Thermophysical Properties Of Liquid Research Articles

Laser-based thermal pulse measurement of liquid thermophysical properties

In this work, a laser-based thermal pulse technique is presented that simultaneously measures thermal conductivity and thermal diffusivity for liquids, from which the volumetric specific heat can be determined as well. The measurement is based on photothermal deflection of a HeNe laser beam that passes through the test liquid next to a thin heating wire. Liquid thermophysical properties are determined by fitting a numerical simulation of the heat conduction and probe beam deflection to the measured time-dependent probe beam deflection. Results are presented for five liquids: glycerol, 1-propanol, 2-propanol, methanol, and ethanol, and are found to be in very good agreement with values reported in the literature. The experimental setup is small, inexpensive and reliable. The temperature dependence of the liquid refractive index is also determined during the measurement process, and the same experimental technique is capable of measuring the thermal conductivity and thermal diffusivity of thin conducting wires.

Boiling nucleation during liquid flow in microchannels

The boiling of liquids in microchannels/microstructures is currently of great interest due to its very unusual phenomena and its many potential applications in a wide variety of advanced technologies. The thermodynamic aspects of phase transformations of liquids in microchannels was analyzed to further understand the boiling characteristics and to determine the conditions under which a portion of such liquids is likely to undergo phase change. A nondimensional parameter and related criteria, that determine the phase transition in microchannels, were derived theoretically. The size of the microchannels results in dramatically high heat fluxes and superheats for liquid nucleation when the microchannel is sufficiently small. The effect that the liquid thermophysical properties have on the nucleation is also described by the analysis.

Cooling augmentation with microchanneled structures

Experiments were conducted to investigate the heat transfer characteristics and cooling performance of snbcooled liquid, water, flowing through rectangular cross-section microchanneled structures machined on a stainless steel plate. Heat transfer or flow mode transition was observed when the heating rate or wall temperature was increased. This transition was found to be suggestively induced by the variation in liquid thermophysical properties due to the significant rise of liquid temperature in the microstructures. The influence of such parameters as liquid velocity, subcooling, property variation, and microchannel geometric configuration on the heat transfer behavior, cooling performance and the heat transfer and liquid flow mode transition were also investigated. The experiments indicated that both single-phase forced convection and flow boiling characteristics were quite different from those in normal-sized tubes and the heat transfer was obviously intensified.

Experimental Investigation of Capillary-Induced Rewetting in a Flat Porous Wicking Structure

An experimental program was conducted to investigate the rewetting characteristics of liquid flowing through multiple layers of screen mesh covering a heated vertical plate. Data obtained for acetone and R-11 were analyzed and compared with previously developed theoretical expressions for the rewetting velocity, the maximum liquid rise height, and the maximum heat flux for which rewetting could occur. The experimental results indicate that the thickness of the screen mesh layer and the liquid thermophysical properties are the most important factors affecting the rewetting behavior. As predicted by the theoretical model, small increases in the thickness of the screen layer initially caused the maximum permissible rewetting heat flux to increase. Once the layer thickness had reached a critical value, continued increases resulted in a decrease in the maximum permissible rewetting heat flux.

Measurement of thermophysical properties of mixtures by periodic heating of probes

We analyze the theory of the method of periodic heating of probes as applied to the study of thermophysical properties of liquid and gaseous mixtures.