Heat transfer coefficients for evaporator with nested helical coils

- Experimental-theoretical analysis for an evaporator with nested helical coils.
- Local and overall heat transfer coefficients are proposed at different operating parameters.
- The water evaporation process was carried out by pool boiling at 50 °C.

The evaporation processes at low temperatures are essential for the factories and thermal systems as the heat pumps by absorption. This paper shows the design, building and characterization about an evaporator of 2 kW with a steam generation at 323.15 K. Its geometry consists in three nested helical coils with different diameters. Every coil is connected in series and the heat interchange is given by means of pool boiling. The heat transfer coefficients are indicated considering different operating conditions. The sizing method was validated taking into account the theoretical and experimental overall heat transfer coefficient of 659.8 W/m2 K. The evaporator efficiency was up to 83% taking into account a steam of 7.1 × 10−4 kg/s with a heat source at 334.35 K and 0.11 kg/s.