7/03/2014

Centrifugal water chillers trane

Centrifugal water chillers trane



chillers trane

INTRODUCTION:

Water chillers are used in a variety of air conditioning and process cooling applications. They are used to make cold water that can be transported throughout a facility using pumps and pipes. This cold water can be passed through the tubes of coils to cool the air in an air conditioning application, or it can provide cooling for a manufacturing or industrial process.
Systems that employ water chillers are commonly called chilled water systems.
There are several types of water chillers. They differ from each other based on the refrigeration cycle or the type of compressor they use.
Absorption water chillers make use of the absorption refrigeration cycle and do not have a mechanical compressor involved in the refrigeration cycle.

period one Components:

Compressor
compressor trane
The centrifugal compressor uses the principle of dynamic compression, which involves converting energy from one form to another, to increase the pressure and temperature of the refrigerant. It converts kinetic energy to static energy.

Impeller
Impeller trane
The core component of a centrifugal compressor is the rotating impeller. The center, or eye, of the impeller is fitted with blades that draw refrigerant vapor into radial passages that are internal to the impeller body.

Centrifugal compressor
Centrifugal compressor
The rotation of the impeller causes the refrigerant vapor to accelerate within the
impeller passages, increasing its velocity and kinetic energy.
The accelerated refrigerant vapor leaves the impeller and enters the diffuser passages. These passages start out small and become larger as the refrigerant travels through them. As the size of the diffuser passages increases, the
velocity, and therefore the kinetic energy, of the refrigerant decreases.
The first law of thermodynamics states that energy is not destroyed—only converted from one form to another. Thus, the refrigerant’s kinetic energy is converted to static energy or static pressure.
Refrigerant, now at a higher pressure, collects in a larger space around the perimeter of the compressor called the volute. The volute also becomes larger as the refrigerant travels through it. Again, as the size of the volute increases, the kinetic energy is converted to static pressure.
Due to its pressure and temperature, the refrigerant leaving the compressor is in a condition that allows its heat to be rejected from the chiller.
 
Energy conversion


Energy conversion
Again, in the passages of the rotating impeller, the refrigerant vapor accelerates, increasing its velocity and kinetic energy. As the area increases in the diffuser passages, the velocity, and therefore the kinetic energy, of the refrigerant decreases. This reduction in kinetic energy is offset by an increase in the refrigerant’s static energy or static pressure. Finally, the high pressure refrigerant collects in the volute around the perimeter of the compressor, where further energy conversion takes place.
 
multistage compressor
multistage compressor
Centrifugal compressors use 1 or more impellers to compress the refrigerant. A multistage compressor uses 2 or 3 impellers to increase the pressure of the refrigerant in steps instead of performing the task within a single impeller.
Compressed refrigerant vapor travels from the outlet of the first-stage compressor impeller to the inlet of the second-stage compressor impeller. After
 
Condenseur
Condenseur

the accelerated refrigerant vapor leaves the last impeller, it collects in the compressor volute and travels on to the condenser.
Condenser
The high-pressure refrigerant vapor is discharged from the compressor into a heat exchanger that acts as a condenser.
In a water-cooled condenser, water is pumped through the tubes of the shell- and-tube heat exchanger while refrigerant vapor fills the shell space surrounding the tube bundle. A baffle inside the condenser helps distribute the refrigerant evenly. As heat transfers from the hot, high-pressure refrigerant vapor to the water, refrigerant condenses on the tube surfaces.
Cooling water flows first through the lower tubes and then through the upper tubes. This produces a nearly constant temperature difference between the downward-moving refrigerant and the tube surfaces, resulting in a uniform heat transfer rate within the tube bundle.
Condensed liquid refrigerant collects in the bottom of the shell and flows through the liquid line to the expansion devices and economizer.

                                                               abo bahaa eddine

3 comments:

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