NSC Mechanical Technology Welding and Metalwork Developments and templates: 11.1 Describe the function of tr

Question

11.1 Describe the function of transformers used in ventilation ducts.

Transformers are used to connect ducting sections of dissimilar shapes to ensure a smooth transition of airflow. They help in maintaining air velocity and pressure by providing a gradual change in the cross-sectional area of the duct. This reduces turbulence and promotes efficient air distribution.

11.2 Use freehand sketches to indicate the difference between an on-centred hopper and an off-centred hopper.

*On-centred hopper sketch*

*Off-centred hopper sketch*

11.3 FIGURE 11.3 below shows a truncated cone.

Calculate the following:

11.3.1 Base circumference:

The circumference of the base can be calculated using the formula:

$$C = 	ext{Base diameter} 	imes rac{	ext{π}}{1000}$$

Where the base diameter is 1400 mm.

Thus,

$$C = 1400 	imes rac{3.14159}{1000} = 4398.23 	ext{ mm}$$

11.3.2 Main radius (AC):

To find the main radius, we recognize that triangles ABC and CED are similar:

$$rac{AC}{DC} = rac{BC}{EC}$$

Where:

- Base Diameter = 800 mm
- Thus, we can express EC as:

$$EC = rac{1400 - 800}{2} = 300 	ext{ mm}$$

Using the values to find DC:

$$DC^2 = DC^2 + CE^2$$
$$DC = 	ext{sqrt}(1200^2 + 300^2)$$

Calculating DC gives:
$$DC 	ext{ rounded } = 1237 	ext{ mm}$$

Now, substituting in to find AC:
$$AC = rac{BC 	imes DC}{EC}$$
$$AC = rac{700 	imes 1237}{300}$$
Thus,
$$AC 	ext{ rounded } = 2886 	ext{ mm}$$

11.3.3 Small radius (AD):

To find the small radius, we compute:

$$AD = AC - DC$$

Thus,
$$AD = 2886 - 1237 = 1649 	ext{ mm}$$

11.1 Describe the function of transformers used in ventilation ducts - NSC Mechanical Technology Welding and Metalwork - Question 11 - 2018 - Paper 1

Worked Solution & Example Answer:11.1 Describe the function of transformers used in ventilation ducts - NSC Mechanical Technology Welding and Metalwork - Question 11 - 2018 - Paper 1

Describe the function of transformers used in ventilation ducts.

Use freehand sketches to indicate the difference between an on-centred hopper and an off-centred hopper.

Base circumference:

Main radius (AC):

Small radius (AD):

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