Steady-State Pool Boiling in Sea Water
Boiling heat transfer has attracted broad attention because of its high efficiency of heat removal and many possible applications, such as nuclear safety issues. From the lessons learned from the Fukushima Daiichi accident in Japan in 2011, Taiwan Power Company proposed an 'Ultimate Response Guideline' to ensure that there is sufficient water which can be injected into the core and prevent the core from being uncovered. However, if the core uncovered accident really happens, one still needs to continuously inject water into the core to keep the situation from getting worse. This is so called the 'quenching process'. Usually, a nuclear power plant is located near the bank of river or coast, so it is easy to get river or sea water as water resources during an emergency condition. Sea and deionized water (DI water) show significantly different performance during the quenching process. Hsu et al. conducted quenching experiments using different metal spheres (stainless steel 304 and zircaloy 702) initially at 1000 deg. C in deionized water and sea water to compare their difference. Their results indicated that sea water demonstrates a more rapid quenching process due to the suppression of film boiling, the zeta-potential between the hot surface and sea water and other effects prevent the formation of the vapor blanket. Lee et al. also studied quenching process by a reflooding method. They reported the rapid quenching time in sea water is due to higher boiling point and easily top quenching by sea salt solution. Despite the fact that better quenching performance has been observed in sea water, more fundamental experiments must be carried out to investigate basic boiling phenomena in sea water. For the past few years, many researchers studied steady boiling behavior based on pool boiling experiments. The parameters that may affect heat transfer coefficient include nucleation site density, wettability, surface tension, etc. Jamialahmadi et al. selected sodium sulfate (high solubility in water) and calcium sulfate (low solubility in water) solution as testing liquids with rod heaters used. They discovered sparingly soluble salts with inversed solubility may deposit on the heating surface and block heat transfer to bulk liquid. However, the addition of highly soluble salts may reduce heat transfer coefficient at modest heat flux but increase slightly at high heat flux. A few years later, Jamialahmadi et al. suggested the decrease in heat transfer coefficient of electrolyte solution has to do with the mass transfer in the liquid phase and developed a model with high accuracy. For nuclear safety, the use of sea water as an alternative emergency coolant, more basic physical phenomena of boiling in sea water must be investigated. The present work conducts pool boiling of sea water by using a platinum wire and compares with that in deionized water.