Statistical optimization of hydrate formation conditions of TBAB and THF mixture as a cold storage material for air-conditioning system based on response surface methodology

• RSM has been employed to optimize the hydrate formation conditions of TBAB/THF as a cold storage material.
• Sub-cooling driving force and electrical conductivity variations of hydrate formation have been evaluated.
• One optimal condition has been determined by overall desirability function.

Response surface methodology has been employed to optimize the hydrate formation conditions of tetra-n-butylammonium bromide (TBAB) and tetrahydrofuran (THF) mixtures as cold storage materials for air-conditioning system. It has been focused on the maximization of sub-cooling driving force and electrical conductivity variations of hydrate formation considering the operating conditions. The results of ANOVA have revealed that TBAB/THF mass ratio has significant effect on sub-cooling driving force, while stirrer speed and jacket temperature are significant factors for electrical conductivity variations. According to RSM, the optimum TBAB/THF mass ratio, stirrer speed and jacket temperature have been respectively found to be 1.96, 784 rpm and −6.66 °C for sub-cooling driving force and 1.23, 798 rpm and −5.2 °C for electrical conductivity variations of hydrate formation. Overall desirability function of both responses has provided one optimal condition yielding TBAB/THF mass ratio of 1.47, stirrer speed of 800 rpm and jacket temperature of −6.4 °C.