Estimation of heat transfer coefficient of forced-air cooling and its experimental validation in controlled processing of forgings

2018 ◽  
Vol 73 (3) ◽  
pp. 163-176
Author(s):  
Piotr Skubisz ◽  
Henryk Adrian
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Experimental Validation ◽  
Air Cooling ◽  
Controlled Processing ◽  
Forced Air

scholarly journals Considerations on the importance of proper heat transfer coefficient modeling in air cooled electronic systems

2018 ◽  
Vol 31 (4) ◽  
pp. 519-528 ◽  
Author(s):  
Marcin Janicki ◽  
Agnieszka Samson ◽  
Tomasz Raszkowski ◽  
Tomasz Torzewicz ◽  
Andrzej Napieralski
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Source ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Electronic Systems ◽  
Air Cooling ◽  
Simulation Accuracy ◽  
Forced Air

This paper illustrates, based on a practical example of a hybrid circuit, the influence of proper heat transfer coefficient modelling in air cooled electronic systems on the accuracy of thermal simulations. This circuit contains a transistor heat source and a set of temperature sensors. The measurements of their temperature responses are taken in natural convection and forced air cooling conditions. The experimental data provide the information necessary to estimate the local heat transfer coefficient values in heat source and temperature sensor locations. Moreover, the experiments rendered possible the fitting of parameters of an empirical heat transfer coefficient model for different surface temperature rise values and cooling air velocities, and hence allowed significant improvement of thermal simulation accuracy.

Numerical Analysis on Heat Transfer Coefficient of Large Die Steel Quenching

2012 ◽  
Vol 487 ◽  
pp. 449-452
Author(s):  
Xin Xiao Bian ◽  
Chao Zhang ◽  
Lin Zhu Qian
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Process Simulation ◽  
Air Cooling ◽  
Empirical Equations ◽  
Surface Conditions ◽  
Die Steel ◽  
Quenching Process ◽  
The Heat Transfer Coefficient

Heat transfer coefficient is one of the most important boundary conditions for quenching process simulation. It depends on many factors, such as material, size, surface conditions of a part, and so on. It is, therefore, difficult to evaluate the heat transfer coefficient accurately. T In the environment for large modules P20 and the actual heat transfer conditions, the off-line air-cooling heat transfer coefficient of C are simulated by using empirical equations.

Heat transfer between Phaseolus vulgaris and the environment

1971 ◽  
Vol 49 (6) ◽  
pp. 833-838 ◽  
Author(s):  
T. F. Saldin ◽  
N. Barthakur
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Phaseolus Vulgaris ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Forced Air ◽  
Theoretical Results ◽  
Infrared Radiometer

Heat transfer was studied from intact leaves of greenhouse-grown Phaseolus vulgaris L. under still and forced air conditions. Microwaves were used to heat the leaves without disturbing the thermal equilibrium of the environment. Leaf temperatures were measured by thermocouples and an infrared radiometer. Convective heat transfer coefficient for a leaf was obtained by two experimental methods and compared with the theoretical results. The unsteady-state method proved to be quite satisfactory.Typical values of heat transfer coefficient for free convection varied from 1.86 × 10−4 to 3.64 × 10−4 cal cm−2 s−1 °C−1, as the temperature difference between the leaf surface and the surrounding air increased from 1.0 to 3.9 °C. Forced convective heat transfer coefficient, however, increased to about 10 × 10−4 cal cm−2 s−1 °C−1 at 610 cm s−1.

scholarly journals THE METHOD OF CALCULATION AND ANALYSIS OF HEAT TRANSFER COEFFICIENT OF BIMETALLIC FINNED TUBES OF AIR COOLING UNITS WITH IRREGULAR EXTERNAL CONTAMINATION

2017 ◽  
Vol 60 (3) ◽  
pp. 237-255
Author(s):  
V. V. Dudarev ◽  
S. O. Filatаu ◽  
T. B. Karlovich
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
New Method ◽  
Constant Thickness ◽  
Air Cooling ◽  
Term Operation ◽  
Finned Tubes ◽  
Annular Layer ◽  
The Heat Transfer Coefficient

The article focuses on a new method of calculating heat transfer coefficient of bimetallic finned tubes of air coolers taking into account external operational pollution. In contrast to wellknown methods that use the assumption of a uniform distribution of operational contamination layer with a constant thickness over the entire surface of the fins in the present method being introduced it is assumed that the thickness of the pollution layer during long-term operation is changed irregularly. Under such conditions the thickness of the pollution layer at the base of the fins becomes much greater than at the rest of the finned surface. The suggested method is based on a mathematical model developed with the use of the method of electrothermal analogy, whereby the heat flow through the wall of the finned tube is considered as divided into two components, viz. through the annular layer of outside contamination adjacent to the base of the ribs, and through the remaining part of the external ribbed surface covered with a thin layer of pollution. Within the framework of the developed methodology a new method for determining the thermal resistance of the pollution layer, which is based on analytical solution of two dimensional problem of heat conduction in the annular layer has been created. With the use of this technique the influence of the degree of contamination of the intercostal space of the industrially manufactured bimetallic finned tubes on the heat transfer coefficient has been studied taking into account the intensity of heat transfer of air and the properties and composition of the pollutant for industrial manufactured bimetallic finned tubes. It is established that a layer thickness of the pollutant at the base of the ribs has the greatest influence on the heat transfer coefficient. This is due primarily to the change of actual coefficient of the fins. It is demonstrated that the heat conductivity of the external pollutant has a significant impact on the heat transfer coefficient when the heat exchanger functions in the mode of forced convection of air.

Electrohydrodynamic Microfabricated Ionic Wind Pumps for Thermal Management Applications

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Andojo Ongkodjojo Ong ◽  
Alexis R. Abramson ◽  
Norman C. Tien
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Management ◽  
High Reliability ◽  
Semiconductor Industry ◽  
Heat Removal ◽  
Coefficient Of Performance ◽  
Air Cooling ◽  
Ionic Wind

This work demonstrates an innovative microfabricated air-cooling technology that employs an electrohydrodynamic (EHD) corona discharge (i.e., ionic wind pump) for electronics cooling applications. A single, microfabricated ionic wind pump element consists of two parallel collecting electrodes between which a single emitting tip is positioned. A grid structure on the collector electrodes can enhance the overall heat-transfer coefficient and facilitate an IC compatible batch process. The optimized devices studied exhibit an overall device area of 5.4 mm × 3.6 mm, an emitter-to-collector gap of ∼0.5 mm, and an emitter curvature radius of ∼12.5 μm. The manufacturing process developed for the device uses glass wafers, a single mask-based photolithography process, and a low-cost copper-based electroplating process. Various design configurations were explored and modeled computationally to investigate their influence on the cooling phenomenon. The single devices provide a high heat-transfer coefficient of up to ∼3200 W/m2 K and a coefficient of performance (COP) of up to ∼47. The COP was obtained by dividing the heat removal enhancement, ΔQ by the power consumed by the ionic wind pump device. A maximum applied voltage of 1.9 kV, which is equivalent to approximately 38 mW of power input, is required for operation, which is significantly lower than the power required for the previously reported devices. Furthermore, the microfabricated single device exhibits a flexible and small form factor, no noise generation, high efficiency, large heat removal over a small dimension and at low power, and high reliability (no moving parts); these are characteristics required by the semiconductor industry for next generation thermal management solutions.

Numerical Simulation of Ammonia Flow Boiling in a Horizontal Circular Tube

2013 ◽  
Vol 718-720 ◽  
pp. 162-165
Author(s):  
Sheng Long Wang ◽  
Yin Hai Ge ◽  
Wen Hao Li
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Volume Fraction ◽  
Cooling System ◽  
Flow Boiling ◽  
Convective Heat Transfer Coefficient ◽  
Air Cooling ◽  
Horizontal Pipe

In order to understand the variation of ammonia as a cooling refrigerant, the ammonia coolant is being used in power plant air cooling system. The subcooled boiling phase transformation of ammonia in a horizontal pipe tube was simulated through the application of the CFD fluid computational platform, the fluid state parameters in the tube were given at the same time. The speed variation along the axis of the tube was obtained, the speed is increasing, the Reynolds number corresponding substantial increase in the convective heat transfer coefficient corresponds to raise; The vapor volume fraction and boiling heat transfer coefficient along the tube were obtained. The boiling can strengthen the heat transfer significantly. The results showed that the ammonia as a cooling refrigerant by raising the Reynolds number and the use of the latent heat absorb these dual characteristics to improve the heat transfer coefficient is worth promoting.

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