= Problem 3 (30 Points - Comparing the LMTD and -NTU methods) A boiler used to...

Transcribed Image Text:

= Problem 3 (30 Points - Comparing the LMTD and -NTU methods) A boiler used to generate saturated steam is in the form of an unfinned cross-flow heat exchanger, where water flows through the tubes at a rate of 3 kg/s and a high temperature gas flows over the tubes at a rate of 10 kg/s. The gas has a specific heat of Cp 1120 J/kg-K and enters the heat exchanger at 1400 K. The water enters as saturated liquid at 450 K and leaves as saturated vapor with negligible pressure drop. Note that the enthalpy of evaporation is hfg = 2024 kJ/kg. The overall heat transfer coefficient is 50 W/mK and there are 500 tubes, with the same diameter of 25 mm. (i) Sketch the temperature distribution in the HX. ME410 Heat Transfer, Summer 2023 Homework #6, Due 7/31/2023 (ii) (iii) Using the LMTD method, calculate the length of the pipes required in the heat exchanger. Same as in question (ii), but use the -NTU method. Compare your answers and discuss. = Problem 3 (30 Points - Comparing the LMTD and -NTU methods) A boiler used to generate saturated steam is in the form of an unfinned cross-flow heat exchanger, where water flows through the tubes at a rate of 3 kg/s and a high temperature gas flows over the tubes at a rate of 10 kg/s. The gas has a specific heat of Cp 1120 J/kg-K and enters the heat exchanger at 1400 K. The water enters as saturated liquid at 450 K and leaves as saturated vapor with negligible pressure drop. Note that the enthalpy of evaporation is hfg = 2024 kJ/kg. The overall heat transfer coefficient is 50 W/mK and there are 500 tubes, with the same diameter of 25 mm. (i) Sketch the temperature distribution in the HX. ME410 Heat Transfer, Summer 2023 Homework #6, Due 7/31/2023 (ii) (iii) Using the LMTD method, calculate the length of the pipes required in the heat exchanger. Same as in question (ii), but use the -NTU method. Compare your answers and discuss.