Negatively Buoyant Plume Flow in a Baffle

2008 ◽  
Author(s):  
S. K. S. Boetcher ◽  
F. A. Kulacki
Keyword(s):  
Heat Transfer ◽  
Transfer Rate ◽  
Two Dimensional ◽  
Buoyant Plume ◽  
Buoyant Flow ◽  
Transfer Rates ◽  
Offset Distance ◽  
Plume Flow ◽  
Negatively Buoyant ◽  
Surrounding Fluid

Transient two-dimensional negatively buoyant flow into a straight adiabatic baffle beneath an isothermal circular cylinder is numerically simulated. The surrounding fluid is considered infinite in extent and at constant temperature. Governing parameters are the baffle width and the offset of the entrance of the baffle beneath the center of the cylinder. Overall characteristics of the flow and entrainment of the surrounding fluid are found to be dependent on the baffle offset; however, the attachment length of the flow to the baffle wall is relatively insensitive to the offset. Heat transfer rates to the cylinder are calculated for various times for various baffle offsets. There is a weak dependence on baffle-offset distance with heat transfer rate.

Buoyant Flow and Heat Transfer in a Conducting Baffle

2008 ◽  
Author(s):  
S. K. S. Boetcher ◽  
F. A. Kulacki
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Quasi Steady State ◽  
Two Dimensional ◽  
Buoyant Flow ◽  
Transfer Rates ◽  
Flow And Heat Transfer ◽  
Rayleigh Numbers ◽  
Negatively Buoyant ◽  
Surrounding Fluid

A numerical simulation of transient two-dimensional negatively buoyant flow into a straight baffle situated below an isothermal circular cylinder is performed. Both an adiabatic and a highly conducting baffle are considered over a range of Rayleigh numbers, 106 < RaD < 107. During the quasi-steady-state period, the surrounding fluid is effectively considered infinite in extent and at constant temperature. It is found that in general, the conducting baffle is at a disadvantage in maintaining a short attachment length which is needed to optimally slow the flow to prevent mixing. Qualitative flow fields are shown and heat transfer rates to the cylinder are calculated at the quasi-steady state.

Negatively Buoyant Plume Flow in a Baffled Heat Exchanger

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Sandra K. S. Boetcher ◽  
F. A. Kulacki ◽  
Jane H. Davidson
Keyword(s):  
Heat Exchanger ◽  
Effective Width ◽  
Two Dimensional ◽  
Buoyant Plume ◽  
Fully Developed Flow ◽  
Buoyant Flow ◽  
Thermal Stores ◽  
Plume Flow ◽  
Rayleigh Numbers ◽  
Negatively Buoyant

A numerical simulation of transient two-dimensional negatively buoyant flow into a straight baffle situated below an isothermal circular cylinder in an initially isothermal enclosure is presented for both an adiabatic and a highly conducting baffle for Rayleigh numbers from 106 to 107. Results show the effects of baffle offset, width, and length on the point where viscous flow develops and on velocity profiles within the baffle. Results are interpreted to guide the design of straight baffles to reduce destruction of stratification in thermal stores using an immersed heat exchanger. The preferred geometry is a low-conductivity baffle of width equal to the effective width of the heat exchanger and 15 or more cylinder diameters in length to ensure nearly fully developed flow at the baffle outlet.

Design of a Plane-Type Bidirectional Thermal Diode

1988 ◽  
Vol 110 (4) ◽  
pp. 299-305 ◽  
Author(s):  
K. Chen
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Transfer Rate ◽  
Reverse Bias ◽  
Energy Utilization ◽  
Heat Transfer Analysis ◽  
Transfer Rates ◽  
One Dimensional ◽  
Plane Type ◽  
Solar Energy Utilization

The design of a plane-type, bidirectional thermal diode is presented. This diode is composed of two vertical plates and several fluid-filled loops with their horizontal segments soldered to the vertical plates. This invention is simple in construction and low in cost. The direction of heat transfer in the invented thermal diode can be easily reversed. These features of the present invention make it very attractive to solar energy utilization. Natural convection analysis for thermosyphon operations was adopted for heat transfer calculations of the fluid-filled loops. A one-dimensional heat transfer analysis was employed to estimate the heat transfer rate and ratio of heat transfer rates of the diode under forward and reverse bias.

An Analytical Study of Heat Transfer in Finite Tissue With Two Blood Vessels and Uniform Dirichlet Boundary Conditions

2005 ◽  
Vol 127 (2) ◽  
pp. 179-188 ◽  
Author(s):  
Devashish Shrivastava ◽  
Benjamin McKay ◽  
Robert B. Roemer
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Source Term ◽  
Dirichlet Boundary ◽  
Total Heat ◽  
Dirichlet Boundary Conditions ◽  
Total Heat Transfer ◽  
Transfer Rates

Counter-current (vessel–vessel) heat transfer has been postulated as one of the most important heat transfer mechanisms in living systems. Surprisingly, however, the accurate quantification of the vessel–vessel, and vessel–tissue, heat transfer rates has never been performed in the most general and important case of a finite, unheated/heated tissue domain with noninsulated boundary conditions. To quantify these heat transfer rates, an exact analytical expression for the temperature field is derived by solving the 2-D Poisson equation with uniform Dirichlet boundary conditions. The new results obtained using this solution are as follows: first, the vessel–vessel heat transfer rate can be a large fraction of the total heat transfer rate of each vessel, thus quantitatively demonstrating the need to accurately model the vessel–vessel heat transfer for vessels imbedded in tissues. Second, the vessel–vessel heat transfer rate is shown to be independent of the source term; while the heat transfer rates from the vessels to the tissue show a significant dependence on the source term. Third, while many previous studies have assumed that (1) the total heat transfer rate from vessels to tissue is zero, and/or (2) the heat transfer rates from paired vessels (of different sizes and at different temperatures) to tissue are equal to each other the current analysis shows that neither of these conditions is met. The analytical solution approach used to solve this two vessels problem is general and can be extended for the case of “N” arbitrarily located vessels.

Heat Transfer From an Isothermal Vertical Surface With Adjacent Heated Horizontal Louvers: Validation

2002 ◽  
Vol 124 (6) ◽  
pp. 1078-1087 ◽  
Author(s):  
M. Collins ◽  
S. J. Harrison ◽  
D. Naylor ◽  
P. H. Oosthuizen
Keyword(s):  
Heat Transfer ◽  
Transfer Rate ◽  
Numerical Study ◽  
Surface Flux ◽  
Element Model ◽  
Vertical Surface ◽  
Two Dimensional ◽  
Local Surface ◽  
Conjugate Conduction ◽  
Steady Laminar

The present study examines the influence of heated, horizontal, and rotateable louvers on the convective heat transfer from a heated or cooled vertical isothermal surface. The system represents an irradiated Venetian blind adjacent to the indoor surface of a window. Detailed temperature field and local surface flux data were obtained using a Mach-Zehnder Interferometer for two window temperatures (warm and cool compared to ambient) and irradiation levels, two louver to plate spacings, and three louver angles. The results have been compared to a steady, laminar, two-dimensional, conjugate conduction/convection/radiation finite element model of this problem. The effect of the heated louvers on the heat transfer rate from the plate surface has been demonstrated and the results of the numerical study have been validated.

scholarly journals Effect of Squealer Tip on Rotor Heat Transfer and Efficiency

1997 ◽  
Author(s):  
A. A. Ameri ◽  
E. Steinthorsson ◽  
David L. Rigby
Keyword(s):  
Heat Transfer ◽  
Transfer Rate ◽  
Flow Structures ◽  
Two Dimensional ◽  
Transfer Enhancement ◽  
Flow And Heat Transfer ◽  
Significant Difference ◽  
Blade Tip ◽  
Large Heat ◽  
Good Agreement

Calculations were performed to simulate the tip flow and heat transfer on the GE-E3 first stage turbine, which represents a modern gas turbine blade geometry. Cases considered were a smooth tip, 2% recess, and 3% recess. In addition a two-dimensional cavity problem was calculated. Good agreement with experimental results was obtained for the cavity calculations, demonstrating that the k-ω turbulence model used is capable of representing flows of the present type. In the rotor calculations, two dominant flow structures were shown to exist within the recess. Also areas of large heat transfer rate were identified on the blade tip and the mechanisms of heat transfer enhancement were discussed. No significant difference in adiabatic efficiency was observed for the three tip treatments investigated.

Heat Transfer Enhancement Using Shaped Polymer Tubes: Fin Analysis

2004 ◽  
Vol 126 (2) ◽  
pp. 211-218 ◽  
Author(s):  
Zhihua Li ◽  
Jane H. Davidson ◽  
Susan C. Mantell
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Transfer Rate ◽  
Polymeric Materials ◽  
Transfer Enhancement ◽  
Transfer Rates ◽  
Shaped Tube ◽  
Polymer Tubes

The use of polymer tubes for heat exchanger tube bundles is of interest in many applications where corrosion, mineral build-up and/or weight are important. The challenge of overcoming the low thermal conductivity of polymers may be met by using many small-diameter, thin-walled polymer tubes and this route is being pursued by industry. We propose the use of unique shaped tubes that are easily extruded using polymeric materials. The shaped tubes are streamlined to reduce form drag yet the inside flow passage is kept circular to maintain the pressure capability of the tube. Special treatment is required to predict convective heat transfer rates because the temperature distribution along the outer surface of the shaped tubes is nonuniform. The average forced convection Nusselt number correlations developed for these noncircular tubes can not be used directly to determine heat transfer rate. In this paper, heat transfer rates of shaped tubes are characterized by treating the tubes as a base circular tube to which longitudinal fin(s) are added. Numerical solution of an energy balance on the fin provides the surface temperature distribution and a shaped tube efficiency, which can be used in the same manner as a fin efficiency to determine the outside convective resistance. The approach is illustrated for three streamlined shapes with fins of lenticular and oval profile. The presentation highlights the effects of the geometry and the Biot number on the tube efficiency and heat transfer enhancement. Convective heat transfer is enhanced for the oval shaped tube for 2000⩽Re⩽20,000 when Bi<0.3. For polymeric materials, the Biot number in most applications will be greater than 0.3, and adding material to the base tube reduces the heat transfer rate. The potential benefit of reduced form drag remains.

Sign in / Sign up

Export Citation Format

Share Document