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23/05/2011

Competitive stages

 

Availability of spare parts
  Hoop strength (to withstand internal tube pressure)
  Buckling strength (to withstand overpressure in the shell)
  Tube length: heat exchangers are usually cheaper when they have a smaller shell diameter and a long tube length. Thus, typically there is an aim to make the heat exchanger as long as physically possible whilst not exceeding production capabilities.jewellery manufacturers However, there are many limitations for this, including the space available at the site where it is going to be used and the need to ensure that there are tubes available in lengths that are twice the required length (so that the tubes can be withdrawn and replaced). Also, it has to be remembered that long, thin tubes are difficult to take out and replace.

What are the allowable pressure drops and velocities in the exchanger?
  Pressure drops are very important in exchanger design (especially for gases).  As the pressure drops, so does viscosity and the fluids ability to transfer heat.freshwater pearl   Therefore, the pressure drop and velocities must be limited.  The velocity is directly proportional to the heat transfer coefficient which is motivation to keep it high, while erosion and material limits are motivation to keep the velocity low.  Typical liquid velocities are 1-3 m/s (3-10 ft/s).  Typical gas velocities are 15-30 m/s (50-100 ft/s).  Typical pressure drops are 30-60 kPa (5-8 psi) on the tubeside and 20-30 kPa (3-5 psi) on the shellside.

Day 2 brought even better stage times for the team with Marius starting to extract most of the awesome potential of the VW.  Road conditions continued to degrade and the high rate of attrition for the event carried on, with more fall outs due to crashes or mechanicals, but the Polo just got stronger.

Ironically,tahitian pearlMarius and Gerard pushed the car through nearly 230km of competitive stages, without a scratch or a hiccup, only to throw the car off the road twice just 3km from the end of the very last stage of the rally, resulting in about a minute of lost time before getting back onto the road and back up to pace.

Tube pitch: when designing the tubes, it is practical to ensure that the tube pitch (i.e., the centre-centre distance of adjoining tubes) is not less than 1.25 times the tubes' outside diameter. A larger tube pitch leads to a larger overall shell diameter which leads to a more expensive heat exchanger.
  Tube corrugation: this type of tubes,golden south sea pearl mainly used for the inner tubes, increases the turbulence of the fluids and the effect is very important in the heat transfer giving a better performance.
  Tube Layout: refers to how tubes are positioned within the shell. There are four main types of tube layout, which are, triangular (30°), rotated triangular (60°), square (90°) and rotated square (45°). The triangular patterns are employed to give greater heat transfer as they force the fluid to flow in a more turbulent fashion around the piping. Square patterns are employed where high fouling is experienced and cleaning is more regular.