Heat Transfer During Liquid Contact on Superheated Surfaces

Abstract

Several boiling regimes are characterized by intermittent contacts of vapor and liquid at the superheated wall surface. A microthermocouple probe was developed capable of detecting transient surface temperatures with a response time better than 1 ms. The transient temperature data were utilized to determine the time-varying heat flux under liquid contacts. The instantaneous surface heat flux was found to vary by orders of magnitude during the milliseconds of liquid residence at the hot surface. The average heat flux during liquid contact was found to range from 105 to 107 W/m2 for water at atmospheric pressure, as wall superheat was varied from 50 to 450°C.

Heat transfer at multiple-intermittent impacts of a hollow cone spray

“…Each curve can be divided in four regions in terms of their slopes. After a steady period before spray impact, measured temperature decreases sharply in Region I due to fast vaporization of leading droplets, as reported by Chen and Hsu [31], and the heat flux reaches an absolute maximum, _ q 00 max ; in Region II surface temperature reaches a minimum, min(T w ), but the rate of temperature decay decreases and the heat flux remains almost constant or even slightly decreases, which may be associated with build up of a liquid film and lower vaporization rates, as also observed by Labeish [29]; in Region III, measured temperatures increase due to complete evaporation of the residual liquid. This description is associated with a thermal morphology which changes from a non-wetting regime right after spray impact to a regime associated with a short contact between the liquid and the target.…”

Thermal product of type-E fast response temperature sensors

“…The accurate measurement of heat transfer rates has long been recognized as a key to improvements in unsteady energy conversion devices such as internal combustion engines [1][2][3][4][5][6], aerodynamics vehicles [7][8][9], gun barrels [10] and in boiling experiments [11][12][13]. The heat flow in these devices is usually quite high (hundreds of kilowatts per square meter) and very unsteady.…”

Design and fabrication of coaxial surface junction thermocouples for transient heat transfer measurements

“…The need for an instrument to measure transient temperatures in a short time duration flow (few microseconds) arises in numerous heat transfer investigations particularly in internal combustion engine cylinder walls [1][2][3][4][5], aerodynamics facilities [6,7], gun barrels [8] and in boiling experiments [9][10][11].…”