Effects of Changing Different Components in a Compression Refrigeration System
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This document describes the components and processes of a vapor compression refrigeration system. It contains information on common types of compressors (reciprocating, rotary, centrifugal), condensers (air-cooled, water-cooled, evaporative), and evaporators. It discusses using different compressor types based on required cooling capacity and advantages of each condenser type. The document also mentions using multiple evaporators to increase cooling capacity and reduce evaporator size.
Effects of Changing Different Components in a Compression Refrigeration System
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- 2. To Study the Effects of Changing Different Components in a Compression Refrigeration System Title of the Mini Project 2
- 3. Group Description Hashim Hasnain Hadi Roll No: 13ME36 Ashtar Abbas Roll No:13ME38 Ghulam Sarwar Roll No: 13ME19 Group Advisor Engr. Faisal Maqbool 3
- 4. Introduction of a Vapor compression Refrigeration System: 4 The vapor-compression refrigeration cycle is the ideal model for refrigeration systems, air conditions and heat pumps. It is comprised of four components: 1) Evaporator 2) Compressor 3) Condenser 4) Expansion valve • It consist of four processes: 1-2 Isentropic compression in compressor. 2-3 Constant-pressure heat rejection in a condenser. 3-4 Throttling in an expansion device. 4-1 Constant-pressure heat absorption in an evaporator. Two-phase liquid-vapor mixture
- 5. Introduction of a Vapor compression Refrigeration System: 5
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- 7. ` 7 Compressor: Reciprocating , Discharge: 8m3/hr Cooling Unit in Thermodynamic s Lab of MED BUETK. Throttling Valve Condens er Capacity 3000 kCal/Hr For 60 Hz Power Supply, 2500 kCal/Hr For 50 Hz Chille r
- 8. Types of Compressors : 8 Reciprocating compressors Rotary compressors Centrifugal compressors
- 9. Using Reciprocating compressors: 9 Most commonly used compressor for small scale applications (refrigerators, freezers, ice machines, etc.…) Very economical to operate Piston and cylinder design, Works on the principal of trapping and compressing refrigerant vapor (positive displacement compressor High output pressure Low flow rate
- 10. Using Rotary compressors: 10 Typically small in size (used for lower capacity applications – ie. window air conditioners, PTAC’s, etc.…) Very reliable Quiet Less efficient Works on the principal of trapping and compressing refrigerant vapor (positive-displacement compressor)
- 11. Using Centrifugal compressors: 11 Typically large in size (used for high refrigeration capacity applications – i.e.. Water chillers, commercial air-conditioning & refrigeration systems, etc.…) Very reliable High flow rate Highly efficient Low output pressure Uses centrifugal force via a rotating impeller to compress refrigerant vapor(Dynamic
- 12. Usage of different type of Compressors according to the Required cooling Capacities: 12
- 13. Type of condensers: 13 Air-Cooled condensers Water-Cooled Condensers Evaporative Condensers
- 14. Using Air-Cooled condensers: 14 Advantages: Simple in construction__ no pipes are required for air. Disposal of warm air not a problem Less fouling(scaling inside tubes) Low maintenance cost. • Disadvantages: Less specific heat Capacity of air Large flow rate of air is required Low thermal conductivity Small heat transfer co-efficient of air Less cop.
- 15. Using Water-Cooled condensers: 15 Advantages: High thermal conductivity of water High specific heat of water Less flow rate is required to compensate the same heat as that in case of air-cooled compressor High heat transfer co-efficient High cop • Disadvantages: Large installation and maintenance cost Pump is required for water circulation Large energy consumption
- 16. Using Evaporative condensers: 16 30% to 40% less compressor KW consumed than air cooled condensing Less Air over coil, therefore quieter than air cooled condensing Less coil required so less space on roof for equipment than air cooled. an evaporative condenser requires less coil. In comparison with an air-cooled condenser, surface and airflow to reject the same heat, or alternatively, greater operating efficiencies can be achieved by operating at a lower condensing temperature • Greater Compressor Life since Evap Condensing Compressors work at lower pressures
- 17. Reduced Connected kW: 17 Wire Size # 350 MCM Wire Size # 2/0 Typical 100 Ton Air Cooled Condenser 205 Operating Amps 135 kW Typical 100 Ton Evap Cooled Condenser 157 Operating Amps 103 kW
- 18. Expansion valve: 18 If the refrigerant at the condenser exit is not completely condensed. Because vapor occupies much more space than liquid, the throttling valve will not function properly if vapor can enter from the condenser. One approach to dealing with this is to locate a liquid receiver downstream of the condenser to assure the availability of liquid to the expansion device
- 20. Using Multi Evaporators: 20 Expansion process is one of the main factors responsible for energy loss Not only the cooling capacity but also increase the size of evaporator. This problem can be eliminated by adopting multi- stage expansion with flash chamber where the flash vapors is removed after each stage of expansion as a consequence there will be increase in cooling capacity and reduce the size of the evaporator. Work input can also be reduced by replacing multi- stage compression or compound compression with single stage compression. Refrigeration effect can also be increased by passing the refrigerant through sub cooler after condenser to
- 21. Schematic diagram of a Vapor Compression Refrigeration System with Actual Multiple Evaporators 21
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