Carrier AquaEdge 19XR series Start-up, Operation And Maintenance Instructions Manual

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Carrier AquaEdge 19XR series Start-up, Operation And Maintenance Instructions Manual Manual pdf 10 page image

10REFRIGERATION CYCLEThe compressor continuously draws refrigerant vapor fromthe cooler at a rate set by the amount of guide vane opening. Asthe compressor suction reduces the pressure in the cooler, theremaining refrigerant boils at a fairly low temperature (typical-ly 38 to 42 F [3 to 6 C]). The energy required for boiling is ob-tained from the water flowing through the cooler tubes. Withheat energy removed, the water becomes cold enough to use inan air conditioning circuit or for process liquid cooling.After taking heat from the water, the refrigerant vapor iscompressed. Compression adds still more heat energy, and therefrigerant is quite warm (typically 98 to 102 F [37 to 40 C])when it is discharged from the compressor into the condenser.Relatively cool (typically 65 to 90 F [18 to 32 C]) waterflowing into the condenser tubes removes heat from the refrig-erant and the vapor condenses to liquid.The liquid refrigerant passes through orifices into theFLASC (Flash Subcooler) chamber (Fig. 4). Since the FLASCchamber is at a lower pressure, part of the liquid refrigerantflashes to vapor, thereby cooling the remaining liquid. TheFLASC vapor is recondensed on the tubes which are cooled byentering condenser water. The liquid drains into a float cham-ber between the FLASC chamber and cooler. Here the Accu-Meter™ float valve forms a liquid seal to keep FLASCchamber vapor from entering the cooler. When liquid refriger-ant passes through the valve, some of it flashes to vapor in thereduced pressure on the cooler side. In flashing, it removes heatfrom the remaining liquid. The refrigerant is now at a tempera-ture and pressure at which the cycle began. Refrigerant fromthe condenser also cools the oil and optional variable speeddrive.The refrigeration cycle for a 19XR,XRV chiller with two-stage compressor is similar to the one described above, withthe following exception: Liquid refrigerant from the condenserFLASC chamber linear float valve flows into an economizer atintermediate pressure (see Fig. 5). As liquid enters the cham-ber, due to the lower pressure in the economizer, some liquidflashes into a vapor and cools the remaining liquid. The sepa-rated vapor flows to the second stage of the compressor forgreater cycle efficiency. A damper valve located on the econo-mizer line to the compressor acts as a pressure regulating de-vice to stabilize low load, low condensing pressure operatingconditions. The damper will back up gas flow and thereby rais-es the economizer pressure to permit proper refrigerant flowthrough the economizer valve during those conditions. Thedamper also is closed during start-up conditions to allow thesecond stage impeller to start unloaded.The subcooled liquid remaining in the economizer flowsthrough a float valve and then into the cooler.Fig. 4 — Refrigeration Cycle — 19XR,XRV Single-Stage Compressora19-1550tf