Consider the feed water heater as the control volume and apply the first law of thermodynamics to obtain,. Energy added in the boiler per unit mass of the working fluid,. Energy rejected in the condenser,. Thermal efficiency,. Air standard Otto cycle on a P-v diagram b T-s diagram. Processes : -. Since the net work done in processes and is zero, for thermodynamic analysis, we consider the only.
The thermal efficiency of the cycle is given by. Energy is absorbed during the process Energy is rejected during the process For an ideal gas undergoing an isentropic process process and ,. Hence we get,. Where the compression ratio r 0 is defined as. The thermal efficiency of the Otto cycle increases with the specific heat ratio, g of the working fluid. Heat transfer can be achieved using a heat exchanger regenerator.
There are two types of feed water heaters: open and closed. The open feed water heater is essentially a mixing chamber, where the steam extracted from turbine is combined with water from the pump.
The fluid that exits the mixing chamber is saturated water. The closed feed water heater is a heat exchanger, inside which the steam condenses on the outside of the tube carrying the feed water. As a result, the feed water temperature is increased. The pressures of the steam and the feed water do not need to be matched since the flows are not mixing. Without heat regeneration, the feed water temperature would be much lower and would require more energy from the heat source for the boiler.
Regeneration helps raise the overall efficiency of the system. The following reading material contains more details on the Rankine cycle and other power conversion cycles that potentially now or in the future can be applied to utility-scale solar power systems. Book chapter : Stine, W. This reading contains some thermodynamic language that may be beyond the scope of this course, but stay cool.
Your goal of studying this material will be quite practical - compare the Rankine, Brayton, and Stirling cycles and extract information on the following:. Skip to main content. Rankine cycle Print 7. Rankine cycle We are going to overview the principle of thermodynamic cycle operation using Rankine cycle example, since most of solar power cycles currently operating are Rankine cycles. Figure Rankine cycle layout. Credit: Andrew. Have a look at the following image from the steam engine wiki article.
At step 2 we can see heat is added to the fluid in the boiler making it a gas. Then in step 3 it expands through the turbine giving us power output. Then on step 4 we need the condenser to remove the heat and condense this expanded gas back into a fluid. That way the fluid can be easily pumped with a small amount of power input into the high pressure boiler.
The pump and the turbine have roughly the same pressure drop across them, but since a much larger volume moves through the turbine, it produces more power than is consumed by the pump. Conversely if we tried to not condense the gas and pump it back into the boiler, it would take more energy to pump it than we would get out of the turbine.
Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Why does a thermodynamic cycle need a condenser? Ask Question. Asked 5 years, 8 months ago. Active 5 years, 8 months ago.
Viewed 4k times. Improve this question. The steps in the Rankine Cycle as shown in Figure 1 and the corresponding steps in the pressure volume diagram figure 2 are outlined below: [1]. The efficiency of the Rankine cycle is limited by the high heat of vaporization by the fluid.
The fluid must be cycled through and reused constantly, therefore, water is the most practical fluid for this cycle. This is not why many power plants are located near a body of water—that's for the waste heat. As the water condenses in the condenser, waste heat is given off in the form of water vapour —which can be seen billowing from a plant's cooling towers. This waste heat is necessary in any thermodynamic cycle. Due to this condensation step, the pressure at the turbine outlet is lowered.
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