Main Components of Compressed Air Systems

Compressed air systems consist of following major components: Intake air filters, inter-stage
coolers, after-coolers, air-dryers, moisture drain traps, receivers, piping network, filters,
regulators and lubricators.

Intake Air Filters : Prevent dust from entering a compressor; Dust causes sticking valves,
scoured cylinders, excessive wear etc.
Inter-stage Coolers : Reduce the temperature of the air before it enters the next stage to
reduce the work of compression and increase efficiency. They are normally water-cooled.
After-Coolers: The objective is to remove the moisture in the air by reducing the
temperature in a water-cooled heat exchanger.
Air-dryers: The remaining traces of moisture after after-cooler are removed using air dryers,
as air for instrument and pneumatic equipment has to be relatively free of any moisture. The
moisture is removed by using adsorbents like silica gel /activated carbon, or refrigerant
dryers, or heat of compression dryers.
Moisture Drain Traps: Moisture drain traps are used for removal of moisture in the
compressed air. These traps resemble steam traps. Various types of traps used are manual
drain cocks, timer based / automatic drain valves etc.
Receivers : Air receivers are provided as stora ge and smoothening pulsating air output -
reducing pressure variations from the compressor.

Compressor Plant and its parts

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Flywheel Energy Storage

Flywheel energy storage systems store kinetic energy (i.e. energy produced by motion) by constantly spinning a compact rotor in a low-friction environment. When short-term back-up power is required (i.e. when utility power fluctuates or is lost), the rotor's inertia allows it to continue spinning and the resulting kinetic energy is converted to electricity.

Active Power's CleanSource® Flywheel Technology, as shown below, integrates the function of a motor, flywheel rotor and generator into a single integrated system. The motor, which uses electric current from the utility grid to provide energy to rotate the flywheel, spins constantly to maintain a ready source of kinetic energy. The generator then converts the kinetic energy of the flywheel into electricity. This integration of functionality reduces the cost and increases product efficiency. 

            A flywheel, in essence is a mechanical battery - simply a mass rotating about an axis. Flywheels store energy mechanically in the form of kinetic energy. They take an electrical input to accelerate the rotor up to speed by using the built-in motor, and return the electrical energy by using this same motor as a generator. Flywheels are one of the oldest and most common mechanical devises in existence. They may still prove to serve us as an important component on tomorrow's vehicles and future energy needs. Flywheels are one of the most promising technologies for replacing conventional lead acid batteries as energy storage systems for a variety of applications, including automobiles, economical rural electrification systems, and stand-alone, remote power units commonly used in the telecommunications industry. Recent advances in the mechanical properties of composites has rekindled interest in using the inertia of a spinning wheel to store energy. 

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Vapour Compression Refrigeration Cycle

Vapour compression refrigeration systems are the most commonly used among all refrigeration systems. As the name implies, these systems belong to the general class of vapour cycles, wherein the working fluid (refrigerant) undergoes phase change at least during one process. In a vapour compression refrigeration system, refrigeration is obtained as the refrigerant evaporates at low temperatures. The input to the system is in the form of mechanical energy required to run the compressor. Hence these systems are also called as mechanical refrigeration systems. Vapour compression refrigeration systems are available to suit almost all applications with the refrigeration capacities ranging from few Watts to few megawatts. A wide variety of refrigerants can be used in these systems to suit different applications, capacities etc. The actual vapour compression cycle is based on Evans-Perkins cycle, which is also called as reverse Rankine cycle.

Vapour Compression Refrigeration System

Compression: In this process vapour is drawn in the compressor cylinder during its suction stroke and is isentropically compressed to pressure P2 during its compression stroke. Hence temperature of vapour increases. 

Condensation: The vapours after leaving the compressor enters the condenser where is is condensed to high pressure liquid. cooling water is supplied to remove heat from the vapour.

Expansion: high pressure liquid is now expanded through throttle valve and the liquid at stage 3 is throttled to lower pressure P1 and has a low temperature. After throttling we get vapours at low temperature.

Vapourization: After the throttle valve the wet vapours are passed through the evaporator. The vapour absorbs the heat from the surrounding hence reach the condition 1.

Figure shows the schematic of a standard, saturated, single stage (SSS) vapour compression refrigeration system and the operating cycle on a T s diagram. As shown in the figure the standard single stage, saturated vapour compression refrigeration system consists of the following four processes:

Process 1-2: Isentropic compression of saturated vapour in compressor
Process 2-3: Isobaric heat rejection in condenser
Process 3-4: Isenthalpic expansion of saturated liquid in expansion device
Process 4-1: Isobaric heat extraction in the evaporator

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