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Design of a Heat Recovery System of a Mining Truck Using Flow Network Modeling (FNM)
Design of Ventilation Systems of Rotating Machinery
Design of a Heat Recovery System of a Mining Truck Using Flow Network Modeling (FNM)
This study involved the design of an innovative heat recovery system used in a mining truck. The large mining trucks use
a very high-capacity engine for fulfilling the large power requirement at the mining site. It is therefore desirable to recover the waste heat from the large amount of hot exhaust generated by the
engine. The heat recovery mechanism involves directing the flow through the beams supporting the dump platform. The objective of the design was to minimize the back-pressure at the engine exhaust
while recovering as much heat as possible.
The flow system involved a number of hollow beams of various cross-sections joined to each other, creating a complex
system for the flow to travel from the engine exhaust to the atmosphere. The Flow Network Modeling (FNM) program MacroFlowTM was used to represent the flow system as a network of ducts, bends, orifices (formed at the joint of two beams), and tee and cross junctions. Most parts of the system were standard and correlations for pressure loss and heat transfer were readily available. In parts of the system where these correlations were not available, COMPACTTM-based
CFD analysis was used to determine the performance characteristics. MacroFlow-based analysis allowed prediction of the flow rates and pressure drops in all parts of the system and back-pressure at
the engine exhaust. This enabled identification of the parts of the system in which the pressure drops are large and localized. Modifications, such as rounding of the bends and incorporation of
ducts to provide parallel paths, were incorporated and their effect on the heat recovery and back-pressure was analyzed. After several interactive modifications, an optimum design of the
flow/structural system was determined. The final design was validated on a prototype and then deployed in practice. Note that a conventional design method would have involved an iterative testing
on a prototype - a procedure that would be very expensive and time consuming given the scale of the physical system involved. Use of MacroFlow-based analysis significantly shortened the design
cycle and enabled determination of an effective design at substantially reduced cost.
Design of Ventilation Systems of Electric Machinery
Large electric machines involve eddy losses in the motor winding and require design of efficient cooling systems to
ensure reliable operation. One of the commonly used strategies is forced air-cooling. The air flow is induced due to the centrifugal force created by the rotation of the rotor and in some cases by
blowers attached at the ends of the rotor. The air then travels through the passages in the stator where it absorbs the generated heat before flowing out of the system.
The ventilation flow in such a system is determined by the interaction of the fan/centrifugal head and the resistances
of the complex flow passages in the stator and the rotor. Detailed analysis of the entire systems using Computational Fluid Dynamics (CFD) is very time consuming due to the time required for
problem set up, solution, and post-processing. The FNM technique in MacroFlow is ideally suited for such analysis because the network description of the flow system is very accurate and the
resulting solution is very fast. This allows rapid and scientific analysis of the effect of design parameters on the performance of the ventilation systems and for investigation of new cooling
strategies.
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