1. ME– VII SEM Refrigeration & Air Conditioning Manav Rachna College of Engg.

2. OBJECTIVES To Learn Basic operation of refrigeration and AC systems. Principle components of refrigeration and AC systems. Thermodynamic principles of refrigeration cycle. Safety considerations. Manav Rachna College of Engg. Uses of Systems Cooling of food stores, buildings and cargo. Cooling of electronic spaces and equipment. CIC, Radar, Sonar, Radio, C omputers etc. Air conditioning for Aero plane, Space ships, Naval Ships, Train, Bus, Car etc.

3. DEFINITION Refrigeration may be defined as the process of removing heat from a body or enclosed space so that its temperature is first lowered and then maintained at a level below the temperature of surroundings. The system maintained at the lower temperature is known as refrigerated system while equipment used to maintain this lower temperature is known as refrigerating equipment. Work is required to transfer heat from lower temperature body to higher temperature body. Amount of heat removed by refrigerating equipment from refrigerated system is known as refrigerating effect. Manav Rachna College of Engg.

4. UNIT OF REFRIGERATION The unit of refrigeration is ton of refrigeration or simply ton denoted by TR. One ton of refrigeration means amount of heat required to remove from one ton of water at 0 0 C to produce ice at 0 0 C in 24 hours. The latent heat of ice is 334.9 kJ/Kg and one tons water equals to 907.18 kg therefore 1 ton of refrigeration equals to, 1 TR = (334.9 x 907.18) / (24 x 3600) = 3.516 kW

5. COEFFICIENT OF PERFORMANCE (COP) The performance of refrigerators and heat pumps is expressed in terms of coefficient of performance (COP), defined as COP HP is larger than COP R. Under the same operating conditions, the COPs are related by

6. REFRIGERATION CYCLE Refrigeration - Cooling of an object and maintenance of its temperature below that of surroundings. Working substance must alternate b/t colder and hotter regions. Most common: vapor compression Reverse of power cycle Heat absorbed in low temp region and released in high temp region

7. GENERIC REFRIGERATION CYCLE Manav Rachna College of Engg.

8. THERMODYNAMIC CYCLE Manav Rachna College of Engg.

9. COMPONENTS Refrigerant Evaporator/Chiller Compressor Condenser Receiver Thermostatic expansion valve (TXV)

10. REFRIGERANT Definition:- It is a heat carrying medium which during their cycle compress, condense, expense and evaporate. It absorb heat from a low temperature system and discard the heat to higher temperature system. Manav Rachna College of Engg.

11. HISTORY OF REFRIGERANTS 1830s - Jacob Perkins - Vapor Compression (ether) 1851 - John Gorie - Patent for Vapor Compression Cycle 1859 R-717 / R-718 (Ammonia / Water) 1866 CO2 - Naval Applications 1873 - R-717 (Ammonia) Commercial Refrigeration – Karl Linde 1875 - R-764 (Sulfur dioxide) 1920s -R-600a (Isobutane) & R-290 (Propane) 1922 - Willis Carrier - R-1130 (Dielene) 1926 - R-30 (Methylene Chloride)

12. PROPERTIES OF REFRIGERANTS Desirable properties: High latent heat of vaporization – max. cooling Non-toxicity (No health hazard) Desirable saturation temp (For operating pressure) Chemical stability (Non-flammable/non- explosive) Ease of leak detection Low cost Readily available Commonly use FREON (R-12, R-114, etc.)

13. EVAPORATOR/CHILLER Located in space to be refrigerated Cooling coil acts as an indirect heat exchanger Absorbs heat from surroundings and vaporizes Latent Heat of Vaporization Sensible Heat of surroundings Manav Rachna College of Engg. Slightly superheated (10°F) - Ensures no liquid carryover into compressor

14. COMPRESSOR Superheated Vapor: Enters as low press r., low temp r. Vapor. Exits as high press r., high temp r. Vapor. Temp r. creates differential (ΔT) promotes heat transfer. Increase in energy provides the driving force to circulate refrigerant through the system Manav Rachna College of Engg.

15. CONDENSER Refrigerant rejects latent heat to cooling medium. Latent heat of condensation (LHC). Condenser used may be air cooled or water cooled. RECEIVER Temporary storage space & surge volume for the sub-cooled refrigerant. Serves as a vapor seal to prevent vapor from entering the expansion valve.

16. EXPANSION DEVICE Thermostatic Expansion Valve (TXV) Liquid Freon enters the expansion valve at high pressure and leaves as a low pressure wet vapor. (vapor forms as refrigerant enters saturation region). Controls: Pressure reduction Amount of refrigerant entering evaporator controls capacity. Manav Rachna College of Engg.

17. AIR CONDITIONING Purpose: Maintain the atmosphere of an enclosed space at a required temp, humidity and purity. Refrigeration system is at heart of AC system. Types Used: Self-contained Refrigerant circulating Chill water circulating Manav Rachna College of Engg.

18. AC SYSTEM TYPES Self-Contained System Add-on to ships that originally did not have AC plants Not located in ventilation system (window unit) Refrigerant circulating system Hot air passed over refrigerant cooling coils directly Chilled water circulating system Refrigerant cools chill water Hot air passes over chill water cooling coils

19. Basic AC System

20. The vapor compression refrigeration cycle is a common method for transferring heat from a low temperature to a high temperature.

21. REVERSED CARNOT REFRIGERATOR AND HEAT PUMP Shown below are the cyclic refrigeration device operating between two constant temperature reservoirs and the T-s diagram for the working fluid when the reversed Carnot cycle is used. Recall that in the Carnot cycle heat transfers take place at constant temperature. If our interest is the cooling load, the cycle is called the Carnot refrigerator. If our interest is the heat load, the cycle is called the Carnot heat pump.

22. CONT…

23. The standard of comparison for refrigeration cycles is the reversed Carnot cycle. A refrigerator or heat pump that operates on the reversed Carnot cycle is called a Carnot refrigerator or a Carnot heat pump, and their COPs are

24. CLASSIFICATION OF REFRIGERANTS This text is based on the American standard ANSI/ASHRAE 34 published in 2001 and entitled “Designation and Safety Classification of Refrigerants”. This classification makes it possible to designate all refrigerants used in a clear and internationally recognized manner by classifying them according to their chemical composition. Main types 1. Primary 2.Secondary

25. Primary: They are directly take part in refrigeration. 1.Helo Carbon Refrigerant 2. Azeotrope Refrigerant 3.Inorganic Refrigerant 4.Hydro carbon Refrigerant Secondary:- They first cool primary refrigerant and than used for cooling purpose. 1. Water 2. Brine 3. Inhibited Glycols CLASSIFICATION OF REFRIGERANTS CONT..

26. NOMENCLATURE OF REFRIGERANTS Refrigerants are denotes by ‘ R’ followed by certain number as R-11, R-12, R-114 1. For saturated Hydrocarbon:- Cm + Hn + Fp + Clq, n +p +q=2m+2 m- No.of carbon atoms n- No.of hydrogen atoms p- No.of fluorine atoms q- No.of chlorine atoms Nomenclature- R(m-1)(n+1)(p)

27. NOMENCLATURE OF REFRIGERANTS 1. For Unsaturated Compounds:- n + p + q = 2m Nomenclature - R1(m-1)(n+1)(p) Eco friendly Refrigerants 1.Hfcs 2. Hcfc-123 3. Hfc-134a

28. INTRODUCTION TO CRYOGENICS Cryogenics is the study of how to get to low temperatures and of how materials behave when they get there. Besides the familiar temperature scales of Fahrenheit and Celsius (Centigrade), cryogenicists use other temperature scales, the Kelvin and Rankine temperature scales. OR Cryogenics may be defined as the branch of physics which deals with the production of very low temperature and their effect on matter. It may also be defined as the science and technology of temperatures below 120 0 K. The word “cryo” is derived from a Greek word “kruos” which means cold.

29. ADVANTAGES OF CRYOGENIC PROCESSING Advantages of Cryogenic Processing: The following properties are attained to the materials treated:- Increases wear resistance, Increases corrosion resistance,Good dimensionality,high strength, Good quality Cost reduction in the material manufactured, lower stress corrosion etc. Cryogenic heat treatment helps to reduce the stored stress in the metal by creating a unified bond between the crystals.

30. CONT… Cryogenics are also used to treat many types of sports equipment, the most common being golf clubs. Because cryogenics increases the molecular density of treated materials, it improves the distribution of energy (in this case kinetic energy) through the object. The treatment also increases the rigidity of the metal, which in this case might affect the shaft of the golf club. Combined, the increases in kinetic energy distribution and rigidity of the shaft make for a longer and straighter drive.

31. CONT… Cryogenics can be applied to almost everywhere in every field. It finds its application in military, tooling industry, agricultural industry, aerospace, medical, recycling, household, automobile industry, cryogenics is found to improve the grain structure of everything treated be it metal or plastic or coils or engines or musical instruments or fiber. This field could be put to many other applications in various fields. Its reaches in the mentioned industries hold a good chance of extension. Hence Cryogenics proves to be very promising for the future in this world of materials.

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