Estimating The Mass Necessary For A Particular Rankine Cycle

• Bashyboy
In summary, the task is to calculate the efficiency of a Rankine cycle using modified parameters and analyze the results. The original parameters given in the text are T_min = 20 C, T_max = 600, P_min = 0.023 bar, and P_max = 300 bars. The modifications to be made are (a) reducing the maximum temperature to 500 deg. C, (b) reducing the maximum pressure to 100 bars, and (c) reducing the minimum temperature to 10 deg. C. The process involves calculating the entropy at vertex 3 and using interpolation to determine the entropy at vertex 4. The efficiency can then be calculated using the modified parameters and compared to the original efficiency.
Bashyboy
Calculating the Efficiency of A Rankine Cycle For Various Parameters

Homework Statement

Calculate the efficiency of a Rankine cycle that is modified from the parameters used in the text in each of the following three ways (one at a time), and comment briefly on the on the results: (a) reduce the maximum temperature to 500 deg. C; (b) reduce the maximum pressure to 100 bars; (c) reduce the minimum temperature 10 deg. C

Homework Equations

The parameters given the text are T_min = 20 C, T_max = 600, P_min = 0.023 bar, and P_max = 300 bars.

The Attempt at a Solution

At vertex 3, the temperature of the gas is 500 deg. C, and the pressure is 300 bars. Therefore, the entropy of the gas is 5.791, according to table 4.2. Because the process described by the segment 3-4 is adiabatic, there will be no heat lost or gained, which means that entropy will not change due to this; furthermore, the volume changes is small enough to allow us to make the approximation that the entropy does not change very much. Therefore, the water at 3 should have approximately the same entropy as it has at 4. So, I can claim that

$S_3 = S_4$ and $S_4 = S_g + S_l$.

Apparently I am suppose to do some sort of interpolation using the tables, but I am unsure of how to do this.

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Last edited:
Sorry everyone. I gave this thread a title that does not reflect what I am truly asking. This title belongs to a question I was going to originally ask, but I figured out the problem. I am trying the edit my post and change the title name; however, it won't work. If a moderator could change the title to, "Calculating the Efficiency of A Rankine Cycle For Various Parameters," I would appreciate that.

1. What is the purpose of estimating the mass necessary for a particular Rankine cycle?

The purpose of estimating the mass necessary for a particular Rankine cycle is to determine the amount of working fluid (typically water) required to generate a specific amount of power. This can help engineers design more efficient and cost-effective power plants.

2. What factors are considered when estimating the mass for a Rankine cycle?

Several factors are considered when estimating the mass for a Rankine cycle, including the desired power output, the efficiency of the cycle, and the properties of the working fluid (such as specific heat and density). Other factors, such as pressure and temperature, also play a role in the estimation.

3. How is the mass estimated for a Rankine cycle?

The mass for a Rankine cycle is typically estimated using the first law of thermodynamics, which states that energy cannot be created or destroyed. By analyzing the energy inputs and outputs of the cycle, the mass of the working fluid can be calculated.

4. How does the mass estimation affect the overall efficiency of a Rankine cycle?

The mass estimation has a direct impact on the efficiency of a Rankine cycle. A higher mass of working fluid means more energy input and output, which can decrease the overall efficiency of the cycle. Therefore, accurate mass estimation is crucial for optimizing the efficiency of a Rankine cycle.

5. Are there any limitations to estimating the mass for a Rankine cycle?

While estimating the mass for a Rankine cycle can provide valuable insights, there are some limitations to consider. The estimation assumes ideal conditions and does not account for factors such as friction, heat loss, and mechanical losses. Additionally, variations in operating conditions can affect the accuracy of the estimation.

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