Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Flow boiling of R1336mzz(Z) in open microchannels with diverging manifold
Submission Author:
Debora Carneiro Moreira , SP , Brazil
Co-Authors:
Debora Carneiro Moreira, Valter Salles do Nascimento Junior, Gherhardt Ribatski, Satish Kandlikar
Presenter: Debora Carneiro Moreira
doi://10.26678/ABCM.COBEM2021.COB2021-1556
Abstract
The advances in electronics and miniaturization of components is directly related to an increasing demand for high heat flux dissipation technologies. Among many existing techniques used to dissipate high heat fluxes, heat sinks based on flow boiling in microchannels is one of the most promising ones, given the possibility of reaching extremely high values of critical heat flux (CHF) that have already surpassed 1 kW/cm2, with huge values of heat transfer coefficient (HTC) and minimum temperature variation along the devices. In this context, over the last decades many efforts have been made to develop these heat sinks, revealing mechanisms that can be altered to enhance flow boiling heat transfer. The use of open and diverging manifold over microchannels as a vapor venting technique resulted in simultaneous augmentation of HTC and CHF with reduction in pressure drop, and can be applied over any array of channels or pillars, but there is limited data on experiments with refrigerant fluids in such configuration. In this work the flow boiling behavior of the refrigerant R1336mzz(Z) in a microchannels-based heat sink with an open and divergent manifold was investigated. The test section comprises a copper chip with milled microchannels and a polysulfone cover with a diverging open section above the channels. Flow boiling experiments were conducted for degrees of subcooling of 10 and 20 °C and mass fluxes equal to 400, 600, and 1000 kg/m2s. Values of CHF and HTC during the experiments reached up to 72.8 W/cm2 and 16.8 kW/m2K, with total pressure drop lower than 10 kPa. The obtained results show that increase in mass flux caused increase in CHF, but at the cost of higher wall superheats and consequently lower HTC at low heat fluxes. However, as the higher mass flux enables the dissipation of higher heat fluxes and HTC increases with heat flux, the maximum HTC was achieved at the highest mass flux. Inlet subcooling had similar effects as mass flux, which was attributed to the portion of the heat sink in which phase-change effectively occurred.
Keywords
Thermal management, cooling, Low GWP Refrigerants, Two-phase Flow, HFO, Microfluidics, heat sink
