Article for Enhanced Boiling Heat Transfer

Technology

This invention finds that scale formation can in fact be positive for boiling, as it enhances a type of boiling called nucleate boiling. Nucleate boiling has a heat transfer coefficient of up to an order of magnitude greater than regular filmwise boiling. The presence of scale can thus improve boiling heat transfer, but only if this scale formation is deposited appropriately. The current technology proposes methods to maintain a scale deposit at a controlled thickness (e.g., below a maximum thickness, within a desired range, or in a certain pattern) that can improve the nucleation site density and bubble formation, which both serve to enhance nucleate boiling. These methods include applying a photoactive coating to promote scale growth or controlling growth via water chemistry or mechanical removal. The technology also recommends a specific set of scale materials (e.g., calcium carbonate, barium sulfate), deposition thicknesses and deposition patterns that can promote this nucleate boiling.  

Problem Addressed

In many industrial applications, the process of boiling can result in unwanted byproducts (such as calcium sulfate in oil wells) accumulating on the boiling surface. This is known as scale formation, and it can create heating inefficiencies by reducing the thermal conductivity of the boiler. Much expense is incurred to remove this scale, and the useful lifetime of the equipment is shortened.   

Advantages

• Improved boiling heat transfer