NOMENCLATURE - Dunham-Bush Americas

1 AFHX Series Air cooled Screw Flooded Chillers Cooling Capacity: 208 to 557 Tons (732 to 1959 kW). 60Hz R134a Products that people who care TABLE OF CONTENT. PAGE NO. NOMENCLATURE .. 2. Advantages of Flooded 3. Unit Features .. 5. Operating Benefits .. 8. Typical Sequence of Operation .. 9. Application Data .. 10. Physical Specifications .. 11. Performance Data .. 12. Dimensional Data .. 13. Dimensional Floor Loading Diagram .. 17. Condenser Fan .. 18. Sound Pressure Level at 10M- Free Field .. 18. Pressure Drop .. 19. Electrical Data .. 19. Typical Wiring Schematic .. 20. NOMENCLATURE . A F HX 115 T - 5 S R- HR. HR = Heat Recovery Air cooled chiller LN = Low Noise Blank = R22.

2 R = R134a Flooded Evaporator S = Standard Q = Special Horizontal Screw Compressor 5 = 50Hz 6 = 60Hz Nominal Tons T = Optional Two Compressors Blank = Standard -2- ADVANTAGES OF FLOODED chiller . In a flooded evaporator the refrigerant input curve over the same conditions. It can surrounds the tubes in the shell and the water be noted that the same compressor when to be cooled flows through the tubes. The level operating with a flooded evaporator will of liquid refrigerant in the shell is maintained by generate approximately 8% more cooling the combined action of an electronic level capacity while kw input increases negligibly controller and a mod-motor actuated ball valve by about Therefore, the same which modulates the subcooled liquid compressor when coupled to a flooded refrigerant into the evaporator.

3 This ensures evaporator will typically achieved higher that all the evaporator tubes are completely cooling capacity performance with immersed in the liquid refrigerant for better heat correspondingly higher Energy Efficiency transfer efficiency. Ratio (EER) (Btu/watt) or lower kw/Ton. For a Direct Expansion (DX) evaporator the refrigerant is expanded into the tubes while the FIGURE 1. chilled water is circulated through the shell. Thermostatic expansion valve is used to throttle the refrigerant in maintaining constant superheat of suction gas to the compressor. The following are the advantages of using flooded chiller : 1. Higher Capacity and Higher EER.

4 Achievable with the Same Compressor The flooded evaporator with all the copper tubes immersed in the boiling liquid refrigerant enables a small approach temperature between the boiling liquid refrigerant temperature in the shell and the outlet chilled water temperature in the evaporator tubes to be achieved. This approach temperature or temperature difference between the evaporating temperature of the boiling liquid refrigerant and the chilled water outlet temperature, for a flooded evaporator, is typically less than 3 F. On the contrary, for a DX or Direct Expansion Evaporator, the typical approach temperature is between 8 F to 10 F. This simply means that the same compressor in a flooded evaporator system will operate at a A DX evaporator uses TXV throttling to higher saturated evaporating temperature maintain about 10 to 15 F suction superheat when compared to the same compressor in to prevent liquid flood back to the a DX-Evaporator system, when outlet chilled compressor.

5 In a flooded evaporator, the water temperatures in both cases are set at refrigerant boils off in the shell and gas can the same temperature. be sucked out from the top of evaporator Figure 1 shows the typical screw back to compressor. The suction superheat compressor capacity performance curve at a is usually about 2 to 3 F. Reduction in particular condensing temperature over suction superheat will further increase the saturated evaporating temperature of capacity performance of the compressor. between 30 F to 50 F, and the typical power -3- ADVANTAGES OF FLOODED chiller . DX evaporators are typically designed with in response to changes in building demand.

6 Higher tube velocities to ensure proper oil and maintains precise ( 1/2 F) preset outlet return to compressor both at full load and at chilled water temperatures even at very low reduced load. This will contribute to higher load conditions; whereas most of Dunham- refrigerant pressure drop through the Bush's competitors, in screw chillers, still evaporator. On the contrary, there is very utilizes the conventional centrifugal chiller . little shell side pressure losses for a flooded method of using orifice plates to modulate evaporator. Therefore, lower suction refrigerant feed to the evaporator; and as pressure drop in the flooded design will such their machines do not function impose less capacity penalty on the efficiently at low-load conditions and can compressor and this will further enable the encounter oil return problem!

7 Compressor in a flooded evaporator to generate more capacity than one with a DX. 4. Cleanable Evaporator Evaporator. For a single pass evaporator, the end plates at both ends of the water boxes (2 pass only 2. Better Part Load Performance at return end) can be removed easily without The Dunham-Bush Air cooled Flooded dismantling the chilled water piping chiller with its sophisticated advanced connections, for inspection and for controller and patented oil management mechanical tubes cleaning with brushes or system has all evaporator tubes completely auto-brush. This will enable low tube fouling immersed in the boiling liquid refrigerant to factor in the evaporator to be ensured, thus achieve superior heat transfer efficiency maintaining system efficiency.

8 While ensuring adequate oil return to the compressor(s). This ensures superior full- 5. Lower water Side Pressure Drop load efficiency and even better part-load In a DX evaporator, the water flows efficiency as the full heat transfer surface transversely over the outside of the tubes. areas of the evaporator tubes are utilized The water flow is guided with vertical baffles. even at part-load conditions. On the This will have a higher-pressure drop as contrary, in the Direct Expansion compared with the water flow in the tubes of Evaporator, because of the need to maintain a flooded evaporator. In other words, the adequate refrigerant gas velocities in the equivalent flooded chiller will require smaller evaporator tubes for proper oil return, it is water pump to operate at lower power typical for certain bundle of evaporator tubes consumption.

9 To be blocked or baffled off at part-load conditions. Thus not utilizing the full heat transfer surface areas of the evaporator 6. Commonly Used In Large Tonnage Chillers Where Efficiency Is Critical tubes and therefore have a lower efficiency when compared with a flooded evaporator As a general rule, DX-evaporator are chiller at part-load conditions. typically used in small and medium tonnage chillers where efficiency is not important and the low initial cost is the main consideration! 3. Excellent Capacity Modulation in However, with increasing energy cost and Response to Building Loads the drive to reduce global warming, Dunham-Bush utilizes its state-of-the-art flooded evaporator chillers will advanced controller in combination increasingly become more popular not with the electronic level controller and only in the large tonnage but also in the mod-motor actuated ball valve to small and medium tonnage chillers.

10 Ensure instantaneous and precise feeding Dunham-Bush , again, leads the industry of liquid refrigerant to the flooded evaporator in this respect! -4- UNIT FEATURES. Semi-Graphic Display panel connected with controller through telephone cable. The terminal allows carrying out all program operations. The user terminal allows displaying the unit working conditions, compressor run times, alarm history and modifying the parameters. The display also has an automatically self-test of the controller on system start-up. Multiple messages will be displayed by automatically scrolling from each message to the next. All of these messages are spelled out in English language on the display terminal.