Cooling of a Multichip Electronic Module by Means of Confined Two-Dimensional Jets of Dielectric Liquid

1990 ◽  
Vol 112 (4) ◽  
pp. 891-898 ◽  
Author(s):  
D. C. Wadsworth ◽  
I. Mudawar
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer Coefficient ◽  
Channel Height ◽  
Heat Sources ◽  
Two Dimensional ◽  
Chip Surface ◽  
Rectangular Slot ◽  
Fluid Properties ◽  
Cooling Module ◽  
Heater Length

Experiments were performed to investigate single-phase heat transfer from a smooth 12.7 × 12.7 mm2 simulated chip to a two-dimensional jet of dielectric Fluorinert FC-72 liquid issuing from a thin rectangular slot into a channel confined between the chip surface and nozzle plate. The effects of jet width, confinement channel height, and impingement velocity have been examined. Channel height had a negligible effect on the heat transfer performance of the jet for the conditions of the present study. A correlation for the convective heat transfer coefficient is presented as a function of jet width, heater length, flow velocity, and fluid properties. A self-contained multichip cooling module consisting of a 3 × 3 array of heat sources confirmed the uniformity and predictability of cooling for each of the nine chips, and proved the cooling module is well suited for packaging large arrays of high-power density chips.

Natural Convection in Two-Dimensional Horizontal Channel With Heat Sources

2003 ◽  
Author(s):  
Tito Dias ◽  
Luiz Fernando Milanez
Keyword(s):  
Natural Convection ◽  
Flux Ratio ◽  
Horizontal Channel ◽  
Maximum Temperature ◽  
Computational Domain ◽  
Heat Sources ◽  
Two Dimensional ◽  
Temperature Excess ◽  
Fluid Properties ◽  
Laminar Natural Convection

Laminar natural convection in a two-dimensional horizontal channel is very important in laptop design, since optimizing the utilization of the cooler saves energy from the battery. In this work, this configuration has been numerically studied. Three cases were studied according to the position of the heat sources in the lower wall, upper wall and both. The computational domain consisted of two adiabatic walls where the heat sources were positioned, and two open boundaries, where the manometric pressure and normal gradient of velocity were zero. Ambient temperature was prescribed for the entering fluid and zero normal gradient for the exiting fluid. Fluid properties were assumed constant except for the density change with temperature on the buoyancy term. The influence of the modified Rayleigh number, position of the heat sources and heat flux ratio between the sources were analyzed for Prandtl number of 0.7. The maximum temperature excess on the heat source is lower for the case with two heat sources and Ra = 104. This preliminary study showed the existence of a minimum value of the excess temperature for the studies aspect ratio (0.1).

Effects of Protrusions on Conjugate Heat Transfer in a Microtube or Microchannel

2010 ◽  
Author(s):  
Muhammad M. Rahman ◽  
Phaninder Injeti
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Conjugate Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Sources ◽  
Two Dimensional ◽  
Discrete Heat Sources ◽  
Global Performance ◽  
Tube Geometry

Effects of protrusions on heat transfer in a microtube and in a two-dimensional microchannel of finite wall thickness were investigated for various shapes and sizes of the protrusion. Calculations were done for incompressible flow of a Newtonian fluid with developing momentum and thermal boundary layers under uniform and discrete heating conditions. It was found that the local Nusselt number near the protrusions changes significantly with the variations of Reynolds number, height, width, and distance between protrusions, and the distribution of discrete heat sources. The results presented in the paper demonstrate that protrusions can be used advantageously for the enhancement of local heat transfer whereas the global performance may be enhanced or diminished based on the tube geometry.

Liquid Immersion Cooling of a Longitudinal Array of Discrete Heat Sources in Protruding Substrates: I—Single-Phase Convection

1992 ◽  
Vol 114 (1) ◽  
pp. 55-62 ◽  
Author(s):  
T. J. Heindel ◽  
F. P. Incropera ◽  
S. Ramadhyani
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Channel Height ◽  
Heat Sources ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Discrete Heat Sources ◽  
Buoyancy Driven Flows

Experiments have been performed using water and FC-77 to investigate heat transfer from an in-line 1 x 10 array of discrete heat sources, flush mounted to protruding substrates located on the bottom wall of a horizontal flow channel. The data encompass flow regimes ranging from mixed convection to laminar and turbulent forced convection. Buoyancy-induced secondary flows enhanced heat transfer at downstream heater locations and provided heat transfer coefficients comparable to upstream values. Upstream heating extended enhancement on the downstream heaters to larger Reynolds numbers. Higher Prandtl number fluids also extended heat transfer enhancement to larger Reynolds numbers, while a reduction in channel height suppressed buoyancy driven flows, thereby reducing enhancement. The protrusions enhanced the transition to turbulent forced convection, causing the critical Reynolds number to decrease with increasing row number. The transition region was characterized by large heater-to-heater variations in the average Nusselt number.

A Model of the Fluid Convective Cooling in Grinding Process

2013 ◽  
Vol 797 ◽  
pp. 299-304 ◽  
Author(s):  
Lei Zhang ◽  
Michael N. Morgan
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Grinding Wheel ◽  
Process Conditions ◽  
Transfer Model ◽  
Grinding Process ◽  
Fluid Properties ◽  
Grinding Conditions

The grinding process has particular interest in that contact temperatures have great significance for quality and integrity of machined surfaces. Hardened surfaces may be damaged by softening and or being stressed, being hardened or re-hardened, burned or cracked. It is important in grinding for the fluid to remove heat from the grinding contact zone to avoid thermal damage to the workpiece surface and/or sub-surface layers. The cooling effect of grinding fluid can be quantified by the convective heat transfer coefficient (CHTC) acting in the grinding zone. This paper presents values of the CHTC based on measured grinding temperatures. The paper also presents a new convective heat transfer model based on principles of applied fluid dynamics and heat transfer. Predicted values for the CHTC calculated from the model are compared with results from experiment obtained under a range of grinding conditions and with experimental data. The results demonstrate that the new CHTC model improves the accuracy of prediction and helps explain the variation in the value of CHTC under varying process conditions. Results also show that convection efficiency strongly depends on the grinding wheel speed, grinding arc length and fluid properties.

Heat Transfer in a Laminar Boundary Layer with Constant Fluid Properties and Constant Wall Temperature

1958 ◽  
Vol 62 (565) ◽  
pp. 60-64 ◽  
Author(s):  
A. G. Smith ◽  
D. B. Spalding
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Laminar Flow ◽  
Laminar Boundary Layer ◽  
Wall Temperature ◽  
Two Dimensional ◽  
Constant Wall Temperature ◽  
Simple Method ◽  
Flow Surface ◽  
Fluid Properties

A simple method is given for the calculation of the heat transfer from a laminar flow surface. Computation is by a quadrature. The method is essentially a simplification and extension of the Eckert(1) method, and is applicable both to two–dimensional and to axisymmetric flows.

scholarly journals Entropy Generation Analysis of Natural Convection in Square Enclosures with Two Isoflux Heat Sources

2017 ◽  
Vol 7 (2) ◽  
pp. 1486-1495
Author(s):  
S. Z. Nejad ◽  
M. M. Keshtkar
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Local Heating ◽  
Heat Sinks ◽  
Temperature Fields ◽  
Entropy Generation Rate ◽  
Heat Sources ◽  
Minimum Entropy ◽  
Adiabatic Flow ◽  
Heater Length

This study investigates entropy generation resulting from natural convective heat transfer in square enclosures with local heating of the bottom and symmetrical cooling of the sidewalls. This analysis tends to optimize heat transfer of two pieces of semiconductor in a square electronic package. In this simulation, heaters are modeled as isoflux heat sources and sidewalls of the enclosure are isothermal heat sinks. The top wall and the non-heated portions of the bottom wall are adiabatic. Flow and temperature fields are obtained by numerical simulation of conservation equations of mass, momentum and energy in laminar, steady and two dimensional flows. With constant heat energy into the cavity, effect of Rayleigh number, heater length, heater strength ratios and heater position is evaluated on flow and temperature fields and local entropy generation. The results show that a minimum entropy generation rate is obtained under the same condition in which a minimum peak heater temperature is obtained.

Indirectly Measuring the Convective Heat Transfer Coefficient Utilizing Thermistors for Education and Research

2013 ◽  
Author(s):  
Chris J. Kobus
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Classical Method ◽  
Convective Heat Transfer Coefficient ◽  
Fundamental Parameters ◽  
Fluid Properties ◽  
Transfer Problems

A primary parameter of interest in many heat transfer problems is the convective heat transfer coefficient, which is dependent upon several fundamental parameters like fluid properties, velocity, temperature distribution, etc. As such, empirically determining this parameter can be complicated, especially in educational settings. The classical method includes many physical temperature sensors and heating pads distributed throughout a body that necessitates complex control schemes and data acquisition systems. This paper details a far simpler method of indirectly measuring the convective heat transfer coefficient by utilizing thermistors of various geometries. In calibrating these thermistors for their temperature-resistance characteristics, the convective heat transfer coefficient can be backed out without directly measuring the temperature of the thermistror itself, which has the effect of simplifying the experimental requirements to a large enough degree to make the technique suitable for introductory educational courses in heat transfer. In addition, the technique is also accurate enough to where the experimental data is worthy of publication in the archival literature.

Impact of Wall Temperature on Turbine Blade Tip Aero-Thermal Performance

2013 ◽  
Author(s):  
Q. Zhang ◽  
L. He
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Temperature Dependence ◽  
Turbine Blade ◽  
Wall Temperature ◽  
High Speed ◽  
Convective Heat Transfer Coefficient ◽  
Gas Temperature ◽  
Fluid Properties ◽  
Blade Tip

Currently, the aerodynamics and heat transfer over a turbine blade tip tend to be analyzed separately with the assumption that the wall thermal boundary conditions do not affect the Over-Tip-Leakage (OTL) flow field. There are some existing correlations for correcting the wall temperature effect on heat transfer. But they were mainly developed to account for the temperature dependence on fluid properties, and are inherently limited by the empirical nature. The questions arise with regard to: is the OTL aerodynamics significantly affected by the wall thermal condition? And if it is, how can we count this effect consistently in turbine blade tip design and analysis using modern CFD methods? In the present study, the problem has been examined for typical HP turbine blade tip configurations. An extensively developed RANS code (HYDRA) is employed and validated against the experimental data from a high speed linear cascade testing rig. The numerical analysis reveals that the wall-gas temperature ratio could greatly affect the transonic OTL flow field and there is a strong two-way coupling between aerodynamics and heat transfer. The feedbacks of the thermal boundary condition to aerodynamics behave differently at different flow regimes over the tip, clearly indicating a highly localized dependence of the convective heat transfer coefficient (HTC) upon wall temperatures. This implies that to use HTC for blade metal temperature predictions without resorting a fully conjugate solution, the temperature dependence needs to be corrected locally. A nonlinear correction approach has been adopted in the present work, and the results demonstrate its effectiveness for the transonic turbine tip configurations studied.

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