ICAR AIEEA-PG / PGS — Code 18 Food Science Technology · India · ICAR through the National Testing Agency
Original practice questions written to the published syllabus · not past papersMass and energy balances and the three transfer processes — momentum, heat and mass — applied to foods: pumping viscous products, heating cans and pouches, and moisture and gas movement through foods and packaging films.
In the exams: GATE XE-G Section 4 (mass and energy balance, momentum transfer, heat transfer, mass transfer); ICAR AIEEA-PG Code 18 Unit II
ICAR AIEEA-PG / PGS — Code 18 Food Science Technology
Unit II names system analysis, mass and energy balance, heat and mass transfer, heat exchanging, steam generation and process equipment design. MCQs test definitions (Re, Nu, Bi, Fo), flow regimes, heat-exchanger types, steam quality and short calculations.
How our questions for ICAR AIEEA-PG / PGS spread across the units of Transport Phenomena in Food Processing: Fluid Flow, Heat & Mass Transfer. Difficulty: 25 easy, 25 medium, 6 hard.
| Units, dimensions and dimensional analysis | 5 | |
| Material balances on mixing, concentration and drying | 5 | |
| Pumps for foods: centrifugal and positive-displacement | 5 | |
| Energy balances and steam tables | 4 | |
| Flow in pipes: Reynolds number, friction factor and pressure drop for Newtonian fluids | 4 | |
| Steady-state conduction through slabs, cylinders and composite walls | 4 | |
| Convection: film coefficients and dimensionless numbers | 4 | |
| Radiation heat transfer | 4 | |
| Permeability through single and multilayer films | 4 | |
| Fluid statics and the Bernoulli equation | 3 | |
| Flow of non-Newtonian foods in pipes | 3 | |
| Unsteady-state heat transfer: lumped systems and Heisler charts | 3 | |
| Heat exchangers: plate, tubular and scraped-surface; LMTD and effectiveness | 3 | |
| Molecular diffusion and Fick's law | 3 | |
| Convective mass transfer | 2 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
The SI unit of dynamic viscosity is
A. Pa s
Viscosity is shear stress (Pa) divided by shear rate (1/s), giving Pa s. m²/s is kinematic viscosity (or diffusivity); N/m is surface tension; kg/m³ is density.
Further reading: Geankoplis, Transport Processes and Separation Process Principles
5,000 kg/h of milk at 12 % total solids is concentrated to 45 % total solids. The water evaporated is closest to
D. 3,667 kg/h
W = F(1 − xF/xP) = 5,000 × (1 − 12/45) = 3,667 kg/h. 1,333 kg/h is the concentrate; 1,650 kg/h multiplies by 0.33 (45 − 12 as a fraction); 3,350 kg/h subtracts percentages (5,000 × 0.67).
Further reading: Singh and Heldman, Introduction to Food Engineering
Steam is the preferred heating medium in food plants mainly because it
B. releases a large latent heat at a constant, pressure-controlled temperature
Condensing steam delivers about 2,200 kJ/kg at a temperature fixed by its pressure, with very high film coefficients; condensate must be removed by traps.
Further reading: Singh and Heldman, Introduction to Food Engineering
The Bernoulli equation for an ideal fluid states that along a streamline the sum of
B. pressure, kinetic and potential energy per unit mass is constant
P/ρ + v²/2 + gz = constant for frictionless, incompressible, steady flow; real flows add pump work and friction terms.
Further reading: Geankoplis, Transport Processes and Separation Process Principles
Milk (ρ = 1,030 kg/m³, μ = 2.0 mPa s) flows at 1.5 m/s in a 38 mm tube. The Reynolds number is closest to
A. 29,355
Re = ρvD/μ = 1,030 × 1.5 × 0.038/0.002 = 29,355, turbulent. 29 and 29,355,000 come from unit slips in μ (Pa s vs mPa s); 2,936 uses D = 3.8 mm.
Further reading: Singh and Heldman, Introduction to Food Engineering
In a heat exchanger with a thin stainless-steel wall, the wall usually contributes little to the overall resistance because
A. metal conductivity is high compared with the fluid films
A 1–2 mm steel wall has resistance far below the convective films and fouling layers.
Further reading: Incropera and DeWitt, Fundamentals of Heat and Mass Transfer
Natural (free) convection is driven by
C. density differences caused by temperature differences
Warm fluid is less dense and rises; forced convection uses pumps or fans. The Grashof number characterises it.
Further reading: Incropera and DeWitt, Fundamentals of Heat and Mass Transfer
A food surface at 20 °C (ε = 0.9) is in an oven whose walls are at 200 °C. The net radiant heat flux to the food is closest to
B. 2,178 W/m²
q = εσ(T1⁴ − T2⁴) = 0.9 × 5.67 × 10⁻⁸ × (473⁴ − 293⁴) = 2,178 W/m². 82 W/m² uses Celsius temperatures; 54 W/m² raises the difference to the fourth power; 2,420 W/m² omits ε.
Further reading: Incropera and DeWitt, Fundamentals of Heat and Mass Transfer
Water evaporates from a 0.5 m² wet surface with km = 0.02 m/s; vapour concentrations are 0.017 kg/m³ at the surface and 0.008 kg/m³ in the air. The evaporation rate is
D. 0.09 g/s
N = kmA(Cs − C∞) = 0.02 × 0.5 × 0.009 = 9.00e-05 kg/s = 0.09 g/s. 0.17 g/s uses Cs only; 0.08 g/s uses C∞ only; 9.0 g/s is a unit slip.
Further reading: Geankoplis, Transport Processes and Separation Process Principles
In the solution–diffusion model of gas permeation through polymers, the permeability coefficient equals
C. diffusivity × solubility
P = D × S; flux = PΔp/L.
Further reading: Robertson, Food Packaging: Principles and Practice
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