Impingement Cooling in a Simulated Data Center Servers With an Array of Elliptic Air Jets

2015 ◽  
Author(s):  
Sheng-Kai Chang ◽  
Lo Yuan-Hsiang ◽  
Yao-Hsien Liu
Keyword(s):  
Heat Transfer ◽  
Data Center ◽  
High Efficiency ◽  
Simulated Data ◽  
Target Surface ◽  
Transfer Coefficients ◽  
Cross Sectional ◽  
Impingement Cooling ◽  
Air Jets ◽  
High Heat Transfer

Reducing the electricity consumption from the cooling systems in a data center can cut the energy cost. The development of the high efficiency cooling schemes can effectively save more energy from the computer room air conditioning (CRAC) system. Impingement cooling with air jets can achieve high heat transfer rates and could be used to cool local hot spots in the cabinets. A 5 × 5 jet array was designed utilizing circular and elliptic holes. The cross sectional area of the test region was 250 mm × 25 mm. The jet Reynolds numbers is 3300. Heat transfer coefficients on the target surface were investigated. Results indicated that the impingement cooling provided lower surface temperature than the traditional fan cooling.

scholarly journals Investigations of Flow and Heat Transfer Characteristics in a Channel Impingement Cooling Configuration with a Single Row of Water Jets

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4327
Author(s):  
Min-Seob Shin ◽  
Santhosh Senguttuvan ◽  
Sung-Min Kim
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Channel Height ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Impingement Cooling ◽  
Average Heat ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

The present study experimentally and numerically investigates the effect of channel height on the flow and heat transfer characteristics of a channel impingement cooling configuration for various jet Reynolds numbers in the range of 2000–8600. A single array consisting of eleven jets with 0.8 mm diameter injects water into the channel with 2 mm width at four different channel heights (3, 4, 5, and 6 mm). The average heat transfer coefficients at the target surface are measured by maintaining a temperature difference between the jet exit and the target surface in the range of 15–17 °C for each channel height. The experimental results show the average heat transfer coefficient at the target surface increases with the jet Reynolds number and decreases with the channel height. An average Nusselt number correlation is developed based on 85 experimentally measured data points with a mean absolute error of less than 4.31%. The numerical simulation accurately predicts the overall heat transfer rate within 10% error. The numerical results are analyzed to investigate the flow structure and its effect on the local heat transfer characteristics. The present study advances the primary understanding of the flow and heat transfer characteristics of the channel impingement cooling configuration with liquid jets.

Effect of Acoustic Excitation on the Heat Transfer to an Impinging Air Jet

2007 ◽  
Author(s):  
Tadhg S. O’Donovan ◽  
Darina B. Murray
Keyword(s):  
Heat Transfer ◽  
Excitation Frequency ◽  
High Heat ◽  
Cooling Capacity ◽  
Mean Flow ◽  
Transfer Coefficients ◽  
Air Jets ◽  
Air Jet ◽  
High Heat Transfer ◽  
Impingement Surface

Impinging air jets are known as a method of achieving particularly high heat transfer coefficients and are employed in many applications including the cooling of electronics, manufacturing processes such as grinding, etc. The current investigation is concerned with acoustically exciting an impinging air jet to enhance its overall cooling capacity. Distributions of the heat transfer to an axially impinging air jet for a range of Reynolds numbers (Re) from 10000 to 30000, non-dimensional nozzle to impingement surface heights (H/D) from 0.5 to 2 and excitation frequencies (f) that range from 0.5 to 1 times the natural frequency of the jet are presented. For this low range of nozzle to impingement surface spacings it has been shown that the heat transfer distribution exhibits a peak at the stagnation point and secondary peaks at a radial location that is both excitation frequency and Reynolds number dependent. Distributions of the fluctuating component of the heat transfer coefficient are also presented for the range of parameters tested. These have been used, along with spectral analysis of the heat flux signal, to discern whether local variations in heat transfer are due to changes in the local vortex flow or to changes in the mean flow structure of the impinging jet.

Computational Investigation of Flow and Heat Transfer Characteristics of Impingement Cooling Channel

2013 ◽  
Author(s):  
B. V. N. Ramakumar ◽  
D. S. Joshi ◽  
Murari Sridhar ◽  
Jong S. Liu ◽  
Daniel C. Crites
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Heat Transfer Analysis ◽  
Computational Investigation ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Impingement Cooling ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
High Heat Transfer

Impingement cooling offers very high heat transfer coefficients. Flow field, involved in impingement cooling is dominated by stagnation zone, transition zone and developing zone. Understanding of complex flow phenomenon and its effects on heat transfer characteristics is useful for efficient designing of impingement channels. Computational fluid dynamics (CFD) has emerged as a powerful tool for the analysis of flow and heat transfer systems. Honeywell has been investigating the use of CFD to determine the characteristics of various complex turbine blade cooling heat transfer augmentation methods such as impingement. The objective of this study is to develop CFD methodology which is suitable for computational investigation of flow and heat transfer analysis of impingement cooling through validation. Single row of circular jets impinging on concave (curved) surface has been considered for this study. The validation was accomplished with the test results of Bunker and Metzger [10] and with the correlations of Chupp et al. [7]. The parameters which are varied in this study include jet Reynolds number (Re2B = 6750–10200), target plate distance to jet diameter ratio (Z/d = 3 and 4), and target surface sharpness (i.e. radius ratio, r* = 0.2, 0.4 and 1) the simulations are performed under steady state conditions. Predicted results are compared for local endwall heat transfer results along the curve length of the mid span target wall. Flow field results obtained at different locations are presented to understand the heat transfer behavior.

scholarly journals Opportunities in Jet-Impingement Cooling for Gas-Turbine Engines

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6587
Author(s):  
Sandip Dutta ◽  
Prashant Singh
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Target Surface ◽  
Turbine Engines ◽  
High Porosity ◽  
Transfer Coefficients ◽  
Impingement Cooling ◽  
Heat Transfer Coefficients ◽  
Impingement Heat Transfer ◽  
Convective Heat Transfer Coefficients

Impingement heat transfer is considered one of the most effective cooling technologies that yield high localized convective heat transfer coefficients. This paper studies different configurable parameters involved in jet impingement cooling such as, exit orifice shape, crossflow regulation, target surface modification, spent air reuse, impingement channel modification, jet pulsation, and other techniques to understand which of them are critical and how these heat-transfer-enhancement concepts work. The aim of this paper is to excite the thermal sciences community of this efficient cooling technique and instill some thoughts for future innovations. New orifice shapes are becoming feasible due to innovative 3D printing technologies. However, the orifice shape variations show that it is hard to beat a sharp-edged round orifice in heat transfer coefficient, but it comes with a higher pressure drop across the orifice. Any attempt to streamline the hole shape indicated a drop in the Nusselt number, thus giving the designer some control over thermal budgeting of a component. Reduction in crossflow has been attempted with channel modifications. The use of high-porosity conductive foam in the impingement space has shown marked improvement in heat transfer performance. A list of possible research topics based on this discussion is provided in the conclusion.

Microjet Impingement Cooling With Phase Change

2004 ◽  
Author(s):  
Evelyn N. Wang ◽  
Juan G. Santiago ◽  
Kenneth E. Goodson ◽  
Thomas W. Kenny
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Heated Surface ◽  
Heat Removal ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Impingement Cooling ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Wall Superheat

The large heat generation rates in contemporary microprocessors require new thermal management solutions. Two-phase microjet impingement cooling promises high heat transfer coefficients and effective cooling of hotspots. We have fabricated integrated microjet structures with heaters and temperature sensors to study local heat transfer at the impingement surface of a confined microjet. Circular jets with diameters less than 100 μm are machined in glass. Preliminary temperature measurements (for Rej = 100–500) suggest that heat transfer coefficients of 1000 W/m2C close to the jet stagnation zone can be achieved. As the flowrate of the jet is increased, a tradeoff in heat removal capability and wall superheat is observed. To aid in understanding the mechanism for wall superheat during boiling at the heated surface, the devices allow for optical access through the top of the device. However, the formation of vapor from the top reservoir makes visualization difficult. This study aids in the design of microjet heat sinks used for integration into a closed-loop cooling system.

Heat Transfer From Novel Target Surface Structures to a Normally-Impinging, Submerged and Confined Water Jet

2009 ◽  
Author(s):  
N. Jeffers ◽  
J. Punch ◽  
E. Walsh
Keyword(s):  
Heat Transfer ◽  
Target Surface ◽  
Water Jet ◽  
Heat Fluxes ◽  
Surface Structures ◽  
Confined Water ◽  
Transfer Coefficients ◽  
Component Level ◽  
High Heat Transfer ◽  
Novel Target

Contemporary electronic systems generate high component-level heat fluxes. Impingement cooling is an effective way to induce high heat transfer coefficients in order to meet thermal constraints. The objective of this paper was to experimentally investigate the heat transfer from five novel target surface structures to a normally-impinging, submerged and confined water jet. The five target structures were: a 90° vane; a 4×4 pin fin array; and three geometries which turn the flow away from, and back towards, the surface to be cooled. The experiments were conducted for Reynolds numbers of 500 ≤ Re ≤ 24 000. The confined impinging jet was geometrically constrained to a round, 8.5mm diameter, square-edged nozzle at a jet exit-to-target surface spacing, of H/D = 0.5. The heat transfer characteristics of the five novel target surfaces were non-dimensionally compared to a flat surface, and enhancements of up to 120% were recorded. Increases of up to 45% was noted when the surface area augmentation of the target surface structures was factored out. The findings of the paper are of practical relevance to the design of primary heat exchangers for high-flux thermal management applications.

Numerical Simulation of Condensation in a Minichannel

2009 ◽  
Author(s):  
Enrico Da Riva ◽  
Davide Del Col
Keyword(s):  
Heat Transfer ◽  
Numerical Models ◽  
Vapour Phase ◽  
High Heat ◽  
Liquid Interface ◽  
Interface Temperature ◽  
Transfer Coefficients ◽  
Cross Sectional ◽  
High Heat Transfer ◽  
Vapour Quality

A steady-state Volume of Fluid (VOF) simulation of condensation of R134a inside a 1 mm i.d. minichannel is proposed. The minichannel is horizontally oriented and both the effects of gravity and surface tension are taken into account. A uniform interface temperature, as well as a uniform wall temperature, were fixed as boundary conditions in order to model the phase change process. The mass flux is G = 200 kg m−2s−1 and it has been assumed that the flow was laminar inside the liquid phase and turbulent inside the vapour phase. Turbulence has been handled by a modified low-Re k-ω model. Numerical models adopted to handle such assumptions are presented and discussed. Computational results displaying the evolution of vapour-liquid interface, cross-sectional void fraction, vapour quality and heat transfer coefficient are reported and compared against some empirical correlations. In the simulation, the fluid is condensated till reaching around 0.5 vapour quality. At inlet, the liquid film is thin and evenly distributed all around the tube circumference, therefore high heat transfer coefficients are obtained. All the liquid condensated at the vapour-liquid interface is shown to be drained by gravity to the bottom of the minichannel. For this reason, moving downstream the channel, the film at the bottom of the pipe becomes thicker, while the film thickness keeps almost constant in the entire upper half of the minichannel.

An Experimental Investigation into the Effect of Changes in the Geometry of a Slot Nozzle on the Heat Transfer Characteristics of an Impinging Air Jet

1983 ◽  
Vol 197 (1) ◽  
pp. 7-15 ◽  
Author(s):  
H Hardisty ◽  
M Can
Keyword(s):  
Heat Transfer ◽  
High Heat ◽  
Slot Width ◽  
Test Series ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Air Jets ◽  
Air Jet ◽  
High Heat Transfer ◽  
Nozzle Shape

High velocity, impinging, air jets are commonly used for heating, cooling, drying etc., because of the high heat transfer coefficients which occur in the impingement region. To provide data for design, a variety of slot nozzles has been tested to determine the effect on heat transfer of both nozzle shape and slot width. A small heat flux meter was used to measure local values of the heat transfer coefficient in the impingement zone, and these local values were integrated to yield space average values. As a necessary preliminary to the heat transfer investigation, the discharge coefficients of the nozzles were measured. From the first test series it was found that heat transfer results from differently shaped nozzles could be satisfactorily correlated provided that the effective slot width was used to characterize nozzle shape. From the second test series it was found that for geometrically similar arrangements, narrower slots gave higher heat transfer coefficients.

Heat Transfer From Novel Target Surface Structures to a Normally Impinging, Submerged and Confined Water Jet

2009 ◽  
Vol 1 (3) ◽  
Author(s):  
Nicholas M. R. Jeffers ◽  
Jeff Punch ◽  
Edmond J. Walsh ◽  
Marc McLean
Keyword(s):  
Heat Transfer ◽  
Target Surface ◽  
Water Jet ◽  
Heat Fluxes ◽  
Surface Structures ◽  
Confined Water ◽  
Transfer Coefficients ◽  
Mean Velocity ◽  
High Heat Transfer ◽  
Novel Target

Contemporary electronic systems generate high component-level heat fluxes. Impingement cooling is an effective way to induce high heat transfer coefficients in order to meet thermal constraints. The objective of this paper is to experimentally investigate the heat transfer from five novel target surface structures to a normally impinging, submerged, and confined water jet. The five target structures were: 90 deg vane, a 2×2 pin fin array, and three geometries, which turn the flow away from, and back towards, the surface to be cooled to create an annular jet. The experiments were conducted for inlet Reynolds numbers of 500≤Re≤22,000, based on the mean velocity and jet tube diameter. The confined impinging jet was geometrically constrained to a round 8.5 mm diameter, square edged nozzle at a jet exit-to-target surface spacing of H/D=0.5. The heat transfer characteristics of the five target surfaces were nondimensionally compared to a flat surface, and surface effectiveness of up to 2.2 was recorded. Enhancements of up to 45% were noted when the wetted surface area of the target surface structures was considered. The pressure drop attributed to the target surfaces is also considered. The findings of the paper are of practical relevance to the design of primary heat exchangers for high-flux thermal management applications, where the boundaries of cooling requirements continue to be tested.

scholarly journals Heat Transfer and Fluid Dynamics Measurements in the Expansion Space of a Stirling Cycle Engine

2006 ◽  
Author(s):  
Nan Jiang ◽  
Terrence W. Simon
Keyword(s):  
Heat Transfer ◽  
High Efficiency ◽  
Stirling Engine ◽  
Transfer Coefficients ◽  
Head Region ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Engine Design ◽  
Region Flow ◽  
Design Calculations

The heater (or acceptor) of a Stirling engine, where most of the thermal energy is accepted into the engine by heat transfer, is the hottest part of the engine. Almost as hot is the adjacent expansion space of the engine. In the expansion space, the flow is oscillatory, impinging on a two-dimensional concavely-curved surface. Knowing the heat transfer on the inside surface of the engine head is critical to the engine design for efficiency and reliability. However, the flow in this region is not well understood and support is required to develop the CFD codes needed to design modern Stirling engines of high efficiency and power output. The present project is to experimentally investigate the flow and heat transfer in the heater head region. Flow fields and heat transfer coefficients are measured to characterize the oscillatory flow as well as to supply experimental validation for the CFD Stirling engine design codes. Presented also is a discussion of how these results might be used for heater head and acceptor region design calculations.

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