Unit 5 Power Absorbing Devices Power Absorbing devices

Unit- 5 Power Absorbing Devices

• • Power Absorbing devices uses work energy from outside source to increase the energy of working fluid during a cycle. e. g. pumps, compressors, blowers, fans, refrigerators, Air conditioners etc. 1 Air Compressors A machine providing gas at high pressure is called compressor and work must be done upon the gas by external agency. • An air compressor takes in atmospheric air, compresses it and delivers the high pressure air to the storage vessel. • Since the process of compressing air requires that work should be done upon it. Thus, compressor is driven by a prime mover. • In a reciprocating compressor, a volume of gas is drawn into a cylinder, it is trapped and compressed by piston and then discharged into the discharge line. •

Classification of compressors Reciprocating Compressor i) Single Acting compressor ii) Double Acting Compressor Rotary Compressors Reciprocating Compressor • In single acting compressor suction and compression of air takes place only one side of piston. It will have one discharge per revolution of crankshaft. • In double acting compressor suction and compression of air takes place both sides of piston. It will have two discharge per revolution of crankshaft. • Pressure Ratio: It is ratio of discharge or outlet pressure to intake or suction pressure. • Free Air Delivered (FAD ): It is actual volume of surrounding air which is sucked by compressor and delivered at discharge pressure. It is given as m 3/min.

Single Acting Compressor • Working • Suction Stroke • Fig shows the position of piston when it is moving downwards. Delivery valve is closed. The compressed air in clearance space of previous stroke expands. • When pressure inside cylinder falls below atmospheric pressure , the inlet valve opens. The atmospheric air is sucked inside cylinder up to the end of its suction stroke. • Compression and Delivery stroke • Fig shows the position of piston when it is moving upwards. The air sucked inside the cylinder during suction stroke is compressed due to positive displacement of the piston. When pressure becomes higher than atmospheric pressure , the inlet valve closes.

• In case of double acting reciprocating air compressor , the processes are carried out in similar manner from both sides of piston. Applications- Spray Painting, Refrigeration and Air conditioning Industry , Mining Machinery, In Blast furnace To operate pneumatic tools like drill, riveting machine etc.

Pump • Pump is defined as a device which transfers the input mechanical energy of a motor or an engine into hydraulic energy of a fluid. • So normal duty of pump is to lift liquid to required height against the force of gravity and to overcome the fluid resistance to flow liquid through pipe and pump itself. • In order to carry out above duties by pump , it has to provide energy. Classification of Pumps • Positive Displacement Pumps • i) Reciprocating Pump • ii)Centrifugal Pump

Reciprocating Pump (Single Acting)- Applications: Used as a feed water pump in boiler operation , pressure washing in service stations , fire fighting applications.

Reciprocating Pump (Double Acting)-

Centrifugal Pump- • Applications- • Agriculture and irrigation works. • Municipal water works and drainage system. • Hydraulic control system. • Oil pumping. • Transfer of raw materials. • Fire fighting

Refrigeration & Air Conditioning • Refrigeration is the process of achieving and maintaining a temperature below that of the surroundings, the aim being to cool some product or space to the required temperature. • One of the most important applications of refrigeration has been the preservation of perishable food products by storing them at low temperatures. How does it work? 10

Tons of Refrigeration • The rating of refrigerating machine is given by a standard unit of refrigeration called ton of refrigeration (TR). • One Ton of refrigeration means capacity to freeze 1 ton of water from and at 00 C in 24 hours. Types of Refrigeration • Vapour Compression Refrigeration (VCR): uses mechanical energy • Vapour Absorption Refrigeration (VAR): uses thermal energy 11

Vapour Compression Refrigeration – • Vapour compression refrigeration cycle is commonly used in refrigeration and air conditioning both for industrial and domestic appliances. • In 12 this system the working substance is a refrigerant like NH 3 , R-11, R-12, R-22.

Refrigerator • This is application of food preservation at the end user level. A refrigerator is an insulated box in which lower temperature is maintained to facilitate medium term storage of food. • Components of Refrigeration System- • • 13 Evaporator Compressor Condenser Expansion device

Air Conditioning • Air conditioning is defined as the control of humidity , air movement and purity of an air in an enclosed space. • The engineer aims to ensure comfort for most people found from statistical survey. Most people (90%) are comfortable when air temperature between 18 and 220 C and % saturation is between 40 and 65%. • There are two types of air conditioners i) Window air conditioner ii) Split air conditioner 14

i) Window air conditioner • It is cubical unit , a complete conditioning system in itself ; it requires a window or such space , where it can be installed with its face inside the room and exterior part outside the room , as it discharges heat outside. • As compressor and evaporator , both are in one unit , so its cooling capacity is limited , this makes it suitable only for small places. • The components • Compressor • Condenser • Evaporator • Expansion Device • Motor and Blower 15

Window Air Conditioner 16

Split Air Conditioner 17

Applications of Refrigeration and Air Conditioning systems- 18