Chillers and their types - An insight on Air-cooled and Water-cooled Chillers

 

Chillers and their types

In this post we are going to see about one of the most widely used Air conditioning Systems. They are "Chillers".

                Chiller is that type of machine which produces chilled water with the help of refrigeration cycle. There are mainly two types of Chillers. Air-cooled Chillers and Water-cooled Chillers. Now we will see about these two chillers. Air-cooled Chillers v/s Water-cooled Chillers.

        A separating element of the sorts of chillers is the strategy used to gather the refrigerant as it leaves the blower. The two strategies include utilizing either air-cooled or water-cooled condensers. Air-cooled condensers utilize encompassing air as the gathering medium and utilize a fan to move the air over the loop. For a given surface and airflow rate, the capacity of an air-cooled condenser varies with the refrigerant condensing temperature, which is the function of the entering dry-bulb temperature. 

        A typical air-cooled condensing temperature based on 95°F dry-bulb ambient air has the following data:

        Design Air Inlet Temperature =  95c

        Air Rise =  15°F

        Difference between Condensing temperature and Leaving air  = 15°F

        Refrigerant Condensing Temperature = 125°F

Water-cooled condensers utilize water as the gathering medium and utilize a siphon to flow the water through the condenser and out to a cooling tower that dismisses the hotness to the environment.

Operating cost is one of the primary factors when deciding between air-cooled and water-cooled chillers. Air-cooled chiller frameworks normally have a lower first and upkeep cost, since they don't need a cooling tower, condenser water siphons, and related condenser water synthetic treatment. Operating costs however, generally favors water-cooled chillers. This is because, water-cooled chillers can take advantage of lower condensing temperatures than air-cooled chillers. 

        Some of the advantages of air cooled chillers are, Lower installation costs, Quicker Availability, No cooling tower or condenser pumps required, Less maintenance, No Mechanical Room required. When we compare this to water-cooled chillers, some of the advantages of water-cooled chillers are, Higher efficiency, Custom Selections in larger sizes, Large tonnage capabilities, Indoor Chiller Location and Longer Life. etc.

Next, we will see about Air-cooled Chillers.

Air Cooled Chillers :

            In this chiller, the condenser cooling is done by air. So, condenser fan is used for condenser cooling on top side of the unit. Fin type condenser is used in air-cooled chillers and fins are made by aluminum. Quantity of fins is 14 numbers in one inch. Some condenser coil fins are in Sine wave form. It means the condenser heat rejection factor will be high. In condenser coil, copper tube is used and the tube size depends on the unit capacity. Air-cooled chillers are normal in present day frameworks and have been filling in prevalence since the 1980's. Nearly doubling, in the last 10 years. Today, air-cooled chillers are applied on little to enormous business occupations, and can be utilized in products to shape frameworks arriving at a few thousand tons of introduced limit. The ubiquity is principally because of the comprehensive idea of air-cooled chillers and the decrease of expenses related with taking out cooling tower.

            On certain models, even the hydronic extras, for example, the siphon and extension tank might be incorporated, gathered and tried from the production line, prepared to start tasks. 

Basic Refrigeration Cycle for Air-cooled Chillers:

            The refrigeration pattern of an air-cooled chiller incorporates two significant cycles. The dissipation of the fluid refrigerant in the evaporator which assimilates hotness and brings down the temperature of the chilled water framework. The condensation of the refrigerant vapor in the air-cooled condenser and rejection of heat to the atmosphere.In the air-cooled chiller refrigeration cycle, water enters the evaporator, otherwise called the cooler and is cooled by the colder refrigerant moving through the other circuit inside the evaporator. The chilled water is siphoned from the chiller to the structure curls to give cooling. In the evaporator, the chilled water cools the building or process load, and the cycle is completed when the warmer water flows back to the evaporator. A mixture of cold liquid refrigerant and flash gas passes through the evaporator circuit opposite to the water to be chilled. The refrigerant in the evaporator absorbs heat from the warmer return water, evaporates to a vapor and finally exits the evaporator as a super-heated vapor. The super-heated refrigerant vapor then enters the suction inlet of the compressor. In the compressor, the refrigerant is compressed raising its pressure and temperature. 

            High tension and temperature refrigerant gas leaves the blower, goes through the release line and enters the condenser. While, in the air-cooled condenser coil, the hot gas condenses to liquid inside the tubes as it gives up heat to cooler. Outdoor air being drawn across the condenser loop by the condenser fans. The refrigerant is on the shell side of some evaporator plans, and on the cylinder side of others. When the refrigerant is on the tube side, the evaporator is called a DX evaporator, when on the shell side, it is a flooded cooler.

        The consolidated fluid refrigerant then leaves the condenser and enters the development gadget. As the refrigerant goes through the extension gadget, its tension and temperature is diminished to the guide that a portion of the fluid glimmers toward fume. The expansion device controls the amount of flashing, in order to maintain a certain super-heat, to ensure no liquid droplets enter the compressor suction. Subsequent to leaving the extension gadget, the refrigerant enters the evaporator and the cycle is rehashed.

Next, we will see about Water-cooled Chillers.

Water Cooled Chillers :

            In this type of chiller, condenser cooling is done by cold water. So, this type of chiller is called water-cooled chiller. Cooling tower is essential for condenser water cooling. Water-cooled chillers range in size from little 20-ton limit models that can fit in a lift, to a few thousand ton models that cool the world's biggest offices, for example, airports, shopping centers, skyscrapers and other facilities. Screw and Centrifugal blower water-cooled chillers will quite often be the most famous plans for bigger business applications. While scroll and responding blower chillers are utilized on the more modest ones. Next, we will examine the major components used in water-cooled chillers such as evaporators, condensers, compressors, and metering devices etc.

Basic Refrigeration Cycle for Water Cooled Chillers :

            Refrigeration cycle for comfort cooling applications. In the evaporator of a water-cooled chiller, liquid refrigerant at approximately 42°F takes on heat from building return water, who's entering temperature maybe represented at 54°F. Here, we will make sense of the refrigeration cycle utilizing parts from an outward chiller, since that sort of chiller is water-cooled chiller.The following temperatures are typical of the standard refrigeration cycle from the building return water, who's entering temperature maybe represented at 54°F, flowing through the evaporator and changes to a vapor. The refrigerant fume is brought into the blower and its temperature and tension are raised. The compressor provides compression to the gas required in condenser. The gas itself discharged into the condenser where it condenses on tubes through which water flows typically at 85°F.  From the cooling tower, this is the entering condenser water. The consolidated beads of fluid refrigerant then tumble to the lower part of the condenser, course through a strain decreasing gadget like a float valve or a hole and furthermore, return to the lower part of the cooler, where the cycle rehashes the same thing.

            So, from the two types of chillers, we discover that the basic components for chillers are same. Except for the cooling tower and condenser pumps in case of water-cooled chillers.