I need hep to paraphrase these graphs

Problem Statement

The purpose of this experiment is to compare the theoretical overall heat transfer coefficient with the experimental overall heat transfer coefficient in both a double pipe heat exchanger and a shell and tube heat exchanger. For the theoretical value, a correlation of the Nusselt number is used to calculate the overall heat transfer coefficient. While calculating the overall heat transfer coefficient, the conductive heat transfer occurring across pipe wall and the convective heat transfer occurring inside and outside pipes are considered. Thus, the log mean temperature difference and the experimental value of the heat transfer coefficient can be calculated through measuring the temperature at the inlet and outlet using a type k thermocouple.

Experimental System

The experimental system consisted of two heat exchangers double pipe heat exchanger and shell and tube heat exchanger. Starting the experiment with the shell and the tube heat exchanger then the double pipe experiment. Co-current and counter-current configuration were done for each experiment. The double pipe heat exchanger consists of inner tube and outer tube. However, the shell and tube heat exchanger has seven stainless steel tubes arranged in a circular organization.

The cold water was supplied from the sink and go bake into the sink. Hot water was provided by the heating reservoir and return to the system, see (App.A). The flow rate of cold water was measured using the rotameter which was connected to the inlet (sink) and using the digital reading in the heat exchanger itself. Also, experimentally the flow rate of cold water was measured using a graduate cylinder and a stopwatch. The flow rate of hot water was measured by the digital reading in the machine. Moreover, the temperatures for the inlet and outlet of both streams was measured by thermocouples. The thermocouples were placed in the inlet and outlet of both cold and hot water.

Experimental Methods

First, the hot water was connected to the tube side of the heat exchanger and cold water was connected to the shell side. The inlet hot water temperature is held approximately constant at 40℃. The Heat exchanger has flowmeters to measure flow rates of cold and hot water. The flow of hot water was kept constant at 1 L/min and cold water flow rate was changed between 1.2, 2, and 2.8 L/min. The cold water flow rate was verified by measuring the flow rate with a graduated cylinder and stopwatch. a calibration of cold water flow rate was measured at different rotameter to ensure accuracy as shown in (App.B, figure1). Once the temperature stopped changing around 4-5 mins, the system reaches steady state. At steady state, the temperature of inlet and outlet of cold water and inlet and outlet of hot water is recorded for each trial. The same process was done for counter-current and co-current configuration. Second, double pipe experiment was done at same flow rates and inlet temperature. Two trials were performed to ensure having stable outlet temperatures for both counter-current and co-current flow.

Key Points in Experimental Procedure:

1. Connect shell and tube to the Armfiled heat exchanger platform, and connect tubes (hot water, cold water). First do that for co-current, then for counter current.

2. A calibration for each cold flow rate was made to adjust experimental flow rates using graduate cylinder and stopwatch.

3. Pour water to drain cylinder and then connect the 4 thermocouples wires that indicate the inlet and outlet temperatures.

4. Keep the flow rate of hot water at 1 [L/min]

5. Change the flow rate of cold water (1.2, 2, and 2.8 L/min).

6. Wait 3-6 min to reach the equilibrium and then record T1, T2, T3, and T4 . change the cold water flow three times and record T1, T2, T3, and T4 .

7. Repeat the same steps after switching the heat exchanger to counter-current.

8. Connect the tubular heat exchanger to the Armfield heat exchanger platform, and then connect 6 thermocouples from Armfield heat exchanger platform to tubular heat exchanger that indicate T1, T2, T3, T4.

9. Repeat steps 3, 4, and 5 for both co-current and counter-current.