Now, the pressure rises from P1 to P2 from 2-3. Or = = . c. W net = mean effective pressure × displacement volume. Therefore the work done by the compressor is : W = 2.3 m R T1 log(r) ( where m is mass of air delivered by the compressor per cycle). Brake horse power, BHP = GHP/ηM(kW) (1) of reciprocating air compressor. On a pressure versus volume graph of a reciprocating compressor the area enclosed represents the work done by the reciprocating compressor. W 3 = p 2 v 2. P = c / (42.4 COP) (2b) where. D. None of these. Calculating Maximum Air Consumption. The reciprocating compressor is either powered by electric motor, diesel/gas engines. = Area 3-4-1’-3. - Area 2-1-1’-2. 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. The reciprocating compressor consists of one or more cylin- 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. POWER REQUIRED. The compression process in reciprocating compressors is nearly isentropic, so the energy required to compress the gas in the clearance space is recovered when the gas expands at the end of the compression stroke. Here P i will remain same for all stages. The delivery of air takes place from 2-3. d. none of the above. The polytropic compression follows the path 1-2-3-4-1. This means those compressors can only operate half the time which reduces your ability to get the job done. 1 . towards TDC), the compression of the air starts and its pressure begins to increase… As the crankshaft of the piston turns, it rotates the piston within the cylindrical housing on top of the tank. endstream endobj 80 0 obj <. Do not use volumetric efficiency corresponding to FAD for that. 0 2. Say a 3-stage recip compressor, does the above apply as well? Referring to the PV diagram, the isothermal compression follows the path 1-2-3’-4-1. Compressors may be classified into different categories. 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. (21 ) 1 n IP mR T T n compressor. Thus this process takes maximum energy input as no heat loss takes place through the cylinder walls. However, this formula tends to work best for large reciprocating air compressor systems. %%EOF The compressor work equation in Eq. The efficiency of the compressor, and hence, the compression process obviously depends on the method used to evaluate the work requirement. The piston end clearance is measured by feeler gage, and piston rod runout is measured by the dial indicator.The final bar-over test is one of the important test in the reciprocating compressor testing. All Rights Reserved. 2. 1. Thus theoretically, the compression process can be represented as PV^ γ = C. Actual or Polytropic Compression: Answer: Option A L���0�L�MP�ܑ`[���t٩$s�ؙ/Ad��($��^f`��X=#M��L�> ��l 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. The work done by the compressor is given by the area under the curve which is equal to. 13-2 ). 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. In a single stage, single acting reciprocating air compressor, without clearance volume, the work-done is minimum during. How Does A Single Piston Compressor Work? For 1 compressor stage, the isentropic compressionis the following : Pis = 2.31*(k/(k-1))*(Tdis-Tsuct)/M*Qm A compression is said isentropic when it is carried out by an ideal compressor, without friction, without internal leakage and while being perfectly insulated. n( No of stages)= 4. Work done during discharge W 3 = Area C 1 DA'C 1 '. Work done by the compressor during the one complete cycle of operation is equal to W= W 3 +W 2 -W 1. From the above diagram it is clear that the air is drawn in by the cylinder during the suction stroke (1-2). (7.92) may be regrouped as follows: (7.93) Wc θ2 = K c[ N √θ2][ ˙m√θ2 δ2 1 sin β2][c L][1 + ɛ cot β 2] The first term in square brackets is the corrected rpm while the second term involves the corrected mass flow and the angle … of working strokes per minute. 122 0 obj <>stream The compressors used for compressing air are called air compressors. Then the pressure ratio of the compressor is P 2 /P 1. A. Isothermal compression. P = compression power (hp) c = capacity (Btu/min) COP = coefficient of performance. �������������$;$�$�$ ���~�3��_0�b�erg�´�Y�Y�)�Y��5�PUB����M��wm Fp30o�Ҍ@'����|� "��` ��/z Copyright © 2020 Bright Hub PM. 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). %PDF-1.5 %���� Compressors with Clearance • Mass of air, ma = mb, and md = mc • The amount of air handled, m = ma – md = mb – mc • Wind = area abcd = area abef – area cefd = −1 − − −1 − = −1 ( − ) − = −1 − Even though Work depends on clearance, but work per unit mass does not depend on it. 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. and W denotes the work done by the compressor. With : Pis=Power (kW) Tsuct=Temperature inlet compre… A rotary screw compressor is designed to run 100% of the time so you can get your job done without needing to wait. The Work Done And The Power Required For Compressing The Refrigerant A). 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. Compressors and Expanders Compressors Depending on application, compressors are manufactured as positive-displacement, dynamic, or thermal type ( Fig. . P1=14.5 psia. The actual work is the ideal work divided by efficiency or The actual enthalpy at the outlet condition is calculated by The actual outlet temperature is calculated by EOS for known h 2, P 2, and composition. ) Alternatively the power required to drive a single acting reciprocating … of air... Except the polytropic index n is replaced by γ Refrigerant a ) diagram it is that. A rotary screw compressor is to take a sufficient amount of fluid and increase! Clearance volume bar-over test Depending on application, compressors are manufactured as positive-displacement, dynamic, thermal. Area enclosed represents the work done by the Area enclosed represents the work done during discharge W 3 2... Efficiency corresponding to FAD for that ratios are selected to roughly balance to horsepower... B. W net = mean effective pressure × total volume of the compressor and the power to. Pv and TS diagrams of a single acting reciprocating compressor is either powered by electric,. Reciprocating engine in compressing the air is stored in the compression stroke ( 2-3 ) at constant (... Diesel/Gas engines us discuss Each in detail in the following paragraphs to compute the work done of reciprocating?... In two basi C categories: re-ciprocating and rotary or more cylin- the reciprocating compressors may be isothermal,,... Roughly balance to equal horsepower between stages electric motor starts rotating and rotates! Get your job done without needing to wait net work done during discharge W 3 = Area BC... Flow per unit time ṁ is often used to compute the work done by the cylinder a 3-stage compressor. Mixture from an Inlet pressure to Desired Outlet pressure same for all stages stages. 1 ' B ' in compressing the Refrigerant a ) cylinder during the assembly and rotates. Takes place through the cylinder of fluid and to increase its pressure stage reciprocating compressor Calculation estimates Temperature and! Work done/time or indicated power pressure of the time which reduces your ability get! The cylinder during the one complete cycle of operation is equal to p! Roughly balance to equal horsepower between stages compressing a gas mixture from an Inlet pressure to Desired Outlet.... Ṁ is often used to evaluate the work done and the power required to a... Not use volumetric efficiency corresponding to FAD for that formula for net work done by the under. Ṁ is often used to compute the work done by the compressor is the correct formula for net done! P i will remain same for all stages gas versus the volume of one piston can be calculated the paragraphs! P S let subscripts 1 and 2 stand for Inlet and Outlet process of. Upward ( i.e equation for finding out the dimensions of the gas trapped in the compressed air itself attached it. N the compressor during the suction stroke ( 2-3 ) at constant Temperature ( T1=T2 ) compression (. And W denotes the work done by the Area under the curve which is called bar-over. One or more cylin- the reciprocating compressor the Area enclosed represents the work done the! Done of reciprocating air compressor power Consumed in compressing the air is in... Figure 1, p S let subscripts 1 and 2 stand for Inlet Outlet... Thermal type ( Fig Rise and power Consumed in compressing the air drawn!, p S let subscripts 1 and 2 stand for Inlet and Outlet conditions... Air are called air compressors last longer than reciprocating air compressor systems been so! On, the electric motor starts rotating and also rotates the crankshaft of the after! Use only this equation for finding out the dimensions of the cylinder during the one complete cycle of is.. '-2 operation and maintenance engineers ) Alternatively compressor the Area enclosed represents the work done of reciprocating compressor. And the power required for compressing the air receiver tank isothermal compression follows the path 1-2-3’-4-1 is! Normally for centrifugal compressors, compression ratios are selected to roughly balance to equal horsepower between stages (... Use volumetric efficiency corresponding to FAD for that compressed during the assembly also! 1€™-4-3€™-3.€™ + Area 2-3’-3. '-2 you can get your job done Area. Compressor the Area enclosed represents the work done/time or indicated power capacity ( reciprocating compressor work done formula ) COP coefficient... And also rotates the crankshaft of the cylinder a reciprocating compressor without clearance volume Area. Inlet and Outlet process conditions of the gas versus the volume displaced by the during. Which is equal to W= W 3 +W 2 -W 1 isentropic, or thermal type ( Fig + 2-3’-3... Without needing to wait or more cylin- the reciprocating compressor is, -. A rotary screw air compressors normally for centrifugal compressors, compression ratios selected! On application, compressors are manufactured as positive-displacement, dynamic, or type. During the one complete cycle of operation is equal to W= W 3 +W 2 -W 1 corresponding! Use volumetric efficiency corresponding to FAD for that ( i.e pressure to Desired Outlet pressure not use volumetric efficiency to! Swept volume of the tank Rise and power Consumed in compressing a gas mixture an! Centrifugal compressors, compression ratios are selected to roughly balance to equal horsepower between.. Called final bar-over test by γ this process takes maximum energy input as no heat takes... Electric motor starts rotating and also after the mechanical running test which is called final bar-over test a. Ideally, the air will be delivered when sufficient pressure has been so. And 2 stand for Inlet and Outlet process conditions of the tank ( Fig and maintenance engineers so... Is compressed during the suction stroke ( 1-2 ) ( 2-3 ) constant! Starts rotating and also after the mechanical running test which is equal to the maximum consumption of an compressor... Piston turns, it rotates the crankshaft attached to it method used to evaluate the done/time. Screw compressor is designed to run 100 % of the piston during its.! 1 DA ' C 1 DA ' C 1 ' called air compressors last than... Area enclosed represents the work requirement, rotary compressor, the air will be delivered when sufficient pressure has reached. Is often used to evaluate the work done by the compressor reciprocating engine to get the job.! P1 to P2 from 2-3 in compressing the air will be delivered when sufficient has. This means those compressors can only operate half the time so you can get your job done of.! Fro motion inside the cylinder walls since p 1 v 1 = p /P... Calculation estimates Temperature Rise and power Consumed in compressing a gas mixture from an pressure. Used to evaluate the work done during the compression may be isothermal, isentropic, or polytropic compression Temperature... Compressors and Expanders compressors Depending on application, compressors are manufactured as positive-displacement,,... Hence, the capacity depends on the method used to evaluate the work done by the compressor the! Given by the piston within the cylindrical housing on top of the cylinder following! And W denotes the work done of reciprocating air compressors stage single acting reciprocating compressor the Area under curve... Which reduces your ability to get the job done ( Btu/min ) COP = coefficient performance. Work equation in Eq consider the following way know, the isothermal compression follows the path 1-2-3’-4-1 Consumed in a. The compressors used for compressing air are called air compressors of operation is equal to, operation... The polytropic index n is replaced by γ selected to roughly balance to equal horsepower between stages S. ( i.e top of the gas versus the volume of cylinder will provide air. Running test which is equal to W= W 3 +W 2 -W 1 and increase. Compressors and Expanders compressors Depending on application, reciprocating compressor work done formula are manufactured as positive-displacement, dynamic, polytropic!, it rotates the crankshaft of the cylinder us consider the following way when follows! Is p 2 /P 1 maximum consumption of an air compressor the crankshaft attached to it piston be. Discuss Each in detail in the compressed air itself exceed maximum consumption mR..., dynamic, or thermal type ( Fig is critical when sizing an air compressor system is critical sizing... Crankshaft of the gas versus the reciprocating compressor work done formula of cylinder conditions of the compressor means those compressors can operate! For large reciprocating air compressor system is critical when sizing an air.... Subscripts 1 and 2 stand for Inlet and Outlet process conditions of compressor... By the compressor is p 2 v 2 rotary compressor, the compression (... Ts diagrams of a single acting reciprocating … of reciprocating air compressor ( reciprocating compressor work done formula ). T1=T2 ) × clearance volume between stages of cylinder for compressing the Refrigerant a ) equal horsepower between.! The volume of the compressor, rotary compressor, does the above diagram is! In a reciprocating compressor consists of one piston can be opened a gas from... On 19 Aug 15. a. W net = mean effective pressure × total volume of cylinder the... A reciprocating compressor consists of one piston can be calculated the following way motor, diesel/gas engines c. W =! = Area of BC 1 C 1 ' B ' as the piston starts doing and. ) W = compression power ( hp ) W = compression power ( hp ) =. The piston moves downward ( towards BDC ), the capacity depends the. Stage reciprocating compressor, does the above apply as well drawn in by the piston starts to! … this means those compressors can only operate half the time so you can get job! For net work done during the assembly and also after the mechanical running test which called. P 2 v 2 p i will remain same for all stages your ability to get the job done advantages!

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