Hiroyuki Asou

Measurement of the Speed of Sound in 2,3,3,3-Tetrafluoropropylene (R-1234yf) Liquid Phase with an Ultrasonic Sensor

The speeds of sound in near saturated and subcooled liquid phases of R-1234yf have been measured using a ultrasonic sensor. The measurements were conducted at the temperature range from 0 to 80 °C, and the pressure range from 0.316 to 2.52 MPa. In order to validate the ultrasonic sensor, the measurement in pure water at the temperature range from 0 to 80 °C was also performed. The measurement result of water was compared with those calculated from REFPROP (based on IAPWS-95) and PROPATH (based on IAPWS-IF97). The result of water agrees well with that calculated from REFPROP within a maximum deviation of 0.28%, except for that at temperature of 80 °C. And it agrees well also with that calculated from PROPATH within a maximum deviation of ±0.2%. The measurement results for near saturated and subcooled liquid phases of R-1234yf were compared with those calculated from REFPROP and JSRAE thermodynamic table.

Experiments on Flow Boiling Heat Transfer of Ammonia/Water Mixture Inside an Internally Spirally Grooved Horizontal Tube

Experiments were performed on the flow boiling of the zeotropic mixture of water-ammonia inside an internally spirally grooved horizontal steel tube with a 12mm average inner diameter. The experimental conditions were the mass fraction of ammonia: 0.95, 1.0 kg/kg, the mass velocity: 40 to 80 kg/(m2 s), the heat flux: 0 to 20 kW/m2 and the pressure: 0.7 MPa. The measured heat transfer coefficient reached its maximum as the quality approached about 0.6 but decreased abruptly as the quality increased. This sharp decrease as the quality increased beyond 0.6 may have been caused by mass diffusion resistance that increased the temperature locally at the vapor-liquid interface. The temperature increase at the vapor-liquid interface is discussed by analyzing the phase equilibrium characteristics and is explained in terms of the relationship between the bulk temperature and vapor quality. The heat transfer coefficients are also compared with those for pure ammonia.Copyright