Heat Transfer Characterizations of Heat Pipe in Comparison With Copper Pipe

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Chen-Ching Ting ◽  
Jing-Nang Lee ◽  
Chien-Chih Chen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Source ◽  
Heat Pipe ◽  
Heat Conductivity ◽  
Cooling Efficiency ◽  
Copper Pipe ◽  
Heat Transfer Behavior ◽  
Transfer Behavior ◽  
Large Heat

The article presents some significant experimental data for studying the heat transfer behavior of heat pipe, which will further help the cooling efficiency improvement of the heat pipe cooler. It is well known that the heat pipe owns the extreme large heat conductivity and is often integrated with cooling plates for CPU cooling. The heat pipe uses special heat transfer techniques to obtain extremely large heat conductivity, which are the inside liquid evaporation for heat absorption and the inside microstructural capillarity for condensation. These special techniques yield the instant heat transfer from the heat source to the remote side directly, but the special heat transfer behavior is changed due to the integration with cooling plates. The destroyed heat transfer behavior of the heat pipe causes the cooling efficiency of the heat pipe cooler to be not able to reach a predicted good value. To improve the cooling efficiency of the heat pipe cooler we recover the original heat transfer behavior of the heat pipe integrated with cooling plates. This work first built a CPU simulator in accordance with the ASTM standard for heating the heat pipe, then uses the color schlieren technique to visualize the sequent heat flux nearby the heat pipe and the infrared thermal camera for quantitative temperature measurements synchronously. The result shows that the heat flux first appears at the opposite side from the heat source and there exhibits also the highest temperature. This is different from the heat transfer behavior of the copper pipe. Another very interesting result is that the heat flux of the cooling plate nearest to the heat source is first viewed than the others, which is similar to the integration with the copper pipe.

Large Heat Transport Due to Spontaneous Gas Oscillation Induced in a Tube With Steep Temperature Gradients

1983 ◽  
Vol 105 (4) ◽  
pp. 889-894 ◽  
Author(s):  
T. Yazaki ◽  
A. Tominaga ◽  
Y. Narahara
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Helium ◽  
Heat Conductivity ◽  
Room Temperature ◽  
Evaporation Rate ◽  
Experimental Studies ◽  
Temperature Gradients ◽  
Pressure Amplitude ◽  
Large Heat

This paper describes experimental studies of heat transfer due to the oscillations of gas columns that are spontaneously induced in a tube with steep temperature gradients. The tube (∼3 m in length) is closed at both ends and bent into U-shaped form at the midpoint. The temperature distribution along the tube is step-functional and symmetrical with respect to the midpoint. The warm part (closed-end sides) is maintained at room temperature and the cold one is immersed in liquid helium (4.2 K). The heat transported from the warm part to the cold is estimated from the evaporation rate of liquid helium. The heat flux by the oscillations is proportional to the square of the pressure amplitude, and the effective heat conductivity can be several orders of magnitude larger than the molecular heat conductivity of gas. The experimental results are compared with the theory of the second-order heat flux proposed by Rott and are found to be in satisfactory agreement with this.

Effect of Heat Source Geometry on the Transient Heat Transfer During Melting Process of a PCM

2016 ◽  
Author(s):  
Mohammad Bashar ◽  
Kamran Siddiqui
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Convective Heat Transfer Coefficient ◽  
Outer Region ◽  
Melting Process ◽  
Melting Rate ◽  
Transfer Coefficients ◽  
Heat Transfer Behavior ◽  
Transfer Behavior ◽  
Inner Region

Thermal energy storage (TES) systems using phase change materials (PCMs) are used in various engineering applications. TES is a means by which heat is ‘hold’ for a certain period of time for use at a later time. We report an experimental study which was conducted to investigate the melting process and associated heat transfer in a rectangular chamber with a cylindrical u-shaped heat source imbedded inside the PCM. The results showed that geometry and orientation of the heat source immensely influenced the heat transfer behavior during solid-liquid phase transition. The heat transfer behavior, interface movement and the heat transfer coefficients differed both axially and vertically inside the chamber as well as with the melting rate. The local convective heat transfer coefficient, hlocal in the inner region, enclosed by the U-tube, was observed to increase at a higher rate than the outer region. Stronger convective flow and a lower viscosity owing to higher temperature in the inner region is believed to have caused faster melting in this region. The melting rate was also found comparatively higher until approximately two-third of the PCM volume was melted before the rate declined.

Heat Transfer Behavior of the Boundary Layer Near Surfaces in Annular Flow of High Capacity Canned Motor Pump

2016 ◽  
Author(s):  
Shengde Wang ◽  
Guohu Luo ◽  
Hong Shen ◽  
Zhenqiang Yao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Annular Flow ◽  
High Capacity ◽  
Heat Transfer Behavior ◽  
Transfer Behavior ◽  
Canned Motor ◽  
The Heat Transfer Coefficient

As significant fluid machinery, canned motor pumps are widely applied in industrial field. The typical characteristic of canned motor pump is that the fluid comes into the narrow gap and affects the performance of canned motor. The coolant flow in the narrow annular gap between rotor and stator cans belongs to Taylor-Couette-Poiseuille flow which has been investigated for a long time while the thermal design is a key function of internal narrow gap annular flow of canned motor. However, the temperature distribution prediction of canned motor deviates from the experiments, especially in the high-capacity canned motor due to the large shear rate of fluid and eddy-current loss of motor’s can. According to the researcher’s work, the significant work lies in the heat transfer coefficient that different researchers give various numerical prediction and experimental measurement. It brings big challenge in thermal design of high-capacity canned motor pump. In this paper, the author focuses on the reason why the heat transfer coefficient is remarkably lower than that other’s forecast. In this paper, the heat transfer behavior of the boundary layer near surfaces in the annular flow is investigated by using the commercial fluid dynamic (CFD) method. Firstly, the Naiver-Stocks (N-S) equations and energy conservation equation are employed for modeling the flow and heat transfer behavior, and the k-ω turbulent model is used for solving the flow control equations. Secondly, the fluid domain is described by a simplified geometrical model: two concentric cylinders with finite gap length. Thirdly, numerical approach is used to analyze the subject with tools of Solidworks, ICEM CFD and Ansys Fluent. Two parameters are analyzed in the research, namely the rotating speed and the wall heat flux, without considering the fluid viscous dissipation and thermal contact resistance. Numerical simulation results indicate that Taylor vortex exists in the flow regime, and the temperature distribution is affected by both the rotating speed and the wall heat flux, named thermal barrier effect under large heat flux condition. The thermal barrier effect lies in that the temperature gradient of interface decreases compared to the peak value of temperature gradient near the surface, so that the heat transfer coefficient is reduced remarkably. This effect leads to the temperature prediction deviates from the experiment measurement.

scholarly journals Heat transfer behavior of flat plate having 45° ellipsoidal dimpled surfaces

2014 ◽  
Vol 2 ◽  
pp. 67-74 ◽  
Author(s):  
Nopparat Katkhaw ◽  
Nat Vorayos ◽  
Tanongkiat Kiatsiriroat ◽  
Yottana Khunatorn ◽  
Damorn Bunturat ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Heat Transfer Behavior ◽  
Transfer Behavior
Sign in / Sign up

Export Citation Format

Share Document