The Effect of Entrainment Temperature on Jet Impingement Heat Transfer

1984 ◽  
Vol 106 (1) ◽  
pp. 27-33 ◽  
Author(s):  
S. A. Striegl ◽  
T. E. Diller
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Recirculation Region ◽  
Measured Temperature ◽  
Air Jets ◽  
Impingement Heat Transfer ◽  
Single Jet ◽  
Multiple Plane

An experimental study was done to determine the effect of entrainment temperature on the local heat transfer rates to single and multiple, plane, turbulent impinging air jets. To determine the effect of entrainment of the surrounding fluid, the single jet issued into an environment at a temperature which was varied between the initial temperature of the jet and the temperature of the heated impingement plate. An analytical model was used to correlate the measured heat transfer rate to a single jet. The effect of the entrainment temperature in a single jet was then used to analyze the effect of entrainment from the recirculation region between the jets of a jet array. Using the measured temperature in the recirculation region to include the effect of entrainment, the single jet correlations were successfully applied to multiple jets.

scholarly journals Numerical heat transfer analysis of micro-scale jet-impingement cooling in a high-pressure turbine vane

2021 ◽  
Author(s):  
Karan Anand
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Transfer Analysis ◽  
Transfer Rates ◽  
Numerical Heat Transfer ◽  
Turbine Vane ◽  
Single Jet

This research provides a computational analysis of heat transfer due to micro jet-impingement inside a gas turbine vane. A preliminary-parametric analysis of axisymmetric single jet was reported to better understand micro jet-impingement. In general, it was seen that as the Reynolds number increased the Nusselt number values increased. The jet to target spacing had a considerably lower impact on the heat transfer rates. Around 30% improvement was seen by reducing the diameter to half while changing the shape to an ellipse saw 20.8% improvement in Nusselt value. The numerical investigation was then followed by studying the heat transfer characteristics in a three-dimensional, actual-shaped turbine vane. Effects of jet inclination showed enhanced mixing and secondary heat transfer peaks. The effect of reducing the diameter of the jets to 0.125 mm yielded 55% heat transfer improvements compared to 0.51 mm; the tapering effect also enhanced the local heat transfer values as local velocities at jet exit increased.

An Analysis of the Effect of Entrainment Temperature on Jet Impingement Heat Transfer

1984 ◽  
Vol 106 (4) ◽  
pp. 804-810 ◽  
Author(s):  
S. A. Striegl ◽  
T. E. Diller
Keyword(s):  
Heat Transfer ◽  
Analytical Solutions ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Impinging Jet ◽  
Local Heat ◽  
Impinging Jets ◽  
Recirculation Region ◽  
Plate Temperature ◽  
Single Plane

An analytical model is developed to determine the effect of the temperature of entrained fluid (entrainment temperature) on the local heat transfer to a single, plane, turbulent impinging jet. Solutions of the momentum and energy equations for a single impinging jet are accomplished using similarity and series analyses. Solutions of the energy equation are obtained for the two limiting cases of entrainment temperatures equal to the plate temperature and the initial jet temperature. The analytical solutions are superposed to obtain the solution for all intermediate entrainment temperatures. The constants in the turbulence model are determined by comparing the analytical solutions to experimentally determined local heat transfer rates for single impinging jets issuing into an environment with a controlled entrainment temperature. When the single jet model is applied to jet arrays it predicts that the entrainment in the recirculation region between the jets can significantly affect the heat transfer. Comparison of the model to heat transfer measurements performed for jet arrays shows that the model successfully predicts the local heat transfer in jet arrays.

Heat Transfer of Confined Circular Jet Impingement

2001 ◽  
Vol 17 (1) ◽  
pp. 29-38
Author(s):  
Shou-Shing Hsieh ◽  
Jung-Tai Huang ◽  
Huang-Hsiu Tsai
Keyword(s):  
Heat Transfer ◽  
Average Nusselt Number ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Local Heat ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Plate Spacing ◽  
Single Jet

ABSTRACTExperiments for heat transfer characteristics of confined circular single jet impingement were conducted. The effect of jet Reynolds number, jet hole-to-plate spacing and heat flux levels on heat transfer characteristics of the heated target surface was examined and presented. The local heat transfer coefficient along the surface is measured and correlations of the stagnation point, local and average Nusselt number are developed and discussed. Finally, comparisons of the present data with existing results were also made.

scholarly journals Heat Transfer and Flow Characteristics of Circular Jets Impinging on a Horizontal Flat Wall

1997 ◽  
Author(s):  
Shou-Shing Hsieh ◽  
Jung-Tai Huang
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Local Heat ◽  
Plate Spacing ◽  
Fundamental Understanding ◽  
Circular Jets ◽  
Single Jet

An experimental study was performed in a confined circular single jet impingement. The effect of jet Reynolds number, nozzle-to-plate spacing and heat flux levels on heat transfer characteristics of the heated target surface was examined and presented. Flow visualization was made to broaden our fundamental understanding of the physical process of the type of flow. Transition and turbulent regimes are identified. The local heat transfer coefficient along the surface is measured and correlation of the stagnation point Nusselt number are presented and discussed.

Effect of Slot Jet Temperature on Impingement Heat Transfer Over a Heated Circular Cylinder

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Sharad Pachpute ◽  
B. Premachandran
Keyword(s):  
Heat Transfer ◽  
Circular Cylinder ◽  
Ambient Temperature ◽  
Stagnation Point ◽  
Nozzle Exit ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Rear Side ◽  
Impingement Heat Transfer

In this paper, heat transfer and effectiveness of a turbulent slot jet impinging over a heated circular cylinder have been investigated numerically by varying the ratio of jet temperature to the ambient temperature, Θj = Tj/Tamp, from 0.7 to 1.2. In all cases, the ambient temperature (Tamb) is assumed to be constant (300 K). The Reynolds number defined based on the average nozzle exit velocity, the diameter of the cylindrical target (D), and properties at the nozzle exit temperature, ReD=ρVD/μ is varied from 6000 to 20,000. The ratio of cylinder diameter to the slot width, D/S = 5.5, 8.5, and 17 are considered and the nondimensional distance from the nozzle exit to the cylinder, H/S is varied in the range of 2 ≤ H/S ≤ 12. The v′2¯−f turbulence model was used for numerical simulations. Numerical results reveal that the local Nusselt number is found to be higher at the stagnation point in the case of cold jet impingement at Θj = 0.7. The local heat transfer at the rear side of the cylinder is 8–18% less as compared to that of Θj = 1.0 for ReD = 6000. The local effectiveness calculated over a circular cylinder strongly depends on H/S and D/S. Based on the parametric study, a correlation has been provided for the local effectiveness at the stagnation point.

scholarly journals Computational Fluid Dynamics Analysis of Impingement Heat Transfer in an Inline Array of Multiple Jets

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Parampreet Singh ◽  
Neel Kanth Grover ◽  
Vivek Agarwal ◽  
Shubham Sharma ◽  
Jujhar Singh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Separation Distance ◽  
Experimental Results ◽  
Impingement Heat Transfer ◽  
Computational Fluid Dynamics Analysis ◽  
The Impact

Amid all convective heat transfer augmentation methods employing single phase, jet impingement heat transfer delivers significantly higher coefficient of local heat transfer. The arrangement leading to nine jets in square array has been used to cool a plate maintained at constant heat flux. Numerical study has been carried out using RANS-based turbulence modeling in commercial CFD Fluent software. The turbulent models used for the study are three different “k-ε” models (STD, RNG, and realizable) and SST “k-ω” model. The numerical simulation output is equated with the experimental results to find out the most accurate turbulence model. The impact of variation of Reynolds number, inter-jet spacing, and separation distance has been considered for the geometry considered. These parameters affect the coefficient of heat transfer, temperature, and turbulent kinetic energy related to flow. The local “h” values have been noticed to decline with the rise in separation distance “H/D.” The SST “k-ω” model has been noticed to be in maximum agreement with the experimental results. The average value of heat transfer coefficient “h” reduces from 210 to 193 W/m2K with increase in “H/D” from 6 to 10 at “Re” = 9000 and S/D of 3. As per numerical results, inter-jet spacing “S/D” of 3 has been determined to be the most optimum value.

Computational Study of Micro-Jet Impingement Heat Transfer in a High Pressure Turbine Vane

2011 ◽  
Author(s):  
Karan Anand ◽  
B. A. Jubran
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Spanwise Direction ◽  
Constant Property ◽  
Impingement Heat Transfer ◽  
Turbine Vane ◽  
Volume Method

The purpose of this numerical investigation is to study the micro-jet impingement heat transfer characteristics and hydromechanics in a 3-D, actual-shaped turbine vane geometry. No concession is made on either the skewness or curvature profile of the airfoil in the streamwise direction, nor to the lean, airfoil twist or tapering of the vane in the spanwise direction. The problem on hand consists of a constant property flow of air via an array of 42 round micro jets impinging onto the inner surface of the airfoil. For simplicity, validation and better understanding of the nature of impingement heat transfer, the airfoil surfaces are provided with a constant temperature boundary condition. Validation is performed against existing numerical results on a simplified model with no spanwise tapering or twisting. The modeled volume spans a total of 12D and consists of three rows of jets; each row contains 14 inline jets. Governing equations are solved using a finite volume method in FLUENT. Effects of jet inclination (+45° and −45° inclinations) and decrease in nozzle diameter (0.51, 0.25 and 0.125 mm) are studied. Inclination of −45° produced enhanced mixing and secondary peaks with marginal decrease in stagnation values. The effect of reducing the diameter of the jets yielded positive results; the tapering effect too enhanced the local heat transfer values, which is attributed to the increase in local velocities at jet exit.

Effect of Angle and Separation Distance on Heat Transfer on an Inclined Surface Subject to Airflow

2003 ◽  
Author(s):  
Srinivasan C. Rasipuram ◽  
Karim J. Nasr
Keyword(s):  
Heat Transfer ◽  
Fluid Velocity ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Impinging Jets ◽  
Separation Distance ◽  
Convective Heating ◽  
Air Jets ◽  
Inclined Surface

Impinging jets may be used to achieve enhanced local heat transfer for convective heating, cooling, or drying. The issuing jet may contact the surface normally or obliquely. Factors such as jet attachment, surface angle, jet angle, separation distance between jet orifice and surface of impingement, and trajectory influence heat transfer dramatically. This study addresses the thermal problem of jet impingement on an inclined surface. This investigation is motivated by the practical application of air jets issuing out of a defroster’s nozzles and impinging on the inclined windshield surface of a vehicle. Effect of incoming fluid velocity, angle that the inclined surface makes with the horizontal plane and angle of impinging jet on heat transfer will be examined. The results are correlated in terms of governing dimensionless parameters. The end-result will be a numerically-based correlation that is capable of predicting heat transfer on an inclined surface subject to impinging airflow.

scholarly journals Numerical heat transfer analysis of micro-scale jet-impingement cooling in a high-pressure turbine vane

2021 ◽  
Author(s):  
Karan Anand
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Transfer Analysis ◽  
Transfer Rates ◽  
Numerical Heat Transfer ◽  
Turbine Vane ◽  
Single Jet

This research provides a computational analysis of heat transfer due to micro jet-impingement inside a gas turbine vane. A preliminary-parametric analysis of axisymmetric single jet was reported to better understand micro jet-impingement. In general, it was seen that as the Reynolds number increased the Nusselt number values increased. The jet to target spacing had a considerably lower impact on the heat transfer rates. Around 30% improvement was seen by reducing the diameter to half while changing the shape to an ellipse saw 20.8% improvement in Nusselt value. The numerical investigation was then followed by studying the heat transfer characteristics in a three-dimensional, actual-shaped turbine vane. Effects of jet inclination showed enhanced mixing and secondary heat transfer peaks. The effect of reducing the diameter of the jets to 0.125 mm yielded 55% heat transfer improvements compared to 0.51 mm; the tapering effect also enhanced the local heat transfer values as local velocities at jet exit increased.

AN EXPERIMENTAL AND NUMERICAL STUDY OF HEAT TRANSFER IN A SIMULATED COLLECTOR FOR A SOLAR DRYER

1993 ◽  
Vol 17 (2) ◽  
pp. 145-160
Author(s):  
P.H. Oosthuizen ◽  
A. Sheriff
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Lower Surface ◽  
Local Heat ◽  
Electrical Heating ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Transfer Rates ◽  
Thermocouple Probe

Indirect passive solar crop dryers have the potential to considerably reduce the losses that presently occur during drying of some crops in many parts of the “developing” world. The performance so far achieved with such dryers has, however, not proved to be very satisfactory. If this performance is to be improved it is necessary to have an accurate computer model of such dryers to assist in their design. An important element is any dryer model is an accurate equation for the convective heat transfer in the collector. To assist in the development of such an equation, an experimental and numerical study of the collector heat transfer has been undertaken. In the experimental study, the collector was simulated by a 1m long by 1m wide channel with a gap of 4 cm between the upper and lower surfaces. The lower surface of the channel consisted of an aluminium plate with an electrical heating element, simulating the solar heating, bonded to its lower surface. Air was blown through this channel at a measured rate and the temperature profiles at various points along the channel were measured using a shielded thermocouple probe. Local heat transfer rates were then determined from these measured temperature profiles. In the numerical study, the parabolic forms of the governing equations were solved by a forward-marching finite difference procedure.

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