Heat Transfer Characteristics of an Angled Array Impinging Jet on a Concave Duct

2012 ◽  
Author(s):  
Eui Yeop Jung ◽  
Chan Ung Park ◽  
Dong Hyun Lee ◽  
Kyung Min Kim ◽  
Ta-kwan Woo ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Stagnation Points ◽  
Transfer Characteristics ◽  
Jet Cooling

This study investigated the heat transfer characteristics of an array jet cooling system on a concave surface. Two types of injection holes were used: one for impinging jets normal to the impingement surface, and the other for angled impinging jets. For the normal jets, the jet Reynolds number (Re) based on the hole diameter varied from 3,000 to 10,000, and the height-to-diameter ratio (H/d) was fixed at 1.0. There were 15 injection holes positioned in a staggered 3×5 array. For the angled jets, Re was set to 5,000 and H/d was also fixed at 1.0. Naphthalene sublimation method was used to determine the heat transfer coefficients on the targeted plates. For normal impinging jet cooling, separate peaks were observed at the stagnation regions due to the curvature effect. Since a crossflow was generated by air spent from the jet arrays, the crossflow effect increased as it moved downstream. Due to the interaction between the crossflow and impinging jets, the peak values at the stagnation points increased downstream. The heat transfer coefficient on the targeted plate increased with Re. The average Sh of the angled jets was higher than that of the normal jets, as the obliquely impinging jet increased the mass flow rate and mass interaction between the jet impingement points.

MEMS Impinging-Jet Cooling

2000 ◽  
Author(s):  
Qiao Lin ◽  
Shuyun Wu ◽  
Yin Yuen ◽  
Yu-Chong Tai ◽  
Chin-Ming Ho
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Measured Temperature ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Jet Cooling

Abstract This paper presents an experimental investigation on MEMS impinging jets as applied to micro heat exchangers. We have fabricated MEMS single and array jet nozzles using DRIE technology, as well as a MEMS quartz chip providing a simulated hot surface for jet impingement. The quartz chip, with an integrated polysilicon thin-film heater and distributed temperature sensors, offers high spatial resolution in temperature measurement due to the low thermal conductivity of quartz. From measured temperature distributions, heat transfer coefficients are computed for single and array micro impinging jets using finite element analysis. The results from this study for the first time provide extensive data on spatial distributions of micro impinging-jet heat transfer coefficients, and demonstrate the viability of MEMS heat exchangers that use micro impinging jets.

Numerical Simulation Study of Impinging Jet Impact Fin Surface on Heat Transfer Characteristics

2013 ◽  
Vol 663 ◽  
pp. 586-591 ◽  
Author(s):  
Li Ming Zhou ◽  
Lei Zhu ◽  
Jing Quan Zhao ◽  
Meng Zheng
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Thermal Resistance ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Transfer Characteristics ◽  
Jet Impact ◽  
Jet Array

Three-dimensional numerical simulation was implemented to analyze the heat transfer characteristics for jet impingement impact fin surface. 60 calculation cases were simulated to investigate the effects of different fin surfaces on heat transfer characteristics, and 12 jet array impingement cases were calculated for comparison. The results shown that the fin shape, the height and the fin arrangement were the critical factors to affect the jet impingement and the best combination were existed in a certain range. The thermal resistance of cylinder fin arranged in order was34.7 percent higher than that of cylinder fin arranged staggered. The thermal resistance of square fin arranged in order was38.9 percent higher than that of square fin arranged staggered .The heat transfer coefficients of impinging jet impact fin surface were better than that of jet array impingement. The fitting correlations on heat transfer of impinging jet impact fin surface were given.

Influences of Small Jet-to-Wall Spacings on Heat Transfer Characteristics and Flow-Field Entrainment Effects of Microscale Jets

2021 ◽  
Vol 143 (3) ◽  
Author(s):  
Prabhakar Subrahmanyam ◽  
B. K. Gnanavel
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Jet Impingement ◽  
Impinging Jets ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Inlet System ◽  
Potential Core ◽  
Transfer Characteristics ◽  
The Impact

Abstract Detailed heat transfer distributions of multiple microscaled tapered jets orthogonally impinging on the surface of a high-power density silicon wall is presented. The tapered jets issued from two different impingement setup are studied—(a) single circular nozzle and (b) dual circular nozzles. Jets are issued from the inlet(s) at four different Reynolds numbers {Re = 8000, 12,000, 16,000, 20,000}. The spacing between the tapered nozzle jets and the bare die silicon wall (z/d) is adjusted to be 4, 8, 12, and 16 jet nozzle diameters away from impinging influence. The impact of varying the nozzle to the silicon wall (z/d) standoff spacing up to 16 nozzle jet diameters and its effects on flow fields on the surface of the silicon, specifically the entrainment pattern on the silicon surface, is presented. Heat transfer characteristics of impinging jets on the hot silicon wall is investigated by means of large eddy simulations (LES) at a Reynolds of 20,000 on each of the four z/d spacing and compared against its equivalent Reynolds-averaged Navier–Stokes (RANS) cases. Highest heat transfer coefficients are obtained for the dual inlet system. A demarcation boundary region connecting all the microvortices between impinging jets is prominently visible at smaller z/d spacing—the region where the target silicon wall is within the sphere of influence of the potential core of the jet. This research focuses on the underlying physics of multiple tapered nozzles jet impingement issued from single and dual nozzles and its impact on turbulence, heat transfer distributions, entrainment, and other pertinent flow-field characteristics.

Heat Transfer Characteristics of Downward Facing Hot Horizontal Surfaces Using Mist Jet Impingement

2017 ◽  
Author(s):  
Ashutosh Kumar Yadav ◽  
Parantak Sharma ◽  
Avadhesh Kumar Sharma ◽  
Mayank Modak ◽  
Vishal Nirgude ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Cooling System ◽  
Water Pressure ◽  
Jet Impingement ◽  
Surface Heat ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Transfer Characteristics

Impinging jet cooling technique has been widely used extensively in various industrial processes, namely, cooling and drying of films and papers, processing of metals and glasses, cooling of gas turbine blades and most recently cooling of various components of electronic devices. Due to high heat removal rate the jet impingement cooling of the hot surfaces is being used in nuclear industries. During the loss of coolant accidents (LOCA) in nuclear power plant, an emergency core cooling system (ECCS) cool the cluster of clad tubes using consisting of fuel rods. Controlled cooling, as an important procedure of thermal-mechanical control processing technology, is helpful to improve the microstructure and mechanical properties of steel. In industries for heat transfer efficiency and homogeneous cooling performance which usually requires a jet impingement with improved heat transfer capacity and controllability. It provides better cooling in comparison to air. Rapid quenching by water jet, sometimes, may lead to formation of cracks and poor ductility to the quenched surface. Spray and mist jet impingement offers an alternative method to uncontrolled rapid cooling, particularly in steel and electronics industries. Mist jet impingement cooling of downward facing hot surface has not been extensively studied in the literature. The present experimental study analyzes the heat transfer characteristics a 0.15mm thick hot horizontal stainless steel (SS-304) foil using Internal mixing full cone (spray angle 20 deg) mist nozzle from the bottom side. Experiments have been performed for the varied range of water pressure (0.7–4.0 bar) and air pressure (0.4–5.8 bar). The effect of water and air inlet pressures, on the surface heat flux has been examined in this study. The maximum surface heat flux is achieved at stagnation point and is not affected by the change in nozzle to plate distance, Air and Water flow rates.

Heat Transfer Characteristic Analysis of Confined Impinging Jet Cooling System with Micro-Scale Round Nozzles

2010 ◽  
Vol 171-172 ◽  
pp. 799-803
Author(s):  
Chang Hong Wang ◽  
Ying Chen ◽  
Juan Tu
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Transfer Characteristic ◽  
Characteristic Analysis ◽  
Chip Cooling ◽  
Jet Cooling ◽  
Air Jet ◽  
Nozzle Type

In order to investigate the heat transfer of confined impinging jet with tiny size round nozzle, a bakelite laminate was used as the heat transfer surface of simulated chip. The thermocouples were mounted symmetrically along the diagonal of the laminate to measure the temperature distribution of the surface. The parameters such as Reynolds number (Re) and ratio of height-to-diameter were changed to investigate the radial distribution of Nu and the characteristics of heat transfer in stagnant section. The results show that hear transfer coefficient at stagnation point is maximal. It is decreased with the increases of the radial jet distance, but increased with Re and impinging height. Moreover, the effect of single-nozzle type is stronger than that of multi-nozzle type in the cases of same air flow. These studies will give a way for the application of air jet impingement in the electronics chip cooling.

Experimental and Numerical Investigation of Heat Transfer Characteristics of Inline and Staggered Arrays of Impinging Jets

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Yunfei Xing ◽  
Sebastian Spring ◽  
Bernhard Weigand
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Local Heat Transfer ◽  
Impinging Jets ◽  
Design Tool ◽  
Thermal Design ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Transfer Characteristics ◽  
Plate Spacing

A combined experimental and numerical investigation of the heat transfer characteristics within an array of impinging jets has been conducted. The experiments were carried out in a perspex model using a transient liquid crystal method. Local jet temperatures were measured at several positions on the impingement plate to account for an exact evaluation of the heat transfer coefficient. The effects of the variation in different impingement patterns, jet-to-plate spacing, crossflow schemes, and jet Reynolds number on the distribution of the local Nusselt number and the related pressure loss were investigated experimentally. In addition to the measurements, a numerical investigation was conducted. The motivation was to evaluate whether computational fluid dynamics (CFD) can be used as an engineering design tool in the optimization of multijet impingement configurations. This required, as a first step, a validation of the numerical results. For the present configuration, this was achieved assessing the degree of accuracy to which the measured heat transfer rates could be computed. The overall agreement was very good and even local heat transfer coefficients were predicted at high accuracy. The numerical investigation showed that state-of-the-art CFD codes can be used as suitable means in the thermal design process of such configurations.

Numerical study on flow and heat transfer characteristics of air-jet cooling system

2018 ◽  
Vol 32 (12) ◽  
pp. 6021-6027 ◽  
Author(s):  
Joo Hyun Moon ◽  
Soyeong Lee ◽  
Jee Min Park ◽  
Jungho Lee ◽  
Daejoong Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Numerical Study ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Jet Cooling ◽  
Flow And Heat Transfer ◽  
Air Jet

Heat Transfer Enhancement of Impinging Jet from Pulse Jet Combustor

2014 ◽  
Vol 931-932 ◽  
pp. 1228-1232
Author(s):  
Pathomporn Narato ◽  
Kittinan Maliwan ◽  
Chayut Nuntadusit
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Flow Characteristics ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Heat Flux Sensor ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Pulse Jet

The aims of this study are to investigate flow characteristics in pulse jet combustor and heat transfer characteristics of impinging jet from pulse jet combustor. The combustor is Helmholtz type which has single combustor chamber and single tailpipe. The inner diameter (D) of tailpipe was 47 mm and tailpipe length was about 16D. The effect of number of air inlets: single inlet, double inlets with 90o apart, double inlets with 180o apart and triple inlets with 90o apart on flow and heat transfer characteristics were studied. A water cooled heat flux sensor was applied to measure heat transfer rate on the surface at stagnation point. The jet-to-plate distance was varied at L=1D, 2D, 4D, 6D and 8D. Two of pressure transducers were mounted on the wall of combustion chamber and on the wall of tailpipe at 4D from tailpipe outlet to measure pressure simultaneously. It is found that the variation of pressure near the tailpipe outlet is strongly depended on air inlet configurations. The pressure variations in pulse jet combustor could be preliminary related to the temperature and velocity of jet from tailpipe and heat transfer rate on jet impingement surface.

scholarly journals Effect of Rotation Number on Heat Transfer Characteristics of a Row of Impinging Jets in Confined Channel

2020 ◽  
Vol 77 (1) ◽  
pp. 161-171
Author(s):  
Thantup Nontula ◽  
Natthaporn Kaewchoothong ◽  
Wacharin Kaew-apichai ◽  
Chayut Nuntadusit
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rotation Number ◽  
Turbine Blades ◽  
Jet Impingement ◽  
Impinging Jets ◽  
Internal Cooling ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Impingement Surface

Jet impingement has been applied for internal cooling in gas turbine blades. In this study, heat transfer characteristics of impinging jets from a row of circular orifices were investigated inside a flow channel with rotations. The Reynolds number (Re) based on the jet mean velocity was fixed at 6,700. Whereas, the rotation number (Ro) of a channel was varied from 0 to 0.0099. The jet-to-impingement distance ratio (L/Dj) and jet pitch ratio (P/Dj) were respective 2 and 4, Dj is a jet diameter of 5 mm. The thermochromic liquid crystals (TLCs) technique was used to measure the heat transfer coefficient distributions on an impingement surface. The results show that heat transfer enhancement on a jet impingement surface depended on the effects of crossflow and Coriolis force. The local Nusselt number at X/Dj?20 on the leading side (LS) was higher than on the trailing side (TS) while heat transfer on the LS at 20?X/Dj?40 gained the lowest, compared to on the TS. The average Nusselt number ratios ( ) on the TS at Ro = 0.0049 gave higher than on the LS of around 2.17%. On the other hand, the on the TS at Ro = 0.0099 was less than the LS of about 0.08%.

Flow and Heat (Mass) Transfer Characteristics in an Impingement/Effusion Cooling System With Crossflow

2003 ◽  
Vol 125 (1) ◽  
pp. 74-82 ◽  
Author(s):  
Dong Ho Rhee ◽  
Jong Hyun Choi ◽  
Hyung Hee Cho
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Cooling System ◽  
Jet Impingement ◽  
Impinging Jets ◽  
Hole Diameter ◽  
Jet Flows ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Transfer Characteristics

The present study is conducted to investigate flow and heat/mass transfer characteristics in an impingement/effusion cooling system with crossflow. To simulate the impingement/effusion cooling system, two perforated plates are placed in parallel and staggered arrangements with a gap distance of two times of the hole diameter, and initial crossflow passes between the plates. Both the injection and effusion hole diameters are 10 mm, and the Reynolds number based on the hole diameter and hole-to-hole pitch are fixed to 10,000 and six times of the hole diameter, respectively. To investigate the effect of crossflow, the flow rate of crossflow is changed from 0.5 to 2 times of that of the impinging jet, and the results of impingement/effusion cooling with crossflow are compared with those of the crossflow in the channel and of an array of impingement jets and the effusion cooling system. A naphthalene sublimation method is used to determine the local heat/mass transfer coefficients on the upward facing surface of the effusion plate. The flow patterns are calculated numerically using a commercial package. With the initial crossflow, the flow and heat/mass transfer characteristics are changed significantly from the results without the crossflow. Jet flows ejected from the injection plate are deflected by the crossflow, so that the stagnation points of the impinging jets move downstream. The heat/mass transfer rates on the effusion (target) plate decrease as the velocity of crossflow increases, since the crossflow induces the locally low transfer regions formed at the mid-way between the effusion holes. However, the impingement/effusion cooling with crossflow presents higher heat/mass transfer rates than the array jet impingement cooling with the same initial crossflow.

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