A Generalized Prediction of Heat Transfer Surfaces

1974 ◽  
Vol 96 (4) ◽  
pp. 511-517 ◽  
Author(s):  
P. G. LaHaye ◽  
F. J. Neugebauer ◽  
R. K. Sakhuja
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Power Factor ◽  
Heat Transfer Performance ◽  
Rapid Assessment ◽  
Transfer Performance ◽  
Pumping Power ◽  
Transfer Data ◽  
Turbulent Flow Regime ◽  
Flow Length

A new way of presenting the heat transfer data is shown. This leads to a dimensionless performance plot between a “heat transfer performance factor” and a “pumping power factor” with a nondimensional “flow length between major boundary layer disturbances” as a varying parameter. This approach leads to the possibility of approximately presenting all surface geometries on a single “idealized” performance plot, the nondimensional “flow length” being a geometrical characteristic of each surface. The method can be used to predict approximately the heat transfer performance characteristics of a new, untested surface. The plot permits the rapid assessment and comparison of various heat transfer geometries for a given application. The performance plot is valid only in the turbulent flow regime. The method will prove invaluable in optimizing a design accounting for space limitations, economic restraints, and system considerations such as pumping power and effectiveness tradeoffs.

An Evaluation of the Application of Nanofluids in Intercooled Cycle Marine Gas Turbine Intercooler

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Ningbo Zhao ◽  
Xueyou Wen ◽  
Shuying Li
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Gas Turbine ◽  
Heat Transfer Performance ◽  
Volume Concentration ◽  
Inlet Temperature ◽  
Transfer Performance ◽  
Pumping Power ◽  
Flow And Heat Transfer ◽  
Overall Performance

Coolant is one of the important factors affecting the overall performance of the intercooler for the intercooled (IC) cycle marine gas turbine. Conventional coolants, such as water and ethylene glycol, have lower thermal conductivity which can hinder the development of highly effective compact intercooler. Nanofluids that consist of nanoparticles and base fluids have superior properties like extensively higher thermal conductivity and heat transfer performance compared to those of base fluids. This paper focuses on the application of two different water-based nanofluids containing aluminum oxide (Al2O3) and copper (Cu) nanoparticles in IC cycle marine gas turbine intercooler. The effectiveness-number of transfer unit method is used to evaluate the flow and heat transfer performance of intercooler, and the thermophysical properties of nanofluids are obtained from literature. Then, the effects of some important parameters, such as nanoparticle volume concentration, coolant Reynolds number, coolant inlet temperature, and gas side operating parameters on the flow and heat transfer performance of intercooler, are discussed in detail. The results demonstrate that nanofluids have excellent heat transfer performance and need lower pumping power in comparison with base fluids under different gas turbine operating conditions. Under the same heat transfer, Cu–water nanofluids can reduce more pumping power than Al2O3–water nanofluids. It is also concluded that the overall performance of intercooler can be enhanced when increasing the nanoparticle volume concentration and coolant Reynolds number and decreasing the coolant inlet temperature.

Microflow Heat Transfer Effectiveness: Questioning the “Area/Volume-Argument”

2011 ◽  
Author(s):  
Heinz Herwig
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Steady State ◽  
Thermal Boundary Layer ◽  
Heat Transfer Performance ◽  
Characteristic Length ◽  
Transfer Performance ◽  
Layer Behavior ◽  
Steady State Heat ◽  
Steady State Heat Transfer

The often used argument that heat transfer in micro-sized devices is superior due to the fact that the transfer area scales like L2 but the volume like L3 with L as a characteristic length is critically analyzed for various heat transfer situations. It turns out that for steady state heat transfer cases the thermal boundary layer behavior is more important. In general, dimensional analysis should be applied to understand how the heat transfer performance changes when scales are reduced from macro- to micro-size.

Heat Transfer Performance of an Air-Assisted Impinging Water Jet Under a Fixed Pumping Power Constraint

2013 ◽  
Author(s):  
Daniel Trainer ◽  
Sung Jin Kim
Keyword(s):  
Heat Transfer ◽  
Flow Pattern ◽  
Heat Transfer Performance ◽  
Plug Flow ◽  
Water Jet ◽  
Air Injection ◽  
Transfer Performance ◽  
Pumping Power ◽  
Two Phase ◽  
Impingement Point

Air injection into a liquid impinging jet has been shown to be a method of improving non-phase change heat transfer rates by up to twice the normal amount. Previous work has shown that there exists an optimal operating point in terms of the volumetric fraction of air injection when the pumping power is held constant because of an optimal two-phase flow pattern. However, previous work focused on heat transfer from the impingement point only, and neglected performance at other points. The present work studies the local heat transfer performance of an air-assisted water jet, at the impingement point and at positions moving radially outward, under constant pumping power conditions. The area-averaged heat transfer is also considered. Heat transfer at the stagnation point is shown to be optimized between β = 0.1∼0.2, where a bubbly flow pattern exists. Nuavg(r/D ≤ 1) is optimized when the flow pattern was plug-flow and off-center peaks in Nur exist. Nuavg(r/D > 1) is optimized when the water is accelerated by the injected air, but splattering is avoided. Flow patterns have no direct effect outside the impingement region.

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