Latent heat of vaporization

Question

Normal butane (C₄H₁₀) is stored as a compressed liquid at 90°C and 1400 kPa. In order to use the butane in a low-pressure gas-phase process, it is throttled to 150 kPa and passed through a vaporizer. The butane emerges from the vaporizer as a gas at 70°C and 150 kPa. Using only the data below and any assumptions you believe are reasonable,

i) determine the latent heat of vaporization of normal butane at 70°C,

ii) calculate the heat that must be supplied to the vaporizer per kg of butane passing through it,

iii) determine the temperature and the mass fraction of butane that is vapour at the inlet of the vaporizer.

Data for normal butane:

Antoine's equation:

ln (p^sat [bar]) = 9.058 - [2154.9/ (T[k]-34.42)]

Heat capacity of the liquid at any constant pressure:

C_P[J/kg K] = 1361 + 3.77 T[K]
Density of liquid at 90°C = 158 kg/m³