PVT measurements of water-ammonia refrigerant mixture in the critical and supercritical regions

The PVTx properties of H2O + NH3 mixture (0.2607 mole fraction of ammonia) have been measured in the near- and supercritical regions. Measurements were made along 40 liquid and vapor isochores in the range from 120.03 to 727.75 kg m−3 and at temperatures from 301 to 634 K and at pressures up to 28 MPa. Temperatures and densities at the liquid–gas phase transition curve, dew- and bubble-pressure points, and the critical parameters for the 0.7393 H2O + 0.2607 NH3 mixture were obtained using the quasi-static thermograms and isochoric (P–T) break-point techniques. The expanded uncertainty of the density, pressure, temperature measurements at the 95% confidence level with a coverage factor of k = 2 is estimated to be 0.06%, 0.02–0.09%, and 15 mK, respectively.