Repository logo
 

Research Publications (Engineering and Built Environment)

Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/215

Browse

Author: search.filters.author.Mohammadi, Amir H.Subject: search.filters.subject.Clathrate hydrate

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Thermodynamic stability conditions of clathrate hydrates for refrigerant (R134a or R410a or R507) with MgCl2 aqueous solution
    (Elsevier BV, 2016-04-15) Ngema, Peterson Thokozani; Naidoo, Paramespri; Mohammadi, Amir H.; Richon, Dominique; Ramjugernath, Deresh
    Clathrate hydrate dissociation data were measured for systems comprising of refrigerants (R134a, R410a and R507) + water + MgCl2 at varying salt concentrations. The ternary system for R134a + water + MgCl2 was measured at salt concentrations of (0.259, 0.546, and 0.868) mol.kg-1 in the temperature range of (277.1-283) K and a pressure range of (0.114-0.428) MPa. Hydrate measurements for the {R410a or R507} + water + MgCl2 systems were measured at salt concentrations of (0.259 and 0.546) mol.kg-1 in the temperature range of (274.3-293) K and a pressure range of (0.154-1.421) MPa. The isochoric pressure-search method was used to measure the hydrate dissociation data. This study is a continuation of previous investigations which focused on obtaining hydrate dissociation data for R134a, R410a and R507 refrigerants in NaCl and CaCl2 aqueous solutions. The measured hydrate dissociation data can be used to design industrial wastewater treatment and desalination processes. The results show that the effect of salt concentration on hydrate formation is smaller for MgCl2 aqueous solutions compared to CaCl2 and NaCl as salt concentration increases. Modelling of the measured data is performed using a combination of the solid solution theory of van der Waals and Platteeuw, the Aasberg-Petersen et al. model, and the Peng-Robinson equation of state with classical mixing rules. The model is in good agreement with the measured hydrate dissociation data.
  • Thumbnail Image
    Item
    Phase stability conditions for clathrate hydrate formation in (fluorinated refrigerant plus water plus single and mixed electrolytes plus cyclopentane) systems : experimental measurements and thermodynamic modelling
    (Elsevier BV, 2019-09) Ngema, Peterson Thokozani; Naidoo, Paramespri; Mohammadi, Amir H.; Ramjugernath, Deresh
    Phase equilibrium conditions (dissociation data) for clathrate hydrates (gas hydrates) were studied for systems involving fluorinated refrigerants + water + single and mixed electrolytes (NaCl, CaCl2, MgCl2 and Na2SO4) at varying salt concentrations in the absence and presence of cyclopentane (CP). The ternary systems for (R410a or R507) + water + CP were performed in the temperature and pressures ranges of (279.8–294.4) K and (0.158–1.385) MPa, respectively. Measurements for {R410a + water + (NaCl or CaCl2) + CP} were undertaken at salt concentrations of (0.10, 0.15 and 0.20) mass fractions in the temperature and pressure ranges of (278.4–293.7) K and (0.214–1.179) MPa, respectively. The temperature and pressure conditions for the (R410a + water + Na2SO4) system were investigated at salt concentration of 0.10 mass fraction in range of (283.3–291.6) K and (0.483–1.373) MPa respectively. Measurements for {(R410a or R507) + water + mixed electrolytes NaCl, CaCl2, MgCl2} were undertaken at various salt concentrations of (0.002–0.15) mass fractions in the temperature and pressure ranges of (274.5–292.9) K and (0.149–1.119) MPa in the absence and presence of CP, for which there are no published data related to mixed salt and a promoter. The phase equilibrium measurements were performed using a non-visual isochoric equilibrium cell and the pressure-search technique. This study was focused on obtaining equilibrium data that can be utilized to design and optimize for water desalination process and the development of a Hydrate Electrolyte–Cubic Plus Association (HE–CPA) Equation of State based model. The results indicate hydrate dissociation pressure reduction/hydrate dissociation temperature increase up to ambient conditions in the presence of promoter (CP). The experimental results were then modelled. The modelling results are in good agreement with the measured hydrate dissociation data.