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Heating and Cooling of Agro Products
Published in B. K. Bala, Agro-Product Processing Technology, 2020
A solution freezes at a lower temperature than does the pure solvent. This phenomenon is called freezing-point depression. The freezing-point depression of a solution is a colligative property of the solution that is dependent upon the number of dissolved particles in the solution. The higher the solute concentration, the greater the freezing-point depression of the solution. Freezing-point depression is the decrease of the freezing point of a solvent on the addition of a nonvolatile solute. Examples include salt in water, alcohol in water, or the mixing of two solids such as impurities into a finely powdered drug.
Freeze Desalination-Membrane Distillation Hybrid Systems
Published in Kang-Jia Lu, Tai-Shung Chung, Membrane Distillation, 2019
Jian Chang, Kang-Jia Lu, Peng Wang, Tai-Shung Chung
Freezing-point depression is a phenomenon where the freezing point of a solvent is decreased by the presence of solutes (Gooch, 2011; Halde, 1980). It is noted that the lowering of the freezing point does not depend on the nature of the solutes. Instead, it is only proportional to the number of dissolved molecules and ions. The expression of freezing-point depression is generally given as: ΔTf=−KFPmo where ∆Tf is the freezing point depression, KFP is the cryoscopic constant which is 1.86 K kg/mol for water, and mo is the molality (mol solute/1000 g solvent).
Moisture modeling and durability assessment of building envelopes
Published in Jan L.M. Hensen, Roberto Lamberts, Building Performance Simulation for Design and Operation, 2019
Aytaç Kubilay, Xiaohai Zhou, Dominique Derome, Jan Carmeliet
The derived moisture and heat transport equations are based on the following hypotheses (Zhou et al. 2017): (1) the porous media are undeformable and no volume change occurs during freezing and thawing; (2) there is no salt present in the porous medium; (3) there is an analogy between capillary pressure curve (the relationship between capillary pressure and moisture content) and freezing curve (the relationship between subzero temperature and unfrozen liquid water content). If a solute is considered to be present in the porous medium, the melting point of water in porous medium is further depressed. The freezing point depression depends also on the concentration of the solutes. In reality, porous media are deformable and thus volume changes occur during freezing and thawing, leading to damage. Within the scope of this chapter, the influence of volume change on the freezing process is not considered.
Microfluidic platform for coupled studies of freezing behavior and final effloresced particle morphology in Snomax® containing aqueous droplets
Published in Aerosol Science and Technology, 2023
Margaret L. House, Cari S. Dutcher
Frozen fraction versus temperature and cumulative INAS density, K(T), versus temperature are shown for the monovalent NaCl and Snomax mixture, the divalent CaCl2 and Snomax mixture, and the 5.25:1 NaCl:CaCl2 mix in Figure 4. These curves are corrected for freezing point depression. Heat treatments were applied because they had a predictable effect on the ice nucleating proteins in the Snomax bacteria, flattening the beta helix structures into beta sheets (Roy, House, and Dutcher 2021) and inactivating the bacteria’s ice nucleating capabilities. The effect of this flattening could then be compared across cation differences. In addition, we could observe the effect of gradual Snomax denaturation on final effloresced particle morphology. Even after freezing point depression correction, the mixture of 1 M divalent CaCl2 shows a significantly lower freezing activity than the monovalent mixture. The divalent curves are also more “spread” than the monovalent curves, with more warm and more cold freezers. To potentially distinguish slight differences in INAS density more clearly between the fully monovalent mixture and the monovalent–divalent mixture, the derivative form of INAS, K(T), was also calculated for these cases. The results of the derivative calculation are included in the online Supplemental Information. The role of cation enrichment on the IN activity will be discussed in more detail in Section 4.2.
Polyethylene glycol and membrane processes applied to suction control in geotechnical osmotic testing
Published in International Journal of Geotechnical Engineering, 2022
Rick Vandoorne, Petrus J. Gräbe, Gerhard Heymann
Osmotic pressure is a colligative property of a solution and is thus related to the other colligative properties: freezing-point depression, boiling-point elevation and vapour pressure depression (Rudin 1999). Boiling-point elevation and freezing-point depression techniques are not well suited for use with aqueous PEG solutions of high molecular weight as is commonly used in geotechnical osmotic testing. This is because the osmotic pressure of an aqueous PEG solution is temperature dependent (Sweeney and Beuchat 1993; Winzor 2004), which is not the case for many common salt solutions such as NaCl, KCl and CaCl2 (Kiyosawa 2003). Due to their very nature, the freezing-point and boiling-point techniques can only determine the osmotic pressure at the freezing-point and boiling-point temperature respectively. This is likely not within the temperature range of interest for geotechnical osmotic testing. Vapour pressure depression techniques allow the determination of the osmotic pressure at the specific temperature of interest.
Integrated and intelligently controlled unit for suspension freeze concentration: design and experimental verification
Published in Instrumentation Science & Technology, 2021
Kewen Peng, Hongkai Yang, Huibin Yin, Frank G. F. Qin
To estimate the refrigeration capacity and the time required for chilling the original solution, the freezing point, Tf, of the solution has to be determined. Due to the effect of freezing point depression (FPD), Tf is a function of the solution concentration Cs. To facilitate the estimation of Tf, the FPD data of 16 food liquids and 64 chemical solutions has been compiled from previous publications[21–23] and stored in the controlling system. The relations between Tf and Cs for several representative solutions are displayed in Figure 3 and the pertinent correlations from fitting are presented in Table 1. Based on the derived relations, Tf can be obtained immediately from the control panel by choosing the solution to be treated with the measured concentration.