Aluminum Pipe Orientation and Diameter Change Effect on overall heat transfer coefficient in Heating System

The objective of this work is to study experimentally the effect of water flow rate on the overall heat transfer and the rate of heat rejected from aluminum pipe of diameter (30 mm, 50 mm). Experimental data are obtained from tested rig with different conditions. Results obtained from calculations with its curves are discussed with conditions changing. The U results show when water flow rate increase, its values increase for horizontal and vertical tested pipe because of increase in the internal thermal resistance due to increase in the Res number and water velocity. The results show that the values of U for 50 mm pipe diameter are less than for 30 mm pipe diameter for the same flow rate because of water velocity and Res number decrease. The heat rejected rate results through the pipe to ambient shows when water flow rate increase; its values increase for horizontal and vertical tested pipe because of increase in U value and temperature difference. The results show that the values of heat rejected rate for 50 mm pipe diameter are greater than for 30 mm pipe diameter for the same flow rate because of pipe outside area increase. The heat rejected rate in the pipe of 50mm diameter are greater than in the pipe of 30mm diameter for the same water flow rate and for all average water temperatures because of outside pipe area increase.