Mechanical Systems

- How to write and solve an energy balance for a closed system.

Explanation: Energy balances on mechanical systems, just as open system energy balances, are derived from the closed system energy balance. It is used for systems in which kinetic energy, potential energy, or shaft work are of prime importance. Derivation: closed system balance, splitting up the work terms: _{k} + ΔE_{p} = Q - W_{s} - W_{flow}_{k} + ΔE_{p} + F = -W_{flow} - W_{s}Doing some rearranging, substituting the definitions of W ΔP/ρ + Δu^{2}/2 + g*Δz + F-hat = - W_{s}-dot / m-dotMechanical System Energy Balance Equation: ^{2}/2 + g*δz + F-hat = - W_{s}-dot / m-dotA modified form of this equation, used for a frictionless (F=0) process with no moving parts (W
^{2}/2 + g*Δz = 0ΔP = 0 if the inlet pressure is equal to the outlet pressure Δu Δz = 0 if the system doesn't move vertically |

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