The pressurized water that enters a cross-flow heat exchanger with a flow of 1 kg / s at 35 ° C and leaves at 125 ° C, where fluids do not mix, is heated by exhaust gases entering the heat exchanger at 300 ° C and exiting at 100 ° C. . The total heat transfer coefficient defined according to the surface on the gas side is 100 W / m ° K. Thermal properties of exhaust gases are considered as atmospheric air. a) Find the required surface area on the gas side. (15P) Due to the contamination that occurs over time, the inlet temperature and flow rate of the water in the heat exchanger remain the same, while the outlet temperature drops to 105 ° C *. a) Calculate the new condition with the acceptance of fixed thermal properties, b) Heat transfer,

The pressurized water that enters a cross-flow heat exchanger with a flow of 1 kg / s at 35 ° C and leaves at 125 ° C, where fluids do not mix, is heated by exhaust gases entering the heat exchanger at 300 ° C and exiting at 100 ° C. . The total heat transfer coefficient defined according to the surface on the gas side is 100 W / m ° K. Thermal properties of exhaust gases are considered as atmospheric air. a) Find the required surface area on the gas side. (15P) Due to the contamination that occurs over time, the inlet temperature and flow rate of the water in the heat exchanger remain the same, while the outlet temperature drops to 105 ° C *. a) Calculate the new condition with the acceptance of fixed thermal properties, b) Heat transfer,

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter10: Heat Exchangers

Section: Chapter Questions

Problem 10.40P

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A gas turbine exhaust stack cooler drops the gas temperature from 1020oF to 605°Fby means of a water cooling coil. Cooling water enters the coil at 65°F and leaves,after a counter-flow passage, with a temperature of 190°F. If cp for the gas is 0.26Btu/lb.F, calculate the overall heat transfer coefficient for an exchanger area of2000 ft2, Btu/hr.ft2.F.A. 19.94 B. 29.94 C. 39.94 D. 49.94
C by Water (heat capacity = 4.174 kJ/kg: ° C) at a rate of 10 kg/min is heated from 20 ° C to 60 ° oil that has a specific heat of 1.9 kJ/kg: ° C. The oil enters the shell side of the heat exchanger at 120 ° C and leaves at 70 ° C. The overall heat transfer coefficient is 350 W/m2 · ° C. (a) Use the log mean temperature difference method to calculate the heat exchanger area if a counter flow double pipe heat exchanger is used. (b) Use the effectiveness-NTU method to calculate the heat exchanger area if a counter flow double pipe t heat exchanger is used. (c) Use the log mean temperature difference method to calculate the heat exchanger area if a 2-4 shell and tube heat exchanger is used. (d) Use the effectiveness-NTU method to calculate the heat exchanger area if a 2-4 shell and tube heat exchanger is used.
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A compressor is used to increase air pressure with the assumption that there is no heat transfer from/to the compressor. The air is entering at 150 kPa and 37 C and leaving at 650 kPa and 227 C with 250 kg/min as mass rate. The constant-pressure specific heat of air is 1.011 k/kg, and the gas constant is 0.287 k/kg.K while the surrounding is 27"C and 100 kPa. a. Deterrmined the entropy charnges of air after the process. b. Determine the reversible power of the compressor in kW.
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In a heat exchanger, the heat transfer depends on the choice of the control volume
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