Comparison of Pressure Drop and Endwall Heat Transfer Measurements to Flow Visualization Testing of Solid and Porous Pin Fin Arrays

2009 ◽  
Author(s):  
Jared M. Pent ◽  
Jay S. Kapat ◽  
Mark Ricklick
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Visualization ◽  
Local Heat Transfer ◽  
Ccd Camera ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Porous Aluminum ◽  
Pin Fins ◽  
A Charge

This paper examines the local and averaged endwall heat transfer effects of a staggered array of porous aluminum pin fins with a channel blockage ratio (blocked channel area divided by open channel area) of 50%. Two sets of pins were used with pore densities of 0 (solid) and 10 pores per inch (PPI). The pressure drop through the channel was also determined for several flow rates using each set of pins. Local heat transfer coefficients on the endwall were measured using Thermochromatic Liquid Crystal (TLC) sheets recorded with a charge-coupled device (CCD) camera. Static and total pressure measurements were taken at the entrance and exit of the test section to determine the overall pressure drop through the channel and explain the heat transfer trends through the channel. The heat transfer and pressure data was then compared to flow visualization tests that were run using a fog generator. Results are presented for the two sets of pins with Reynolds numbers between 25000 and 130000. Local HTC (heat transfer coefficient) profiles as well as spanwise and streamwise averaged HTC plots are displayed for both pin arrays. The thermal performance was calculated for each pin set and Reynolds number. All experiments were carried out in a channel with an X/D of 1.72, a Y/D of 2.0, and a Z/D of 1.72.

Local Heat Transfer Coefficients and Pressure Drop During Evaporation in a Smooth Horizontal Tube

2002 ◽  
Author(s):  
C. Aprea ◽  
A. Greco ◽  
G. P. Vanoli
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Local Heat ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

R22 is the most widely employed HCFC working fluid in vapour compression plant. HCFCs must be replaced within 2020. Major problems arise with the substitution of the working fluids, related to the decrease in performance of the plant. Therefore, extremely accurate design procedures are needed. The relative sizing of each of the components of the plant is crucial for cycle performance. For this reason, the knowledge of the new fluids heat transfer characteristics in condensers and evaporators is required. The local heat transfer coefficients and pressure drop of pure R22 and of the azeotropic mixture R507 (R125-R143a 50%/50% in weight) have been measured during convective boiling. The test section is a smooth horizontal tube made of a with a 6 mm I.D. stainless steel tube, 6 m length, uniformly heated by Joule effect. The effects of heat flux, mass flux and evaporation pressure on the heat transfer coefficients are investigated. The evaporating pressure varies within the range 3 ÷10 bar, the refrigerant mass flux within the range 200 ÷ 1000 kg/m2s, the heat flux within 0 ÷ 44 kW/m2. A comparison have been carried out between the experimental data and those predicted by means of the most credited literature relationships.

Evaporation Heat Transfer and Pressure Drop in Horizontal Tubes With Strip-Type Inserts Using Refrigerant 600a

1999 ◽  
Vol 122 (2) ◽  
pp. 387-391 ◽  
Author(s):  
S.-S. Hsieh ◽  
K.-J. Jang ◽  
Y.-C. Tsai
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Pressure Drops ◽  
Horizontal Tubes ◽  
Evaporation Heat

Results of a study on saturated boiling heat transfer of refrigerant R-600a in horizontal tubes (ID=10.6 mm) with strip-type inserts (longitudinal strip LS with/without perforated holes and cross-strip CS inserts) are reported. Local heat transfer coefficients are measured for a range of heat flux (9.1∼31.2 kW/m2), mass velocity (8.23∼603.3 kg/m2s), and equilibrium mass quality (⩽0.8) and the influences were studied. The data were compared with the performance of the corresponding smooth tubes. Enhancement factors are presented and discussed. Pressure drop measurement was also conducted and it is found that both single-phase and two-phase pressure drops increase with increasing heat flux levels and mass velocities. [S0022-1481(00)00302-9]

Investigation of Endwall Heat Transfer in Staggered Pin Fin Arrays

2020 ◽  
Author(s):  
Marcel Otto ◽  
Gaurav Gupta ◽  
Patrick Tran ◽  
Shinjan Ghosh ◽  
Jayanta Kapat
Keyword(s):  
Heat Transfer ◽  
Maximum Velocity ◽  
Local Heat Transfer ◽  
Horseshoe Vortex ◽  
Local Heat ◽  
Channel Length ◽  
Thermochromic Liquid Crystal ◽  
Transfer Coefficients ◽  
Vortical Structures ◽  
Pin Fins

Abstract Arrays of staggered pin fins are a typical geometry found in the trailing edge region of modern airfoils. If coolant is supplied by bleeding from the mid-section of the airfoil instead of provided through the root, the channel length is not long enough to reach a fully developed flow which is commonly found from the fifth row downstream. This present study focuses on the developing section (four rows) of a staggered array with a height to diameter ratio of 2 and a spanwise and streamwise spacing of 2.5 respectively. Measurements are conducted at two Reynolds numbers of 10,000 and 30,000 based on the maximum velocity and pin diameter. Stereoscopic PIV is used to describe the flow field and turbulence characteristics in the wake of the first and third row pin. It is found that the dominating vortical structures depend highly on the Reynolds number. A transient thermochromic liquid crystal technique is used to obtain local heat transfer coefficients on the endwall which are then discussed in the context with the vortical structures. The structure of the horseshoe vortex and the transient wake shedding behave differently in the first and second row. The interaction of both vortex systems affects directly the endwall heat transfer. The results are supplemented by a thorough discussion of TLC and PIV uncertainty.

Local and Average Heat Transfer and Pressure Drop for Refrigerants Evaporating in Horizontal Tubes

1960 ◽  
Vol 82 (3) ◽  
pp. 189-196 ◽  
Author(s):  
M. Altman ◽  
R. H. Norris ◽  
F. W. Staub
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Test Facility ◽  
Transfer Coefficients ◽  
Local Pressure ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

A test facility is described that has been constructed to investigate local heat transfer and pressure drop for evaporating or condensing refrigerants. The empirical method of B. Pierre [1] for correlating the average heat-transfer coefficients of refrigerants evaporating in horizontal tubes is presented in conjunction with the data of several authors [3–6]. Data on local heat-transfer coefficients and pressure drop are presented for Refrigerant-22 evaporating in two 4-ft-long, 0.343-in-ID straight horizontal tubes, and are correlated by a refinement of the curve proposed in [1]. The procedure of Martinelli-Nelson [9] correlated the data for local pressure drop within 15 per cent.

Experimental Heat Transfer for Gas-Liquid Vertical Flow inside Pipe

2011 ◽  
Vol 90-93 ◽  
pp. 1667-1670 ◽  
Author(s):  
Huan Qun Qian ◽  
Chang Yong Wang
Keyword(s):  
Heat Transfer ◽  
Flow Pattern ◽  
High Speed ◽  
Local Heat Transfer ◽  
Ccd Camera ◽  
Local Heat ◽  
Circulation System ◽  
Vertical Flow ◽  
Transfer Coefficients ◽  
Forced Circulation

Experiments have been performed to observe flow pattern and investigate convective heat transfer for air-water vertical flow in a forced circulation system. The bubbles motion was recorded by a high-speed CCD camera. For the bubble and slug flow pattern, the temperature fluctuation signals and local heat transfer coefficients were obtained in a short heated tube. The probability density function classical was applied to analyze the temperature. The results qualitatively reflected characteristics of local heat transfer in two phase flow comparing with that in single-phase liquid. The comparison revealed that the gas phase could enhance the heat transfer.

Supercritical Heat Transfer and Pressure Drop in Refrigerant R410A

2003 ◽  
Author(s):  
Biswajit Mitra ◽  
Srinivas Garimella
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Cooling Water ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Coolant Temperature ◽  
Transfer Coefficients ◽  
Water Stream

This paper presents the results of an experimental study on heat transfer and pressure drop at critical and supercritical pressures of refrigerant R410A inside a horizontal 9.4 mm I.D. tube. Knowledge of heat transfer and pressure drop in such refrigerants blends at elevated pressures is gaining increasing attention for the design of vapor-compression space-conditioning and water heating systems at high heat rejection temperatures. Local heat transfer coefficients and pressure drops were measured for the mass flux range 200 < G < 800 kg/m2-s for the temperature range from 30–110°C. A technique that simultaneously allows accurate measurement of low local heat duties and deduction of the tube-side heat transfer coefficient from the measured overall resistance was used. A primary cooling loop using water at high flow rates ensures that the refrigerant side presents the governing thermal resistance. Heat exchange with a secondary cooling water stream at a much lower flow rate amplifies the coolant temperature difference, which in turn enables accurate heat duty measurements. The results show that the heat transfer coefficient exhibits a sharp peak in the vicinity of the vapor-liquid dome. These data are compared with the most relevant correlations from the literature and possible explanations for agreement and discrepancies between the data and predictions are provided.

Heat Transfer Experiments and Flow Visualization for Arrays of Short Pin Fins

1982 ◽  
Author(s):  
D. E. Metzger ◽  
S. W. Haley
Keyword(s):  
Heat Transfer ◽  
Flow Visualization ◽  
Large Scale ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Internal Cooling ◽  
Additional Information ◽  
Pin Fins ◽  
Scale Test ◽  
Turbine Airfoils

Results from several sets of experiments are presented to illustrate the character of streamwise heat transfer development in large aspect ratio ducts filled with uniform staggered arrays of circular pins. The short (height-to-diameter ratio 1.0) pins span the full height of the duct and are packed in moderately dense arrays (pitch-to-diameter ratios 1.32 to 2.5) typical of internal cooling applications in gas turbine airfoils. Heat transfer experiments have been performed on two separate test sections utilizing (i) highly conducting, fin effectiveness unity pins, and (ii) low conductivity, fin effectiveness near zero pins. In both cases the streamwise development of heat transfer, averaged across the duct width, is resolved to a single pin row spacing. Additional information on the flowfield and local heat transfer is provided from a large scale test rig where kerosene-lamp black flow visualization and small heat flux gages were utilized.

Heat Transfer on Convective Surfaces With Pin-Fins Mounted in Inclined Angles

2007 ◽  
Author(s):  
M. K. Chyu ◽  
E. O. Oluyede ◽  
H.-K. Moon
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Casting Process ◽  
Local Heat ◽  
Test Model ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Pin Fins ◽  
Inclined Angle

Casting of pin fins at the trailing edge of the turbine blades often presents some difficulties due to tight dimensional tolerances, leaving the pin fins inclined after the casting process. This study is to experimentally examine the effects of such an imperfect manufacturing phenomena on the heat transfer and friction characteristics over pin-fin arrays with different pin inclinations. The test model is a staggered short (H/D = 1) pin-fin array with an inter-pin spacing of 2.5 times the pin-diameter (S/D = 2.5) in both longitudinal and transverse directions. Detailed local heat transfer coefficients on both array endwalls and pin elements are determined using the transient liquid crystal technique, as the inclined angle θ varies from 40° to 90° and the Reynolds number ranges from 7.0 × 103 and 1.3 × 104. The measured data suggest that an increase in pin inclined angle relative to its normal orientation (90-degree) significantly reduces the level of heat transfer enhancement from the array. Such a reduction amounts to nearly 50% for the 40-degree case. The accompanied friction loss also decreases.

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