What? Selection Optimisation of ABB’s Wind Turbine Generator Performance by InstallingA Heat Pipe Heat Exchanger oc ? Presented by: Haytham Abdulwahab The United Arab Emirates University II
Overview - Increase in the temperature difference safety margin, which allows increasing the loading. - extending the life of the insulation, and thus the life of the generator.
- Increase in the temperature difference safety margin, which allows increasing the loading. - extending the life of the insulation, and thus the life of the generator.
What? What? What’s a heat pipe? What reasons behind choosing a heat pipe to solve the problem Whatconsideration should be taken in designing a heat pipe? What could limit the operation of a heat pipe? What procedures are taken to design a heat pipe? What other things should we be awared of? What do you need to ask more? What What?
Why a heat pipe was considered? 1.A heat pipe will transport the heat to a location where it can be effectively dissipated by natural or forced convection. 2.The heat pipe provides a thermal path through the enclosure wall, while the internal air cycle is kept close. 3.There will be no need for extra cooling fan that would consume extra power; since the original cooling fan used to drag cooling air for the primary cooling unit is the one to be used in the cooling of the heat sink by forced convection. 4.The product maintenance requirements are eliminated or reduced. And no noise source does exist. ?
Heat Pipe Fundamentals: Thermal Design: - Evaporator - Adiabatic - Condenser( Heat Sink) Manufacturer: - Container - Working Fluid - Wick Structure (operation against gravity)
Selection Materials Selection Creteria: Container Material: 1.The container should isolate the working fluid from the outside environment. 2.The container should also enable heat transfer to take place from and into the working fluid. 3.The container material should be compatible with both the working fluid and external environment. 4.A material with good fabrication properties including weldibility, machineability and ductility, is preferable. Selection
Selection Materials Selection Creteria: Working Fluid Material: 1. Compatibalityof the working fluid with the container material. 2.The thermal stability of the working fluid. 3.High latent heat a high latent heat of vaporization and high thermal conductivity. 4.Low values of vapor and liquid viscosities to minimize the resistance to fluid flow. 5.Acceptable freezing point in comparison to the operating temperature range. Selection
Selection Materials Selection Creteria: - Methanol was fluid of choice. Methanol would provide a temperature potential capable of driving the required amount of heat because of its low value of boiling point Tsat. Since methanol freezes at a very low temperature, -97C, it is useful in gravity-aided, pool boiling applications where water heat pipes would be subject to freezing. - Copper for evaporator tubes, and aluminum for condenser fins. materials with good fabrication properties and good thermal properties in addition to compatability with working fluid of choice. Selection
NuD = 1.13C1C2Remmax Pr 1/3 Δp=NLχ(χρairV2max/2)f Evaporator Design
Evaporator Tubes Design Summery: All the dimensions and geometry details are shown in the figure beside 18 circular pipes of 25mm. The cross section of the pipe array is cantered a distance of 237.5mm from the axis of the generator. Each pipe is made of copper and has a wall thickness of 2mm. The average convection heat transfer coefficient based on the velocity of air at the centre of the array is equal to 47.5 W/m2.oC The total heat transfer to the evaporator tubes is equal to 1692W The total weigh of evaporator tubes filled with methanol is 42kg. The empty tubes weigh 35kg. The time required for the heat pipe to start working is 8 minutes.
Heat Sink Design Summery: All the dimensions and geometry details are shown in the figure above. 49 L-shaped rectangular aluminium fins will be attached on the inner surface of the air duct using a glue material that has a thermal conductivity of 0.95 W/m.oC. The methanol vapor will be contained between this surface and a 510mm diameter concentric cylindrical surface forming the heat pipe heat sink.
Heat Sink Design Summery: The natural convection heat transfer coefficient on the outer surface of the heat sink was found to be 4.77 W/m2.oC. The emmisivity ε of paint material on the outer surface was taken to be 0.85 This gives us a total of heat transfer to the outside equal to 309W.
Heat Sink Design Summery: Based on an average air velocity inside the duct of 13.443 m/s, the forced convection heat transfer coefficient on the inner surface of the heat sink was found to be 33.3kW/m2.oC
Heat Sink Design Summery: And thus the heat emitted by the fins is equal to 687W. While the heat emitted by the wings is equal to 103W. The rest unfinned area emits 551W. A total amount of heat transfer to the air driven by the duct fan equal to 1341W The total amount of heat emitted by the heat sink is equal to 1650W. The temperature of the inner surface of the heat sink is equal to 63.6 oC.
Alternative Design [Acetone Heat Pipe] Just12 evaporator tubes! Butwe will need more than 40 extra fins. II
Recommendations! It is highly recommended to check a safety data sheet or a hazard sheet that provides information about safety about dealing with methanol.
Recommendations! Since the wind turbine will be used in a marine environment, a surface coating is required to protect the heat sink assembly, where dissimilar materials are being attached to each other (aluminum fins on steel wall), from galvanic corrosion.
Recommendations! When monitoring heat pipe performance, the key parameter is the temperature difference between the surfaces of the evaporator and the condenser.
Recommendations! Don’t use the same heat pipe design for two different working fluids.
? Thanks for Listening! ? ? ? ? ? What questions do you have?