The Heat Transfer and Pressure-Drop Characteristics of Gas Flow Inside Spirally Corrugated Tubes

1970 ◽  
Vol 92 (3) ◽  
pp. 513-518 ◽  
Author(s):  
G. J. Kidd
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Gas Flow ◽  
Pumping Power ◽  
Friction Factors ◽  
Apparent Correlation ◽  
Smooth Tubes ◽  
Enhancing Heat Transfer

Heat transfer and pressure-drop experiments have been performed for gas flow inside nine, 1/2-in-OD, 0.035-in. wall thickness, A-nickel, spirally corrugated tubes. The corrugations, which varied from 0.003–0.028 in. deep, were formed by pulling the tubes through a rotating head containing four embossing tools; corrugation-spacing-to-corrugation-depth ratios (P/e) ran from 16–41. The data, for heat transfer to nitrogen, at approximately 200 psig, were correlated by an expression of the form NNu,B (NPr,B)−0.4 × (Tw/TB)0.5 = A(NRe,B)m, where all the physical properties were evaluated at bulk gas conditions. The exponent, m, on the Reynolds number was observed to be consistently greater (0.854–0.900) than the value of 0.8 found for smooth tubes; the constant, A, varied from 0.0095–0.0195 with no apparent correlation with P/e. Friction factors, measured with adiabatic airflow, were found to be up to 1.7 times that for smooth tubes. Tubes of this geometry were found to be very effective in enhancing heat transfer. On an equal pumping power basis, for example, a tube with P/e = 22 had a heat transfer coefficient 22 percent greater than a smooth tube.

Single-Phase Heat Transfer and Pressure Drop of Water Cooled Inside Horizontal Smooth Tubes in the Transitional Flow Regime

2010 ◽  
Author(s):  
Josua P. Meyer ◽  
Leon Liebenberg ◽  
Jonathan A. Olivier
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Transition Region ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Transitional Flow ◽  
Working Fluid ◽  
Tube Heat Exchanger ◽  
Smooth Tubes

Heat exchangers are usually designed in such a way that they do not operate in the transition region. This is usually due to a lack of information in this region. However, due to design constraints, energy efficiency requirements or change of operating conditions, heat exchangers are often forced to operate in this region. It is also well known that entrance disturbances influence where transition occurs. The purpose of this paper is to present experimental heat transfer and pressure drop data in the transition region for fully developed and developing flows inside smooth tubes using water as the working fluid. The use of different inlet disturbances were used to investigate its effect on transition. A tube-in-tube heat exchanger was used to perform the experiments, which ranged in Reynolds numbers from 1 000 to 20 000, with Prandtl numbers being between 4 and 6 while Grashof numbers were in the order of 105. Results showed that the type of inlet disturbance could delay transition to a Reynolds number as high as 7 000, while other inlets expedited it, confirming results of others. For heat transfer, though, it was found that transition was independent of the inlet disturbance and all commenced at the same Reynolds number, 2 000–3 000, which was attributed to secondary flow effects.

Experimental Investigation of Crossflow Diverters in Jet Impingement Cooling

2019 ◽  
Author(s):  
Srivatsan Madhavan ◽  
Kishore Ranganath Ramakrishnan ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Turbine Blades ◽  
Jet Impingement ◽  
Target Surface ◽  
Pumping Power ◽  
Detailed Measurement ◽  
To Come

Abstract Jet impingement is a cooling technique commonly employed in combustor liner cooling and high-pressure gas turbine blades. However, jets from upstream impingement holes reduce the effectiveness of downstream jets due to jet deflection in the direction of crossflow. In order to avoid this phenomenon and provide an enhanced cooling on the target surface, we have attempted to come up with a novel design called “crossflow diverters”. Crossflow diverters are U-shaped ribs that are placed between jets in the crossflow direction (under maximum crossflow condition). In this study, the baseline case is jet impingement onto a smooth surface with 10 rows of jet impingement holes, jet-to-jet spacing of X/D = Y/D = 6 and jet-to-target spacing of Z/D = 2. Crossflow diverters with thickness ‘t’ of 1.5875 mm, height ‘h’ of 2D placed in the streamwise direction at a distance of X = 2D from center of the jet have been investigated experimentally. Transient liquid crystal thermography technique has been used to obtain detailed measurement of heat transfer coefficient for four jet diameter based Reynolds numbers of 3500, 5000, 7500, 12000. It has been observed that crossflow diverters protect the downstream jets from upstream jet deflection thereby maximizing their stagnation cooling potential. An average of 15–30% enhancement in Nusselt number is obtained over the flow range tested. However, this comes at the expense of increase in pumping power. Pressure drop for the enhanced geometry is 1–1.5 times the pressure drop for baseline impingement case. At a constant pumping power, crossflow diverters produce 9–15% enhancement in heat transfer coefficient as compared to baseline smooth case.

Experimental study of the heat transfer coefficient and pressure drop of R1234yf condensing flow in flattened smooth tubes

2019 ◽  
Vol 106 ◽  
pp. 120-132 ◽  
Author(s):  
Hamidreza Fazelnia ◽  
Behrang Sajadi ◽  
Soorena Azarhazin ◽  
Mohammadali Akhavan Behabadi ◽  
Sajjad Zakeralhoseini
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Smooth Tubes ◽  
The Heat Transfer Coefficient

Experimental Study on Heat Transfer Characteristics and Pressure Drops for Water Flowing in Spiral Coil Heat Exchanger

2013 ◽  
Vol 732-733 ◽  
pp. 593-599
Author(s):  
Xiao Yan Zhang ◽  
Fang Fang Jiang ◽  
Shan Yuan Zhao ◽  
Wen Fei Tian ◽  
Xiao Hang Chen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Resistance Coefficient ◽  
Heating Power ◽  
Average Heat Transfer Coefficient ◽  
Spiral Coil ◽  
Pressure Drops ◽  
Average Heat

The heat transfer and pressure drop characteristics for water flowing in four spiral coils with different shapes and different sizes were experimental studied. Reynolds number range from 4000 to 9000, volume flow rate range from 200 to 350 L/h and heating power range from 80-350 W. Based on the experimental results, the regularity of Reynolds number and heating power influencing on heat transfer and pressure drop characteristics was analyzed and discussed. The results indicate: the Nu increases with increasing Re, the greatest average heat transfer coefficient appears in the smaller circular spiral coil. The heat transfer coefficients increase with increasing heating power, the greatest average heat transfer coefficient also appears in the smaller circular spiral coil. The pressure drops increase with increasing Re, the pressure drop in big ellipse spiral coil is greatest. The resistance coefficients gradually decrease with increasing Re. The resistance coefficient of small circular spiral coil is always greatest, and the resistance coefficient of big circular spiral coil is smallest.

Heat Transfer and Pressure Drop for Short Pin-Fin Arrays With Pin-Endwall Fillet

1990 ◽  
Vol 112 (4) ◽  
pp. 926-932 ◽  
Author(s):  
M. K. Chyu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Circular Cylinders ◽  
Significant Finding ◽  
Array Configuration ◽  
Pin Fin ◽  
Pin Fin Arrays

The effects of array configuration and pin-endwall fillet on the heat transfer and pressure drop of short pin-fin arrays are investigated experimentally. The pin-fin element with endwall fillet, typical in actual turbine cooling applications, is modeled by a spool-like cylinder. The arrays studied include an in-line and a staggered array, each having seven rows of five pins. These arrays have the same geometric parameters, i.e., H/D = 1, S/D = X/D = 2.5, and the Reynolds number ranging from 5 × 103 to 3 × 104. One of the present results shows that the staggered array always has a higher array-averaged heat transfer coefficient than its in-line counterpart. However, the pressure drop for the staggered array is higher compared to the in-line configuration. These trends are unaffected by the existence of the pin-endwall fillet. Another significant finding is that an array with pin-endwall fillet generally produces lower heat transfer coefficient and higher pressure drop than that without endwall fillet. This leads to the conclusion that pin-endwall fillet is undesirable for heat transfer augmentation. In addition, nai¨ve use of the heat transfer results obtained with perfectly circular cylinders tends to overestimate the pin-fin cooling capability in the actual turbine. The effects of endwall fillet on the array heat transfer and pressure drop are much more pronounced for the staggered array than for the inline array; however, they diminish as the Reynolds number increases.

Design Optimisation of Finned Channel

2009 ◽  
Author(s):  
K. M. C. Seakher ◽  
L. S. S. Prakash Kumar ◽  
K. S. R. Kali Prasad ◽  
K. H. Manasa ◽  
A. Siva Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Dissipation ◽  
Pumping Power ◽  
Transfer Enhancement ◽  
Power Requirement ◽  
Smooth Channel ◽  
Fin Length

A finned channel has a higher heat transfer coefficient compared to a smooth channel and the increase in this fin height enhances the heat transfer. But this heat transfer enhancement is accompanied by an increase in pressure drop for a series of fins. This requires an increase in pumping power requirement, indicating that there exists an optimum design or length of the fin at which the heat dissipation is maximum. The objective of this paper is to observe the variation of heat transfer with varying sizes of fins. The effect of fin dimensions on heat transfer can be clearly seen in its performance, which is discussed in the paper. The results are obtained by analytical analysis, and some illustrations are dealt with in the paper, which clearly determine the importance of this factor of optimal fin length.

scholarly journals CFD Analysis on the Air-Side Thermal-Hydraulic Performance of Multi-Louvered Fin Heat Exchangers at Low Reynolds Numbers

2017 ◽  
Author(s):  
Arslan Saleem ◽  
Man-Hoe Kim
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Reynolds Numbers ◽  
Hydraulic Performance

The air side thermal hydraulic performance of multi-louvered aluminium fin heat exchangers is investigated. A detailed study was performed to analyse the thermal performance of air over a wide range of Reynolds number i.e. from 30 to 250. Air-side heat transfer coefficient and air pressure drop were calculated and validated over the mentioned band of Reynolds numbers. Critical Reynolds number was determined numerically and the variation in flow physics along with the thermal and hydraulic performance of microchannel heat exchanger associated with R_cri has been reported. Moreover, a parametric study of the multi-louvered aluminium fin heat exchangers was also performed for 36 heat exchanger configurations with the louver angles (19-31°), fin pitches (1.0, 1.2, 1.4 mm) and flow depths (16, 20, 24 mm); and the geometric configuration exhibiting the highest thermal performance was reported. The air-side heat transfer coefficient and pressure drop results for different geometrical configurations were presented in terms of Colburn j factor and Fanning friction factor f, as a function of Reynolds number based on louver pitch.

scholarly journals Investigation on Heat Transfer and Pressure Drop Performance Utilizing GNP-based Colloidal Suspension Flow in Finned Conduit

2021 ◽  
Vol 945 (1) ◽  
pp. 012056
Author(s):  
Yanru Wang ◽  
Cheen Sean Oon ◽  
Manh-Vu Tran ◽  
Joshua Yap Kee An
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Colloidal Suspension ◽  
Convective Heat Transfer Coefficient ◽  
Constant Heat Flux

Abstract Heat exchangers have been widely used in various engineering applications. It is important to develop a highly efficient heat transfer equipment to reduce carbon footprint. In the current research, the effect of 0.025wt% CGNP/water nanofluid on convective heat transfer and pressure drop performance is investigated numerically in finned conduits with circular and square geometry. ANSYS FLUENT is used to analyze the turbulent flow inside the conduits with Reynolds number ranging from 7360 to 28011 and constant heat flux 12254.90W/m2 and 9615.38W/m2 in circular and square geometry, respectively. Only 1/8 of the pipe was constructed in the simulation as the geometry is symmetrical. The numbers of mesh elements are 465488 and 469144 for circular and square conduits. SST k-omega viscous model, SIMPLEC scheme and second-order upwind solvers are used in this model, where SST k-omega viscous model is good at solving turbulence parameters in the near wall boundary regions. It is found that the use of CGNP/water nanofluid can increase convective heat transfer coefficient without increasing pressure drop compared with water. Besides, the circular pipe shows higher heat transfer enhancement compared with square pipe. Furthermore, the increase in Reynolds number enhances the Nusselt number and heat transfer coefficient in both circular and square geometries. It is recommended that circular finned pipe and CGNP/water colloidal suspension could be applied in low turbulence flow setting heat exchanger.

Sign in / Sign up

Export Citation Format

Share Document