Handbook of air conditioning and refrigeration / Shan K

at an oil concentration of 3 percent. For 300-SSU oil, the surface heat-transfer coefficient inside the
microfin tube increases slightly and then decreases about 20 percent when the oil concentration
increases from 0 to 3 percent.
Superheated Region. In the superheated region, the quality of refrigerant x r � 1. The refrigerantside
heat-transfer coefficient is low. Because of the relatively high outer surface temperature caused
by the superheated refrigerant, the outer surface of the DX coil corresponding to the superheated
region may be dry. The superheated region is small. For simplification, the rate of heat transfer
(including both sensible and latent heat) of the whole DX coil is often multiplied by a degrading
factor F super to account for the existence of the superheated region.
Simultaneous Heat and Mass Transfer
REFRIGERATION SYSTEMS: COMPONENTS 10.5
FIGURE 10.1 Temperature and pressure drop across a typical DX coil using HCFC-22 as refrigerant.
(All pressures are measured at gauge pressure.)
In a DX coil, the driving potentials for the simultaneous heat and mass transfer during cooling and
dehumidifying are the enthalpy difference between the ambient air and the saturated air film at the