Study of Meandering Closed-Loop Heat-Transport Device. Vapor-Plug Propagation Phenomena.

Heat transport rates of micro scale SEMOS (Self-Exciting Mode Oscillating) heat pipe with inner diameter of 1.5mm, 1.2mm and 0.9mm, were investigated by using R141b, ethanol and water as working fluids. The effects of inner diameter, liquid volume faction, and material properties of the working fluids are examined. It shows that the smaller the inner diameter, the higher the thermal transport density is. For removing high heat flux, the water is the most promising working fluid as it has the largest critical heat transfer rate and the widest operating range among the three kinds of working fluids. A one-dimensional numerical simulation is carried out to describe the heat transport characteristics and the two-phase flow behavior in the closed loop SEMOS heat pipe. The numerical prediction agrees with the experimental results fairly well, when the input heat through was not very high and the flow pattern was slug flow. This paper was also originally published as part of the Proceedings of the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems.

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An Experimental Study of a Bubble-Driven Heat-Transport Device

ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference, Volume 1 ◽

10.1115/ht2007-32758 ◽

2007 ◽

Author(s):

Osamu Suzuki

Keyword(s):

Thermal Conductivity ◽

Effective Thermal Conductivity ◽

Heat Transport ◽

Tube Bundle ◽

Temperature Fluctuations ◽

Temperature Gradients ◽

Heating And Cooling ◽

Tube Bundles ◽

Steady State Time ◽

Transport Device

We experimentally measured the heat-transport characteristics of a bubble-driven heat-transport device. The device consisted of a non-looped copper tube containing water. The tube was either meandered or spiraled to form tube bundles. The inner surface of the tube was smooth and its diameter small enough to enable the formation of vapor and liquid plugs in it. Two copper blocks were attached to the tube bundles, one as a heating block and the other as a cooling block. In the experiment, most of the wall temperatures measured on the tube fluctuated periodically at a quasi-steady state. Time-averaged temperature gradients between the heating and cooling sections of the device were constant. By increasing heater input from 300W to 350W, the amplitude of the temperature fluctuations decreased and the temperature gradients increased significantly. This behavior was regarded as a transition to critical heat transport condition. The effective thermal conductivity of the device was proportional to the heat-transport rate but did not depend on the formation of the tube bundle and the gravity effect. The temperature fluctuations had specific peak frequencies and a positive correlation was found between the frequency and effective thermal conductivity. These experimental results strongly suggest that the main heat-transport mechanism of the investigated device is based on the oscillation-induced transport of sensible heat.

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Micro-Scale Two-Phase Flow Heat Transport Device Driven by Electrohydrodynamic Conduction Pumping

Volume 2: Heat Transfer Enhancement for Practical Applications; Heat and Mass Transfer in Fire and Combustion; Heat Transfer in Multiphase Systems; Heat and Mass Transfer in Biotechnology ◽

10.1115/ht2013-17196 ◽

2013 ◽

Author(s):

Viral K. Patel ◽

Jamal Seyed-Yagoobi

Keyword(s):

Heat Transport ◽

Two Phase Flow ◽

Operating Conditions ◽

Electrode Spacing ◽

Working Fluid ◽

Phase Flow ◽

Two Phase ◽

Micro Scale ◽

Flow Heat ◽

Transport Device

Micro-scale two-phase flow heat transport involves specialized devices that are used to remove large amounts of heat from small surface areas. They operate by circulating a working fluid through a heated space which causes phase change from liquid to vapor. During this process, a significant amount of heat is transported away from the heat source. Micro-scale heat transport devices are compact in size and the heat transfer coefficient can be orders of magnitude higher than in macro-scale for similar operating conditions. Thus, it is of interest to develop such devices for cooling of next-generation electronics and other applications with extremely large heat fluxes. The heat transport device presented in this paper is driven by electrohydrodynamic (EHD) conduction pumping. In EHD conduction pumping, when an electric field is applied to a dielectric liquid, flow is induced. The pump is installed in a two-phase flow loop and has a circular 1 mm diameter cross section with electrode spacing on the order of 120 μm. It acts to circulate the fluid in the loop and has a simple yet robust, non-mechanical design. Results from two-phase flow experiments show that it is easily controlled and such electrically driven pumps can effectively be used in heat transport systems.

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