Energy Losses

T

he energy losses can be classified under two categories;
  • Conversion losses
  • Transmission losses

Conversion losses:


Conversion process associated with all heat engines (such as steam, gas etc.) are primarily dictated by the laws of thermodynamics. Accordingly, no heat engine can ever produce work more than Carnot cycle engine that works between the same reservoir (Th) and sink (Tl) temperatures. Therefore, work potential of any energy conversion process can be readily assessed using this concept and given as follows.

Wp = Qc(1 - Tl/Th)

Where Qc is the amount of energy converted or transferred from the reservoir to the medium. Any difference in the actual work and the work potential can be measured as conversion loss.

Transmission losses


Transmission losses are energy losses that occur between two energy conversion devices. Transmission loss in case of electrical energy system can be as high as 10% from the generating source to the consumer. Similarly, flow energy (pressure) loss coupled with heat in case of fluids can be much greater. Energy losses increase as the fluid transmission line between the source and the load become longer.

The Flow Joule program can analyze flow energy losses associated with most common fluids such as steam, water, air, fuel-air mixes passing through pipes and conduits for any given upstream and down stream conditions. It also facilitates investigation of all scalling and excessive pipe pressure drops. For example, a 5% reduction in diameter due to scaling can cause almost 27% increase in the pressure drop for the water to flow at the same original designed rate. Consequently, it needs 27% more energy to pump water through this conduit. This can also further offset the pump efficiency due to the increase in the total head. All flow energy losses are computed using steady flow process model as per Bernoulliís law. This is the main modeling principle followed in all fluid circuits

Transmission losses in mechanical systems often are considered to be a part of the conversion device efficiency and can be generalized as follows.

IHP = BHP + FHP
Mechanical efficiency = BHP/IHP

Where IHP: Indicated horsepower (input); BHP: Brake horsepower (output);
FHP: Frictional Horsepower that measures the rate at which a mechanical energy is being converted into heat and dissipated back to the sink. This is the amount of heat generated due to friction between various mechanical elements such as shaft and bearings; speed reduction gear drives; belt drives etc.

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