Currently I am doing a project on heat transfer .I have considered a system in which , there is a chamber with desired volume (1 m3 ).Air is filled inside the chamber at 5 bar and 35 degree Celsius .There will be a tubular heat transfer unit inside the chamber. Water is flowing through the tube at a particular flow rate . Inlet temperature of water is 90 degree Celsius. I need to raise the air temperature to 80 degree Celsius. As of my initial impression there will be a forced convection from flowing water to the tube body , natural convection from tube body to air in contact with tube surface and radiation heat transfer with in the chamber volume . I would like to know how do I find the heat transfer rate from water to air , final temperature of water after particular time and length of tube.