Falling film evaporation in a triangular tube bundle under the influence of cross vapor stream

The falling film evaporation and the effect of cross vapor stream in falling film evaporator with triangular tube bundle using R123 was experimentally investigated. The variations of local and bundle average heat transfer coefficients were described. The tube bundle consisted of 4 × 3 (column × row) of triangular horizontal copper tubes. The tests without vapor effect were conducted with nominal heat fluxes of 20 to 60 kWm^–2, saturation temperatures of 6 to 16 °C and film flow rates of 0.016 to 0.18 kgm^–1s^–1. Cross vapor stream effect experiments were operated at three heat fluxes of 20, 30 and 40 kWm^–2 and two film flow rates of 0.035 and 0.07 kgm⁻¹s⁻¹, and the vapor velocity at the narrowest interstice in the tube bundle varies from 0 to 5.0 ms⁻¹. It is indicated that the heat transfer is seriously influenced by the bundle effect while less affected by changing of saturation temperature. With the increase in vapor velocity, the heat transfer performance is generally weakened; the cross vapor stream has a strong influence on falling film evaporation of R123.