Reciprocating compressor utilizing physical models combining with. Homework statement air enters a compressor at 100kpa and 20 oc in steady flow rate. 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. In previous chapters we assumed that the gas expansion is isentropic and therefore we used t 4,is as the outlet temperature of the gas. This is a transfer of heat energy out of the refrigerant.
Thermodynamics is a branch of physics that deals with heat and temperature, and their relation to energy, work, radiation, and properties of matter. Thermodynamic analysis of reciprocating compressors request pdf. Expressions for the volumetric effectiveness, the work per unit mass and the indicated efficiency are derived. Referring to our station numbering, the compressor entrance is station 2 and the compressor exit is station 3. This article is an attempt to simplify these concepts. The isentropic compressor work for an ideal gas is given by. Homework statement air enters a compressor at 100 kpa and 290 k, where it is compressed adiabatically, where the flow rate is 0. So, even though there is pressure rise in compressor, we are calculating work by using specific heat at constant pressure, which is. The model is based on five main and four secondary dimensionless physically meaningful parameters. Activity thermodynamics activitybased costing adiabatic process aerothermodynamics arrow of time blackhole thermodynamics and superstring theory blackbody boiling bolometer boyles law brayton cycle calorimetry carnot cycle charles law chemical energy chemical equilibrium chemical thermodynamics condensation conservation of energy daltons. The heat loss is 10% of the power of the compressor. It covers the basic principles in refrigeration and is not intended to provide specialized knowledge on the subject. Thermodynamics, as with most concepts in science and physics, is most accurately described using mathematical equations.
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. Data were obtained from the manufacturers manual, field reports and the field operators log sheets. These laws define thermodynamic properties, which are of great importance in understanding of thermodynamic principles. In an ideal vaporcompression refrigeration cycle, the refrigerant enters the compressor as a saturated vapor and is cooled to the saturated liquid state in the condenser. What is the reason for a reduction in entropy other that heatloss in these cases. An air compressor is a specific type of gas compressor. Work and efficiency as motivation for the development of the second law, we examine two types of processes that. Comparison between reciprocating and centrifugal compressors. Compressor is the device which is used to compress the fluid and increase its pressure.
Compression raising the gas pressure to dis charge pressure. Fundamentals of refrigeration thermodynamics by daniel micallef. In either design, the job of the compressor is to increase the pressure of the flow. Pdf theoretical analysis of the volumetric efficiency. However, simple explanations, although not perfectly accurate, are sufficient to convey the information needed to understand everyday experiences. There are many types of compressors with different working. Hw set 10 most of these problems deal with the isentropic e. Applicable and comparative research of compressor mass. Comparison between reciprocating and centrifugal compressors can done in aspects like mechanical efficiency, cost, noise, pressure ratio, multi stage possibility, volume handled, maintenance required or not, weight of compressor, operation speed, isentropic efficiency, higher compression efficiency condition and suitable operation conditions. Our mission is to provide a free, worldclass education to anyone, anywhere. Carnot heat engines, efficiency, refrigerators, pumps, entropy, thermodynamics second law, physics duration. Before moving to further detailed explanation lets have some overview of pump and compressor. Thermodynamics ii chapter 3 compressors mohsin mohd sies fakulti kejuruteraan mekanikal, universiti teknologi malaysia. Turbine and compressor thermodynamics for engineer.
A basic hvac system shows the application of the second law of thermodynamics. A vapor compression refrigeration cycle with a mechanical subcooling loop to increase system performance and reduce energy consumption is investigated by using both the first and second laws of thermodynamics. Two objects must be at the same temperature thermodynamically if the net heat transfer between them is zero when they are put in thermal contact and have reached a thermal equilibrium. Thermodynamics 157 internal energy of the system in state a be called u a. Back since april 2000 at the laboratory of thermodynamics, university. The laws of thermodynamics are deceptively simple to state, but they are farreaching in their consequences. Determine the following assuming the air is ideal with constant specific heat. Thermodynamic and aerodynamic meanline analysis of wet. Application of basic thermodynamics to compressor cycle. The actual power input into the compressor is larger than the indicated power, to overcome friction and other losses. How to size a refrigeration compressor based on an. Effect of intercooling on brayton cycle mechanical. This vapour compression system mainly consists of a refrigerator compressor, a liquid compressor, a liquid receiver, a refrigerant control valve also called as an expansion valve and evaporator. 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.
Recent the journal of chemical thermodynamics articles. Thermodynamics, environmental and economic assessment of. Influence of compressor geometry on the performance 8. We do some mechanical work, say 1 kj, by rotating a set of small paddles and. Fundamental laws of thermodynamics classical thermodynamics is based upon four empirical principles called zeroth, first, second and third laws of thermodynamics. Evaluate the performance of a typical twostage air compressor. Thermodynamics of a vaporcompression refrigeration cycle. Applied thermodynamics tutorial 2 gas compressors in order to complete this tutorial you should be familiar with gas laws and polytropic. Corrosionpedia explains compressor the laws of thermodynamics dictate how compressors are able to compress gases. Read thermodynamics law, browse chemistry articles, search huge archives on physical chemistry.
Thermodynamics is the study of relationship between energy and entropy, which deals with heat and work. The turbojet engine consists of a diffuser at the entrance which slows down the entrance air and thereby compresses it, called the ramming effect. The behavior of these quantities is governed by the four laws of thermodynamics which convey a quantitative description using measurable macroscopic physical quantities, but may be explained in terms of microscopic constituents by statistical. Getting started all of thermodynamics can be expressed. The main differences between pump and compressor are the pump transfers liquid from one place to another place whereas the compressor is used for storage of squeezed gas and then it supplied at the required place. Compressor thermodynamics under varying capacity loads are difficult to predict due to the interaction between the valvesealing element.
Pradeep, department of aerospace engineering, iit bombay. Thermodynamics thermodynamics is the study of the effects of work, heat, and energy on a system thermodynamics is only concerned with macroscopic largescale changes and observations. The compressor adds energy to the refrigerant, and it becomes hot, just the way a hand operated tire pump does. Recent the journal of chemical thermodynamics articles recently published articles from the journal of chemical thermodynamics. Simulation and prediction of thermodynamic performance of. Effect of heat losses on the thermodynamics efficiency of a compression process.
Simplified modelling of an opentype reciprocating compressor. Performance assessment of a twostage reciprocating air. A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. What is the reason for a reduction in entropy in a compressor. The most widely used refrigeration cycle is the vapor compression refrigeration cycle. Students who further their studies on refrigeration shall still find this book as. Proceedings of the asme 1997 international gas turbine and aeroengine congress and exhibition. How to size a refrigeration compressor based on an evaporator size. Thermodynamics the first law of thermodynamics britannica. The aim of the book is to provide first degree engineering students with the foundations on refrigeration engineering. Article in international journal of thermal sciences 401. Articles by topic accessscience from mcgrawhill education. Thermodynamic analysis of reciprocating compressors. Thermodynamics thermodynamics the first law of thermodynamics.
Thermodynamics of a hermetic reciprocating refrigeration. Cooling capacity 2 kw size 66 x 53 x 43 what i need to know is how to choose a compressor just to gain this full. Pdf effect of heat losses on the thermodynamics efficiency of a. Measurement of the speed of sound in ndecane at temperatures from 298. Application of basic thermodynamics to compressor cycle analysis. Open system energy balance conservation of energy statement for control volume mass entering the system increases energy content while mass leaving the system decreases energy content use appropriate sign convention for heat and work interactions. The first law asserts that if heat is recognized as a form of energy, then the total energy of a system plus its surroundings is conserved. Theoretical analysis of the volumetric efficiency reduction in reciprocating compressors due to incylinder thermodynamics article pdf available january 2010 with 716 reads how we measure reads. A vaporcompression refrigeration cycle with a mechanical subcooling loop to increase system performance and reduce energy consumption is investigated by using both the first and second laws of thermodynamics. Application gf basic thermodynamics to compressor cycle analysis richard g.
Since the compressed refrigerant is hotter than the air blowing across the condenser, the heat will flow to the cooler air. The most widely used refrigeration cycle is the vaporcompression refrigeration cycle. Procedure the compressor used in this experiment is an integersolrand type 30 twostage air compressor. In an ideal vapor compression refrigeration cycle, the refrigerant enters the compressor as a saturated vapor and is cooled to the saturated liquid state in the condenser. Construction and principle of operation of centrifugal compressor 2. As gases are compressible, the compressor also reduces the volume of a gas. Thermodynamics of a hermetic reciprocating refrigeration compressor with mcctpiston and valve system m. Thermodynamics, environmental and economic assessment of crgt for exhaust heat recovery in remote compressor station applications. During the expansion work will be done by the fluid to drive, for example, electric generation. These assumptions are only applicable with ideal cycles. It is a set of theories that correlate macroscopic properties that we can measure such as temperature, volume, and pressure to energy and its capability to deliver work. A global model for the thermodynamic analysis of reciprocating compressors is presented. W e can change the state of the system in two different ways. Article pdf available in international journal of applied engineering.
Theoretical analysis of the volumetric efficiency reduction in reciprocating compressors due to incylinder thermodynamics. A brief look into the laws of thermodynamics and how they govern the work done by machines. Thermodynamic analysis of reciprocating compressors sciencedirect. The properties of gases more or less follow the ideal gas law, which relates pressure p, volume v, the amount of gas in moles n and temperature t with a factor r called the universal gas constant.
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