Performance Study of Storage-Type Domestic Electrical Water-Heaters with Wedged Inlet: Unsteady Water Discharge Rate

The unsteady water discharge rate on performance of storage-type domestic electrical water-heaters with wedged inlet was studied by computer fluid dynamics simulation (CFD). The results were compared with those of conventional design EWHs having the same tank size. The heater performance is characterized the discharge efficiency, extraction efficiency and fraction of heat recoverable. The water draw-off temperature profile of steady and unsteady water discharge rate has nothing difference for wedged inlet structure, both curve was overlapped. The almost the same energy utility efficiency was gotten both steady and unsteady discharge rate for wedged inlet structure. The obviously difference of water draw-off temperature profile was shown for conventional inlet structure. Water draw-off temperature profile of unsteady discharge rate was decreased faster than steady discharge rate. The energy utility efficiency of unsteady discharge rate was also lower than steady discharge rate. The results were shown that the wedged inlet structure heater has excellent performance for energy utility efficiency under unsteady discharge rate.

Dynamic Responses of Partially Cavitated Hydrofoil Cascade to Axial Gust in Bubbly Water

A method for analysis by singularity representations is presented for dynamic responses of partially cavitated hydrofoil cascade to axial gust in bubbly water. Conservation laws of mass and momentum are applied to take account of the unsteady parts of cavity area, cavity termination thickness, and cavity pressure for unsteady partial cavity model. Also, the cavitation compliance and mass flow gain factor obtained from the cavity model determined are considered in relations to cavity length, reduced frequency, and air volume ratio. Comparisons of the mean unsteady pressure rise and unsteady discharge difference are also made with the available former results.