Extending the applicability of the flow boiling correlation to low Reynolds number flows in microchannels

As microchannels are applied in flow boiling applications, it is becoming apparent that the Reynolds number based on all liquid flow could approach values below 100. The earlier work by Kandlikar and Steinke (2002, 2003) provided modifications to the Kandlikar correlation (1990, 1991) by extending the range of the correlation to all-liquid Reynolds numbers in the range 1000 - 3000. The present work utilizes the newly available data on flow boiling in microchannels that cover the all-liquid flow Reynolds number between 50 - 500. A new correlation is developed in this range that is able to predict the flow boiling heat transfer coefficient and its trends with quality, heat flux and mass flux accurately within less than 15 percent mean deviation. It is noted that the correlation simply accounts for the change of the flow boiling mechanism without incorporating any additional empirical constants. The heat transfer mechanism during flow boiling at such low Reynolds numbers is altered considerably indicating strong presence of nucleate boiling mode of heat transfer.