### Recent Question/Assignment

ENG790s2 Energy Systems
Online Coursework
Deadline For Submission: 15 May 2020
Instructions for completing the Please see coursework brief assessment:
Examiners: Dr James Buick, Dr Jovana Radulovic
The numerical values in this coursework are based on your student number.
Your student number is a six-digit code UP QWERTY. In the assignment below you should replace letters Q, W, E, R, T, Y with digits from your student number. If any of the numbers are 0, please use the subsequent number.
You are required to design a combustion-based thermal system to produce Q0 kg/s of liquid water at (50 + 5*W) °C , from a source of water at 10°C. You should specifically consider the following aspects:
• The properties of the fuel you will use
• The rate at which the fuel will be consumed and the flow rate of air required
• The optimal design of the heat exchanger you will use
Your design should be supported by relevant calculations for each section including:
Combustion analysis: Select a fuel to be used in your combustion unit. For this fuel, determine the mass flow rate of the fuel and air, under stoichiometric conditions, which is required. You also need to consider an analysis of the breakdown of gases in the exhaust. Dissociation effects can be neglected.
Transport: Combustion products are routed to the heat exchanger through a steel pipe (k = 60 W/mK) of E0 mm outside diameter, W mm wall thickness, and R00m length. The representative environmental conditions involve air 0 °C and velocity of T m/s in a cross flow over pipe. A Y mm-thick coating of insulation (k = 0.02 W/mK) is at the outer surface of the pipe. Determine the temperature of combustion gases at the pipe outlet. Determine the savings associated with application of the insulation layer compared to the heat loss from an uninsulated pipe.
Heat Exchanger size: Combustion products (leaving the pipe in part 2) are used to heat water to (50 + 5*W) °C in a heat exchanger. The flow rate of the water is Q0 kg/s. The overall heat transfer coefficient of the heat exchanger is 155 W/(m2 K) based on a surface area of R0 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 combustion gases.
Note that the three sections are not independent, for example, the flow rate of fuel will depend on the details of the losses in the connecting pipe and 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 fuel mass flow rate
• The air mass flow rate
• The dimensions of the heat-exchanger
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.
The marking scheme is given below.
Assumptions and general considerations 5%
Calculations: Combustion analysis 15%
Calculations: Transport 15%
Calculations: Heat Exchanger size 15%
Discussion and Analysis 20%
5% variation calculations and analysis 30%
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