SPRAY COOLING WITH AMMONIA ON MICRO-STRUCTURED SURFACES

摘要

Experiments were performed to investigate spray cooling enhancement on micro-structured surfaces. Surface modification techniques were utilized to obtain micro-scale indentations and protrusions on the heater surfaces. A smooth surface was also tested to have baseline data for comparison. Tests were conducted in a closed loop system with ammonia using RTI's vapor atomized spray nozzles. Thick film resistors, simulating heat source, were mounted onto 1cm × 2cm heaters and heat fluxes up to 500W/cm{sup}2 (well below critical heat flux (CHF) limit) were removed. Two nozzles each spraying 1cm{sup}2 of heater area used 96ml/cm{sup}2-min (9.7gal/in{sup}2-hr) liquid and 13.8ml/cm{sup}2-s (11.3ft{sup}3/in{sup}2-hr) vapor flow rate with only 48kPa (7psi) pressure drop. Results for micro-structured surfaces with protrusions and indentations offered significant performance enhancement of 115% and 52% increase in heat transfer coefficient over smooth surface respectively.