A food factory uses hot water to wash and clean foods. The drained water, which has...

  

Transcribed Image Text:

A food factory uses hot water to wash and clean foods. The drained water, which has a mass flow rate of 0.1 kg/s, still have a temperature of 62C. Consider a concept design solution of waste heat recovery for pre-heating fresh water, which has an inlet temperature of 15C and mass flow rate of 0.2 kg/s inside tube flow. The following information can be used for your design: 2 shell-pass and any multiple of four tube passes (4, 8, 12, etc., tube passes) heat exchanger may be considered. The shell side heat transfer coefficient could be assumed as 300 W/m K. The most popular copper pipe of 15 mm internal diameter could be used. Total pipe length should not be longer than 60 meters. For inside pipe flow, fully developed turbulent flow and Dittus and Boelter correlation may be assumed, Nu = 0.023Re 0.8 Pr.n 0.7 Pr 160 Re> 10,000 where n = 0.4 for heating, n = 0.3 for cooling of fluid flowing through the tube A clear justification of the heat exchanger design and calculations should be included, also to state why it should be deployed in terms of energy saving. Assumptions: steady operating conditions, the heat exchanger is well insulated, properties are constant, the thermal properties for the shell side water can be assumed based on 45C, and the thermal properties in tube side water can be assumed based on 25C; no kinetic & potential energies changes, the overall heat transfer coefficient is constant, the thickness of the tube wall is negligible. (NB: The total cost of the heat exchanger including the installation could be about 30k, and the factory may not be interested in any project that has a payback period of more than 2.5 years. If the cost of natural gas is 30 pence per kWh.) A food factory uses hot water to wash and clean foods. The drained water, which has a mass flow rate of 0.1 kg/s, still have a temperature of 62C. Consider a concept design solution of waste heat recovery for pre-heating fresh water, which has an inlet temperature of 15C and mass flow rate of 0.2 kg/s inside tube flow. The following information can be used for your design: 2 shell-pass and any multiple of four tube passes (4, 8, 12, etc., tube passes) heat exchanger may be considered. The shell side heat transfer coefficient could be assumed as 300 W/m K. The most popular copper pipe of 15 mm internal diameter could be used. Total pipe length should not be longer than 60 meters. For inside pipe flow, fully developed turbulent flow and Dittus and Boelter correlation may be assumed, Nu = 0.023Re 0.8 Pr.n 0.7 Pr 160 Re> 10,000 where n = 0.4 for heating, n = 0.3 for cooling of fluid flowing through the tube A clear justification of the heat exchanger design and calculations should be included, also to state why it should be deployed in terms of energy saving. Assumptions: steady operating conditions, the heat exchanger is well insulated, properties are constant, the thermal properties for the shell side water can be assumed based on 45C, and the thermal properties in tube side water can be assumed based on 25C; no kinetic & potential energies changes, the overall heat transfer coefficient is constant, the thickness of the tube wall is negligible. (NB: The total cost of the heat exchanger including the installation could be about 30k, and the factory may not be interested in any project that has a payback period of more than 2.5 years. If the cost of natural gas is 30 pence per kWh.)

Answer rating: 100% (QA)

The images youve provided contain a design brief for a food factorys hot water system which intends to reclaim heat from drained hot water to preheat fresh water The information includes specific para... View the full answer