An experimental study was carried out on n-pentane nucleate boiling at atmospheric pressure and saturation temperature for different gap sizes. The boiling was investigated in a confined space delimited by two horizontal discs, a heated surface and an adiabatic surface, for distances varying between 0.1 mm and 13 mm. Tests were carried out on heated surfaces of 12 mm and 20 mm diameter. The effects of the gap size on the partial boiling curve and the diameter of the heated surface were studied. A dimensionless analysis was carried out and a correlation to describe the phenomenon of confined nucleate boiling is presented.