Direct steam generation in parabolic trough collector (DSGPTC) has had a great importance because of its thermoeconomic advantages and many researches have be done in this field. Due to that reason this paper studies the convection heat transfer from absorber tube of a PTC to all phases of water (liquid water, wet steam and dry steam) along the whole distance of fixed length of a DSG-PTC generates a high temperature superheated steam (561 °C). All heat transfer operations in PTC has been modelled and then the convection' components which are; fluid temperature, tube wall-fluid temperatures difference and heat transfer coefficient have been analyzed in details at different operation conditions such as inlet fluid pressure, direct solar beam and mass flow.