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.

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.

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.

Three-Dimensional Transient Heat Conduction Equation Solution for Accurate Quantification of Heat Transfer Coefficient in Transient Liquid Crystal Experiments

2019 ◽  
Author(s):  
Shoaib Ahmed ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Crystal ◽  
Transfer Coefficient ◽  
Three Dimensional ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Conduction Model

Abstract Liquid crystal thermography and infrared thermography techniques are typically employed to measure detailed surface temperatures, where local heat transfer coefficient (HTC) values are calculated by employing suitable conduction models. One such practice, which is very popular and easy to use, is the transient liquid crystal thermography using one-dimensional semi-infinite conduction model. In these experiments, a test surface with low thermal conductivity and low thermal diffusivity (e.g. acrylic) is used where a step-change in coolant air temperature is induced and surface temperature response is recorded. An error minimization routine is then employed to guess heat transfer coefficients of each pixel, where wall temperature evolution is known through an analytical expression. The assumption that heat flow in the solid is essentially in one-dimension, often leads to errors in HTC determination and this error depends on true HTC, wall temperature evolution and HTC gradient. A representative case of array jet impingement under maximum crossflow condition has been considered here. This heat transfer enhancement concept is widely used in gas turbine leading edge and electronics cooling. Jet impingement is a popular cooling technique which results in high convective heat rates and has steep gradients in heat transfer coefficient distribution. In this paper, we have presented a procedure for solution of three-dimensional transient conduction equation using alternating direction implicit method and an error minimization routine to find accurate heat transfer coefficients at relatively lower computational cost. The HTC results obtained using 1D semi-infinite conduction model and 3D conduction model were compared and it was found that the heat transfer coefficient obtained using the 3D model was consistently higher than the conventional 1D model by 3–16%. Significant deviations, as high as 8–20% in local heat transfer at the stagnation points of the jets were observed between h1D and h3D.

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.

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.

Uneven Wall Heat Flux Effect on Local Heat Transfer in Rotating Two-Pass Channels With Two Opposite Ribbed Walls

1996 ◽  
Vol 118 (4) ◽  
pp. 864-876 ◽  
Author(s):  
Shou-Shing Hsieh ◽  
Wei-Jen Liu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Secondary Flows ◽  
Fluid Temperature ◽  
Bulk Fluid ◽  
Aspect Ratios ◽  
Uneven Heating

The influence of rotation and uneven heating condition on the local heat transfer coefficient in rotating, two-pass rib-roughened (rib height e/DH ≈ 0.17 − 0.20; rib pitch p/e = 5) rectangular channels with cross-sectional aspect ratios of 1 and 1.5 were studied for Reynolds numbers from 5000 to 25,000 and rotation numbers from 0 to 0.6152. Regionally averaged Nusselt number variations along the duct have been determined over the trailing and leading surfaces for two pass channels. In general, Coriolis-induced secondary flows are shown to enhance local heat transfer over the trailing (leading) surface in the first (second) pass compared to a duct without rotation. Centrifugal buoyancy is shown to influence the heat transfer response with heat transfer being imposed on both leading and trailing surfaces as the wall-to-bulk fluid temperature difference is increased with other controlling parameters fixed. Results also indicate a slight decrease in heat transfer coefficient for an increase in passage aspect ratio. Results are compared with previous studies. It is found that the results agree quite well with those reported by other works for two-pass flow channels.

The Characteristics of Heat Transfer and Flow on a Surface With Small Scale V-Shape Groove

2009 ◽  
Author(s):  
Jiansheng Wang ◽  
Zhiqin Yang
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Coherent Structure ◽  
Rectangular Channel ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Small Scale

The characteristics of heat transfer and flow in a rectangular channel with bottom of scale groove were investigated with numerical method. The numerical calculation was performed with large eddy simulation. A variety of small scale V-shapes groove with different of depth and space in longitudinal were employed in numerical simulation. The coherent structure near the surface of small scale groove was studied. The effect of the depth and space in longitudinal of small scale groove on coherent structure was investigated. Furthermore, the relationship between coherent structure and local heat transfer coefficient was investigated as well as. The numerical results indicate that the heat transfer performance of channel with small scale groove has been improved and the drag reduction has been gained in some case. The numerical simulation indicated that flow structure in different area of small scale groove had obvious difference and it would cause influence on local heat transfer coefficient.

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