Application of FGB Concept in Reversible Cooling & AC Systems 45th KGH Congress, Belgrade 3-5 Dec 2014 Nemanja Dzinic University of Illinois/University of Belgrade MPG-KGH Belgrade , CTS USA Pega Hrnjak Co-Director ACRC, Res. Professor, University of Illinois, Urbana-Champaign, USA President, CTS
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Application of FGB Concept in Reversible · Evaporator Specifications Items Unit Denso evap. Test evap. Tube Length mm 255 255 Overall width mm 267 233 No. of Tubes - 39 23 Depth
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Application of FGB Concept in Reversible Cooling & AC Systems
45th KGH Congress, Belgrade 3-5 Dec 2014
Nemanja DzinicUniversity of Illinois/University of BelgradeMPG-KGH Belgrade , CTS USA
Pega HrnjakCo-Director ACRC, Res. Professor, University of Illinois, Urbana-Champaign, USAPresident, CTS
Background• Microchannel evaporators widely used in MAC system• One of the issues: two phase refrigerant distribution• Possible solutions:
yGeometry remedies: baffles, flow constrains, etc.
yGenerate mist droplets flow at the evaporator inlet
yFlash Gas Bypass
Paper 01-0139
Two Phase Refrigerant
Typical microchannel evaporator used in MAC
system
Flash Gas Bypass (FGB)
FGB: Flash Gas BypassDX: Direct Expansion
Concept used in industrial systems for many years: • Separate & bypass flash gas• Feed liquid only to MCHX
Hrnjak proposed for MC systems:• Beaver et al. 1999• Elbel and Hrnjak, 2003• Milosevic and Hrnjak, 2011• Tuo and Hrnjak, 2013, 2014
• Primary benefits • Improve refrigerant distribution• Lower refrigerant-side DP• Effect on heat transfer
Example: Good performance demonstrated in MAC system:Original system (Toyota Camry 2007) had to be modified• Same compressor and condenser• Evaporator had to be modified: flash gas bypass requires
single pass design to preserve initial distribution
• We had difficulties to get single pass evaporator in the same size as original Denso evaporator
Evaporator SpecificationsItems Unit Denso
evap.Test evap.
Tube Length mm 255 255Overall width mm 267 233No. of Tubes - 39 23Depth mm 32 20Fin height mm 5 8Fin pitch mm 1.25 1.56Fin thickness mm 0.05 0.1Slabs - 2 1Air side area m2 3.25 1.49