Enhancement of Heat Removal Rate in Film Boiling Regime by Spray Cooling with Sea Water

Abstract

Water spray cooling is an important technology which is used in steel industries. The final mechanical properties of the steel are directly proportional to the quenching rate. Spray cooling is an important technique to achieve very high cooling rate. However, the achieved cooling rate is not sufficient for the metal which are used in some specific applications such as production of low weight and high strength steel which is used for the fabrication of light weight vehicle. Hence, the current process needs to be further enhanced. In the current case, experiments were conducted by using spray of different coolants such as pure water, salt added water surfactant added water, salt plus surfactant added water and sea water. For the above mentioned experiments an experimental set up was fabricated and for the calculation INTEMP software has been used. Initially, for the coolants, the optimum height (40 mm) and the flow rate (16.67 × 10-5 m3/s) were determined. The experimental result of salt added spray cooling reveals that the quenching rate increases with increase in salt concentration up to 0.4 M due to salt deposition effect which alter the heat transfer mechanism from convection mode to conductive mode. However, further increment shows decline trend and this is due to the decrement of resultant thermal conductivity of the substrate. In addition to the above, cooling experiments also done by using sea water. The results show that the cooling rate increases with the increase in dilution and this happens because of the combined effect of salt deposition and contact angle decrement. In addition to the above, for the comparative study, among all the coolants, a cooling experiment was conducted with surfactant (Tween 20). Finally, the comparison among all the coolants has been made and from the comparison it is concluded that 100 % sea water produce maximum cooling rate.