The effects of ultrasonic vibrations on the heat transfer characteristics of LiBr aqueous solution at low pressures are studied experimentally. Pool boiling curves of a horizontal smooth tube are obtained using distilled water and 50% LiBr aqueous solution as test liquids. The system pressure p{sub}s is varied from 12 to 101 kPa, and the liquid subcooling ΔT{sub}(sub) ranges from 0 to 70 K. The frequency of ultrasonic vibration v is set to 24 and 44 kHz, and the power input to the vibrator P is varied from 0 to 35 W. The wall superheat at boiling incipience is found to decrease with increasing P, and the nucleate boiling curve shifts toward the lower wall temperature region. However, the effect of P is not found to be very significant in the high heat flux region, especially in the case of small liquid subcooling. Ultrasonic vibration is found to improve the nucleate boiling heat transfer coefficient by up to a maximum of 3.5 times and to prevent crystallization of the solution and precipitation of additives.
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