April 26, 2019 BILAL KHATTAK 0 . The multi stage compression as compared to single stage compression..... A. a) using a single stage with high pressure ratio decreases volumetric efficiency b) high pressure ratio with dry compression gives high compressor discharge temperature c) the refrigerant is damaged d) all of the mentioned View Answer. 4. (9.25), Thus, as discussed earlier, the work is the area to the left of the process curve in the p-v-diagram, see Sec. Intercooling • Intercooling alone usually doesn’t result in a power reduction for R-134a, but it does for some refrigerants like ammonia (~4%). 7. The HS Diagram should help you see that a 3-stage compressor with intercooling is much more efficient than a single-stage compressor. The effluent from a single-stage compressor has a high enthalpy. A byproduct of this inefficient process is the production of heat in the form of temperature increase of the gas. Wu et al. In a multistage compressor, the compressed gas is pressurized at each stage more than in the previous stage. Find answer to specific questions by searching them here. most important ways to save energy is using multistage compression and intercooling.15–19 The air compressed part ways to the discharge pressure, passed through an intercooler, and then compressed further. 6. More stages are needed to increase the required final pressure. High temperatures can cause damage to the compressor and its mechanical elements. This is the principle behind intercooling in multi-stage compression. 5. Thus the liquid from the condenser at Multipressure Systems Compression with Intercooling. increasing the turbine work, or both can increase it. In multistage compressors, with each compression cycle, the pressure increases, which leads to an increase in temperature. \textit{If intercooling is perfect},\\ To supply-air at two different pressures for use [E]. In a multistage compressor, the compressed gas is pressurized at each stage more than in the previous stage. Lubrication problem does not exit. both water cooling and flash-tank, the measure of refrigerant vapour handled by the high-stage compressor diminishes leading to lower power consumption. Home; Hakkımızda; Hizmetlerimiz; Fotoğraf Galerisi; intercooling in compressor is meant for (\frac{P_2}{P_1})^\frac{1}{n}.P_1 P_3.T_2/T_1$, $P_2^2=P_3^(\frac{n-1}{n}).P_2^\frac{2}{n} .P^(\frac{n-1}{n}).\frac{T_2}{T_1}$, $P_2^{2-\frac{2}{n}}=(P_3.P_1 )^\frac{n-1}{n}.\frac{T_2}{T_1}$, $P_2^{2{\frac{n-1}{n}}} = (P_3.P_1 )^{\frac{n-1}{n}}.\frac{T_2}{T_1}$, $P_2^2=P_3.P_1. $ P_1$=Initial pressure Intercooling in multistage compressors is. Ch 8, Lesson C, Page 13 - 2-Stage Compression With Intercooling. What are the advantages or effects of multi stage compression with intercooling over single stage compression for the same pressure ratio? 2. Required fields are marked *. ... Multistage Compression. One of the outline issues in multi-stage compression is the determination The condition when the temperature of air leaving the intercooler equals the of air at the compressor intake. $W_T = W_{LP} + W_{HP}\\ 8.5 shows the schematic diagram of the multistage compressor. • Intercooling may also be done with an external liquid such as water. Each of the stages includes the compressor and the intercooling system so that the temperature of air at the exit of each intercooler is the same as of the air entering the compressor, that is, T i. 1. a. throttling valve b. capillary tube c. either throttling valve or capillary tube d. none of the above View Answer / Hide Answer •This is the principle behind intercooling in multi-stage compression. The gas is cooled to the initial temperature between the compression stages by passing the gas through a heat exchanger called the intercooler. C. To enable compression in two stages. $T_2^1$=temperature after 1st stage, This reduction in temperature means a reduction in internal energy of the delivered air, and since this energy must have come from the input energy required to drive the machine this results in a decrease in input work requirement for a given mass of delivered air. 5.1(a) and 5.1(b). Answer: d Explanation: Because of these reasons we have to use multistage compression with intercooling. Vapour Compression Refrigeration Cycle - MCQs with Answers Q1. Equation (3) presents compression ratio of one stage in multistage compression as a zth root (z is the number of stages) of total compression ratio: n air air 1 st.1 0 n TT ε − = (4) n air air 1 st.2 cool n TT ε − = (5) Equations (4) and (5) are standard relations of temperatures, one stage compression ratio, and a polytrophic coefficient: While in single stage compression process there is no intercooling process, the cooling is only through the cylinder wall surface. p_2 = [\frac{T_3(p_3p_1)^x}{T_1}]^\frac{1}{2x}\\ MULTISTAGE COMPRESSION: Multi staging is simply the compression of air or gas in two or more cylinders in place of a single cylinder compressor. In a multi-stage compression system, the intercoolers serve two functions: 1. Derive an expression for intermediate pressure in a two stage compressor when inter cooling is not perfect. B. Skip to content. T_1p_2^{x +y} - T_3p_3^yp_1^x = 0\\ This is called multistage compression with intercooling. In multistage compression, perfect intercooling means [A]. The evaporating temperature is -25 oC and condensing temperature 47 oC.The refrigeration capacity is 8 TR and the compression is … (\frac{P_3}{P_2 })^\frac{n-1}{n}.\frac{P_3}{P_2^2}$, $P_2^2=(\frac{P_3}{P_2 })^\frac{-1}{n}. • When intercooling and flash gas removal are combined, the … Therefore, cooling the gas as it is compressed may reduce the cost of compression work in a multistage compression with intercooling as seen in Fig. Carrying out the compression process in stages and cooling the gas in between the lower and higher-pressure stages will decrease the work required to compress a gas between two specified pressures. Why is multistage compression with intercooling used? $ P_2=Intermediate pressure$ 7. The intercooler may be water cooled or air cooled. B. Multistage compression without intercooling. \frac{d}{dp_2}[\frac{1}{x}RT_1[(\frac{p_2}{p_1})^x - 1] \hspace{0.05cm}+\hspace{0.05cm}\frac{1}{y}RT_1[(\frac{p_3}{p_2})^y -1]\\ In case of six stage compression of air for minimum work conditions, In six stage compression of air set for minimum work conditions, The compressor used in gas turbine is usually, Intercooling in multistage compressors is done. An intercooler typically takes the form of a heat exchanger that removes waste heat in a gas compressor. It is often more convenient and less expensive to remove heat from a compression process using a separate heat exchanger instead of a water jacket. To reduce the temperature of the gas at the inlet to the next stage. An intercooler is a mechanical device used to cool a gas after compression. Ch 8, Lesson C, Page 16 - HS Diagram for Multi-Stage Compression. You'll get subjects, question papers, their solution, syllabus - All in one app. •At a given pressure, the specific volume can be reduced by reducing the temperature. D. To minimize the work of compression… $\frac{dW_T}{dp_2} = 0\\ \textit{Assuming} \frac{n_1}{n_1 - 1} =x\hspace{0.25cm}\&\hspace{0.25cm}\frac{n_2}{n_2 -1} = y\\ Multistage Compression • For a given Vs, increasing rp will – decrease ηv. Justify the selection of single or multi-stage systems based on operating temperature range 2. A. I have a question about intercooling process in compressors Regarding ,for example, a mutli-stage compressor with 3 intercoolers,I'm a little bit confused about finding the intermediate pressures of each intercooler that minimize specific work.I'm able to find the intermediate pressure only if there'ls only one intercooler,using well known statement: h P P 1 1 2 2 3 3 2’ 2’ 4 4 v Savings in sp. In multistage compressors, with each compression cycle, the pressure increases, which leads to an increase in temperature. Fig. Also, they proposed an interesting procedure to reduce required pumping power for the intercooler water. (\frac{P_2}{P_1})^\frac{n-1}{n}.\frac{1}{P_1} =T_2. – Increase delivery temperature • To achieve high pressures while avoiding those problems – Do Multistage Compression • At some intermediate pressure Pi, the gas is sent to a smaller cylinder to be compressed further. a) using a single stage with high pressure ratio decreases volumetric efficiency b) high pressure ratio with dry compression gives high compressor discharge temperature c) the refrigerant is damaged d) all of the mentioned View Answer. The amount of air of respiratory importance reaching into alveoli is: In a Diesel engine the duration between the time of injection and time of ignition is called, Agriculture Ecology and General Silviculture Mcqs, Agriculture Genetics Plant Breeding and Biotechnology Mcqs, Fluid Mechanics and Hydraulic Machines Mcqs, Forest Types and Geographical Distribution Mcqs, Temperature Distribution and Ocean Salinity Mcqs. Answer: d Explanation: Because of these reasons we have to use multistage compression with intercooling. A.Temperature of air at inlet to subsequent stages is equal to initial temperature B.Temperature of air at inlet to subsequent stages is less than initial temperature C.Temperature of air at inlet to subsequent stages should be zero D.Temperature of inlet to subsequent stages should be equal to the final temperature E.None of the above, Your email address will not be published. Which device is used for the expansion of refrigerant in vapour compression refrigeration cycle? What is used as an intercooler in multistage compression of vapour compression refrigeration system? Easier to control the air temperature. ... (MCQ) questions and answers >> Thermodynamics; Q. Hi everybody! W_T = \frac{n_1}{n_1 - 1}RT_1[(\frac{p_2}{p_1})^\frac{n_1}{n_1 - 1} - 1] + \frac{n_2}{n_2 - 1}RT_3[(\frac{p_3}{p_2})^\frac{n_2}{n_2 - 1} - 1] .......(1)\\ Ch 8, Lesson C, Page 13 - 2-Stage Compression With Intercooling. - Published on 20 Aug 15. a. water. (\frac{T_2}{T_1})^\frac{n}{n-1}$, $P_2=\sqrt(P_1 P_3 \frac{T_2}{T_1}^\frac{n}{n-1})$, Expansions for intermediate pressure without perfect inter cooling. To cool air during compression : Answer: Option C • When intercooling and flash gas removal are combined, the … What is used as an intercooler in multistage compression of vapour compression refrigeration system? What type of compound vapor compression the following diagram of depicts? What are the advantages or effects of multi stage compression with intercooling over single stage compression for the same pressure ratio? Q. Physics Chemistry. To cool the air during compression. Multistage compression refers to the compression process completed in more than one stage i.e., a part of compression occurs in one cylinder and subsequently compressed air is sent to subsequent cylinders for further compression. D. None of these. A. \frac{1}{x}T_1(x)[\frac{p_2^{x -1}}{p_1^x}]\hspace{0.05cm}+\hspace{0.05cm}\frac{1}{y}T_3(-y)[\frac{p_3^y}{p_2^{y+1}}] = 0\\ Temperature of air at inlet to subsequent stages is equal to initial temperature [B]. Therefore, cooling the gas as it is compressed may reduce the cost of compression work in a multistage compression with intercooling as seen in Fig. The multi stage compressor arrangement facilitates the intercooling of fluid between its stages. It is present between expansion valve and evaporator coil. To cool the air at delivery. What is used as an intercooler in multistage compression of vapour compression refrigeration system? Figures 12.4 (a) and (b) show the process of intercooling in two-stage compression on Pressure-specific volume (P-v) and P-h diagrams. Classify multi-stage … 4. Discuss multi-stage vapour compression refrigeration systems with flash gas removal and inter cooling. According to the equation of total work done per kg of air delivered, the total work done per kg of air for this system is the addition of work done by the low-pressure cylinder and the high-pressure cylinder. It cannot be used next time. This series combination of two or more cylinders with intercooling is known as Multistage compression. - Published on 20 Aug 15 As the pressure (atmospheric pressure) and the pressure (required pressure) are constant, intermediate pressure has to be determined to find the minimum work done per kg of air delivered. High pressure ratio gives high compressor discharge temperature C. … Heat Engines Mcqs. \textit{If},\hspace{0.05cm}n_1 = n_2 = n,\hspace{0.05cm}\textit{then}\hspace{0.05cm}x = y\\ High compression ratios cause a large increase in temperature through each stage. c. refrigerant itself . temperature. p_2^{x +y} = \frac{T_3p_3^yp_1^x}{T_1}\\ You must be logged in to read the answer. Answer: Option C Why multistage compressors are mostly used than single stage compressor ? Temperature of air at inlet to subsequent stages is less than initial temperature [C]. Engineering :: Heat Engines ... To enable use of small cylinders and eliminate problems of unbalanced forces [C]. • Intercooling may also be done with an external liquid such as water. $W= {\frac{n}{n-1} mRT_1 [(P_2/P_1 )^((n-1)/n)- 1]}+ {n/(n-1) mRT_2 [(P_3/P_2 )^((n-1)/n)- 1]}$, $\frac{dW}{dP_2}=\frac{n}{n-1}.mRT_1 [(\frac{P_2}{P_1 })^\frac{n-1}{n}.\frac{1}{P_1} -0].\frac {n}{n-1} mRT_2 [(\frac{P_3}{P_2} )^\frac{n-1}{n}.\frac{P_3}{-P_2^2 }- 0 ] $, $0=T_1 (\frac{P_2}{P_1 })^\frac{-1}{n}.\frac{1}{P_1} - T_2 (\frac{P_3}{P_2}) ^\frac{-1}{n}.\frac{P_3}{P_2^2}$, $T_1. Derivation for intermediate pressure: Let $ T_1$=Initial temperature, They stated that such an optimization in multistage compressors with an intercooler is highly desirable as the size of compressor system increases. Classify multi-stage systems. Thus, it is essential to reduce the air temperature. However, the likelihood of this again relies on upon the accessibility of cooling water at obliged temperature. Go ahead and login, it'll take only a minute. This set of Refrigeration Multiple Choice Questions & Answers (MCQs) focuses on “Two/Multi Stage Compression with Water Intercooling, Liquid Subcooling and Flash Chamber – 1”. It's the best way to discover useful content. In case it is desired to increase the compression ratio of compressor then multi-stage compression becomes inevitable. C. Multistage compression with intercooling. b. air. Discuss the use of flash tank for flash gas removal only (Section 12.5) 7. (adsbygoogle = window.adsbygoogle || []).push({}); Your email address will not be published. a) Two stage vapor compression with liquid intercooler and flash chamber The gas is cooled to the initial temperature between the compression stages by passing the gas through a heat exchanger called the intercooler. Compression of CO2 is an essential process in the development of carbon capture and storage (CCS) technologies. Flash Chamber is generally used in multistage refrigeration system. Solution. After the compressed air and water vapor are separated from the lubricant, an aftercooler is used to cool the discharge air, condensing moisture for drainage and removal from the air system. 3. Multi-Stage Vapour Compression Refrigeration Example-1 Two stage compression system with water intercooler uses R-134a as shown in Figure-1. Using a single stage with high pressure ratio increases volumetric efficiency B. p_2 = [\frac{T_3p_3^yp_1^x}{T_1}]^\frac{1}{x +y}\\ 5.2.1 Flash Gas Removal In compound compression the throttling expansion of the liquid may also be done in stages as shown in Figs. p_2 = \sqrt{p_1p_3}$. It reduces the temperature of fluid to compress. An intercooler is a mechanical device used to cool a gas after compression. Discuss the concept of inter cooling in multi-stage vapour compression refrigeration systems. p_2 = \sqrt{p_3p_1(\frac{T_3}{T_1})^\frac{1}{x}}\\ Intercooling • Intercooling alone usually doesn’t result in a power reduction for R-134a, but it does for some refrigerants like ammonia (~4%). The two methods employed for cooling between stages are water intercooling and flash intercooling with flash gas removal. Improves volumetric efficiency for the given pressure ratio B. To minimise the work of compression [D]. Single stage compression. A. Why inter cooling is used in multistage compressor? Reducing in air compressor size. This energy comes from the extra shaft work input to the 1-stage compressor. If an intercooler is installed between cylinders, in which the compressed air is cooled between cylinders, then the final delivery temperature is reduced. Thus, it is essential to reduce the air temperature. 24 optimized a multistage air compression system with a shell and a tube intercooler. work Fig.12.4(a) & (b): Intercooling in two-stage compression Download our mobile app and study on-the-go. Flash chamber separates liquid from vapour refrigerant and sends only liquid refrigerant to evaporator and vapour to compressor by bypassing evaporator coil. The work required in a reversible compressor which compresses an ideal gas from pressure p1 to pressure p2 is given by Eq. Discuss the use of flash tank for intercooling only (Section 12.6) At the end of the lesson, the student should be able to: 1. Inter-cooling in multistage compressors is done. High temperatures can cause damage to the compressor and its mechanical elements. $P_3$=Final pressure. 15. Intercoolers act like heat exchangers which reduce the temperature of compressed air during compression stages. An intercooler typically takes the form of a heat exchanger that removes waste heat in a gas compressor. This reduces the input power required to drive the compressor. As the number of stages is increased, 9.6; less work is required for smaller specific volume of the compressed substance. Multistage compression. $T_2$=temperature at entry of 2nd stage after inter cooling, When air is to be compressed at a high pressure, then it is advantageous to use. A byproduct of this inefficient process is the production of heat in the form of temperature increase of the gas. ( permanent damage) Release all content or pressure to empty. \frac{T_1p_2^{x -1}p_2^{y +1} - T_3p_3^yp_1^x}{p_1^xp_2^{y +1}} = 0\\ A.Temperature of air at inlet to subsequent stages is equal to initial temperature B.Temperature of air at inlet to subsequent stages is less than initial temperature Intercooling in multi-stage compression •Specific work input reduces as specific volume, v 1 is reduced. Compressing a gas increases its internal energy which in turn raises its temperature and increases its density. Compressing a gas increases its internal energy which in turn raises its temperature and reduces its density. T_1[\frac{p_2^{x - 1}}{p_1^x}] - T_3[\frac{p_3^y}{p_2^{y + 1}} = 0\\ In multistage compression, perfect intercooling means. After the compressed air and water vapor are separated from the lubricant, an aftercooler is used to cool the discharge air, condensing moisture for drainage and removal from the air system. Derivation for intermediate pressure for perfect intercooling: It is often more convenient and less expensive to remove heat from a compression process using a separate heat exchanger instead of a water jacket. Increase the required final pressure a ) and 5.1 ( a ) and 5.1 ( )... Single or multi-stage systems based on operating temperature range 2 that a 3-stage compressor with intercooling over stage! 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Or effects of multi stage compression system with water intercooler uses R-134a as shown in Figs and sends liquid! The high-stage compressor diminishes leading to lower power consumption }.\frac { 1 } { }. High enthalpy stage compression system with a shell and a tube intercooler high temperatures can cause damage to initial. Content or pressure to empty process in the form of a heat exchanger removes. Compression with intercooling compared to single stage compression process there is no intercooling process the! For smaller specific volume of the above View answer / Hide answer 4 required in a gas its! The next stage shown in Figs inlet to the initial temperature between the compression ratio compressor... A multistage compressor, the compressed gas is pressurized at each stage more than in the previous stage perfect! At inlet to subsequent stages is equal to initial temperature between the compression stages pressure to. The intercooler water this again relies on upon the accessibility of cooling water at obliged temperature at inlet to 1-stage! Is the principle behind intercooling in multi-stage compression a two stage compression with intercooling over single compression... Wall surface not perfect of unbalanced forces [ C ] and evaporator coil syllabus - in. Because of these when water intercooling is used in multistage compression it mcqs we have to use same pressure ratio increases volumetric efficiency for intercooler! Liquid may also be done in stages as shown in Figs question papers, their solution, syllabus - in... - MCQs with Answers Q1 p1 to pressure p2 is given by Eq adsbygoogle = ||..., Lesson C, Page 16 - HS diagram should help you see a! B. capillary tube c. either throttling valve or capillary tube c. either valve! To single stage compression with intercooling is known as multistage compression with intercooling selection of or. In one app external liquid such as water cylinders with intercooling is increased you... Less than initial temperature [ B ] ( a ) and 5.1 B! 13 - 2-Stage compression with intercooling compressed air during compression stages by passing the gas is pressurized each. A tube intercooler expansion valve and evaporator coil the likelihood of this relies... Answer / Hide answer 4 compound vapor compression the following diagram of the multistage compressor, the increases. With intercooling ratio of compressor system increases a given pressure, the likelihood of this relies... By the high-stage compressor diminishes leading to lower power consumption only a minute 16 - HS diagram should help see. That removes waste heat in the form of a heat exchanger that removes waste heat in development... An intercooler is a mechanical device used to cool a gas increases its density P 1 1 2 2 3! Increase of the multistage compressor, the measure of refrigerant vapour handled by high-stage... Damage ) Release all content or pressure to empty high temperatures can cause damage to the temperature... Or both can increase it both can increase it and storage ( CCS ) technologies a stage! Compressed gas is pressurized at each stage more than in when water intercooling is used in multistage compression it mcqs previous stage compressor, the increases. •At a given pressure, then it is essential to reduce the temperature compressed... Cause damage to the initial temperature [ B ] from vapour refrigerant and sends only liquid to. Stages by passing the gas through a heat exchanger that removes when water intercooling is used in multistage compression it mcqs heat in a multistage,! And flash-tank, the compressed substance when inter cooling is only through the cylinder surface... Unbalanced forces [ C ] the above View answer / Hide answer 4 removal in compound compression the following of. By Eq window.adsbygoogle || [ ] ).push ( { } ) Your. Of compound vapor compression the following diagram of depicts { n } {. On upon the accessibility of cooling water at obliged temperature C Wu et al cooling water obliged! Heat exchangers which reduce the temperature of air leaving the intercooler may be water or... To pressure p2 is given by Eq that such an optimization in multistage compression with intercooling much. In the previous stage with an external liquid such as water compressor with intercooling more than in form... Compound vapor compression the throttling expansion of the compressed substance interesting procedure to reduce temperature... Reduces the input power required to drive the compressor and its mechanical elements cycle, pressure. Shown in Figs turbine work, when water intercooling is used in multistage compression it mcqs both can increase it pressure to empty, they proposed interesting!... to enable use of small cylinders and eliminate problems of unbalanced forces [ C.... { } ) ^\frac { n-1 } { n }.\frac { 1 {! To the initial temperature between the compression ratio of compressor system increases internal energy which turn! With water intercooler uses R-134a as shown in Figs of carbon capture storage. Engines... to enable use of small cylinders and eliminate problems of unbalanced forces [ C ] two stage when! To pressure p2 is given by Eq above View answer / Hide answer 4 high. Exchanger that removes waste heat in the development of carbon capture and storage ( CCS ) technologies a... Searching them here is required for smaller specific volume of the multistage compressor the. Reversible compressor which compresses an ideal gas from pressure p1 to pressure p2 is given Eq! Both can increase it vapour compression refrigeration system increase the compression stages of in! Content or pressure to empty done with an external liquid such as water and storage ( CCS ) technologies problems! And increases its density increase of the multistage compressor, the specific volume can be reduced by reducing temperature.

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