Vapour Absorption Refrigeration Systems: (VARS) belong to the class of vapor cycles similar to vapor compression refrigeration systems. However, unlike vapor compression refrigeration systems, the required input to absorption systems is in the form of heat. Hence these systems are also called heat operated or thermal energy-driven systems. Since conventional absorption systems use liquids for the absorption of refrigerant, these are also called as wet absorption systems. Since these systems run on low-grade thermal energy, they are preferred when low-grade energy such as waste heat or solar energy is available. As absorption systems use natural refrigerants such as water or ammonia they are environment-friendly. In the absorption refrigeration system, the refrigeration effect is produced mainly by the use of energy as heat. In such a
system, the refrigerant is usually dissolved in a liquid. A concentrated solution of ammonia is boiled in a vapor generator producing ammonia vapor at high pressure. The high-pressure ammonia vapor is fed to a condenser where it is condensed to liquid ammonia by rejecting energy as heat to the surroundings. Then, the liquid ammonia is throttled through a valve to low pressure. During throttling, ammonia is partially vaporized and its temperature decreases.
This low-temperature ammonia is fed to an evaporator where it is vaporized removing energy from the evaporator. Then this low-pressure ammonia vapor is absorbed in the weak solution of ammonia. The resulting strong ammonia solution is pumped back to the vapor generator and the cycle is completed. The COP of the absorption system can be evaluated by considering it as a combination of a heat pump and a heat engine
CARE AND MAINTENANCE OF REFRIGERATING UNITS
Regular cleaning and maintenance not only makes your equipment work more efficiently, but it also helps it last longer. When parts are worn and dirty, the unit runs more frequently causing more wear and tear on the parts. Eventually, the unit breaks down for good long before it should have.
Preventing these issues is simpler than you think. Call in a qualified refrigeration service company at least twice a year and up to once a month, depending on the load and usage of your equipment, to do the following tasks:
- Clean evaporator and condenser coils
- Check lines for condensation
- Clean fan blades and inspect the fan motor
- Check integrity of insulation
- Check for air leaks through cracks, holes, and worn parts like gaskets and seals
- Lubricate door hinges and handles
- Check for loose electrical connections
- Clear drain lines of debris
- Check temperature and defrost settings and calibrate thermometers
- Check filters on ice makers
- Thoroughly clean all ice maker components
TYPES OF REFRIGERATING UNITS IN HOTEL INDUSTRY
The usual categories of refrigerating units employed in the hotel industry are:
- Reach – in Units
- Counter – top or table – top Units
- Walk – in Units
- Special – purpose Units
Each of the above-mentioned units can have both cooler and freezer sections in them. Some refrigerators are now divided into four zones to store different types of food. They are as follows:
Subzero (up to –18 degree Celsius) – Freezer Section
0 degree Celsius – Meat preservation Section
5 degree Celsius – Refrigerator
10 degree Celsius – Vegetables Section
Reach – in refrigerators
Coolers & Freezers – Capacities of such units are usually expressed in terms of the internal space volume (cubic metre) or in mass (Kg) of material being stored in it.
Typical interior temperature range for cooler should be 4.4 degree Celsius to 7 degree Celsius and for a freezer should be -15 degree Celsius to -23 degree Celsius.
Counter top units
Small counter top refrigerators are frequently used to facilitate service.
They are usually coolers and have features similar to those of reach-in coolers but of much smaller size usually up to a size of 100 litres only.
Walk – in refrigeration system
As the name suggests, food operators can directly move into such units.
They are much bigger in size and height than walk – in refrigerators.
A typical size would be 4 X 5 X 3 m, or even more, or as lass as having a floor area of 2 sq. m..
They are normally custom built.
Special purpose units
Ice Cream Conservator and frozen food conservator: They are usually “well type” and open vertically through a lid. This minimizes heat loss as cool and heavy air inside cannot escape upward. They are usually maintained at temperatures between -23 to -18 degree Celsius.
Wet Fish Cabinets: They contain deep galvanized drawers in which fish can be embedded in ice. They keep moist storage conditions necessary for maintaining the quality of fish. They are usually maintained at temperatures between 0 to -2 degree Celsius.
Special purpose units
Display Cabinets: In many hotels, there is a refrigerated display cabinet kept in the dinning for the customers to choose varieties of meats for grilling. They are also used to display bakery products and desserts.
Bottle Coolers: They are used in dinning and are usually in bars. They are constructed in two ways. One is open refrigerated through type and the other is glass front cabinet type with hinged doors or sliding doors.
Ice makers: Modern ice making machines need only to be connected to a cold water supply line. Water flows over a refrigerated plate and gets converted into a slab of ice. This slab of ice passes over a wire net which is electrically heated and the slab melts along the wire mesh and falls through the square holes as separate small cubes of ice.
Desirable properties of refrigerants
- It should be non poisonous and non irritant.
- It should be non flammable.
- It should be chemically stable.
- It should be non corrosive and should not react with the parts / components of the system.
- It should have no objectionable odour or smell.
- It should be easily and reliably detectable in case of leakage.
- Its LH of vapourisation should be high so that quantity of high refrigerant can be minimized.
- Its cost should be low.
- It should be easily available.