# Past Papers Chemical Process Heat Transfer

## Guess Paper 1: Chemical Process Heat Transfer Fall – 2020 Past Papers

University Name – Confidential

Time Allowed: 3 hours

Total Marks:    70, Passing Marks (35)

Q.1 Derive heat conduction equation for the sphere in detail.

Q.2 Discuss the perfect black body. Also derive Stephan Boltzman Law.

Q.3 Derive an equation for the critical thickness of insulation.

Q.4 A hot plate at a temperature of 350 ⁰C having the emissivity of two-third as that of ideal condition. If the surrounding temperature is 25 ⁰C. Calculate the heat flux.

Q.5 Design of a two-pass, shell-and-tube heat exchanger to supply vapor for the turbine of an ocean thermal energy conversion system based on a standard (Rankine) power cycle. The power cycle is to generate 2 MW at an efficiency of 3%. Ocean water enters the tubes of the exchanger at 300 K, and its desired outlet temperature is 292K. The working fluid of the power cycle is evaporated in the tubes of the exchanger at its phase change temperature of 290K, and the overall heat transfer coefficient is known to be 1200 W/ m2K. Calculate the evaporator area.

Q.6 Water entering a shell-and-tube heat exchanger is at 35 ºC is to be heated to 75 ºC by oil. The oil enters at 110 ºC and leaves at 75 ºC. The heat exchanger is arranged for counterflow with water making one shell pass and the oil two tube passes. If the water flow rate is 68 kg/min and the overall heat transfer coefficient is estimated from Table 8.1 to be 320 W/m2-K, calculate the required heat exchanger area.

Q.7 Discuss types of heat exchangers in detail.

Q 8. The inner and outer surface temperatures of a glass window 5 mm thick are 15 and 5°C, respectively. What is the heat flux through a window that is 1 m by 3 m on a side? The thermal conductivity of glass is 1.4 W/m.K.

## Guess Paper 2: Chemical Process Heat Transfer Spring – 2020 Past Papers

University Name – Confidential

Time Allowed: 3 hours

Total Marks:    70, Passing Marks (35)

Q.1 Derive heat conduction equation for cylindrical coordinates in detail.

Q.2 Discuss convection and its types with examples.

Q.3 Discuss shell and tube heat exchanger. Also, draw the schematic of 2-4 shell and tube heat exchanger.

Q.4 A hot plate at a temperature of 350 ⁰C having the emissivity of two-third as that of ideal condition. If the surrounding temperature is 25 ⁰C. Calculate the heat flux.

Q.5 Hot fluid of 105 ⁰C is passed over the sphere of outer radius 5cm and inner radius 1cm. The temperature of the outer surface is the same as that of hot fluid while the temperature of the inner surface is 35 ⁰C. Assume the sphere is made up of aluminum having a thermal conductivity of 40W/m.K. Find the heat rate and thermal resistance for this case.

Q.6 A concentric tube heat exchanger with an area of 50 m2 operating under the following conditions:

Description Heat Capacity rate,
C= m*Cp (kW/K) Inlet temperature
Ti (C) Outlet temperature
To (C)
Hot Fluid 6 70 ??
Cold Fluid 3 30 60

Calculate the outlet temperature of the hot fluid.

Q.7 Discuss log mean temperature difference. Draw temperature profile diagram for counter-current heat
exchanger.

Q.8 Define and explain
i View Factor
b) Nucleate boiling

## Guess Paper 3: Chemical Process Heat Transfer Spring – 2019 Past Papers

University Name – Confidential

Time Allowed: 3 hours

Total Marks:    70, Passing Marks (35)

Q1: Choose the correct options. Each correct option carries 1 mark.
1) Unit of thermal conductivity is ……..
(a)Kcal/hr.m2.oC (b) kcal/hr.m.oC (c) Kcal/hr.m (d) Kcal/hr.oC
2) When warm and cold liquids are mixed, the heat transfer is mainly by
(a) Conduction (b) convection (c) Radiation (d) both (a) & (c)
3) Heat transfer in liquids and gases takes place by
(a) Conduction (b) Convection (c) Radiation (d) Conduction and convection
4) Thermal conductivity of solid metals with the rise in temperature normally
(a) increases (b) decreases (c) remains constant ( d) may increase or decrease depending on temperature (e) unpredictable.
5) Pick up the wrong case. Heat flowing from one side to other depends directly on
(a) Face area (b) time (c) thickness (d) temperature difference
(e) thermal conductivity.
6) The temperature of steam at around 540°C can be measured by
(a) Thermometer (b) radiation pyrometer (c) thermistor (d) thermocouple
(e) Thermopile.
7) A non-dimensional number generally associated with natural convection heat transfer is (a) Grashoff number (b) Nusselt number (c) Weber number (d) Prandtl number
(e) Reynold number.
8) Which of the following has the least value of conductivity?
(a) Glass (b) water (c) plastic (d) Rubber (e) air
9) Fourier’s law of heat conduction is valid for
(a) one dimensional case only (b) two-dimensional cases only (c) three-dimensional cases only (d) regular surfaces having non-uniform temperature gradients (e) irregular surfaces.
10) Heat is closely related with.
(a) Liquids (b) energy (c) Temperature (d) entropy (e) Enthalpy
11) The thermal diffusivities for gases are generally
(a) more than those for liquids (b) less than those for liquids (c) more than those for solids
(d) Dependent on the viscosity (e) Same as for the liquids.
12) The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as
(a) Kirchoff’s law (b) Stefan’s law (c) Wien’ law (d) Planck’s law
13) If the temperature of a solid surface changes form 27°C to 627°C, then its emissive power changes in the ratio of
(a) 3 (b) 6 (c) 9 (d) 27 (e) 81.
14) Convective heat transfer, in which heat is transferred by movement of warmed matter, is described by
(a) Fourier’s law (b)Newton’s law of cooling (c)Fick’s law (d) None of these

Q2: Explain steady-state one-dimensional heat conduction for a plain wall.

Q3: Discuss the term “Critical thickness of insulation”.

Q4: An exterior wall of a house may be approximated by a 4-in layer of common brick [k = 0.7W/m•◦C] followed by a 1.5-in layer of gypsum plaster [k =0.48 W/m•C]. What thickness of loosely packed rock- wool insulation [k =0.065 W/m•◦C] should be added to reduce the heat loss (or gain) through the wall by 80 percent?

Q5: What are the different types of heat exchangers?

Q6: What advantage does the effectiveness-NTU method have over the LMTD method?

Q7: Discuss the overall heat transfer coefficient for cylindrical bodies.

Q8: Write short notes on any two of the following.
a) Log Mean Temperature Difference (LMTD)
b) Black Body
c) Shell and Tube Heat exchanger