◽  
Pitch Ratio ◽  
Surface Patterns

This paper presents the heat transfer augmentation and friction factor characteristics by means of dimpled tubes. The experiments were conducted using the dimpled tubes with two different dimpled-surface patterns including aligned arrangement (A-A) and staggered arrangement (S-A), each with two pitch ratios (PR = p/Di = 0.6 and 1.0), for Reynolds number ranging from 9800 to 67,000. The experimental results achieved from the dimpled tubes are compared with those obtained from the plain tube. Evidently, the dimpled tubes with both arrangements offer higher heat transfer rates compared to the plain tube and the dimpled tube with staggered arrangement shows an advantage on the basis of heat transfer enhancement over the dimpled tube with aligned arrangement. The increase in heat transfer rate with reducing pitch ratio is due to the higher turbulent intensity imparted to the flow between the dimple surfaces. The mean heat transfer rate offered by the dimpled tube with staggered arrangement (S-A) at the lowest pitch ratio (PR = 0.6), is higher than those provided by the plain tube and the dimpled tube with aligned arrangement (A-A) at the same PR by around 127% and 8%, respectively. The empirical correlations developed in terms of pitch ratio (PR), Prandtl number (Pr) and Reynolds number, are fitted the experimental data within ±8% and ±2% for Nusselt number (Nu) and friction factor (f), respectively. In addition, the thermal performance factors under an equal pumping power constraint of the dimple tubes for both dimpled-surface arrangements are also determined.

Sign in / Sign up

Export Citation Format

Share Document