The thermal irreversibility in microfluidic annular channel and a microfluidic chip

Abstract

The shape, size, and performance of microfluidic chip heaters are designed to fit the housing of microfluidic chips and channels. During the heating process, some of the heat is transferred to the surrounding environment where the microfluidic chip is located, which is typically undesirable. In order to better control the heating of the fluid within the microfluidic channel, this study examines a heating wire placed coaxially inside the channel. The fluid flows through the annular space between the channel and the heating wire, which maintaining a constant heat flux and minimizing heat transfer to the environment. To provide a basis for comparison, an analysis of fluid flow within a straight channel chip with a heat source of constant temperature is also conducted. The methodology used combines analytical modeling with experimental testing. Thermal entropy and entransy flow rate during fluid flow within the microfluidic channel are studied in relation to changes in volumetric flow rate, the temperature of the microfluidic chip housing, and the heat transfer from the heating wire. Additionally, a modified irreversibility ratio is used to further describe the relationship between thermal entropy and entransy flow rate. The results show that the fluid heated in the annular microfluidic channel exhibits lower thermal entropy and higher entransy flow rate compared to the straight channel chip.