Download GTU BE/B.Tech 2018 Winter 3rd Sem Old 131404 Food Engineering Thermodynamics Question Paper

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GUJARAT TECHNOLOGICAL UNIVERSITY

BE - SEMESTER-III (OLD) EXAMINATION — WINTER 2018

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Subject Code: 131404 Date: 05/12/2018

Subject Name: Food Engineering Thermodynamics

Time: 10:30 AM TO 01:00 PM Total Marks: 70

Instructions:

1. Attempt all questions.

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

Q1 (a) What are ideal gases? In what way real gases differ from ideal behaviour? 07

(b) A container of 0.5 m³ contains nitrogen gas at 5 atmosphere pressure and 17 °C. Calculate the mass of gas in kg. Assume ideal gas behaviour. [Take R = 8.314 J/mol K] 07

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Q2 (a) State the law of corresponding states. Hundred kilogram of CO₂ gas is stored in a 10 liter sealed container at 2 °C. Calculate the pressure of the gas in kPa using compressibility factor of z = 0.82. [Take M =44 and R = 8.314 J/mole K] 07

(b) State Zeroth law of thermodynamics. Convert 77 °F in °C and Kelvin. Explain with a neat diagram the principle and working of any one thermometer. 07

OR

(b) Explain Joule-Kelvin effect. Prove that for an ideal gas undergoing a throttling process, µ = 0 07

Q3 (a) Define enthalpy. Prove that C_p-C_v =R for ideal gases. 07

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(b) Five moles of SO₂ gas at 300K is heated reversibly at a constant pressure of 2 bar until its volume doubles. Calculate (i) The work done. (ii) Change in internal energy and enthalpy. [Assume ideal behaviour; C_v =32 J/mol K, R = 8.314 J/mol k] 07

Q3 (a) Explain first law of thermodynamics for a closed system operating in a cycle. Prove that the work done by the system during an isentropic process is given by : (P₁V₁ - P₂V₂). 07

(b) What is SFEE? A steam turbine developing 600 kW receives a flow of 25 tonne/h of steam @ 110 m/s. The exit velocity of steam is 325 m/s. The inlet pipe is located 1.5 m above the outlet pipe. Using SFEE, calculate the change in enthalpy. 07

OR

What is first law of thermodynamics? Prove that for a reversible adiabatic process TV^?-1 = Constant. 07

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Q4 (a) What is Gibb’s phase rule? Explain different types of thermodynamic equilibrium. Calculate the thermodynamic degrees of freedom of pure water at its critical point. 07

(b) Prove that ?(dQ/T) < 0 for any irreversible cyclic process. 07

OR

Explain Carnot theorems. A Carnot heat engine operates between a source temperature of 620 °C and a sink temperature of 37 °C. The work output is 20 kW. Calculate the amount of heat rejected to sink. 07

Q5 (a) Explain the operation of a heat pump with help of a schematic diagram. A heat pump is operating between 5 °C and 30 °C at a COP of 50 % of the maximum possible COP. If the net heating effect generated is 5 kW, calculate the power requirement. 07

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(b) Explain Kelvin-Plank statement of second law of thermodynamics with the help of a neat schematic diagram. Show that for any reversible thermodynamic process: (dQ/T)_rev = (dS) 07

Q5 (a) Draw a neat labeled P-v diagram of a pure substance (water) showing its various states. Show that the specific volume of wet steam is given by, v=v_g+(1-X) v_fg 07

(b) Determine the following using steam tables for saturated steam at 5 bar pressure: (i) Saturation temperature in °C (ii) Entropy in kJ/kg K (iii) Latent heat of vaporization in kJ/kg (iv) Specific volume in m³/kg 07

OR

Explain phase diagram of a pure substance (Water) on a T-s diagram. Using Steam Tables determine the following for saturated steam at 150 °C: (i) Specific enthalpy (ii) Latent heat of vaporization (h_fg) (iii) Density (iv) Specific entropy 07

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Explain the following processes on a Psychrometric Chart: (i) Sensible heating (ii) Cooling and Dehumidification. 07

The following data are available for the atmospheric air: Temperature = 40 °C, Atmospheric Pressure = 760 mm Hg and RH = 80%. Using Psychrometric Chart determine the following: (i) Mass of air in kg. (ii) DPT in °C (iii) WBT in °C (iv) Enthalpy (v) Specific volume 07

Explain the Following IRAFRUPTHERH K Com i. Dry bulb temperature ii. Wet bulb and temperature iii. Adiabatic saturation temperature 07

Air at a certain location having a barometric pressure of 760 mm Hg, air is at DBT and WBT of 35 °C and 26 °C respectively. Determine the following using Psychrometric Chart: (i) Absolute humidity (ii) Relative humidity (iii) Relative humidity (iv) Dew point temperature 07

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