Freezing Points, Densities, and Refractive Indexes of System Glycerol-Ethylene Glycol-Water

Promising Nanoparticle-Based Heat Transfer Fluids-Environmental and Techno-Economic Analysis Compared to Conventional Fluids

Providing optimal operating conditions is one of the major challenges for effective heating or cooling systems. Moreover, proper adjustment of the heat transfer fluid is also important from the viewpoint of the correct operation, maintenance, and cost efficiency of these systems. Therefore, in this paper, a detailed review of recent work on the subject of conventional and novel heat transfer fluid applications is presented. Particular attention is paid to the novel nanoparticle-based materials used as heat transfer fluids. In-depth comparison of environmental, technical, and economic characteristics is discussed. Thermophysical properties including thermal conductivity, specific heat, density, viscosity, and Prandtl number are compared. Furthermore, the possible benefits and limitations of various transfer fluids in the fields of application are taken into account.

Cryogenic viscoelastic surfactant fluids: Fabrication and application in a subzero environment

HYPOTHESIS

Current viscoelastic surfactant (VES) aqueous solutions quickly freeze and thus, lose their viscoelasticity and flowability at subzero temperatures, limiting their practical use in cold environments. Therefore, it is highly desirable to develop cryo-VES fluids with freezing point far below 0 °C. Since addition of alcohol antifreeze greatly reduces the freezing point of water, cryo-VES fluids might be generated in the presence of alcohols.

EXPERIMENTS

The self-assembly behavior of a C₂₂-tailed surfactant, erucyl dimethyl amidopropyl betaine (EDAB), in eight alcohol/water cosolvents from 20 to -20 °C was studied by pyrene fluorescent probe, cryo-TEM imaging and cryo-SNAS characterization, and the solution properties of the mixtures were investigated by rheological test.

FINDINGS

It is found that the alcohol molecular structure, content and temperature play crucial roles dominating EDAB self-assembly behavior. Monohydric alcohols are unfavorable for micelles formation and growth, thus VES fluids cannot be obtained in the presence of 50 vol% monohydric alcohols even at subfreezing temperatures. On the contrary, dihydric and trihydric alcohols with short alkyl chain show less negative effect on EDAB micellization. Thus, cryo-VES fluids can be formed in the presence of 50 vol% ethylene glycol, 1,3-propanediol or glycerol due to the formation of wormlike micelles. These cryo-VES fluids with different alcohols exhibit different temperature-sensitivity and rheological properties, furnishing them with potential applications in anti-freeze hydraulic fracking fluids and aircraft deicing/anti-icing fluids.

Alteration of fluorescent protein spectroscopic properties upon cryoprotection

Cryoprotection of a protein crystal by addition of small-molecule compounds may sometimes affect the structure of its active site. The spectroscopic and structural effects of the two cryoprotectants glycerol and ethylene glycol on the cyan fluorescent protein Cerulean were investigated. While glycerol had almost no noticeable effect, ethylene glycol was shown to induce a systematic red shift of the UV–vis absorption and fluorescence emission spectra. Additionally, ethylene glycol molecules were shown to enter the core of the protein, with one of them binding in close vicinity to the chromophore, which provides a sound explanation for the observed spectroscopic changes. These results highlight the need to systematically record spectroscopic data on crystals of light-absorbing proteins and reinforce the notion that fluorescent proteins must not been seen as rigid structures.

ROLE OF GLYCEROL IN THE COLD-HARDENING OF BRACON CEPHI (GAHAN)

Concentrations of glycerol as great as 5 molal are built up in larvae of Bracon cephi (Gahan) after hibernation begins in the fall, and are lost again in the spring. The source of the glycerol was not determined, but is not glycogen. Large solute concentrations, composed mostly of glycerol, depress the melting points of the haemolymph to as low as −17.5 °C. Supercooling points of the intact larvae are lowered even more than their melting points, and this excess is proportional to the melting point depression.Glycerol is directly responsible for the cold-hardening of the larvae in two separate ways: by increasing supercooling, it increases the ability of the larvae to avoid freezing, and by its protective action it allows the larvae to survive even if they do freeze.