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AE-JE (ME) || Heat Transfer Quiz - 4

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Question 1

A new heat exchanger is inducted in a power plant with an overall heat transfer coefficient 5000 W/m²-K. After continuous run of 2 years, overall heat transfer coefficient reduces to 2000 W/m²-K due to various factors like chemical deposition, scale and sludge formation. Then what will be fouling factor under this condition?

Question 2

In a heat exchanger, the hot liquid enters with a temperature of 180 °C and leaves at 160°C. The cooling fluid enters at 30 °C and leaves at 110 °C. The capacity ratio of the heat exchanger is

Question 3

In the counter flow heat exchange, for the hot fluid the specific heat is 3 kJ/kg K, mass flow rate is 6 kg/s, inlet temperature is 150 °C and outlet temperature is 100 °C. For the cold fluid, the specific heat is 3 kJ/kg K, mass flow rate is 8 kg/s, inlet temperature is 20 °C . Neglecting the heat transfer to surrounding, the outlet temperature of the cold fluid in °C is ________.

Question 4

In a counter-flow heat exchanger, the cold fluid enters at 20°Cand leaves at 40°C. The hot fluid enters at 140°C and leaves at 120°C. What is the heat transferred per unit area per unit overall heat transfer coefficient?

Question 5

After expansion from a gas turbine, the hot exhaust gases are used to heat the compressed from a compressor with the help of a counter flow compact heat exchanger of 0.6 effectiveness. The number of transfer units of the heat exchanger is _________.

Question 6

In a counterflow heat exchanger the hot fluid is cooled from 140° to 110°C by a cold fluid which get heated from 70°C to 100°C . The overall heat transfer coefficient is 250 W/m² – K and heat transfer area is 2 m². If both the fluids have identical mass flow rate specific heat product. Then the heat transfer rate is (in kW) __________?

Question 7

For the same inlet and outlet temperatures of hot and cold fluids, the Log Mean Temperature Difference (LMTD) is

Question 8

For the parallel flow heat exchange the effectiveness is 0.4 and capacity ratio is unity, then NTU is___.

Question 9

In a shell and tube heat exchanger, baffles are provided on the shell side to ________.

Question 10

A cross-flow type air heater has an area of 50 m². The overall transfer coefficient is 100 W/m²K; and heat capacity of the stream, be it hot or cold, is 1000 W/K. What is the NTU?

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AE & JE Exams Mechanical Engineering

Dec 28AE & JE Exams