Free cooling on RTAF Chiller. Integrated option

Transcription

1 Free cooling on RTAF Chiller Integrated option

2 Water based free cooling principle. Use full aluminum (car radiator based) flat channel dry cooler exchangers. Modulate 3 way to reach required free cooling capacity. Need low air pressure drop coil to avoid upgrade of fans. Oil Sep. Evaporator 2

3 Technical proposition Alternative 1 : no change on condenser fan = lower EER, but no fan impact on cost, almost no impact on sound level 1 2 Total Free cooling Direct free cooling version (With glycol on customer loop) Total Free cooling Glycol Free version (With water on customer loop) 3 4 Partial Free cooling Direct free cooling version (With glycol on customer loop) Partial Free cooling Glycol Free version (With water on customer loop) Trane FreeCool External drycooler 3 5 External Standard RTAF With or without glycol on customer loop

4 Flow chart - Free cooling Direct free cooling version (With glycol on customer loop) 1 3 (Vent) Tchill OUT (Vent) Tevap IN Tchill IN Evaporator Optionnal Pump package Bypass 2way Modulating 2way (Drain) 4

5 Flow chart - Free cooling Glycol Free version (With water on customer loop) 2 4 (Vent) Tchill OUT Tchill IN (Vent) Evaporator Optionnal Pump package Tevap IN Water/glycol BPHE Tfc OUT Tfc IN Exp.tank Bypass 2way Modulating 2way (Drain) (Drain) Circulating pump 5

6 Free cooling enabling condition Condition to get free cooling active : Unit is in active cooling mode. Outdoor temperature shall be low enough. Cf. diagram here below Free cooling enabled Proposed default value FC Offset = 3K (Min 0.5 K, max 15 K) FC Hysteresis = 1K (Min 0.5 K, max 3 K) FC Offset FC Hysteresis Free cooling disabled Water Cooling setpoint Outdoor air temperature FC setpoint = Active chilled water cooling setpoint FC_offset The free cooling function is enabled when outdoor air temperature is below (Active chilled water cooling set point minus FC_offset). An hysteresis shall be applied to avoid short cycling of FC enable logic. FC offset is the parameter adjusted by user to make free cooling active. Free cooling becomes the 1 st stage of cooling, whatever the compressor sequence selected: If free cooling is enabled while compressor is running, then unload command of the algorithm shall apply to running compressor. In case of load command, then free cooling capacity shall be increase 6

7 Free cooling capacity modulation 3 3 Bypass 2way (ON-OFF) 1 2 Modulating 2way Bypass 2way (ON-OFF) 1 2 Modulating 2way FC pump Bypass Valve 100% FC disabled FC 1 st step FC 2 nd step 100% 0% for TFC 100% 30% for PFC 0% for TFC 30% for PFC FC CLOSE 0% 100% (modulating) 100% Condenser fan airflow Follow compressor fan sequence 0% or follow compressor fan sequence if compressor are still running 0% 100% or follow compressor fan sequence if compressor are still running FC pump OFF ON ON 7

8 Freeze protection (only for Glycol free version) If Free cooling is active, the pump is ON. At start up or when heat transfer over the drycooler increases, the glycol stored in the system could be very cold, resulting in freezing risk on the BPHE. To avoid this, the strategy is to run the pump with recirculation of the glycol in a short loop (dotted line arrow). The freeze protection mode is targeted to restore positive temperature at BPHE glycol inlet. The heat from return chilled water and from the pump heat loss will try to maintain the BPHE glycol temperature above 0 C. Difficulty here is to have quick enough system response to avoid partial freezing into the BPHE Condition to have freeze protection active: Outdoor air temperature <3 C Free cooling is active : Chiller water flow is present & there is a call for cooling. If Tfc OUT is < chilled water freeze protection setpoint and FC pump is ON then we are in FC freeze protection mode FC Freeze protection limiting mode : Reduce Free cooling capacity to keep TfcOUT > chilled water freeze protection setpoint from 100% to 0% (following accelarated unload sequence). If Tfc IN < chilled water freeze protection then Lockout free cooling operation and report alarm. Auto reset when Outdoor temperature is >3 C. To dry cooler Tchill OUT Evaporator Tevap IN Water/glycol BPHE Tfc OUT FC Modulating 2way Tchill IN Optionnal Pump package Tfc IN FC Bypass 2way 8 (Drain) (Drain) Circulating pump

9 Schedule 2015 Q1 Q2 Q3 Q4 2016Q1 Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Jan. Feb. Mar. G1 G2 G3 G4 G2 G4 IRPDP gates reviews Jul-09 Mockup build & Test Program key steps Validation unit Ph1 build & Test Validation unit Ph2 build & Test Industrialization Ph1 Industrialization Ph2 Literature update Ph1 Literature update Ph2 Phase 1 = All RTAF sizes Direct free cooling version - Partial and Total Free cooling Phase 1 : All RTAF sizes Glycol FREE version - Partial and Total Free cooling Pre-annoucement Topps Release Topps Release 1 ST SHIP 1 ST SHIP 9 9

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