Final answer:
The student's question involves calculating the mass flow rate of refrigerant-134a for a Rankine cycle to produce 750 kW power and the cycle's thermal efficiency. Due to missing specific property data, the exact mass flow rate can't be provided, but typically thermal efficiency is the ratio of work output to heat input, and for Carnot efficiency, temperatures must be in Kelvin.
Step-by-step explanation:
The student's question pertains to determining the mass flow rate of refrigerant-134a needed for a Rankine cycle system to produce 750 kW of power and calculating the thermal efficiency of the cycle. The system uses a low-temperature thermal energy boiler that operates at 1.6 MPa, a condenser at 0.4 MPa, and the turbine inlet at 80°C. To solve this engineering thermodynamics problem, a step-by-step approach involving the principles of the Rankine cycle and the properties of the working fluid, refrigerant-134a, would be necessary.
In this analysis, we would use the first law of thermodynamics applied to the steady-flow energy equation for the components of the Rankine cycle, such as turbines, condensers, pumps, and boilers. Using the enthalpies of refrigerant-134a at the various points of the cycle along with the energy output requirement, we could calculate the mass flow rate. Additionally, the thermal efficiency of the cycle is the ratio of the work output to the heat input, which would be determined using the specific enthalpies as well.
However, due to the lack of specific enthalpy values provided in the question, we cannot provide an exact solution. Normally, tables with thermophysical properties of refrigerant-134a or software such as REFPROP would be used to find those values, based on the given pressures and temperatures. A general formula for the thermal efficiency of an ideal Rankine cycle is Efficiency (η) = (W_{out} / Q_{in}) × 100% where W_{out} is the work output and Q_{in} is the heat input to the boiler. Thermal efficiency can also be assessed according to the Carnot efficiency, which is based on the temperature difference between the heat source and the sink; however, this requires converting temperatures to Kelvin.