Investigating Heat Transfer in a Shell and Tube Heat Exchanger

Describe the use of heat exchanger to support an industry process to improve energy efficiency.

Example of situation where heat exchanger was used in an industry application.

Briefly explain steps taken to acquire all the lab data correctly and accurately.

Outline the important elements need to be considered to maintain the consistency of data being recorded.

The rates of heat transfer.

The Logarithmic Mean Temperature Difference

The overall heat transfer coefficient

Examine the rate of heat transfer calculated for both the hot and cold fluid data and discuss the discrepancy between the two.

Analyse the impact of using the Logarithmic and Arithmetic Mean Temperature Difference methods in calculating the temperature difference between the hot and cold fluids.

Define the relationship and discuss the importance of mass flow rate on the overall heat transfer coefficient and the heat exchanger as a whole.

5.Conclusions

Summary of findings on the use of shell and tube heat exchanger.

Draw conclusions on the effect of mass flow rate on the overall heat transfer coefficient and the heat exchanger as a whole.

Overview:

The main objective of carrying this lab is to investigate the impact of changing the cold water and hot water flow into and out of a shell and tube heat exchanger on overall heat transfer coefficient. Figure 1 shows the GUNT WL 110 series service unit which can be used to attach to different types of heat exchanger units such as tubular, plate and shell and tube heat exchanger.

Fig. 1: GUNT WL 110 series service unit

Figure 2 shows the shell and tube heat exchanger unit which has been selected and used in this lab assignment.  The shell of this heat exchanger unit is made transparent to allow the tube bundle to be visible (Fig. 2).

Fig. 2: GUNT shell and tube heat exchanger unit

This shell and tube heat exchanger unit comes with a tube bundle which consists of parallel tubes (seven tubes in this case) as illustrated in Fig. 3. These tubes are soldered to the tube plates on both sides and creates two separate areas, the tube area (inside the tubes) and the shell area (between the tubes and the outer shell).

Fig. 3: GUNT shell and tube heat exchanger unit tube bundle

The shell area is divided by four baffle plates (Fig. 3). They deflect the fluid in the shell area, thus improving the heat transfer from hot fluid to cold fluid. The flow in the shell area is essentially perpendicular to the tubes, hence the direction of the flow is known as a cross current flow.

Fig. 4: Shell and tube heat exchanger schematic with cross counter flow set-up

Figure 4 illustrates the principle (illustrated with more than seven tubes in this diagram as an example). In this case, the hot water (red) flows through the tube area and cold water (blue) flows through the shell area. When viewing it axially, the flows can run in the same direction or in opposite direction, hence differentiating between cross-parallel flow (PF) and cross-counter flow (CF) configurations. For this lab assignment, the heat exchanger has been set to run on the cross-counter flow configuration.

By referring to Table 1, use the recorded data to calculate the following:

The rate of heat transfer Q ? for both the hot and cold fluid and the mean rate of heat transfer Q ?_m in W

The Logarithmic Mean Temperature Difference LMTD in ?

The overall heat transfer coefficient U in ^2.?

Use the calculated overall heat transfer coefficient U and plot a graph showing the mass flow rate m ? versus U. Discuss extensively the effect of m ? on U.

Note: Use mean fluid temperature to define both hot and cold fluid properties individually. Different fluid properties can be obtained by referring to “Thermodynamic and Transport Properties of Fluids” table (i.e. Page 10 - Further properties of water).

Write a 1500-word report (strictly limited to ±10% and additional words will not be marked). When submitting the report, please make sure to include the first 3 pages of this assignment cover sheet on the front page of the report. Please note title page, front cover sheets, tables of content, captions, references and appendix are excluded from word count.

Please make sure to include all relevant references in text using USW Harvard Referencing. The guide to this referencing method can be found within the “Assessment Information” tab on the Blackboard module page.