ASSESSMENT
COVER PAGE
FACULTY: ENGINEERING
DEPARTMENT MECHANICAL SEMESTER 1
QUALIFICATION (S) CODE (S)
NAME ADVANCE DIPLOMA AdvDMCHE
SUBJECT (S) NAME CODE (S)
HEAT TRANSFER HTR470S/HTR471S
NO OF PAGES DATE 25-Mar-24 TIME 17:30
(Including cover page)
ANNEXURE (S) 1 DURATION 3 hours
COLOUR IMAGES (Y/N) N
EXAMINER NAME Mr.C Magoda/ Prof. T Ngonda
INTERNAL MODERATOR P Senda
EXTERNAL MODERATOR C Tshamala
INSTRUCTIONS (to AGC, students, invigilators, etc)
REQUIREMENTS (e.g. 2 answer books, etc)
FOR STUDENT IN THE FACULTY OF ENGINEERING & THE BUILT ENVIRONMENT
- Answer All questions and in sequence.
- Indicate if the assessment is a closed or open book assessment.
- Only pens with permanent ink may be used when answering questions. Pencils may be used in instances
where diagrams and sketches are required.
- Return your Question Paper with your Answer Book.
- Graduate Attribute (GA): No GA assessment for this Subject.
DO NOT turn the page over before the starting
time
1
, Question 1 (20 Marks)
1.1 A steam pipe in the Thermodynamics lab at (CPUT_Mech Eng) has the following
specifications.
Length of pipe 20 m
Internal diameter 8 cm
Outer diameter 10 cm
Thermal conductivity (k) 30 W/m. ͦC
Inner Temperature 200 0C
Outer Temperature 100 0C
1.1.1 Derive a mathematical expression for the temperature distribution inside the pipe
(assume steady state conditions and one dimension heat conduction).
[7]
1.1.2 Calculate the rate of heat transfer across the pipe thickness. [3]
1.2 Saturated steam at 200 0C flows through the above-mentioned pipe. The pipe is
covered by a 5 cm-thick layer of insulation material (k = 0.073 W/m. K). Compare the
heat loss from the insulated pipe to that of a bare pipe per unit length when the
ambient air temperature is 20 °C. Take the outside heat transfer coefficients of 8 and
6 W/m2.K for the bare and insulated pipe respectively.
[10]
Question 2 (20 Marks)
At the exit of the building, the steam in pipe mentioned in question 1 is to be cooled. The
student considered a pipe length of 10 m and suggested to attach Circular aluminium fins (k
= 200 W/m °C) of outer diameter D2=15 cm and constant thickness t = 5 mm. The space
between the fins is 8 mm, and 200 fins per meter length of the pipe were attached. Heat is
transferred to the surrounding air at T = 20°C, with a combined heat transfer coefficient of h
= 60 W/m2°C. Determine the increase in heat transfer from the tube per meter of its length
because of adding fins.
2
COVER PAGE
FACULTY: ENGINEERING
DEPARTMENT MECHANICAL SEMESTER 1
QUALIFICATION (S) CODE (S)
NAME ADVANCE DIPLOMA AdvDMCHE
SUBJECT (S) NAME CODE (S)
HEAT TRANSFER HTR470S/HTR471S
NO OF PAGES DATE 25-Mar-24 TIME 17:30
(Including cover page)
ANNEXURE (S) 1 DURATION 3 hours
COLOUR IMAGES (Y/N) N
EXAMINER NAME Mr.C Magoda/ Prof. T Ngonda
INTERNAL MODERATOR P Senda
EXTERNAL MODERATOR C Tshamala
INSTRUCTIONS (to AGC, students, invigilators, etc)
REQUIREMENTS (e.g. 2 answer books, etc)
FOR STUDENT IN THE FACULTY OF ENGINEERING & THE BUILT ENVIRONMENT
- Answer All questions and in sequence.
- Indicate if the assessment is a closed or open book assessment.
- Only pens with permanent ink may be used when answering questions. Pencils may be used in instances
where diagrams and sketches are required.
- Return your Question Paper with your Answer Book.
- Graduate Attribute (GA): No GA assessment for this Subject.
DO NOT turn the page over before the starting
time
1
, Question 1 (20 Marks)
1.1 A steam pipe in the Thermodynamics lab at (CPUT_Mech Eng) has the following
specifications.
Length of pipe 20 m
Internal diameter 8 cm
Outer diameter 10 cm
Thermal conductivity (k) 30 W/m. ͦC
Inner Temperature 200 0C
Outer Temperature 100 0C
1.1.1 Derive a mathematical expression for the temperature distribution inside the pipe
(assume steady state conditions and one dimension heat conduction).
[7]
1.1.2 Calculate the rate of heat transfer across the pipe thickness. [3]
1.2 Saturated steam at 200 0C flows through the above-mentioned pipe. The pipe is
covered by a 5 cm-thick layer of insulation material (k = 0.073 W/m. K). Compare the
heat loss from the insulated pipe to that of a bare pipe per unit length when the
ambient air temperature is 20 °C. Take the outside heat transfer coefficients of 8 and
6 W/m2.K for the bare and insulated pipe respectively.
[10]
Question 2 (20 Marks)
At the exit of the building, the steam in pipe mentioned in question 1 is to be cooled. The
student considered a pipe length of 10 m and suggested to attach Circular aluminium fins (k
= 200 W/m °C) of outer diameter D2=15 cm and constant thickness t = 5 mm. The space
between the fins is 8 mm, and 200 fins per meter length of the pipe were attached. Heat is
transferred to the surrounding air at T = 20°C, with a combined heat transfer coefficient of h
= 60 W/m2°C. Determine the increase in heat transfer from the tube per meter of its length
because of adding fins.
2
