Refrigeration and Airconditioning

IIT Kharagpur Course , Prof. M.Ramgopal

Lecture 1: History of Refrigeration

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Refrigeration and Air Conditioning

Course Description :

Definition of Refrigeration and Air Conditioning:History of Refrigeration and Air conditioning:History from conceptual point of view:Ice production by nocturnal cooling in ancient India and application of evaporative cooling in India. Use of natural ice, ice houses and ice trade - Vapour Compression Refrigeration Systems - Vapour Absorption Refrigeration Systems - Air Cycle Refrigeration Systems - Miscellaneous Systems (Vapour Jet Refrigeration Systems,Thermoelectric systems, Vortex tube systems, Intermittent-Solar Refrigeration Systems, Combined Cycles) - History from Refrigerant development Point of View - Early refrigerants (SO2, CO2, CH3Cl, CH4, C2H6 etc) - Introduction of CFCs and HCFCs - Ozone layer depletion - HFCs, HCs, NH3, CO2, H2O etc - History from compressor development point of view - Low-speed steam engine driven compressors - High-speed electric motor driven compressors - Rotary vane compressors - Centrifugal compressors - Screw compressors - Scroll compressors - History of Air Conditioning;Applications of Refrigeration and Air Conditioning:Comfort Air Conditioning:Residential air conditioning - Commercial air conditioning - Industrial air conditioning;Industrial Refrigeration:Chemical and process industries - Dairy plants - Petroleum refineries - Food processing and food chain - Miscellanous;Methods of producing low temperatures:Applications of Refrigeration and Air Conditioning:Using enthalpy of mixing (mixing of salt with water) - Expansion in a turbine - Throttling - Thermoelectric effects - Adiabatic demagnetization;Thermodynamics:1st law of thermodynamics for open and closed systems - 2nd law of thermodynamics, Kelvin-Planck and Clausius statements, and Clausius inequality. 3rd law of thermodynamics - Heat Engines, Heat Pumps and Refrigeration Systems, Maximum COP - Thermodynamic properties - Thermodynamic processes - T-s and p-h diagrams;Fluid Mechanics:Continuity and Momentum equations - Bernoullis equation and friction factor;Heat Transfer:Modes of heat transfer - Concept of thermal resistance and overall heat transfer coefficient - Radiative heat transfer coefficient - Forced Convection, Free Convection, Boiling and Condensation heat transfer coefficients - Air Cycle Refrigeration Systems:Reverse Carnot Cycle and its limitations:Bell Coleman, Joule or Reverse Brayton Cycle - Aircraft refrigeration cycles - Joule Thompson coefficient and Inversion Temperature - Linde, Claude and Stirling cycles for liquefaction of air;Vapour Compression Refrigeration Systems:Comparison of Vapour Compression Cycle and Gas cycle - Ideal refrigeration cycle Reversed Carnot cycle and maximum COP - Deviations of practical cycles from Carnot cycle - Standard vapour compression refrigeration cycle (SSS cycle) - Superheat horn and throttling loss for various refrigerants, efficiency - Modifications to standard cycle liquid-suction heat exchangers:Grindlay cycle and Lorenz cycle - Optimum suction condition for optimum COP Ewings construction and Gosneys method - Actual cycles with pressure drops and heat transfer - Complete Vapour Compression Refrigeration System - Multipressure, multistage systems, optimum intermediate pressure - Two stage ammonia and halocarbon systems - Multi-evaporator systems - Cascade systems, optimum intermediate temperature - Manufacture of dry ice and supercritical CO2 cycle - Autocascade cycle;Vapour Absorption Refrigeration Systems:Working principle:Maximum COP of the ideal VARS - Properties of Mixture - Simple absorption refrigeration system;Lithium bromide-Water Absorption Refrigeration Systems:Operating principles and applications - Refrigerant-absorbent properties using tables and charts - Performance evaluation and methods of improvement - Practical problems crystallization and air leakage - Commercial systems Single and multistage systems;Aqua Ammonia Refrigeration System:Operating principles and applications - Refrigerant-absorbent properties using tables and charts - Practical problems and Principle of Rectification;Aqua-ammonia Absorption Refrigeration Systems:Analysis of Generator- Exhausting Column and Rectification column -Dephelgmator - Three fluid system - Solar energy based adsorption refrigeration systems;Refrigeration system components:Compressors - Reciprocating Compressors:Constructional details open , hermetic and semi-sealed compressors - Performance of the ideal compressor - Clearance volumetric efficiency Effects of evaporator and condenser pressures - Actual volumetric efficiency - Effects of cylinder cooling, heating and friction - Empircial equations for actual volumetric efficiency - Power requirements of ideal and actual compressors - optimum work for given condenser and evaporator pressures, mean effective pressure,pull down characteristics - Compressor discharge temperatures and need for cooling - Capacity control;Centrifugal Compressors:Basic principle of dynamic compressor - Velocity diagrams - Efficiency considerations - Construction details, applications and performance characteristics - Comparison with reciprocating compressors
Screw compressors- Basic principles- single screw and double screw compressors - Working principle, work requirement and performance characteristics - Comparison with reciprocating and centrifugal compressors - Rotary- single vane and multi-vane compressor

Condensers:Classification based on type of construction, flow direction - Condensing capacity and Heat Rejection Ratio - Correlations for condensing heat transfer coefficients - Thermal design of condensers - Effects of fouling and noncondensible gases on performance;Evaporators - Classification based on type of construction, flow direction etc - Correlations for boiling heat transfer coefficients for various configurations - Design and performance aspects - Effects of pressure drops and frost formation - Use of Wilsons plots - Expansion devices - Capillary tubes - Applications, operating characteristics and selection - Thermostatic expansion valves - Applications and operating characteristics - Internal vs external equalizers - Cross charging, gas charging, liquid charging and fade out point - Automatic expansion valves - Float valves Low side and high side float valves - Electronic expansion valves;Refrigerants:Primary and secondary refrigerants:Designation of Refrigerants - Desirable properties of refrigerants including solubility in water and lubricating oil, material compatibility, toxicity, flammability, leak detection,cost, environment and performance issues - Thermodynamic properties of refrigerants - Synthetic and natural refrigerants - Comparison between different refrigerants vis a vis applications - Special issues and practical implications - Refrigerant mixtures zeotropic and azeotropic mixtures;Properties of moist air (psychrometry):Composition of moist air:Methods for estimating moist air properties:Important psychrometric properties - Dry bulb temperature - Humidity ratio - Relative humidity - Degree of saturation - Dew point temperature - Enthalpy - Adiabatic saturation - Thermodynamic wet bulb temperature and wet bulb thermometer - Relations between psychrometric properties - Introduction to humidity ratio vs. dry-bulb temperature psychrometric chart and ASHRAE chart.Use of psychrometric charts and moist air tables, Goff and Gratch tables;Psychrometric Processes:Sensible cooling and heating, RSH - Humidification and dehumidification, RLH - Combined heat and mass transfer processes, RTH, RSHF,Straight line law coil bypass factor and ADP - Cooling and dehumidification - Heating and humidification - Psychrometric calculations for simple airconditioning system and for return air systems with bypass factor. RSHF, GSHF and ESHF - Cooling and humidification (evaporative cooling) - Adiabatic mixing - Spray washers and cooling towers;Air conditioning systems for comfort:Thermal comfort. Heat transfer from human body by sensible and latent heat transfer. Metabolic heat generation, steady state and unsteady state model for heat transfer, effect of clothing and definition of effective temperatures. PMV and PPD. ASHRAE comfort chart - Inside and Outside design conditions - Summer air conditioning systems - Winter air conditioning systems - All year air conditioning systems - Infiltration - Indoor Air Quality (IAQ) - Heating and Cooling load calculations - Heating and Cooling load calculations - Heat transfer through building structure - Winter heating load calculations - Summer cooling load calculations - Fixing of supply air conditions for summer air conditioning - Air conditioning Systems - Fan and Duct Systems - Transport air conditioning Systems - Control systems for Refrigeration and Air conditioning applications

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