Written by Chaitanya Rane
Monday, December 18, 2017
Generating more with less ! Duct design optimization for efficient power plant
By
Chaitanya Rane
Efficiency is money | Every Power Industry in the World !
Every power generating industry in the world deals with conversion of Energy from one form to another. Efficiency plays a vital role in this process. It reflects directly on the cost of power production and thus an efficient system is what every power industry looks forward to.
Economisers
Layout of Boiler, Economiser, Flue Gas Duct and other Components
Economisers are one such component that are instrumental in improving Thermal Power Plant Efficiency. Economisers use the waste flue gases from the boiler furnace to preheat the water entering into the boiler. Ducts are used to transport the flue gases from the furnace to the economiser. There is a rise in pressure drop across such ducts which affects the air flow into the economiser. This in turn reflects on the efficiency of the power plant.
So how do we solve this issue ?
The major cause of pressure losses in ducts and pipes are sudden changes in direction of flow and friction losses due to the surface of the duct. I made an attempt here to bring a gradual change in direction by using fillets and reducing the length of the duct by reducing the bend angle. Lets see how that worked out for me !
A Square Duct is used to connect the Boiler and the Economiser. The installation constraints and the position of the components demand the use of a duct with minimum 2 bends. Pressure losses are clearly evident due to the presence of these bends. The experiment shall aim at reducing this pressure loss and ensure the flow is uniform as it enters the Economiser.
Flow across a Straight Duct of 8.5m length
*Note: All Pressure values are Gauge Pressures in Pascal.
The air enters the duct with a mass flow rate of 1.4 kg/s. A Static pressure of 0 Pa is considered at the outlet. The pressure loss across a straight duct of 8.5m shall be considered as the reference value.
A comparison will be made between the pressure losses across the design modification and the reference. An increase in pressure drop within 20% of the reference value shall be considered as a good design. I have used Generic Simulation App by simulationHub for the CFD analysis and calculation of pressure drop across the ducts.
Design Modifications
Generic Simulation to my Rescue !
For my experiment I had to simulate the air flow in all the designs mentioned above. A standard CFD Simulation has to go through CAD Modelling, Fluid Domain Extraction, Meshing, Simulation Run and Post Processing ! Performing these tasks for all the 5 Designs can be very tedious.
No Worries ! Generic Simulation by simulationHub comes to my rescue here. A task which should have taken days is now merely completed in hours. Generic Simulation makes it very designer friendly and takes the complexity of a CFD Simulation out of my experiment. To be honest, it has taken me longer to write this blog than it took to complete the simulations ! Within hours I was ready with the results and could analyse the problem at hand.
Time for the Results !
Flow across the Duct
Flow at the Entrance of the Economiser
The above comparisons show us that there is a qualitative improvement in the flow with every design modification. A more uniform flow shall enhance the efficiency of the economiser.
Pressure Drop Across the Ducts
Flow at the Entrance of the Economiser
The reduction in length and gradual change in direction certainly improves the Pressure Drop across the duct. With minimum energy lost in the duct and an uniform air flow into the economiser will contribute to make the system more efficient.
This will reflect in the cost of energy production and shall be beneficial to the power plant.
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