Thermodynamics Power Cycle Energy Balance

[AGiantGolden49er]

Homework Statement

As shown in Fig. P5.39, a system undergoing a power cycle develops a net power output of 1 MW while receiving energy by heat transfer from steam condensing from saturated vapor to saturated liquid at a pressure of 100 kPa. Energy is discharged from the cycle by heat transfer to a nearby lake at 17°C. These are the only significant heat transfers. Kinetic and potential energy effects can be ignored. For operation at steady state, determine the minimum theoretical steam mass flow rate, in kg/s, required by any such cycle.

Fig. 5.39: https://gyazo.com/49a3ca702a5fa239633f8f054618345e
(Can't get it to embed)

Homework Equations

η = W_cycle / Q_H = 1 - T_C / T_H
W_cycle = Q_H - Q_C
mass flow: dm_cv / dt = ∑ m_i - ∑ m_e
energy balance: dEcv / dt = Q - W + ∑ m_i(h_i + V_i² / 2 + gz_i)- ∑ m_e(h_e + V_e² / 2 + gz_e)

The Attempt at a Solution

Knowing that the system operates at steady state, I know that the entry mass flow and exit mass flow are the same. I also know that since kinetic energy and potential energy can be ignored, the energy balance equation simplifies to:
0 = Q - W + ∑ m_i(h_i)- ∑ m_e(h_e) =>
W = Q + m(h_i - h_e)

Knowing that the initial and final states are at saturated vapor and saturated liquid, respectively, using the tables in the back of the book, I found the specific enthalpy values to be:
h₁ = 2675.5 kJ/kg
h₂ = 417.46 kJ/kg

I know that I can use the thermal efficiency relation to find the Q_H value, but I don't know how exactly to find the thermal efficiency since there's no listed T_H value, unless I'm missing something in the problem statement. I feel that the energy balance equation will be cake once the heat transfer value is found, but I just can't figure out how to get it. If anyone could steer me in the right direction, that would be appreciated.

Edit: The temperature of the lake is 17°C, not 178C. Copy-and-paste didn't recognize the degree symbol.

 

[CWatters]

Not my field but... isn't 100kPa about atmospheric pressure so the temperature of the steam would be...

 

[Chestermiller]

What would be the ratio of Qh to Qc if the system were operating reversibly (at maximum theoretical efficiency)? (Qh is the rate of heat addition from the steam reservoir).