MT-Peer Discussion - Session-1

The meeting covered various aspects of mass transfer, including convective mass transfer, diffusion, and humidification and drying processes. Participants discussed theoretical concepts, solved sample problems, and derived equations related to mass transfer coefficients, evaporation rates, and drying regimes. The session concluded with an overview of humidity calculations and a brief mention of distillation as the next topic to be covered in the following week.

Karthikeyan explained the coverage of mass transfer coefficients, convective mass transfer, and diffusion topics, noting that Janarth would handle humidification and drying. He discussed solving problems related to convective mass transfer, including calculating the mass transfer coefficient and evaporation rate, and derived the necessary units for these calculations.

Karthikeyan explained the conversion of units in a chemical calculation and demonstrated how to manipulate units to match those given in the problem. He also provided an overview of the theory behind convective mass transfer, discussing the relationship between partial pressures, mole fractions, and mass flux in both gas and liquid phases.

Karthikeyan explained the theory behind mass transfer coefficients, emphasizing the importance of units in determining which coefficient is being used. He discussed how to derive the overall mass transfer coefficient and the equations to use for gas and liquid phases. Karthikeyan then worked through a sample problem, explaining how to determine which mass transfer coefficient is being used based on the given units.

Karthikeyan explained the process of calculating the overall mass transfer coefficient and molar flux using given formulas and data. He demonstrated how to find the interface mole fraction by substituting known values into the appropriate equations. Karthikeyan encouraged the audience to review the material and suggested that proceeding with the given method would be appropriate for solving the problem.

Karthikeyan explained the concept of mass transfer and how to calculate the time it takes for a substance to reach 95% of its equilibrium concentration in an unsteady state problem. He emphasized the importance of using mass balance equations and integrating them to find the required time, considering the units and assumptions involved. Karthikeyan also discussed the relationship between mass flux, concentration, and area, and highlighted the need to assume uniform concentration within the system for simplicity.

Karthikeyan explained a mathematical problem involving integration and substitution, emphasizing the importance of correctly substituting variables and converting units. He solved the problem step-by-step and provided the final answer. Janarth then took over to discuss the topic of humidification and drying, introducing a problem from a previous gate exam. He explained the approach to solving the problem, focusing on understanding the different regimes of drying and calculating the mass of the drying solid per unit area.

Janarth derived equations for both the concentrate and falling rate drying regimes, solving for the time required in each. He found that the total drying time for the falling rate regime was 2.4 hours, and the mass of dry solid per unit area was 34.6 kg/m². Janarth noted that the critical equilibrium moisture was assumed to be 0, and the drying regimes were analyzed from point 3.5 to point 2 for the concentrate regime and up to point 0 for the falling rate regime.

Janarth explained how to solve a problem involving humidity and wet bulb depression using the Antoine equation and mass balance equations. He outlined the steps to find the saturation vapor pressure, absolute humidity, and wet bulb temperature, emphasizing the importance of using the correct units and assumptions. Janarth also discussed the concept of humid heat and how to apply it to the problem.

Janarth explained how to solve a problem involving the calculation of specific humidity using the energy balance equation. He demonstrated the steps to find the value of y dash, which represents the mass of water vapor per unit mass of dry air, and showed how to multiply by 1,000 to get the final value of 11.1 kg of water per kg of dry air. Janarth also mentioned that the next question would involve using a similar energy balance approach to find the initial humidity of air entering a saturator.

The meeting focused on solving equations related to drying processes, including the determination of moisture content and drying rates in different regimes. Janarth explained the steps to solve a problem involving the drying of alumina particles, including the use of equations for the constant and falling rate regimes. He emphasized the importance of understanding the drying mass and area, as well as the integration of equations to find the total drying time. Karthikeyan mentioned that the next topic would be distillation, which would be covered in the following week. The session concluded with an invitation for participants to ask any questions they might have about the covered topics.