INTERNATIONAL INSTITUTE FOR AEROSPACE
ENGINEERING AND MANAGEMENT
Jain Global Campus
Jakkasandra Post, Kanakapura Taluk, Ramanagara District - Pin Code: 562 112
Department of Aerospace Engineering
US N
B.Tech.4thSem
TEST - III
Subject Name: Thermal Science Session:Jan – June 2021
Subject Code: 18AS41 (Common for ASE & ANE) Duration: 90 Minutes
Date of Examination: 7th June 2021 Max Marks: 9 X 10 = 90
Note:
✓ Answer all questions and each question carries 10 Marks.
✓ Provide neat diagrams, assumptions and units & conversions wherever applicable.
Bloom’s
Q.No Question Marks COs
Level
Consider a 1.2-m-high and 2-m-wide glass window whose thickness is 6 mm and thermal
conductivity is k = 0.78 W/m·K. Determine the steady rate of heat transfer through this
glass window and the temperature of its inner surface for a day during which the room is
1. 10 CO5 L4
maintained at 24°C while the temperature of the outdoors is 25°C. Take the convection
heat transfer coefficients on the inner and outer surfaces of the window to be h 1 = 10
W/m2·K and h2 = 25 W/m2·K, and disregard any heat transfer by radiation.
A thin electronic component with a surface area of 950 cm2 is cooled by having a heat
sink attached on its top surface. The thermal contact conductance of the interface between
the electronic component and the heat sink is 25,000 W/m2∙K. According to the
manufacturer, the heat sink has combined convection and radiation thermal resistance of
2. 10 CO5 L4
1.3 K/W. If the electronic component dissipates 45 W of heat through the heat sink in a
surrounding temperature of 30°C, determine the temperature of the electronic
component. Does the contact resistance at the interface of the electronic component and
the heat sink play a significant role in the heat dissipation?
A 2.2-mm-diameter and 10-m-long electric wire is tightly wrapped with a 1-mm-thick
plastic cover whose thermal conductivity is k = 0.15 W/m·K. Electrical measurements
indicate that a current of 13 A passes through the wire and there is a voltage drop of 8 V
along the wire. If the insulated wire is exposed to a medium at T`= 30°C with a heat
3. transfer coefficient of h = 24 W/m2·K. 10 CO5 L4
Determine the temperature at the interface of the
wire and the plastic cover in steady operation.
Also determine if doubling the thickness of the
plastic cover will increase or decrease this
interface Temperature.
A 5-mm-diameter spherical ball at 50°C is covered by a 1-
mm-thick plastic insulation (k = 0.13 W/m·K). The ball is
4. exposed to a medium at 15°C, with a combined convection 10 CO5 L4
and radiation heat transfer coefficient of 20 W/m2·K.
Determine if the plastic insulation on the ball will help or hurt
heat transfer from the ball.
Explain the Velocity Boundary Layer for the flow over flat plates. Also Explain the
5. 10 CO6 L4
Thermal Boundary Layer with neat diagram and define various regions of flow
Page 1 of 2
ENGINEERING AND MANAGEMENT
Jain Global Campus
Jakkasandra Post, Kanakapura Taluk, Ramanagara District - Pin Code: 562 112
Department of Aerospace Engineering
US N
B.Tech.4thSem
TEST - III
Subject Name: Thermal Science Session:Jan – June 2021
Subject Code: 18AS41 (Common for ASE & ANE) Duration: 90 Minutes
Date of Examination: 7th June 2021 Max Marks: 9 X 10 = 90
Note:
✓ Answer all questions and each question carries 10 Marks.
✓ Provide neat diagrams, assumptions and units & conversions wherever applicable.
Bloom’s
Q.No Question Marks COs
Level
Consider a 1.2-m-high and 2-m-wide glass window whose thickness is 6 mm and thermal
conductivity is k = 0.78 W/m·K. Determine the steady rate of heat transfer through this
glass window and the temperature of its inner surface for a day during which the room is
1. 10 CO5 L4
maintained at 24°C while the temperature of the outdoors is 25°C. Take the convection
heat transfer coefficients on the inner and outer surfaces of the window to be h 1 = 10
W/m2·K and h2 = 25 W/m2·K, and disregard any heat transfer by radiation.
A thin electronic component with a surface area of 950 cm2 is cooled by having a heat
sink attached on its top surface. The thermal contact conductance of the interface between
the electronic component and the heat sink is 25,000 W/m2∙K. According to the
manufacturer, the heat sink has combined convection and radiation thermal resistance of
2. 10 CO5 L4
1.3 K/W. If the electronic component dissipates 45 W of heat through the heat sink in a
surrounding temperature of 30°C, determine the temperature of the electronic
component. Does the contact resistance at the interface of the electronic component and
the heat sink play a significant role in the heat dissipation?
A 2.2-mm-diameter and 10-m-long electric wire is tightly wrapped with a 1-mm-thick
plastic cover whose thermal conductivity is k = 0.15 W/m·K. Electrical measurements
indicate that a current of 13 A passes through the wire and there is a voltage drop of 8 V
along the wire. If the insulated wire is exposed to a medium at T`= 30°C with a heat
3. transfer coefficient of h = 24 W/m2·K. 10 CO5 L4
Determine the temperature at the interface of the
wire and the plastic cover in steady operation.
Also determine if doubling the thickness of the
plastic cover will increase or decrease this
interface Temperature.
A 5-mm-diameter spherical ball at 50°C is covered by a 1-
mm-thick plastic insulation (k = 0.13 W/m·K). The ball is
4. exposed to a medium at 15°C, with a combined convection 10 CO5 L4
and radiation heat transfer coefficient of 20 W/m2·K.
Determine if the plastic insulation on the ball will help or hurt
heat transfer from the ball.
Explain the Velocity Boundary Layer for the flow over flat plates. Also Explain the
5. 10 CO6 L4
Thermal Boundary Layer with neat diagram and define various regions of flow
Page 1 of 2
