Investigation of the Variation of Point Unit Heat-Transfer Coefficients for Laminar Flow Over an Inclined Flat Plate

1949 ◽  
Vol 16 (1) ◽  
pp. 1-8
Author(s):  
R. M. Drake
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Flat Plate ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Specific Rate ◽  
Angle Of Incidence ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Full Explanation

Abstract Many applications of heat-transfer phenomena by forced convection require a knowledge of heat transfer from simple geometric bodies like the flat plate. Investigations of the flat plate have been limited, in general, to studies of isothermal plates of 0-deg angle of incidence and in laminar flow. The amount of data concerning investigations on turbulent flow, nonisothermal plates or inclined plates is quite small. It is the intent of this paper to provide information on the heat transfer from a nonisothermal inclined flat plate in laminar flow. It is shown herein that forced-convection heat-transfer data for an inclined nonisothermal flat plate with a constant specific rate of heat flow can be correlated and represented by an equation of the type (1)NuxReL=C(xL)n for laminar flow. It is further shown that this equation is similar in slope to the theoretical equation of the type (2)NuxReL=C2(xL)m+12 for an isothermal plate in laminar flow, but is larger by 30 per cent in absolute value. This variance can be partly explained by an analysis of the behavior of a nonisothermal plate as opposed to an isothermal one, but this analysis leaves much to be desired, so that the full explanation is at present unknown.

A Study of Forced Convection Direct Air Cooling in the Downstream Vicinity of Heat Sinks

1990 ◽  
Vol 112 (3) ◽  
pp. 234-240 ◽  
Author(s):  
G. L. Lehmann ◽  
S. J. Kosteva
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Heat Sinks ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Packaging System ◽  
Transfer Rates ◽  
Heat Transfer Coefficients

An experimental study of forced convection heat transfer is reported. Direct air cooling of an electronics packaging system is modeled by a channel flow, with an array of uniformly sized and spaced elements attached to one channel wall. The presence of a single or complete row of longitudinally finned heat sinks creates a modified flow pattern. Convective heat transfer rates at downstream positions are measured and compared to that of a plain array (no heat sinks). Heat transfer rates are described in terms of adiabatic heat transfer coefficients and thermal wake functions. Empirical correlations are presented for both variations in Reynolds number (5000 < Re < 20,000) and heat sink geometry. It is found that the presence of a heat sink can both enhance and degrade the heat transfer coefficient at downstream locations, depending on the relative position.

Experimental Study on Transient Heat Transfer Enhancement for Helium Gas Flowing Over a Thin Twisted Plate

2014 ◽  
Author(s):  
Zhou Zhao ◽  
Qiusheng Liu ◽  
Katsuya Fukuda
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Heat Generation ◽  
Heat Input ◽  
Convection Heat Transfer ◽  
Transient Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Helium Gas ◽  
The Heat Transfer Coefficient

Transient forced convection heat transfer due to exponentially increasing heat input to a heater is important as a database for safety assessment of the transient heat transfer process in a Very High Temperature Reactor (VHTR). The knowledge of heat transfer enhancement using a heater with twisted configuration is also important for the high performance design of intermediate heater exchanger (IHX) in VHTR system. In this study, forced convection transient heat transfer for helium gas at various periods of exponential increase of heat input to a short thin twisted plate with various helix angles was experimentally studied. A forced convection heat transfer experimental apparatus was used to measure the experimental data. The test heater was mounted horizontally along the center part of a circular test channel. Twisted plates were made of thin platinum plate with a thickness of 0.1 mm and width of 2 mm and 4 mm. The heat generation rates of the heater were controlled and measured by a heat input control system. The heat generation rate, Q̇, was raised with exponential function, Q̇ = Q0exp(t/τ). Where, t is time, and τ is period of heat generation rate. The mean temperature of the test heater was measured by resistance thermometry. The heat flux was obtained by the energy conservation equation. The test heater surface temperature was calculated from heat conduction equation of the heater. The transient heat transfer experimental data were measured for the periods ranged from 80 ms to 17 s and at a gas temperature of 303 K under 500 kPa. The flow velocities ranged from 4 m/s to 10 m/s. In the experiments, the twisted plates with different width were tested. The surface temperature and heat flux are increasing exponentially with the time. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period longer than about 1 s, and it becomes higher for the period shorter than about 1 s. The heat transfer coefficients for total length of the twisted plate were compared with the values of flat plate which has the same width and thickness with the twisted one. The local mean heat transfer coefficients have been tested as well. The heat transfer coefficients of twisted plate are about 10% for 2 mm-width one and15% for 4 mm-width one higher than those of flat plate with same width at the quasi-steady state. And also, the heat transfer coefficients for the first half pitch are 24% higher than that for the total length of the same twisted plate. Therefore, an enhancement in the heat transfer coefficient for the twisted plate was clarified.

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