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Compressed air and refrigeration system
- 1. ENERGY EFFICIENCY IN ELECTRICAL Utilities D.PAWAN KUMAR
- 2. ENERGY EFFICIENCY IN COMPRESSED AIR SYSTEM
- 3. Air Is Free !!! Compressed Air Is Free !!! Not
- 5. A TYPICAL COMPRESSED AIR SYSTEM
- 9. STAGES OF RECIPROCATING COMPRESSOR
- 10. STAGES OF RECIPROCATING COMPRESSOR
- 11. SCREW COMPRESSOR
- 13. GENERAL SELECTION CRITERIA FOR COMPRESSORS
- 16. COMPRESSOR EFFICIENCY N = No. of stages K = Ratio of specific heats (1.35 for air) Ps = suction pressure in kg/cm2 Pd = Discharge pressure in kg/cm2 Q = Actual air flow (m3/min.) Actual kW = 3 V I PF as measured Efficiency of compressor and motor combination = Theoretical kW =
- 17. EFFECT OF INTAKE AIR TEMPERATURE ON POWER CONSUMPTION Every 4 0 C rise in inlet air temperature results in a higher energy consumption by 1 % to achieve equivalent output. Hence, cool air intake leads to a more efficient compression.
- 18. EFFECT OF PRESSURE DROP ACROSS AIR INLET FILTER ON POWER CONSUMPTION For every 25 mbar pressure lost at the inlet due to choked filters, the compressor performance is reduced by about 2 percent.
- 19. ELEVATION It is evident that compressors located at higher altitudes consume more power to achieve a particular delivery pressure than those at sea level, as the compression ratio is higher.
- 20. EFFICACY OF INTER AND AFTER COOLERS It can be seen from the table that an increase of 5.5 0 C in the inlet to the second stage results in a 2 % increase in the specific energy consumption. Use of cold water reduces power consumption
- 22. POWER REDUCTION THROUGH PRESSURE REDUCTION A reduction in the delivery pressure of a compressor would reduce the power consumption.
- 23. EXPECTED SPECIFIC POWER CONSUMPTION OF RECIPROCATING COMPRESSORS (BASED ON MOTOR INPUT)
- 24. ENERGY WASTAGE DUE TO SMALLER PIPE DIAMETER Typical acceptable pressure drop in industrial practice is 0.3 bar in mains header at the farthest point and 0.5 bar in distribution system
- 25. DISCHARGE OF AIR THROUGH ORIFICE
- 26. COST OF AIR LEAKAGE Based on Rs. 5 / kWh ; 8000 operating hours; air at 7.0 bar
- 29. AIR AMPLIFIERS Compressed air flows through the inlet (1) into an annular chamber (2). It is then throttled through a small ring nozzle (3) at high velocity. This primary air stream adheres to the coanda profile (4), which directs it toward the outlet. A low pressure area is created at the center (5) inducing a high volume flow of surrounding air into the primary air stream. The combined flow of primary and surrounding air exhausts from the Air Amplifier in a high volume, high velocity flow.
- 34. ENERGY EFFICIENCY IN REFRIGERATION SYSTEM
- 36. TON OF REFRIGERATION 1 ton of refrigeration = 3024 kCal/hr heat rejected. The cooling effect produced is quantified as tons of refrigeration.
- 37. VAPOUR-COMPRESSION REFRIGERATION SYSTEM (R-22)
- 38. VAPOUR – ABSORPTION REFRIGERATION SYSTEM EVAPORATOR CONDENSOR PUMP GENERATOR ABSORBER STRONG SOLUTION WEAK SOLUTION COOLING WATER IN HOT WATER OUT THROTTLING VALVE Regulating Valve Waste Heat/ Direct Fired Heat load In
- 39. PERFORMANCE ASSESSMENT The specific power consumption kW/TR is a useful indicator of the performance of refrigeration system. By messing refrigeration duty performed in TR and the Kilo Watt inputs measured, kW/TR is used as a reference energy performance indicator. The refrigeration TR is assessed as TR = Q C p (T i – T o ) / 3024 Where TR is cooling TR duty Q is mass flow rate of coolant in kg/hr C p is coolant specific heat in kCal /kg / 0 C T i is inlet. Temperature of coolant to evaporator (chiller) in 0 C. T o is outlet temperature of coolant from evaporator (chiller) in 0 C.
- 41. EFFECT OF VARIATION IN EVAPORATOR TEMPERATURE ON COMPRESSOR POWER CONSUMPTION A 1 0 C raise in evaporator temperature can help to save almost 3 % on power consumption.
- 42. EFFECT OF VARIATION IN CONDENSER TEMPERATURE ON COMPRESSOR POWER CONSUMPTION
- 43. EFFECT OF POOR MAINTENANCE ON COMPRESSOR POWER CONSUMPTION
- 48. CALCULATING THE OPERATING LOAD OF A CHILLER PLANT Refrigeration plant Hot well 12 O C Cold well 8 O C Process Chilled water flow – 100 m 3 /hr Refrigeration TR - 100,000 kg/hr x 1 x 4 3000 - 133.33 TR Efficiency - Power drawn by compressor, kW TR m C p 120 133.33 - = 0.9 DT
- 52. THANK YOU
Editor's Notes
- A reciprocating compressor is a positive displacement machine that uses a piston contained within a cylinder to produce compression. The piston traverses the cylinder, sucking in atmospheric air at one end of its stroke, then compressing the air when it reaches the other end of its stroke. This type of machine is available as an 'oil-free' compressor or as a 'lubricated' compressor.The reciprocating compressor probably accounts for largest number of compressors used worldwide
- A screw compressor is a positive displacement machine that uses a pair of intermeshing rotors instead of a piston to produce compression. The rotors comprise of helical lobes affixed to a shaft. One rotor is called the male rotor and it will typically have four bulbous lobes. The other rotor is the female rotor and this has valleys machined into it that match the curvature of the male lobes. Typically the female rotor will have six valleys. This means that for one revolution of the male rotor, the female rotor will only turn through 240 deg. For the female rotor to complete one cycle, the male rotor will have to rotate 1 1/2 times. Screw compressors are available as oil-free machines, oil-lubricated machines and more recently as water lubricated machines.
- As mentioned earlier, we can see the difference in power consumption between various cooling mediums. The lower the temperature to be attained the higher is the power consumption.
- Energy savings in refrigeration needs application of common sense. The first thing to look for is in the process. There may be a stream which is cooled from 50 O C to 25 O C. In this case the stream can first be cooled by cooling water upto say 30 O C and further cooling can be effected by chilled water. Chilled water is costlier than cooling water. There could also be process streams to be cooled and other stream requiring heating. In such cases proces to process heat exchange can reduce chilled water requirements as well as steam. Similarly in an air conditioning application, minimising/ eliminating unwanted loads can bring down energy consumption. Once load reduction options have been explored, we can move to refrigeration plant to try and optimise the system.