STAINLESS STEEL TUBE & PIPE   

Parallel flow, as illustrated below, exists when both the tube side fluid and the shell side fluid flow in the same direction. In this case, the two fluids enter the heat exchanger from the same end with a large temperature difference. As the fluids heat transfer, hotter to cooler, the temperature of the two fluids approach each other. Note that the hottest cold-fluid temperature is always less than the coldest hot-fluid temperature.