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Interview Q/A

Q1 what are your favorite subjects?

▶️my favorite subjects are chemical engineering thermodynamics and heat transfer


Q2 what do you know about fins?

▶️fins are extensions on the exterior surfaces of objects that increase the rate of heat transfer to or from the object by increasing convection. This is achieved by increasing the surface area of the body


Q3 where are fins used? 

▶️a. Heat dissipation is an unavoidable by-product of electronic devices and circuits. To ensure an efficient heat transfer, fins are attached to the surface to dissipate heat into the environment. For example, in the cooling system of graphics card. 

b. Heat loss by conduction through furnace wall must be dissipated into the surrounding through convection. This is done with the help of fins


Q4 what are the assumptions of Fourier’s law?

▶️1. Heat flow is one directional

2. Bounding surfaces are isothermal in nature. Constant and uniform temperature is maintained at 2 faces.

3. Material is isotropic and homogeneous, and thermal conductivity k is constant

4. Temperature gradient is constant and temperature profile is linear.


Q5 designing of a heat exchanger

▶️ designing of a heat exchanger means calculating the area required for the given heat transfer. The factors which are considered are the type of process such as condensation, reboiling, evaporation, vaporization, cooling and heating, and the type of heat exchanger to be used such as shell and tube, plate and double pipe heat exchanger.


Q6 what are baffles? 

▶️Baffles are flow-directing or obstructing vanes or panels used shell and tube heat exchangers. A baffle is designed to support tube bundles and direct the flow of fluids for maximum efficiency.


Q7 can same baffles be used in condenser and heat exchanger? 

▶️in condensers, horizontal baffles are preferred. This is because Horizontal baffles decrease the velocity of steam/water mixture and, hence, reduce erosion of condenser tubes. Moreover the distribute steam/water mixture along the whole length of condenser tubes, intensifying heat exchange. They also direct condensate to the sides of condenser and, hence, reducing water film on condenser tubes and reduce aerodynamic resistance of condenser.

In shell and tube heat exchanger, impingement baffles are used to protect tube bundle by direct colloding of the fluid to the tube bundle.


Q8 what is dittus boilter equation and it’s use

▶️ dittus boilter equation is used for turbulent flow inside the pipe to calculate heat transfer coefficient.

Nu= 0.023 x Re^0.8 x Pr^n 

n = 0.3 for cold fluid 

n = 0.4 for hot fluid


Q9 how is the pressure head dependent on velocity in turbulent and laminar flow?

-> doubt


Q10 Hagen Poiseuille equation

▶️∆P= 32.L.μ.v/D^2

It is used to calculate head loss due to friction in pipe for a fully developed laminar flow.

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