Discussion:

The experimenters set the boiler temperature at 65 degrees C. They obtained the initial and final temperature of hot and cold water by the use of the control panel. After obtaining the necessary temperatures, these are applied in the formulas to determine the following:

A. Actual Heat transfer (Qactual)

The Actual Heat Transfer is obtained by using the initial and final temperatures either hot or cold water.

Qh=Q c=Qactual

Qc=mCp(Tcout−T c¿)

Qh=mC p(T hout−Th¿)

The mass flow rate is obtained by using the following equation:

V=m v

m=Vv

The flow rate of the cold and hot water is set to 2 liters per minute. The specific volume of water is 1 Liter per kilogram.

In the experiment, the Qc is not equal to Qh. The experimenters calculate both Qc and Qh. There is a slight difference. The values for using the hot and cold water temperatures are plotted in order to signify that Qh is not equal to Qc because of human errors during the experiment or the equipment itself has a defect.

The maximum heat transfer is obtained by:

Qmax=mCp (T h¿−T c¿ )

After getting the Qactual and Qmax, heat exchanger efficiency is solved by the ratio of Qactual to Qmax.

The overall heat transfer coefficient based on inside and surface area can be obtained by the following formulas:

U i=Q

Ai∆T m where Ai = 0.069498 m2

U o=Q

Ao∆T m where Ao = 0.075438 m2

The logarithmic mean temperature difference, ∆T m, is obtained by:

∆T m=(T hout−T cout)−(T h¿

−T c¿ )

ln [T hout−T coutT h¿

−T c¿¿]¿

The different formulas are used in the three types of heat exchangers in the experiment.

Conclusion:

The experimenters concluded that among the different three types of heat exchangers, the one using the counter flow has the higher heat exchanger efficiency. The counter flow or counter-current has higher efficiency because of the uniform temperature between the moving liquids over the length of its path. Moreover, the counter flow heat exchangers only requires a low heat transfer surface area. Thus, it yields a higher value for the logarithmic mean temperature difference than the parallel flow heat exchangers. In comparison of the three types of heat exchangers for both types of flow, the plate heat exchanger has the highest efficiency.