If a system expands a small volume against a constant external pressure, a small

Question

If a system expands a small volume against a constant external pressure, a small quantity of energy is transferred as work to the surroundings. What is the expression for the work transferred? For a closed system with no change in system velocity or vertical position, where the only work is from the expansion, simplify the energy balance. The specific enthalpy of a liquid hydrocarbon at 1 atm varies linearly with temperature at equals 25 kJ/kg at 30C and 130 kJ/kg at 50C. Determine the equation relating specific enthalpy to temperature, and calculate the temperature reference temperature for which the given enthalpies are based. Derive an equation for U(T) at 1 atm. Calculate the heat transfer rate required to cool the liquid hydrocarbon, flowing at 30 kg/min from 60C to 25C at a constant pressure of 1 atm. What is the change in specific internal energy for this change?

Explanation / Answer

1) If external pressure Pext and Volume change occurs from V1 and V2 , therefore, work done by the system,

w = Pext (V2-V1)

2) Internal energy change occurs during work done.

3)

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