The chiller is a kind of water cooling equipment, which can provide constant temperature, constant current and constant pressure. How does the refrigeration cycle using components from a centrifugal chiller of water chiller?
The following temperatures are typical of the standard 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 (whose entering temperature may be represented at 54°F) flowing through the evaporator, and changes to a vapor. The refrigerant vapor is drawn into the compressor and its temperature and pressure are elevated.
The compressor provides the work necessary to compress the gas to a temperature and pressure required by the condenser, typically 97°F. The gas is then discharged into the condenser where it condenses on tubes through which water flows, typically at 85°F. This is the entering condenser water from the cooling tower. The condensed droplets of liquid refrigerant then fall to the bottom of the condenser, flow through a pressure reducing device such as a float valve or an orifice, and return to the bottom of the cooler where the process repeats itself. But high pressure of chiller become a problem that we need to solve.
The cycle can be shown on a pressure enthalpy(p-h) diagram.Pressure is the force exerted per unit area, while enthalpy is the total heat content expressed in Btu per pound of the substance. When the compressor is close-coupled to the evaporator,there is negligible pressure loss in the suction line, and gas enters the compressor at approximately the saturated conditions that exist in the evaporator. lf we follow the steps shown, you can see that from A to 1 is the refrigeration effect. In this step, building heat from the chilled water is absorbed by the refrigerant,and the refrigerant transitions from a liquid to refrigerant transitions from a liquid to a saturated vapor, at Step 1. From Step 1 to 2 is the compression stage. This stage raises the temperature and pressure of the saturated refrigerant vapor to the saturated condensing temperature, so that heat can be rejected to the condensing fluid. This compression is also called the “lift” of the compressor.