Nozzle and diffuser air flows through an adiabatic and horizontal placed pipe with changeable cross section. Thermodynamic analysis of reciprocating compressors. Only the compression process can be adjusted by varying n, the polytropic index. A thermodynamic model, simulating a single compression stroke, is developed to investigate the heat transfer phenomena inside the compression chamber.
Thermodynamic analysis of three compressed air energy. The isentropic compressor work for an ideal gas is given by. Isothermal compression is represented by the same formula as boyles law. The process involves some work, called compression. Any compressor has an inlet and outlet via which fluid enters and leaves. Jun 06, 2016 the thermodynamics of air compressors is quite complex, but there are some general rules that can be used to help people understand what happens in the air system. Microscopic thermodynamics or statistical thermodynamics macroscopic thermodynamics or classical thermodynamics a quasistatic process is also called a reversible process intensive and extensive properties intensive property. As gases are compressible, the compressor also reduces the volume of a gas. Sep 04, 2015 homework statement air enters a compressor at 100kpa and 20 oc in steady flow rate. You will study the principles of reciprocating compressors in detail and some principles of rotary compressors.
However, simple explanations, although not perfectly accurate, are sufficient to convey the information needed to understand everyday experiences. Engineering and chemical thermodynamics, 2nd edition milo d. In theory, the compressor must be designed so that heat generated can also be extracted at an equal rate. Energy is supplied to compress air, and when energy is required this compressed air is allowed to expand through some expansion turbines. Thanks for contributing an answer to physics stack exchange. Thermodynamics and heat transfer laboratory manual edition. Air enters an adiabatic compressor at 300 k, 1 atm pressure. The heat loss is 10% of the power of the compressor. So, even though there is pressure rise in compressor, we are calculating work by using specific heat at constant pressure, which is fine if we only look at this as a slight mathematical manipulation.
We compared the rigorous method results with the values from the shortcut methods. Late in the 19th century a french genius, professor auguste rateau, invented the centrifugal compressor. During the expansion work will be done by the fluid to drive, for example, electric generation. Josephs college of engineering department of chemical engineering page 5 design of the evaporator, compressor condenser requires the knowledge of the rate of circulation of refrigerant m lqcl. After the engine is running for a sufficient time approx. Electricity is supplied by the grid to run the air compressors and charge the storage system. A global model for the thermodynamic analysis of reciprocating compressors is presented. Finally, we know the thermodynamic processes from b to c and from d to a are adiabatic, which means the system did not gain or lose heat during these. The model is based on five main and four secondary dimensionless physically meaningful parameters.
The work input to the compressor is 350 kj per kg of air. Jilin university with a background in hvac and thermodynamic engineering. It may also run at a different speed to the compressor. Application of the first law of thermodynamics to the. The second law of thermodynamics states that heat can never of its own effort transfer from a lowertemperature region to a higher temperature region. Evaluate the performance of a typical twostage air compressor. The first law of thermodynamics when you have completed section two, you should be able to explain and use the following terms. In this paper, an exergy analysis was presented based on the first and the second laws of thermodynamics to study incylinder properties of the air in a typical reciprocating compressor at each. For planning purposes, reference 2 suggests the following values for the overall ef. Pdf engineering and chemical thermodynamics, 2nd edition. The basic operating principle behind compressed air energy storage caes is extremely simple. We measure the increase by the compressor pressure ratio cpr, which is the ratio of the air total pressure pt exiting the compressor to the air pressure entering the compressor. Thermodynamics of air compressors pt1 air equipment. An air compressor is a specific type of gas compressor compressors are similar to pumps.
The steam nozzle is a fixed orificemetering device. The change of kinetic energy and potential energy of fluid flowing into and out of turbines and compressors are very small that can usually be neglected. Determine the following assuming the air is ideal with constant specific heat. Effects of leakage flow model on the thermodynamic performance of a scroll were studied in detail. Application of basic thermodynamics to compressor cycle analysis.
However, isothermal compression presents realworld limitations. Thermodynamics of air compressors pt2 air equipment. Dcaes collects fuel credits equal to the negated heating fuel, leading to a higher overall efficiency compared to conventional caes. At position 2, the discharge valve opens and, as the piston continues to move, gas at discharge pressure and temperature is pushed out of the compression. Alexis giauque lmfaecl turbomachinery aero thermodynamics ii ecole centrale paris 21 48 transformation types rotor in a rotor, the e ective work is positive for a compressor and negative for a. Boyles and charles gas laws boyles law states that if the temperature is constant isotherm, then the product of the pressure and volume are constant. Boles 7th edition, mcgrawhill companies, isbn9780073529325, 2008 sheet 8. This article is an attempt to simplify these concepts. But to study comoressors, pumps and turbines defining a system as open helps a lot. Steam is expanded adiabatically in a turbine from 100 bar and 600oc to 0. Investigation of the thermodynamics of reciprocating compressors. It is ideal for student experiments, demonstrations and projects. Thanks for contributing an answer to engineering stack exchange. Thermodynamics also explains the relationships between such basic concepts as entropy, energy, heat capacity and temperature.
Development of high specific speed mixed flow compressors pdf. This law is for liquids and gases at rest and neglects the weight. A compressor acts as the heart of a refrigerantbased mechanical cooling system. The rigorous method was based on an equation of state like the soaveredlichkwong srk for calculating the required enthalpies and entropies. Air enters with speed of 50ms in a surface of 0,009 m2 and leaves with speed 120 ms from a surface of 0,0005 m2. Compressed air energy storage, entropy and efficiency saurorja. In the axial compressor, cascades of small airfoils are mounted on a shaft that turns at a high rate of speed. Thermocompressors use highpressure steam or gas as a motive fluid. Erb,september 2001 ii ii experiment or topic pages preface iii 1 calorimeter 1 2 capillary tube 10 3 dynamometer 18 4 expansion valve, automatic, pressure regulation 23 5 expansion valve, automatic, temperature regulation 28 6 gasoline engine, transparent, four stroke 33 7 heat exchanger, double pipe 39 8 heat pump 45 9 polytropic process air compressor 51. It is shown that the optimum rotor profile, compressor speed, oil flow rate and temperature may significantly differ when compressing different gases or vapors or if working at the oilfree or oilflooded mode of operation. Thermodynamic analysis of gas compressor 111 compressing the air in the cylinder, and the inlet the work of compression or steady flow work input to the gas is the negative of the shaft work wx, i.
The same principles are applied to the compression of other gasses. Chapter 9 92c how does the thermal efficiency of an ideal cycle, in general, compare to that of a carnot cycle operating between the same. Nov 28, 20 we define a system as per our convenience. Pradeep, department of aerospace engineering, iit bombay. A compressor is a mechanical device that increases the pressure of a gas by reducing its. In 1903 he had his first industrial unit operating in a steel works and by 1905 he. Isothermal process n1 results in minimum work smallest area. This relationship is a function of the ratio of the absolute pressuresfor example. Turbomachinery aerothermodynamics aerothermodynamics 0d2d alexis. Application of basic thermodynamics to compressor cycle. Compressors are cooled by water jackets or cooling fins.
Compression raising the gas pressure to dis charge pressure. The reciprocating compressor is probably the most versatile of all the types and is only out performed by rotary types when large volumes at low pressures are required. Thermodynamics ii compressors piston cylinder engine. Intake or induction piston moves from tdc to bdc intake valve opens and air induced into cylinder pressure p1 and temperature t1 remain constant. Whose value is independent of the size or extent i.
Aug 29, 2015 characteristics of compressed air pascals law states that the pressure of a gas or liquid exerts force equally in all directions against the walls of its container. Thermodynamics and heat transfer laboratory manual. In the november 2011 tip of the month totm we presented the compressor calculations of a case study. Heat transfer analysis of liquid piston compressor for. Thermodynamics allows an understanding of the overall physical features of a system in a microscopic dimension without focusing on the microscopic details of the behaviour of each component of the system. A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. But avoid asking for help, clarification, or responding to other answers. By 1899 he had a singlestage prototype on his test stand compressing 0. Reciprocating compressors are common machines that provide compressed air for machines and tools. Several rows, or stages, are usually used to produce a high cpr, with each stage producing a small pressure increase. Expressions for the volumetric effectiveness, the work per unit mass and the indicated efficiency are derived. May 05, 2015 to produce the increase in pressure, the compressor must perform work on the flow. In either design, the job of the compressor is to increase the pressure of the flow. However, the various compressor types and their attributes often cause.
Compression intake valve closes and piston moves towards tdc compression follows the polytropic process pvnc until. When these devices are adiabatic as is often the case, a comparison can be made between the performance of the actual, irreversible device and a. To understand the workings of compressed air, a basic introduction to physics can come a long way. But, as and when we approach this simple theory, it starts becoming more complex because of the thermodynamics involved. Compressor problem in thermodynamics physics forums. Any change in motive pressure causes a proportionate change in the quantity of motive fluid. Calculate the enthalpy at exit and the power output. Notes on availability and irreversibility you are already familiar with the basic second law concepts of a heat engine. Learn more about thermodynamics and how they are vital in understanding how air compressors work. Basic thermodynamics of reciprocating compression oaktrust. The first law of thermodynamics expresses the principle of conservation of energy.
This tutorial is mainly about reciprocating compressors. As is the case with the closed system, the availability will depend on the environment conditions. Turbine and compressor thermodynamics for engineer. Investigation of the thermodynamics of reciprocating. Applie d thermodynamics d201 self ass e ssment solutions tutorial 1 self assessment exercise no. Energy exists in various forms, such as thermal, physical, chemical, radiant light etc. Introduction the recent development in mathemati cal simulation models of recipro cating compressors has made clear the demand for data and correla. This presentation contains data about compressors and their types. Sep 02, 2015 homework statement air enters a compressor at 100 kpa and 290 k, where it is compressed adiabatically, where the flow rate is 0. The fluid initial state a before compression is known. Hw set 10 most of these problems deal with the isentropic e.
Sep 21, 2015 carnot heat engines, efficiency, refrigerators, pumps, entropy, thermodynamics second law, physics duration. Chap12 compressed air 1 gas compressor thermodynamics. Thermo 1 mep 261 thermodynamics an engineering approach yunus a. Axial compressor free download as powerpoint presentation.
The thermodynamics of caes has been extensively studied 10, but that of dcaes has not been. Compressor efficiency definitions vairex air systems. Open the hot and coldwater valves that supply the calorimeter. An air compressor is a specific type of gas compressor. Effects of leakage flow model on the thermodynamic. The free turbine drives the load and it is not connected directly to the compressor. Liquid piston, hydrogen compression, thermodynamic model, energy balance, heat analysis. The motive enters the steam chest and expands through the converging diverging nozzle. The compressor of dcaes is located near a heat load e. Thermodynamics ii compressors free download as powerpoint presentation.
Procedure the compressor used in this experiment is an integersolrand type 30 twostage air compressor. The thermodynamic model of the refrigerator compressor. Waste heat is released during the compression phase. Jun 06, 2016 when the compressor compresses the air, the air gets hot. Applied thermodynamics tutorial 2 gas compressors in order to complete this tutorial you should be familiar with gas laws and polytropic gas processes. Nov 22, 2010 thermodynamics, as with most concepts in science and physics, is most accurately described using mathematical equations. The result is high temperature 90c compressed air with high levels of oily mist in the air. Application gf basic thermodynamics to compressor cycle analysis richard g. Compressor is the device which is used to compress the fluid and increase its pressure. Compressed air energy storage, entropy and efficiency. The two leakage flow models, the isentropic and fanno flow model, were implanted into an analysis code to see their effects on the thermodynamic performance of a scroll compressor. The force is measured in terms of force per unit area pounds per square inchpsi. They can only be determined afterward by a compressor test, although compressor manufacturers can usually provide good estimates. But another way to view this situation would be that.
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