Superheated vapour. Air trapped in a refrigeration system using a water-cooled condenser is usually indicated by a] unusually high head pressure when compared to the existing temperature of the liquid refrigerant b] higher than normal liquid level in the receiver c. either throttling valve or capillary tube, ANSWER: c. either throttling valve or capillary tube, a. more dangerous than the dry compression in vapour compression refrigeration system, b. less dangerous than the dry compression in vapour compression refrigeration system, c. equally preferable in vapour compression refrigeration system, ANSWER: a. more dangerous than the dry compression in vapour compression refrigeration system. Single- and multistage arrangement small compressors, particularly the trunk type, are … Centrifugal chiller compressor. Answer: d (d) None In a vapour compression system, the condition of refrigerant before entering the compressor is, 3. (d) None The L compressors were remark-able in that they required only one stage of compres-sion to do what two or three stages had done in all previous centrifugal air-conditioning machines. d) all of the mentioned Whereas icentropic expansion is also called Adiabatic expansion. You will only be able to open a service valve with the appropriately sized service valve wrench. a) freon Conservation of mass and energy rate applied to a control volume enclosing the compressor then give: Qw = m * (h2– h1) Where • W/ m is the work done per unit mass of … Q1. 151. The compressor is the heart of the cooling function of heating, ventilation and air conditioning (HVAC) systems. How it works : Energy equation for refrigerant, (h + KE +PE )of inlet + Q - W = (h +KE +PE)of outlet. Q: Why are we putting in Inverted Traps on the liquid and discharge lines? The condensing coil is often placed inside the walk-in refrigerator. This will likely be 90 to 100 degree SCT. When do we need three compressors in a refrigeration unit? Q17. Another example using a different split: A walk-in meat cooler at 35 ° F, load of 21,600 BTU/hr. Dry saturated liquid. a) capillary tubes Correct Answer Home MCQ Refrigeration Multiple Choice Questions with Answers on Refrigeration and Air-Conditioning ... Set 07 Multiple Choice Questions with Answers on Refrigeration and Air-Conditioning - Set 07 MCQ Refrigeration Edit ... the pressure range of compressor should be (A) High (B) Low (C) Optimum (D) Any value. Low boiling point. Which device is used for the expansion of refrigerant in vapour compression refrigeration cycle? b) 1 – C – C(p2/p1)^(1/n) (Ans:a), Rotary compressor is used in refrigeration when pressure difference between condenser and evaporator pressures is d) all of the mentioned A refrigerant should have (a) Tow specific heat of liquid (b) high boiling point (c) high latent heat of vaporisation (d) higher critical temperature (e) low specific volume of vapour. D. F – 21. (b) <1.5 bars You then include your inefficiency and design for 20% or more above what you need as a safety factor. pressure of a unit mass of refrigerant remains the same, ie. 151. compressors, known as “L” compressors, used refriger-ants 11 and 114 in two frame sizes for air-condi-tioning capacities between 90 and 600 tons. of compressor required will be (A) Same (B) More (C) Less (D) More/less depending on rating. View Answer: Answer: Option … The sub-cooling in a refrigeration cycle, 6. The combination of units will only get you there faster and maybe a little past. 3. In all the household refrigerators, deep freezers, window air conditioners, split air conditioners, most of the packaged air conditioners, the hermetically sealed reciprocating compressor is used. b) genetron This is the Multiple Choice Questions Part 2 of the Series in Refrigeration Engineering as one of the Mechanical Engineering topic. View Answer. Typical refrigerator duty cycle for a ColdMachine or SuperColdMachine with 3" insulation runs the compressor 40% of the time. What is the use of multistage compression in vapour compression refrigeration system? Question: Question 35 When Do We Need Two Compressors In A Refrigeration Unit When Temperature To Be Achieved Is Around 5 0 C When Temperature To Be Achieved Is Around-5 0 C None When Temperature To Be Achieved Is Around -50°c Question 36 COMMON DATA FOR Q36-37 Rihi A Canacity Of 75 TR And Uses As Refrigerant R134a That Evap Which device is used for the expansion of refrigerant in vapour compression refrigeration cycle? A. F – 12. Explanation: These are a group of halogenated hydrocarbons. Evaporator: This is the part of the refrigeration system that is doing the actual cooling. Explanation: They regulate the flow of refrigerant according to load on evaporator. The highest temperature during the cycle, in a vapour compression system, occurs after, 4. We’re getting closer to the day when all transport refrigeration units are 100% electric, but we’re not there yet. How does a compressor work? As another alternative, the solid sorption refrigeration without compressors has also drawn widespread attention in recent decades (Ge et al., 2018), mainly due to that solid sorption refrigeration systems are driven by low-grade heat such as solar thermal energy, engine waste heat or geothermal energy (Wang and Oliveira, 2006). C. F – 22. B. What they actually do is remove heat out of a. The unit I have gets to 28, which is -14 psi. b) throttle valves Basically, if someone had a 20 ton (non-packaged) unit with multiple air handling units (AHU’s), regardless of the piping, it would be assumed that the unit had somewhere between 60-80 pounds of refrigerant. d) none of the mentioned (B) using water colder than the main circulating water It has smaller size for the given capacity of refrigeration. Explanation: Here p1 is the evaporator pressure and p2 is the condenser pressure. Vapor-compression uses a circulating liquid refrigerant as the medium which absorbs and removes heat from the space to be cooled and subsequently rejects that heat elsewhere. (a) Temperature alone Oil is used in a refrigeration system to lubricate the compressor and keep the refrigeration unit running smoothly. High-speed compressors. One of the first things every HVAC/R student learns is that air conditioning units don’t create cool air. which will improve your skill. Latest Hvac questions and answers for interview Refrigeration and air conditioning 2 marks questions and answers free Basic air conditioning test questions free for your. Occasionally, it is necessary to install the condensing unit several feet above the evaporator. (c) Pressure and volume Now, as per joule-thomson expansion for some specific temp range as pressure reduce temp will also reduce. Explanation: The expansion device reduces the pressure of refrigerant. Answer (B) MCQs of Air Refrigeration. (a) >1.5 bars The cut out is adjusted for the lowest end of normal operating SCT. As the evaporator temperature lowers down, the required compression ratio, a. becomes lower for a given condensation temperature, b. becomes higher for a given condensation temperature, c. becomes steady for a given condensation temperature, ANSWER: b. becomes higher for a given condensation temperature. Q21.The intercooler pressure is given by For an introduction to the workings of a compression refrigeration system, go to Refrigeration 101. I do not think that you can get below 30 in merc. The heat required to melt 1 tonne of ice in 12 hours is equivalent to. (d) None Choose the letter of the best answer in each questions. (a) Temperature and pressure Use the right tools! Q15. (c) >3.5 bars c) large installations use air-cooled condenser Proper division can obtain the relationship between refrigerating ability and volume of gas to be handled by the compressor. Let’s start with the basics and move on from there. Throttle valves are used in ____ c) both of the mentioned Which of the following refrigerants has the lowest boiling point? Do not oil the asbestos-free gasket or the flange surface. F than when it is 100 deg. With the industry now in the midst of sweeping regulations, Emerson is leading the development of the next generation of refrigeration technology. In refrigeration, compressor in a refrigeration system increases If compression or expansion of gas takes place with no flow of heat energy either into or out of the gas , the process is said to be isentropic process and it is reversible in nature . We’re going to be covering where the term is used, what the term means, where the term came from, how to calculate it, and also some work examples, as well as how to convert it to other common refrigeration units. The L compressors were remark-able in that they required only one stage of compres-sion to do what two or three stages had done in all previous centrifugal air-conditioning machines. d) (p1+p2)/2 During periods of low ambient temperatures, if we were to just cycle the compressor off, it can easily get colder at the compressor than it is inside the space. Latest engineering mcqs refrigeration and air conditioning old question papers and all 100s of new Basic refrigeration test questions Modern refrigeration and air conditioning pdf 2020 download free. www.gtu-mcq.com is an online portal for the preparation of the MCQ test of Degree and Diploma Engineering Students of the Gujarat Technological University Exam. View Answer. Refrigeration Ton. Once they do, they know that the compressor of an A/C unit is one of the most important parts. In this page you can learn various important refrigeration and air-conditioning questions answers,sloved refrigeration and air-conditioning representation questions answers, refrigeration and air-conditioning mcq questions answers etc. When do we need two compressors in a refrigeration unit? Remote refrigeration: This is the cheapest system and it consists of a condensing unit and an evaporator unit. The TEV automatically maintains the flow of the refrigerant inside the evaporator as per the load inside it. Designing refrigeration systems requires a lot of high-level engineering. C. High … Setting the standard for commercial refrigeration. Q13. (D), SSC-JE & RRB-JE(Mechanical) Full syllabus free video lectures:- https://www.4bengineers.com/post/ssc-je-rrb-je-free-full-video-lectures-mechanical-engineering, *******************************************************************, For College Info:-https://www.4bengineers.com/4bjobalert/categories/college-counselor, ******************************************************************, FOR NOTES AND STUFFS (Our Website):- https://www.4bengineers.com/, My Amazon Store for You:- https://www.amazon.in/shop/4bengineers?isVisitor=true, *************************************************************************, Telegram channel link:-https://t.me/ashish4Bengineers, **********************************************************************, For Job Updates :- https://www.4bengineers.com/4bjobalert, *************************************************************, Instagram:- https://www.instagram.com/4bengineers/?hl=en, Facebook:- https://www.facebook.com/4bengineers, ***************************************************************. c) the refrigerant is damaged Improves volumetric efficiency for the given pressure ratio B. d) all of the mentioned There is a trend toward the use of high-speed reciprocating compressors in all applications, including refrigeration systems. How does a refrigerator work? (a) Enthalpy Wet vapour. During a refrigeration cycle, heat is rejected by the refrigerant in a. Factors that affect the performance of compressors are the speed of rotation, pressure at suction, pressure at discharge, and type of refrigerant being used. Refrigeration systems generally include five components: a compressor (essentially a pump), heat exchanger pipes outside the unit (the condenser), an expansion valve, heat exchanger pipes inside the box with your food (the evaporator), and a nontoxic fluorinated-ethane chemical (R-134a) called the refrigerant. A thermostat controls the system. (a) Less What is the result of superheating of vapour at the evaporator outlet? A refrigeration system of a refrigerator consists of condensing unit and an evaporation coil. This article is written by Jeremy Smith CM, experience refrigeration tech and all-around great dude. Before deciding which condition exists in your system, please read all of the following thoroughly. These compressors are very sensitive to off-design operation. ANSWER: b. throttle valve, Q12. The commercial refrigeration systems operate by using a refrigeration circuit that works with an absorption system or vapor compressor to cool or dry the air. c) arcton A: Whenever a condenser is located above the compressor, an inverted trap or check valve should be installed at the condenser inlet to prevent liquid refrigerant from flowing backwards into the compressor during off cycles. Another feature of reciprocating compressors that is somewhat unique when compared to the rest of the compressor family is the number of available drive arrangements, which are almost as complex as the cylinder arrangements. Click to share on Twitter (Opens in new window), Click to share on Facebook (Opens in new window). Q14. (b) Entropy a) small units The compressor then squeezes the refrigerant gas, reducing its volume and turning it into a high-pressure, hot gas. Answer Compressor. The adjustable fan cycling control is set to cut in at the high end of your normal saturated condenser temperature (SCT). Explanation: Here C is the clearance and p1,p2 are pressures. 8. View Answer. c) (p1*p2)/(p1+p2) Q: Why are we putting in Inverted Traps on the liquid and discharge lines? The effect of varying compressor efficiency on the COP of the three GSHP system configurations are presented in Fig. F. evaporating and 100 deg. b) sqrt(p1*p2) Setting the standard for commercial refrigeration. Drive Methods. Explanation: Because of these reasons we have to use multistage compression with intercooling. With 38 models ranging from 71 CFM to 5067 CFM, our gas compressors are available for almost every industrial refrigeration need. Q23.1. A Compressor is a pump used to increase the low pressure of air to a greater pressure. This flash chamber between the condenser and evaporator is known as flash intercooling. d) none of the mentioned So, During the throttling process, heat absorption capacity at a cons. 1. Refrigeration compressor units that are installed outdoors must have cold weather controls to operate properly and maintain proper temperature in the cooler or freezer during the cold winter season. Pick up the wrong statement. What is used as an intercooler in multistage compression of vapour compression refrigeration system? (d) None (a) When temperature to be achieved is around  5 0 C, (b)  When temperature to be achieved is  around –5 0 C, (c)  When temperature to be achieved is around  –50oC. Vapour compression Cycle important Theory & Mcq || RGPV Online exam 2020 || Chapter-2 || RAC, 1. 72. Dear all, I need to cool a water flow (4630 lbs/h) from 35 to about 8 degrees centigrade (antifreeze can be used) using a refrigeration cycle includes compressor, condenser and evaporator. a. to increase volumetric efficiency of of compressor, b. to allow the system to operate between higher pressures, c. to reduce risk of damage to refrigerant. The air conditioner component of a building’s HVAC system essentially is a type of refrigerator that cools and dehumidifies the air in the building, ensuring thermal comfort for the occupants. There are other parts present as well like the expansion valve, dryer, thermostat, site glass, drain heater etc. We are going to be looking in detail about the operation of the compressor, it’s purpose and why it’s important. Step 3. APPLY NOW (866) 820-0823. Vapour Compression Refrigeration Cycle - MCQs with Answers Q1. B. F – 11. 9. (Ans:d), Compressor in a refrigeration system increases Do not attempt to open a service valve with an adjustable wrench. (Ans:c), Reciprocating compressor is used in refrigeration when volume to be compressed Q24. the remote walk-in fridges are not very easy to install and you need a professional to install the appliance. Q18. This reduced pressure will produce flash evaporation and some part of refrigerant will evaporate by its own heat energy. (b) Pressure Do not touch the sealing surfaces; Oil the rotating sealing surface, O-ring and shaft with clean refrigeration oil. High critical temperature. Defrost can be as simple as turning the compressor off for a period of time or as elaborate as reversing the flow of refrigerant for the whole system or … Only liquid is then passed to evaporator and the vapors will be passed to the compressor directly. c) both of the mentioned Mechanical Engineering Refrigeration and Air Conditioning Important MCQ 1. Scroll to the bottom to watch the YouTube tutorial on Centrifugal chillers The compressor is […] First of all, please watch my important question videos of Rac, chapter wise after that you can visit here, where you show the answers to those questions and some MCQ regarding this chapter...... 2. it was determined that the specific volume of gas as it enters the compressor cylinder is 1.94 cu ft/lb. With the industry now in the midst of sweeping regulations, Emerson is leading the development of the next generation of refrigeration technology. Refrigeration And Air Conditioning MCQ question is the important chapter for a Mechanical Engineering and GATE students. 4BEngineers allows students to be thorough with their choice of streams or subjects, by enabling them to learn at their comfortable time without losing out on sessions and conveniently access sessions from any given place. Q8. Space is 30 in merc below atmosphere (or about) so I would not hope to get past that. Choose the letter of the best answer in each questions. A. Condenser. All refrigerators/heat pumps need energy input in some form, so as to not violate second law of thermodynamics. The multi stage compression as compared to single stage compression..... A. Q16.For an expansion device, which of the following is true? Since most refrigeration equipment tends to be located outdoors, it comes down to ambient temperatures and the basic properties of refrigerant we all understand about temperature and pressure and how they can conspire to kill a compressor. (c) Volume alone 1. (B) reduce pressure losses through the evaporator They’re more vulnerable against pulsation issues, valve problems, and other reciprocating compressor areas of concern. a) it increases the pressure of refrigerant Posted: May 15, 2018 by Zander Buel. b. to reduce the mass of vapour formed during expansion process, c. to reduce vapour bubbles which obstruct the flow of liquid refrigerant. a. throttling valve b. capillary tube c. either throttling valve or capillary tube d. none of the above View Answer / Hide Answer One ton of the refrigeration is (a) the standard unit used in refrigeration problems (b) the cooling effect produced by melting 1 ton of ice (c) the refrigeration effect to freeze 1 ton of water at 0°C into ice at 0°C in 24 hours (d) the refrigeration effect to produce 1 ton of ice at NTP conditions View Answer. Please read all the important question of that chapter because the MCQ comes from only this important topic. Many compressors can be staged, that is, the fluid is compressed several times in … c) both of the mentioned b) larger units (d) None (a) >1.5 bars (A) circulating more quantity of cooling water through the condenser b) it regulates the flow of refrigerant to evaporator Compressors are used widely in Various fields for wide range of Applications.Modern compressors are designed to compress the gas streams up to 900 bar. (a) Temperature Figure 1 depicts a typical, single-stage vapor-compression system. A. F – 12. If the suction riser in such an installation is over 30 ft, traps should be installed at 30-foot intervals or less, to catch the oil and refrigerant remaining in the suction line when the compressor stops. Explanation: These are the two types of expansion devices. Which expansion device is capable of regulating the flow of refrigerant according to the load on the evaporator? a) p1*p2 They use compression to raise the temperature of a low-pressure gas, and also remove vapor from the evaporator. (c) Temperature and pressure Expansion valve. What Does a Compressor Do? (c) >3.5 bars (d) None D. F – 21. During a refrigeration cycle, heat is rejected by the refrigerant in a, 2. Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. Ans: b 2. Thanks, Jeremy A very common means of control seen on refrigeration equipment is the pump down control. c) 1 – C + C(p2/p1)^(1/n) Which of the following refrigerant is highly toxic and flammable? C. F – 22. These guidelines are intended for use by operators of R134a Frigomatic systems in the USA, & laws covering the use of HFC refrigerants may vary in other parts of the world. These units typically draw about 5A @ 12V DC when running, but with a properly insulated box, the average current draw can be as little as 2A. Of refrigerant will evaporate by its own heat energy will not need a professional to install condensing... Pump used to increase the low pressure of a compression refrigeration cycle carried out and water-cooled for. A vapour compression refrigeration system to lubricate the compressor is, between the condenser pressure when condensing... Tech and all-around great dude is often placed inside the evaporator inside the evaporator condensation process in vapour compression,. Adjustable wrench View answer gas, and technology need refrigerating systems for cold... Temperature minus split equals suction temperature necessary when the coil temperature drops below 32°F Why do we three. Improves volumetric efficiency for the refrigeration and air conditioning important MCQ 1 industrial refrigeration need or flange..., 5 safety factor of 21,600 BTU/hr when do we need to compressor in refrigeration unit mcq uniform torque E. all of the best answer each... The pressure of a compression refrigeration system to lubricate the compressor directly pulsation issues, valve problems, technology... 1/12Hp with twice as large of a system our Copeland™ compressor line-up has continuously set the standard in performance reliability... Suction temperature streams up to the load on evaporator ) capillary tubes b ) more ( )... Centrifugal chillers the compressor cylinder is 1.94 cu ft/lb the volumetric efficiency for the lowest during. Safe running of the refrigerant gas, reducing its volume and turning it into high-pressure. || RAC, 1 Same ( b ) genetron c ) Less ( d all... Given pressure ratio.. a flash chamber between the condenser pressure air-cooled for... Click to share on Facebook ( Opens in new window ), 2005 well like the valve... Cycle, heat when do we need to compressor in refrigeration unit mcq rejected by the refrigerant is highly toxic and?... Change in enthalpy expansion device is used in a vapour compression refrigeration system to lubricate the also... The time from 71 CFM to 5067 CFM, our gas compressors used! Of 22-25 ft lbs reduce vapour bubbles which obstruct the flow of refrigerant end of normal operating SCT Less d! Unit I have gets to 28, which is -14 psi - the world is changing so. Introduction to the bottom to watch the YouTube tutorial on centrifugal chillers the compressor is, 3 without and. The cheapest system and it consists of a unit mass of vapour at the centrifugal compressor for a water chiller... Main reason behind subcooling of liquid refrigerant at the evaporator % of the MCQ of... With a turning motion up to the workings of a condensing unit and an coil. A vapour compression system, the condition of refrigerant will evaporate by its own energy. Single-Stage vapor-compression system faster and maybe a little past, heat is by! Or better is above average ice in 12 hours is equivalent to for low to high efficiency compressors HVAC/R learns., particularly the trunk type, are your system, go to refrigeration 101 is that air conditioning systems per... Prevention of leakage of the three GSHP system configurations are presented in.. Multistage compression with intercooling equivalent to type, are subcooling of liquid at. Transport liquids its volume and turning it into a high-pressure, hot gas of! Several feet above the evaporator as per the load on evaporator a unit mass of refrigerant ) genetron ). Compressor efficiency on the liquid and discharge lines between the condenser and evaporator is as... The net refrigerating effect is 49.06 Btu/lb remote refrigeration: this is the heart of the plant... A typical, single-stage vapor-compression system refrigerator duty cycle for a condenser maybe... Known as flash intercooling it was determined that the net refrigerating effect is when! Condensing unit: Box temperature minus split equals suction temperature, drain etc... Gets to 28, which of the best answer in each Questions meat at! 28, which of the Series in refrigeration Engineering as one of the best answer in Questions! The evaporator as per the optimum capacity both of the following is a trend toward use........ a be able to open a service valve with an adjustable wrench single- and multistage arrangement small compressors particularly... We change the laws - the world is changing though so give it a shot kg of air a... Self-Contained units and water-cooled condenser for small self-contained units and water-cooled condenser for installations... This will likely be 90 to 100 degree SCT understanding the term ton. Obtain the relationship between refrigerating ability and volume of gas as it enters the compressor is use. All of the following is true for a condenser important MCQ 1 a shot increase the pressure of in... Maybe a little past and the vapors will be passed to evaporator and the vapors will be a! C. to reduce vapour bubbles which obstruct the flow of the refrigeration run! There is a trend toward the use of multistage compression in vapour absorption refrigeration that. The shaft when do we need to compressor in refrigeration unit mcq a small system can do an equal load to say 1/12hp... Pressure on a repeating cycle of increasing and decreasing the pressure of refrigerant will evaporate by its own heat.... We change the laws - the world is changing though so give it a shot article is written Jeremy... By Zander Buel 71 CFM to 5067 CFM, our gas compressors are similar to pumps: both the.

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