Pool boiling performance enhancement using a scalable thermally sprayed porous copper coating

Abstract

Modified surfaces have gained significant attention from researchers for enhancing boiling performance, offering significant advantages such as effective thermal management and increased efficiency in power generation. However, large-scale and robust enhanced surfaces are still rare. In this study, a cost-effective and scalable coating technique, i.e., thermal plasma spray, is proposed for developing porous copper coatings to simultaneously enhance both critical heat flux (CHF) and heat transfer coefficient (HTC) in boiling. The pool boiling heat transfer characteristics of the coated surfaces with de-ionized water at the atmospheric pressure are presented. The study mainly focusses on the influence of surface characteristic parameters on the heat transfer performance. The detailed surface properties of the newly developed surfaces are characterized using the field emission scanning electron microscopy, X-ray diffraction and optical profilometry. The porosity and roughness of the coatings are tuned using different percentage of sacrificial material in the coating feedstock powder. The wettability and wicking properties of the coated surfaces are also characterized and their effect on the heat transfer is discussed in detail. The pool boiling phenomenon is captured using high-speed imaging and the corresponding bubble dynamics is discussed. It has been observed that the coated surfaces provide superior heat transfer performance than the uncoated surface. The best-performing coated surface exhibits a HTC of 290.3 kW/m²K and a CHF of 2700.3 kW/m², representing enhancements of 5.1 times in HTC and 2.3 times in CHF than the uncoated surface. The enhancement ratio of CHF on coated surfaces demonstrates a linear relationship with the nondimensional wicking number (Wi). Hence, the surface wickability plays an important role in enhancing the CHF.