This paper addresses the effect of hydraulic diameter on single-phase and condensation heat transfer and pressure gradient for R-I34a in multi-port flat extruded aluminum tubes. The hydraulic diameter range of the four tubes tested is between 0.44 and 1.56 mm. This work is believed to provide condensation data on the smallest hydraulic diameters reported in the literature. The modified Wilson plot method was used to determine the heat transfer coefficient for water-side flow in the annulus. The data span 300-1000kg/m2-s mass velocity and approximately 15-to-90% vapor qualities. The condensation coefficient and pressure gradient increases with decreasing hydraulic diameter for all tubes. The effect of hydraulic diameter on condenser design and operation is also discussed. The ability of existing correlations to predict the single-phase and condensation coefficients are evaluated.

Thermal energy storage (TES) is an advanced energy technology that is attracting increasing interest for thermal applications such as space and water heating, cooling, and air conditioning. TES systems have enormous potential to facilitate more effective use of thermal equipment and large-scale energy substitutions that are economic. TES appears to be the most appropriate method for correcting the mismatch that sometimes occurs between the supply and demand of energy. It is therefore a very attractive technology for meeting society’s needs and desires for more efficient and environmentally benign energy use. In this study, thermal energy storage systems, energy storage, and methods, hydrogen for energy storage, and technologies are reviewed.