HEAT TRANSFER 2018 Question Paper — Government College of Engineering…
The 2018 HEAT TRANSFER previous year question paper (Government College of Engineering and Technology, Jammu), with every question and its marks.
- University: Government College of Engineering and Technology, Jammu
- Subject: HEAT TRANSFER
- Course: Heat Transfer
- Branch: MECHANICAL ENGINEERING
- Year: 2018
- Paper: end-term
- Duration: 180 minutes
- Total marks: 100
Instructions
- Attempt five questions in all selecting at least two questions from each Section.
- Each question carries 20 marks.
- Assume suitable missing data, if required.
- Use of scientific calculator is allowed.
Questions
SECTION-A
- QQ1. (a) A furnace wall is made of composite wall of total thickness 550mm. The inside layer is made of refractory material ($K = 2.3 \text{ W/mK}$) and outside layer is made of an insulating material ($K = 0.2 \text{ W/m-K}$). The mean temperature of the glass inside the furnace is $900^{\circ}\text{C}$ and interface temperature is $520^{\circ}\text{C}$. The heat transfer coefficient between the gases and the inner surface is taken as $230 \text{ W/m}^2\text{C}$ and between the outside surface and atmosphere as $46 \text{ W/m}^2\text{C}$. Taking air temperature as $30^{\circ}\text{C}$, calculate (i) required thickness of each layer, (ii) the rate of heat loss per square meter area. [20] (b) [Missing part label, or continuation of Q1 or general instruction, but printed as Q2(a)] [20 marks]
- QQ2. (a) Derive the General differential equation of heat conduction in Cartesian coordinates? [12] (b) Distinguish between the fin effectiveness and the fin efficiency? [8] [20 marks]
- QQ3. (a) Steam in a heating system flows through tubes whose outer diameter is $D_1 = 3 \text{ cm}$ and whose walls are maintained at a temperature of $120^{\circ}\text{C}$. Circular aluminum fins ($k = 180 \text{ W/m }^{\circ}\text{C}$) of outer diameter $D_2 = 6 \text{ cm}$ and constant thickness $t = 2 \text{ mm}$ are attached to the tube. The space between the fins is $3 \text{ mm}$, and thus there are 200 fins per meter length of the tube. Heat is transferred to the surrounding air at $T_{\infty} = 25^{\circ}\text{C}$, with a combined heat transfer coefficient of $h = 60 \text{ W/m}^2\text{ }^{\circ}\text{C}$. Determine the increase in heat transfer from the tube per meter of its length as a result of adding fins. [10] (b) Explain how fins can increase the rate of heat transfer. Mention the most common types of fins and sketch them. Give some practical examples of fins. [10] [20 ma…
- QQ4. (a) Two parallel plates of size $1 \text{ m}$ by $1 \text{ m}$ spaced $0.5 \text{ m}$ apart are located in a very large room, the walls of which are maintained at temperature of $27^{\circ}\text{C}$. One plate is maintained at temperature of $900^{\circ}\text{C}$ and other at $400^{\circ}\text{C}$. Their emissivities are $0.2$ and $0.5$ respectively. If the plates exchange heat between themselves and surroundings, find the net heat transfer to each plate and to room. Consider only the plate surfaces facing each other? [14] (b) What is meant by absorptivity, reflectivity and transmissivity? [6] [20 marks]
SECTION-B
- QQ5. (a) A counter flow double-pipe heat exchanger is used to heat from $20^{\circ}\text{C}$ to $40^{\circ}\text{C}$ by cooling oil from $90^{\circ}\text{C}$ to $55^{\circ}\text{C}$. The heat exchanger is designed for a total heat transfer of $59 \text{ KW}$ with an overall heat transfer coefficient of $340 \text{ W/m}^2\text{ }^{\circ}\text{C}$. Calculate surface area of heat exchanger? [12] (b) Explain about fouling factors? [8] [20 marks]
- QQ6. The door of an industrial furnace is $2 \text{ m} \times 4 \text{ m}$ in surface and is to be insulated to reduce the heat loss to not more than $1200 \text{ W/m}^2$. The interior and exterior walls of the door are $10\text{mm}$, $7\text{mm}$ thick steel sheets ($k = 25 \text{ W/m K}$). Between these two sheets, suitable thickness of insulation material is to be placed. The effective gas temperature inside the furnace is $1200^{\circ}\text{C}$ and overall heat transfer coefficient between the gas and door is $20 \text{ W/m}^2\text{K}$. The heat transfer coefficient outside the door is $5 \text{ W/m}^2\text{ }^{\circ}\text{C}$. The surrounding air temperature is $20^{\circ}\text{C}$. Select suitable insulation material and its size? [20] [20 marks]
- QQ7. (a) Explain the various regions of flow boiling in detail. [10] (b) The outer surface of a vertical tube, which is $1\text{m}$ long and has an outer diameter of $80\text{mm}$, is exposed to saturated steam at atmospheric pressure and is maintained at $50^{\circ}\text{C}$ by the flow of cool water through the tube. What is the rate of heat transfer to coolant and what is the rate at which steam is condensed at the surface. [10] [20 marks]
- QQ8. Write a Short notes on ($2*10=20$) (a) Thermal boundary layer (b) Log mean temperature difference [20 marks]