Organic Rankine Cycle

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ÇUKUROVA UNIVERSITY ENGINEERING AND ARCHITECTURE FACULITY DEPARTMENT OF MECHANICAL ENGINEERING DESIGN PROJECT NAME OF SUBJECT: ORGANIC RANKINE CYCLE FOR HEAT ACTIVATED COOLING SUBMITTED BY: ASSOC. PROF. ALPER YILDIRIM MECHANICAL ENGINEERING DEPARTMENT 17 OCTOBER 2011 PREPARED BY: AYTAÇ ŞANLISOY STUDENT NO: 2011911608 CONTENTS 1 INTRODUCTION ........................................................................................................................... 3 1.1 1.2 2 RANKINE CYCLE ..
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  ÇUKUROVA UNIVERSITYENGINEERING AND ARCHITECTURE FACULITYDEPARTMENT OF MECHANICAL ENGINEERINGDESIGN PROJECTNAME OF SUBJECT: ORGANIC RANKINE CYCLE FOR HEAT ACTIVATED COOLINGSUBMITTED BY:ASSOC. PROF. ALPER YILDIRIMMECHANICAL ENGINEERING DEPARTMENT17 OCTOBER 2011PREPARED BY: AYTAÇ ŞANLISOY  STUDENT NO: 2011911608   CONTENTS1   INTRODUCTION ........................................................................................................................... 3 1.1   RANKINE CYCLE ................................................................................................................. 3 1.2   ORGANIC RANKINE CYCLE .............................................................................................. 4 2   THERMODYNAMIC ANALYSIS OF CYCLE ............................................................................ 4 2.1   1st Law cycle performance ...................................................................................................... 5 2.2   2nd Law cycle performance .................................................................................................... 5 3   ANALYSIS OF WORKING FLUID .............................................................................................. 6 4   REFERANCES ............................................................................................................................... 8  1   INTRODUCTION1.1   RANKINE CYCLE TheRankine Cycleis a thermodynamic cycle used to generate useful work and electricity in manypower stations, engineering applications and is the real-world approach to theCarnot Cycle.  İdeal rankine cycle is represented in figure 10-2.1-2 Isentropic compression in a pump2-3 Constant pressure heat addition in a boiler3-4 Isentropic expansion in a turbine4-1 Constant pressure heat rejection in a condenserFluid enters the pump at state 1 as saturated liquid and is compressed isentropically to the operatingpressure of the boiler. The fluid temperature increases somewhat during this isentropic compressionprocess due to a slight decrease in the specific volume of water. Fluid enters the boiler as acompressed liquid at state 2 and leaves as a superheated vapor at state 3. The boiler is basically a largeheat exchanger where the heat srcinating from combustion gases, nuclear reactors, or other sources istransferred to the water essentially at constant pressure. The boiler, together with the section where thesteam is superheated (the superheater), is often called the steam generator. The superheated vapor atstate 3 enters the turbine, where it expands isentropically and produces work by rotating the shaftconnected to an electric generator or turbo-compressor. The pressure and the temperature of steamdrop during this process to the values at state 4, where steam enters the condenser. At this state, steamis usually a saturated liquid  –  vapor mixture with a high quality. Steam is condensed at constantpressure in the condenser, which is basically a large heat exchanger, by rejecting heat to a coolingmedium such as a lake, a river, or the atmosphere. Steam leaves the condenser as saturated liquid andenters the pump, completing the cycle. Remembering that the area under the process curve on a T-sdiagram represents the heat transfer for internally reversible processes, we see that the area underprocess curve 2-3 represents the heat transferred to the water in the boiler and the area under theprocess curve 4-1 represents the heat rejected in the condenser. The difference between these two (thearea enclosed by the cycle curve) is the net work produced during the cycle.  1.2   ORGANIC RANKINE CYCLE The organic Rankine cycle (ORC) uses an organic fluid such as n-pentane or toluene in place of waterand steam. This allows use of lower-temperature heat sources, such as solar ponds, which typicallyoperate at around 70  –90°C The efficiency of the cycle is much lower as a result of the lowertemperature range, but this can be worthwhile because of the lower cost involved in gathering heat atthis lower temperature. Alternatively, fluids can be used that have boiling points above water, and thismay have thermodynamic benefits.In recent years renewable energy sources such as solar, wind, and geothermal have played increasinglyimportant roles in satisfying energy needs. One method to use thermal sources of renewable energy isthe organic Rankine cycle (ORC), which can utilize low-to-moderate grade heat. Resources includinggeothermal, solar thermal and waste heat fall into this category for the purposes of power generation.Generally in industry, industrial low-grade waste heat accounts for more than 50 percent of heatgenerated. In general, heat is considered to be moderate-to low grade if its temperature is less than 370 °C, which is relevant to steam power plants based on the Rankine cycle. Since a wide range of fluidchoices exist, ORCs have the advantage of operating with good relative efficiency over a wide range of temperatures, for example, from120°C to 370°C. Depending on the application, waste heat from aprocess could be used to generate useful energy such as shaft work, electricity, or cooling that can beused by another process. This reduces the energy consumption of the overall system. 2   THERMODYNAMIC ANALYSIS OF CYCLE
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