Heat Transfer Enhancement of Square-Pitch Shell-and-Tube Spray Evaporator Using Interior Spray Nozzles

Abstract

This study proposes a new nozzle/heater arrangement for enhancing the heat transfer coefficient of a square-pitch shell-andtube spray evaporator. In the proposed approach, the nozzle tubes are positioned within the tube bundle in such a way that the surface of each heater tube is sprayed simultaneously by four cooling sprays. As a result, the dry-out phenomenon on the lower surface of the heater tubes is prevented. The experimental results reveal that the shell-side heat transfer coefficient obtained using the proposed spray technique is significantly higher than that achieved in a conventional flooded-type evaporator. Moreover, it is shown that the heat transfer performance increases as the saturation temperature decreases and the spray film flow rate increases.

Optimal nozzle spray cone angle for triangular-pitch shell-and-tube interior spray evaporator

“…Chang and Chiou [20] investigated the heat transfer characteristics within the gap between the heater surface and the liquid catchers, and found that a smaller gap size increased the heat transfer coefficient under low surface heat flux conditions. Chang et al [21] showed that the dry-out problem in compact shell-and-tube evaporators can also be prevented by placing the spray nozzles within the bundle interior rather than above the upper row of tubes.…”