JNTU
JNTU B.Tech III PROCESS HEAT TRANSFER Previous Question Paper (November/December - 2018 - R13)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks and may have a, b, c as sub questions.
Part A
Define natural convection.
Answer
Natural convection is a mode of heat transfer where fluid motion is caused by buoyancy forces resulting from density differences due to temperature variations within the fluid, rather than by external mechanical means like a pump or fan.
Define Fourier’s Law of heat conduction.
Answer
Fourier's Law states that the rate of heat conduction through a material is directly proportional to the area normal to the direction of heat flow and the temperature gradient in that direction. Mathematically:
where q is the heat transfer rate, k is thermal conductivity, A is the area, and dT/dx is the temperature gradient.
Draw the temperature profiles for concurrent and counter current flows.
Answer
Sign in to view the complete answer paper.
Explain about LMTD.
Answer
Sign in to view the complete answer paper.
Write about thermal boundary layer.
Answer
Sign in to view the complete answer paper.
What are the regimes of heat transfer in fluids? Explain.
Answer
Sign in to view the complete answer paper.
Explain about sub cooled boiling.
Answer
Sign in to view the complete answer paper.
Explain about pool boiling of saturated liquid.
Answer
Sign in to view the complete answer paper.
What is fin efficiency?
Answer
Sign in to view the complete answer paper.
Write about air cooled exchangers?
Answer
Sign in to view the complete answer paper.
Part B
Derive the expressions for heat flow through a cylinder and a sphere.
Answer
Sign in to view the complete answer paper.
A flat Furnace wall is constructed of a 114 mm Layer of Sil-O-cel brick, with thermal conductivity of 0.138 W/m°C. The temperature of the inner face of the wall is 760°C and that of the outer face is 76.6°C. Calculate (a) What is the heat loss through the wall? (b) What is the temperature of the interface between the refractory brick and common brick?
Answer
Sign in to view the complete answer paper.
Derive the equation for individual and overall heat transfer coefficients.
Answer
Sign in to view the complete answer paper.
Write about fouling factors.
Answer
Sign in to view the complete answer paper.
Carbon tetrachloride flowing at 19000 kg/h is to be cooled from 85°C to 40°C using 13500 kg/h of cooling water at 20°C. The film coefficient for carbon tetrachloride outside the tubes is 1700 W/m²°C. The wall resistance is negligible, but hi on the water side, including fouling factors, is 1100 W/m²°C.
What area is needed for a counter flow exchanger?
Answer
Sign in to view the complete answer paper.
By what factor would the area be increased if parallel flow were used to get more rapid initial cooling of the carbon tetrachloride?
Answer
Sign in to view the complete answer paper.
Explain about heat transfer by turbulent eddies and analogy between transfer of momentum and heat.
Answer
Sign in to view the complete answer paper.
Explain about hydro dynamic boundary layer.
Answer
Sign in to view the complete answer paper.
Derive the equation for laminar flow heat transfer to flat plate.
Answer
Sign in to view the complete answer paper.
Explain about heat transfer to liquid metals.
Answer
Sign in to view the complete answer paper.
A double walled flask may be idealized to be equivalent to two infinite parallel plates. The emissivity’s of walls are 0.3 and 0.7 respectively. The space between them is evacuated. A shield of polished aluminum of e=0.05 is inserted between them. Find the reduction in heat transfer due to insertion of radiation shield.
Answer
Sign in to view the complete answer paper.
Derive the expression to find the heat transfer coefficient for film type condensation for vertical tubes.
Answer
Sign in to view the complete answer paper.
Explain about combined heat transfer by Conduction, Convection and Radiation.
Answer
Sign in to view the complete answer paper.
Discuss in detail about methods used for feeding a multiple evaporation system.
Answer
Sign in to view the complete answer paper.
What is the effect of liquid head and boiling point elevation for multiple effect evaporator?
Answer
Sign in to view the complete answer paper.
Write the differences between Vapor recompression, Mechanical recompression and Thermal recompression.
Answer
Sign in to view the complete answer paper.
Write about the forced circulation evaporators with neat diagrams.
Answer
Sign in to view the complete answer paper.