The human body has wide ranges of heat transfer processes in different modes and types as separated processes and/or associated with mass transfer. These vital mechanisms have an essential role in the regular physiological and biological activities of the human body. Principally, the main source of heat generation within the human body is the metabolism process, while the blood flow rate plays a major role in the heat exchange phenomenon. On the other hand, the heat transfer from the human body has many modes and forms; for instance: heat losses by convection, radiation, and evaporation in addition to heat loss through clothing and breathing. In this study the modes of bio-heat transfer are modeled and investigated for different human activities, such that multi mathematical models have been introduced to form a full bio-heat model for human body. This model has been invoked to analyze the varied modes of bio-heat processes under miscellaneous activities. Furthermore, it could be used to elucidate the scales and quantitative ranges of each bio-heat modes under different human performance. The results of this investigation showed that the maximum bio-heat losses is due to evaporation process (Q_evp) and heat losses through clothes (Q_clth),whil the minimum heat losses from the human body is in the form of convection  (Q_conv) and breathing (Q_br). Moreover, for standard activity of the human body (i.e., standing-writing-walking) the body core temperature increased by 0.41% of base temperature (T_b) (i.e., 37^oC) within the investigation time period (i.e., 1500 sec.), it starts moderate increasing up to maximum limit then it reaches a plateau and keep on the same limit, while the skin temperature raised up by 5.41% of base temperature for the same time period. The results of this study may be considered for ergonomical applications, climate control designs, clothes and shoes styling and designs and pharmaceutical industry.