Fluid flow and heat-transfer in a porous medium over a stretching surface have been investigated. The flow is influenced by linearly stretching the surface with internal heat generation or absorption and by the presence of suction, blowing and impermeability of the surface. We have two cases are studied, namely: - (i) Constant surface temperature (CST case), (ii) Prescribed surface temperature (PST case).The effects of Prandtl number, permeability parameter, suction/blowing parameter and heat source/sink parameter on both flow and heat-transfer characteristics are studied and the variations of dimensionless surface temperature with various parameters are graphed and tabulated. In these cases, the final product of desired characteristics depend on the rate of cooling in the process and the process of stretching. Heat transfer in a porous medium over a stretching surface with internal heat generation and suction or injection is studied. The boundary layer equations are transformed to ordinary differential equations containing a Prandtl number, permeability parameter, injection parameter and heat source/sink parameter. Numerical solution for velocity field and the skin friction are obtained. Also, solution for the temperature and the heat transfer characteristics are obtained. Therefore, it is very useful to understand the molecular structure and properties of the polymers before they are selected for processing. Simulation is a useful tool to investigate the process characteristics as well as for scaling up and optimization of the production. And Flow profiles of the blown films. This will help to improve the physical and mechanical properties of the films in a cost effective way, which will in turn be of great benefit to the food and packaging industries. Also the experimental and numerical study of a blown sheet extrusion were carried out using two different low-density polyethylene (LDPEs). In the experiment, the key parameters measured and analyzed were molecular, Time temperature superposition (TTS) technique was utilized to determine the flow activation energy, in the numerical study, blown film simulation was carried out to determine the bubble characteristics and freeze line height (FLH).