Heat Exchanger Analysis & Design Question Paper 2011 for BPUT M.Tech in Thermal Engineering (Heat Power or Mechanical Engineering) is given below. This is an optional paper in M.Tech 2nd Sem of Thermal Engineering. There is no special book for this paper. But if you are preparing for this subject then solve the questions from the Book HEAT TRANSFER By R.K. Rajput (S. Chand Publication). There is special chapters in this book on Heat Exchanger Analysis.
Second Semester Examination — 2011
Heat Exchanger Analysis & Design Question Paper 2011
Time: 3 Hours
Max. Marks: 70
Answer Question No.1: which is compulsory and any five from the rest.
The figures in the right-hand margin indicate marks.
1. Answer the following questions: 2×10
(a) What are the main selection criteria of a heat exchanger?
(b) Differentiate between regenerators and recuperators and state their scope of application.
(c) Why are baffles used in shell-and-tub heat exchangers?
(d) In a steam condenser, the steam is effectively at as Constant temperature of 50 Degree Celcius throughout the heat exchanger, While the temperature of cooling water increases from 20°C to 31°C as it passes through the condenser. Calculate the NTU for this heat exchanger.
(e) In a hypothetical counter flow gas turbine regenerator, having the same heat capacity rate for fluids, the design NTU and effectiveness are 0.5 and 33% respectively, If at part-load operation, NTU doubles, what will be:the corresponding effectiveness?
(f) Ina heat exchanger, engine oil with a 0.2 kgls flow rate and 130 Degree Celcius inlet temperature is being cooled by water having a 0.438 kg/s flow rate at 90 Degree C inlet. The engine oil and water specific heats are 2.3 and 4.2 kJ/kg-K, respectively. What is the maximum possible exchanger effectiveness if it is a counte flow exchanger?
(g) What are the assumptions in e-NTU and LMTD methods in the analysis of heat exchangers?
(h) How do you define the heat capacity rate of a Matrix? How is it related to the heat capacity of the wall for a rotary regenerator and for a fixed-matrix regenerator?
(i) Explain briefly Bell—Delaware method, used for design of shell-and-tube exchanger:.
(j) What do you mean by flow maldistrubution in a heat exchanger? Enumerate necessary arrangements commonly adopted to reduce the flow maldisribution.
2. Assume that in a condenser, there will be no sub-cooling, and the condensate leaves the condenser at saturation temperature Th. Show that variation of the coolant temperature along the condenser is given by
FORMULA NOT AVAILABLE
3. What are the common causes of fouling in a heat exchanger? How does fouling affect the heat transfer and pressure drop? How is the thermal resistance due to fouling in a heat exchanger accounted for? How do the fluid velocity and temperature affect fouling? Explain techniques to control fouling.
4. Classify heat exchangers according to flow type and construction type. Explain characteristics of each type of heat exchangers. When is a heat exchanger classified as being compact ? Give examples.
5. What is a regenerative heat exchanger? How does a static type heat exchanger differ from Dynamic type? Explain the ‘reduced length” and “reduced period’ Method for ‘determining regenerator performance.
6. Lubricating oil at temperature of 60°C enters a 10 mm diameter tube with a velocity of 2.0 m/s. The tube surface is maintained at 30°C. Calculate the tube length required to cool the oil to 45°C. Consider the following properties for oil : Density p =865 kg/m3, k = 0.14 VV/ m-K. Cp= 1780 J/kg-K, and mu = 0.0078 Pa-s. For oil flow in the tube the heat transfer coefficient h = 51.2 W/m2-K.
7. In an oil-to-water heat exchanger, the oil enters the exchanger at 100°C with a heat capacity rate of 3700 W/K. Water is available at 15°C and 0.6 kg/s. Determine the exit temperatures in parallel-flow arrangement for U = 500W/m2-K and surface area of 10 m2. Consider Cp= 1.88 and 4.19 J./g-K for Oil and water, respectively.
8. At 80 km/h the inlet temperature of air to-an automobile radiator is 37.8 degree C. Water enters at 98.9°C with a flow rate of 1.89 kg/s and leaves with a temperature of 93.3°C. UA for this radiator is 960.6 W/K. Determine the air flow rate and air outlet temperature for this radiator using LMTD method. Consider Cp for air and water as 1.01 and 4.19 KJ/kg-K respectively The radiator is unmixed on the air side and mixed on the water side.