3917 (RP-668) -- The Effects of Nozzle Height and Orifice Size on Spray Evaporation Heat Transfer Performance for a Low-Finned, Triangular-Pitch Tube Bundle with R134a PDF

The heat transfer performance for a 1,575 fins/m (40 fpi) triangular-pitch tube in a spray evaporation environment with R134a was investigated. Shell-side heat transfer coefficients were measured through a heat flux range of 40.2 kW/m² (12.8 × 10 to the power 3 Btu/[h×ft²]) to 19.2 kW/m² (6.1 × 10 to the power 3 Btu/[h×ft²]). Both circular and rectangular spray patterns were evaluated at nozzle heights of 66.7mm (25/8 in) and 41.3mm (15/8 in) over the tube bundle. It was found that several nozzle configurations yielded shell-side heat transfer coefficients higher than those found in the pool-boiling test. Bundle heat transfer performance showed dependence on the nozzle orifice size and wall heat flux, with only a weak dependence on the type of spray pattern and the nozzle height over the top row. It was determined with collector tests that orifice size directly affected the amount of refrigerant contacting the tube bundle.

KEYWORDS: year 1995, nozzles, height, orifices, size, heat flow, performance, finned tubes, R134a, refrigerants, heat transfer coefficient, measuring, testing, evaporators, spray nozzles, comparing, geometry