Abstract
As the use of environmentally acceptable refrigerant is required recently, CO_2 is proposed for one of alternatives and recommended in car air-conditioners and heat pumps for hot-water supply system. However, remaining unsolved problems are not small amont to develop the designing method of heat exchanger. In this study, to clarify the heat transfer characteristics of CO_2 in a small diameter tube of 1.8 mm I.D., the experiments were carried out on flow boiling and the local heat transfer coefficients are measured in the range of mass velocity from 100 to 250 kg/m^2s and of wallheat flux from 3.77 to 37.4 kW/m^2 at constant inlet pressure of about 3.5 MPa.
