scholarly journals Spin Freezing and Its Impact on Pore Size, Tortuosity and Solid State

Pharmaceutics ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2126
Author(s):  
Joris Lammens ◽  
Niloofar Moazami Goudarzi ◽  
Laurens Leys ◽  
Gust Nuytten ◽  
Pieter-Jan Van Bockstal ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Solid State ◽  
Pore Size ◽  
Freeze Drying ◽  
Product Layer ◽  
Mass Transfer Resistance ◽  
Transfer Resistance ◽  
X Ray ◽  
Spin Freezing ◽  
The Impact

Spin freeze-drying, as a part of a continuous freeze-drying technology, is associated with a much higher drying rate and a higher level of process control in comparison with batch freeze-drying. However, the impact of the spin freezing rate on the dried product layer characteristics is not well understood at present. This research focuses on the relation between spin-freezing and pore size, pore shape, dried product mass transfer resistance and solid state of the dried product layer. This was thoroughly investigated via high-resolution X-ray micro-computed tomography (µCT), scanning electron microscopy (SEM), thermal imaging and solid state X-ray diffraction (XRD). It was concluded that slow spin-freezing rates resulted in the formation of highly tortuous structures with a high dried-product mass-transfer resistance, while fast spin-freezing rates resulted in lamellar structures with a low tortuosity and low dried-product mass-transfer resistance.

scholarly journals Investigation of Inlet Gas Relative Humidity on Performance Characteristics of PEMFC Operating at Elevated Temperature

2021 ◽  
Vol 12 (3) ◽  
pp. 110
Author(s):  
Yiming Xu ◽  
Guofeng Chang ◽  
Jienan Zhang ◽  
Yuyang Li ◽  
Sichuan Xu
Keyword(s):  
Mass Transfer ◽  
Relative Humidity ◽  
Polarization Curve ◽  
Operating Temperature ◽  
High Current Density ◽  
Proton Exchange ◽  
Mass Transfer Resistance ◽  
Transfer Resistance ◽  
Output Performance ◽  
The Impact

Raising the operating temperature is considered to be an effective method to improve the output performance of proton exchange membrane fuel cells (PEMFCs). In this paper, the effects of inlet relative humidity in the anode (RHa) and cathode (RHc) on the polarization curve and impedance spectra of a single rotating serpentine PEMFC were investigated by experimental method at the operating temperature of 90 °C. It was found that the output performance is the smallest in the high RH case (RHa90%/RHc90%) due to the largest mass transfer resistance. However, the ohmic resistance in the dry case (RHa50%/RHc50%) is the highest, and it shows better output performance at more than 1.0 A/cm2 because of the lowest mass transfer resistance. The impact of the changes in the RHa value on the polarization curve is more apparent than that of the RHc changes at high current density. The largest power density can be attained and the efficiency can reach 24.4% when the RHa is 90% and RHc is 50%.

Analysis of Heat and Mass Transfer Between a Desiccant-Air System in a Packed Tower

1987 ◽  
Vol 109 (2) ◽  
pp. 89-93 ◽  
Author(s):  
P. Gandhidasan ◽  
M. Rifat Ullah ◽  
C. F. Kettleborough
Keyword(s):  
Mass Transfer ◽  
Gas Phase ◽  
Heat And Mass Transfer ◽  
Packing Material ◽  
Mass Transfer Resistance ◽  
Liquid Desiccant ◽  
Governing Equations ◽  
Packed Tower ◽  
Transfer Resistance ◽  
Steady State Model

Heat and mass transfer analysis between a desiccant-air contact system in a packed tower has been studied in application to air dehumidification employing liquid desiccant, namely calcium chloride. Ceramic 2 in. Raschig rings are used as the packing material. To predict the tower performance, a steady-state model which considers the heat and mass transfer resistances of the gas phase and the mass transfer resistance of the liquid phase is developed. The governing equations are solved on a digital computer to simulate the performance of the tower. The various parameters such as the effect of liquid concentration and temperature, air temperature and humidity and the rates of flow of air and liquid affecting the tower performance have been discussed.

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