Experimental measurement of thermal characteristics of two-phase segmented flow in minichannel heat sinks

Janes, Nicholas Gill (2013) Experimental measurement of thermal characteristics of two-phase segmented flow in minichannel heat sinks. Masters thesis, Memorial University of Newfoundland.

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Abstract

Experiments were conducted to measure the heat transfer characteristics of non-boiling two-phase segmented flow in two different miniature heat sinks. The heat sinks were manufactured to have a square wave flow path (termed Square Sink) and a spiral flow path (termed Spiral Sink). -- The working fluids used in the experiments were water, canola oil and air. Single phase water and oil were examined first, and the results were used as a basis for comparison of the two-phase flow results. Two-phase flow experiments using water-air and oil-air were then conducted. The flow rates of the water-air and oil-air phases were varied between a range of values during each experiment and the system pressure and temperatures were recorded at each combination of flow rates. -- The experimental data was used to calculate the value of dimensionless heat transfer q* and dimensionless length L*, which were used to compare the thermal performance from each experiment. The two-phase flow experiments for the square heat sink resulted in a dimensionless heat transfer enhancement of 24% for water-air containing long liquid slugs, 39.5% for water-air containing short liquid slugs and 1% for oil-air. The two-phase flow experiments for the spiral heat sink resulted in a dimensionless heat transfer enhancement of 14% for water-air containing short slugs. -- The effects of liquid slug length and void fraction were examined. The effect of liquid slug length was shown to increase the dimensionless heat transfer as the slug length decreased. The effect of void fraction was found to be a controlling factor due to its impact on liquid slug length, which in turn affects dimensionless heat transfer. Finally the efficiencies of the square sink and spiral sinks were compared and it was shown that the spiral sink was most efficient when power requirements are considered.

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