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Gerd Maurer - One of the best experts on this subject based on the ideXlab platform.
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simultaneous solubility of so2 and nh3 in salt h2o and Enthalpy Change upon dilution of so2 nh3 salt h2o in salt h2o salt nh4 2so4 or na2so4 experimental results and model predictions
Fluid Phase Equilibria, 2006Co-Authors: Eckehard Meyer, Viktor Ermatchkov, Alvaro Perezsalado Kamps, Gerd MaurerAbstract:Abstract The simultaneous solubility of sulfur dioxide and ammonia in aqueous solutions of (ammonium sulfate or sodium sulfate) was measured by a synthetic method in the temperature range from 313.6 to 373.2 K and at pressures up to 2.5 MPa. Furthermore, the Enthalpy Change upon diluting aqueous solutions of sulfur dioxide, ammonia and (ammonium sulfate or sodium sulfate) in aqueous solutions of the same salt was measured in a batch calorimeter at about 313 and 352 K. The experimental results are used for comparison with predictions from a thermodynamic model for the vapor–liquid equilibrium and the Enthalpy of dilution of those chemical reacting systems. In that model, activity coefficients are calculated from Pitzer's molality-scale-based Gibbs excess energy model, where all interaction parameters are either adopted from previous investigations on the properties of the binary and ternary sub-systems (if available) or they are neglected (if they are not available).
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Enthalpy Change on vaporization of aqueous and methanolic formaldehyde solutions
AIChE Journal, 1992Co-Authors: Y.‐q. Liu, Hans Hasse, Gerd MaurerAbstract:A physicochemical model for vapor-liquid equilibrium in multicomponent formaldehyde-containing mixtures (Maurer, 1986; Hasse et al., 1990; Hasse and Maurer, 1991a). is extended to describe Enthalpy Changes upon vaporization. Predicted Enthalpy Changes are compared with new experimental results. The measurements were carried out with a thin-film evaporator flow-calorimeter (Liu and Maurer, 1991). More than 80 experimental data points for mixtures of formaldehyde + water and formaldehyde + methanol + (small amounts of water) are reported. The data cover the temperature range from 323 to 363 K (formaldehyde + water) and 312 to 347 K (formaldehyde + methanol) at liquid phase formaldehyde mole fractions up to about 0.3 (formaldehyde + water) and 0.6 (formaldehyde + methanol). Comparisons between predicted and experimental results for the Enthalpy Change reveal deviations of only a few percent. Further improvements are achieved by fitting some model parameters, which originally were estimated from noncalorimetric data.
Yat Huang Yau - One of the best experts on this subject based on the ideXlab platform.
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analysis of Enthalpy Change with without a heat pipe heat exChanger in a tropical air conditioning system
International Journal of Energy Research, 2006Co-Authors: Yat Huang YauAbstract:In an earlier paper (Yau, 2006. Application of a heat pipe heat exChanger to dehumidification enhancement in tropical HVAC systems—a baseline performance characteristics study. Int. J. Thermal Sci., accepted for publication), the baseline performance characteristics of the 8-row wickless heat pipe heat exChanger (HPHX) were established for it being used in a vertical configuration under tropical climate conditions. The present paper covers the tests and simulation conducted on the same experimental HVAC system without the HPHX installed, thereby determining the Enthalpy Change for the air passing through the chilled water coil (CWC) alone (i.e. without the pre-cooling or reheating effect of the HPHX). These experimental results, in comparison with those already obtained, would also allow an examination of how the reheat recovery with the 8-row HPHX installed was influenced by the same key inlet parameters. The final results show that the Enthalpy Change with a HPHX installed for all cases examined are significantly higher than Enthalpy Change without a HPHX installed, demonstrating that the cooling capability of the CWC was enhanced by the HPHX. Copyright © 2006 John Wiley & Sons, Ltd.
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Analysis of Enthalpy Change with/without a heat pipe heat exChanger in a tropical air conditioning system
International Journal of Energy Research, 2006Co-Authors: Yat Huang YauAbstract:In an earlier paper (Yau, 2006. Application of a heat pipe heat exChanger to dehumidification enhancement in tropical HVAC systems—a baseline performance characteristics study. Int. J. Thermal Sci., accepted for publication), the baseline performance characteristics of the 8-row wickless heat pipe heat exChanger (HPHX) were established for it being used in a vertical configuration under tropical climate conditions. The present paper covers the tests and simulation conducted on the same experimental HVAC system without the HPHX installed, thereby determining the Enthalpy Change for the air passing through the chilled water coil (CWC) alone (i.e. without the pre-cooling or reheating effect of the HPHX). These experimental results, in comparison with those already obtained, would also allow an examination of how the reheat recovery with the 8-row HPHX installed was influenced by the same key inlet parameters. The final results show that the Enthalpy Change with a HPHX installed for all cases examined are significantly higher than Enthalpy Change without a HPHX installed, demonstrating that the cooling capability of the CWC was enhanced by the HPHX. Copyright © 2006 John Wiley & Sons, Ltd.
Michael Haumann - One of the best experts on this subject based on the ideXlab platform.
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Enthalpy Changes during Photosynthetic Water Oxidation Tracked by Time-Resolved Calorimetry Using a Photothermal Beam Deflection Technique
Biophysical journal, 2007Co-Authors: Roland Krivanek, Holger Dau, Michael HaumannAbstract:Abstract The energetics of the individual reaction steps in the catalytic cycle of photosynthetic water oxidation at the Mn 4 Ca complex of photosystem II (PSII) are of prime interest. We studied the electron transfer reactions in oxygen-evolving PSII membrane particles from spinach by a photothermal beam deflection technique, allowing for time-resolved calorimetry in the micro- to millisecond domain. For an ideal quantum yield of 100%, the Enthalpy Change, Δ H , coupled to the formation of the radical pair YZ ⋅ + QA − (where Y Z is Tyr-161 of the D1 subunit of PSII) is estimated as −820±250meV. For a lower quantum yield of 70%, the Enthalpy Change is estimated to be −400±250meV. The observed nonthermal signal possibly is due to a contraction of the PSII protein volume (apparent Δ V of about −13A 3 ). For the first time, the Enthalpy Change of the O 2 -evolving transition of the S-state cycle was monitored directly. Surprisingly, the reaction is only slightly exergonic. A value of Δ H (S 3 ⇒S 0 ) of −210 meV is estimated, but also an Enthalpy Change of zero is within the error range. A prominent nonthermal photothermal beam deflection signal (apparent Δ V of about +42A 3 ) may reflect O 2 and proton release from the manganese complex, but also reorganization of the protein matrix.
P. Claudy - One of the best experts on this subject based on the ideXlab platform.
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Enthalpy Change and temperature of the reversible monoclinic-orthorhombic phase transition in MFI type zeolitic materials
Thermochimica Acta, 1996Co-Authors: B.f. Mentzen, J. M. Letoffe, P. ClaudyAbstract:Calorimetric investigations show that the Enthalpy Change corresponding to the reversible and displacive monoclinic (P21n.1.1) ↔ orthorhombic (Pnma) solid state phase transition in MFI type zeolitic materials presenting several SiAl ratios is very sensitive versus the framework aluminum content. For ≈0.01 E > 1.8 kJ/mol. ΔH rapidly decreases with increasing Al content and the transition temperature Tt for strictly anhydrous materials is always above 50°C. In the case of air-equilibrated phases, the extra-framework water content increases with Aluc and beyond ≈ 1.3 – 1.4 Aluc Tt is below 20°C. Tt is also sensitive versus the nature and the amount of sorbed or encaged guest molecules (e.g., water, aliphatic and aromatic hydrocarbons).
G. Catalani - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamics of dipeptides in water. V. calorimetric determination of Enthalpy Change values related to proton transfer processes of a series of dipeptides in water
Thermochimica Acta, 1997Co-Authors: F. Rodante, F. Fantauzzi, G. CatalaniAbstract:Abstract We have made calorimetric determination of Enthalpy Change values related to proton dissociation processes (for a series of dipeptides having α-alanine as first common term) of the free α-amino groups belonging to the amino terminal residue (N-terminal) and of the free α-carboxyl groups belonging to the carboxyl terminal residue (C-terminal). These values were subsequently compared with those related to proton dissociation processes of the corresponding groups of alanyl-alanine and of the individual free α-amino acids. The results were interpreted in terms of reciprocal influence of the components of the dipeptides.