Heat Transfer Measurements for Array Jet Impingement With Castellated Wall

2021 ◽  
Author(s):  
Taehyun Kim ◽  
Eui Yeop Jung ◽  
Minho Bang ◽  
Changyong Lee ◽  
Hee Koo Moon ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Leading Edge ◽  
Jet Impingement ◽  
Target Surface ◽  
Impinging Jets ◽  
Wall Jet ◽  
Impingement Cooling ◽  
Baseline Case ◽  
Rib Structure

Abstract Impingement cooling is one of the powerful cooling methods in high-temperature devices. For the gas turbine applications, impingement cooling is commonly applied in the transition piece of a combustor and in the leading edge, suction and pressure sides of a turbine blade/vane. In the suction side and pressure side, impingement cooling is applied as a form of an array jet. However, due to the small gap between the jet hole and target surface, the wall jet faces a crossflow inside of the gap. This crossflow has an adverse effect on the jets and deteriorates the heat/mass transfer performance. Therefore, several studies have been conducted to minimized the crossflow effect. The present study also investigated the effect of crossflow reduction in the gap by having a castellated hole plate. The heat/mass transfer was measured using the naphthalene sublimation method. Heat/mass transfer data are compared among three different cases. One is the baseline case which is simple array impinging jets. Others are the castellated cases with and without rib structures on the target wall. Jet-to-jet spacing (s/d) and jet-to-target spacing (z/d) are selected as geometrical variables. Also, the experiments were conducted for the Reynolds numbers (based on jet hole diameter) of 5,000, 15,000 and 30,000. The baseline case was named as B case, the castellated case without rib structure as C case and with rib structure as CR case. Both C and CR cases showed the crossflow reduction effect and resulted high and similar Nusselt number values.

Heat Transfer Measurements for Array Jet Impingement with Castellated Wall

2021 ◽  
pp. 1-27
Author(s):  
Taehyun Kim ◽  
Eui Yeop Jung ◽  
Minho Bang ◽  
Changyong Lee ◽  
Hee-Koo Moon ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Leading Edge ◽  
Jet Impingement ◽  
Target Surface ◽  
Suction Side ◽  
Wall Jet ◽  
Impingement Cooling ◽  
Baseline Case ◽  
Sublimation Method ◽  
Reduction Effect

Abstract Impingement cooling is one of the powerful cooling methods in high-temperature devices. For gas turbine applications, impingement cooling is commonly applied in the transition piece of a combustor and in the leading edge, suction, and pressure sides of a turbine blade/vane. In the suction side and pressure side, impingement cooling is applied as a form of an array jet. However, due to the small gap between the jet hole and target surface, the wall jet faces a crossflow inside of the gap. This crossflow has an adverse effect on jets and deteriorates the heat transfer performance. Therefore, several studies have been conducted to minimize the crossflow effect. The present study also investigated the effect of crossflow reduction in the gap by having a castellated hole plate. The heat transfer was measured using the naphthalene sublimation method. Heat transfer data are compared among three different cases. One is the baseline case which is simple array jets. Others are the castellated cases with and without rib structures on the target wall. Jet-to-jet spacing(s/d) and jet-to-target spacing(z/d) are selected as geometrical variables. Also, the experiments were conducted for the Reynolds numbers (based on jet hole diameter) of 5,000, 15,000 and 30,000. The baseline case was named as B case, the castellated case without rib as C case and with rib as CR case. Both castellated cases showed the crossflow reduction effect and resulted high and similar Nusselt number values.

Characterization of Impingement Heat/Mass Transfer to the Synthetic Jet Generated by a Biomimetic Actuator

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Zdeněk Trávníček ◽  
Zuzana Broučková
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Mass Transfer Rate ◽  
Jet Impingement ◽  
Flux Measurement ◽  
Impinging Jets ◽  
Synthetic Jet ◽  
Working Fluid ◽  
Naphthalene Sublimation Technique ◽  
Flexible Diaphragm

Two biomimetic synthetic jet (SJ) actuators were designed, manufactured, and tested under conditions of a jet impingement onto a wall. Nozzles of the actuators were formed by a flexible diaphragm rim, the working fluid was air, and the operating frequencies were chosen near the resonance at 65 Hz and 69 Hz. Four experimental methods were used: phase-locked visualization of the oscillating nozzle lips, jet momentum flux measurement using a precision scale, hot-wire anemometry, and mass transfer measurement using the naphthalene sublimation technique. The results demonstrated possibilities of the proposed actuators to cause a desired heat/mass transfer distribution on the exposed wall. It was concluded that the heat/mass transfer rate was commensurable with a conventional continuous impinging jets (IJs) at the same Reynolds numbers.

Local heat/mass transfer of array jet impingement cooling with pin-fin heat sinks

2021 ◽  
pp. 1-1
Author(s):  
Taehyun Kim ◽  
Eui Yeop Jung ◽  
Seungyeong Choi ◽  
Hee Seung Park ◽  
Changyong Lee ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Jet Impingement ◽  
Local Heat ◽  
Heat Sinks ◽  
Impingement Cooling ◽  
Pin Fin

Numerical Study of Flow and Heat Transfer of Impingement Cooling on Model of Turbine Blade Leading Edge

2010 ◽  
Author(s):  
Zhao Liu ◽  
Zhenping Feng ◽  
Liming Song
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Numerical Study ◽  
Leading Edge ◽  
Jet Impingement ◽  
Target Surface ◽  
Nozzle Diameter ◽  
Impingement Cooling ◽  
Jet Nozzle ◽  
Blade Leading Edge

In this paper a numerical simulation is performed to simulate the impingement cooling on internal leading edge region, which is stretched by the middle cross section of the first stage rotor blade of GE-E3 engine high pressure turbine, and in the condition that jets flow is ejected from a row of four different diameter circular nozzles. The relative performances of three versions of turbulence models including the RNG κ-ε model, the standard κ-ω model and the SST κ-ω model in the simulation of a row of circle jet impingement heat transfer are compared with available experimental data. The results show that SST κ-ω model is the best one based on simulation accuracy. Then the SST κ-ω model is adopted for the simulation. The grid independence study is also carried out by using the Richardson extrapolation method. A single array of circle jets is arranged to investigate the impingement cooling and its effectiveness. Four different jet nozzle diameters are studied and seven different inlet flow Mach numbers of each jet nozzle diameter are calculated. The influence of the ratio of the spacing of jet nozzle from the target surface to the jet nozzle diameter on impingement cooling is also studied, in case of a constant ratio of jet spacing to jet nozzle diameter in different jet nozzle diameters. The results indicate that the heat transfer coefficient on the turbine blade leading edge increases with the increase of jet Mach number and jet nozzle diameter, the spanwise area weight average Nusselt number decreases with the increase of the ratio of the spacing of jet nozzle from the target surface to jet nozzle diameter, and a lower ratio of spacing of jet nozzle from the target surface to the jet nozzle diameter is desirable to improve the performance of impingement cooling on turbine leading edge.

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.

Effects of Hole Arrangements on Local Heat/Mass Transfer for Impingement/Effusion Cooling With Small Hole Spacing

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Hyung Hee Cho ◽  
Dong Ho Rhee ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Heat Mass Transfer ◽  
Single Layer ◽  
Target Surface ◽  
Local Heat ◽  
Impinging Jets ◽  
Diameter Ratio ◽  
Perforated Plates

The present study investigates the local heat (mass) transfer characteristics of flow through perforated plates. Two parallel perforated plates were placed, relative to each other, in either staggered, in line, or shifted in one direction. Hole length to diameter ratio of 1.5, hole pitch to diameter ratio of 3.0, and distance between the perforated plates of 1–3 hole diameters are used at hole Reynolds numbers of 3000 to 14,000. For flows through the staggered layers and the layers shifted in one direction, the mass transfer rates on the surface of the effusion plate increase approximately 50% from impingement cooling alone and are about three to four times that with effusion cooling alone (single layer). The high transfer rate is induced by strong secondary vortices formed between two adjacent impinging jets and flow transition so that heat/mass transfer coefficient in the midway region is as high as stagnation heat/mass transfer coefficient. The mass transfer coefficient for the in-line arrangement is approximately 100% higher on the target surface than that of the single layer case. In overall, the staggered hole arrangement shows better performance than other cases.

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

2002 ◽  
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 2 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 6 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.

Experimental and Numerical Investigation of a Shower Head Advanced Jet Impingement on Concave Surfaces

2018 ◽  
Author(s):  
Alankrita Singh ◽  
Bhamidi V. S. S. S. Prasad
Keyword(s):  
Heat Transfer ◽  
Leading Edge ◽  
Jet Impingement ◽  
Target Surface ◽  
Curvature Effect ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Impingement Heat Transfer ◽  
Gap Ratio ◽  
Improved Performance

A novel configuration of jet impingement cooling for leading edge of a gas turbine blade is proposed in this paper. The new configuration is obtained by rearranging the jet impingement holes in a shower head fashion with a combination of circular and elliptic holes. The entire configuration is simulated by a jet impingement pipe (JIP) to experimentally investigate the improved performance of cooling of concave target surfaces. The central JIP has circular ends, remaining four neighboring JIP have 45° chamfer at one of its ends facing target surface to ensure uniformity and extension in cooling coverage. The heat transfer characteristics of jet impingement were investigated both experimentally and numerically by varying jet Reynolds number and gap ratio. Simulations are also carried out for different curvature ratios to determine the relative surface curvature effect on jet impingement heat transfer. This is accomplished by varying diameter of concave surface. The augmentation in heat transfer by both the elliptic (chamfered JIP) and circular (whose all JIP ends are circular) shower head arrangements are compared.

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