Experimental investigation on the effects of the geometry of microchannels based heat sinks on the flow boiling of HFE-7100

•MCHs with different aspect ratios and wall thickness are tested.•New experimental procedures based on high-speed thermography are performed.•A MEMS device capable to meet the heat transfer optimization requirements is examined.•Narrower channels show thermal performance but high pressure losses.•Channels with wider walls exhibit higher overall heat transfer coefficients and lower pressure losses. In this paper, nine Microchannel Heat sinks (MCHs) all with channel lengths of 20 mm and heights of 1 mm but with different aspect ratios 1.33; 2 and 4, wall thicknesses 0.25–0.75 were tested in single and two-phase flows using the HFE-7100 as the working fluid. Three different scenarios were established, changing only the inlet temperature of the fluid: ambient (18–25 °C), intermediate (38–42 °C) and near saturation (55–58 °C). In all experiments the flow at the inlet was in the laminar region with Reynolds (Re) number values ranging from 50 to 130. A thermographic camera was placed below the microchannel heat sink, to observe the cooling process during the flows. Thus, the main objective of this study is to evaluate the effects of channel geometry on both the overall heat transfer coefficient and the pressure losses. The results demonstrate that, for both single and two-phase flow, narrower channels exhibit better thermal performance but higher-pressure losses than wider channels. When maintaining channel width constant and varying thicknesses, channels with wider walls presented higher overall heat transfer coefficients and lower pressure losses.