Isobaric Specific Heat Capacity for Al2O3/ Water Ethylene Glycol Mixture Nanofluid

Specific heat is a vital characteristic of nanofluids. The present work is an experimental assessment for the isobaric specific heat measurements for the Al2O3 nanoparticle dispersed in a base fluid of different mixture ratio of ethylene glycol and water at 30, 40, 50, and 60 vol%. The experiments were conducted over temperature range from 35 to 105 °C with nanoparticle concentrations of 0.5 to 2.5 vol%. The results indicated that the specific heat of nanofluid decreases as the nanoparticle volume increases and EG ratio increases but increases as the temperature increases. This characteristic demonstrates that the use of nanofluids should be at as high temperature as possible to fulfill a good beneficial effect. A new correlation from the measurements with maximum deviation of 2.2% was found to estimate the specific heat for these nanofluids.

Enhancement and maximum in the isobaric specific-heat capacity measurements of deeply supercooled water using ultrafast calorimetry

Knowledge of the temperature dependence of the isobaric specific heat (Cp) upon deep supercooling can give insights regarding the anomalous properties of water. If a maximum in Cp exists at a specific temperature, as in the isothermal compressibility, it would further validate the liquid–liquid critical point model that can explain the anomalous increase in thermodynamic response functions. The challenge is that the relevant temperature range falls in the region where ice crystallization becomes rapid, which has previously excluded experiments. Here, we have utilized a methodology of ultrafast calorimetry by determining the temperature jump from femtosecond X-ray pulses after heating with an infrared laser pulse and with a sufficiently long time delay between the pulses to allow measurements at constant pressure. Evaporative cooling of ∼15-µm diameter droplets in vacuum enabled us to reach a temperature down to ∼228 K with a small fraction of the droplets remaining unfrozen. We observed a sharp increase in Cp, from 88 J/mol/K at 244 K to about 218 J/mol/K at 229 K where a maximum is seen. The Cp maximum is at a similar temperature as the maxima of the isothermal compressibility and correlation length. From the Cp measurement, we estimated the excess entropy and self-diffusion coefficient of water and these properties decrease rapidly below 235 K.

PHASE TRANSITION OF THE REISSNER-NORDSTROM BLACK HOLE

The phase transition of matter outside the four-dimensional Reissner-Nordstr¨om charged black hole have been investigated. Based on the metric we have found analytic expressions for thermodynamic quantities as temperature, pressure and isobaric specific heat. The numerical results have shown that for temperatures T less than the critical value Tc there exits a ”liquid-gas” phase transition similar to the Van der Waals fluid. In addition, also pointed out that both temperature and spatial curvature affect phase transitions, but phase transitions are always the first oder.

Specific Heat and Transport Functions of Water

Numerous water characteristics are essentially ascribed to its peculiarity to form strong hydrogen bonds that become progressively more stable on decreasing the temperature. However, the structural and dynamical implications of the molecular rearrangement are still subject of debate and intense studies. In this work, we observe that the thermodynamic characteristics of liquid water are strictly connected to its dynamic characteristics. In particular, we compare the thermal behaviour of the isobaric specific heat of water, measured in different confinement conditions at atmospheric pressure (and evaluated by means of theoretical studies) with its configurational contribution obtained from the values of the measured self-diffusion coefficient through the use of the Adam–Gibbs approach. Our results confirm the existence of a maximum in the specific heat of water at about 225 K and indicate that especially at low temperature the configurational contributions to the entropy are dominant.

Experimental studies of optoacoustic effect on the model of erythrocytes in the presence of carbon nanoparticles

Experimental model has been developed to study optoacoustic signal from model blood cells presented by polystyrene microspheres with nanoparticles. It was found out that nanoparticles due to their strong absorption of light significantly affect the coefficient of cellular optical absorption, while the thermophysical parameters, namely the coefficient of thermal expansion, compressibility and isobaric specific heat of cells remain unchanged, since nanoparticles occupy a small intracellular volume compared to the cell volume. Optoacoustic signals were obtained using model solutions at various concentrations of cells and nanoparticles using 1064 nm laser. The results of experimental measurements using LIMO 100–532/1064-U system based on Nd:YAG showed that the amplitude of the optoacoustic signal increased without increasing the temperature in the laser area.