Fluid Mechanics of Mechanical Systems Assignment

A Rankine cycle solar “fired” powerplant, whose working fluid is refrigerant R134a, uses a water-cooled condenser to remove heat from refrigerant gas vapour at its saturated vapour pressure so it condenses back to a liquid. The water components of the system comprise a single-tube, eleven pass condenser (internal length of each pass 1.0 m, thus total length is 11m, with 180 degree bends connecting each pass), a strainer (or filter) to protect the pump, several 90 degree bends, a throttling valve and a cooling tower. From cooling considerations it is required to pass a volume flow of water of 0.2XX litres/second (where XX are the last two digits of one of the team’s student numbers. So, if your student number is 12345678, then your design flow rate is 0.278 L/s). The temperatures of the water before and after the condenser are 10 degrees C and 50 degrees C respectively. Commercial drawn copper tubing of 13.84 mm ID is used in the condenser and for the rest of the system you can choose any other tubing that is commercially available. (See schematic diagram next page).

It is required to provide the system characteristic and match this to a commercially available pump. You must select a pump. The format of the report should be as follows:

1. 1. Cover page
   2. Abstract
   3. Introduction
   4. Body
      1. Discuss your choice of pipe (diameter and material, reference a real pipe). NB Ensure that the velocities in the system are: high enough to entrain air (greater than 0.6 m/s) and low enough to ensure noise will not be a problem (less than 1.3 m/s); and in the condenser discuss if noise, air entrainment and fouling (to avoid fouling – we require flow velocities greater than 1 m/s) will be a problem.
      2. Calculate the system characteristic. You may use your design flow rate to find the three friction factors. One for before the condenser, one in the condenser and one after the condenser, then treat these three friction factors as constants for the rest of the report (i.e. they do not change with changing flow rates). For this step, you need to discuss/list the K loss factors used for every part of the system including the strainer and any other features of the system that introduces K loss factors. Plot the system characteristic (head loss vs flow rate).
      3. Select a pump that will enable the system to pass a flow sufficient to meet at least the design flow rate of the system (the pump need to provide a flow rate greater than the design flow rate, however, will be deemed too big if it provides a head greater than 20 % over the head required at the design flow rate). Provide details of the pump (pump should be an inline pump, not a submersible pump). Plot the pump curve over the system curve and locate the intersection point with its respective flow rate and head.
      4. Throttle the valve (i.e. increase the K value of the valve) until the flow rate of the system is the same as the design flow rate. Plot the pump curve over the new system curve and locate the intersection point with its respective flow rate and head. Provide the new K value of the valve.
      5. Throttle the valve again - find the K value of the valve to achieve half the design flow rate of the system. Plot the pump curve over the new system curve and locate the intersection point with its respective flow rate and head (at half the design flow rate). Provide the new K value of the valve.
      6. Indicate where you will locate the pump and state the reason for its location (show the location of the pump on a diagram). Check that the inlet to the pump is at sufficiently high pressure to avoid cavitation - manufacturers give the allowable inlet static pressure to ensure a long life (NPSHrequired). This is done with a net positive suction head calculation (NPSHavailable). Ensure that the NPSHavailable is greater than the NPSHrequired – this ensures that no cavitation will occur in the pump.
      7. Comment on how you think the performance of the system will vary with time.
   5. Conclusion
   6. References

Write a well-presented FORMAL report which addresses the points above in ord