Introduction:
Chiller is a equipment which is used for the refrigeration system. Refrigeration
is defined as the process of extracting from a low temperature medium and
transferring it to a high temperature heat sink. Refrigeration maintains the
temperature of the heat source below that of its surroundings while transferring
the extracted heat to a heat sink.
Purpose of the chiller:
i) Chiller is used for producing humid air. This humid air is supplied in
the weaving room, in the inspection room.
ii) Chiller is also needed for the refrigeration system.
Main parts of the chiller:
i)Evaporator
ii) Absorber
iii) Heat exchanger
iv) High temperature generator
V) Low temperature generator and condenser
Working principal of the chiller:
At the chiller the steam is used from the boiler. Which is controlled with
the help of the PLC (programmable logic control) and there is a IP converter
which converts the order of the PLC (programmable logic control). There is
a cooling tower at which the hot water from the chiller is cooled at normal
temperature. Here the steam inlet temperature 174.5 0C and pressure 8 kg/cm2
which separates the distilled water. Here three types of pumps are used,
i) Refrigeration pump
ii) Absorbent pump
iii) Purge pump
Here cooling water inlet temperature 29.4 0C and the cooling water
Lower shell pressure = 6.2 mm Hg
Upper shell pressure = 4.8 mm Hg
High temperature generator pressure = 671.5 mm Hg
Dilute solution concentration = 58.6 %
Medium solution concentration = 61.0 %
Strong solution concentration = 63.4 %
The evaporator consists of a tube bundle, an outer shell, distribution trays, and a refrigerant pan. The chilled water flows inside the tubes. A refrigerant pump circulates the refrigerant from the refrigerant pan into the distribution trays. From the trays the refrigerant falls on the evaporator tubes. The shell pressure is very low (~6mmHg). At this pressure the refrigerant evaporates at a low temperature (~3.70c) and extracts latent heat of evaporation from the water being circulated through the evaporator tubes. Thus the water being circulated through the tubes becomes chilled.
The absorber consists of a tube bundle, an outer shell (common with the evaporator), distribution trays, and an absorbent collection sump. Concentrated absorbent solution (~63.4%) from low temperature generator is fed into the distribution trays. This solution falls on the absorber tubes. Concentrated absorbent has an affinity to water. Hence the vaporized refrigerant from the evaporator section is absorbed. Due to absorption the vacuum in the shell is maintained at a low pressure and ensure the correct chilled water temperature. The concentrated absorbent becomes diluted. During this dilution the “heat of dilution” is generated. The heat is removed by the cooling water being circulated in the absorber tubes. The diluted absorbent (~5.9%) collects in the bottom of the shell.