Download GTU BE/B.Tech 2019 Winter 3rd Sem New 3131404 Food Engineering Thermodynamics Question Paper

FirstRanker.com

Subject Code: 3131404

GUJARAT TECHNOLOGICAL UNIVERSITY

--- Content provided by FirstRanker.com ---

- SEMESTER- IIT (New) EXAMINATION — WINTER 2019

Subject Name: Food Engineering Thermodynamics

Time: 02:30 PM TO 05:00 PM

Date: 26/11/2019

Total Marks: 70

--- Content provided by⁠ FirstRanker.com ---

Instructions:

1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. Standard Steam Tables and normal range Psychrometric Chart can be used

--- Content provided by FirstRanker.com ---

Q.1

1. (a) Define ideal and real gases. Why do real gases deviate from ideal behaviour? 03
2. (b) A sealed container contains air at 87 °C and 1 bar. The container was evacuated using a vacuum pump so that the vacuum inside the container is recorded as 18 kPa. Calculate the final temperature & absolute pressure inside the container. 04
3. (c) Write down Van der Waal’s equation of state for real gases. Two hundred moles of CO2 gas is stored in a 2 liter closed container at — 13 °C. Calculate the pressure of the gas in kPa using Van der Waal’s gas equation. Take a = 0.360Pa (m6/mole)², b = 4.28 x 10?5 m³/mole, R = 8.314 J/mole K 07

Q.2

--- Content provided by‍ FirstRanker.com ---

1. (a) Match Column-I with most appropriate entity from Column-II and reconstruct a matched table. 03

   Column-I	Column-II
   Vacuum of 380 mm Hg equals	(i) Van der Waal’s gas equation
   Ideal gases	(ii) Cp=Cv is >0
   Real gases	(iii) NkT
   Specific gas constant for O2 gas	(iv) 14 g
   	(V).77°F
   	(vi)56g
   	(vii) RT
   For ideal gases PV is equal to :	(viii) < 0 for real gases
   Mass of 2 mole N2 gas at NTP is	(ix) Sublimation
   25 °C is equal to	(x) 14.67kPa
   Freeze drying	(xi) 259.8 J/kg K

2. (b) Explain Zeroth law of thermodynamics. List different types of thermometers. 04
3. (c) A gas at 5 bar and 177 °C kept in a container of 200 liter volume. It is cooled isobarically to 27 °C. Calculate the following in kJ:
   1. Heat transferred.
   2. Change in internal energy.
   [Take Cp =40 J/mol K, R = 8.314 J/mol k] 07

--- Content provided by‌ FirstRanker.com ---

OR

1. (a) Derive SFEE for a fluid stream entering and leaving a thermodynamic system in terms of work and energy transfer per unit mass. Specify the assumptions made. 07

OR

1. (b) Explain how first law of thermodynamics can be applied for closed systems operating in a cyclic and non-cyclic process. Prove that “TV^?-1 = constant” for an ideal gas undergoing a reversible process. 07

FirstRanker.com

--- Content provided by​ FirstRanker.com ---

Q.3

1. (a) Show the following processes on psychrometric chart for moist air: 03
   1. Sensible heating
   2. Dehumidification
   3. Humidification

--- Content provided by‍ FirstRanker.com ---

2. (b) Atmospheric air for Anand city on a certain day in October records the following:
   Temperature = 32 °C
   Barometric Pressure = 760 mm Hg
   WBT =27°C
   Using Psychrometric Chart determine: 04
   1. DPT in °C

   --- Content provided by‍ FirstRanker.com ---

   2. % RH
   3. DBT in °C
   4. Specific humidity in kg/kg d.a
3. (c) Draw a labeled ‘P-V diagram’ of pure water showing zones of thermodynamic interest. Determine the following using Steam Tables for saturated steam at 10 bar pressure: 07
   1. Saturation temperature in Kelvin

   --- Content provided by FirstRanker.com ---

   2. Specific Entropy in kJ/kg K
   3. Latent heat of vaporization in kJ/kg
   4. Enthalpy of saturated vapours in kJ/kg.

OR

--- Content provided by⁠ FirstRanker.com ---

1. (a) Indicate the following processes on psychrometric chart for moist air: 03
   1. Sensible cooling
   2. Dehumidification and heating
   3. Cooling and dehumidification
2. (b) Atmospheric air on a certain day has the following parameters:
   

   --- Content provided by‍ FirstRanker.com ---

   Temperature = 40 °C
   Barometric Pressure = 760 mm Hg
   Relative humidity = 80%.
   Using Psychrometric Chart determine: 04
   1. DPT in °C
   2. WBT in °C

   --- Content provided by FirstRanker.com ---

   3. Absolute humidity in kg/kg d.a
   4. Enthalpy in kJ/kgd.a
3. (c) Show state points of water on a “T-S phase diagram”. Explain sub-cooling, superheating, critical point & triple point of water. Using Steam Tables, for saturated steam at 180 °C, determine 07
   1. Saturation pressure in bar
   2. Specific Entropy in kJ/kg K

   --- Content provided by‌ FirstRanker.com ---

   3. Enthalpy of saturated vapours in kJ/kg.

Q.4

1. (a) Prove that for any thermodynamically feasible cyclic process § dQ/T < 0 03
2. (b) What is Joule-Kelvin effect? Show that for ideal gases, µ_j =0 04

--- Content provided by​ FirstRanker.com ---

3. (c) State first law of thermodynamics for a closed system undergoing a state change process. An ideal gas is allowed to expand isothermally in a reversible manner. Establish that the work done per mole of gas is given by W=nRTln(V2/V1) 07

OR

1. (a) Differentiate between intensive and extensive properties with examples. Define Specific heat at constant pressure C_p and Specific heat at constant volume C_v for ideal gases. 03
2. (b) An insulated rigid tank of 0.2 m³ volume contains 25 kg of nitrogen gas at 4 bar pressure. A paddle wheel is rotated inside the tank so that its pressure increases to 5 bar. Calculate the following: 04
   1. Net heat transfer
   2. Change in internal energy

   --- Content provided by‌ FirstRanker.com ---

   3. Work done
   4. Entropy change.
   [Take Cp = 1.04 kJ/kgK, R = 8.314 J/mol K]
3. (c) Differentiate between steady and non-steady flow processes with examples. Write down SFEE for a fluid stream entering and exiting a turbine. For a steady flow of steam through a turbine the following data are available: 07
   

   	Inlet Condition	Outlet Condition
   P	P1 = 50 bar	P2 = 38 bar
   t	t1 = 500 °C	t2 = 470 °C
   h	h1 = 3600 kJ/kg	h2 = 3500 kJ/kg
   v	v1 = 0.072 m³/kg	v2 = 0.082 m³/kg

   
   

   --- Content provided by‍ FirstRanker.com ---

   A heat loss of 12kJ/kg occurs through the turbine due to poor insulation. Calculate the inlet and outlet velocities of steam. Assume that inlet and outlet cross-sectional areas and elevations are same.

Q.5

1. (a) What is Gibb’s phase rule? Calculate the degrees of freedom of liquid water at 25 °C and 1 atmosphere pressure and at its critical point. 03
2. (b) Prove the following for a pure substance undergoing an infinitesimally reversible process: 04
   1. dU=TdS-PdV
   2. dH=TdS + VdP

   --- Content provided by‍ FirstRanker.com ---

   3. dA = - (PdV +sdT)
   4. dG = VdP —sdT
3. (c) State second law of thermodynamics. Draw a block diagram of a heat engine indicating work-energy flow directions and write energy balance equations. How will you express its Carnot and actual thermal efficiency? A heat engine operating on Carnot cycle, produces 200 kW of power while operating between temperature limits of 750°C and 50°C. Determine the engine efficiency and the amount of heat input to the engine. 07

OR

--- Content provided by‌ FirstRanker.com ---

1. (a) Explain types of thermodynamic equilibrium for a system and conditions for its stability. 03
2. (b) State Kelvin-Plank statement of second law of thermodynamics and explain the equivalence of Kelvin —Planck and Clausius statements with neat diagram. 07
3. (c) Using first principles, prove that (?T/?V)_S = —(?P/?S)_V 04

FirstRanker.com

--- Content provided by FirstRanker.com ---