Pressure drop and thermal efficiency of double U-shaped tube heat exchanger

especially the effects of tube cross-sectional shape and heat exchanger inclined angle

were experimentally investigated in a low-speed wind tunnel. The results show that the internal pressure drop for the elliptical tube heat exchanger is bigger than the circular tube heat exchanger under the same averaged flow velocity inside the U-shaped tube. The difference between two different heat exchangers is more obvious under higher flow velocity inside the U-shaped tube. For the external flow

the pressure drop is significantly increased with the increase of the heat exchanger's inclined angle. Under small inclined angle

the external flow pressure drop for the elliptical tube heat exchanger is somewhat higher than the circular tube heat exchanger. However

the pressure drop outside the elliptical tube heat exchanger is significantly lower than the circular tube heat exchanger under big inclined angle. The overall heat transfer coefficient of heat exchanger with 30 degree inclination is about 50% higher than that with 10 degree. Under the density flow ratio of 0.4

the thermal efficiency of elliptical tube heat exchanger is increased about 6% in relative to the circular tube heat exchanger.