Refrigeration
Basic Refrigeration Cycle
Reversed Carnot Cycle
Reversed Carnot Cycle Refrigeration Cycle
Dr. M. Zahurul Haq
Professor Department of Mechanical Engineering Bangladesh University of Engineering & Technology (BUET) Dhaka-1000, Bangladesh zahurul@me.buet.ac.bd http://teacher.buet.ac.bd/zahurul/
ME 415: Refrigeration & Building Mechanical Systems
e720
Coefficient of Performance, COP =
TL QL = Wnet TH − TL
ME 415 (2011) 2 / 14
c Dr. M. Zahurul Haq (BUET)
Refrigeration Cycle Reversed Carnot Cycle
ME 415 (2011)
1 / 14
c Dr. M. Zahurul Haq (BUET)
Refrigeration Cycle Reversed Carnot Cycle
Basic Refrigeration Cycle
Basic Refrigeration Cycle
Wet Compression in Carnot Cycle vs. Dry Compression
Expansion Process in Carnot Cycle
Carnot cycle demands that the expansion take place isentropically and that the resulting work be used to help drive the compressor. Practical difficulties, however, militate against the expansion engine: the possible work that can be derived from the engine is small fraction that must be supplied to the compressor. practical problems such as lubrication intrude when a fluid of two phases drives the engine. the economics of the power recovery have in past not justified the cost of the expansion engine. A throttling device, such as a valve or other restriction, is almost universally used for this purpose.
During compression, droplets present in liquid are vaporised by the internal heat transfer process which requires finite time. High-speed compressors are susceptible to damage by liquid because of the short time available. In wet compression, the droplets of the liquids may wash the lubricating oil from the walls of the cylinder, accelerating wear. Dry compression takes place with no droplets and is preferable. Liquid refrigerants may be trapped in the head of reciprocating compressor by the rising piston, possibly damaging the valves or the cylinder head.
c Dr. M. Zahurul Haq (BUET)
Refrigeration
Reversed Carnot Cycle
Reversed Carnot Cycle Refrigeration Cycle
Dr. M. Zahurul Haq
Professor Department of Mechanical Engineering Bangladesh University of Engineering & Technology (BUET) Dhaka-1000, Bangladesh zahurul@me.buet.ac.bd http://teacher.buet.ac.bd/zahurul/
ME 415: Refrigeration & Building Mechanical Systems
e720
Coefficient of Performance, COP =
TL QL = Wnet TH − TL
ME 415 (2011) 2 / 14
c Dr. M. Zahurul Haq (BUET)
Refrigeration Cycle Reversed Carnot Cycle
ME 415 (2011)
1 / 14
c Dr. M. Zahurul Haq (BUET)
Refrigeration Cycle Reversed Carnot Cycle
Basic Refrigeration Cycle
Basic Refrigeration Cycle
Wet Compression in Carnot Cycle vs. Dry Compression
Expansion Process in Carnot Cycle
Carnot cycle demands that the expansion take place isentropically and that the resulting work be used to help drive the compressor. Practical difficulties, however, militate against the expansion engine: the possible work that can be derived from the engine is small fraction that must be supplied to the compressor. practical problems such as lubrication intrude when a fluid of two phases drives the engine. the economics of the power recovery have in past not justified the cost of the expansion engine. A throttling device, such as a valve or other restriction, is almost universally used for this purpose.
During compression, droplets present in liquid are vaporised by the internal heat transfer process which requires finite time. High-speed compressors are susceptible to damage by liquid because of the short time available. In wet compression, the droplets of the liquids may wash the lubricating oil from the walls of the cylinder, accelerating wear. Dry compression takes place with no droplets and is preferable. Liquid refrigerants may be trapped in the head of reciprocating compressor by the rising piston, possibly damaging the valves or the cylinder head.
c Dr. M. Zahurul Haq (BUET)
Refrigeration