Özet:

In this research an experimental study was carried out to show the effect of time of opening and closing the solenoid valve on the effectiveness of finned cross flow heat exchanger, which has changed the time of opening and closing the solenoid valve (2, 4, 6 sec.) with change the mass flow rate of water each time and the range values between (0.027-0.0816 kg/s) with constant of mass flow rate of air at (0.032 kg/s). The results obtained from experiment works that the decreasing in the time of opening and closing the solenoid valve from (6 sec.) to (2 sec.) leads to increase internal heat transfer coefficient (hi) the highest increase was by (18.37%) at mass flow rate of water (0.027 kg/s) and increase the overall heat transfer coefficient (U) and the highest percentage of increase (7.36%) at mass flow rate of water (0.027 kg/s). The experimental results obtained show that the increasing both the number of units transmitted (NTU) and effectiveness of the finned heat exchanger when decrease the time of opening and closing the solenoid valve from (6 sec.) to (2 sec.) and the highest percentage of the increase occurring is (8.4%) and (1.74%) respectively at mass flow rate of water (0.027 kg/s).

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