Heat Transfer Temperature Experiment

After the initial trail run of the experiment is done, the bath vessel is filled with the bath liquid of choice i.e., Water or Motor Oil till all the coils inside the vessels are submerged.

Heat input is given to the bath liquid using the dimmerstat provided, by turning the knob to a desired value of temperature, say 40 0C. Allow the bath liquid to gain temperature gradually. Using the auto transformer put the motor into motion by fixing a value of rotation on the scale. This motor rotation allows the impeller to turn inside the liquid.

The inlet of the coil is provided with coolant stream and the volumetric flow rate is regulated as per the need. Using a stopwatch and a measuring jar the flow rate of the liquid is measured. Wait till the

Also measure the RPM of the motor using a Tachometer. Carry out the experiment at different temperatures with different pre fixed flow rates using chosen impeller. Repeat the experiment with different impellers mentioned earlier at those pre fixed flow rates and temperatures. The entire process is carried out with different bath liquid i.e., Motor Oil.

V. RESULTS & DISCUSSIONS

From the above plotted graphs between Overall Heat Transfer Coefficient and Reynolds Number it can be asserted that the overall heat transfer coefficient varies with change in speed of impeller and the flow rate of the coolant.

As from the Water-Water system graphs at different pre chosen temperatures i.e., 400C, 500C, 600C, 700C using different impellers it can be understood that the heat transfer coefficient attains higher magnitudes with the impeller speed increments and gradual raise in temperature.

The speed of impeller has no direct consequence on the local inner heat transfer coefficient. The variation inside the coil in the H.T. C. is due to the secondary flow existence at the curves of the coil which regulates the effective heat transfer.

But in the case of Oil-Water system the overall heat transfer coefficient values are not greatly promoted in comparison with water as bath

Inherent defects like impeller pitch, coil curvature, thermostat effective temperature regulation and shaft load on the motor are negligible.

VI. CONCLUSIONS

As per the expected values, the deviations are appreciably low. In Water-Water system the heat transfer is more effectively done in comparison with Oil-water system.

The Overall Heat Transfer Coefficient U as expected increases with Reynolds Number NRe. As the flow rates increases the molecular movement increases so the film thickness reduces due to turbulence creation.

The correction factors are to be associated to the existing correlations to account for deviated behavior of the apparatus.

The variations of fall and raise in the H. T. C values from the graphs and observations notes that the predictable values are yet to arrive only if further study at different speeds which are intermediate to the original ones is done.

Helical coil heat exchangers are not studied extensively so there is gap for any forward comments on the effects of Reynolds number in tube side and consequent changes due to secondary flow. Hence for higher flow rates also the study is supposed to be