Overall Thermal Performance of a Rectangular Channel With an Array of Elongated Pedestals

2013 ◽  
Author(s):  
S. Huang ◽  
Y. Y. Yan ◽  
J. D. Maltson ◽  
E. Utriainen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Rectangular Channel ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Flow Area ◽  
Coefficient Distribution

Experiments have been conducted to investigate the overall thermal performance of a rectangular channel implemented with an elongated pedestal array. The staggered pedestals were elongated in the spanwise direction in order that the jet flow from between the pedestals impinges at the centre of the pedestals in the downstream row. The average heat transfer coefficient of the pedestal and the local heat transfer coefficient distribution of the bottom channel wall were investigated for different geometrical arrangements. The pressure drop across the pedestal bank was measured. The transient liquid crystal method was used to obtain the local heat transfer coefficient distribution on the bottom channel wall and the lumped capacitance method was used to measure the average heat transfer coefficient of the pedestals in the last two rows of the bank. Five pressure taps were arranged on the centerline of each gap between two pedestal rows to measure the pressure drop. The heat transfer coefficients were measured over the Reynolds number range from 10,000 to 30,000. The minimum flow area to the channel cross-section flow area ratio ranged from 0.149 to 0.333. The effects of pedestal geometry and array distribution were investigated in detail showing the relationship between the pedestal array geometry, heat transfer enhancement and pressure drop. Conclusions were drawn on the effects of geometry and flow conditions on overall thermal performance of the respective channels.

Experimental Study on Flow Boiling of HFC134a in a Multi-Port Extruded Tube

2004 ◽  
Author(s):  
Ken Kuwahara ◽  
Shigeru Koyama ◽  
Kengo Kazari
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Rectangular Channel ◽  
Large Diameter ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Inlet Temperature

In the present study, the local heat transfer and pressure drop characteristics are investigated experimentally for the flow boiling of refrigerant HFC134a in a multi-port extruded tube of 1.06mm in hydraulic diameter. The test tube is 865mm in total length made of aluminum. The pressure drop is measured at an interval of 191 mm, and the local heat transfer coefficient is measured in every subsection of 75mm in effective heating length. Experimental ranges are as follows: the mass velocity of G = 100–700 kg/m2s, the inlet temperature of Tin = 5.9–11.4 °C and inlet pressure of about 0.5 MPa. The data of pressure drop are compared with a few previous correlations for small diameter tubes, and the correlations can predict the data relatively good agreement. The data of heat transfer coefficient is compared with the correlations of Yu et al. proposed for relatively large diameter tubes. It is found that there are some differences about two phase multiplier factor of convective heat transfer between the circular channel and rectangular channel.

scholarly journals Local Heat Transfer and Pressure Drop in a Rotating Two-Pass Ribbed Rectangular Channel

2001 ◽  
Vol 7 (3) ◽  
pp. 183-194 ◽  
Author(s):  
Shou-Shing Hsieh ◽  
Hsiu-Cheng Liao
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Transfer Coefficient ◽  
Rectangular Channel ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Uneven Heating

The influences of rotation and uneven heating condition as well as passage aspect ratio on the local heat transfer coefficient and pressure drop in a rotating, two pass ribroughened (rib heighte/DH≈0.27; rib pitchp/e=8) rectangular channel with a crosssection aspect ratio of 3 was studied for Reynolds numbers from 5000 to 25,000 and rotation numbers from 0 to 0.24. Regionally averaged Nusselt number variations along the duct have been determined over the trailing and leading surfaces for two pass straight channels and U-bend region. Implementing with the data from Hsieh and Liu (1996) forAR=1and 1.5 withp/e=5ande/DH=0.17and 0.20, passage aspect ratio effect was further examined. Furthermore, data for180∘U-bend region with ribroughened turbulator on heat transfer were also measured. It was found that a complicated three-dimensional accelerated flow and secondary flow in this U-bend region caused higher heat transfer on both leading/trailing walls. Enhancement performance ratios are also presented and discussed. Results again indicate a slight decrease in heat transfer coefficient for an increase in passage aspect ratio as compared to those of previous studies.

Investigation of Heat Transfer Characteristics of Supercritical Carbon Dioxide at Microchannels

2019 ◽  
Author(s):  
Mostafa Asadzadeh ◽  
Anatoly Parahovnik ◽  
Stephen Adeoye ◽  
Yoav Peles
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Supercritical Co2 ◽  
Local Heat Transfer ◽  
Local Heat ◽  
System Pressure ◽  
Micro Channels

Abstract Carbon Dioxide (SCO2) can revolutionize the thermal management landscape due to a dramatic increase in enthalpy and a specific heat near supercritical state, particularly along the pseudocritical line, which correspond to much lower temperatures and pressures than water and other refrigerants. This study is conducted to assess the capability of supercritical CO2 in heat transfer applications. The heat transfer coefficient of carbon dioxide near the pseudocritical conditions was experimentally studied at the micro scale. Devices with 20 micro channels were fabricated to measure local and average heat transfer coefficient as well as system pressure drop. The experimental results showed a significant increase up to 72000 W/m2.k in local heat transfer coefficient and large pressure drop up to 3 MPa at microscale with supercritical CO2.

Numerical Simulation on Forced Convection Heat Transfer Performance and Pressure Drop of High Permeability Porous Media

2016 ◽  
Author(s):  
Shigeki Hirasawa ◽  
Tsuyoshi Kawanami ◽  
Katsuaki Shirai
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Air Flow ◽  
Convection Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Convection Heat

We studied the forced convection heat transfer performance and pressure drop of high permeability metal cellular porous media in air flow using a 3-dimensional thermofluid computation code. The temperature and velocity distributions in the air flow region, local heat transfer coefficient, and local heat flux on the surface of the porous media were numerically calculated for steady air flow by changing the parameters of the pore size and air velocity. The cellular porous media were modeled by pin array, cube geometry, and truncated octahedron geometry using thin wires. The diameter of the wires was 0.1 mm, and the pore per inch (PPI) was 5–50. The relations between the Nusselt number using the volumetric heat transfer coefficient and the Reynolds number were obtained from our calculation results, and we compared them with conventionally proposed experimental correlations. Also, the pressure drop calculation result was compared with conventionally proposed experimental correlations. The following results were obtained. The local heat transfer coefficient and local heat flux on the surface of porous media were small near the joint positions of the wires of the cellular porous media because of the thermal boundary layer. The volumetric heat transfer coefficient and pressure drop agreed with conventionally proposed experimental correlations within errors of twice the volumetric heat transfer coefficient and pressure drop. The relation between the heat transfer rate per unit volume and the heat transfer area per unit volume agreed with the convection heat transfer correlation for a tube bundle.

Local Heat Transfer Coefficient Distribution With Air Impingement Into a Cavity

1972 ◽  
Author(s):  
F. Burggraf
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Impinging Jets ◽  
Local Heat Transfer Coefficient ◽  
Cavity Surface ◽  
Transfer Coefficients ◽  
Coefficient Distribution

Impingement heat transfer coefficients are presented for a row of holes impinging into an oval cavity with the spent air leaving through holes on one or both sides of the cavity. The distribution around the cavity surface is obtained and is correlated with a survey of the recent literature. In addition, local heat flux gages were used with an impingement jet air supply which could be changed in location along the axis of the test section. This permitted the determination of local heat transfer coefficient distribution over the surface both around the cavity and also in the region between the impinging jets. This two-dimensional distribution is shown to be influenced by the bleed geometry and the shape of the impinging jet holes.

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