|Title:||Investigation of Adiabatic Refrigerant Pressure Drop and Flow Visualization in Flat Plate Evaporators
|Author(s):||Jassim, E.W.; Newell, T.A.; Chato, J.C.
|Abstract:||Adiabatic pressure drop and flow visualization in chevron plate, 1:1 aspect ratio bumpy plate, and 2:1 aspect
ratio bumpy plate heat exchangers were investigated for vertical upward flow with R134a. Qualities ranging from subcooled
liquid to superheated vapor were investigated. Mass fluxes ranged from 16 kg/m2-s (for superheated vapor) to
approximately 300 kg/m2-s (for sub-cooled liquid). The pressure drop experiments were conducted for 10o C and 20o C
inlet temperatures. The flow visualization experiments were conducted at a 10o C inlet temperature.
The following is the order of highest to lowest pressure drop geometries on both a mass flux and mass flow
bases: chevron plate, 1:1 aspect ratio bumpy plate, and 2:1 aspect ratio bumpy plate. These trends are more
pronounced on a mass flow basis.
Four flow regimes were observed for the flat plate geometries investigated and are mapped out on a mass
flux versus quality basis for each geometry. The chevron geometry was seen to undergo flow transitions at lower
qualities and mass fluxes than the bumpy plate geometries.
The kinetic energy per unit volume of the flow was found to have a strong linear relationship with pressure
drop for both single-phase and two-phase flow, suggesting that inertial effects are the dominant mode of pressure
drop in flat plate heat exchangers. Vapor pressure drop prediction models based on the kinetic energy of the flow are
presented, which predict pressure drop within 20%. A two-phase pressure drop model is developed, also based on
kinetic energy per unit volume of the flow. A pseudo void fraction is defined in order to correlate the two-phase
pressure drop to the single-phase pressure drop. The two-phase pressure drop model predicts two-phase pressure
drop to within 15% of experimental measurements.
A description of and modifications to the experimental test facilities are provided. In addition, the
geometries and construction of the plates are provided.
|Publisher:||Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
|Series/Report:||Air Conditioning and Refrigeration Center TR-187
|Sponsor:||Air Conditioning and Refrigeration Project 120
|Date Available in IDEALS:||2009-06-04