Ice formation modes during flow freezing in a small cylindrical channel

Abstract

Freezing of water flowing through a small channel can be used as a nonintrusive flow control mechanism for microfluidic devices. However, such ice valves have longer response times compared to conventional microvalves. To control and reduce the response time, it is crucial to understand the factors that affect the flow freezing process inside the channel. This study investigates freezing in pressure-driven water flow through a glass channel of 500 m inner diameter using measurements of external channel wall temperature and flow rate synchronized with high-speed visualization. The effect of flow rate on the freezing process is investigated in terms of the external wall temperature, the growth duration of different ice modes, and the channel closing time. Freezing initiates as a thin layer of ice dendrites that grows along the inner wall and partially blocks the channel, followed by the formation and inward growth of a solid annular ice layer that leads to complete flow blockage and ultimate channel closure. A simplified analytical model is developed to determine the factors that govern the annular ice growth, and hence the channel closing time. For a given channel, the model predicts that the annular ice growth is driven purely by conduction due to the temperature difference between the outer channel wall and the equilibrium ice-water interface. The flow rate affects the initial temperature difference, and thereby has an indirect effect on the annular ice growth. Higher flow rates require a lower wall

Ultrafast Axial Freezing in a Liquid-Filled Capillary Tube

“…In the case of a liquid column with larger thicknesses, the effect of disjoining pressure is not considered. For normal pure water in the millimeter of quartz tubes at standard atmospheric pressure, the supercooling is approximately 6 °C . When the temperature reaches the supercooling degree, it does not require external energy and can proceed spontaneously; therefore, the thermal parameters of the tube do not influence v LF .…”

“…For normal pure water in the millimeter of quartz tubes at standard atmospheric pressure, the supercooling is approximately 6 °C. 8 When the temperature reaches the supercooling degree, it does not require external energy and can proceed spontaneously; therefore, the thermal parameters of the tube do not influence v LF . Based on the thermophysical properties of water listed in Table 1, the velocity of axial freezing in a water-filled capillary tube was calculated from eq 8 to be v LF ∼ 250 mm/s, independent of the tube diameter.…”

“…Freezing remains a perennial topic of great relevance to a wide variety of fields like climate, medicine, and energy. − In recent years, there is gowing interest in exploring how freezing occurs in liquid-filled capillary tubes, for they are not only a kind of standard component in life science (e.g., capillary blood vessels, interstitial pores, and plant vessels , ) but also commonly exploited in engineering (e.g., MEMS microchannel resonators, capillary electrophoresis, and heat pipe wicks , ). Therefore, under freezing temperatures, in order to better understand how life evolves (e.g., cryogenic freezing and frost damage) and how engineering components perform (e.g., permafrost and ice valve , ), it is of importance to explore the nucleation of ice and the movement of ice–water interface in such capillary tubes.…”

Study on ice nucleation temperature and water freezing in saline soils

“…If Equation is used to calculate the unfrozen water content with the form of contact between the ice nucleus and substrate taken as a plane, the initial contact angle calculated from test data listed in Table 2 is 22° 28 . The results are shown in Figure 10.…”

“…Classical nucleation theory has been used for particles immersed in cloud droplets to establish a relationship between nucleation rate and temperature 20–24 . Ice crystal dynamic equilibrium was achieved during this process based on thermodynamic equilibrium; thus, the mechanism of ice formation has been explained by the contact angle in heterogeneous nucleation theory 25–28 . A previous experiment was used to verify the applicability of classical nucleation theory in water freezing, and the critical nucleation radius was found to decrease as the particle size decreased 29 .…”