P23875 Energy Systems - University of Portsmouth
You are required to design a thermal system to produce 20 kg/s of liquid water at 65 °C, from a source of water at 10°C. Heat is provided from exhaust gas at 300°C, with mass flow rate of 35 kg/s.
You should consider several designs and advise on the optimal heat exchanger you will use.
Your design should be supported by relevant calculations for each section including:
Transport: Exhaust gas is routed to the heat exchanger through a steel pipe (k = 60 W/mK) of 30 mm outside diameter, 3 mm wall thickness, and 500m length. The representative environmental conditions involve air 6 °C and velocity of 8 m/s in a cross flow over pipe. A 5 mm-thick coating of insulation (k = 0.02 W/mK) is at the outer surface of the pipe. Determine the temperature of exhaust gas at the pipe outlet. Determine the savings associated with application of the insulation layer compared to the heat loss from an uninsulated pipe. Advise whether an alternative insulative material can be used and what would be the effect.
Heat Exchanger size: Exhaust gas (leaving the pipe) is used to heat water to 65°C in a heat exchanger. The flow rate of the water is 20 kg/s. The overall heat transfer coefficient of the heat exchanger is 155 W/(m2 K) based on a surface area of 50 m2. Determine the effectiveness of the heat exchanger (you should consider at least two types), the heat transfer rates, and the outlet temperatures of the exhaust gas from the heat exchanger.
Note that the two sections are not independent, for example, the losses in the connecting pipe will affect the desired performance of the heat exchanger.
You should also consider how the performance of the system would be affected by a 5% variation in the heat exchanger area.
You should submit the report showing your main findings and analysis. Detailed calculations should be shown in the Appendix or in a spreadsheet. You must clearly state all assumptions made and discuss how these affect the accuracy of your findings.
Attachment:- Energy Systems.rar