DA-00-11-2 -- Effects of Oil on Boiling of Replacement Refrigerants Flowing Normal to a Tube Bundle-Part II: R-134a PDF

Local, experimental heat transfer coefficients have been obtained for boiling refrigerant flowing up and across a tube bundle segment representing a full flooded evaporator tube bundle. R-134a data with a structured enhanced boiling tube are available. This tube has reentrant cavities designed for higher saturation pressure refrigerants. The refrigerant enters at 15% vapor quality and exits at nearly 100% vapor in order to simulate an actual evaporator bundle. Both heat flux, 2607 to 10,427 Btu/h·ft² (8224 to 32,893 W/m² ), and oil content, 0% to 12% (by weight), are varied; the mass flux is not an independent variable but determined by the heat flux. Local tube and bulk fluid temperatures are measured directly, by thermocouples, to calculate the refrigerant-side heat transfer coefficients. The bundle segment saturation temperature setpoint (taken at the top of the tube bundle) is 40°F (4.4°C).

Units: Dual