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The surface renewal frequency in Danckwerts model of mass transfer is given by (KL: mass transfer co-efficient)

The surface renewal frequency in Danckwerts model of mass transfer is given by (KL: mass transfer co-efficient) Correct Answer $$\sqrt {{{\text{K}}_{\text{L}}}^2 \cdot {{\text{D}}_{\text{A}}}} $$

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The surface renewal frequency in Danckwerts model of mass transfer is given by (KL: mass transfer co-efficient)
A stream of air at 100 kPa pressure and 300 K is flowing on the top surface of a thin flat sheet of solid naphthalene of length 0.2 m with a velocity of 20 m/sec. The other data are: Mass diffusivity of naphthalene vapor in air = 6 * 10 –6 m2/sec Kinematic viscosity of air = 1.5 * 10 –5 m2.sc Concentration of naphthalene at the air-solid naphthalene interface = 1 * 10 – 5 kmol/m3 Calculate the overage mass transfer coefficient over the flat plate. Note: For heat transfer over a flat plate, convective heat transfer coefficient for laminar flow can be calculated by the equation. Nu = 0.664 ReL1/2 Pr1/3 you may use analogy between mass and heat transfer.
Experimental results indicate that the local heat transfer coefficient h g for flow over a flat plate with an extremely rough surface is approximated by the relation h x = a x -0.12 Where a is a constant coefficient and x is distance from the leading edge of the plate. What is the relation between this local heat transfer coefficient and the average heat transfer coefficient for a plate of length x?
The Weberian model of bureaucracy has been criticised from a variety of stand points.
Consider the following points in this regard:
1. The Weberian model appears to be a 'machine theory' and a closed system model taking little account of organisational interactions with the environment.
2. The structural features of bureaucracy as laid down by Weber might be suitable for routine and repetitive tasks but these would produce dysfunctional consequences in terms of human behaviour if the jobs would involve innovation and creativity.
3. Weberian model has not been found to respond adequately to the tasks of socioeconomic transformation in the developing countries. These tasks require quick changes whereas the capacity of the Weberian model for adaptation to change is rather slow.
4. Weber's model is confined to the study of formal bureaucratic structure and fails to take notice of the informal structure of bureauracy such as informal relations, informal norms and values, an informal power hierarchy and informal power struggles.
Which of the above points make a valid criticism of the Weberian model? Select the correct answer from below:
A finned surface consists of root or base area of 1m2 and fin surface area of 2m2. The average heat transfer coefficient for finned surface is 20W/m2K effectiveness of fins provided is 0.75. If finned surface with surface with root or base temperature of 50°C is transferring heat to fluid of 30°C, then the rate of heat transfer without using fin is _______
What is the monoisotopic and average mass of valine? Given data: Mass of the most abundant isotope of Carbon (C°)=12.0000, Mass of most abundant isotope of Hydrogen (H°)=1.0078, Mass of most abundant isotope of Oxygen (O°)=15.9949, Mass of most abundant isotope of Nitrogen (N°)=14.0031, The average mass of Carbon (C)=12.011, The average mass of Hydrogen (H)=1.008, The average mass of Oxygen (O)=15.999, The average mass of Nitrogen (N)=14.007.
Statement 1: Penetration theory states that mass transfer coefficient is directly proportional to diffusivity coefficient which was later proved wrong. Statement 2: Penetration theory states that mass transfer is based on unsteady mass transfer.
Surface renewal model of mass transfer was enunciated by
The plum pudding ( first model )of the atom was proposed by JJ Thomson. Which of the following is/are the limitations of the Thomson model (i) The model wasn't able to explain the alpha scattering (ii) The model failed to explain the position of nuclei  (iii) The model failed to explain how the positive charges hold the negative charges (iv)The model failed to explain the existence of electrons in an atom 
User level threads are threads that are visible to the programmer and are unknown to the kernel. The operating system kernel supports and manages kernel level threads. Three different types of models relate user and kernel level threads. Which of the following statements is/are true ? (a) (i) The Many - to - one model maps many user threads to one kernel thread (ii) The one - to - one model maps one user thread to one kernel thread (iii) The many - to - many model maps many user threads to smaller or equal kernel threads (b) (i) Many - to - one model maps many kernel threads to one user thread (ii) One - to - one model maps one kernel thread to one user thread (iii) Many - to- many model maps many kernel threads to smaller or equal user threads