LMTD – Heat Exchangers Questions | Gate

Heat Exchangers- LMTD

  • 1. In a condenser of a power plant, the steam condenses at a temperature of 60 degree Celsius. the cooling water enters at 30 degree Celsius and leaves at 45 degree Celsius. the logarithmic mean temperature difference(LMTD) of the condenser is
  • 2. Water (Cp =4.18 kj/kgk) at 80 C enters a counter flow heat exchanger with a mass flow rate of 0.5kg/s. AIr (Cp= 1kj/kgk) enter at 30C with a mass flow rate 2.09 kg/s . if the effectiveness of the heat exchanger is 0.8, the LMTD is
  • 3. Cold water flowing at 0.1 kg/s is heated from 20 C to 70 C in a counter flow type heat exchanger by a hot water stream flowing at 0.1kg/s and entering at 90 C. the specific heat of water is 4200 j/kgk and density is 1000 kg/m3. if the overall heat transfer coefficient U for the heat exchanger is 2000W/m2k, the required heat exchange area (in meter square) is
  • 4. The LMTD of a counter flow heat exchanger is 20 C. the cold fluid enters at 100 C. Mass flow rate of the cold fluid is twice that of the hot fluid. specific heat at constant pressure of the hot fluid is twice that of the cold fluid. The exit temperature of the cold fluid is
  • 5. In a counterflow heat exchanger, hot fluid enters at 60 C and cold fluid leaves at 30 C. Mass flow rate of the hot fluid is 1kg/s and cold fluid is 5kj/kgk. the LMTD for the heat exchanger in C is
  • 6. Hot oil is cooled from 80 to 50 C in an oil cooler which uses air as the coolant. The air temperature rises from 30 to 40 C. The designer uses a LMTD value of 26 C. The type of heat exchanger is
  • 7. In a condenser, water enters at 30 C and flows at the rate 1500 kg/hr. The condensing steam is a temperature of 120 C and cooling water leaves the condenser at 80 C. specific heat of water is 4.187 kj/kgk. if the overall heat transfer cofficient is 2000 W/m2k, the heat transfer are is
  • 8. Air enters a counter flow HE at 70 C and leaves at 40 C. water enters at 30 C and leaves at 50 C, the LMTD in degree Celsius is
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Questions –> Effectiveness By NTU Method

 

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