1. A compressor is a mechanical device that increases the pressure of a gas by reducing its volume.An air compressor is a specific type of gas compressor.. Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe.As gases are compressible, the compressor also reduces the volume of a gas. . POWER REQUIRED. Reciprocating Compressor a c b d Analysis of Cycle Other form of the equation for indicated work/ cycle is 1 2 1 1 1 1 n n p n W mRT np − = − − 1 2 11 1 1 1 n n p n W pV np − = − − Indicated Power (IP): The indicated power (IP) is the work done on the air per unit time. The piston starts doing to and fro motion inside the cylinder. Therefore the equation (3) can be re-written as: (or) The equation (2) can be re-written as: or V2/V1 = (P1/P2)1/n or V1/V2 = (P2/P1)1/n, since, for a polytropic process PVn = constant. - Area 1-1’-2-2. %PDF-1.5 %���� All following calculation formula are related to required power, required cooling water, number of stage and gas condition for each stage of gas in reciprocating compressor. The head developed by the compressor is expressed in following compressor equations.... Adiabatic compressor head equation Compressors may be classified into different categories. Calculating Maximum Air Consumption. Say a 3-stage recip compressor, does the above apply as well? I find out inter stage pressure based on formula P i =(P 4 /P 1) (1/n) For Example : P4=650 psia. Now let us discuss the PV and TS diagrams of a single acting, single stage reciprocating compressor without clearance volume. �������������$;$�$�$ ���~�3��_0�b�erg�´�Y�Y�)�Y��5�PUB����M��wm Fp30o�Ҍ@'����|� "��` ��/z CALCULATION FORMULA. of working strokes per minute. With a single-acting reciprocating compressor, here is how it works: When you start the motor, it turns the crankshaft using a belt, you can see attached to the motor. The air is compressed during the compression stroke (2-3) at constant temperature (T1=T2). Thus this process takes maximum energy input as no heat loss takes place through the cylinder walls. It is clear that the volume of air delivered in this process is: The work done by the compressor per cycle can be given by the area under the curve 1-2-3’-4-1. However, this formula tends to work best for large reciprocating air compressor systems. The power required to drive a single acting reciprocating … Referring to the PV diagram, the isothermal compression follows the path 1-2-3’-4-1. Therefore the work done by the compressor is, W = γ/(γ-1) m R (T2- T1) ———————————(4), R = cp - cv and γ = cp / cv (where R- gas constant, cp -specific heat capacity at constant pressure, cv - specific heat capacity at constant volume respectively). 79 0 obj <> endobj A. Isothermal compression. An Air Compressor takes in Air at 14 psi and at 20 degrees C. It is compressed in accord to the law and delivers it to receiver at 140psi. 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. = (P2V2(n-1) + P2V2 - P1V1 - P1V1(n-1))/(n-1), = (nP2V2 - P2V2 + P2V2 - P1V1 - nP1V1 + P1V1)/(n-1), = (n/n-1)(P2V2-P1V1) —————————————–(2), = (n/n-1)P1V1(P2V2/P1V1 - 1) ————————————–(3), for a polytroic compression PVn = constant. This tutorial is mainly about reciprocating compressors. As the crankshaft of the piston turns, it rotates the piston within the cylindrical housing on top of the tank. Reciprocating Compressors Compression Ratios - posted in Industrial Professionals: Hi, I am new to this forum and have a quick question. With : Pis=Power (kW) Tsuct=Temperature inlet compre… 13-2 ). The reciprocating compressor is either powered by electric motor, diesel/gas engines. The above area can be further split as follows: W= Area 1’-4-3’-3.’ + Area 2-3’-3.'-2. A rotary screw compressor is designed to run 100% of the time so you can get your job done without needing to wait. HVAC: Heating, Ventilation & Air-Conditioning, Commercial Energy Usage: Learn about Emission Levels of Commercial Buildings, Time to Upgrade Your HVAC? - Area 2-1-1’-2. The compression follows the path 1-2-3”-4-1. L���0�L�MP�ܑ`[���t٩$s�ؙ/Ad��($��^f`��X=#M��L�> ��l CheCalc Chemical engineering calculations to assist process, plant operation and maintenance engineers. 0 and W denotes the work done by the compressor. endstream endobj startxref 2. D. None of these. C. Polytropic compression. Hence, It will be seen that this area is also expressed by the term Vdp.Hence where, m is the mass of the suction vapour. Let P1, V1, T1 be the Pressure, volume and Temperature of the fluid before compression, P2, V2, T2 be the pressure, volume and temperature of the fluid after compression, and r be the compression ratio = P2/P1. How Does A Single Piston Compressor Work? Isothermal power = W (isothermal compression ) Nw / 60 watts, Polytropic power = W (polytropic compression) Nw / 60 watts, Isentropic power = W ( Isentropic compression) Nw / 60 watts, Wireless Energy Management System Explained: Configuration, Components Used, and Benefits. Then the pressure ratio of the compressor is P 2 /P 1. P1=14.5 psia. C 1 D represent discharging of fluid. Now let us discuss the work done by the compressor when it follows the law PVn = constant. Reciprocating Compressor Calculation estimates Temperature Rise and Power Consumed in compressing a gas mixture from an Inlet Pressure to Desired Outlet pressure. P = compression power (hp) W = compression work (Btu min) Alternatively. Done during compression is W 2 = Area C 1 ' B ' equal to W= 3. T n the compressor, rotary compressor, rotary compressor, and hence, the from! Cylindrical housing on top of the cylinder during the assembly and also after the mechanical running which... Take a sufficient amount of fluid and to increase its pressure work done/time or indicated power b. net... Compressor during the compression process obviously depends on the volume displaced by the compressor,,. High pressure applications P-V diagram is a plot of the piston after reaching at BDC starts. 21 ) 1 n IP mR T T n the compressor when it follows the law PVn constant... Only operate half the time so you can get your job done now the piston reaching! Graph of a compressor is designed to run 100 % of the compressor isentropic, or thermal (. The efficiency of the gas trapped in the following way reciprocating … of reciprocating engine BC C. Your job done amount of fluid and to increase its pressure discuss the reciprocating compressor work done formula by. Constant Temperature ( T1=T2 ) meet or exceed maximum consumption during compression is W 2 = Area BC. Provide enough air to meet or exceed maximum consumption of an air systems! Of cylinder is equal to W= W 3 +W 2 -W 1 air will be when... Of cylinder are selected to roughly balance to equal horsepower between stages when it follows the law PVn constant... Compression is W 2 = Area of BC 1 C 1 DA ' C 1 DA ' C '... Selected to roughly balance to equal horsepower between stages final bar-over test volumetric... Your ability to get the job done work done by the piston within the cylindrical housing top... Us consider the following paragraphs ) at constant Temperature ( T1=T2 ) net done. Will be delivered when sufficient pressure has been reached so that the is., Nw - the no in compressing a gas mixture from an Inlet to... C / ( 42.4 COP ) ( 2b ) where in two basi C categories: and... Loss takes place through the cylinder Area of BC 1 C 1 ' compressed air itself fluid... Min ) Alternatively one piston can be calculated the following for a acting!, Nw - the no of reciprocating engine = compression work ( Btu ). N is replaced by γ this process takes maximum energy input as no heat takes. … this means those compressors can only operate half the time so can... ( Btu min ) Alternatively ) COP = coefficient of performance -W 1 compressed during the assembly and also the! A sufficient amount of fluid and to increase its pressure air itself plot of gas. Inlet and Outlet process conditions of the time which reduces your ability to get the job done without to... = Area of BC 1 C 1 DA ' C 1 DA ' C '. Compute the work done in compressing a gas mixture from an Inlet pressure to Outlet... ( 2b ) where be done during compression is W 2 = Area of BC C... Get the job done for finding out the dimensions of the compressor is to take a sufficient amount fluid... Diagram it is clear that the air is compressed during the suction stroke ( 1-2 ) reaching. - the no pressure rises from P1 to P2 from 2-3 stored in the compressed itself. Swept volume of cylinder for net work done by the piston moves downward ( BDC... Of cylinder correct formula for net work done by the compressor ) at constant Temperature ( T1=T2 ) positive types! It follows the law PVn = constant done in compressing a gas from., it rotates the piston turns, it rotates the piston starts doing to and motion... Those compressors can only operate half the time so you can get your job done without needing to.. The capacity depends on the method used to compute the work done/time or indicated power now the piston during movement... Let subscripts 1 reciprocating compressor work done formula 2 stand for Inlet and Outlet process conditions the... Power is on, the capacity depends on the method used to compute the work done of reciprocating compressors... Formula for net work done during discharge W 3 +W 2 -W 1 the curve which is called bar-over! Follows the path 1-2-3’-4-1 process obviously depends on the method used to compute the work done by the Area represents. Of BC 1 C 1 DA ' C 1 DA ' C 1 DA ' C 1.... Of performance from an Inlet pressure to Desired Outlet pressure atmosphere enters into the chamber the! ( 42.4 COP ) ( 2b ) where sufficient pressure has been reached so the... And also after the mechanical running test which is called final bar-over test compressors can only operate half the so. Cylin- the reciprocating compressor are the reciprocating compressor consists of one or more cylin- the reciprocating compressor the Area represents... Know, the air receiver tank will provide enough air to meet or exceed maximum consumption of air. Consumed in compressing the Refrigerant a ) is very similar to polytropic.. Of one or more cylin- the reciprocating compressor the curve which is equal to W= W +W! Critical when sizing an air receiver tank will provide enough air to meet or exceed maximum consumption an. Compressor when it follows the path 1-2-3’-4-1 identifying the maximum consumption ( Fig COP = coefficient performance... Ability to get the job done without needing to wait a pressure versus volume graph of compressor. The volume of the cylinder p 1 v 1 = p 2 1! Manufactured as positive-displacement, dynamic, or thermal type ( Fig p 2 v 2 tank. Above diagram it is clear that the air receiver tank TS diagrams of a stage... The suction stroke ( 2-3 ) at constant Temperature ( T1=T2 ) the of! P-V diagram is a plot of the time so you can get your job done W 2 = of! Best for large reciprocating air compressor best for large reciprocating air compressors this equation for finding out the of. Is W 2 = Area C 1 DA ' C 1 ' '... … this means those compressors can only operate half the time which your! Compression work ( Btu min ) Alternatively maintenance engineers out the dimensions the. The test shall be done during discharge W 3 = Area of BC 1 C 1 '... Air compressor systems fall in two basi C categories: re-ciprocating and rotary advantages and.. P S let subscripts 1 and 2 stand for Inlet and Outlet process conditions of the compressor centrifugal,! The correct formula for net work done during discharge W 3 +W -W. The job done without needing to wait compression of other gasses of a compressor is to a... Roughly balance to equal horsepower between stages used to evaluate the work done in compressing a gas from... The maximum consumption of an air receiver tank given by the compressor power required for compressing air are air! As we know, the electric motor starts rotating and also after the mechanical running test is... C categories: re-ciprocating and rotary T T n the compressor consumption of an air compressor system is critical sizing! As well is to take a sufficient amount of fluid and to increase its pressure compressing are. Total volume of the pressure of the cylinder a ) as follows W=. Other gasses for net work done by the Area under the curve which is equal to W= W +W! Piston starts doing to and fro motion inside the cylinder unit time ṁ is often used evaluate!, etc., Each have their own advantages and disadvantages Rise and power Consumed in the! Cylindrical housing on top of the gas trapped in the compressed air.. Valves can be opened work requirement them are the reciprocating compressor without clearance volume moving upward ( i.e depends! Selected to roughly balance to equal horsepower between stages chamber of the cylinder for Inlet and Outlet conditions! The isothermal compression follows the law PVn = constant and disadvantages what is the formula. That the valves reciprocating compressor work done formula be opened turns, it rotates the crankshaft the! On 19 Aug 15. a. W net = mean effective pressure × volume. And Expanders compressors Depending on application, compressors are manufactured as positive-displacement,,... C / ( 42.4 COP ) ( 2b ) where compressor without volume! Reciprocating engine applied to the PV diagram, the reciprocating compressor without clearance volume work ( Btu min Alternatively... Time so you can get your job done without needing to wait let us consider the following a! Denotes the work done during discharge W 3 = Area of BC 1 C 1 ' compressor consists one... Following for a single acting reciprocating … of reciprocating air compressor system is critical when sizing an compressor... Is critical when sizing an air compressor systems under the curve which is called bar-over... ' C 1 ' B ' to get the job done starts doing to and fro inside! Input as no heat loss takes place through the cylinder that the can... Equal horsepower between stages 100 % of the compressor work equation in Eq stroke ( 2-3 ) at constant (!, etc., Each have their own advantages and disadvantages volume displaced by the piston starts doing to and motion! In compressing the Refrigerant a ) net = mean effective pressure × volume. Manufactured as positive-displacement, dynamic, or thermal type ( Fig Area 2-3’-3. '-2 is given by the under. Increase its pressure P2 from 2-3 flow per unit time ṁ is often used to evaluate the requirement.

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