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  1. K

    VAWT, wind induction factor

    I'm trying to model a vertical axis wind turbine with the double-multiple streamtube model (with Matlab), where wind speed is dampened by an induction factor so that the output is different for upwind and downwind parts of rotation. The trouble is that for the downwind part, the induction...
  2. K

    Convective heat transfer coefficients

    Hi. I'm trying to make a simple model of a condensation based countercurrent heat exchanger where liquid water and steam flows are separated by a conducting wall. I formed the equations as Q = \frac{T_{steam}-T_{water}}{\frac{1}{Ah_{water}}\frac{d}{Ak_{wall}}\frac{1}{Ah_{steam}}} = L\dot{m}...
  3. K

    How does electricity power devices?

    I've been wondering how or why electricity actually works. Resistance heaters and light bulbs just turn the kinetic energy of electrons into heat, but what about more complex devices? For example, why does a microwave oven do something useful when electrons flow in the circuitry?
  4. K

    Cooling trouble

    Air conditioner cools the air in a room with a power of 8.4*10^6J/h. Volume of the room is 62.5m^3. At first the air is at the temperature of 30C and air pressure is 1atm, which stays a constant. How long does it take to cool the room to 25C? Note that the air shrinks while cooling down and...
  5. K

    Ideal gas problems

    There are some problems which have me completely stumped. 1. A balloon has a volume of 10.5dm^3. Its mass is 8.5g and inside is helium at a pressure of 1.05atm. Atmospheric pressure is 1.00atm and both the helium and the outside air is 25.0C (degrees Celcius). Define the tension in the...
  6. K

    Problem with fluid flow.

    I have a sylindrically shaped canister (open from the top) with a height of 25.0cm and a radius of 5.00cm. At the bottom there is a hole with an area of 1.50cm^2 spraying out water. How long does it take to empty the canister? Subscripts t and b stand for top and bottom and h is the height...