Example

A fully mixed water storage tank contains 500 kg of water, has a UA product equal to 12 W/°C, and is located in a room that is at a constant temperature of 20°C. The tank is examined in a 10 h period starting from 5 am where the Qu is equal to 0, 0, 0, 10, 21, 30, 40, 55, 65, 55 MJ. The load is constant and equal to 12 MJ in the first 3 h, 15 MJ in the next 3 h, and 25 MJ the rest of time. Find the final storage tank temperature if the initial temperature is 45°C.

Solution

The estimation time interval is 1 h. Using Eq. (5.34) and inserting the appropriate constants, we get

By inserting the initial storage tank temperature (45°C), Qu, and Ql according to the problem, Table 5.3 can be obtained.

Table 5.3 Results for Example 5.2

Hour

Qu (MJ)

Qi (MJ)

Ts (0C)

Qtl (MJ)

45

5

0

12

38.7

1.1

6

0

12

32.6

0.8

7

0

12

26.6

0.5

8

10

15

24.1

0.3

9

21

15

26.9

0.2

10

30

15

33.9

0.3

11

40

25

40.8

0.6

12

55

25

54.7

0.9

13

65

25

73.1

1.5

14

55

25

86.4

2.3

Therefore, the final storage tank temperature is 86.4°C. For these calculations, the use of a spreadsheet program is recommended.

The collector performance equations in Chapter 4 can also be used with the more detailed determination of inlet fluid temperature to estimate the daily energy output from the collector. This is illustrated by the following example.

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Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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