This lab will look into the heat transfer between two streams of water at different temperatures that flow inside a tube-in-tube heat exchanger. The lab touches four heat exchanger tubes in total. Despite the fact that the experimental analysis's goal was met, some mistakes in the data collected were discovered. Specifically, the lab achieved an overall efficiency of 67.5%. Overall, the increase in flowrate resulted in a decrease in temperature. By definition, a heat exchanger refers to a device of transferring heat whose purpose is the energy transfer from one moving stream of fluid to another (Becker 1993; Lederer 1982). It one of the most common of the devices of transferring heat (Sugunan and Paul 1998). Examples of heat transfer include the radiator of the car and the units of condenser on the systems of air conditioning (Khullar and Tyagi 2017). Both the thermodynamics and the first law play a significant role in dictating the overall transfer of energy (Patel and Mehta 2017). A control volume is considered when performing the analysis of the thermodynamics on a heat exchanger (Deitrich 2011; Reimers and Hush 1989).
Figure 1: The Model of Control Volume (Source: Fronk and Rattner 2016).
Even though heat is transferred from the hot stream of the fluid to the cold stream of the fluid, there is not heat or work being transferred from the control volume to the surroundings (Lakew and Bolland 2010). For this reason, the first law of the kind of system becomes: H in = H out (Eriksson 1988; Khan 1981). Notably, there are a total of two flows out of the control volume and two flows into the control volume (Melo and Bott 1997). For many exchangers of heat, there is not a change of phase that occurs for either stream of fluid. In this case, the fluids are either ideal gases or incompressible liquids (Hoare and Waters 1962). Under such conditions, the enthalpies can be represented in terms of temperature by the use of the proper equation of state which helps in the introduction of the specific heat (Liu and Huan 1995; Vorberger and Gericke 2014).
Unfortunately, the whole story of the performance of the heat exchanger is not tole by the thermodynamics (Faiman 1980; Littler and Waters 1959). However, the principles of the conduction and convection of the transfer of heat is applicable in trying to achieve the transfer of energy that the first law predicts (Cova 1960; Lister 1996). The application of these principles first involves the consideration of a very small heat exchanger’s length (Kudinovich and Syraleva 2017; Morlock 2015). For the processes of the heat transfer to be at work, there has to be the convective transfer of heat from the surface of the wall to the cold fluid in the first place (Ishibashi 1988; Shekhter 2006). The use of the thermal conduit model helps in the modeling of the series of the process of heat transfer (Becker and Beattie 1982; TKiatsiriroat 2000).
Methods
In the first place, the number of the active tube in the software was selected in the “number of tubes” box on the left. Subsequently, the cold-water flow rate was set according to 0.25 by adjusting the arrows on the cold-water rate display box’s side. Afterward, the cold-water inlet temperature T6 was checked. Also, the hot water temperature controller was set to a point approximately 300C above the cold-water inlet temperature. To close the window, the “apply” was clicked before clicking the “OK”. Furthermore, the hot water flow was set to 1 L/min after which the “flow” was clicked in the controller box.
Figure 2: The HT30XC Schematic Diagram
The “Automatic” was then selected in the controller window’s top right. At this point, the window was closed to allow the heat to stabilize. On the top toolbar, the “Go” icon was selected to record the data after stabilizing the temperature. After recording all the values of the temperatures, the cold-water control valve was adjusted to give 0.5 L/min by the use of the arrow buttons on the display box’ side. The new icon was then used for creating new results. This process was repeated by selecting the “Go” icon. Moreover, other combinations of the cold and hot flow rates were investigated as per the design of the experiment. Finally, an excel sheet was used to save all the data.
Results
Table 1: Results of Heat Exchanger for One Tube
No.
of
tubes
Temperature in 0C
Hot water pump setting (%)
Hot water flowrate F hot 1/min
Cold water valve setting (%)
Cold water flowrate F cold 1/min
Hot water flowrate -m3/s
Cold water flowrate -m3/s
T1 0C
T2 0C
T3 0C
T4 0C
T5 0C
T6 0C
T7 0C
T8 0C
T9 0C
T10 0C
1
50.7
49.5
48.5
48.5
47.3
20.8
28.6
38.5
20.0
48.2
14
1.0
34
0.24
1.6 E-05
4.1 E-05
1
49.7
45.4
44.5
44.5
43.7
20.8
29.1
37.6
19.5
33.8
14
1.1
40
0.46
1.8 E-05
7.7 E-05
1
49.7
43.1
43.1
43.7
42.5
20.8
28.6
36.6
19.1
24.9
14
1.0
60
1.15
1.7 E-05
1.9 E-05
1
49.8
43.2
42.0
41.9
41.0
20.8
27.9
35.3
18.7
21.8
14
1.0
100
1.78
1.7 E-05
2.9 E-05
1
50.9
50.9
50.2
50.4
49.6
20.8
28.8
38.1
19.2
47.2
27
2.1
34
0.22
3.5 E-05
3.7 E-05
1
50.6
50.7
49.9
50.2
49.5
20.8
29.5
38.2
19.3
47.5
28
2.0
34
0.57
3.3 E-05
9.6 E-05
1
49.6
45.7
44.9
45.0
44.3
20.7
29.5
38.2
18.9
25.6
28
1.9
60
0.89
3.1 E-05
1.5 E-05
1
49.6
44.9
44.1
44.3
43.9
20.8
29.1
37.8
18.6
23.6
27
2.2
100
1.45
3.7 E-05
2.4 E-05
1
51.3
51.5
50.8
51.0
50.4
20.8
30.1
41.8
19.1
48.0
40
2.6
34
0.22
4.3 E-05
3.7 E-05
1
51.0
51.2
50.6
50.8
50.2
20.8
30.6
42.0
19.1
48.0
41
3.0
34
0.45
5.0 E-05
7.5 E-05
1
49.1
46.4
45.7
45.9
45.4
20.9
30.7
39.8
18.8
27.6
42
2.9
60
1.03
4.9 E-05
1.7 E-05
1
49.4
46.6
46.0
46.2
45.7
20.8
30.4
39.5
18.8
27.4
44
2.9
60
1.45
4.8 E-05
2.4 E-05
Av.
50.1
47.4
46.7
46.9
46.1
20.8
29.4
38.6
19.1
35.3
SD
0.74
3.17
3.16
3.18
3.22
0.04
0.88
1.94
0.38
11.4
Table 2: Results of Heat Exchanger for Two Tubes
No.
of
tubes
Temperature in 0C
Hot water pump setting (%)
Hot water flowrate F hot 1/min
Cold water valve setting (%)
Cold water flowrate F cold 1/min
Hot water flowrate -m3/s
Cold water flowrate -m3/s
T1 0C
T2 0C
T3 0C
T4 0C
T5 0C
T6 0C
T7 0C
T8 0C
T9 0C
T10 0C
2
50.7
51.3
48.9
49.0
48.1
20.7
29.9
20.6
47.9
48.7
14
1.0
34
0.24
1.6 E-05
4.1 E-05
2
49.7
47.1
42.0
42.0
41.4
20.9
28.7
19.3
31.6
40.6
14
1.1
40
0.55
1.6 E-05
9.2 E-05
2
49.6
44.8
38.2
38.3
37.5
20.9
27.5
18.8
23.2
27.0
14
1.0
60
1.10
1.7 E-05
1.8 E-05
2
49.8
42.9
36.6
37.0
36.5
20.8
26.1
18.5
21.4
24.5
14
1.0
100
1.57
1.7 E-05
2.6 E-05
2
49.8
49.3
45.8
45.9
45.2
20.7
29.8
19.3
36.7
44.2
29
2.0
40
0.23
3.3 E-05
3.9 E-05
2
50.9
51.2
48.9
49.1
48.5
20.7
30.5
19.4
45.6
49.6
29
1.9
34
0.54
3.1 E-05
8.9 E-05
2
49.7
46.8
41.9
42.1
41.5
20.8
28.3
18.7
26.2
32.1
28
2.1
60
1.09
3.5 E-05
1.8 E-05
2
49.8
46.2
40.8
40.8
40.0
20.7
27.3
18.4
24.0
28.2
29
2.0
100
1.60
3.4 E-05
2.7 E-05
2
49.9
49.5
46.8
47.0
46.4
20.7
30.5
19.4
37.6
45.0
40
3.4
40
0.21
5.7 E-05
3.5 E-05
2
50.9
51.4
50.0
50.2
49.7
20.7
30.8
19.4
46.5
49.6
43
3.0
34
0.57
5.0 E-05
9.6 E-05
2
49.7
47.9
44.1
44.3
43.7
20.7
29.1
18.7
27.6
34.3
42
3.0
60
0.99
5.0 E-05
1.6 E-05
2
49.9
47.2
43.0
43.2
42.6
20.7
28.3
18.4
25.2
30.7
42
3.1
100
1.54
5.1 E-05
2.6 E-05
0.49
2.68
4.31
4.29
4.29
0.08
1.47
0.63
9.74
9.43
11.86
0.921
26.97
0.533
Table 1: Results of Heat Exchanger for Three Tubes
No.
of
tubes
Temperature in 0C
Hot water pump setting (%)
Hot water flowrate F hot 1/min
Cold water valve setting (%)
Cold water flowrate F cold 1/min
Hot water flowrate -m3/s
Cold water flowrate -m3/s
T1 0C
T2 0C
T3 0C
T4 0C
T5 0C
T6 0C
T7 0C
T8 0C
T9 0C
T10 0C
3
51.8
51.8
49.2
46.9
46.1
21.0
18.4
36.5
45.7
49.5
14
1.0
34
0.27
1.6 E-05
4.5 E-05
3
49.5
47.0
42.9
39.3
38.9
21.1
18.4
26.0
32.6
38.5
14
1.1
40
0.57
1.7 E-05
9.6 E-05
3
49.6
44.9
39.3
35.0
34.7
21.1
18.1
22.2
26.3
30.4
14
1.0
60
1.09
1.8 E-05
1.8 E-05
3
49.7
44.4
38.1
34.0
33.3
20.1
17.9
20.8
23.9
27.1
14
1.0
100
1.60
1.7 E-05
2.7 E-05
3
50.7
52.2
51.1
49.9
49.0
20.1
18.2
42.5
47.9
49.4
26
2.3
34
0.24
3.8 E-05
4.0 E-05
3
49.6
49.6
47.5
45.5
44.9
20.2
18.6
33.6
43.4
47.3
28
1.8
40
0.43
3.0 E-05
7.1 E-05
3
49.6
46.8
42.8
39.6
39.1
20.2
18.1
24.8
31.1
35.9
28
2.0
60
1.10
3.3 E-05
1.8 E-05
3
49.6
46.1
41.6
38.3
37.7
20.2
18.0
22.8
27.7
31.4
29
2.1
100
1.53
3.4 E-05
2.5 E-05
3
51.3
51.5
49.9
48.3
47.7
20.1
18.5
35.8
45.4
49.0
41
3.0
34
0.29
5.0 E-05
4.9 E-05
3
50.8
51.0
49.6
48.0
47.4
20.3
18.9
37.4
46.0
491
41
3.2
34
0.54
5.3 E-05
8.9 E-05
3
47.9
46.6
43.7
41.1
40.8
20.8
18.4
26.3
32.9
38.0
42
2.8
60
1.15
4.7 E-05
1.9 E-05
3
48.7
46.8
43.2
40.3
39.7
20.9
18.0
24.4
30.2
34.8
42
3.0
100
1.49
4.9 E-05
2.5 E-05
SD
1.24
2.82
4.43
5.37
5.27
0.36
0.29
7.26
8.88
8.42
11.74
0.847
Table 1: Results of Heat Exchanger for Four Tubes
No.
of
tubes
Temperature in 0C
Hot water pump setting (%)
Hot water flowrate F hot 1/min
Cold water valve setting (%)
Cold water flowrate F cold 1/min
Hot water flowrate -m3/s
Area hot
T1 0C
T2 0C
T3 0C
T4 0C
T5 0C
T6 0C
T7 0C
T8 0C
T9 0C
T10 0C
4
49.9
50.2
49.0
48.1
43.8
19.5
38.6
45.0
47.6
48.6
13.8
0
34.0
0
2.7 E-05
5.4 E-05
4
49.6
48.1
45.1
42.4
37.7
19.3
27.0
33.6
38.3
42.5
14.0
0
40.0
0
5.5 E-05
5.4 E-05
4
49.5
45.0
39.9
36.3
31.9
18.7
21.3
25.0
28.7
32.6
14.0
0
60.0
0
8.4 E-05
5.4 E-05
4
49.5
44.3
38.8
35.0
30.2
18.5
20.1
23.1
26.0
29.2
14.1
0
100.0
0
5.4 E-05
5.4 E-05
4
50.0
50.5
49.8
49.7
47.4
19.5
43.8
47.8
49.1
49.3
27.4
0
34.0
0
8.2 E-05
5.4 E-05
4
50.4
50.7
49.6
49.2
46.2
19.2
38.5
44.4
48.0
49.5
27.1
0
37.0
0
2.8 E-05
5.4 E-05
4
50.2
48.1
45.5
43.1
39.0
18.5
26.5
33.4
38.5
42.1
27.4
0
52.0
0
5.6 E-05
5.4 E-05
4
49.4
47.0
43.0
40.0
36.1
18.3
22.7
27.7
32.5
36.4
27.9
0
87.0
0
2.8 E-05
5.4 E-05
4
50.2
50.8
50.1
50.2
48.6
19.4
46.0
48.4
49.5
49.6
40.6
0
34.0
0
8.6 E-05
5.4 E-05
4
50.9
51.3
50.2
49.5
46.4
18.6
37.2
44.5
48.4
49.8
41.0
0
40.0
0
5.5 E-05
5.4 E-05
4
49.1
48.5
46.3
44.3
40.8
18.4
27.1
33.9
39.0
42.4
41.1
0
63.0
0
8.4 E-05
5.4 E-05
4
48.6
47.4
44.6
42.3
38.8
18.3
24.4
30.3
35.3
39.0
41.7
0
95.0
0.0
2.7 E-05
5.4 E-05
Av.
49.7
48.5
45.9
44.2
40.6
18.8
31.1
36.4
40.1
42.6
27.5
56.3
SD
0.63
2.31
3.95
5.29
6.06
0.48
9.14
9.15
8.39
7.14
Analysis and Discussion
The reduction in the temperature of the hot fluid = Thot= T1-T5 (°C) = 50.1 – 46.1 = 40C. (for tube one). For tube four, the temperature reduced by 49.69-40.58 = 9.110C.
Again, the cold temperature increased by Tcold= T10-T6 (°C) = 35.3-20.8 = 14.50C. It is observed that the temperature reduces as the flowrate increases (Radulovic 2016).
Figure 3: A Graph of the Change in Temperature versus Change in Flowrate (Source: Wells and Husain 1970).
Different number of tubes produce various cold and hot flowrates (Ismail and Marzouk 1996). For the hot water, the temperature efficiency = (T1-T5)/ (T1-T6) x 100 = (50.1 – 46.1)/ (50.1 – 42.8) x 100 = 48.2%
For the cold fluid, the temperature efficiency = (T6-T10)/ (T1-T6) x 100 = (20.8-27.4)/ (49.4-41.8) = 6.6/7.6 x 100 = 86.8%
The overall temperature efficiency = (48.2 + 86.8)/ 2 = 67.5%.
In general, the difference between the Qa and Qe results from the losses in the pipe (Naresh and Balaji 2017).
The mean temperature efficiency = (efficiency of the hot temperature + the efficiency of the cold temperature)/ 2 = (48.2 + 86.8)/ 2 = 67.5%.
LMTD= Where, = ;
= (49.4-27.4)/ ln (49.4/27.4) = 22/ ln1.8 = 8.1
The arithmetic mean diameter = (m) = (0.635-0.515)/ 2 = 0.38 m
The laminar flowrate increases up to a certain point before reducing through the annulus (Billing 1983; Porous Element Heating 1984). In this case, the G = -dp/ dx = constant (Bahi and Dreyer 2012; Yataghene and Legrand 2013). Different lengths of the heat exchanger produce various flowrates (Office 2015). Larger lengths mean higher head losses hence a reduction in the flow rate (Koch and Ehlers 2013). The slight differences between the theoretical and the experimental values are caused by the presence of errors (Garon 1973). Lengthy calculations are one of the possible sources of discrepancies (Fridman 2004). Also, all the equipment must be ensured to work properly to reduce the chances of error in the experimental values (Hansen 1965; Roth 1993; Somerscales 1992).
Conclusions
This lab managed to achieve its primary goal of investigating the transfer of heat between water’s two streams of different temperatures that flows inside a tube-in-tube exchanger of heat. Different heat exchanger tubes are evident to produce different rate of flow of water. Some errors might have played a significant role of reducing the overall efficiency of the lab (67.5%). However, the possibility of reducing such errors is by taking note of the significant figures as well as ensuring that all the apparatuses work effectively.
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