EXPERIMENTAL CHF AND MHF CORRELATIONS IN TRANSIENT BOILING SYSTEMS WITH VERTICAL RECTANGULAR PARALLEL PLATES

The objectives of this article are to propose critical heat flux (CHF) and minimum heat flux (MHF) correlations in transient forced-connecti ve boiling systems and to investigate the parametric effects on CHF an d MHF. Experiments were conducted to obtain the CHF and MHF values in forced-convective boiling systems with vertical, parallel, rectangular channels between parallel plates. A nondimensional transient paramete r tau = ((z) over bar(2)/alpha(f)T(sat))(dT(W)/dt)(CHF), was adopted t o quantify the transient effects on CHF and MHF values. Experimental r anges are 718.0-2162.0 kg/m(2)s for mass flux, 7.5-20.3 degrees C for inlet subcooling, and 3.0-8.0 mm for channel gap distance. The system pressure is 1.0 atm. The results show that CHF and MHF increased with increasing inlet subcooling. It was also found that CHF and MHF increa sed somewhat linearly with increasing mass flux at the top of the test section, while they were weakly dependent on the mass flux at the bot tom of the test section. New CHF and MHF correlations were developed f or upward flow in transient boiling heat transfer with maximum error b ands of +/-18% for CHF and +/-30% for MHF.