Subcooled and saturated water flow boiling pressure drop in small diameter helical coils at low pressure

Heat dissipation beyond 1 kW/cm2 accompanied with high heat transfer coefficient and low pressure drop using water has been a long-standing goal in the flow boiling research directed toward electronic cooling application. In the present work, three approaches are combined to reach this goal: (a) a microchannel with a manifold to increase critical heat flux (CHF) and heat transfer coefficient (HTC), (b) a tapered manifold to reduce the pressure drop, and (c) high flow rates for further enhancing CHF from liquid inertia forces. A CHF of 1.07 kW/cm2 was achieved with a heat transfer coefficient of 295 kW/m2°C with a pressure drop of 30 kPa. Effect of flow rate on CHF and HTC is investigated. High speed visualization to understand the underlying bubble dynamics responsible for low pressure drop and high CHF is also presented.

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Experimental Study of Heat Transfer, Pressure Drop, and Dryout for Flow Boiling of Water in an Oil Heated Minichannel

ASME 2nd International Conference on Microchannels and Minichannels ◽

10.1115/icmm2004-2387 ◽

2004 ◽

Cited By ~ 3

Author(s):

Levi A. Campbell ◽

Satish Kandlikar

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Test Section ◽

Two Phase Flow ◽

Flow Boiling ◽

Small Diameter ◽

Constant Heat Flux ◽

Phase Flow ◽

Two Phase ◽

Mass Fluxes

Heat transfer and pressure drop, are experimentally recorded for flow boiling water in a single 706 μm circular copper channel 158.75 mm long. Heat is supplied by heat transfer oil at specified temperatures to a helical channel in the test section. In contrast to other current experimental techniques for flow boiling in small diameter tubes, a uniform temperature boundary condition is employed rather than a constant heat flux condition. The principal results of these experiments are two-phase flow boiling heat transfer rates and an analysis of the time-dependent pressure drop signature during two-phase flow in a minichannel. The range of experiments includes mass fluxes of 43.8–3070 kg/m2s and wall temperatures of 100°C–171.2°C. In all cases the test section water inlet is subcooled to between 72.9°C and 99.6°C. The inlet pressures used are 1.1–230.5 kPa (gage).

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Flow boiling of ammonia in vertical small diameter tubes: Two phase frictional pressure drop results and assessment of prediction methods

International Journal of Thermal Sciences ◽

10.1016/j.ijthermalsci.2011.11.018 ◽

2012 ◽

Vol 54 ◽

pp. 1-12 ◽

Cited By ~ 24

Author(s):

M.H. Maqbool ◽

B. Palm ◽

R. Khodabandeh

Keyword(s):

Pressure Drop ◽

Flow Boiling ◽

Small Diameter ◽

Prediction Methods ◽

Two Phase ◽

Frictional Pressure Drop

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The Characteristics of Flow Boiling Heat Transfer and Pressure Drop in Small Tube with the Pipe Sections Having Increased Diameters

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.651.525 ◽

2013 ◽

Vol 651 ◽

pp. 525-529

Author(s):

Mao Yu Wen ◽

Kang Jang Jang

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Boiling Heat Transfer ◽

Flow Boiling ◽

Small Diameter ◽

Saturation Temperature ◽

Smooth Tube ◽

Flow Boiling Heat Transfer ◽

Small Tube

This study presents an experimental investigation of the characteristics of the flow boiling heat transfer and pressure drop for refrigerant of R134a flowing in a small - diameter evaporative tube with the pipe sections having increased diameters. The experiments were performed at the saturation temperature of 5°C , heat flux of 5.12 ~ 10.96 ( KW/m2), mass flux of 200~600 ( kg/m2s), different length-to-diameter ratios of the test tubes and refrigerant quality of 0.07~0.78, and based on the same surface area of heat transfer. The enhancement performance ratios, θa/s for the tubes with the pipe sections having increased diameters relative to the smooth tube are higher than 1 (about 1.01~1.10). It means that the augmented tubes show the better overall performance than the smooth tube under study.

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